33-05-003 Piston Engine Emissions_Swiss FOCA_Summary Report_070612_rit Federal Department of the Environment, Transport, Energy and Communications DETEC

Federal Office of Civil Aviation FOCA Aviation Policy and Strategy Environmental Affairs



# AIRCRAFT PISTON ENGINE EMISSIONS



# SUMMARY REPORT

Purpose of this paper: This paper aims to inform interested parties about the development of aircraft piston engine emission factors. These have been meas ured and are provided by Swiss FOCA for the primary purpose of emission inventory calculations. Furthermore, FOCA presents findings about emissions performance and in-flight oper ation of aircraft piston engines and recommendations for emissions reduction.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern FOCA, CH-3003 Bern

Reference: 0 / 3/33/33-05-003 ECERT Contact person: Theo Rindlisbacher Tel. +41 31 325 93 76, Fax +41 31 325 92 12, theo.rindlisbacher@bazl.admin.ch This document has been released for publication by FOCA, Aviation Policy and Strategy, Director M. Zuckschwerdt, 13.06.2007Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern ABSTRACT
According to Swiss aviation law (SR 748.0, LFG Art. 58), emissions from all engine powered aircraft have to be evaluated and tested. The legal requirem ent also incorporates aircraft engines that are currently unregulated and do not have an ICAO 1 emissions certification – lik e piston, helicopter, turboprop and small jet engines. Credible emissions dat a are necessary for emission and immission inventory purposes, environmental impact assessments an d for issues directly related to environmental protection.
Up to now, there have only been few emissions data available for aircraft piston engines. This report tries to fill this gap of knowledge in a comprehensive approach. The following aspects are documented in this report and in its Appendices:

• Emissions performance for a wide range of existing aircraft piston engines.

• A methodology for cost effective standardized on ground emission measurements of aircraft piston engines.

• A methodology for the calculation of aircraft piston engine emissions.

• General principles of aircraft piston engine combustion and the effect of pilot operations on emissions.

• Research for emission reduction through optim ization of pilot operations, new aircraft piston engine concepts, technological improvements and the use of cleaner AVGAS.
The presented material serves FOCA for

• Calculation of more complete aviation emission inventories in the context of legal national and international environmental requirements.

• Observation of the environmental impact of piston engine aircraft.

• Reduction of piston engine aircraft emissions.

• Pilot education.

As far as measurements are concerned, FOCA plans to increase the number of measured engines in the future. For other engine families without an ICAO emissions certification, like helicopter turbines and small jet engines, there is still a lack of emis sions data and FOCA plans to work on respective packages, based on its aviation law.

June, 2007 Theo Rindlisbacher

1 International Civil Aviation OrganizationReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 

### CONTENTS Page



### 1. General information 9

1.1 Background 9 1.2 Main scope and objectives of the project 10



### 2. Summary of results 11

2.1 FOCA data sheets and their practical application 11

2.1.1 General methodology for emissions calculation 11 2.1.2 Suggested times in mode for emissions calculation 11
2.1.3 Cruise emissions factors 12
2.1.4 Calculated LTO and 1 hour cruise emissions on data sheets 12 2.1.5 Data quality and accuracy 13
2.1.6 Data download 14


### 2.2 General findings about aircra ft piston engine emissions 15

2.2.1 Combustion basics 15 a) What goes in? Composition of AVGAS 100LL 15 b) How much air to make the fire? 16 c) What comes out? 17 d) Properties of pollutants 17

2.2.2 Air/fuel mixture adjustments 18 a) Dominant “old tech” engines require manual mixture control 18 b) Rich and lean mixture definition with lambda 19 c) Mixer = lambda control 20 d) Typical values for lambda 20 e) Influence of mixer settings on engine temperatures and power 21 f) Influence of mixer settings on emissions 22 g) Influence of mixer settings summary 24 h) Why “full rich” at high power for “old tech” engines? 24 i) Why “rich” near idle power? 25 j) Uneven distribution of mixture and temperature in “old tech” engines 25 k) Investigated manual mixture setting procedures 28 l) Mixture adjustment technique with fuel flow 29

2.2.3 Typical emission factors and ma gnitude of emissions 30 a) Pollutants of “old tech” engines during l anding and take-off cycle (“full rich” mixture) 30 b) Pollutants during cruise (at or near “peak EGT”) 33 c) Emissions for aerodrome circuits (“old tech” engines) 34 d) Emissions for landing and take-off cycle 35 e) Emissions for cruise 36Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern f) Emissions of modern turbo diesel engines – a comparison 36 g) Contribution of piston engines to total aviation emissions 38


### 2.3 Optimization of fuel bur n and emissions 38

2.3.1 “Old tech” gasoline engines 38 a) Use of unleaded AVGAS 38 b) Power setting, choice of speed and altitude for lowest possible CO 2 emissions in cruis e 38 c) Manual mixture management (Climb, Cruise, Descent/Approach) 43

2.3.2 Choice of engine technology 44 a) FADEC for gasoline engines 44 b) Turbo Diesel engines 44


### 3. Outlook – planned future work 45
3.1 Number of measured aircraft piston engines 45 3.1.1 “Old tech” engines and new engines concepts 45 3.1.2 Modernized “old tech” engines with FADEC 45



### 3.2 Unleaded AVGAS 45
3.2 Emissions data for helicopter turbines and small turbofans 46

3.3 International activities 46
4. List of acronyms and abbreviations 47
5. Bibliography 49
Appendix 1: Measurement System

a) Minimum requirements met by FOCA lo w cost gas measurement system 3 b) Measurement Method 3 c) Measured Gaseous Emissions 3 d) Ranges 3 e) Illustration of FOCA low cost gas measurement system 4 f) Measurement systems for total HC measurements (certification standard) 5 g) Measurement systems for comparative gas measurements (certification standard) 5 h) Measurement system for nanoparticle measurements (Appendix 4) 6



### Appendix 2: Documentation of in-flight Measurements

1. The first in-flight tests 3 1.a) Preparation of aircraft HBEYS 3 1.b) Calculated emission factors for first test flight with HBEYS 5 1.c) Discussion and general explanations 6 2) Standard Flight Test Programme 7Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 3) HBEYS (Carburated Engine Lyc O-360 Series) 8 3.a) Results for simulated aerodrome circuits 8 3.b) Discussion 11 3.c) HC emission factors at flight idle 12 3.d) Discussion 13 3.e) Additional high altitude circuit flight testing 14 3.f) Discussion 15 3.g) Inventory: Total emissions in aerodrome circuits at different flight altitudes 15 3.h) Full power and approach power settings 16 3.i) Climb power and approach power settings 18 3.j) Cruise power settings 20
4) HBKEZ (Fuel Injected Engine Lyc IO-360 Series) 22 4.a) Results for simulated aerodrome circuits 25 4.b) Discussion 27 4.c) Full power and approach power settings 27 4.d) Take-off, climb and approach power setti ngs with mixture “full rich” 29 4.e) Discussion 30 4.f) Take-off, climb and approach power settings with mixture adjustment 31 4.g) Discussion 33 4.h) Inventory: Standard flight em ission measurement 33
5) HBKIA (Fuel Injected Engine TCM IO-550 B) 36 5.a) Results for aerodrome circuits 39 5.b) Discussion 43 5.c) Inventory: Total emissions of HBKIA in aerodrome circuits 43 5.d) Discussion 44 5.e) Additional high altitude circuit flight testing 44 5.f) Discussion 46 5.g) Inventory: Total emissions of HBKIA in t he low and high altitude aerodrome circuit 47 5.h) Discussion 47 5.i) Full power settings 47 5.j) Discussion 50 5.k) Climb power settings 50 5.l) Approach power settings 53 5.m) Standard flight profile emission measurement 55 5.n) Discussion 57 5.o) Inventory: Total emissions of HBKIA in standard flight, defined in 5.m) 59 5.p) Emissions summary for a HBKIA mission, defined in 5.m) 64
6) HBHFX (Carburated Engine Lyc O-320 Series) 64 6.a) HBHFX high accuracy in-flight measurements: Installation of OBS2200 64 6.b) Real time emission mass determination during flight 70 6.c) OBS2200 confirms typical emission factors for Lycoming carbureted engines 75Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 6.d) OBS2200 time trend chart and confirmation of high HC at flight idle 76


### Appendix 3: Ground Measure ment Power Settings
1. The problem of piston engine power definitions 3 2. Theoretical power calculation 3 3. Engine manifold pressure (MAP) and RPM for power determination 3 4. Correlation of fuel flow and propeller power 4 5. Adjustment of ground measurement power settings (Fuel Flow Method) 7 5.1 Step 1: Comparison of in-flight and static ground measurements of HBKEZ (example) 7 5.2 Step 2: Power setting methodology fo r static ground measurements 8
5.2.1 Determination of maximum fuel flow 8 5.2.2 Power settings other than maximum propeller power 9 5.3 Step 3: Application of the power setting methodology (step 2) 9 5.3.1 Comparison of ground and late r in-flight measurements 11 5.3.2 Adjustments to the fuel flow method for complex aircraft/engines 14 5.3.3 Temperature corrections for normally aspirated carburetted piston engines 15 6. Recommended ground measurement power setting procedures for emission tests 17 6.1 Selection of methodology 17
6.2 Procedure for determination of maximum fuel flow 17
6.2.1 Fuel flow calibration 17 6.2.2 Preparing the aircraft for a maximum fuel flow (and emission) measurement 18 6.3 Simple fuel flow method 19
6.3.1 Fuel flow for all modes 19 6.3.2 Recommended procedure 20
6.4 Combined MAP & fuel flow method 21 6.4.1 Preparations 21 6.4.2 Recommended procedure 22 7. Example for measurement documentation 23



### Appendix 4: Nanoparticle Measurements

1. Background, motivation and project partners 3 1.1 Research programme 3 1.2 Research goals 3

2. General results for nanoparticle emissions of an aircraft gasoline engine, running 3 under rich air/fuel conditions (AVGAS 100 LL) 2.1 Preparations 3 2.2 SMPSTM system layout and descripti on for particle measurements 4
2.3 Results 6
2.4 Picture documentation of first non-vo latile nanoparticle measurements 9Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 3. Looking for particle emission improvem ents: First tests with unleaded 11 AVGAS (AVGAS 91/96 UL) 3. 1 Introduction and description of AVGAS 91/96 UL 11 3.2 Composition of measured AVGAS 100LL (560 mg Pb / liter) 11
3.3 Used aircraft 12
3.4 Results for HB-EYS 12
3.5 Conclusion for HB-EYS tests 13
3.6 Results for SE-KEI 13
3.7 Air/fuel mixture ratio for HB-EYS and SE-KEI 14
3.8 Discussion 15
3.9 Conclusions for AVGAS 91/96 UL 15

4. Change from SMPSTM to Engine Exhaust Particle SizerTM (EEPS 3090TM) system for 15 aircraft piston engine nanoparticle measurements
4.1 Introduction 15 4.2 EEPSTM system description 15 4.3 Application of EEPSTM for aircraft piston engine measurements 16
4.4 EEPSTM results 18
4.5 First conclusions for EEPSTM measurements 19

5. Research for AVGAS 100LL substitution and emission reduction 19
5.1 Test fuels 20
5.2 Test location 20
5.3 Used aircraft 20 5.4 Measurement systems 20 5.5. Power settings 21
5.6 Results 22
5.7 Discussion 31
5.8 First conclusions 32



### Appendix 5: Calculati on of Emission Factors

a) Introduction 3 b) List of abbreviations 3 c) Calculation of EF (Equations used for FO CA ground measurements and data sheets) 3 d) Equations for "low cost" measurement system described in Appendix 1 for AVGAS 4 (used for FOCA in-flight measur ements and comparative ground measurements) e) Equations for "low cost" measurement sy stem described in Appendix 1 for DIESEL 6 f) Correction of ambient air temperature influen ce on normally aspirated piston engines 7 g) Statistical checks 7 h) Fuel flow 7Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 

## 1. General information

1.1 Background

There are basically three propul sion concepts used for today’s engine powered civil aircraft:

• Propulsion with „Turbofan“ (In everyday langu age, this is usually called “jet engine”),

• Propulsion with „Turboprop“ (Turbojet engine, driving a propeller) and

• Propulsion with piston engines (driving a propeller).

Turbofans (jet engines) and turboprops burn jet fuel (kerosene), aircraft piston engines primarily burn aviation gasoline (AVGAS). The highest portion of aviati on fuel is consumed by large aircraft with large engines (mostly turbofans). Large turbofans and jet engines are certified for compliance with tight emissions standards.

Aircraft piston engines are mostly used for what mi ght be called “small propeller aircraft”. On a global scale, such aircraft consume a relatively minor shar e of fuel. In Switzerland, the annual fuel consumption of aircraft piston engines is less than the fuel consumption for gardening activities 2 . Basically, emissions from aircraft piston engines have not been se en as a significant problem when looking at the broad picture of total emissions, and when look ing at measured pollutant concentrations in a country like Switzerland. This can vary when looking at t he aviation sector only, as we will see later (section 2.2.3 of this report). But assuming little to no infl uence, emissions from aircraft piston engines have not raised any interest, so far. Internationally, there have not been any efforts to consider work towards an emission certification for such engines. The dis advantage is that information about aircraft piston engine emissions performance is practically nonexistent . In Switzerland, this has sometimes caused problems, e.g. to produce a complete aircraft emissi ons inventory, or to provide credible data for an environmental impact assessment.

According to Swiss aviation law (SR 748.0, LFG Art. 58), emissions from all engine powered aircraft have to be evaluated and tested. Therefore, the Swis s Federal Office of Civil Aviation (FOCA) has been looking for efficient means, to fill the ”black emission holes“.

In autumn 2002, FOCA initiated project ECERT (E mission Certification). Although the project name incorporates the term “certification” it was clea r from the beginning that the primary purpose of the project was to provide emission factors. This proj ect would present the best available emissions data for aircraft piston engines but not necessarily at certif ication level, because of cost efficiency considerations. Project planning started with estimations of the aircra ft piston engine emissions contribution to the total civil aviation emissions. First estimations were based on a handful of old data and generated a surprising result: Carbon monoxide (CO) and total hydrocarbon (HC) emissions could be significant in a landing and take-off cycle, compared to large aircra ft. Despite a fuel burn that was severa l magnitudes lower, CO and HC emissions coul d reach the magnitude of large ai rcraft. Explanations were found: The combustion in engines used for today’s passenger aircraft has become exceptionally complete and clean, whereas aircraft piston engine technology – in general – has had a complete technology standstill since the 60’s. Emissions reducti on has never been an issue. Reliability of simple piston engine concepts, high power-to-weight ratio (high HP per kg), and production costs for a comparatively low number of certified engines seemed to be t he main drivers. A disadvantage of such concepts was high specific emissions. Additionally, about half of the global aircraft piston engine fleet must operate on leaded fuel, due to high octane requirements. It became clear to FOCA that it would be worth ga thering a clear picture of aircraft piston engine emissions, and that new piston engine concepts would bear a high potential of emissions reduction within the aviation sector.

2 Swiss National Greenhouse Gas Inventory, Off Road Sector, INFRAS, January 2004.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern From the beginning, the project was driven by the sear ch for cost effective solutions. On the one hand, FOCA bought “low cost” equipment, which costs about 1/10 of a conventional certification level test equipment. This equipment was originally designed for automotive engine emissions testing (Appendix 1). For the purpose of emission factor determinat ion, several adaptations and further developments were needed (Appendix 5). On the other hand, most ai rcraft used for in-flight testing belong to the Swiss Confederation, with FOCA being the respon sible operator having direct access to the fleet. (Robin DR400/180 HB-EYS, Robin DR400/500 HB -KEY and HB-KEZ, Raytheon A36 Bonanza HBKIA). In order to measure aircraft piston engine emission s in static conditions, directly on the ground, an appropriate ground measurement methodology had to be developed (Appendix 3). A special feature which most gasoline aircraft piston engines have in common is the manual air/fuel mixture control. Knowledge, necessary for standardization of the me asurements could only be gained from in-flight emission tests (Appendix 2). These measurements were also leading to an improved insight in emissions optimized operations of manually tuned engines. Wi th growing interest in fine particle emissions, particle measurements have been integrated into the proj ect. Finally, after the first results for particles, FOCA intensified basic research into emissions reduction of AVGAS engines (Appendix 4).

Since 2003, and through AERONET, there has been collaboration with the German Aerospace Centre (DLR), HJELMCO Oil Inc., BR P-ROTAX GmbH & Co, HORIBA Europe GmbH, TSI GmbH, ALPAIR, Swiss AIR FORCE, Prospective Concepts AG und GABUS SA.



### 1.2 Main scope and object ives of the project

- Development of a cost-effective ground based in-field measurement technique for aircraft piston engines (gaseous and non-volatile particle em issions) by using state of the art automotive testing equipment and by comparing in-flight to ground measurements.
- Gather absolute emissions data of a variety of piston engines for emissions inventory purposes (some helicopter – and small jet engines will follow at a later step).
- Development of operational guidelines for piston engines with manual mixture control which take engine durability and emission performance into account.
- If feasible, use the basic research for the dev elopment of an emission certification for small engines, bearing in mind that certif ication costs should be reasonable.
- Support basic research in order to replac e leaded by unleaded AVGAS for aviation piston engines and to improve emissions performance.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 

## 2. Summary of results

2.1 FOCA data sheets and th eir practical application
2.1.1 General Methodology for Emission Calculation
Definition of Power Modes for Aircraft Piston Engines
Typical power settings have been established by fli ght testing (Appendix 2) and ground measurement comparison. Table 1 below indicates five operating modes: Take-off, Climb out, Cruise, Approach and Taxi . For each mode, the table indicates typical po wer settings used in ground static tests. (Details are given in Appendix 3.) All FOCA data, establ ished with ground static tests, are based on the suggested modes and power settings below.

Table 1: Power Modes Mode % of max. Propeller HP Take off 100 Climb out 85 Cruise 65 Approach 45 Taxi Operator’s Manual

Calculation of emissions of an aircraft at and in vicinity of an airport (landing and take-off cycle, LTO) =
Number of engines * (Taxi time * Taxi fuel flow * Taxi emission factor + Take-off time * Take-off fuel flow * Take-off emission factor + Climb out time * Climb out fuel flow * Climb out emission factor + Approach time * Approach fuel flow * Approach emission factor)
Calculation of emissions of an aircraft during cruise =
Number of engines* (Cruise time * Cruise fuel flow * Cruise emission factor)



### 2.1.2 Suggested Times in Mode for Emission Calculation
Table 2 suggests standard times in mode for piston engine LTO emission calculations according to the equation above.
Table 2: Standard Times in Mode for Piston Engines Mode Time (Minutes) Take off 0.3 Climb out 2.5 Cruise - Approach 3 Taxi 12

Remarks: 1) Part of the piston engine powered aircraft are intensely used for training and school flights, where two movements (= 1 LTO) are reduced to one circuit around the airport. The times in mode try to take a representative mixture between LTO, circuit flying and the performance variability between different aircraft into account. This can be very country dependent. 2) Cruise Time: Actual time outside LTO. In absence of such information FOCA suggests a mean cruising time of 20 minutes for small ai rcraft for central Europe, corresponding to a mean total flight time of 30 to 40 minutes per flight, when the LTO is included.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 3) The time value for taxi (in and out) seems to be rather small but is considered appropriate for small airfields where most of piston aircraft operate. At airports, total taxi time might be higher and should be adjusted according to the local situation. 4) At climb out up to 3000ft AGL, the majority of engines below 200 HP are operated at full power. In those cases, it would be more realis tic to calculate the climb segment of the LTO with take-off emission factors and take-off fuel flow.
Table 3 suggests times in mode for the LTO cycle, if circuit flying around airports is excluded. This is not suggested for full airport emissions inventories, however it can be used to compare piston engine emissions in the LTO band of 3000ft above ground level to other types of engines.
Table 3: Full LTO Times in Mode for Piston Engines Mode Time (Minutes) Take off 0.3 Climb out 5 Cruise - Approach 6 Taxi 16



### 2.1.3 Cruise Emission Factors
Most of the piston engines which are dominating t he market have manual air/fuel mixture control to adjust the engine to different altitudes (in fact to density altitude). This air/fuel mixture adjustment has to be done by the pilot during flight whenever the ai rcraft changes its power c onfiguration and altitude. This adds a particular degree of complexity to representative emission s measurements, because emissions can vary strongly even if the same aircraft is flying at the same mass, same density altitude, same speed, configuration and attitude. The variatio n comes from different “leaning techniques” and is also dependent on the pilot’s experience, training and available engine cockpit instrumentation (sections 2.2, 2.3 and Appendix 2). For this reason and as a result of in-flight measurements, the cruise mode is given twice in the data sheet:

Table 4: Extract of data sheet PF01. CRUISE and CRUISE LEAN values. EI = emission factors

MODE POWER SETTING (%) TIME (minutes) FUEL FLOW (kg/s) EI HC (g/kg) EI CO (g/kg) EI NOx (g/kg) PM (...) (...) TAKE-OFF 100 0.3 0.0182 12.7 818 6 CLIMB OUT 85 2.5 0.018 12.3 787 6 CRUISE 65 60 0.0152 6.9 750 8 APPROACH 45 3 0.0098 11.5 1055 2 TAXI 12 12 0.0038 42.6 1123 0 CRUISE LEAN 65 60 0.0138 5.4 473 23

CRUISE : Measured at very rich air/fuel mixture, calle d “full rich”. Well defined and for comparison only

CRUISE LEAN: to be used for cruise emission calculations. The definition of the mixture comes from operator’s manuals and in-flight studies. “Cruis e lean” values are the result of the most common “leaning technique”, where pilots manually adjust the air/fuel mixture to less rich conditions. ”Leaning” is a common term, however in most cases it means that the engine is run leaner than at full power but still at a rich air/fuel mixture (Details are given in sections 2.2, 2.3 and Appendix 2). Some of the engines do not have a manual mixture cont rol. On the datasheet this is either indicated with remarks or with the same cruise values for CRUISE and CRUISE LEAN.



### 2.1.4 Calculated LTO and 1 hour cruise emissions on data sheets
Table 5 (below): Extract of data sheet PF01. LT O fuel consumption and total HC, CO and NOx emissions are marked in yellow. One hour cruise fuel consumption and emissions are marked in green. All values for LTO and CRUISE are calculated based on t he suggestions made in sections 2.1.1 to 2.1.3Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern MODE POWER SETTING (%) TIME (minutes) FUEL FLOW (kg/s) EI HC (g/kg) EI CO (g/kg) EI NOx (g/kg) PM (...) (...) TAKE-OFF 100 0.3 0.0182 12.7 818 6 CLIMB OUT 85 2.5 0.018 12.3 787 6 CRUISE 65 60 0.0152 6.9 750 8 APPROACH 45 3 0.0098 11.5 1055 2 TAXI 12 12 0.0038 42.6 1123 0 CRUISE LEAN 65 60 0.0138 5.4 473 23 LTO TOTAL FUEL (kg) or EMISSIONS (g) 7.53 174 7327 24 CRUISE 1HOUR FUEL (kg) or EMISSIONS (g) 49.7 268 23490 1149



### 2.1.5 Data Quality and Accuracy
FOCA data sheets are primarily based on the "low cost" STARGAS 898 measurement system and the MEXA 1170 HFID (see Appendix 1). For each engine on ground static tests, a minimum of three measurements have been performed for every power mode. Data variability has been statistically checked with a T-test and 90% confidence interval (Example in Appendix 3). The particle emission measurements have been perfor med in collaboration with German DLR. Primary focus were the nanoparticle and carbonyl emissions. There is presently no "low cost" for such measurements. First measurements have been made wi th HBKEZ. The measurement results have been reproduced one year later with the DLR measurem ent system and the same aircraft (see Appendix 4 for details). Swiss FOCA sees the primary purpose of the data co llection in their application in emissions inventory calculations. The measurement system that has be en used so far (STARGAS 898) does clearly not represent certification standard. However, t he measurement quality achieved by requirements described in Appendix 1a/b) is considered sufficient for emissions inventories. This conclusion is based on the following comparisons:
FOCA has started to use a total HC FID in paralle l to the "low cost" ST ARGAS NDIR HC measurement and has done crosscheck measurements with a chemiluminescence (CLD) NO x analyzer. From comparative measurements with differe nt systems, correction factors for the "low cost" gas analyzer with NDIR HC and electrochemical NO probe hav e been derived. (See Appendix 5 for details.) In addition to that, FOCA has been given the chance to use HORIBA OBS 2200. This system meets the requirements for high quality certificati on emissions measurements (THC FID, NO/NO 2 CLD, heated sampling line at 191°C, exhaust flow meas urement etc, see Appendix 1.g) and is very compact, originally designed and tested for on board meas urements in cars and trucks under real operating conditions. The system has been used for compar ative ground static tests in the ECERT project. It has then been installed for the first time in an airc raft and flown successfully, providing high quality real time mass emissions data at one second intervals, together with position, altitude, speed and flight time. Complete, 4-dimensional resolved emissions inventories have been measured and recorded, from taxi out to taxi in. Those real world data have been compared to the STARGAS data and to the existing LTO-modelling data. (Det ails are given in Appendix 2.)
From the present experiences FOCA concludes that the results for a "low co st" measurement system described in Appendix 1a/b, as well as the calculations and corrections described in Appendix 5, would be in a systematic error band of +-15% for the measurement itself. This is considered acceptable because operational issues and individual engine tuning can change emission factors drastically (See Section 2.2.2 and Appendix 2) and because of t he low system costs (app roximately one tenth of a common measurement system, used for emission cert ification). In the opinion of FOCA, overall representation of emission factors mainly depends on the choice of operating points and on the real flight operations. FOCA has taken this into acc ount by doing in-flight emission tests.

Four aircraft have been used for ba sic testing (Appendix 2). The first two aircraft HBEYS and HBKEZ have been tested in-flight, followed by in-field stat ic ground tests until it was possible to reproduce useful in-flight data on ground. The third aircraft HB KIA has been first tested on ground on the basis of the ground power setting procedur e developed with the HBEYS and HBKEZ measurements. Once this had been completed, HBKIA has been tested in flight in order to validate the ground test procedure (Appendix 3). The HORIBA OBS 2200 ha s been used for cross check ofHBKEZ static ground measurement data accuracy and for in-fli ght measurement of HBHFX in order to produce "real world" emissions inventories.Reference: 0 / 3/33/33-05-003.022

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### 2.1.6 Data Download
This report, as well as the full documentation (App endices), available data and individual datasheets can be downloaded from the FOCA webpage.

Download link:
http://www.bazl.admin.ch -> for specialists -> environment -> engine emissions

List of abbreviations, used in the data sheet table:
FOCA UID: Unique identifier for piston engines whic h can be used as the key to link aircraft with engine data. “P” stands for piston engine, “F” stands for FOCA measurement.

Rated HP: Rated Horse Power. Manufacturer decl aration. The number may vary within certain engine model variants. If a certain engine m odel can not be found in the table, Horsepower, Combustion Tech, Cooling System and Technology Age can give hints to choose the nearest possible representative engine.
Piston Engine Model: To simplify application of the table, only the basic model designations without derivative variants are given. Example: TCM IO -520 A, B, C, D, E, F, J, K & L are represented by TCM IO-520. In most cases the variants do not produce significant change of emission factors. The actual va riant measured is indicated on the FOCA datasheet.
Combustion Technology: If a certain engine model can not be found in the table, Combustion Tech can give hints to choose the neares t possible representative engine.
Cooling System and Fuel Type: If a certain engine m odel can not be found in the table, Cooling System and Fuel Type can give hints to choo se the nearest possible representative engine. Piston engine particle emissions are highl y influenced by fuel type. Some of the engines that have been measured with AVGAS100LL are allowed to run on unleaded fuel. This has not yet been incorporated in the database.
Technology Age: If a certain engine model can not be found in the table, Technology Age can give hints to choose the nearest possible repr esentative engine. 1960 technology engines are currently dominating the market.
Data Source: For completeness, the FAEED 3 data that Swiss FOCA has been used so far are incorporated in the table. Comparison with FOCA ECERT measurements has shown that existing FAEED data seem to be reas onable for the purpose of LTO-emissioncalculation. Therefore ECERT has primarily focused on missing and more modern engines to complete the picture.

3 FAEED = US Federal Aviati on Engine Emissions DatabankReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 

### 2.2 General findings about ai rcraft piston engine emissions

2.2.1 Combustion basics

a) What goes in? Composition of AVGAS 100LL
AVGAS (aviation gasoline) is a complex mixture of hy drocarbons (HC) plus additives. The fuel must comply with the specification of the US standar d ASTM D-910 which ensures safe engine operation at the whole ambient temperature and pressure range, as far as the fuel is concerned.

Additives:

• Most of the AVGAS available is AVGAS 100LL, a leaded fuel. The “LL” stands for “Low Lead” which is a relative term. AVGAS 100LL can contain up to 0.8 g lead (tetra ethyl lead) per kg fuel! The lead additive is used to get the high octane rating of 100/130. Lead additives have been introduced many decades ago, mainly to impr ove the power to weight ratio of aircraft piston engines by increasing the compression rati o in the cylinders. FOCA assumes that about 30% of the global gasoline aircraft piston engine fleet still needs such high octane fuel to suppress knocking or self-detonation at high compre ssion ratios and at suboptimal air/fuel ratios and ignition timings.

• If the fuel is leaded, it contains a similar amount of ethylene dibromide. This substance is used to remove lead deposits from the combustion parts of the engine. Otherwise spark plugs can be destroyed and deposits on valves can obstruct their proper operation. As lead, the scavenger is an environmentally harmful substance, believed to be carcinogenic and contributing to stratospheric ozone depletion.

• Dyes (to colour code the fuel): The blue dye in AVGAS 100LL (1,4 – dialkylaminoantraquinone) is causing skin irritation and allergic reactions.

• Antioxidants (preventing gums and sediments)

• Icing inhibitor (optional)

• Electrical conductivity additive (optional)
Like car gasoline, AVGAS 100LL contains some amount of benzene, a toxic substance known to be carcinogenic.
Note: There are much cleaner alternatives to AVGAS 100LL, even cleaner than car gasoline. During the project, FOCA has started collaboration with Sw edish Hjelmco Oil, the producer of a synthetic, very pure unleaded AVGAS, meeting ASTM-D910 s pecifications. (See Appendix 4 for details.)

Figure 1: Composition of AVGAS 100LL, used for part of the FOCA emission tests. The composition analysis has been done with gas chromatography and mass spectrometry at DLR Stuttgart/Germany. [C. Wahl/DLR]Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Some aircraft/engine combinations are certified to use motorcar gasoline (MOGAS). In Europe, this fuel is lead free but with the high bandwidth of possible composition and some alcohol content, there are limitations for its safe use. Besides this, not onl y the engine (which is in many cases not the problem) but also the airframe must be certified to us e that fuel, which basically comes from requirements for the fuel system.
For theoretical calculations of the fuel combustion, it is useful to look at a representative AVGAS (or MOGAS) hydrocarbon molecule. Figure 2 below shows a typical distribution of the carbon number in AVGAS molecules.
A “mean” AVGAS molecule is considered to be composed of 7 Carbon atoms and 13 Hydrogen atoms ( C 7 H 13 ). For all standard mass emission calculations of FOCA, this molecule is used (see Appendix 5).

Figure 2: Carbon number distribution of the hydrocarbon molecules in AVGAS 100LL [Chevron].

b) How much air to make the fire?

Fuel and air are needed to ignite a fire. Generally, the more of both there is, the hotter the flame. But the combustion will only be “optimal” at certain fuel/air ratios.

The combustion conditions at which the fuel/air ratio is, such that there is neither an excess of fuel nor of air, is called the stoichiometric mixture within a cylinder. At this condition, all of the reactants are present in the chemically ideal amounts for combustion and the greatest amount of total combustion heat per unit of air is produced.

At stoichiometric mixture, the cylinder is running at “ peak EGT” (peak Exhaust Gas Temperature)

. Peak EGT mixture can be seen as the “ maximum-heat mixture point ”.

In order to estimate the amount of air that is needed to burn a defined amount of fuel at stoichiometric mixture, the chemical reaction equation is used. Note , that in a combustion process the mass of all reactants going into the process is conserved. Mole cules are reformulated but nothing is lost. The fuel and air have been reformed to other substances, giving heat during the formation process. Intake mass equals exhaust mass.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Calculation with reaction equation for complete combustion:

1 C 7 H 13 (AVGAS) + 10.25 O 2 (Oxygen from Air) + 39 N 2 (Nitrogen from Air) react to (“burn” to):

7 CO 2 (Carbon dioxide) + 6.5 H 2 O (Water vapour) + 39 N 2 Taking the number of necessary molecules for the complete combustion from the equation above and multiplying them with the molar masses of the mo lecules, then, for 1 Mol of AVGAS the result is:

97.18g C 7 H 13 + 328.0g O 2 + 1092g N 2 react to 308.07g CO 2 + 117.13g H 2 O + 1092g N 2 (1)

Therefore, 97.18 g fuel is reacting with 1420 g Air (O 2 + N 2 ). This is a mass ratio of 1 : 14.6
The conclusion is that for complete combustion of 1 kg fuel, about 15 kg air is necessary!

Fuel / Air ratio 1kg / 15 kg = 0.067 (for stoichiometric combustion)

c) What comes out?
From the chemical mass equation (1) above it can also be seen that for complete combustion:
1 kg fuel (AVGAS) produces

• 3.17 kg CO 2 (Carbon dioxide)

• 1.21 kg H 2 O (Water vapour)

CO 2 and H 2 O are no pollutants, but are both atmospheric green house gases due to their infrared (= heat) absorption properties. Most of the N 2 (78Vol% in ambient air) passes combustion unchanged.

Hot air: N 2 , CO 2 and H 2 O are dominating the exhaust gas.
Besides hot air, pollutants are formed.
Causes for the production of pollutants can be:
Oxygen deficiency : There is too little oxygen to react the C from the fuel to CO 2 (Carbon dioxide). It will react to CO (Carbon monoxide) only. The fuel can not react completely to CO 2 and H 2 O (water) and a complex mixture of hydrocarbon molecules (C x H y ) will be exhausted, also named HC.
High combustion temperatures and pressures with short chemical reaction times : The nitrogen (N 2 ) contained in ambient air (78V ol%) together with the oxygen (O 2 ) from ambient air (21Vol%) start to react in the combustion cham ber (cylinder) to form nitrogen oxides (NO and NO 2 , named as NO x )

Pollutants: CO, HC, NO x , soot, lead bromides (AVGAS 100LL)

FOCA measurements concentrated on CO, total HC and NO x emissions, which are reported in FOCA data sheets. Soot and other partic les were measured by DLR Institute of Combustion Technology, Stuttgart, in collaborative projects (Appendix 4).

d) Properties of pollutants
Carbon monoxide (CO) :

• Toxic gas, e.g. blocking oxygen transport in blood.

• Chemically unstable, normally converted to CO 2 after a few days in the free atmosphere.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Hydrocarbons (HC) :

• Hundreds of possible H-C-molecules (e.g. form aldehyde) with different health impacts, some carcinogenic.

• Some are converted with sunlight (UV) to r adicals, contributing to ground level ozone production. In the troposphere, ozone is able to strongl y react on different substances. Ozone is able to “clean” the troposphere (+), but it is itse lf toxic with increasing concentrations (-).
Nitrogen Oxides (NO x ) :

• NO converts to NO 2 within minutes to hours in free atmosphere.

• NO 2 (yellowish colour) is toxic for the respiratory system.

• With sunlight (UV), NO/ NO 2 contributes strongly to the low level ozone production



### 2.2.2 Air/fuel mixture adjustments

a) Dominant “old tech” engines require manual air/fuel mixture control
Around 70% of all aircraft piston engines which can be found in the global market have the following general concept:
- Opposed cylinders in boxer configuration - Big cylinder volume, relatively low RPM, no reduction gear for the propeller - Air cooled (direct air cooled cylinders, indirect via oil cooler) - Carburettors without ambient conditions or combustion sensing devices - Most injection systems without ambient conditions or combustion sensing devices - Injection systems not timed with cylinder valve movements - Constant ignition timing, not taking into account engine RPM (except for start-up) - Everything mechanical, no electronic devices
This general concept, which is called here “ old tech ” or “conventional”, has not changed for many decades. Contributing factors were t he very good power to weight ratio, the “simplicity” (compared to amodern car engine) and very good reliability and durability of such engines. Keeping in mind that aircraft engines have to pass an airworthiness certificat ion process, it must be understood how costly it is, to certify a complex engine. At the same time, t he market of aircraft piston engines is rather small. This situation is completely different from that ofcar engines, which are sold in millions with less demanding requirements. In addition to that, as long as leaded AVGAS can not be completely replaced, it is difficult to install elec tronic mixture control devices.

Figure 3: Basic design parameters of an “old tech” aircraft piston engine
The disadvantage of the “old tech” engine is:

- High specific fuel consumption (at least at high power settings)

- High specific emissions
Increasing flight altitude (decreasing air density) in creases the fuel/air ratio (of normally aspirated engines.) Reliabilit y “Simplicity” Light weight

Durability Proven Concept

Reasonable engine costsReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Because carburettors and fuel injectors of “old tech” aircraft piston engines can not sense air density and resulting fuel/air ratio, the air/fuel mixture has to be adjusted manually . Without correction, the engine runs increasingly richer, the lower the air density is, and besides waste of fuel and excessive emissions, it may finally quit.

Picture 1: Throttle (black), propeller (blue) and mixture handle (red).

In addition to the throttle, the mixer handle controls

- Engine power

- Engine temperature

- Emissions performance

- Specific fuel consumption
The mixer position plays a vital role for the re sulting emissions. That is why any measurement of aircraft piston engine emissions requires proper investigation of mixer operation.
b) Rich and lean mixture definition with lambda ( λ )

It is convenient to indicate actual air/fuel mixt ures, obtained with a certain setting of the mixer handle at certain ambient conditions, by comparison with th e stoichiometric air/fuel mixture. The term “lambda probe” is known from gasoline car engines with catalyst .The word “lambda” comes from the greek letter λ . The “lambda probe” (“ λ – probe”) actually measures the oxygen content in the exhaust. The probe signal is used to control the air/fuel mixtur e in the injection system of a car engine to be near stoichiometric. If the air/fuel mixture is stoichiometric, λ equals 1. If there is too much fuel for the combustion (oxygen deficiency), λ is smaller than 1. If there is excess oxygen for the combustion, λ is bigger than 1.

Definition of λ :



### mixture rich mixture lean : AVGAS

: 1 : 1 : ) ( 6

. 14 ) ( : ) ( : ) ( :

< > = =

λ λ λ λ

Note tric stoichiome measured Fuelmass Airmass for tric stoichiome Fuelmass Airmass measured Fuelmass Airmass

“lean” = poor in fuel (excess oxygen), “rich” = fuel excess (oxygen deficiency)
Example : If a carburettor is mixing air and fuel in a ratio of 10 kg to 1 kg, then

λ = (10 : 1) : (14.6 : 1) = 10 : 14.6 = 0.68 -> The engine is running rich, with oxygen deficiency.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern c) Mixer = lambda control
Figure 4 below shows lambda values in function ofpercent maximum continuous power for a TCM IO550B engine. The grey shaded area shows the “full ri ch” lambda region for that engine. This is the lambda region, obtained at mixture “full rich” for sea level ISA conditions. At taxi power, the engine runs at about lambda = 0.70, getting richer up to 20% power. With increasing power, if the mixer is left at “full rich”, the engine runs slightly less ri ch (lambda = 0.78) and towards maximum continuous power again richer with lambda around 0.74.
If the mixer handle is pulled back at a certain throttle setting, for example at 45% power (as shown in figure 4, red line), lambda increases (in most cases while reducing the fuel pressure). The engine runs less and less rich . Still rich, the best power point is pa ssed. Pulling the mixer handle further back, the stoichiometric mixture is reached, wh ich gives the highest exhaust gas temperature (EGT peak). If that point is trespassed, the engine runs lean and the best economy point is approached. As the pilot pulls further, the engine may run rough and quit. At the maximum pulled position of the mixer handle, fuel is cut off and the engine will definitely quit.
It must be noted that during the mixer operation, t he engine power changes. So, for the measurement shown below, also throttle corrections had to be ma de, in order to maintain constant power. FOCA chose a low power setting for this measurement to keep engine temperatures of the air cooled engine well below the limit, as the aircraft was standing. But the variations of lambda with the mixer positions are valid for all possible power settings and are not limited to the measured engine (example).

Mixture

Full rich

Lean Rich

Fuel cut off

Figure 4: Lambda values in function of the mixer handl e position, from full rich to lean, measured with TCM IO-550B engine at 45% maximum continuous propeller power. The measurement of lambda is described in Appendix 5. EGT = Exhaust Gas Temperature.

d) Typical values for lambda

λ = 1 EGT peak (maximum-heat mixture point)

λ = 0.85 approx. 100°F rich of EGT peak (max imum-pressure mixture point, best power)

λ = 0.95 approx. 25 - 50°F rich of EGT peak (still a rich air/fuel mixture)

λ = 1.15 approx. 50°F lean of EGT peak (lean mi xture, lowest specific fuel consumption)Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern e) Influence of mixer settings on engine temperature and powerMixtureFull richLeanRichFuel cut off

Figure 5: Influence of mixer position (lambda) on engine temperature, power and specific fuel consumption for a certain fixed throttle setting. Note: This chart has to be read for one single cylinder and not for the whole engine. 1 = full rich, 2 = peak EGT, 3 = peak CHT, 4 = standard cruise mixture, 5 = lean mixture setting. CHT = Cylinder Head Temper ature. [Adapted from TextronTM LycomingTM]

Discussion : At a fixed throttle setting, pulling the mixer from “f ull rich” (Position 1) first increases CHT, EGT and power and improves SFC (Specific Fuel Consumption).
At EGT around 100 °F rich of EGT peak, the best power mixture is obtained.
With further pulling the mixer, with still rich air/fuel mixture, EGT and CHT further increase. At 50° to 25°F rich of EGT peak point (Position 4), the CHT is around the maximum (Position 3) for the given throttle setting. Interestingly, this is the most common cruise power mixture setting for conven-Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern tional “old tech” aircraft piston engines (also obtai ned with the “feel-the-RPM-drop-and-push-back-themixture-1cm-rule” 4 for fixed pitch propeller aircraft, see section k).
With further pulling the mixer, the ai r/fuel mixture gets stoichiometric ( λ =1) and peak EGT is reached (Position 2). CHT has already fallen a little bit. Power and SFC are both decreasing. Past peak EGT , with further pulling the mixer, the air/fuel mixture gets lean ( λ > 1). EGT is decreasing, CHT is significantly decreasing, power is decreasing and SFC reaches the minimum value. This drop of CHT at lean conditions seems to be contradictor y to practical experience of pilots and mechanics, reporting engine overheat damage, when opera ted at lean conditions. This will be discussed in section j).
Best power:

• Best power is obtained at a fuel/air mixture with slight oxygen deficiency ( at about 100°F below and rich of peak EGT.

• At this condition, from incomplete combus tion, an excess of combustion gases is produced (mainly CO).

• The extra gas produced increases the pressure in the cylinder which contributes more to piston movement.

• “Best power mixture” can be seen as the “maximum-pressure mixture point”

• Remember: Piston movement, not heat per se is what results in power.

• Best power is generally about 5 to 7% above power at “full rich” (sea level) mixture.

• At best power, the mixture is giving the most power per unit of air, not per unit of fuel.
Best economy:

• When the mixture is leaned past EGT peak, fuel consumption drops off faster than power production, up to a certain point.

• This point is called the best-sfc point or best economy mixture and occurs at or near 50°F lean of EGT peak

• Note: At best economy setting the fuel consumption can be 40% lower than at “best power”!

f) Influence of mixer settings on emissions

The FOCA instrumentation for measurement and calcul ation of emission factors is described in Appendix 1 and 5. Based on this instrumentation, in-flight testing with different mixer settings has been performed. In order to get emissions (in mass units ), measured emissions conc entrations (respectively emission factors) have to be multiplied with the fuel burn, as explained in section 2.1.1 of this report. Figure 6 below shows the exhaust CO 2 and pollutant concentrations in function of the mixer position at a fixed throttle setting. The concentrations have been measured on a TCM IO-550B engine of the aircraft HB-KIA.

Note: 1) The shapes of the curves in figure 6 are representative for all combustion engines (piston engines, jet engines (turbofans), etc.). 2) If on the one hand, the concentration (respectively emission factor) of a certain pollutant in the exhaust and the fuel burn are both high, resulting emissi ons are high. On the other hand, a fuel burn reduction can reduce emissions, even if the concen tration (or emission factor) of a pollutant is not lowered.
Taking the concentrations shown in figure 6 and the dec reasing fuel flow from right to left into account:

• At mixture “full rich”, CO is extremely high, HC high, NO x low. Direct CO 2 is fairly low, but taking the later recombination of pollutants (mainly CO) to CO 2 into account, total CO 2 will be very high (corresponding to the very high fuel burn).

4 This is a standard rule, taught in many flight schools, applied for engines without EGT probe. With fixed pitch propeller, any change in engine power will be noticed by an engine RPM change.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern • At mixture “best power”, CO and HC become lower, NO xbecomes higher with increasing engine efficiency, total CO 2 high.

• At “standard cruise mixture” (rich of EGT peak), CO and HC are further reduced, NO x sharply increases and total CO 2 is still high.

• At “peak EGT”, CO is very low, HC low and NO xnear the maximum value (complete combustion with NO x “trade-off”). Total CO 2 starts to decrease.

• At “mixture lean” (around λ = 1.15), CO and HC are very low, NO x relatively low and CO 2 is lower. The engine is at its best specific fuel consumption. Low pollutant concentrations and low fuel burn lead to lowest possible emission s. If not highest possible power is needed, then this would be the preferred mixture setting.

In conclusion, the preferred mixture setting

• For lowest emissions

• For lowest fuel consumption per flight distance (in many cases)

• For reasonable cylinder operating temperatures (see also figure 7)
Would be 50°F Lean of EGT peak, at λ around 1.2

It is known from AFM and engine operating manuals that this mixture setting

• Must not be applied with most of “old technology” engines

• Does not work with most of “old technology” engines
The reason and possible solutions will be discussed in section j)



### 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2

0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 Mixer position (lambda)Relative Exhaust Concentration



### Rel. Vol% CO2 Rel. Vol% CO Rel. ppm HC Rel. ppm NOxMixtureFull richLeanRichFuel cut off 

### 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2

0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 Mixer position (lambda)Relative Exhaust Concentration



### Rel. Vol% CO2 Rel. Vol% CO Rel. ppm HC Rel. ppm NOxMixtureFull richLeanRichFuel cut off

Figure 6: The figure shows the change of exhaust CO 2 and pollutant concentration in function of the mixer position (lambda). The concentrations are given in a relative scale in order to show them all in the same figure.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern g) Influence of mixer settings summary



## • CO emissions



## • HC emissions



## • NOx emissions



## • Particle mass 1)



## • Power 2)



## • SFC



## • CHT 4)



## • EGT



## • Combustion Stability 3)MixtureFull richLeanFuel cut offRich Peak EGTMixtureFull richLeanFuel cut offRich Peak EGT

Figure 7: Influence of mixer position on emissions, power, specific fuel consumption, engine temperatures and combustion stability at a fixed throttle setting for one cylinder.

Note 1) : Particle mass (and number) emissions are gener ally high. Emissions are at the same magnitude as a car diesel engine without particle filter, main ly for two reasons: Extremely rich mixtures at high power (black carbon emissions) and leaded fuel, producing a lot of lead bromide particles. With unleaded AVGAS, at lean conditions, particle mass emissions would be very low (Appendix 4). Note 2) : At lean conditions, there is a significant power drop , if the throttle is fixed. In the times of piston engine driven airliners, after lean mixture had been established in the cruise, throttle was increased to compensate for the power drop. This changed the mixture and temperature distribution again and in an iterative process, the lean mixtur e at the same power level as the rich mixture was established. This technique can still be used today, if the engine and instrumentation allow. Note 3) : Combustion stability is lost, if the mixture is too rich (engine flooded with fuel) or too lean (combustion temperature too low and combustion re action too slow). The combustion stability range is wide for rich mixtures and narrow for lean mixtures. Note 4) : Lean mixture in the cylinder is not only beneficial for lowest emissions but also for lower CHT. Final note: Diesel piston engines always run lean on steady-state conditions over the whole operating range.

h) Why “full rich” at high power for “old tech” engines?

• Most “old tech” aircraft piston engines are air cooled.

• At full power, the cooling performance of air cooled engines is often too weak. There is generally less cooling air flow in climb than in cruise or descent, because the aircraft flies slower and has a different attitude. But in clim b, the engine is working at the highest load. Therefore, additional cooling is required: Incomplete combustion at very rich mixtures (lambda 0.7) reduces combustion temperatures, thus keeping cylinder head temperatures relatively low. This is internal combustion cooling by wasting fuel.

• At high power settings, some excess fuel may be necessary to suppress detonation also due to invariable ignition timing.

Note: Lean mixtures reduce combustion temperatures as well, but with greater loss of power.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern i) Why “rich” near idle power?

• “Rich mixture” ensures safe engine operation in engine transient conditions : When the throttle is opened, the engine experiences a sudden inrush of air. Therefore, a transient lean mixture condition exists. The mixture must be rich enough, so that suddenly opening the throttle does not kill the engine.

• “Rich mixture” ( λ around 0.7) is necessary for cold-weather starting ability.

• Air-cooled engines need a “fudge factor” for possi ble too lean conditions of single cylinders under worst case conditions.
Note: “Rich mixture” can be any mixture with λ < 1 (mixture rich of EGT peak). It is not necessarily the “full rich” carburettor setting.

j) Uneven distribution of mixture and temperature in “old tech” engines
From measurements and investigation, the author th inks that the primary cause for problems with running “old tech” piston engines lean in cruise is the uneven mixture and temperature distribution in the different cylinders. Figure 8 sh ows, what temperature and mixture distribution would be required, in order to be able to run the engine lean as a whole. All cylinders would have their temperature peaks at exactly the same mixer position. In that case, 50 °F lean of EGT peak would be a clearly defined operating point for the engine, with all cylinder head temp eratures lower than for the same power at rich mixture. If the cylinders run like this, the engine can be run lean at low temperature, low SFC and lowest emissions!
Note: The temperature can vary in absolute terms from cylinder to cylinder, due to differences in cylinder charge and piston compression.MixtureFull richLeanRichFuel cut off

Figure 8: Requested mixture distribution in four cylin ders for a certain mixture position. All four cylinders pass peak temperature at the same mixture position.
In reality, all cylinders of “old technology” aircra ft piston engines normally have their individual peak temperature at different mixture settings (figure 9)! Additionally, peak temperature can vary significantly from cylinder to cylinde r.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Reasons for this (not to be considered complete):

• Different distances from carburettor to cylinders

• Cooling air distribution causes cooling differences.

• Fuel droplets that have to travel “uphill”, agai nst gravity in the induction system tend to reach the nearer cylinder more easily.

• Fuel injectors: Bad nozzle tuning

• Airflow anomalies
Many intake systems are so poorly tuned that lean misfire begins in the leanest cylinder(s) well before peak EGT is reached in the richest cylinder(s).

• Recall: It takes fuel and air to make the fire. The more fuel and air, generally, the hotter the flame. This can be expressed by the term “cy linder charge”. Cylinders normally are differently charged.

• Also, the more compression a cylinder has during combustion, the higher the final temperature.

• As the mixture handle is pulled back, the riches t cylinder will be the last one to reach the peak EGT (figure 9). It is well possible that this cylin der can reach the highest EGT of all cylinders:
It is possible for the richest cylinder to give the highest peak EGT.MixtureFull richLean ??RichFuel cut off

Figure 9: Uneven distribution of mixture and temperatur e in an “old tech” engine. At a certain mixture position, all cylinders have a different lambda and different temperatures!Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern In the example of figure 9 above, it is assumed that mixtur e is set to 50°F lean of EGT peak (left black line) with reference to cylinder 1.

The leanest cylinder is that one, which first reaches “EGT peak” , when the mixer is pulled. In the example, it is cylinder no. 4

. At the selected mixture setting (for cylinder 1), the cylinder 4 can already be so lean that it reaches the lean misfire condition . In practice this can sometimes be no ticed by a slightly rough running engine. Of course, this condition is negative for engine life. And note in this example, no 4 is running cooler than cylinders 1 and 2. The richest cylinder is no 2 . All other cylinders have passed EG T peak and this one just reached it. The coolest cylinder, in absolute terms, is cylinder no 3, despite the fact, that it is running near EGT peak. The hottest cylinder , in absolute terms, is cylinder no 1 . This one has e.g. the best charge and/or compression of all four cylinders.
Do not confuse “leanest” and “hottest” cylinder.

• The leanest cylinder is that one, which first reaches “EGT peak” , when the mixer is pulled back

• The richest cylinder is that one, which last reaches “EGT peak”, when the mixer is pulled back

• The hottest cylinder , can be the richest e.g. if combined with best charge and/or compression.

Conclusions

• If all cylinders together are running lean, temperatures can be lower than with rich of EGT peak or best power point.

• At lean mixture, the combustion process is slowed down and the combustion pressure on the piston and on the cylinder head is dist ributed over a longer period of time, reducing material stress

.
• At lean mixture , the engine reaches the lowest specific fuel consumption and the lowest possible emissions.

• Rich mixtures have a much larger bandwidth of lambda for engine operations than lean mixtures (figure 7). Lean mixtures require better mixture control.

• Altitude changes (e.g. descent) are someti mes less critical with rich mixtures.

• For engine transient power conditions, rich mixtures are needed.

• Most “old tech” engines have a higher risk of one ore mo re cylinder(s) being at high internal temperatures, without noticing it. Therefore such engines must not be run lean.

• Going very lean with “old tech” engines can cause one ore more cylinder(s) to reach the lean misfire condition. Therefore such engines must not be run lean.

Picture 2: Running lean for thousands of hours is nothing new: The Wright R-3350 engine (DC7 etc.) has been operated on lean mixture during cruise (historical example). As explained above, lean mixture requires better mixture control. In former times this was assured e.g. by symmetrical engine design (equal distances for air intake, symmetrical cooling air flow etc) and a fuel flow and power based leaning technique. A flight engineer was looking after the engines all the time during flight. In a modernized piston engine aircraft, lean operation is possible by use of a fuel injection system with carefully tuned injection nozzles and/or with FADEC, controlling each cylinder separately.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern k) Investigated manual mixture setting procedures
Setting the air/fuel mixture without EGT : Many “old tech” piston engine aircraft with fixed pitch propeller do not have any exhaust gas temperature inst rumentation. Therefore no information about exhaust gas (and internal combustion ) temperatures is available. To handle the mixer of such aircraft, pilots are often instructed to adjust the mixture with a "rule of thumb": At a fixed throttle setting, the pilot pulls the mixture lever slowly back and leans t he mixture until a slight RPM drop of the fixed pitch propeller is recognized. At this condition, the engine is running slightly lean. After that, the pilot pushes the mixture lever slightly forward (about 1 cm) and the engine is running slightly rich . After a while, the pilot checks cylinder head and oil temperature.
Rule for fixed pitch propeller engines without EGT for cruise below 75% propeller power: “feel-the-RPM-drop-and-push-back-the-mixture-1cm ”. This mixture adjustment for cruise should be done at every altitude with engine propeller power not exceeding 75% (refer to AFM).

The effect of the rule was studied with FOCA airc raft HB-EYS (In-flight measurements with application of the above rule are documented in Appendix 2, se ctions 1 and 3). The measurement system showed the resulting lambda for a certain mixer setting on a small TV-monitor. In doing so, during the flight, the effect of a certain mixer setting on lambda and emissions could be immediately observed.
With a fixed pitch propeller engine, without EGT and the aircraft at constant climb angle, best power mixture is obtained with the mixer position giving the highest engine RPM. Usually, from this mixer position, the mixture is slightly enric hed for better engine cooling. For a normally aspirated engine, this adjustment should usually be done in cl imb above 5000 ft density altitude (refer to AFM).
General findings for the rule:

• If the pilot applies the rule slowly and tries to sense possible engine vibrations 5 with feet on the floor, the resulting lambda is around 0.93 to 0.95 which corresponds quite nicely to a 50°F rich of EGT peak setting.

• With increasing density altitude, the “rule of thumb” leads to increasingly richer mixture.

• Adjusting the mixture in static aircraft condition, e.g. prior to take-off at high density altitude (mix for highest static RPM (best power) and en rich) leads to a richer mixture than applying the rule during flight.

• Strictly speaking, the rule is only applicable fo r cruise but can be used to a lesser extend to climb. For descent, at a fixed mixer position, the mixture gets leaner, and eventually, the engine may quit. Therefore many AFM call for mixture “full rich” in the descent, which is very far from optimum for the engine (see 2.3.1 c).
Setting the air/fuel mixture with EGT : The standard setting is often 25 to 50°F rich of EGT peak during cruise.
Some engines may – according to AFM – run lean of EGT peak. In fact, the engine installed on HBKIA, does not seem to have an extremely uneven mixt ure distribution and it is not surprising as the AFM describes lean of peak operation. But in spit e of that, during an in-flight measurement at lean conditions with HB-KIA, one or more cy linders were clearly running hot (high NO x emissions) without being noticed by cockpit instrumentation (see pr evious section j and Appendix 2, section 5)!
General findings for EGT mixture setting:

• Proper mixture adjustment with EGT needs time (5 minutes easily). The temperature probe(which is a thermocouple in many cases) is reacting slowly and the engine needs time to stabilize temperature at a certain throttle/mixer setting.

• Most EGT leaning techniques start with finding EGT peak. This means that at least the measured cylinder has to run on EGT peak for a certai n time, which may in fact not be beneficial for cylinder life, if by chance, this is the hottest cylinder.

5 Additional vibrations can be caus ed, if one or more cylinders are in a very diffe rent mixture state compared to others, as sho wn in section j) of this report. A mixer position with increased engine vibrat ions should be avoided.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern • A single probe for EGT (and CHT!) on a four or six cylinder “old tech” piston engine is considered not sufficient for proper mixture adjustment (see previous section j). Certified instruments, showing all cylinders and exhaust temper atures simultaneously, would be preferred.

General findings for all “old tech” engines:

• For every change of power configuration and al titude (air density change), the mixer position should be changed.

• Applying “carburettor heat” at a fixed throttle pos ition enriches the mixture. The hotter air in the intake is less dense and this has the same effect as flying higher. Therefore, the mixture should be adjusted to less rich conditions after applying carburettor heat.

• Mixer adjustments, if done properly during fli ght, can consume a considerable amount of pilot concentration and can distract cons iderably from primary tasks (fly the aircraft, look out, etc.), especially, if pilots are not well trained.

l) Mixture adjustment technique with fuel flow

• Whenever possible, install (certified) EGT and CHT on every cylinder exhaust and cylinder head.

• Whenever possible, install a (certified) fuel fl ow transducer in the fuel line(s) and a corresponding fuel flow instrument.

Fuel flow method:

• Record the indicated fuel flow for defined power settings at different flight pressure altitudes, with the engine perfectly leaned according AFM (preparation)

.
• Once this table is ready, the engine is leaned at a defined throttle (and RPM setting) based on the fuel flow. Example for a variable pitch propeller aircraft:
For 65% power at 5500 ft PA the setting may be 22.5 InHg and 2350 RPM, The corresponding tabulated fuel flow for 50°F rich of EGT peak is 9.5 GAL Î Pull back the mixer handle to read 9.5 GAL on the fuel flow instrument instantly Î Check EGT and CHT values after a couple of minutes

Setting the mixture by fuel flow goes very fast, does not distract too much from primary tasks. It may also be an advantage for engine life: There is no need to go to peak EGT values every time leaning starts.

Picture 3: Mixture setting investigation with ai rcraft HB-EYS with Lycomi ng O-360 se ries engineReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 

### 2.2.3 Typical emission factors and magnitude of emissions
a) Pollutants of “old tech” engines during la nding and take-off cycle (“full rich” mixture)
In most cases, “full rich” is set during the whole landing and take-off cycle (LTO) . Because of oxygen deficiency, the fuel combustion is very incomplete with a lot of CO, HC and particle emissions.

CO Emission Factors

1280 1300 1320 1340 1360 1380 1400

ModeMass (g/kg Fuel)

CO 1330 1364 1393 1420 1441 1430 1397 1374 1359 TO 3000ft_4124 TO 4000ft_5004 TO 5000ft_5884 TO 6000ft_6764 TO 7000ft_7884 AP 7000ft_7884 AP 6000ft_6884 AP 5000ft_5764 AP 4000ft_4764

Figure 10: Example of CO emission factors, measured in-flight at full throttle between 3000 and 7000ft pressure altitude and at approach power (about 45% of maximum propeller power) between 7000 and 4000ft pressure altitude. The second number to the right of the pressure altitude indicates the density altitude. The measurements were made with HB -KEZ and a Lyc IO-360 engine, which has an extremely rich “full rich” mixture. It can also be seen from the figure that increasing altitude leads to higher CO emission factors, which means that the e ngine gets increasingly richer, if it is not leaned.
Generally, “old tech” engines will produce between 600 and 1200 g CO per kg fuel under “full rich” conditions. Note: The CO emission factor of a je t engine is generally a factor of 1000 lower!

HC Emission Factors

0 5 10 15 20 25 30 35 40 45 50

ModeMass (g/kg Fuel)

HC NDIR 32 32 31 32 32 34 32 31 31 TO 3000ft_4124 TO 4000ft_5004 TO 5000ft_5884 TO 6000ft_6764 TO 7000ft_7884 AP 7000ft_7884 AP 6000ft_6884 AP 5000ft_5764 AP 4000ft_4764

Figure 11: Example of HC emission factors, measured in-flight at full throttle between 3000 and 7000ft pressure altitude and at approach power (about 45% of maximum propeller power) between 7000 and 4000ft pressure altitude. (Example HB-KEZ)
Generally, “old tech” engines will produce between 12 and 30 g HC per kg fuel under “full rich” conditions. Note: The HC emission factor for a jet engine at high power is around zero! (Complete combustion). Only at taxi/idle it will be higher and be of the same magnitude.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Figure 12: Example of NOx emission factors, meas ured in-flight at full throttle between 3000 and 7000ft pressure altitude and at approach power (about 45% of maximum propeller power) between 7000 and 4000ft pressure altitude. (Example HB-KEZ)
Generally, “old tech” engines will produce only a few g NOx per kg fuel under “full rich” conditions. Note: The NO x emission factor of current jet engines at high power is in the order of 20 to 30 g / kg fuel, because of high efficiency and slightly rich mixture at the fuel nozzle. At taxi/idle the NO xemission factor is down at a few g / kg fuel.

Non-volatile particles and soot emission factors:
Figure 13 shows a typical example of a particle num ber - size distribution from an aircraft gasoline piston engine, running on AVGAS 100LL (leaded fuel) under full rich air/fuel ratio at approach setting (HB-KEZ).
For the different power modes,

• the mean particle diameter 6 varied between 49 and 108 nm and

• the total particle concentration varied between 5.7 to 8.6 times 10 million particles per cubic centimetre.
With an assumed specific density for soot of 1.2,

• the estimated particle mass concentration was around 10 000 μ g/m 3 ( micro grams per cubic meter ).
Generally, particle emissions of aircraft gasoline “old tech” piston engines, running on leaded AVGAS at “full rich” conditions, seem to be comparable to diesel car engine particle emissions (see figure 14). Details of these measurements are given in Appendix 4.

6 Most of the particles are ultra fine: 100 nm = 0.00001 mm NOx Emission Factors

0 10 20 30 40 50 60

ModeMass (g/kg Fuel)

NOx 111001111 TO 3000ft_4124 TO 4000ft_5004 TO 5000ft_5884 TO 6000ft_6764 TO 7000ft_7884 AP 7000ft_7884 AP 6000ft_6884 AP 5000ft_5764 AP 4000ft_4764Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Figure 13: Number-size distribution of HB-KEZ engine at approach mode. The mean particle diameter is around 100 nm and the total concentration is in th e order of 10 million particles per cubic centimetre (cm 3 ).

Figure 14: Number-size distribution of a typical diesel passenger car (CDI) at 2000 RPM (increased idle) for comparison to the HB-KEZ measurements [C. Wahl/DLR 2004l]

Based on the measurement of two typical “old tech” aircraft gasoline piston engines (150 and 180HP) the following soot emission factors are suggested (Appendix 4):

Soot Emission Factors (mg soot / kg fuel) Fuel TA AP CL TO AVGAS 100LL (leaded) 50 40 70 100 AVGAS 91/96UL (unleaded) 1 1 2 3Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern b) Pollutants during cruise (at or near “peak EGT”)
In most cases, a mixture setting near peak EGT is chosen for cruise conditions . At peak EGT, the combustion is complete and theoretically, no partially burned fuel products should be produced. In reality, because of inhomogeneous mixture and temp erature distribution in a cylinder, there are still small amounts of CO (carbon monoxide) and HC (hydrocarbons) in the exhaust gas.
Due to maximum combustion heat and short reaction time at peak EGT, the nitrogen from air (N 2 ) reacts with the oxygen from air (O 2 ) in the combustion chamber to form NO (and to a lesser extent NO 2 ), called nitrogen oxides NO x , as explained in section 2.2.2 f). Th is is the classical “fuel burn – NO x “ trade-off: Increased engine efficiency (less fuel burn) can lead to higher NO x emissions. The trade-off is normally discussed in the context of airc raft turbofan engines, but of course it exists also for piston engines, if they are run more efficiently . Automotive engines have exhaust after treatment systems with catalysts to reduce NO x . For aircraft gasoline piston engines, this would also be an option – if the fuel was not leaded.

NOx Emission Factors

0 10 20 30 40 50 60

ModeMass (g/kg Fuel)

NOx 8 46 6 43 5 44 5 44 4 39 9 45 6 43 7 42 4 41 3 39 CR 3kft CR L 3kft CR 4kft CR L 4kft CR 5kft CR L 5kft CR 6kft CR L 6kft CR 7kft CR L 7kft CR 3kft CR L 3kft CR 4kft CR L 4kft CR 5kft CR L 5kft CR 6kft CR L 6kft CR 7kft CR L 7kft

Figure 15: Example of NO x emission factors, measured in-flight during cruise between 3000 and 7000ft pressure altitude and at about 65% of maximum propeller power. The measurements have been repeated between cruise “full rich” (indicated with CR, low NO x ) and cruise peak EGT mixture (indicated with CR L, high NO x ). At “full rich”, NO x emission factors decrease with increasing altitude. The measurement also shows reproducib ility of the results (Example HB-EYS).
Generally, “old tech” engines will produce between 30 and 40 g NO x per kg fuel near “EGT peak” conditions during cruise.

CO Emission Factors

0 200 400 600 800 1000 1200

ModeMass (g/kg Fuel)

CO 799 128 818 160 956 142 982 147 978 166 746 94 839 140 850 132 963 138 1013 144 CR 3kft CR L 3kft CR 4kft CR L 4kft CR 5kft CR L 5kft CR 6kft CR L 6kft CR 7kft CR L 7kft CR 3kft CR L 3kft CR 4kft CR L 4kft CR 5kft CR L 5kft CR 6kft CR L 6kft CR 7kft CR L 7kftReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Figure 16: Example of CO emission factors, measured in-flight during cruise between 3000 and 7000ft pressure altitude and at about 65% of maximu m propeller power. The measurements have been repeated during cruise “full rich” (indicated with CR, low NO x ) and cruise peak EGT mixture (indicated with CR L, high NO x ). At “full rich”, CO emission factors in crease with increasing altitude. The measurement also shows reproducibility of the results (Example HB-EYS).
Generally, “old tech” engines will produce around 2 00 g CO per kg fuel near “EGT peak” conditions during cruise.

HC Emission Factors

0 5 10 15 20 25

ModeMass (g/kg Fuel)

HC NDIR 13 5 14 3 16 5 16 6 21 5 13 3 14 5 16 6 16 5 19 4 CR 3kft CR L 3kft CR 4kft CR L 4kft CR 5kft CR L 5kft CR 6kft CR L 6kft CR 7kft CR L 7kft CR 3kft CR L 3kft CR 4kft CR L 4kft CR 5kft CR L 5kft CR 6kft CR L 6kft CR 7kft CR L 7kft

Figure 17: Example of HC emission factors, measured in-flight during cruise between 3000 and 7000ft pressure altitude and at about 65% of maximu m propeller power. The measurements have been repeated during cruise “full rich” (indicated with CR, low NO x ) and cruise peak EGT mixture (indicated with CR L, high NO x ). At “full rich”, HC emission factors in crease with increasing altitude. The measurement also shows reproducibility of the results (Example HB-EYS).

Generally, “old tech” engines will produce between 6 and 12 g HC per kg fuel near “EGT peak” conditions during cruise.

Based on the measurement of two typical “old tech” aircraft gasoline piston engines (150 and 180HP) the following soot emission factors fo r cruise are suggested (Appendix 4):
Soot Emission Factors (mg soot / kg fuel) Fuel CR AVGAS 100LL (leaded) 40 AVGAS 91/96UL (unleaded) 1

c) Emissions for aerodrome circ uits (“old tech” engines)
A circuit is a flight pattern that is flown at an ai rport e.g. for aircraft doing a sequence of landings for training purposes. A high percentage of piston engine aircraft are flying in aerodrome circuit patterns, because those aircraft are often used for pilot basic training and education.
For a typical 4 seat piston engine aircraft, circuit emissions for low level circuits (1500 ft PA) and high level circuits (5600ft PA, with mixture adjustment) are given in tables 1 and 2 (from Appendix 2, section 3 g). For a high performance single engine piston aircraft, sug gested mean values are given in table 3.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Normally, for CO 2 emissions calculation, complete combustion is assumed, which means to multiply the kg fuel by 3.17 to get kg of CO 2 (section 2.2.1.c). As shown befo re, “old tech” piston engine have an extremely incomplete combustion during circuit flyi ng. In Tables 1 and 2, this has been taken into account with a lower value for CO 2 emissions. So it is possible to sum up all emissions of different species to get the total emissions.
However, in emissions inventory work, the general principle is to calculate the mass of CO 2 (and H 2 O) as if they were resulting from complete combustion. The pollutants have to be seen as part of CO 2 and H 2 O mass emissions. This makes a certain sense in the context of climate impact assessments, because most CO and HC pollu tants will later be transformed in CO 2 and H 2 O after being released into the atmosphere.

Tables 1 and 2: Circuit emissions for a typical 4 seat single engine piston aircraft (180HP) . (Appendix 2, section 3 g). Please note: CO 2 emissions have been indicated here as measured directly in the exhaust gas (see text above for explanation).

Total circuit emissions (taxi-in, 1 circuit, taxi-out) Elevation fuel (kg) CO (g) HC (g) NOx (g) CO2 (kg) H20 (kg) lead (g) 2000ft 2.83 3305 73 3 5.66 3.40 2.25 5600ft (Samedan) 2.76 2562 67 8 5.51 3.31 2.19
Total circuit emissions (1 circuit without taxi) Elevation fuel (kg) CO (g) HC (g) NOx (g) CO2 (kg) H20 (kg) lead (g) 2000ft 1.90 2200 45 3 3.79 2.28 1.51 5600ft (Samedan) 1.82 1898 44 5 3.65 2.19 1.45

Table 3: Circuit emissions for a typical high performance single engine piston aircraft (300HP)
, fitted with automatic mixture adjustment (best power mixture). (Appendix 2, section 5 h). Please note: CO 2 emissions have been indicated here as measured di rectly in the exhaust gas (see text above for explanation). TCM IO-550 B fuel (kg) CO (g) HC (g) NOx (g) CO2 (kg) H20 (kg) lead (g) 1 Aerodrome circuit 3.9 3300 60 22 7.8 4.6 3.1

d) Emissions for landing and take-off cycle
Emissions in the landing and take-off cycle (LTO) are based on the suggestions of section 2.1.2 and on the data contained in the i ndividual FOCA engine data sheets.

Table 4: LTO fuel and emissions for a typical microlight aircraft (S witzerland: Ecolight) , if fitted with a four stroke engine. Note: No lead and no bromide emissions. The soot value is estimated. ECOLIGHT (MICROLIGHT 4 - STROKE) Fuel (kg) HC (g) CO (g) NOx (g) Soot (g) Lead (g) LTO TOTAL FUEL (kg) or EMISSIONS (g) 1.4 47 940 33 0.002 0.0

Table 5: LTO fuel and emissions for a typical flying school single engine piston aircraft (150HP)

. The soot value is estimated.

SINGLE EGINE PISTON AIRCRAFT 150HP Fuel (kg) HC (g) CO (g) NOx (g) Soot (g) Lead (g) LTO TOTAL FUEL (kg) or EMISSIONS (g) 3.2 47 2397 28 0.17 2.5

Table 6: LTO fuel and emissions for a turbo diesel single engine piston aircraft (135HP) . The soot value is estimated.

SINGLE ENGINE TURBO DIESEL 135HP Fuel (kg) HC (g) CO (g) NOx (g) Soot (g) Lead (g) LTO TOTAL FUEL (kg) or EMISSIONS (g) 1.6 5 19 30 0.09 0.0

Table 7: LTO fuel and emissions for a typical 4 seat single engine piston aircraft (180HP) . The soot value is estimated.
SINGLE EGINE PISTON AIRCRAFT 180HP Fuel (kg) HC (g) CO (g) NOx (g) Soot (g) Lead (g) LTO TOTAL FUEL (kg) or EMISSIONS (g) 3.9 71 3930 12 0.20 3.1Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Table 8: LTO fuel and emissions for a single engine piston high performance aircraft (300HP) . The soot value is estimated.

SINGLE EGINE PISTON AIRCRAFT 300HP Fuel (kg) HC (g) CO (g) NOx (g) Soot (g) Lead (g) LTO TOTAL FUEL (kg) or EMISSIONS (g) 7.5 174 7327 24 0.39 6.0

Table 9: LTO fuel and emissions for a twin engine piston high performance aircraft (2 x 325HP)

. The soot value is estimated.

TWIN EGINE PISTON AIRCRAFT 2 X 325HP Fuel (kg) HC (g) CO (g) NOx (g) Soot (g) Lead (g) LTO TOTAL FUEL (kg) or EMISSIONS (g) 21.6 244 19330 46 1.12 17.2

e) Emissions for cruise
The tables below show fuel consumption (in kg) and gaseous pollutants mass emissions for cruiseduring one hour flight. The cruise setting has been chosen according to engine technology as described in Appendix 3.
Table 10: One hour fuel and emissions for a typical microlight aircraft (Switzerland: Ecolight) , if fitted with a four stroke engine. Note: No lead and no bromide emissions. The soot value is estimated. Ecolight Aircraft (Microlight 4-Stroke) Fuel (kg) HC (g) CO (g) NOx (g) Soot (g) Lead (g) CRUISE 1HOUR FUEL (kg) or EMISSIONS (g) 8.7 67 1090 243 0.009 0.0

Table 11: One hour fuel and emissions for a typical flying school single engine piston aircraft (150HP) . The soot value is estimated.
SINGLE ENGINE PISTON AIRCRAFT 150HP Fuel (kg) HC (g) CO (g) NOx (g) Soot (g) Lead (g) CRUISE 1HOUR FUEL (kg) or EMISSIONS (g) 20.9 243 8557 772 1.09 16.6

Table 12: One hour fuel and emissions for a turbodiesel single engine piston aircraft (135HP) . The soot value is estimated.
SINGLE ENGINE TURBO DIESEL 135HP Fuel (kg) HC (g) CO (g) NOx (g) Soot (g) Lead (g) CRUISE 1HOUR FUEL (kg) or EMISSIONS (g) 14.1 22 91 373 0.8 0.0

Table 13: One hour fuel and emissions for a typical 4 seat single engine piston aircraft (180HP)

. The soot value is estimated.
SINGLE ENGINE PISTON AIRCRAFT 180HP Fuel (kg) HC (g) CO (g) NOx (g) Soot (g) Lead (g) CRUISE 1HOUR FUEL (kg) or EMISSIONS (g) 23.0 197 6743 903 1.20 18.3

Table 14: One hour fuel and emissions for a single engine piston high performance aircraft (300HP) . The soot value is estimated.

SINGLE ENGINE PISTON AIRCRAFT 300HP Fuel (kg) HC (g) CO (g) NOx (g) Soot (g) Lead (g) CRUISE 1HOUR FUEL (kg) or EMISSIONS (g) 49.7 268 23490 1149 2.58 39.5

Table 15: One hour fuel and emissions for a twin engine piston high performance aircraft (2 x 325HP) . The soot value is estimated.
TWIN ENGINE PISTON AIRCRAFT 2 x 325HP Fuel (kg) HC (g) CO (g) NOx (g) Soot (g) Lead (g) CRUISE 1HOUR FUEL (kg) or EMISSIONS (g) 106.0 766 60088 1648 5.51 84.2

f) Emissions of modern turbo diesel engines – a comparison
By design, diesel engines are lean burn engines, wo rking with a lot of excess air (= a lot of excess oxygen)! The TAE-125-01 Centurion 1.7 engine, which FOCA has measured, had a minimal λ of at least 1.3. In every continuous operating condition (take-off, climb, cruise, approach), the FADEC controlled engine is running lean. With section 2.2.2 f) it is directly understandable, what this means in terms of gaseous emissions: Emissions are minimal in comparison to “old tech” gasoline pistonReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern engines of the same power. Depending on the oper ating conditions, the emissions of the diesel can be a factor of 100 lower, compared to “old tech”! (See tables 6 and 12, figures 18 and 19).



## Total gaseous pollutants in a landing and take-off cycle

0 500 1000 1500 2000 2500 3000

Conv. Piston (Lyc O-320) Diesel (TAE-125) Ecolight (Rotax 912)Sum of pollutants (g)

Figure 18: Sum of gaseous emissions during a la nding and take-off cycle, based on FOCA measurements, for a conventional “old tech”, a turbo diesel of similar power and a four stroke microlight engine (Swiss microlight = Ecolight).



## Total gaseous pollutants for a 1 hour cruise

0 2000 4000 6000 8000 10000 12000

Conv. Piston (Lyc O-320) Diesel (TAE-125) Ecolight (Rotax 912)Sum of pollutants (g)

Figure 19: Sum of gaseous emissions during one hour cruise, based on FOCA measurements, for aconventional “old tech”, a turbodiesel of similar power and a four stroke microlight engine (Swiss microlight = Ecolight).

Particle Emissions: At approach (full rich), the mean diameter of emitted particles from an “old tech”engine (an aviation gasoline engine) was around 100 nm and the concentration around 10 million nonvolatile particles in 1 cubic-centimetre (cm 3 ) of exhaust air. This is very similar to a diesel engine without particle filter (see section 2.2.3 a). From present knowledge it is concluded that the si ze, number and mass of emitted particles from the measured turbo diesel engine is not worse than with the rich burn gasoline aircraft piston engine, using leaded fuel. However, the chemical composition of the particles can be different with possibly different health effects, if particles are directly inhaled.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern g) Contribution of piston engines to total aviation emissions
FOCA is providing aircraft emissions data to exte rnal bodies e.g. for environmental impact assessments. FOCA is legally bound to calculate annual em issions inventories based on different principles, and has developed advanced models, taking every aircraft movement and destination into account, with actual flying engines .
One of the models calculates the fuel (CO 2 ) and emissions for all flights from A to B in Switzerland and all flights from A in Switzerland to the first des tination B abroad during one year. This modelling corresponds approximately to the fuel sold in Switzerland during one year, which is used as a quality control for the bottom up calculated fuel consumption. This model has been used for the comparison below.

For total CO 2 emissions, based on the fuel sold, no mode lling would be necessary, as for aviation fuel, every kg of fuel translates approximately into 3.15 kg CO 2 (This is the value for jet fuel, not for AVGAS). Pollutants emissions depend on engine technol ogy and therefore on the actual engines that are flying. From point of view of fuel burn (CO 2 ), piston engines can be completely neglected. In Switzerland, AVGAS consumption is lower than fuel cons umption for gardening (off road sector). Even in comparison with jet fuel only, the AVGAS consumption is not significant (see below). But from point of view of pollutants emissions, for the first time, FOCA was able to generate a clea r picture of the contribution from aircraft piston engines to to tal aviation emissions in Switzerland.
The results of pollutants mass emissions have be en generated based on the computation of around 700’000 flight records of the year 2004, using actu al engine data as far as possible for all operations that took place in Switzerland during that year.
Piston aircraft emissions have the following shares on civil aviation emissions in Switzerland:

• Less than 1% share on total aviation fuel and CO 2

• 1% share on NO x

• 10% share on HC

• 40% share on CO

• 100% share on lead and bromides (the only lead source!)*

* about 5 metric tons of lead and a similar amo unt of bromides per year in Switzerland



### 2.3 Optimization of fu el burn and emissions
2.3.1 “Old tech” gasoline engine s a) Use of unleaded AVGAS
FOCA and DLR measurements have proven a significant reduction of gasoline piston aircraft emissions by use of the unleaded Swedish AVGAS 91/96 UL . Besides this, the fuel meets the same aviation standard as the leaded AVGAS. The engine manufacturer Textron Lycoming has included AVGAS 91/96UL as an approved alternate aviation gasoline fo r a large number of its engines already since 1995. The engines with type numbers are listed in se rvice instruction No. SI 1070. Bombardier-Rotax explicitly recommends the use of this fuel for its engines.

b) Power setting, choice of speed and altitude for lowest possible CO 2 emissions in cruise
Lowest possible CO 2 emissions will be the resu lt of lowest possible fuel burn (section 2.2.1 c). If CO 2 emissions shall be minimized, a mission has theref ore to be optimized for best range. In order to find an optimal speed and altitude for best range in cruise , a theoretical approach is outlined below. Please note that distances, speeds and forces are in fact ve ctors. Because of paralle l vector situations, the notation of vectors is simplified with the size of the scalar.

Definition of terms for theoretical considerations:Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern ) 5 ( ) 3 ( ) 2 ( ) 1 (

n consumptio fuel specific throttle) full at engine (from power available (4) airspeed true thrust required airframe) (for power required power engine fuelmass distance range specific airspeed true time fuelmass fuelflow

P t m P t m

P FF SFC P TAS F P P FF TAS

t m

t d

m d S TAS and t m FF

f f avail req req f f R f

⋅ = = = = = ⋅ = ⋅ = = = = = = = = = = = =

The speed for best range (v _best_range ) is the speed, where the ratio between forward speed (a true air speed TAS ) and the fuel flow ( FF ) is the best possible (equation 3).

The term TAS : FF is called specific range. The specific range for a given aircraft depends on

• power management

• cleanness of the airframe

• aircraft mass

• density altitude

At v _best_range , the specific range is highest.

How can v _best_range be found?
One practical solution is the per manent automatic computing of TAS : FF (or better: Ground Speed : FF
, which takes wind into account). This can be done wi th a fuel flow measurement unit, which is coupled to GPS and constantly provides the nautical miles (N M) per fuel ratio. With experience, the NM per fuel ratio can be maximized, adjusting engine power and altitude accordingly (therefore Ground Speed) during flight.
Theoretical approach:
For the usual power range of an aircraft piston engine, the fuel flow is proportional to the (propellershaft) power P avail . With (5), the fuel flow can be written as:

) 6 ( P SFC P P FF FF

⋅ = ⋅ =

Equation (6) in (3) gives the following specific range formula:

) 7 ( P SF C

TAS S R

⋅ =

The term SFC describes engine resp. propulsion efficiency. The term TAS : P req is an expression for the aerodynamic efficiency of the airframe. More precisely, the maximum sp ecific range will be obtained at highest TAS with lowest SFC and minimum required engine power.

) 8 ( max. max.

req R P SFC TAS S

⋅ =

In order to make things easier, the considerations are made step by step:
1) Looking at aerodynamic efficiency and airc raft mass (keeping propulsion efficiency constant) 2) Looking at propulsion efficiency alone 3) Altitude considerations 4) Summary and “Rules of Thumb”Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 1) Aerodynamic efficiency term, with equation (4)

) 9 ( 1

req req req F TAS F TAS P TAS

=

⋅ =

Equation (9) expresses the fact that aerodynamic efficiency is best, if the required thrust is least. In steady state conditions, level flight at constant s peed, the required thrust exactly compensates drag. Therefore, the number of Newtons for the required thrust equals the number of Newtons of the drag. Hence, for best aerodynamic efficiency, drag must be minimal. Besides others, the drag of a given aircraft is dependent on the aircraft mass. During crui se, the aircraft burns fuel and gets lighter, which reduces the mass, therefore reduce s the necessary lift (reduces the li ft coefficient) and the resulting drag.
From the lift and drag equations (which we are not wr iting down here), it follows that the minimum drag occurs at the maximum lift-to-drag ratio. The true air speed for minimum drag, v min_drag , , can be found (theoretically) by using the function of required power to fly at a certain TAS for a given aircraft and
mass:

Figure 20: Required power for a given aircraft in function of TAS for two different aircraft masses. The highest possible value for equation (9) is given with the tangent from the origin to the power required curve. This represents the minimum for P req : TAS which is the same as the maximum of TAS : P req . The corresponding speed for minimum drag is v _min_drag . The two power curves have been plotted based on a generic airframe. The tangent in the figure shows the example for v _min_drag determination in the lower
mass case.

Figure 21: Required power for a given aircraft in function of TAS for two different aircraft masses. With increasing mass, v _min_drag increases.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern • For best range (at constant SFC), v _best_range is equal to v _min_drag .
• With decreasing aircraft weight, v _min_drag decreases.

• With headwind, v _min_drag increases. (The origin of the tangent in figure 20 moves to the right.)

• v _min_drag is a very low cruising speed compared to “conventional” cruising speeds.

• Drag reduction in general is not only achieved by approaching v _min_drag , but also by cleaning the airframe and the propeller from insects and dirt, reducing edges between engine cowling and airframe, etc.

2) Propulsion efficiency
In general, aircraft piston engines will run more efficiently ( SFC gets smaller, improves):

• If the required power to fly at a certain TAS is generated with the throttle fully open.

• If engine RPM are as low as possible to generate the required power.

• If the engine runs with more than 40% and le ss than 70% of the maximum sea level power.

• If the air/fuel mixture is properly adjusted (summary in next section c).
At low engine RPM, cylinder charge with air/fuel mixt ure is better and there are less friction losses. At full throttle, the intake system works more efficiently . However, there is a lower limit for efficient engine power generation, as well.
Low engine RPM can be achieved with a variable pitch pr opeller. In fact, the propeller efficiency of a variable pitch propeller is very good at low RPM, wh ich can combine to a good efficiency of the whole propulsion system at relatively low RPM.
Output of the required power at low RPM needs rela tively higher Manifold Pressure (MAP), respectively torque. For many engines, the MAP (in InHg ) must not exceed engine RPM/100. The limitations are given by engine manufacturers and/or stated in the AFM/EOM and must be known.
Apart from a better achievable SFC at lowered RPM (not lowest po wer), the propeller noise can be significantly reduced. A drop of only 100 RPM will reduce the prope ller tip mach number with an impressively positive effect on noise reduction. This is an environmental win-win situation (noise and emission reduction).
For a fixed pitch propeller aircraft, to fly on lowest po ssible RPM is normally not feasible. The effects depend on the chosen fixed propeller pitch and are therefore extremely aircraft dependent.

3) Altitude considerations
Before talking about altitude effects, it is worth understanding, that the speed indicator in most piston engine aircraft is essentially a pressure gauge, calibrated in speed units. The speed is called “Indicated Air Speed” IAS . At sea level standard conditions IAS will equal TAS

. TAS is the only speed in the
narrow sense.

• With increasing altitude, IAS will be less than TAS . If IAS is kept constant during climb, TAS will increase.

• The dynamic pressure used for moving the needle of the speed indicator is the same as the dynamic pressure in the drag formula. Therefore,

• if IAS is kept constant during climb, the drag will remain the same, but TAS will increase. From equation (4) follows, that the required power increases.

• If TAS shall be kept constant with increasing altitude, IAS has to be reduced. At higher altitude, the drag and the required power will then be less.
With increasing density altitude, normally aspirated piston engines lose power, due to the lower oxygen partial pressure. Flying at high density altitudes can reduce the available power at full throttle down to 55% or even below. With medium available pow er at full throttle, properly mixed and at reduced RPM, the engine is at best SFC. Desp ite lower drag and higher achievable TAS at higher altitude, the relatively low avail able power (around 50%) holds the TAS at a relatively low level, not very far above v _min_drag . This means that the airframe is near to its best aerodynamic efficiency. Both effects, good SFC and TAS near v _min_drag combine to best specific range.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern During cruise, the aircraft gets lighter by fuel burn. Figure 22 suggests reducing TAS accordingly. This can be done by successively climbing higher, as the loss of power will eventually reduce TAS , despite a lower drag at higher altitude.
In turbocharged engines, at higher altitude, a relatively high air pressure (enough oxygen per volume) can be maintained in the manifold. For turbocharg ed engines, the altitude for best specific range could be further increased compared to the normally aspirated engine, because the engine provides the required power at higher altitude. The lower ambi ent air density causes less drag, with the effect of a higher achievable TAS , which increases specific range (equations 4 and 8).
High cruising altitude does not necessa rily result in best specific range for a piston engine aircraft. The fuel for a climb to higher altitudes and the wi nd components have to be taken into account. Additionally, the SFC of the piston engine is not very altitude and speed dependent, compared to a jet engine. Therefore, high specific r ange can be obtained also at lower altitudes with sufficient power reduction at maximum allowed MAP and low RPM (around 50% of maximum sea level power), which results in a TAS not very far above v _min_drag High cruising altitude does not necessa rily result in best specific range for a piston engine aircraft. The fuel for a climb to higher altitudes and the wi nd components have to be taken into account. Additionally, the SFC of the piston engine is not very altitude and speed dependent, compared to a jet engine. Therefore, high specific range can be obtained with sufficient power reduction at maximum allowed MAP and low RPM, around 50% of maximum sea level power, which results in a TAS not very far above v _min_drag 4) Summary and “Rules of Thumb”
The speed for best range is not very far above v _min_drag. . In any case, the AFM has to be consulted. Additionally, the following “rules of thumb” may be considered:

The least CO 2 emissions during cruise may be achievable with:

• v _best_range (no wind) = TAS for best rate of climb + 15%

• v _best_range + 1/4 of head wind component (for headwind)

• v _best_range – 1/5 of tail wind component (for tailwind)

• v _best_range – 4% for every 100 kg below MTOM

• Required power not below 45% and seldom above 55%

• Required power at lowest possible RPM with highest allowed MAP

• Proper mixture adjustment (High contribution, Appendix 2, summary in section c below)Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern ”Holding position” during flight
If an aircraft has to hold position during flight (e.g. during an approach), the best range criteria is not important. In this case, the aircraft should burn the fuel at the slowest rate possible, in order to minimize CO 2 emissions. This is a power setting for best endurance . As explained before, the fuel burn for a piston engine is practically proportional to the pow er. The least fuel burn per time can therefore be achieved with a speed that requires the least power to keep the aircraft flying. This speed is at the minimum of the required power:

Figure 22: Determination of speed for maximum endur ance. It is the speed at minimum required power (the lowest point of the curve), shown for two ai rcraft masses. With increasing mass, the speed for maximum endurance increases. The lowest required power equals the lowest energy consumption per time to keep the aircraft flying. The speed where this occurs corresponds to the speed for minimum sink rate with engine off ( v _min_sink ).

Usually, v _min_sink is not directly indicated in a piston engine aircraft AFM. But it is very near v y , the speed for best rate of climb. The best rate of c limb will be achieved at a speed where the difference between available power and required power for the climb will be biggest. Because the required power is lowest at v _min_sink , the best rate of climb will usually be around that speed.

The least CO 2 emissions in a holding may be achieved with:

• Flying slightly higher than or at v y (AFM restrictions may apply)

• Required power at lowest possible RPM with highest allowed MAP

c) Manual mixture management (Climb, Cruise, Descent/Approach)

Climb

• At climb, the engine may be leaned according to AFM to best power if AFM/EOM allows and CHT limits can be maintained. Again, the fuel flow method (as described in section 2.2.2 l) may be useful.
Cruise “rich of EGT peak”

• At cruise, flying slightly “rich of EGT peak” is still better than flying best power or very rich from point of view of emissions, although there will be more NO x emissions. There will be less fuel consumption (less total CO 2 ), less CO and HC emissions and less particle mass emissions.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Cruise at “50°F lean of EGT peak”

• Flying lean would be the optimum from point of vi ew of emissions. With the specific fuel consumption at the minimum for a certain powe r setting, range can be maximized and at the same time, all emissions will be minimized as sh own in section 2.2.2 f). In addition, the engine can run cooler. Minimum requirements for safe engine operation at this condition are considered like: - The engine manual and AFM explicitly describe lean mixture setting as an option. - The engine has a well balanced mixture and temp erature distribution between the different

cylinders.
Descent / Approach

• During descent at a fixed mixer position, the engine will normally get less rich (or leaner) due to increasing air density. If the mixture is set slightly rich before de scent, the cylinders are approaching peak EGT when the aircraft descend s. With a lean setting before descent, the cylinders are approaching lean misfire conditi on and may flame out during descent. Therefore, pilots are told to go to “full rich” for descent or approach. This makes operation simple.

• FOCA measurements have shown that with the si mple “full rich” operation, more fuel per distance is burnt during descent and approach than during cruise! The combination with a very incomplete combustion at “full rich” often leads to higher total emissions during descent than during cruise (Appendix 2).

• Instead of going standard “full ri ch”, the author tested alternativ es: Engine propeller power is down at around 45%. If the mixture is set to 100°F rich of EGT peak (best power, safety margin) just before descent, and if the 100°F during descent are maintained by stepwise enriching the mixture, considerable amounts of fuel and emissions can be saved. The 100°F have proven to be practical also for the case, when a sudden increase of power is required during descent. “Full rich” is set later, at mid downwi nd and checked in the final check, because “full rich” is necessary in the event of a go around.



### 2.3.2 Choice of engine technology

a) FADEC for gasoline engines
In the opinion of the author, certif ied FADEC systems for “old tech” fuel injected aircraft gasoline piston engines are a valuable means of significantly reduci ng emissions (including fuel burn). A FADEC system is able to control the air/fuel mixture of ev ery single cylinder and therefore, the engine can be run lean during cruise.

b) Turbo Diesel engine
At the time of completing this FOCA report, the turbo diesel engine has shown by far the lowest gaseous emissions per unit of power. From point of view of emissions, the turbo diesel technology brings the greatest reduction of aircraft pist on engine emissions. This includes CO 2 and pollutants. From point of view of particle emissions, the turbo diesel is not considered worse than the “old tech” gasoline piston engine, running on AVGAS100LL.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 

## 3. Outlook – planned future work
3.1 Number of measured aircraft piston engines

3.1.1 “Old tech” engines and new engine concepts

Some of the FOCA data are based on the measurem ents of one particular engine of a certain engine type. Significant variations between one and anot her engine of the same type exist and therefore FOCA plans to improve data representation with mo re measurements of different engines of a particular engine type. The database will also be completed with engine emissions data for still missing engines.


### 3.1.2 Modernized “old tech” engines with FADEC
During the last couple of years, options for fuel injected engines have been brought into the market and have been certified for certain airframe/engine combinations. From present knowledge, the author concludes that FADEC equipped aircraft piston engines (with individual cylinder control) can have substantially improved emissions performance. More measurement data are needed.


### 3.2 Unleaded AVGAS

In Europe, AVGAS 100LL is the only leaded fuel in the market. Besides lead-tetraethyl, this fuel contains bromides which are harmful to the stratospheri c ozone layer. The scientific research programme documented in Appendix 4 has revealed that the use of an unleaded fuel like AVGAS 91/96 UL can dramatically improve emissions performance of ex isting aircraft piston engines. Therefore, wheneverfeasible and applicable, FOCA supports the transition from leaded AVGAS to a cleaner unleaded AVGAS for aircraft piston engines. Unfortunately, AVGAS 91/96 UL can not yet replace AVGAS 100LL inany case, due to the slightly lower octane rating. Tested unleaded AVGAS with still better environmental performance than 100LL, lik e type C and G (Appendix 4) are alte rnatives that will be evaluated in the future. Unleaded motor gasoline (MOGAS) has strong limitations for use in aircraft. Existing “old tech” piston engine aircraft designs – if possible at all - require a supplemental type certificat e (STC) to ensure safe operation when using MOGAS. For safety reasons, su ch a STC normally prescribes very low ethanol content. The increasing ethanol content in motor ga soline may lead to difficulties in aircraft MOGAS supply in the future. Besides this, instead of lead components, MOGAS can contain substances, which create a certain risk for contamination of drinking water 7

.

Picture 4: Research on unleaded AVGAS, St. Stephan, Switzerland, May 2006. From left to right: C. Wahl, M. Kapernaum (both DLR), L. Hjelmberg (H jelmco), T. Rindlisbacher, W. Bula (both FOCA)

7 MOGAS sold in Switzerland and analyzed in 2006 contained quite large amounts of MTBE.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 

### 3.3 Emissions data for helicopter turbines and small turbofans
For other engine families, like hel icopter turbines and small jet engines, without an ICAO emissions certification, there is still a lack of emissions data and FOCA plans to work on two respective packages, based on its aviation law (SR 748.0, LFG Art. 58):

• Hel icopter en gine emissions, project HELEN (starting mid 2007)

• S mall tu rbo f an engine emissions, project STUF (planned to start in 2008).
A first feasibility study for application of the FO CA “low cost” measurement system has been done on a typical business jet turbofan in summer 2006. Me asurements of gaseous exhaust components havebeen combined with a sophisticated particle measurement system (as described in Appendix 4, section 4). Measured gaseous emissions have been compared to certification level data kindly provided by the engine manufacturer. The data matched quite nicely.



### 3.4 International activities
Due to environmental legislation of different countrie s, and also to the increase of interest at international level, the improvement of knowledge about non-certified engine emissions data has become more and more important. FOCA is supporting the further development of ICAO guidance material for the calculation of emissions caused by the aviation sector and for calculations in relation to environmental impact assessments.

- END -Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 

## 4. List of acronyms and abbreviations

AFM Airplane Flight Manual AMSL Above mean sea level AP Approach modeASTM American Society for Testing and Materials, one of the largest voluntary standards development organizations in the world AVGAS Aviation gasoline AVGAS 100LL leaded AVGAS with 100/130 aviation octane rating AVGAS 91/96 UL unleaded AVGAS with 91/96 aviation octane rating BHP Brake Horse Power °C Temperature in degrees Celsius CAEP Committee on Aviation Environmental Protection CHT Cylinder head temperature CL Climb mode CLD Chemiluminescence CO Carbon monoxide CO 2 Carbon dioxide CPC Condensation Particle Counter CR Cruise mode CR L Cruise mode with adjusted mixture to lambda = 0.95 CR LL Cruise mode with adjusted mixture to lambda = 1.3 CR R Cruise mode at mixture "full rich" Density Altitude DA Height in the Internationa l Standard Atmosphere at which the prevailing air density occurs. Key parameter for aircraft and engine performance DLR German Aerospace Centre DWD Downwind (part of the approach pattern at the airport) EEPS Engine Exhaust Particle Sizer EF Emission Factor (sometimes also indicated as EI, emission index) EGT Exhaust Gas Temperature ELT Emergency Localizer Transmitter EOM Engine Operating Manual °F Temperature in degrees Farenheit FADEC Full Authority Digital Engine Control FF Fuel Flow FID Flame Ionization Detector Final Final approach (last segment of approach before touchdown) FOCA Federal Office of Civil Avia tion (the Swiss Civil Aviation Authority) ft feet FT Full Throttle GPS Global Positioning System H 2 Hydrogen H 2 O Water(vapour) HBEYS FOCA aircraft Robi n DR400-180 with Lycomi ng O-360 se ries engine HBHFX Aircraft AS 2002 Bravo with Lycoming O-320 series engine HBKEY FOCA aircraft Robin DR400/500 wi th Lycoming IO-360 series engine HBKEZ FOCA aircraft Robin DR400/500 with Lycoming IO-360 series engine HBKIA FOCA aircraft Bonanza A35 with Teledyne Continental IO-550 series engine HBWAD Aircraft Ikarus C22-B with Rotax 912S engine HC (total) hydr ocarbon emissions HC6NDIR NDIR HC reading in Hexane ppm He Helium HP (Propeller) Horsepower ICAO International Civil Aviation Organization InHg Pressure Unit in inches of mercury column, e.g. 23 InHg = 779 hPa ISA International Standard Atmosphere λ Number, expressing how rich or lean an air/fuel mixture is Lambda Number, expressing how rich or lean an air/fuel mixture isLean Air/fuel mixture which is poor in fuel (excess oxygen) in relation to stoichiometric mixture LTO Landing and take-off cycle M Torque MAP Manifold Air PressureReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Mixer Lever in the cockpit to adjust air/fuel mixture Mixture Air/fuel mixture Mode Flight phase and attitude with certain power setting MOGAS Motorcar Gasoline MPH Miles per Hour MTBE Methyl tert-butyl ether N 2 NitrogenNanoparticles Ultra fine combustion particles with diameters between 10 and 500 nanometers NDIR Non-Dispersive Infrared Sensor NO x Nitrogen oxides "Old tech" Market dominant aircraft piston engine concept P Power PM Particle Mass Pressure Altitude PA Height in the Internationa l Standard Atmosphere at which the prevailing air pressure occurs, obtained by setting the subscale of a pressure altimeter to 1013.2 hPa QNH Ambient air pressure corrected to sea level with ISA temperatures Rich Air/fuel mixture which is rich in fuel (oxygen deficiency) in relation to stoichiometric mixture RPM Revolutions per Minute RWY Runway SEKEI Aircraft Piper PA-28 Warrior with Lycoming O-3 20 series engine SMPS Scanning Mobility Particle Sizer STC Supplemental Type Certificate stoichiometric Combustion condition at which the ai r/fuel ratio is such that there is neither an excess of fuel nor of air TA Taxi mode (aircraft taxi out and in at the airport) THC Total hydrocarbon emissions (often simply indicated as HC) TO Take-off mode UV Ultraviolet radiation VFR Visual Flight Rules Vne Never-exceed speedReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 

## 5. Bibliography

1) Bombardier-Rotax, engine test stand data, property of Rotax, 2005
2) Chevron Products Company, Technical Review "aviation fuels", 2000
3) DLR, German Aerospace Centre, Institut e of Combustion Technology, C. Wahl/M. Kapernaum, written and oral communication, 2004 – 2007
4) Hjelmco Oil, Aviation Gasolines, AVGAS 91/96UL description, Edition V, 1997
5) Hjelmco Oil, Aviation Gasolines, turbo fuels & lubricants, Fuel Certificate, 2005
6) HORIBA, Mexa 1170 HFID manual, 2006
7) ICAO Annex 16, volume 2, aircraft emissi ons, second edition, July 1993, amendment 5
8) Intertek Caleb Brett, C-H relation measur ements for test fuels, FOCA property, 2006
9) Kas Thomas, Light Plane Maintenance, 2000, ISBN 0-965196-0-6
10) Porsche, PFM3200, Abgaskonzentrationen, BAZL, 1988
11) Technotest, Stargas 898 manual, 2003
12) Textron-Lycoming, Power Curves O-360 and IO-360 series engines, provided hand written documents
13) TSI Incorporated, SMPS a nd EEPS functional drawings, 2007
14) US EPA, Control of air pollution from aircraft and aircraft engines, federal register, volume 38, number 136, July 17, 1973
15) US FAA, Advisory Circular AC34-1A
16) US FAA, Federal Aviation Engine Emissions Databank, November 26, 1991Federal Department of the Environment, Transport, Energy and Communications DETEC

Federal Office of Civil Aviation FOCA Aviation Policy and Strategy Environmental Affairs



# AIRCRAFT PISTON ENGINE EMISSIONS

Appendix 1: Measurement System

FOCA, CH-3003 Bern

Reference: 0 / 3/33/33-05-003 ECERT Contact person: Theo Rindlisbacher Tel. +41 31 325 93 76, Fax +41 31 325 92 12, theo.rindlisbacher@bazl.admin.ch This document has been released for publication by FOCA, Aviation Policy and Strategy, Director M. Zuckschwerdt, 11.06.2007

33-05-003 Piston Engine Emissions_Swiss FOCA_Appendix1_070605_ritReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 

### Contents Page

a) Minimum requirements met by FOCA low cost gas measurement system 3

b) Measurement Method

c) Measured Gaseous Emissions

d) Ranges

e) Illustration of FOCA low cost gas measurement system 4

f) Measurement systems for total HC measurements (certification standard) 5

g) Measurement systems for comparative gas measurements (certification standard)

h) Measurement system for nanoparticle measurements (Appendix 4) 6Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern a) Minimum requirements that are met by FOCA low cost gas measurement system

- Class 0 of OIML R99 1 - Capable of NO measurements with electrochemical cell - Calibration Intervals three months ore more - Condensation water separation, capable of cold sampling line measurement - Capable of direct λ monitoring - Ambient temperature range of +1 to +40°C - Ambient relative humidity range 0 to 95% - Ambient pressure compensation between 770 and 1030 hPa (for in-flight tests) - Portable, no calibration gases and fuel during operation necessary (for in-flight tests) - Battery power possible (for in-flight tests) - Aviation fuel flow meter FAA TSO/STC approved

FOCA uses Tecnotest S.r.l STARGAS 898 with implemented NO sensor (Andros) and jp fuel scan 450 with corresponding fuel flow transducers.

b) Measurement Method NDIR (Non-dispersive Infrared Spectroscopy) for HC, CO, CO 2 Electrochemical detection for O 2 and NO

c) Measured Gaseous Emissions HC calibrated with propane, results given as ppm n-hexane (see Appendix 4 for corrections to ppmC) CO, CO 2 ; O 2 , NO

d) Ranges Resolution Accuracy CO 0 - 15 Vol% 0.001 0..10 l% +-0.02% abs. / +-3% rel. 10.01..15 % +-5% rel.

CO2 0 - 20 Vol% 0.01 0.00..16.00 % +-0.03% abs. / +-3% rel. 16.01..20.00 % +-5% rel.

HC 0 - 30000 ppm 1 0..2000 ppm +-4ppm abs. / +-3% rel. 2001..15000 ppm +-5% rel. 15001..30000 ppm +-8% rel.

O2 0 - 25 Vol% 0.01 0.00..25. 00 % +-0.1% abs. / +-3% rel.

NO 0 - 5000 ppm 1 0..4000 ppm +-25ppm abs. / +-4% rel. 4001..5000 ppm +-5% rel.



### λ 0.5 - 2.000 0.01 +-0.3% abs. 2

jp fuel flow
0 – 60 GPH 1% +- 1 liter / hour (test result)

1 Organisation Internationale de Métrologie : „Instrum ents de mesure de gaz d’échappement des véhicules“ 2 Roberto Amadasi, Tecnotest S.r.l, Sala Bagaza, ItalyReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern e) Illustration of FOCA low co st gas measurement system

Probe Design

Exhaust In to analyzer

The exhaust probe which goes into the exhaust pipe has a length of 30 cm (left part of the probe). The tip of the probe is closed and has four small holes, drilled sidewards into the probe. Normally, aircraft piston engines have rather short exhaust pipes. Therefore a cooling device as seen on the right hand side is necessary for cooling the exhaust gas in the probe from around 600°C to 200°C measuring temperature.
Gaz Analyzer STARGAS 898, MEXA 1170 HFID, calibration gas and FID operating gas installed in FOCA environmental measurement car 

### Optional RPM

Probe Automobile Gas Analyzer Fuel Flow

Calibration GasReference: 0 / 3/33/33-05-003.022

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FOCA uses HORIBA Model MEXA-1170- HFID (Hot Flame Ionization Dete ctor) for total HC measurements. The MEXA-1170-HFID is a stand-alone total HC analyzer with heated sample line at 191°C. This system is very accurate but not suitable for in -flight tests. It is used for static on ground total HC emission measurements. On ground, FOCA uses both the low cost NDIR HC and the HFID in parallel. However, HC data on FOCA data sheets (and CO, NOx corrections) are solely based on the more accurate HFID measurements.

g) Measurement systems for comparative gas measurements (certification standard)

HORIBA OBS 2200 (provided by HORIBA, not owned by FOCA):
All in one system. Dimensions: 40 x 35 x 50 cm Utilizing HFID for total HC measurement, HCLD (hot chemiluminescence) for NOx measurement, HNDIR (hot NDIR) for CO and CO2 measurement. GPS, Temp./Humidity, Engine Control Unit Interface, pat ented exhaust flow meters, heated sampling line at 191°C. System mass (incl. batteries, calibration and utility gases): 120 kg This system has been used by FOCA in order to com pare in-flight tests results with very sophisticated gas analyzer data. At the same time, the provider was able to demonstrate that its system even works in an aircraft up to 7000ft.

Performance: THC HFID (0 – 100 ~10 000 ppm) NOx HCLD (0 – 100 ~3000 ppm) CO2 HNDIR (0 – 5 ~ 20vol%) CO HNDIR (0 – 0.5 ~ 12vol%)

Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 BernReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Illustration : OBS 2200 pitot exhaust flow meter, ready for in stallation in light aircraft (AS02, HB-HFX) for in-flight measurements (see Appendix 2).

Exhaust flow meter, heated sampling line and installation on backseat of HB-HFX

h) Measurement system for nanoparticle measurements
The measurement system and expertise is provided by German DLR, Institute of Combustion Technology. The 2004 measurement system consists of
- TSITM SMPS (Scanning Mobility Particle Sizer) System - 4.5 meter stainless steel sampling li ne at 150°C, calibrated sampling line loss - Dekati Diluter 1:10
In 2005 the SMPS has been replaced by a TSITM EEPS (Engine Exhaust Particle Sizer), providing fast response number-size distributions (see Appendix 4).33-05-003 Piston Engine Emissions_Swiss FOCA_Appendix2_070605_rit Federal Department of the Environment, Transport, Energy and Communications DETEC

Federal Office of Civil Aviation FOCA Aviation Policy and Strategy Environmental Affairs



# AIRCRAFT PISTON ENGINE EMISSIONS

Appendix 2: In-flight Measurements

FOCA, CH-3003 Bern

Reference: 0 / 3/33/33-05-003 ECERT Contact person: Theo Rindlisbacher Tel. +41 31 325 93 76, Fax +41 31 325 92 12, theo.rindlisbacher@bazl.admin.ch This document has been released for publication by FOCA, Aviation Policy and Strategy, Director M. Zuckschwerdt, 11.06.2007Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 

### Contents Page 1. The first in-flight tests 3 1.a) Preparation of aircraft HBEYS 3 1.b) Calculated emission factors for first test flight with HBEYS 5 1.c) Discussion and general explanations 6

2) Standard Flight Test Programme 7
3) HBEYS (Carburated Engine Lyc O-360 Series) 8 3.a) Results for simulated aerodrome circuits 8 3.b) Discussion 11 3.c) HC emission factors at flight idle 12 3.d) Discussion 13 3.e) Additional high altitude circuit flight testing 14 3.f) Discussion 15 3.g) Inventory: Total emissions in aerodrome circuits at different flight altitudes 15 3.h) Full power and approach power settings 16 3.i) Climb power and approach power settings 18 3.j) Cruise power settings 20

4) HBKEZ (Fuel Injected Engine Lyc IO-360 Series) 22 4.a) Results for simulated aerodrome circuits 25 4.b) Discussion 27 4.c) Full power and approach power settings 27 4.d) Take-off, climb and approach power setti ngs with mixture “full rich” 29 4.e) Discussion 30 4.f) Take-off, climb and approach power settings with mixture adjustment 31 4.g) Discussion 33 4.h) Inventory: Standard flight em ission measurement 33

5) HBKIA (Fuel Injected Engine TCM IO-550 B) 36 5.a) Results for aerodrome circuits 39 5.b) Discussion 43 5.c) Inventory: Total emissions of HBKIA in aerodrome circuits 43 5.d) Discussion 44 5.e) Additional high altitude circuit flight testing 44 5.f) Discussion 46 5.g) Inventory: Total emissions of HBKIA in t he low and high altitude aerodrome circuit 47 5.h) Discussion 47 5.i) Full power settings 47 5.j) Discussion 50 5.k) Climb power settings 50 5.l) Approach power settings 53 5.m) Standard flight profile emission measurement 55 5.n) Discussion 57 5.o) Inventory: Total emissions of HBKIA in standard flight, defined in 5.m) 59 5.p) Emissions summary for a HBKIA mission, defined in 5.m) 64

6) HBHFX (Carburated Engine Lyc O-320 Series) 64 6.a) HBHFX high accuracy in-flight measurements: Installation of OBS2200 64 6.b) Real time emission mass determination during flight 70 6.c) OBS2200 confirms typical emission factors for Lycoming carbureted engines 75 6.d) OBS2200 time trend chart and confirmation of high HC at flight idle 76Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 1. The first in-flight tests
1.a) Preparation of aircraft HBEYS
July 2003: The FOCA measurement system was insta lled in HBEYS for the first time. After successful ground testing, documentation for airworthiness validat ion of such a major aircraft modification (aircraft category “restricted”) was completed.

Picture 1: Electronic RPM and fuel flow Picture 2: Sampling lines in and out installation

Picture 3: Installation of the remote controlled gas analyzer in the luggag e compartment of HBEYS. The exhaust sample flows through the black line to the analyzer. Because of high CO concentrations in the exhaust, all sample gas has to be pumped outside the cabin (white line). Water condensate isseparated from the sample and trapped in a small bottle at the bottom. To check cabin CO concentration level, a CO detector is installed, which is independent from the analyzer. The fuel scan box, which indicates the fuel flow, is placed on the knees of the copilot. The exhaust probe installation has been tested during many hours of ground operation prior to the first flight.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Picture 4: Exhaust probe Picture 5: Cockpit of HBEYS with 12VDC/70W power supply for the gas analyzer on the right.

Picture 6: Taxiing for the first flight Picture 7: Those tapes have proven reliable...
Installation steps HBEYS

1. Mount exhaust probe 2. Mount RPM detector (Engine cowling, electric line) 3. Connect Fuel Scan 4. Remove back seat, ELT OFF during work 5. Fix Stargas in baggage compartment, install H 2 O line 6. ELT ON 7. Install 12DC lines and extern TV-screen 8. Install exhaust sample lines IN and OUT (via fresh air vents on starboard, which are removed) 9. Install lines for thermocouple 10. Scotch all lines (exhaust sampling lines, PET, 12VDC and RPM detector lines)

Operational Changes

Installation moves the centre of gravity aft, whic h has to be considered in „Weight and Balance“

At engine start up there is an additional chec klist for measurement system start up.

If one of the cockpit CO detectors changes the co lour to green or even blue, the canopy must be immediately opened by about 10 cm.

Maximum continuous vertical acceleration is limit ed to +2g. Avoid negative vertical accelerations.

Maximum pressure altitude is limited to 7000 ft AMSL.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Checklist Stargas 898

Preparing for operation Paper roll Check Operation supply switch Chose „Battery“ Robin Checklist Engine in warming up phase Robin Checklist Radio Master ON Main switch Stargas ON External monitor ON Revolution counter Red LED ON Pump In function Menu Pump OFFRevolution counter Green LED ON, if negative: Vary Engine revolutions betw. taxi idle and 2000 RPM Clock Stargas Check Menu Exhaust measurement Standard

Before measurement Warming phase > 30 seconds Pump ON Automatic calibration in function Value for O2 (with probe pipe disconnected) 21%

Other values (with probe pipe disconnected) 0 (HC few ppm)

Fuel Flow in function

1.b) Calculated emission factors for first test flight with HBEYS
All calculations are done according Appendix 5. Abbreviations used in the figures: TO = Take off roll, CL = Climb, CR = Cruise, AP = Approach, L = air fuel mixture manually leaned 3700_6748 = Altitude 3700ft QNH and Density Altitude 6748ft etc.

CO Emission Factors

0 200 400 600 800 1000 1200 1400

ModeMass (g/kg Fuel)

CO 1224 1137 975 279 436 479 1124 1199 TO 3700_6748 CL 4700_7748 CR 5000_7880 CRL 5000_8000 CRL 6000_8880 CRL 6000_8880 CR 6000_8760 AP 3000_5520

Figure 1: CO emission factors for take-off, climb, cruise and approach. TO, CL, CR5000_7748, CR6000_8760 and AP have been flown with air-fuel mi xture “full rich”. CRL has been flown with manually adjusted engine air-fuel mixture.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern HC Emission Factors

0 5 10 15 20 25 30

ModeMass (g/kg Fuel)

HC NDIR 22 21 19 8 10 9 19 28 TO 3700_6748 CL 4700_7748 CR 5000_7880 CRL 5000_8000 CRL 6000_8880 CRL 6000_8880 CR 6000_8760 AP 3000_5520

Figure 2: HC emission factors fo r take-off, climb, cruise and approach. TO, CL, CR5000_7748, CR6000_8760 and AP have been flown with air-fuel mi xture “full rich”. CRL has been flown with manually adjusted air-fuel mixture.

NOx Emission Factors

0 5 10 15 20 25 30 35 40 45 50

ModeMass (g/kg Fuel)

NOx 2 2 6 43 28 27 3 1 TO 3700_6748 CL 4700_7748 CR 5000_7880 CRL 5000_8000 CRL 6000_8880 CRL 6000_8880 CR 6000_8760 AP 3000_5520

Figure 3: NO x emission factors for take -off, climb, cruise and appr oach. TO, CL, CR5000_7748, CR6000_8760 and AP have been flown with air-fuel mi xture “full rich”. CRL has been flown with manually adjusted air-fuel mixture.
1.c) Discussion and general explanations
The engine tested (like the majority of existing airc raft piston engines) is air cooled. Cooling requirements are best met in cruise, when the air flow is rather high and the power is reduced.

Take-off and Climb: At full power and climb power, such e ngines would overheat, if they were operated at high combustion efficiency (at high combus tion temperatures). For that reason, the standard air-fuel mixture ratio is set far on the rich side. Th is means that in the combustion chamber, too much fuel is mixed to the air. The excess fuel takes heat in the process of vaporization and combustion temperatures in the combustion chamber remain low, although the engine produces high power. The system can be described as “internal combustion chamber cooling by using excess fuel”. In that operating condition, the air-fuel mixture setting is normally de scribed as “full rich”. The actual air-fuel mixture compared to the stoichiometric mixture (when o xygen meats exactly the demand for complete combustion) is described with the term “lambda” (see Appendi x 5). It is clear that “full rich” conditions result in very low fuel efficiency and very incomplete combustion. This can be seen in the extraordinary high CO and rather high HC emission factors for take-off and climb power settings.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Manual air/fuel mixture control: Most of these engines do not have an automatic mixture control. For r educed power (normally below 75% maximum brake horse power), the mixture has to be manually set to less rich conditions, according to the f light altitude (density altitude) as described in the engine and aircraft operating manual. In many cases of normal aspirated engines (as with the tested aircraft), the manual mixture adjustment to less richer conditions should start during climb at about 5000ft pressure altitude, because the engine maximum power has fallen to around 75% of maximum sea level brake horse power.

Cruise: During cruise, below 75% of maximum brake horse power, the manual mixture adjustment should normally be done for every flight altitude. During the first test flight, when reaching 5000ft, the pilot established cruise configuration. First, t he mixture has been left at “full rich” position (CR 5000_7880). Then, the pilot adjusted the mixture to less rich conditions:
Setting the air/fuel mixture : This test aircraft (like many other s) does not have exhaust gas temperature gauges, therefore no information about peak ex haust gas (and internal combustion) temperatures (EGT) is available. Therefore the pilot adjusts the mixture with a "rule of thumb": Normally the pilot pulls the mixture lever and leans the mixture until a sl ight RPM drop of the fixed pitch propeller is recognized. At this condition, the engine is running sli ghtly lean. After that, the pilot pushes the mixture lever slightly back (about 1 cm) and the engine is runn ing slightly rich. After a while, the pilot checks cylinder head and oil temperature. The result on em ission factors of the described setting can be seen in CRL 5000_8000. Because of higher combustion effi ciency, CO and HC emission factors are significantly lower. However, with increa sing combustion temperatures, the NO x emission factors drastically increase. This is the classical trade-off, (fuel efficiency versus NO x ) also known from rich burn jet engines.
The same mixture adjustment has been repeated at 6000 ft cruising altitude. From this first test we had the impression that the "rule of thumb" resulted in a richer mixture t han at 5000ft. (CRL 6000_8800) which was confirmed later.
Descent and approach:
During descent, the air/fuel mixture should be enric hed gradually. For simplicity - and to make sure pilots do not forget – the AFM of the test aircraft (and of many similar aircrafts) suggests pushing the mixture lever directly to the “full rich” position. The effect of this operation can be seen in CR 6000_8760, where the mixture has been set to full rich just before descent and during approach (AP 3000_5520). Again, we see very high CO and HC emission factors, resulting from much too rich air/fuel mixture, causing very incomplete combustion.

2) Standard flight test programme
The first flight test had shown the tremendous influenc e of pilot operations on emission factors. A lot of in – flight data would be needed for the development of ground based static test s. For the purpose of calculating emission inventories, the measurement of aerodrome circuits and the study of flight altitude on emissions were necessary.

• Aerodrome circuits (VFR traffic departure and arrival pattern) simulated outside aerodrome airspace, starting at 2000, 4000 and 6000ft. Mixtur e full rich and leaned (standard leaning procedure as described in 1.c)).

• Climb at full power (within permitted engine lim its) with measurements at 3000, 4000, 5000, 6000 and 7000ft. Descent (Approach) at around 45% engine load with measurements at 7000, 6000, 5000, 4000 and 3000 ft. Mixture full rich and leaned (sta ndard leaning procedure as described in 1.c)).

• Climb at reduced power (at around 85% engine load) with measurements at 3000, 4000, 5000, 6000 und 7000f. Mixture full rich and leaned (standard leaning procedure as described in 1.c)).

• Cruise at 3000, 4000, 5000, 6000 und 7000ft between 65 and 75% engine load. Controlled leaning (via emission measurements) and stand ard leaning procedure as described in 1.c).

• Predefined flight profiles.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 3) HBEYS (Carburated Engine Lyc O-360 Series)
3.a) Results for simulated aerodrome circuits, flown at 2000 to 6000ft

CO Emission Factors

0 200 400 600 800 1000 1200 1400

ModeMass (g/kg Fuel)

CO 1237 1204 1208 1164 353 1215 1150 1171 1162 1104 1211 633 1162 Take off

roll Take off vy Take off

curve Downwin d Base Long Final Short Final Take off vy Take off

curve Downwin d Base Long Final Short Final

Figure 4: CO emission factors durin g two aerodrome circuits, starting at 2000ft, downwind at 2800ft. (ECERT 4, HBEYS). The first base leg was measured during po wer adjustments and is not considered valid.

CO Emission Factors

0 200 400 600 800 1000 1200 1400

ModeMass (g/kg Fuel)

CO 1285 1231 1170 1242 1201 200 159 387 478 705 391 118 Take off vy_4000 Take off

curve Downwind _4800 Base Long Final Short Final Take off vy L_4000 Take off curve L Downwind L_4800 Base L Long Final L Short Final L

Figure 5: CO emission factors durin g two aerodrome circuits, starting at 4000ft, downwind at 4800ft. The second circuit has been flown with leaned mixtur e as described in 1.c. (ECERT 4.2 HBEYS)

CO Emission Factors

0 200 400 600 800 1000 1200 1400

ModeMass (g/kg Fuel)

CO 1346 1350 1277 707 593 1130 682 524 602 935 991 1201 Take off vy_6000 Take off

curve Downwind _6800 Base Long Final Short Final Take off vy L_6000 Take off curve L Downwind L_6800 Base L Long Final L Short Final L

Figure 6: CO emission factors durin g two aerodrome circuits, starting at 6000ft, downwind at 6800ft. The second circuit has been flown with leaned mi xture as described in 1.c. (ECERT 4. 3 HBEYS) The first base leg was measured during power adjustments and is not considered valid.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern HC Emission Factors

0 5 10 15 20 25 30 35 40 45 50

ModeMass (g/kg Fuel)

HC NDIR 27 23 22 27 15 30 496 22 21 25 27 20 562 Take off

roll Take off vy Take off

curve Downwin d Base Long Final Short Final Take off vy Take off

curve Downwin d Base Long Final Short Final

Figure 7: HC emission factors during two aerodrome circuits, starting at 2000ft, downwind at 2800ft. (ECERT 4, HBEYS). The first base leg was measured during po wer adjustments and is not considered valid.

HC Emission Factors

0 5 10 15 20 25 30 35 40 45 50

ModeMass (g/kg Fuel)

HC NDIR 22 22 25 30 31 9 9 9 11 17 12 6 Take off vy_4000 Take off

curve Downwin d_4800 Base Long Final Short Final Take off vy L_4000 Take off curve L Downwin d L_4800 Base L Long Final L Short Final L

Figure 8: HC emission factors during two aerodrome circuits, starting at 4000ft, downwind at 4800ft. The second circuit has been flown with leaned mixtur e as described in 1.c. (ECERT 4.2, HBE YS)

HC Emission Factors

0 5 10 15 20 25 30 35 40 45 50

ModeMass (g/kg Fuel)

HC NDIR 25 26 32 20 14 1276 13 12 15 21 29 961 Take off vy_6000 Take off

curve Downwin d_6800 Base Long Final Short Final Take off vy L_6000 Take off curve L Downwin d L_6800 Base L Long Final L Short Final L

Figure 9: HC emission factors during two aerodrome circuits, starting at 6000ft, downwind at 6800ft. The second circuit has been flown with leaned mixture as described in 1.c. (ECERT 4.3, HBEYS). The first base leg was measured during power adjustments and is not considered valid.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern NOx Emission Factors

0 10 20 30 40 50 60

ModeMass (g/kg Fuel)

NOx 2222812222121 Take off

roll Take off vy Take off

curve Dow nw ind Base Long Final Short Final Take off vy Take off

curve Dow nw ind Base Long Final Short Final

Figure 10: NO x emission factors during tw o aerodrome circuits, starting at 2000ft, downwind at 2800ft. (ECERT 4, HBEYS). The first base leg was measur ed during power adjustments and is not considered valid.

NOx Emission Factors

0 10 20 30 40 50 60

ModeMass (g/kg Fuel)

NOx 1 2 2 1 1 11 62 36 23 7 6 10 Take off vy_4000 Take off

curve Downwind _4800 Base Long Final Short Final Take off vy L_4000 Take off curve L Downwind L_4800 Base L Long Final L Short Final L

Figure 11: NO x emission factors during two aerodrome circuits , starting at 4000ft, downwind at 4800ft. The second circuit has been flown with leaned mixture as described in 1.c. (ECERT 4.2, HBEYS)

NOx Emission Factors

0 10 20 30 40 50 60

ModeMass (g/kg Fuel)

NOx 1 1 1 4 3 1 14 23 17 4 5 1 Take off vy_6000 Take off

curve Downwind _6800 Base Long Final Short Final Take off vy L_6000 Take off curve L Downwind L_6800 Base L Long Final L Short Final L

Figure 12: NO x emission factors during two aerodrome circuits , starting at 6000ft, downwind at 6800ft. The second circuit has been flown with leaned mixture as described in 1.c. (ECERT 4.3, HBEYS ). The first base leg was measured during power adjustments and is not considered valid.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Lambda

0 0.2 0.4 0.6 0.8

1 1.2

ModeLambda

Lambda 0.68 0.689 0.687 0.713 0.949 0.705 1.463 0.7 0.703 0.732 0.706 0.881 1.637 Take off

roll Take off vy Take off

curve Dow nw ind Base Long Final Short Final Take off vy Take off

curve Dow nw ind Base Long Final Short Final

Figure 13: Lambda (=actual air/fuel ratio to stoichiometric air/f uel ratio) during two circuits, starting at 2000ft, downwind at 2800ft. (ECERT 4, HBEYS). The first base leg was measured during powe r adjustments and is not considered valid.

Lambda

0 0.2 0.4 0.6 0.8

1 1.2

ModeLambda

Lambda 0.663 0.681 0.71 0.693 0.708 1.009 0.981 0.916 0.906 0.853 0.947 1.027 Take off vy Take off

curve Dow nw ind Base Long Final Short Final Take off vy L Take off curve L Dow nw ind L Base L Long Final L Short Final L

Figure 14: Lambda during two circuits, starting at 4000 ft, downwind at 4800ft. The second circuit has been flown with leaned mixture as described in 1.c) (ECERT 4.2, HBEYS).

Lambda

0 0.2 0.4 0.6 0.8

1 1.2

ModeLambda

Lambda 0.642 0.64 0.674 0.856 0.882 1.771 0.841 0.882 0.874 0.79 0.831 1.501 Take off vy Take off

curve Dow nw ind Base Long Final Short Final Take off vy L Take off curve L Dow nw ind L Base L Long Final L Short Final L

Figure 15: Lambda during two circuits, starting at 6000 ft, downwind at 6800ft. The second circuit has been flown with leaned mixture as described in 1.c) (ECERT 4.3, HBEYS). The first base leg was measured during power adjustments and is not considered valid.

3.b) Discussion

CO emission factors remain rather constant at an ex tremely high value of around 1200 g/kg fuel, if the engine is operated at standard “full rich” mixture setting (figure 4). If the circuit is flown at higher altitude, the CO emission factors gets even worse at “full rich” condition. This can also be seen in the lambda value, which drops, the higher the aircraft f lies (minimum lambda at around 0.64, figure 15). At this condition the engine swallows around 36% more fuel mass than necessary for efficient combus-Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern tion. The additional enrichment of the air/fuel mixture with higher altitude can be explained by the fact that the air density becomes smaller with increasi ng altitude, thus the carburetor mixes even less air mass to the fuel than with higher air density at lower altitude. Below 5000ft and at full throttle, the engine air-fuel mixture is generally not adjusted to leaner conditions. For the circuit flying with moderate outside ai r temperature, we decided to start leaning at 4000ft and did not see any engine temperature problems with t hat particular aircraft. The effect of the mixture adjustment can be clearly seen in figure 5. CO emission factors drop by a factor of 2 to 8. However, at a fixed mixture lever setting, the air/fuel mixture seems to become richer again, as power is reduced (see CO emission factor increase on the right of figure 5 between take-off L (=lean) and base L, and lambda drop in figure 14, from take-off L to base L). Comparison of figure 5 and figure 6 shows that the standard “rule of thumb” leaning procedure seems to lead to higher CO emission factors at higher altitu de, thus to richer air/fuel mixture than at 4000ft. This can also be seen in figures 14 and 15, right hand side, with lower values for lambda at 6000ft.
Similar findings result for HC emission factors (figures 7 to 9) with values around 25 g/kg fuel at “full rich” mixture setting and half the value at less rich conditions. However, a dramatic increase in HC emission factors can be seen in short final measurem ents (figures 7 and 9) when the engine throttle is in idle position just before simulated touch down. In figure 8, this effect does not occur. A comparison between fuel flows and RPM in the measurements of figures 7, 8 and 9 showed that the engine was not really at idle setting in the short final at 4000ft (f igure 8). So in fact, this difference between figure 8 and figures 7 and 9 can be explained. The remaining question about the reason for the high HC emission factors at “flight idle” 1 remained unsolved and we decided to investigate this in a separate flight test (see section 3.c).

NO x emission factors behave vice versa to CO and HC as can be seen in figures 10, 11 and 12. At “full rich” mixture, hardly any NO xcan build up. Values are around 1 to 2 g / kg fuel. At less rich conditions, NO x emission factors grow. The highest factor of 62 g/kg fuel was measured during take-off at 4000ft (figure 11). At this high power and hot condi tion, the engine was running nearly stoichiometric (figure 14, take-off L, lambda = 0.981).
From FOCA experience it is well known that aerodrome circuits are mostly flown at mixture setting “full rich”. Exceptions are high (density) altitude ai rports, like Samedan airport in Switzerland (Elevation 5600ft). The effect of mixture adjustment on emission factors (and fuel flow) is very big and therefore we decided to do additional “high” altitude flight tests in Samedan (see section 3.e).

3.c) HC emission factors at flight idle
In order to study the effect of high HC emission factor s in flight idle (figures 7 and 9) we climbed several times to 4500ft and started descent with engine idle at different indicated air speeds: normal finalapproach speed of 115 km/h, and higher speeds of 140, 160 and 180 km/h. Measurements were performed each time when descending through 4000ft.

RPM

0 500 1000 1500 2000 2500 3000

ModeRPM (1/Min.)

RPM 2520 2440 2330 880 1150 1290 1500 Take off vy cruise cruise L idle v=115 idle v=140 idle v=160 idle v=180

Figure 16: Engine RPM (Revolutions per Minute) at take-off and cruise (for comparison) and with engine idle at an indicated airspeed of 115, 140, 160 and 180 km/h. Idle RPM increases with increasing airspeed. (ECERT 4.4)

1 „flight idle“ is used here as short expression for „engine thro ttle fully pulled back to idle position during flight“. This do es not in any case correspond to the term “flight idle” used for turboprops or jet engines.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern HC Emission Factors

0 200 400 600 800 1000 1200 1400 1600 1800 2000

ModeMass (g/kg Fuel)

HC NDIR 21 17 6 812 1115 1275 1716 Take off vy cruise_4300 cruise L_4300 idle v=115 idle v=140 idle v=160 idle v=180

Figure 17: HC emission factors for engine idle at an indi cated airspeed of 115, 140, 160 and 180 km/h (take-off and cruise for comparison and system check). HC emission factors increase drastically with increasing airspeed at engine idle. Note that the absolute scale of HC emission factors at engine flight idle may have a considerable error. (ECERT 4.4)

Lambda

0 0.2 0.4 0.6 0.8

1 1.2 1.4 1.6 1.8

ModeLambda

Lambda 0.696 0.787 0.993 1.426 1.637 1.534 1.616 Take off vy cruise cruise L idle v=115 idle v=140 idle v=160 idle v=180

Figure 18: Lambda for engine idle at an indicated airspeed of 115, 140, 160 and 180 km/h (take-off and cruise for comparison and system check). Lambda increases far above 1 at engine flight idle condition, which shows the presence of excess oxygen in the combustion chambers of the engine, producing very lean conditions. (ECERT 4.4) 3.d) Discussion The findings presented in figure 7 and 9 have been co nfirmed. The flight test showed that HC emission factors increase drastically at flight idle. The effect increases with increasing airspeed (and therefore increasing engine idle RPM). Figure 18 proves the presence of excess oxygen in the combustion chambers of that engine at these flight condition s. Standing on ground, the engine idles at about 650 RPM. At normal approach speed, idle RPM is ar ound 900. The RPM increase comes from the air stream, pushing the propeller to el evated RPM, working like a propeller of a wi ndmill. One possible explanation for the measured effect on HC emission factors might be that the engine “pumps” air through the intake into the combustion chambers due to the elevated RPM from the propeller windmill. At the same time the throttle is nearly closed, theref ore dispersing very little f uel. The little fuel quantity at idle setting is not burnt anymore, which causes extremely high HC emission factors. In fact the engine has practically a “flame out”. This is normally not observed by the pilots because the air stream turns the propeller. From point of view of emissions inventory calculati on, the measured effect can be neglected in simple method or first order calculations. Normally, flight idle occurs only in short final, just before touch down. Duration of this event and fuel flow are both very small, resulting in a small emission change. However, if such an aircraft/engine was operated at long flight idle descents, HC total emissions increase would be considerable.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 3.e) Additional high altitude circ uit flight testing at Samedan Airport (5600ft AMSL), Switzerland
At this high altitude airport, the engine air/fuel mixture should be adjusted to less rich conditions already prior to take-off. We wanted to compare the resulting emission factors when the mixture was adjusted on ground and not during flight, as we had done in the simulated circuits at 6000ft (figures 6, 9, 12 and 15). The “rule of thumb” procedure consisted of - going to full throttle, full rich, static aircraft. - pulling the mixture lever until maximum RPM was noted (with fixed pitch propeller). This can be described as best power mixture, still rich. - Slightly pushing the mixture lever, thus enriching the mixture again (for engine internal cooling reasons at high power).

CO Emission Factors

0 200 400 600 800 1000 1200

ModeMass (g/kg Fuel)

CO 1092 1082 1089 903 1083 1066 1084 1051 778 991 Take Off Roll_5600 Take Off Vy Take Off Turn Downwind_ 6600 Long Final Short Final Take Off Vy_5600 Downwind_ 6600 Long Final Short Final

Figure 19: CO emission factors, measured during two circuits at Samedan airport. (ECERT 13)

HC Emission Factors

0 5 10 15 20 25 30 35 40 45 50

ModeMass (g/kg Fuel)

HC NDIR 22 19 19 25 29 43 25 27 27 39 Take Off Roll_5600 Take Off Vy Take Off Turn Downwind_ 6600 Long Final Short Final Take Off Vy_5600 Downwind_ 6600 Long Final Short Final

Figure 20: HC emission factors, measured during two circuits at Samedan airport. (ECERT 13)Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern NOx Emission Factors

0 10 20 30 40 50 60

ModeMass (g/kg Fuel)

NOx 3333322252 Take Off Roll_5600 Take Off Vy Take Off Turn Dow nw ind_66 00 Long Final Short Final Take Off Vy_5600 Dow nw ind_66 00 Long Final Short Final

Figure 21: NO x emission factors, measured during two circuits at Samedan airport. (ECERT 13)

Lambda

0 0.2 0.4 0.6 0.8

1 1.2

ModeLambda

Lambda 0.733 0.728 0.726 0.788 0.738 0.748 0.726 0.744 0.824 0.706 Take Off Roll Take Off Vy Take Off Turn Dow nw ind Long Final Short Final Take Off Vy Dow nw ind Long Final Short Final

Figure 22: Lambda, measured during two circuits, st arting at 5600ft, downwind at 6600ft. (ECERT 13)
3.f) Discussion
From comparison between figure 22 and figure 15, on e can see that the mixture adjustment which had been prepared on ground was richer than that of t he simulated circuit. But it had the same magnitude as “full rich” mixture on sea level. With the de scribed mixture adjustment, the engine can be brought back to approximately the same rich mixture level which those types of engines normally have at sea level at “full rich” position. If the mixture adjustm ent is done properly at high altitude airports, emission factors will be similar to low altitude airports (figures 19, 20, 21 and 6, 9, 12). However, the fuel flow is lower at high altitude airports (as the power). A compar ison of total emissions in the circuits at different airport levels is done in the next section.

3.g) Inventory: Total emissions in aerodrom e circuits at different flight altitudes
For this comparison of total emissions in the circui ts, we use the mean circuit times measured at Bern airport (LSZB). Table 1 : Mode Times in Mode (s) TAXI OUT 467 TAKE-OFF 20 CLIMB OUT 75 DOWNWIND 90 BASE 105 FINAL 20 TAXI IN 200Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Emission factors were taken from the previously discussed measurements, with “full rich” emission factors for 2000 and 4000ft and less rich conditions fo r 6000ft as presented in section 3.e). Because of very incomplete combustion, the mean emission factor for CO 2 is far below the theoretical 3.17 kg / kg fuel. For this calculation we assume a conservative factor of 2 kg CO 2 / kg fuel and 1.2 kg H 2 O / kg fuel. The lead content in AVGAS 100LL is considered 0.794 g / kg fuel, the fuel density 0.72 kg / liter.

Tables 2 and 3 (emissionsinvent ar.volten.HBEYS_060825_rit):

Total circuit emissions (taxi-in, 1 circuit, taxi-out) Elevation fuel (kg) CO (g) HC (g) NOx (g) CO2 (kg) H20 (kg) lead (g) 2000ft 2.83 3305 73 3 5.66 3.40 2.25 5600ft (Samedan) 2.76 2562 67 8 5.51 3.31 2.19
Total circuit emissions (1 circuit without taxi) Elevation fuel (kg) CO (g) HC (g) NOx (g) CO2 (kg) H20 (kg) lead (g) 2000ft 1.90 2200 45 3 3.79 2.28 1.51 5600ft (Samedan) 1.82 1898 44 5 3.65 2.19 1.45

3.h) Systematic measurements at full power and approach power settings between 3000 and 7000ft flight altitude

Lambda

0 0.2 0.4 0.6 0.8

1 1.2

ModeLambda

Lambda 0.713 0.712 0.692 0.674 0.667 0 .734 0.743 0.74 0.741 0.775 TO 3000ft TO 4000ft TO 5000ft TO 6000ft TO 7000ft AP 7000ft AP 6000ft AP 5000ft AP 4000ft AP 3000ft

Figure 23: Change of lambda during full power climb and approach at 45% engine load. All measurements with mixture “full rich”. Lambda decreases wi th increasing aircraft height. The air/fuel mixture gets richer the higher the aircraft flies. At approach power, the mixture is less rich than at climb full power. (ECERT 8)

CO Emission Factors

0 200 400 600 800 1000 1200 1400

ModeMass (g/kg Fuel)

CO 1127 1130 1191 1249 1267 1096 1073 1106 1111 994 TO 3000ft TO 4000ft TO 5000ft TO 6000ft TO 7000ft AP 7000ft AP 6000ft AP 5000ft AP 4000ft AP 3000ft

Figure 24: Effect on CO emission factor. With increasing height, the CO emission fact or gets even worse (without mixture adjustment). (ECERT 8)Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern HC Emission Factors

0 5 10 15 20 25 30 35 40 45 50

ModeMass (g/kg Fuel)

HC NDIR 14 16 19 20 23 29 28 27 28 25 TO 3000ft TO 4000ft TO 5000ft TO 6000ft TO 7000ft AP 7000ft AP 6000ft AP 5000ft AP 4000ft AP 3000ft

Figure 25: Effect on HC emission factor. With increasing height, the HC emission factor gets even worse (without mixture adjustment). At approach power (45% engine load), HC emission factors are higher than at full power. (ECERT 8)

NOx Emission Factors

0 10 20 30 40 50 60

ModeMass (g/kg Fuel)

NOx 2221111112 TO 3000ft TO 4000ft TO 5000ft TO 6000ft TO 7000ft AP 7000ft AP 6000ft AP 5000ft AP 4000ft AP 3000ft

Figure 26: NO x emission factors are very low due to low inte rnal combustion temperatures. With increasing height, the NO x emission factor decreases (no mixture adjustment). (ECERT 8)

Fuel Flow

0 10 20 30 40 50 60

ModeFuel Flow (l/h)

Fuel 60 58 57 58 55 25 26 26 26 27 TO 3000ft TO 4000ft TO 5000ft TO 6000ft TO 7000ft AP 7000ft AP 6000ft AP 5000ft AP 4000ft AP 3000ft

Figure 27: The fuel flow decreases with increasing height. During descent (45% engine load), the fuel flow has been kept constant. (ECERT 8)Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Manifold Pressure

0 5 10 15 20 25 30

ModeManifold Pressure (in Hg)

Man. Pr. 26.5 25.5 24.5 24 23 15 15 14.5 14.5 14.5 TO 3000ft TO 4000ft TO 5000ft TO 6000ft TO 7000ft AP 7000ft AP 6000ft AP 5000ft AP 4000ft AP 3000ft

Figure 28: Manifold Pressure (air inlet pressure between ca rburetor and cylinder inlet): Manifold pressure is agood indicator for engine power. It drops with increasing altitude due to decreasing ambient air pressure. Accordingly, engine power drops. During descent, engine power has been kept constant. (ECERT 8)

3.i) Systematic measurements at climb power and approach power settings between 3000 and 7000ft flight altitude

Lambda

0 0.2 0.4 0.6 0.8

1 1.2

ModeLambda

Lambda 0.739 0.737 0.715 0.706 0.685 0 .712 0.723 0.743 0.746 0.779 CL 3000ft CL 4000ft CL 5000ft CL 6000ft CL 7000ft AP 7000ft AP 6000ft AP 5000ft AP 4000ft AP 3000ft

Figure 29: Change of lambda during climb at reduced po wer (85% engine load below 4000ft) and descent (45% engine load). All measurements with mixture “full rich”. (ECERT 11)

CO Emission Factors

0 200 400 600 800 1000 1200 1400

ModeMass (g/kg Fuel)

CO 1046 1049 1122 1149 1216 1159 1136 1075 1058 943 CL 3000ft CL 4000ft CL 5000ft CL 6000ft CL 7000ft AP 7000ft AP 6000ft AP 5000ft AP 4000ft AP 3000ft

Figure 30: Effect on CO emission factor. With increasing height, the CO emission fact or gets even worse (without mixture adjustment). (ECERT 11)Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern HC Emission Factors

0 5 10 15 20 25 30 35 40 45 50

ModeMass (g/kg Fuel)

HC NDIR 18 25 21 22 24 33 31 27 25 22 CL 3000ft CL 4000ft CL 5000ft CL 6000ft CL 7000ft AP 7000ft AP 6000ft AP 5000ft AP 4000ft AP 3000ft

Figure 31: Effect on HC emission factor. At approach power, HC emission factors are higher than at climb power (ECERT 11). During descent, approach power has been slightly increased above 45% engine load, compared to ECERT 8 (figure 25). In spite of that, HC emission fact ors for approach show similar values between 22 and 33 g/kg fuel.

NOx Emission Factors

0 10 20 30 40 50 60

ModeMass (g/kg Fuel)

NOx 3322112223 CL 3000ft CL 4000ft CL 5000ft CL 6000ft CL 7000ft AP 7000ft AP 6000ft AP 5000ft AP 4000ft AP 3000ft

Figure 32: NO x emission factors are very low and comparable to figure 26 due to low internal combustion temperatures. With increasing height, the NO x emission factor decreases (without mixture adjustment). (ECERT 11)

Fuel Flow

0 10 20 30 40 50 60

ModeFuel Flow (l/h)

Fuel 53 53 52 50 49 25 24 26 26 27 CL 3000ft CL 4000ft CL 5000ft CL 6000ft CL 7000ft AP 7000ft AP 6000ft AP 5000ft AP 4000ft AP 3000ft

Figure 33: The fuel flow decreases with increasing heigh t. During descent, the fuel flow has slightly increased (ECERT 11). Approach power has been higher at 3000ft than at 7000ft (see figure 34).Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Manifold Pressure

0 5 10 15 20 25 30

ModeManifold Pressure (in Hg)

Man. Pr. 25 23.6 23.1 22.8 21.9 15 14.9 15.5 16.2 17.4 CL 3000ft CL 4000ft CL 5000ft CL 6000ft CL 7000ft AP 7000ft AP 6000ft AP 5000ft AP 4000ft AP 3000ft

Figure 34: 85% engine load could not be kept above 3000ft. With a manifo ld pressure of 23.6 at 4000ft, the engine load was already below 85%. During descent, manifold pressure has not been kept constant. Engine load increased slightly with decreasing altitude. Therefore, the results for descent can not be compared to the results of the previous section one to one. (ECERT 11)
3.j) Systematic measurements for cruise power settings at flight altitudes between 3000 and 7000ft
Cruise power emissions have been measured with two f lights (ECERT 9/10). The same flight test program as described in section 2, has been used for both flights, star ting at 3000ft, mixture “full rich” and 65% of maximum engine fuel flow, followed by a mi xture adjustment to lambda = 1 (stoichiometric). The same procedure has been repeated at 4000, 5000, 6000 and 7000ft.

Lambda

0 0.2 0.4 0.6 0.8

1 1.2

ModeLambda

Lambda 0.812 1.011 0.806 0.999 0.766 1.003 0.759 0.999 0.759 0. 996 0.826 1.034 0.799 1 0.796 1.003 0.763 1.001 0.749 1.003 CR 3kft CR L 3kft CR 4kft CR L 4kft CR 5kft CR L 5kft CR 6kft CR L 6kft CR 7kft CR L 7kft CR 3kft CR L 3kft CR 4kft CR L 4kft CR 5kft CR L 5kft CR 6kft CR L 6kft CR 7kft CR L 7kft

Figure 35: Lambda at “full rich” condition in function of flig ht altitude (e.g. CR 3 kft = cruise at 3000ft full rich), followed by stoichiometric mixture (e.g. CR L 3kft = crui se leaned at 3000ft). Lambda at “full rich” setting is decreasing with altitude, as usual. Lambda for leaned conditi on has been set directly by on line reading of emission concentrations during flight. Theref ore lambda at CR L could be kept constant around 1. (ECERT 9/10)

Fuel Flow

0 10 20 30 40 50 60

ModeFuel Flow (l/h)

Fuel 40 32 40 31 40 31 39 30 38 29 40 31 40 30 39 30 39 31 39 30 CR 3kft CR L 3kft CR 4kft CR L 4kft CR 5kft CR L 5kft CR 6kft CR L 6kft CR 7kft CR L 7kft CR 3kft CR L 3kft CR 4kft CR L 4kft CR 5kft CR L 5kft CR 6kft CR L 6kft CR 7kft CR L 7kft

Figure 36: Reproducible fuel flows in both flights. (ECERT 9/10)Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern CO Emission Factors

0 200 400 600 800 1000 1200

ModeMass (g/kg Fuel)

CO 799 128 818 160 956 142 982 147 978 166 746 94 839 140 850 132 963 138 1013 144 CR 3kft CR L 3kft CR 4kft CR L 4kft CR 5kft CR L 5kft CR 6kft CR L 6kft CR 7kft CR L 7kft CR 3kft CR L 3kft CR 4kft CR L 4kft CR 5kft CR L 5kft CR 6kft CR L 6kft CR 7kft CR L 7kft

Figure 37: CO emission factors are very high and increas ing with altitude without mixture adjustment. At stoichiometric mixture, the values vary around 140 g / kg fuel

. In terms of typical emission measurement accuracies, the values are considered reproducible

. (ECERT 9/10)

HC Emission Factors

0 5 10 15 20 25 30 35 40 45 50

ModeMass (g/kg Fuel)

HC NDIR 13 5 14 3 16 5 16 6 21 5 13 3 14 5 16 6 16 5 19 4 CR 3kft CR L 3kft CR 4kft CR L 4kft CR 5kft CR L 5kft CR 6kft CR L 6kft CR 7kft CR L 7kft CR 3kft CR L 3kft CR 4kft CR L 4kft CR 5kft CR L 5kft CR 6kft CR L 6kft CR 7kft CR L 7kft

Figure 38: HC emission factors increasing with altitude with out mixture adjustment. At st oichiometric mixture, the values vary around 5 g / kg fuel

. In terms of typical emission measurement accuracies, the values are considered reproducible

. (ECERT 9/10)

NOx Emission Factors

0 10 20 30 40 50 60

ModeMass (g/kg Fuel)

NOx 8 46 6 43 5 44 5 44 4 39 9 45 6 43 7 42 4 41 3 39 CR 3kft CR L 3kft CR 4kft CR L 4kft CR 5kft CR L 5kft CR 6kft CR L 6kft CR 7kft CR L 7kft CR 3kft CR L 3kft CR 4kft CR L 4kft CR 5kft CR L 5kft CR 6kft CR L 6kft CR 7kft CR L 7kft

Figure 39: NO x emission factors decreasing with altitude without mixture adjustment. At st oichiometric mixture, the values get high (trade off with CO and HC) and are around 42 g / kg fuel

. In terms of typical emission measurement accuracies, the values are considered reproducible

. (ECERT 9/10)Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 4) HBKEZ (Fuel Injected Engine Lyc IO-360 Series)
Basically, installation of the exhaust emission measurement system in HBKEZ was identical to that of HBEYS. In addition to HBEYS, this aircraft is equipped with a variable pitch, constant speed propeller. At a given propeller RPM, the propeller governor will keep propeller RPM co nstant as long as possible (by automatic pitch adjustment) if engine power or aircraft speed change, thus leading to increased propulsion efficiency compared to the fixed pitch propeller.
Power management complexity is increased, with propulsion power depending on throttle, mixture and propeller pitch adjustment!

Installation of fuel flow transducer 2 for fuel flow measurement:

2 JPI Type 201Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Documentation of sampling probe and measurement system installation:Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 BernReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 4.a) Results for simulated aerodrome circuits, flown at 2000 to 6000ft

CO Emission Factors

0 200 400 600 800 1000 1200 1400

ModeMass (g/kg Fuel)

CO 1273 1319 1345 1381 1370 1172 1355 1377 1394 1407 1420 1199 293 417 479 591 835 1116 TO vy 2300ft _3644 TO curve_ Down wind_ 4272 Base_ Long Final_ 3652 Short Final_ TO vy 4300ft _5524 TO curve_ Down wind_ 6392 Base_ Long Final_ 5652 Short Final_ TO vy 6300ft _7404 TO curve_ Down wind_ 8272 Base_ Long Final_ 7652 Short Final_

Figure 40: Record braking CO emission factors in th ree simulated circuits, starting at 2300ft, 4300ft and 6300ft. The first two circuits were flown with air/fuel mixture “fu ll rich”, the circuit above 6300ft with leaned mixture (right hand side). (ECERT22, HBKEZ)Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern HC Emission Factors

0 5 10 15 20 25 30 35 40 45 50

ModeMass (g/kg Fuel)

HC NDIR 24 24 29 32 30 554 26 27 30 32 34 1616 13 12 12 13 25 1614 TO vy 2300ft TO curve_ Down wind_ Base_ Long Final_ Short Final_ TO vy 4300ft TO curve_ Down wind_ Base_ Long Final_ Short Final_ TO vy 6300ft TO curve_ Down wind_ Base_ Long Final_ Short Final_

Figure 41: HC emission factors in thr ee simulated circuits, starting at 23 00ft, 4300ft and 6300ft. The first two circuits were flown with air/fuel mixture “full rich”, the circuit above 6300ft with leaned mixture (right hand side). Again, the same effect at engine idle, described in sections 3.c/d) can be seen. (ECERT22, HBKEZ)

NOx Emission Factors

0 10 20 30 40 50 60

ModeMass (g/kg Fuel)

NOx 1 1 1 1 1 0 1 1 1 1 1 1 42 33 25 17 7 1 TO vy 2300ft _3644 TO curve_ Down wind_ 4272 Base_ Long Final_ 3652 Short Final_ TO vy 4300ft _5524 TO curve_ Down wind_ 6392 Base_ Long Final_ 5652 Short Final_ TO vy 6300ft _7404 TO curve_ Down wind_ 8272 Base_ Long Final_ 7652 Short Final_

Figure 42: NO x emission factors in three simulated circuits , starting at 2300ft, 4300ft and 6300ft. The first two circuits were flown with air/fuel mixture “full rich”, the circuit above 6300ft with leaned mixture (right hand side). (ECERT22, HBKEZ)

Lambda

0 0.2 0.4 0.6 0.8

1 1.2

ModeLambda

Lambda 0.665 0.649 0.64 0.628 0. 632 0.883 0.636 0.628 0.622 0.618 0.613 1. 066 0.936 0.904 0.889 0.861 0.798 0.909 TO vy 2300ft_ TO curve_ Dow nw ind_ Base_ Long Final_ Short Final_ TO vy 4300ft_ TO curve_ Dow nw ind_ Base_ Long Final_ Short Final_ TO vy 6300ft_ TO curve_ Dow nw ind_ Base_ Long Final_ Short Final_

Figure 43: Lambda values in three simulated circuits, st arting at 2300ft, 4300ft and 6300ft. The first two circuits were flown with air/fuel mixture “full rich”, the circui t above 6300ft with leaned mixture (right hand side). This engine shows even richer combustion (lower lambda) than that of HBEYS at “full rich” setting. (ECERT22, HBKEZ)Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Fuel Flow

0 10 20 30 40 50 60 70 80

ModeFuel Flow (l/h)

Fuel 70 70 44 29 12 6 67 66 44 30 30 5 43 41 29 21 17 5 TO vy 2300ft_ TO curve_ Dow nw ind_ Base_ Long Final_ Short Final_ TO vy 4300ft_ TO curve_ Dow nw ind_ Base_ Long Final_ Short Final_ TO vy 6300ft_ TO curve_ Dow nw ind_ Base_ Long Final_ Short Final_

Figure 44: Fuel flows in three simula ted circuits, starting at 2300ft, 4300ft and 6300ft. The first two circuits were flown with air/fuel mixture “full rich”, the circuit abov e 6300ft with leaned mixture (right hand side). (ECERT22, HBKEZ)

4.b) Discussion
The fuel injected engine of HBKEZ has an even rich er standard air/fuel mixture setting than the carburated one of HBEYS, resulting in CO emission fact ors up to 1400 g / kg fuel. The reason for this extremely rich setting is not clear – engine cylinder and oil temperatures remained far below threshold values for all observed engine operations. However the aircraft AFM describes a leaning procedure, starting already shortly after lift o ff, when take-off power is reduced to climb power. This is rather unique for such engines but makes sense, as c an be seen from the measurements. Mixture adjustment is easily possible to standard values according to AFM with help from fuel flow indicator and exhaust gas temperature control. In a conservative approach, we supposed that pilo ts would not always lean that particular engine on climb. For that reason, the following measur ements were made at mixture “full rich”.

4.c) Systematic measurements at full power and approach power settings between 3000 and 7000ft flight altitude

CO Emission Factors

1280 1300 1320 1340 1360 1380 1400

ModeMass (g/kg Fuel)

CO 1330 1364 1393 1420 1441 1430 1397 1374 1359 TO 3000ft_4124 TO 4000ft_5004 TO 5000ft_5884 TO 6000ft_6764 TO 7000ft_7884 AP 7000ft_7884 AP 6000ft_6884 AP 5000ft_5764 AP 4000ft_4764

Figure 45: CO emission factors during climb at full powe r (TO) from 3000 to 7000ft and during descent from 7000 to 3000ft (AP). The second number after aircraft altit ude in feet is the density altitude. (ECERT27, HBKEZ)Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern HC Emission Factors

0 5 10 15 20 25 30 35 40 45 50

ModeMass (g/kg Fuel)

HC NDIR 32 32 31 32 32 34 32 31 31 TO 3000ft_4124 TO 4000ft_5004 TO 5000ft_5884 TO 6000ft_6764 TO 7000ft_7884 AP 7000ft_7884 AP 6000ft_6884 AP 5000ft_5764 AP 4000ft_4764

Figure 46: HC emission factors during climb at full powe r (TO) from 3000 to 7000ft and during descent from 7000 to 3000ft (AP). With the very rich mixture, they vary around 32 g / kg fuel. (ECERT27, HBKEZ)

NOx Emission Factors

0 10 20 30 40 50 60

ModeMass (g/kg Fuel)

NOx 111001111 TO 3000ft_4124 TO 4000ft_5004 TO 5000ft_5884 TO 6000ft_6764 TO 7000ft_7884 AP 7000ft_7884 AP 6000ft_6884 AP 5000ft_5764 AP 4000ft_4764

Figure 47: NO x emission factors during climb at full power (TO) from 3000 to 7000ft and during descent from 7000 to 3000ft (AP). With the very rich mixture, practically no NO x is built up. (ECERT27, HBKEZ)

Fuel Flow

0 10 20 30 40 50 60 70 80

ModeFuel Flow (l/h)

Fuel 70 69 68 67 66 47 46 45 44 TO 3000ft_ TO 4000ft_ TO 5000ft_ TO 6000ft_ TO 7000ft_ AP 7000ft_ AP 6000ft_ AP 5000ft_ AP 4000ft_

Figure 48: Fuel flow during climb at full power (TO) from 3000 to 7000ft and during descent from 7000 to 3000ft (AP). (ECERT27, HBKEZ)Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Lambda

0.58 0.59 0.6 0.61 0.62 0.63 0.64 0.65

ModeLambda

Lambda 0.644 0.631 0.621 0.612 0. 603 0.609 0.622 0.631 0.635 TO 3000ft_ TO 4000ft_ TO 5000ft_ TO 6000ft_ TO 7000ft_ AP 7000ft_ AP 6000ft_ AP 5000ft_ AP 4000ft_

Figure 49: Lambda during climb at full power (TO) from 3000 to 7000ft and during descent from 7000 to 3000ft (AP). It can be seen, how the engine gets even richer wi thout mixture adjustment dur ing climb. At 7800ft density altitude (TO 7000ft), lambda stays at 0.6 and the engine sw allows 40% more fuel than necessary for efficient combustion. (ECERT27, HBKEZ)
4.d) Systematic measurements at take-off, climb and approach power at 3500ft flight altitude, mixture “full rich”

CO Emission Factors

0 200 400 600 800 1000 1200 1400

ModeMass (g/kg Fuel)

CO 1315 1317 1321 1295 1291 1285 1316 1312 1310 1301 1304 1303 1281 1274 1279 1283 1274 1277 TO 3500ft _2840 TO 3500ft _2840 TO 3500ft _2840 CL 3500ft _2840 CL 3500ft _2840 CL 3500ft _2840 AP 3500ft _2840 AP 3500ft _2840 AP 3500ft _2840 TO 3500ft _2720 TO 3500ft _2720 TO 3500ft _2720 CL 3500ft _2720 CL 3500ft _2720 CL 3500ft _2720 AP 3500ft _2720 AP 3500ft _2720 AP 3500ft _2720

Figure 50: CO emission factors during take-off, climb and approach, when passing 3 500ft (2800ft density altitude.) Two flights at differ ent days. (ECERT48+49, HBKEZ)

HC Emission Factors

0 5 10 15 20 25 30 35 40 45 50

ModeMass (g/kg Fuel)

HC NDIR 25 26 26 25 26 26 28 28 29 24 27 26 27 27 27 29 28 29 TO 3500ft TO 3500ft TO 3500ft CL 3500ft CL 3500ft CL 3500ft AP 3500ft AP 3500ft AP 3500ft TO 3500ft TO 3500ft TO 3500ft CL 3500ft CL 3500ft CL 3500ft AP 3500ft AP 3500ft AP 3500ft

Figure 51: HC emission factors during take-off, climb and approach, when passing 3500 ft (2800ft density altitude.) Two flights at different days. (ECERT48+49, HBKEZ)Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern NOx Emission Factors

0 10 20 30 40 50 60

ModeMass (g/kg Fuel)

NOx 111111111111111111 TO 3500ft _2840 TO 3500ft _2840 TO 3500ft _2840 CL 3500ft _2840 CL 3500ft _2840 CL 3500ft _2840 AP 3500ft _2840 AP 3500ft _2840 AP 3500ft _2840 TO 3500ft _2720 TO 3500ft _2720 TO 3500ft _2720 CL 3500ft _2720 CL 3500ft _2720 CL 3500ft _2720 AP 3500ft _2720 AP 3500ft _2720 AP 3500ft _2720

Figure 52: NO x emission factors during take-off, climb and appr oach, when passing 3500 ft (2800ft density altitude.) Two flights at differ ent days. (ECERT48+49, HBKEZ)

Fuel Flow

0 10 20 30 40 50 60 70 80

ModeFuel Flow (l/h)

Fuel 70 70 70 59 60 59 37 36 35 70 70 70 60 60 60 36 37 37 TO 3500ft_ TO 3500ft_ TO 3500ft_ CL 3500ft_ CL 3500ft_ CL 3500ft_ AP 3500ft_ AP 3500ft_ AP 3500ft_ TO 3500ft_ TO 3500ft_ TO 3500ft_ CL 3500ft_ CL 3500ft_ CL 3500ft_ AP 3500ft_ AP 3500ft_ AP 3500ft_

Figure 53: Fuel flow during take-o ff, climb and approach, w hen passing 3500ft (2800ft density altitude.) Two flights at different da ys. (ECERT48+49, HBKEZ)

Manifold Pressure

0 5 10 15 20 25 30

ModeManifold Pressure (in Hg)

Man. Pr. 26.3 26.3 26.3 25 25 25 17 17 17 26.3 26.2 26.2 25 25 25 16.9 16.9 16.8 TO 3500ft_ TO 3500ft_ TO 3500ft_ CL 3500ft_ CL 3500ft_ CL 3500ft_ AP 3500ft_ AP 3500ft_ AP 3500ft_ TO 3500ft_ TO 3500ft_ TO 3500ft_ CL 3500ft_ CL 3500ft_ CL 3500ft_ AP 3500ft_ AP 3500ft_ AP 3500ft_

Figure 54: Manifold pressure during take-off, climb and approach, when passi ng 3500ft (2800ft density altitude.) Two flights at different days. (ECERT48+49, HBKEZ)

4.e) Discussion
The two measurement series have been made with comparable power settings (figure 54) and fuel flows (figure 53). At the extremely rich air/fuel mi xture condition of that engine, emission factors do not change significantly from one power condition to the other. It can also be seen that the data can beReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern considered reproducible in the context of emi ssion measurements. CO emis sion factors stay around 1300 g/kg fuel, HC emission factors around 26 g/kg fuel and NO x emission factors around 1 g / kg fuel. These are worst case scenario values, as suming that pilots do not lean the engine.

4.f) Systematic measurements at take-off, climb and approach power at 3500ft flight altitude with mixture adjustment according to the aircraft flight manual (AFM).
According to the AFM of HBKEZ , the engine air/fuel mixture should be leaned after obstacle clearance in the following way (normal procedure):
Reduce angle of climb to reach 84 kt Reduce throttle to 25 InHg Reduce propeller RPM to 2500 RPM Mixture: Reduce fuel flow to 12 US gal/h
The mixture setting can be checked with exhaust gas temperature (EGT) and cylinder head temperature (CHT). The obtained mixture setting results in an EGT about 150°F rich of EGT peak, which corresp onds approximately to best power mixture (at sea level). For descent, mixture has to be set to “full rich” again, according to the AFM.

CO Emission Factors

0 200 400 600 800 1000 1200 1400

ModeMass (g/kg Fuel)

CO 1290 1294 1300 584 811 817 1330 1301 1285 1294 1291 TO 3500ft_264 4 TO 3500ft_264 4 TO 3500ft_264 4 CL 3500ft_264 4 CL 3500ft_264 4 CL 3500ft_264 4 AP 3500ft_264 4 AP 3500ft_264 4 AP 3500ft_264 4 AP 3500ft_264 4 AP 3500ft_264 4

Figure 55: CO emission factors when le aning during climb. (ECERT47, HBKEZ)

HC Emission Factors

0 5 10 15 20 25 30 35 40 45 50

ModeMass (g/kg Fuel)

HC NDIR 24 25 24 16 16 15 27 29 28 30 28 TO 3500ft_264 TO 3500ft_264 TO 3500ft_264 CL 3500ft_264 CL 3500ft_264 CL 3500ft_264 AP 3500ft_264 AP 3500ft_264 AP 3500ft_264 AP 3500ft_264 AP 3500ft_264

Figure 56: HC emission factors when leaning during climb. (ECERT47, HBKEZ)Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern NOx Emission Factors

0 10 20 30 40 50 60

ModeMass (g/kg Fuel)

NOx 1 1 1 10 6 6 1 1 1 1 1 TO 3500ft_264 4 TO 3500ft_264 4 TO 3500ft_264 4 CL 3500ft_264 4 CL 3500ft_264 4 CL 3500ft_264 4 AP 3500ft_264 4 AP 3500ft_264 4 AP 3500ft_264 4 AP 3500ft_264 4 AP 3500ft_264 4

Figure 57: NO x emission factors when leaning during climb. (ECERT47, HBKEZ)

Fuel Flow

0 10 20 30 40 50 60 70 80

ModeFuel Flow (l/h)

Fuel 71 71 71 46 48 48 32 35 34 34 33 TO 3500ft_ TO 3500ft_ TO 3500ft_ CL 3500ft_ CL 3500ft_ CL 3500ft_ AP 3500ft_ AP 3500ft_ AP 3500ft_ AP 3500ft_ AP 3500ft_

Figure 58: Fuel flow when leaning dur ing climb. (ECERT47, HBKEZ ) The engine is still runn ing rich all the time, however consuming about 15% less fuel during c limb than at the “full rich” setting (figure 53).

Manifold Pressure

0 5 10 15 20 25 30

ModeManifold Pressure (in Hg)

Man. Pr. 27 26.8 26.8 25 25 25 17 17 17 17 17 TO 3500ft_ TO 3500ft_ TO 3500ft_ CL 3500ft_ CL 3500ft_ CL 3500ft_ AP 3500ft_ AP 3500ft_ AP 3500ft_ AP 3500ft_ AP 3500ft_

Figure 59: Manifold pressure values . (ECERT47, HBKEZ) The throttle setting can be compared to the flights of section 4.d)Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Lambda

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

ModeLambda

Lambda 0.659 0.657 0.656 0.863 0.803 0. 802 0.646 0.656 0.661 0.658 0.66 TO 3500ft_ TO 3500ft_ TO 3500ft_ CL 3500ft_ CL 3500ft_ CL 3500ft_ AP 3500ft_ AP 3500ft_ AP 3500ft_ AP 3500ft_ AP 3500ft_

Figure 60: Lambda values: The leaning procedure in climb according AFM leads to lambda values around 0.85 (ECERT 47, HBKEZ).
4.g) Discussion
The leaning procedure during climb of that particular aircraft/engine combination leads to slightly better combustion and better engine power (lambda around 0.85). At all of those measurements, engine cylinder and oil temperatures were stayi ng far below maximum allowed values. From present experience it is however not fully understood, why the mixture should be immediately set to “full rich” during descent, as described in the AFM. One explanation could be that pilots might forget to gradually enrich the mixture during descent and th erefore are asked to go to “full rich” as a general procedure. Note that during descent, the fuel flow at “full rich” is only 30% below the fuel flow at leaned climb power (figure 58)! The values have shown to be reproducible (see section 4.d).

4.h) Inventory: Standard flight emission measure ment from Bern (LSZB) to Grenchen (LSZG)

What we see in this section is the result of a real measured emission inventory for a half an hour VFR 3 flight from Bern (LSZB) to Grenchen (LSZG) with HBKEZ.

The pilot got the following route briefing:

- Bern outbound route E – Hasle - Direct WIL VOR - Climb to 5500ft QNH 4 and level off - Cruising altitude 5500ft QNH - Grenchen approach Aarwangen, G-E - E altitude 3200ft QNH - RWY 25 in use

The actual take-off mass of HBKEZ was 1040 kg (+- 10 kg).
The picture on the left shows the route flown with HBKEZ on 16 th July 2004 (red line).

3 VFR = Visual Flight Rules 4 QNH = actual barometric air pressure in hPa, calculat ed to sea level & standard atmosphere, used for altimeter settingReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Flight-Profile LSZB - LSZG, HB-KEZ, 16.07.2004

1000 2000 3000 4000 5000 6000 7000

0 5 10 15 20 25 30 35 40 Time (Min)Index

Flightprofile RPM Man. Pressure Fuel Flow LTO 1 LTO 2 CR 1 CR 2 LTO 1 LTO 2 (including all taxi) Cruise (Climb) (Descent)

F igure 61: Altitude profile (dark blue), fuel flow (light blue), engine RPM (violet) and manifold pressure (brown) during flight from Bern to Grenchen. The taxi time which was spent in Bern has been add ed to the end of the flight for calculation purposes. The altitude profile on the left shows the climb phase to 550 0ft. Most of this phase is spent in the LTO 1 (if the upper limit of the LTO is 3000ft AGL). During cruise, the fli ght altitude is kept constant and after 16 minutes flight time, the pilot starts the descent. Looking at the fuel flow: A first significant reduction of fuel flow is obtained when the pilot starts to lean the engine in climb, about two minutes after brak e release (see also section 4.f ). The second reduction appears after top of climb (TOC), when the pilot sets cruise power, cruise pr opeller pitch and adjusts the air/fuel mixture (line CR 1). At top of descent (TOD, line CR 2), power is reduced (manifold pressure is dropping) but the fuel flow is increasing and higher as in cruise until around 24 minutes, wh en power is further reduced. The increasing fuel burn comes from the mixture adjustment, as described in sect ions 4.f/g). At about 23 minut es flight time, at the approach check, the mixture is set to “full rich”. (ECERT 29, HBKEZ)

Cumulative Fuel Consumption

0 2 4 6 8 10 12 14 16

0 5 10 15 20 25 30 35 40 Time (Min)Fuel (kg)

Fuel Consumption LTO 1 LTO2 CR 1 CR 2 Figure 62: Integrated fuel burn over time (ECERT 29, HBKEZ)

Cumulative CO Emissions

0 2000 4000 6000 8000 10000 12000

0 5 10 15 20 25 30 35 40 Time (Min)CO (g)

CO Emissions LTO 1 LTO 2 CR 1 CR 2 Figure 63: Integrated CO emissions over time (ECERT 29, HBKEZ)Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Cumulative HC Emissions

0 50 100 150 200 250 300 350 400

0 5 10 15 20 25 30 35 40 Time (Min)HC (g)

HC Emissions LTO 1 LTO 2 CR 1 CR 2 Figure 64: Integrated HC emissions over time (ECERT 29, HBKEZ)

Cumulative NOx Emissions

0 50 100 150 200 250 300 350

0 5 10 15 20 25 30 35 40 Time (Min)NOx (g)

NOx Emissions LTO 1 LTO 2 CR 1 CR 2 Figure 65: Integrated NO x emissions over time (ECERT 29, HBKEZ)

CO Emission Factor Variation During Flight

0 200 400 600 800 1000 1200 1400 1600

0 5 10 15 20 25 30 35 40 Time (Min)EI CO (g/kg)

EI CO LTO 1 LTO 2 CR 1 CR 2 Figure 66: Variation of CO emission fa ctor over time (ECERT 29, HBKEZ)Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern HC Emission Factor Variation During Flight

0 10 20 30 40 50 60 70 80

0 5 10 15 20 25 30 35 40 Time (Min)EI HC (g/kg)

EI HC LTO 1 LTO 2 CR 1 CR 2 Figure 67: Variation of HC emission fa ctor over time (ECERT 29, HBKEZ)

NOx Emission Factor Variation During Flight

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0

0 5 10 15 20 25 30 35 40 Time (Min)EI NOx (g/kg)

EI NOx LTO 1 LTO 2 CR 1 CR 2 Figure 68: Variation of NO x emission factor over time (ECERT 29, HBKEZ)

5) HBKIA (Fuel Injected Engine TCM IO-550 B)
Basically, installation of the exhaust emission measurement system in HBKI A was similar to that of HBEYS and HBKEZ. As HBKEZ, this aircraft is equipped with a variable pitch, constant speed propeller. At a given propeller RPM, the propeller governor will keep propeller RPM constant as long as possible (by automatic pitch adjustment) if engine power or aircraft speed change, thus leading to increased propulsion efficiency compared to the fixed pitch propeller. The complexity of the aircraft is increased with the relatively high power six cylinder engine, higher speed and retractable gear.
Not many pilots seem to know that this type of engine has auto-leaning capabilities . There is still a manual mixture handle but the fuel pump ha s what appears to be an aneroid that senses changes in ambient pressures. Ambient pressure s are routed to the aneroid through the drain fitting via a bolt hole channel in the pump body. High rp m pressures are set by means of a tapered needle (like those seen on naturally aspirated models) housed in a brass boss on the side of the pump. So in fact, this air cooled engine is always automatically leaned even during climb and therefore engine temperatures should be watched with additional care.
So, this type of engine added a further degree of complexity to representative measurements, because of the auto-leaning effects on emissions whic h could only be measured and “seen” in flight.
In addition to previous flights with HBEYS and HBKEZ, repetitive patterns were fl own by different pilots in order to study the effect on emissions depending on different pilot operations.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Installation of FOCA emissions measurement unit in HBKIA:Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 BernReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 5.a) Results for aerodrome circuits, flown at LSZG (Grenchen Airport, Switzerland)
In Grenchen, high performance single engine piston aircraft like HBKIA have to fly the outer circuit No.1 (see picture). Runway in use during the measurements was 07. Take-offmeasurements took place shortly before liftoff. After departure, the pilot had to fly a slight right turn to avoid Altreu village, for noise abatement. The first climb measurement took place abeam ALTREU, the second (if possible) between Leuzigen and Nennigkofen. The downwind measurement was performed abeam tower (if possible) and the base measurement when crossing theriver. The final measurement took place approximately in the middle between turning final and touch down points. Two sets of circuit patterns have been flown (ECERT 56 and 62), with the same aircraft at the same initial take-off mass and comparable meteorological conditions. But the second set of measurements was flown by a different pilot (ECERT 62).

CO Emission Factors

0 200 400 600 800 1000 1200 1400

ModeMass (g/kg Fuel)

CO 621 713 746 860 844 1167 714 656 782 724 806 698 725 861 887 1301 TO CL CL DWD Base Final TO CL CL DWD Base TO CL DWD Base Final

Figure 69: CO emission factors during three aerodrome circuits (TO = Take off roll, CL = Climb at vy 5 , DWD = downwind). No “Final” measurement at the second circuit. (ECERT 56, HBKIA )

HC Emission Factors

0 5 10 15 20 25

ModeMass (g/kg Fuel)

HC NDIR 23 17 17 9 11 13 21 13 14 8 9 22 16 9 10 18 TO CL CL DWD Base Final TO CL CL DWD Base TO CL DWD Base Final

Figure 70: HC emission factors during three aerodrome ci rcuits (TO = Take off roll, CL = Climb at vy, DWD = downwind). No “Final” measurement at the second circuit. (ECERT 56, HBKIA )

5 Vy = indicated airspeed for best rate of climbReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern NOx Emission Factors

0 2 4 6 8 10 12

ModeMass (g/kg Fuel)

NOx 12 9 7 4 4 2 10 10 3 6 7 8 8 4 5 1 TO CL CL DWD Base Final TO CL CL DWD Base TO CL DWD Base Final

Figure 71: NO x emission factors during three aerodrome circuits (TO = Take off roll, CL = Climb at vy, DWD = downwind). No “Final” measurement at the second circuit. (ECERT 56, HBKIA )

Fuel Flow

0 10 20 30 40 50 60 70 80 90 100

ModeFuel Flow (l/h)

Fuel 91 87 83 58 58 49 91 81 83 64 57 91 83 60 57 44 TO CL CL DWD Base Final TO CL CL DWD Base TO CL DWD Base Final

Figure 72: Fuel flow during three aerodrome circuits (TO = Take off roll, CL = Climb at vy, DWD = downwind). No “Final” measurement at the second circuit. (ECERT 56, HBKIA )

Manifold Pressure

0 5 10 15 20 25 30

ModeManifold Pressure (in Hg)

Man. Pr. 27 27 25.5 20 20 15.5 27 25 25.2 23 19.2 27.2 25.8 20 19 14 TO CL CL DWD Base Final TO CL CL DWD Base TO CL DWD Base Final

Figure 73: Manifold pressure during three aerodrome circui ts (TO = Take off roll, CL = Climb at vy, DWD = downwind). No “Final” measurement at the second circuit. (ECERT 56, HBKIA )Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Lambda

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

ModeLambda

Lambda 0.851 0.826 0.817 0.788 0.792 0. 701 0.828 0.841 0.807 0.83 0.803 0.844 0.829 0.798 0.781 0.656 TO CL CL DWD Base Final TO CL CL DWD Base TO CL DWD Base Final

Figure 74: Lambda during three aerodrome circuits (TO = Ta ke off roll, CL = Climb at vy, DWD = downwind). No “Final” measurement at the second circuit. (ECERT 56, HBKIA )
Second set, flown by different pilot:

CO Emission Factors

0 200 400 600 800 1000 1200 1400

ModeMass (g/kg Fuel)

CO 671 783 876 1165 678 724 945 1115 665 732 1021 982 662 740 1002 1217 TO CL DWD Final TO CL DWD Final TO CL DWD Final TO CL DWD Final

Figure 75: CO emission factors during four aerodrom e circuits (TO = Take off roll, CL = Climb at vy 6 , DWD = downwind), flown with seco nd pilot (ECERT 62, HBKIA )

HC Emission Factors

0 5 10 15 20 25

ModeMass (g/kg Fuel)

HC NDIR 22 18 13 13 23 17 14 14 24 20 13 11 24 19 13 10 TO CL DWD Final TO CL DWD Final TO CL DWD Final TO CL DWD Final

Figure 76: HC emission factors during four aerodrome circui ts (TO = Take off roll, CL = Climb at vy, DWD = downwind), flown with second pilot (ECERT 62, HBKIA)

6 Vy = indicated airspeed for best rate of climbReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern NOx Emission Factors

0 2 4 6 8 10 12

ModeMass (g/kg Fuel)

NOx 11 5 3 3 11 8 3 2 11 8 3 4 11 8 3 2 TO CL DWD Final TO CL DWD Final TO CL DWD Final TO CL DWD Final

Figure 77: NO x emission factors during four aerodrome circuits (TO = Take off roll, CL = Climb at vy, DWD = downwind), flown with seco nd pilot (ECERT 62, HBKIA)

Fuel Flow

0 10 20 30 40 50 60 70 80 90 100

ModeFuel Flow (l/h)

Fuel 93 87 58 53 93 87 57 53 94 88 57 53 94 87 34 33 TO CL DWD Final TO CL DWD Final TO CL DWD Final TO CL DWD Final

Figure 78: Fuel flow during four aerodrome circuits (TO = Take off roll, CL = Climb at vy, DWD = downwind), flown with second pilot (ECERT 62, HBKIA)

Manifold Pressure

0 5 10 15 20 25 30

ModeManifold Pressure (in Hg)

Man. Pr. 27 24.5 19 16 27 26.8 18 15 27.5 26.8 18 17 26.5 26.8 17 15 TO CL DWD Final TO CL DWD Final TO CL DWD Final TO CL DWD Final

Figure 79: Manifold pressure during four aerodrome circui ts (TO = Take off roll, CL = Climb at vy, DWD = downwind), flown with second pilot (ECERT 62, HBKIA)Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Lambda

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

ModeLambda

Lambda 0.839 0.807 0.785 0.701 0.837 0. 822 0.765 0.716 0.839 0.82 0.743 0.757 0.85 0.817 0.749 0.683 TO CL DWD Final TO CL DWD Final TO CL DWD Final TO CL DWD Final

Figure 80: Lambda during four aerodrome circuits (TO = Take off roll, CL = Climb at vy, DWD = downwind), flown with second pilot (ECERT 62, HBKIA)
5.b) Discussion
In contrast to the engines of HBEYS and HBKEZ, the engine of HBKIA is auto- leaned (see 5, Introduction). This can be seen in figures 74 and 80. Lambda values at take-off are around 0.83 to 0.85, significantly higher than the values of the previously measured engines at “full rich” mixture. A lambda value of 0.85 corresponds approximately to best power mixture. However, engine cylinder head temperatures reach easily its limits at this condition and therefore considerable care must be taken, not to exceed engine temperature limits during climb. At low power settings, the auto-lean feature does not seem to have an effect. The engine is running extrem ely rich again (lambda around 0.7), like the previously measured engines at “full rich” mixture adjustment. The second pilot has been flying the circuits very regul arly compared to the first pilot. This can be seen in the variation of the engine manifold pressu re, lambda, fuel flow and emission factors. Due to auto-lean at high power, CO emission factors are lowest and NO x emission factors highest for high power setting (take-off and climb). Interestingly, HC emission factors are highest as well for high power settings. Normally HC correlates to CO an d HC would have been expected to be lowest at high power settings.
5.c) Inventory: Total emissions of HBKIA in aerodrome circui ts and comparison between two pilots
For this comparison of total emissions in the circuits , we used the same mean circuit times as in 3.g) and the data of 5.a). In order to obtain more ge neral results, we used mean FOCA standard times instead of Grenchen circuit times for this comparison.

Table 4 : Mode Times in Mode (s) TAKE-OFF 20 CLIMB OUT 75 DOWNWIND 90 BASE 105 FINAL 20
Emission factors were taken from the previously disc ussed measurements, with mixture control in “full rich” position and the engine doing auto-lean, as disc ussed in 5.b). Because of very incomplete combustion (as described in section 3 of this Appendix), the mean emission factor for CO 2 is far below the theoretical 3.17 kg / kg fuel. For this calculation we assume again a conservative factor of 2 kg CO 2 / kg fuel and 1.2 kg H 2 O / kg fuel. The lead content in AVGAS 100LL is considered 0.794 g / kg fuel, the fuel density 0.72 kg / liter.

Table 5: Total emissions for 1 circuit (emissionsinventar.volten.HBKIA_060921_rit) HBKIA fuel (kg) CO (g) HC (g) NOx (g) CO2 (kg) H20 (kg) lead (g) Pilot 1 4.10 3291 52 24 8.19 4.92 3.25 Pilot 2 3.88 3371 62 20 7.77 4.66 3.08Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 5.d) Discussion
During 1 circuit, HBKIA burns around 4 kg fuel and produces roughly 3 kg CO, 50 g HC and 20 g NO x , 8 kg CO 2 , 5 kg H 2 O and 3 g lead. From the existing measurement experience, FOCA assu mes that significant differences in the results between pilot 1 and pilot 2 of more than 5% can be at tributed to pilot operations. Table 5 shows thatpilot 2 was flying more efficient. This can be explained by lower power settings, especially in the downwind leg (see figures 79 and 73). Part of this gain would be compensated by longer downwind time. The lower power setting results in slightly higher CO and HC emissions and lower NO x emissions, as can be seen in table 5. CO 2 , H 2 O and lead emissions are directly propor tional to fuel burn, hence are lower for pilot 2 operations. Generally speaking, the differences between the tw o measurement sets and the influence of the pilot are not significantly high for this aircraft during circui t flying. This may be attributed mainly to the fact, that the engine of HBKIA is automatically leaned and hence produces similar combustion conditions in both cases. Remaining differences outside possibl e measurement statistical errors may be caused from different power settings in the downwind, base and final leg of the circuit.

5.e) Additional high altitude circuit flight testing at Samedan Airport (5600ft AMSL), Switzerland

As in 3.e) we wanted to investigate the emission s performance at a high altitude airport. The function of the auto-lean feature of the te sted engine and the effect on emissions was of particular interest.

CO Emission Factors

0 200 400 600 800 1000 1200 1400

ModeMass (g/kg Fuel)

CO 1151 1040 860 882 882 742 1385 809 727 1388 808 871 745 1274 821 858 732 1051 TA MC Check TO TO/CL CL DWD Final TO DWD Final TO CL DWD Final TO CL DWD FinalH RPM

Figure 81: CO emission factors during four aerodrome ci rcuits (TA = Taxi, MC = Magneto Check, TO = Take off roll, CL = Climb at vy 7 , DWD = downwind), flown at Samedan Airport (ECERT 59, HBKIA )

7 Vy = indicated airspeed for best rate of climbReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern HC Emission Factors

0 10 20 30 40 50 60

ModeMass (g/kg Fuel)

HC NDIR 42 24 26 20 20 9 24 41 11 23 52 25 11 19 59 27 12 18 TA MC Check TO TO/CL CL DWD Final TO DWD Final TO CL DWD Final TO CL DWD FinalH RPM

Figure 82: HC emission factors during four aerodrome circ uits (TA = Taxi, MC = Magneto Check, TO = Take off roll, CL = Climb at vy, DWD = downwind), fl own at Samedan Airport (ECERT 59, HBKIA )

NOx Emission Factors

0 2 4 6 8 10 12

ModeMass (g/kg Fuel)

NOx 1 2 6 6 6 7 1 8 9 1 8 6 10 1 7 6 10 2 TA MC Check TO TO/CL CL DWD Final TO DWD Final TO CL DWD Final TO CL DWD FinalH RPM

Figure 83: NO x emission factors during four aerodrome circuits (TA = Taxi, MC = Magneto Check, TO = Take off roll, CL = Climb at vy, DWD = downwind), fl own at Samedan Airport (ECERT 59, HBKIA )

Fuel Flow

0 10 20 30 40 50 60 70 80 90

ModeFuel Flow (l/h)

Fuel 18 26 81 81 79 61 36 79 57 39 80 80 59 42 81 78 61 57 TA MC Check TO TO/CL CL DWD Final TO DWD Final TO CL DWD Final TO CL DWD FinalHR PM

Figure 84: Fuel flow during four aerodrome circuits (TA = Taxi, MC = Magneto Check, TO = Take off roll, CL = Climb at vy, DWD = downwind), flown at Samedan Airport (ECERT 59, HBKIA ) ? ? ?Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Manifold Pressure

0 5 10 15 20 25

ModeManifold Pressure (in Hg)

Man. Pr. 12 12.2 23 23 22.8 21 10 23 19.5 11 23.2 23.2 20 12 23 23 20 15 TA MC Check TO TO/CL CL DWD Final TO DWD Final TO CL DWD Final TO CL DWD FinalHR PM

Figure 85: Manifold pressure during four aerodrome circui ts (TA = Taxi, MC = Magneto Check, TO = Take off roll, CL = Climb at vy, DWD = downwind), flown at Samedan Airport (ECERT 59, HBKIA )

Lambda

0 0.2 0.4 0.6 0.8

1

ModeLambda

Lambda 0.903 0.741 0.788 0.781 0. 781 0.819 0.624 0.798 0.823 0.623 0.797 0. 782 0.819 0.664 0.792 0.785 0.822 0.735 TA MC Check TO TO/CL CL DWD Final TO DWD Final TO CL DWD Final TO CL DWD FinalHR PM

Figure 86: Lambda during four aerodrome circuits (TA = Taxi, MC = Magneto Check, TO = Take off roll, CL = Climb at vy, DWD = downwind), flown at Samedan Airport (ECERT 59, HBKIA )

5.f) Discussion The circuits at Samedan have been flown by the sa me pilot, as in ECERT 62 (circuits at Grenchen airport, see 5.a). Therefore the results of ECERT 62 are compared to that of ECERT 59 (circuits at Samedan airport). ECERT 59 data do not contain the base leg. In Samedan, the base leg consists basically of a 180° turn. First of all, it can be seen from figures 79 and 85 t hat the four circuits flown in Samedan did not show a consistent repetitive power setting. There is no clea r repetition of the power setting pattern as shown in figure 79. This can be explained by the fact that the wind conditions in the alpine valley were very variable, resulting in different power adjustments. Be cause of the high altitude (in fact the density altitude varied between 6800 and 7800ft in the circuits), maximum manifold pressure at take off was only at 23 In Hg 8 (figure 85) and maximum engine power was approximately as low as normal cruise power. From comparison between figures 80 and 86 it can be seen that the auto-lean mixture adjustment for take-off power was not as good as in the lower altitude measurement (5.a). The engine ran still very rich. In fact, it seems that the measured engine doe s not automatically fully compensate the air-fuelmixture for the lower air density and additional m anual leaning would have been necessary in this situation. The result can be seen with higher CO and HC values at high power settings compared to ECERT 62. Once again, HC values are highest for take-off. We were not able to find out, whether this was real and resulted from the particular engine condition with low manifold pressure in the air intake, richer conditions and the throttle fully open or resu lted from a systematic error in the measurement. (figure 82).

8 In Hg = Inches mercury column, 23 In Hg = 779 hPaReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 5.g) Inventory: Comparison of total emissions of HBKIA in the low and high altitude aerodrome circuit
For this comparison of total emissions in the circuits , we used the same mean circuit times as in 3.g), 5.c) and the data of 5.e). In order to obtain more general results, we used mean FOCA standard times instead of Samedan circuit times for this comparison.

Table 6 : Mode Times in Mode (s) TAKE-OFF 20 CLIMB OUT 75 DOWNWIND 90 BASE 105 FINAL 20
Emission factors were taken from the previously disc ussed measurements, with mixture control in “full rich” position and the engine doing auto-lean, as disc ussed in 5.b) and 5.f). Because of very incomplete combustion (as described in section 3 of this Appendix), the mean emission factor for CO 2 is far below the theoretical 3.17 kg / kg fuel. For this calc ulation we assume again a conservative factor of 2 kg CO 2 / kg fuel and 1.2 kg H 2 O / kg fuel. The lead content in AVGAS 100LL is considered 0.794 g / kg fuel, the fuel density 0.72 kg / liter. The missing base leg data in ECERT 59 has been interpolated between “downwind” and “final”.

Table 7: Total circuit emissions (1 circuit), calcul ated with mean values from Grenchen and Samedan measurements and table 6. fuel (kg) CO (g) HC (g) NOx (g) CO2 (kg) H20 (kg) lead (g) Samedan (ECERT 59) 3.81 3309 72 22 7.63 4.58 3.03 Grenchen (ECERT 62) 3.88 3371 62 20 7.77 4.66 3.08
5.h) Discussion
The result for high altitude circuits with HBKIA s uggests similar total emissions, which are within measurement uncertainties. The higher emission factor s of the richer running engine are partly compensated by a lower fuel burn during the high powe r segments of the circuit. For emission inventories with TCM IO-550 engine, the following values are suggested for 1 circuit (based on table 6 times):

Table 8: Suggested emission totals for 1 aerodrome circuit with TCM IO-550 B. (33-05-003 emissionsinventar.volten.HBKIA_060921_rit)

TCM IO-550 B fuel (kg) CO (g) HC (g) NOx (g) CO2 (kg) H20 (kg) lead (g) 1 Aerodrome circuit 3.9 3300 60 22 7.8 4.6 3.1

5.i) Systematic measurements at full power se ttings between 3000 and 6000ft flight altitude
The following measurements, ECERT 58, 61 and 65 have been performed on three different days, with different meteorological conditions. Measur ements for take-off, climb and approach have been separated into different sets of figures.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern CO Emission Factors

0 200 400 600 800 1000 1200

ModeMass (g/kg Fuel)

CO 710 818 879 855 823 734 829 785 821 803 737 718 721 724 855 806 802 TO 2300 TO 3000 TO 4000 TO 5000 TO 6000 TO 5000 TO 6000 TO 3000 TO 4000 TO 5000 TO 6000 TO 3000 TO 3000 TO 3000 TO 4000 TO 4000 TO 4000

Figure 87: CO emission factors for full power climb, meas ured at different flight al titudes, e.g. TO 2300 means take-off measurement at 2300ft pressure altitude (From le ft to right: No 1 – 7 from ECERT58, No 8 – 11 from ECERT61 and No 12 – 17 from ECERT 65).

HC Emission Factors

0 5 10 15 20 25

ModeMass (g/kg Fuel)

HC NDIR 16 15 17 18 18 18 16 12 12 13 14 14 14 15 14 16 16 TO 2300 TO 3000 TO 4000 TO 5000 TO 6000 TO 5000 TO 6000 TO 3000 TO 4000 TO 5000 TO 6000 TO 3000 TO 3000 TO 3000 TO 4000 TO 4000 TO 4000

Figure 88: HC emission factors for full power climb, measur ed at different flight altitudes, e.g. TO 2300 means take-off measurement at 2300ft pressure altitude (From le ft to right: No 1 – 7 from ECERT58, No 8 – 11 from ECERT61 and No 12 – 17 from ECERT 65).

NOx Emission Factors

0 2 4 6 8 10 12

ModeMass (g/kg Fuel)

NOx 9 7 4 5 6 10 7 8 4 4 4 10 9 9 6 7 7 TO 2300 TO 3000 TO 4000 TO 5000 TO 6000 TO 5000 TO 6000 TO 3000 TO 4000 TO 5000 TO 6000 TO 3000 TO 3000 TO 3000 TO 4000 TO 4000 TO 4000

Figure 89: NO x emission factors for full power climb, measured at different flight altitudes, e.g. TO 2300 means take-off measurement at 2300ft pressure altitude (From le ft to right: No 1 – 7 from ECERT58, No 8 – 11 from ECERT61 and No 12 – 17 from ECERT 65).Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Fuel Flow

0 10 20 30 40 50 60 70 80 90 100

ModeFuel Flow (l/h)

Fuel 90 89 88 87 80 87 80 91 88 86 83 91 91 91 90 90 89 TO 2300 TO 3000 TO 4000 TO 5000 TO 6000 TO 5000 TO 6000 TO 3000 TO 4000 TO 5000 TO 6000 TO 3000 TO 3000 TO 3000 TO 4000 TO 4000 TO 4000

Figure 90: Fuel flow for full power climb, measured at di fferent flight altitudes, e.g. TO 2300 means take-off measurement at 2300ft pressure altitude (F rom left to right: No 1 – 7 from ECERT58, No 8 – 11 from ECERT61 and No 12 – 17 from ECERT 65).

RPM

0 500 1000 1500 2000 2500 3000

ModeRPM (1/Min.)

RPM 2550 2550 2550 2540 2550 2580 2550 2610 2580 2610 2600 2580 2580 2560 2580 2580 2590 TO 2300 TO 3000 TO 4000 TO 5000 TO 6000 TO 5000 TO 6000 TO 3000 TO 4000 TO 5000 TO 6000 TO 3000 TO 3000 TO 3000 TO 4000 TO 4000 TO 4000

Figure 91: Engine revolutions per minute for full power clim b, measured at different flig ht altitudes, e.g. TO 2300 means take-off measurement at 2300ft pressure altitude (F rom left to right: No 1 – 7 from ECERT58, No 8 – 11 from ECERT61 and No 12 – 17 from ECERT 65).

Manifold Pressure

0 5 10 15 20 25 30

ModeManifold Pressure (in Hg)

Man. Pr. 26.2 25.6 24.8 23.8 23 24 22.9 25.6 24.9 23.9 23 26 26 26 25 25 25 TO 2300 TO 3000 TO 4000 TO 5000 TO 6000 TO 5000 TO 6000 TO 3000 TO 4000 TO 5000 TO 6000 TO 3000 TO 3000 TO 3000 TO 4000 TO 4000 TO 4000

Figure 92: Manifold pressure for full power climb, measured at different flight altitudes, e.g. TO 2300 means takeoff measurement at 2300ft pressure altitude (From left to right: No 1 – 7 from ECERT58, No 8 – 11 from ECERT61 and No 12 – 17 from ECERT65).Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Lambda

0 0.2 0.4 0.6 0.8

1 1.2

ModeLambda

Lambda 0.985 0.932 0.9 0.898 0.895 0.918 0.987 0.81 0.798 0.802 0.819 0. 829 0.828 0.826 0.788 0.803 0.803 TO 2300 TO 3000 TO 4000 TO 5000 TO 6000 TO 5000 TO 6000 TO 3000 TO 4000 TO 5000 TO 6000 TO 3000 TO 3000 TO 3000 TO 4000 TO 4000 TO 4000

Figure 93: Lambda for full power climb, measured at different flight altitudes, e.g. TO 2300 means take-off measurement at 2300ft pressure altitude (F rom left to right: No 1 – 7 from ECERT58, No 8 – 11 from ECERT61 and No 12 – 17 from ECERT65).

5.j) Discussion
From figure 93 it can be seen that the engine was running significantly less rich in ECERT58 than in ECERT61 and 65. This could be attributed to a different general engine adjustment before and after regular maintenance. In ECERT65, after some pilot tr aining and in calm air, power settings and aircraft attitude were more stable, resulting in less fluct uating values. All measurements were made with the mixture lever in “full rich” position. Auto lean works in function of density alti tude, therefore the results are showing differences even at the same pressure altitude, because of different ambient air temperatures. The same is true for the following results (5.k and l), measured at climb and approach power settings.

5.k) Systematic measurements at climb power settings between 3000 and 6000ft flight altitude

CO Emission Factors

0 200 400 600 800 1000 1200

ModeMass (g/kg Fuel)

CO 832 872 849 826 752 796 754 753 701 737 737 708 758 743 CL 3300 CL 4000 CL 5000 CL 6000 CL 3000 CL 4000 CL 5000 CL 6000 CL 3000 CL 3000 CL 3000 CL 4000 CL 4000 CL 4000

Figure 94: CO emission factors for AFM 9 climb power, measured at different flight altitudes, e.g. CL 3300 means climb measurement at 3300ft pressure altitude (From le ft to right: No 1 – 7 from ECERT58, No 8 – 11 from ECERT61 and No 12 – 17 from ECERT 65).

9 AFM = Airplane Flight ManualReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern HC Emission Factors

0 5 10 15 20 25

ModeMass (g/kg Fuel)

HC NDIR 18 19 19 19 14 15 16 16 15 15 15 15 17 18 CL 3300 CL 4000 CL 5000 CL 6000 CL 3000 CL 4000 CL 5000 CL 6000 CL 3000 CL 3000 CL 3000 CL 4000 CL 4000 CL 4000

Figure 95: HC emission factors for AFM climb power, meas ured at different flight altitudes, e.g. CL 3300 means climb measurement at 3300ft pressure altitude (From le ft to right: No 1 – 7 from ECERT58, No 8 – 11 from ECERT61 and No 12 – 17 from ECERT 65).

NOx Emission Factors

0 2 4 6 8 10 12

ModeMass (g/kg Fuel)

NOx 6 6 6 7 9 6 5 5 10 9 9 10 8 8 CL 3300 CL 4000 CL 5000 CL 6000 CL 3000 CL 4000 CL 5000 CL 6000 CL 3000 CL 3000 CL 3000 CL 4000 CL 4000 CL 4000

Figure 96: NO x emission factors for AFM climb power, measured at different flight altitudes, e.g. CL 3300 means climb measurement at 3300ft pressure altitude (From le ft to right: No 1 – 7 from ECERT58, No 8 – 11 from ECERT61 and No 12 – 17 from ECERT 65).

Fuel Flow

0 10 20 30 40 50 60 70 80 90 100

ModeFuel Flow (l/h)

Fuel 84 82 80 76 87 85 81 79 89 87 87 83 85 85 CL 3300 CL 4000 CL 5000 CL 6000 CL 3000 CL 4000 CL 5000 CL 6000 CL 3000 CL 3000 CL 3000 CL 4000 CL 4000 CL 4000

Figure 97: Fuel flow for AFM climb power, measured at di fferent flight altitudes, e. g. CL 3300 means climb measurement at 3300ft pressure altitude (F rom left to right: No 1 – 7 from ECERT58, No 8 – 11 from ECERT61 and No 12 – 17 from ECERT 65).Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern RPM

0 500 1000 1500 2000 2500 3000

ModeRPM (1/Min.)

RPM 2440 2450 2450 2450 2470 2470 2470 2480 2440 2470 2450 2470 2470 2460 CL 3300 CL 4000 CL 5000 CL 6000 CL 3000 CL 4000 CL 5000 CL 6000 CL 3000 CL 3000 CL 3000 CL 4000 CL 4000 CL 4000

Figure 98: RPM for AFM climb power (Reference 2500 RPM), measured at different flig ht altitudes, e.g. CL 3300 means climb measurement at 3300ft pressure altitude (Fro m left to right: No 1 – 7 from ECERT58, No 8 – 11 from ECERT61 and No 12 – 17 from ECERT 65).

Manifold Pressure

0 5 10 15 20 25 30

ModeManifold Pressure (in Hg)

Man. Pr. 25.2 24.9 23.9 23 25.8 24.9 24 23 26 26 26 25 25 25 CL 3300 CL 4000 CL 5000 CL 6000 CL 3000 CL 4000 CL 5000 CL 6000 CL 3000 CL 3000 CL 3000 CL 4000 CL 4000 CL 4000

Figure 99: Manifold pressure for AFM climb power, measur ed at different flight altitudes, e.g. CL 3300 means climb measurement at 3300ft pressure altitude (From le ft to right: No 1 – 7 from ECERT58, No 8 – 11 from ECERT61 and No 12 – 17 from ECERT 65).

Lambda

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

ModeLambda

Lambda 0.886 0.896 0.883 0.888 0.818 0.804 0.814 0. 815 0.832 0.832 0.832 0.83 0.816 0.82 CL 3300 CL 4000 CL 5000 CL 6000 CL 3000 CL 4000 CL 5000 CL 6000 CL 3000 CL 3000 CL 3000 CL 4000 CL 4000 CL 4000

Figure 100: Lambda for AFM climb power, measured at diff erent flight altitudes, e.g. CL 3300 means climb measurement at 3300ft pressure altitude (F rom left to right: No 1 – 7 from ECERT58, No 8 – 11 from ECERT61 and No 12 – 17 from ECERT 65).Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern5.l) Systematic measurements at approach power settings between 3000 and 6000ft flight altitude

CO Emission Factors

0 200 400 600 800 1000 1200

ModeMass (g/kg Fuel)

CO 556 585 677 832 616 659 786 819 1024 822 991 903 933 937 AP 6000 AP 5000 AP 4000 AP 3000 AP 6000 AP 5000 AP 4000 AP 3000 AP 3000 AP 3000 AP 3000 AP 4000 AP 4000 AP 4000

Figure 101: CO emission factors for approach power, meas ured at different flight al titudes, e.g. AP 6000 means approach measurement at 6000ft pressure altitude (From le ft to right: No 1 – 7 from ECERT58, No 8 – 11 from ECERT61 and No 12 – 17 from ECERT 65).

HC Emission Factors

0 5 10 15 20 25

ModeMass (g/kg Fuel)

HC NDIR 7 8 8 9 8 10 11 11 11 11 10 11 12 11 AP 6000 AP 5000 AP 4000 AP 3000 AP 6000 AP 5000 AP 4000 AP 3000 AP 3000 AP 3000 AP 3000 AP 4000 AP 4000 AP 4000

Figure 102: HC emission factors for approach power, m easured at different flight altitudes, e.g. AP 6000 means approach measurement at 6000ft pressure altitude (From le ft to right: No 1 – 7 from ECERT58, No 8 – 11 from ECERT61 and No 12 – 17 from ECERT 65).

NOx Emission Factors

0 2 4 6 8 10 12 14 16 18 20

ModeMass (g/kg Fuel)

NOx 17 16 12 7 14 12 8 7 4 8 4 5 5 5 AP 6000 AP 5000 AP 4000 AP 3000 AP 6000 AP 5000 AP 4000 AP 3000 AP 3000 AP 3000 AP 3000 AP 4000 AP 4000 AP 4000

Figure 103: NO x emission factors for approach power, measured at different flight altitudes, e.g. AP 6000 means approach measurement at 6000ft pressure altitude (From le ft to right: No 1 – 7 from ECERT58, No 8 – 11 from ECERT61 and No 12 – 17 from ECERT 65).Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Fuel Flow

0 10 20 30 40 50 60 70 80 90 100

ModeFuel Flow (l/h)

Fuel 57 55 57 58 51 51 52 53 52 52 52 52 53 52 AP 6000 AP 5000 AP 4000 AP 3000 AP 6000 AP 5000 AP 4000 AP 3000 AP 3000 AP 3000 AP 3000 AP 4000 AP 4000 AP 4000

Figure 104: Fuel flow for approach power, measured at different flight altitudes, e.g. AP 6000 means approach measurement at 6000ft pressure altitude (From left to ri ght: No 1 – 7 from ECERT58, No 8 – 11 from ECERT61 and No 12 – 17 from ECERT 65).

RPM

0 500 1000 1500 2000 2500

ModeRPM (1/Min.)

RPM 2280 2280 2290 2290 2270 2250 2250 2250 2240 2230 2240 2250 2280 2250 AP 6000 AP 5000 AP 4000 AP 3000 AP 6000 AP 5000 AP 4000 AP 3000 AP 3000 AP 3000 AP 3000 AP 4000 AP 4000 AP 4000

Figure 105: Engine RPM for approach power, measured at different flight altitudes, e.g. AP 6000 means approach measurement at 6000ft pressure altitude (From left to ri ght: No 1 – 7 from ECERT58, No 8 – 11 from ECERT61 and No 12 – 17 from ECERT 65).

Manifold Pressure

0 5 10 15 20 25

ModeManifold Pressure (in Hg)

Man. Pr. 20 20 20 19.8 17.5 17.5 17.5 17.5 17 17 17 17 17 17 AP 6000 AP 5000 AP 4000 AP 3000 AP 6000 AP 5000 AP 4000 AP 3000 AP 3000 AP 3000 AP 3000 AP 4000 AP 4000 AP 4000

Figure 106: Manifold pressure settings for approach powe r, measured at different f light altitudes, e.g. AP 6000 means approach measurement at 6000ft pressure altitude (F rom left to right: No 1 – 7 from ECERT58, No 8 – 11 from ECERT61 and No 12 – 17 from ECERT 65). In ECERT 65, manifold pressure has been kept constant during descent.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Lambda

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

ModeLambda

Lambda 0.898 0.902 0.871 0.829 0.854 0.845 0.811 0. 805 0.745 0.8 0.754 0.778 0.769 0.768 AP 6000 AP 5000 AP 4000 AP 3000 AP 6000 AP 5000 AP 4000 AP 3000 AP 3000 AP 3000 AP 3000 AP 4000 AP 4000 AP 4000

Figure 107: Lambda for approach power, measured at different flight altitudes, e.g. AP 6000 means approach measurement at 6000ft pressure altitude (From left to ri ght: No 1 – 7 from ECERT58, No 8 – 11 from ECERT61 and No 12 – 17 from ECERT 65).

5.m) Standard flight profile emission measurement Bern - WIL 10 - Bern, Switzerland
The following flight profile has been flown at two different days by two different pilots: - Departure at LSZB (Bern) - Outbound route E - Continuous climb to 5500ft - Level off at 5500ft and maintain - Track WIL VOR - Cruise power setting, first full rich (CR 5510), then three measurements (C R 5500) at mixture “25°F rich side of EGT 11 peak according to AFM 12 , followed by “best power mixture, 125°F rich of EGT peak” (CR 5500 BP) and again two measurements at mixtur e “25°F rich side of EGT peak”. After that, one measurement (CR 5500) at mixture “25°F lean of EGT peak” according to AFM and the last cruise measurement at mixture “25°F rich side of EGT peak” as before. - Descent and approach were at pilot’s discretion and the two pilots were told to always fly according to AFM. - 180° turn at WIL VOR and return to LSZB (Bern) - Approach and Landing at LSZB

CO Emission Factors

0 200 400 600 800 1000 1200 1400 1600

ModeMass (g/kg Fuel)

CO Pilot 1 1105 747 807 856 891 866 793 396 325 350 603 491 313 14 425 345 293 461 494 619 604 938 1161 113 3
CO Pilot 2 1136 772 811 852 862 808 794 612 390 386 400 392 25 26 27 723 783 1020 850 1154 992 1393 970 TA 167 3 TO 170 0 CL 230 0 CL 300 0 CL 400 0 CL 500 0 CR 551 0 CR 550 0 CR 550 0 CR 550 0 CR 550 0 BP CR 550 0 CR 550 0 CR 550 0 CR 550 0 DCT 540 0 DCT 510 0 DCT 480 0 DCT 430 0 DCT 420 0 R DCT 370 0 AP 320 0 AP 240 0 Fina l 190

Figure 108: CO emission factors comparison for both flights. TA = taxi, TO = take-off ro ll, CL = climb, CR = cruise, DCT = descent, AP = approach. The number below the flight mode indicates flight pressure altitude, e.g. DCT 5100 = measurement during descent at 5100ft. (ECERT 57 and 64)

10 WIL = Willisau VOR (Radio Navigation Facility) 11 EGT = Exhaust Gas Temperature, at this aircraft, measured in the collector of the exhaust muffler on the right side of the engine (= exhaust gas temperature mixture of three cylinders out of six). 12 AFM = Airplane Flight ManualReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern HC Emission Factors

0 10 20 30 40 50

ModeMass (g/kg Fuel)

HC Pilot 1 114 16 16 16 17 17 17 11 10 10 12 11 11 5 12 8 7 8 8 8 9 13 13 15
HC Pilot 2 50 17 17 18 19 19 18 11 10 10 10 11 4 4 4 6 9 13 11 18 13 48 14 TA 167 TO 170 CL 230 CL 300 CL 400 CL 500 CR 551 CR 550 CR 550 CR 550 CR 550 CR 550 CR 550 CR 550 CR 550 DCT 540 DCT 510 DCT 480 DCT 430 DCT 420 DCT 370 AP 320 AP 240 Fina l

Figure 109: HC emission factors comparis on for both flights. TA = taxi, TO = ta ke-off roll, CL = climb, CR = cruise, DCT = descent, AP = approach. The number below the flight mode indicates flight pressure altitude, e.g. DCT 5100 = measurement during descent at 5100ft. (ECERT 57 and 64)

NOx Emission Factors

0 10 20 30 40 50

ModeMass (g/kg Fuel)

NOx Pilot 1 0 9 7 4 3 5 8 28 35 32 15 20 35 87 26 32 39 24 22 16 15 5 2 2
NOx Pilot 2 1 9 3 1 2 3 3 10 29 29 28 29 38 37 32 11 8 3 6 2 3 0 3 TA 167 3 TO 170 0 CL 230 0 CL 300 0 CL 400 0 CL 500 0 CR 551 0 CR 550 0 CR 550 0 CR 550 0 CR 550 0 BP CR 550 0 CR 550 0 CR 550 0 CR 550 0 DCT 540 0 DCT 510 0 DCT 480 0 DCT 430 0 DCT 420 0 R DCT 370 0 AP 320 0 AP 240 0 Fina l 190

Figure 110: NO x emission factors comparison for both flights. TA = taxi, TO = take-off roll, CL = climb, CR = cruise, DCT = descent, AP = approach. The number below the f light mode indicates flight pressure altitude, e.g. DCT 5100 = measurement during descent at 5100ft. (ECERT 57 and 64)

Fuel Flow

0 20 40 60 80 100

ModeFuel Flow (l/h)

Fue Pilot 1 17 91 89 89 87 85 79 65 64 64 68 65 64 49 65 57 58 55 56 58 56 47 45 45
Fuel Pilot 2 18 95 95 87 84 81 80 66 64 64 64 64 49 49 49 52 52 51 49 53 49 36 61 TA 1673 TO 1700 CL 2300 CL 3000 CL 4000 CL 5000 CR 5510 CR 5500 CR 5500 CR 5500 CR 5500 CR 5500 CR 5500 CR 5500 CR 5500 DCT 5400 DCT 5100 DCT 4800 DCT 4300 DCT 4200 DCT 3700 AP 3200 AP 2400 Final 1900

Figure 111: Fuel flow comparison for both flights. TA = taxi, TO = take-off roll, CL = climb, CR = cruise, DCT = descent, AP = approach. The number below the flight mode i ndicates flight pressure altitude, e.g. DCT 5100 = measurement during descent at 5100ft. (ECERT 57 and 64)Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern RPM

0 500 1000 1500 2000 2500 3000

ModeRPM (1/Min.)

RPM Pilot 1 1120 2550 2540 2530 2530 2530 2530 2300 2310 2320 2320 2300 2300 2300 2310 2310 2310 2300 2310 2310 2170 2170 2160 2150
RPM Pilot 2 1160 2640 2470 2470 2460 2460 2460 2250 2250 2230 2250 2240 2060 2060 2060 2250 2290 2290 2280 2280 2270 1930 2440 TA 1673 TO 1700 CL 2300 CL 3000 CL 4000 CL 5000 CR 5510 CR 5500 CR 5500 CR 5500 CR 5500 CR 5500 CR 5500 CR 5500 CR 5500 DCT 5400 DCT 5100 DCT 4800 DCT 4300 DCT 4200 DCT 3700 AP 3200 AP 2400 Final 1900

Figure 112: Engine RPM comparison for both flights. TA = taxi, TO = take-off roll, CL = climb, CR = cruise, DCT = descent, AP = approach. The number below the flight mode i ndicates flight pressure altitude, e.g. DCT 5100 = measurement during descent at 5100ft. (ECERT 57 and 64)

Manifold Pressure

0 5 10 15 20 25 30

ModeManifold Pressure (in Hg)

Man. Pr. Pilot 1 13.5 27 26.5 26 25 24 23.2 23.4 23 23 23 23 23 23 23 20 21 19.8 19.9 20 21 16.2 15 15
Man. Pr. Pilot 2 13.2 27 26.5 26 24.8 24 23.5 23 23 23 23 23 22.5 22.5 22.5 17 17 16.2 16 17 16.5 11 17 TA 1673 TO 1700 CL 2300 CL 3000 CL 4000 CL 5000 CR 5510 CR 5500 CR 5500 CR 5500 CR 5500 CR 5500 CR 5500 CR 5500 CR 5500 DCT 5400 DCT 5100 DCT 4800 DCT 4300 DCT 4200 DCT 3700 AP 3200 AP 2400 Final 1900

Figure 113: Manifold pressure comparis on for both flights. TA = taxi, TO = ta ke-off roll, CL = climb, CR = cruise, DCT = descent, AP = approach. The number below the flight mode indicates flight pressure altitude, e.g. DCT 5100 = measurement during descent at 5100ft. (ECERT 57 and 64)

Lambda

0 0.2 0.4 0.6 0.8

1 1.2 1.4

ModeLambda

Lambda Pilot 1 0.883 0.821 0.825 0.818 0.809 0.815 0.837 0.925 0.943 0.957 0.9 0.944 1. 02 1.269 1.011 1.008 1.031 0.974 0. 972 0.937 0.943 0.84 0.848 0.826
Lambda Pilot 2 0.902 0.812 0.798 0.787 0.784 0.799 0.803 0.852 0.909 0.91 0.907 0.908 1.251 1.25 1.259 0.829 0.812 0. 747 0.795 0.705 0.754 0.633 0.761 TA 1673 TO 1700 CL 2300 CL 3000 CL 4000 CL 5000 CR 5510 CR 5500 CR 5500 CR 5500 CR 5500 CR 5500 CR 5500 CR 5500 CR 5500 DCT 5400 DCT 5100 DCT 4800 DCT 4300 DCT 4200 DCT 3700 AP 3200 AP 2400 Final 1900

Figure 114: Lambda comparison for both fl ights. TA = taxi, TO = take-off roll, CL = climb, CR = cruise, DCT = descent, AP = approach. The number below the flight mode i ndicates flight pressure altitude, e.g. DCT 5100 = measurement during descent at 5100ft. (ECERT 57 and 64)

5.n) Discussion
Taxi, Take-off, Climb During taxi, take-off and climb, there are no signific ant differences between the results of ECERT57 (pilot 1) and 64 (pilot 2). Both pilo ts operate the aircraft in a similar way with a power reduction to 25Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern inHG manifold pressure in the climb phase. Manual mi xture control is set to “full rich” and the engine is doing automatic lean, producing similar emission factors in both flights. This is also true for the first cruise power setting with mixture “full rich”.

Cruise The task for the two pilots, to adjust the mixture to “25°F rich of EGT peak”, best power “125°F rich of EGT peak” and economy power “25°F lean of EGT peak ” (which is an allowed operating condition for this type of engine), was definitely leading to different results. Most sensitive to differences in mixture are NO x emission factors (figure 110) and CO emission factors (figure 108). It can also be seen, that the mixture settings of pilot 2 are more constant t han those of pilot 1. At “lean of EGT peak” mixture, pilot 2 was able to adjust the engine repeatedly to smooth running lean conditions (lambda around 1.2) with CO and HC emissions falling drastically (figure 108 / 109 middle) and without increasing NO x emissions (figure 11 0) too much. [It must also be noted that engine cylinder head temperatures were falling from around 150°C to 140°C during that oper ating condition and airspeed was reduced by a few knots due to power loss]. From previous results and the results of the cruise phase measured during these flights, it can be concluded:
From point of view of emissions, the “lean of EGT peak” setting is preferred, producing lowest possible emissions. All emission factors and the fuel flow are lower than with “rich of EGT peak” setting. This is especially true for NO x , because these emissions are hi ghest with the “rich of EGT peak” setting, mainly because of the highest comb ustion temperatures. Very strict “lean of EGT peak” conditions lead to lower cylinder head temperatures.
However, from point of view of operations, the “lean of EGT peak” setting has a lot of limitations : - The rather simple engine technology of the meas ured type (air cooled, fuel injection system, not taking individual cylinder operating condition into account) leads to uneven mixture distribution and cylinder filling in the six cylinders (u neven “charging weight”), causing all six cylinders to be in six different operating conditions at a certain mixture setting. There is the risk ofone or more cylinders being at higher operating conditions which can cause vibrations, additional wear and valve damage. - Safety margins for engine operations are more limited, because one or more cylinders may go into the self detonation or flame out conditi on, if the pilot does not observe the engine carefully or if the pilot forgets to enrich the mixture for descent. At “rich conditions”, the margins for safe operations are much higher. - Pilots need to be well trained as “lean conditi ons” require even more attentive engine observation which can distract from the primary air work.
For the emission inventory application , it can be concluded that it is probably more representative to take “rich of EGT peak” conditions as the refere nce for the cruise phase, because in most cases, such engines will be ope rated at “rich” conditions. As could be se en in the in-flight tests with HBKEZ and HBEYS, “rich of EGT peak” conditions typically lead to a lambda of around 0.93 to 0.95 which can be a basis value for engine on ground measuremen ts at cruise power setti ng. This value for “rich of EGT peak” condition has been conf irmed with the HBKIA flights.
Descent and Approach Within the limits of the AFM, pilots were free to choose the “top of desce nt” point and the power settings for descent and approach. Figure 113 shows th at pilot 2 was choosing less power during descent. [Pilot 1 started the descent early, with a sma ll rate of descent and higher power.] The effect of lower power setting in the case of pilot 2 can be s een in lower instantaneous fuel consumption (figure 111) and lower NO x emission factors but significantly higher CO and HC emission factors. The effect on total emissions will be discussed in the next sect ion 5.o/p). In the first part of the approach, both pilots used similar power settings (around 17 InHg manifold pressure and similar selected propeller RPM. In the second part of the approach, pilot 2 reduced engine power further but later had to increase power during final above the pilot 1 power setting.
For the emission inventory application , it can be seen that the descent and approach phase are very dependent on pilots operational choice (wheth er forced by the environment, weather etc or not) and therefore, sort of mean power settings have to be derived for standardized ground measurements. From the sum of the in-fli ght tests with HBEYS, HBKEZ and H BKIA it can be concluded, that a preferred power setting for this phase of flight seems to be around 18 InHg with a fuel flow of 40 to 45% of the maximum take-off power fuel flow. These values are taken as the basic values for engine ground measurements at approach power setting.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 5.o) Inventory: Total emissions of HBKIA in a flight, defined in 5.m)

Figure 115: ECERT 57 (Defined Flight from Bern to Wilis au VOR and back to Bern, flown by pilot 1). The altitude profile is plotted in dark blue. Engine RPM, manifold pressu re and fuel flow have been added to the same figure. The theoretical LTO and cruise phase boundaries are show n with red and blue darts on top of the figure. 5 Minutes after engine start up, the sharp ri se in fuel flow indicates the beginni ng of the take off roll. After lift-off, manifold pressure is slightly reduced and the fuel flow slightly decreases (at around 6 minutes on the time axis). During level flight at cruise, the pilo t was given different tasks for air/fuel mixture settings. Please note, that all variations of fuel flow (the light blue curve) during crui se level, are caused by different choice of engine operating air/fuel mixture conditions at const ant RPM and constant manifold pressure (see 5.m)! At around 15 minutes on the time axis, the engine is run at slightly rich air/fuel mixture. At about 18 minutes the mixture is further enriched for best power, followed by the previous setting. At about 23 minutes, the air/fuel mixture is set to lean conditions, which is shown by a significant reduction of fuel flow. During descent and the first par t of the approach, the fuel flow does not significantly fall below cruise fuel flow. This is due to the standard mixture enrichment for approach, causing the engine to run less efficiently. Because of the au to lean capabilities of the tested engine, the effect is not as pronounced as it was with HBKEZ (see figure 61).

Figure 116: ECERT 64 (Defined Flight from Bern to Wilisau VOR and back to Bern, as above, flown by pilot 2). In contrast to pilot 1, pilot 2 was achieving only two differ ent manual mixture settings during cruise: 25°F rich of peak EGT and lean of peak EGT. There is a long lean of EG T peak phase, showing significantly lower fuel consumption. The power setting during cruise and the first part of desc ent is slightly lower than that chosen by pilot 1. During cruise, the aircraft was flying slower than that of pilo t 1, resulting in a longer flight time. The descent starts later and with higher descent rate than that chosen by pi lot 1. Pilot 2 was performing rather big power corrections during landing. Flight-Profile LSZB - WIL - LSZB, HB-KIA, Pilot 1, ECERT 57

1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

0 5 10 15 20 25 30 35 40 45 Time (Min)Index

Flightprofile RPM Man. Pressure Fuel Flow mixture 25°F rich of EGT peak manual mixture full rich

best pow er mix lean of EGT peak manual mixture full rich LTO LTO Cruise (Climb) (Descent)

Flight-Profile LSZB - WIL - LSZB, HB-KIA, Pilot 2, ECERT 64

1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

0 5 10 15 20 25 30 35 40 45 Time (Min)Index

Flightprofile RPM Man. Pressure Fuel Flow mixture 25°F rich of EGT peak manual mixture full rich

lean of EGT peak manual mixture full rich LTO LTO Cruise (Climb) (Descent)Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Figure 117: Variation of CO emissi on factor during flight. LTO and cruise phase are indicated in red and blue darts, mixture settings in black darts. (ECERT 57)

Figure 118: Variation of HC emission factor during flight. LTO and cruise phase are indicated in red and blue darts, mixture settings in black darts. (ECERT 57)

Figure 119: Variation of NO x emission factor during flight. LTO and cruise phase are indicated in red and blue darts, mixture settings in black darts. During cruise, at a mixture setting 25°F rich of peak EGT, the EI NO x is around 35 g/kg fuel. Please note, that at lean of EGT peak operation, the EI NO x would decrease below rich of EGT peak value. During this flight, th is does not occur: The EGT aircraft in strumentation in HBKIA does not give individual cylinder EGT. This measurement reveals that although the mean indicated EGT value has dropped with this mixture setting, at least one of the six cylinders must have been runnin g very hot, at peak EGT, thus producing a very high EI NO x ! (ECERT 57) CO Emission Factor Variation During Flight HBKIA, ECERT 57

0 200 400 600 800 1000 1200

0 5 10 15 20 25 30 35 40 45 Time (Min)EI CO (g/kg)

EI CO mixture 25°F rich of EGT peak manual mixture full rich

best pow er mix lean of EGT peak manual mixture full rich LTO LTO Cruise (Climb) (Descent)

HC Emission Factor Variation During Flight HBKIA, ECERT 57

0 20 40 60 80 100 120

0 5 10 15 20 25 30 35 40 45 Time (Min)EI HC (g/kg)

EI HC mixture 25°F rich of EGT peak manual mixture full rich

best pow er mix lean of EGT peak manual mixture full rich LTO LTO Cruise (Climb) (Descent)

NOx Emission Factor Variation During Flight HBKIA, ECERT 57

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0

0 5 10 15 20 25 30 35 40 45 Time (Min)EI NOx (g/kg)

EI NOx mixture 25°F rich of EGT peak manual mixture full rich

best pow er mix lean of EGT peak manual mixture full rich LTO LTO Cruise (Climb) (Descent)Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern For comparison of the two flights and to calculate cu mulative emissions, the cruise phase values have to be generalized. The most common mixture setting with this engine is 25°F rich of peak EGT, so for both flights, the measured values for this setting ha ve been taken for the entire level flight at cruise:

Figure 120: Pilot 1 Flight Profile, used for emission inventory. (ECERT57)

Figure 121: Pilot 2 flight profile, us ed for emission inventory. (ECERT 64)

Figure 122: Comparison of CO emission factor variation during flights with pilot 1 and 2. Please note, that the increase of EI CO P2 (pilot 2) between 23 and 32 minutes after off-block is artificial, because of missing data points. Flight-Profile LSZB - WIL - LSZB, HB-KIA, Pilot 1, ECERT 57

1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

0 5 10 15 20 25 30 35 40 45 Time (Min)Index

Flightprofile RPM Man. Pressure Fuel Flow

Flight-Profile LSZB - WIL - LSZB, HB-KIA, Pilot 2, ECERT 64

1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

0 5 10 15 20 25 30 35 40 45 Time (Min)Index

Flightprofile RPM Man. Pressure Fuel Flow

CO Emission Factor Variation During Flight HBKIA, Pilot 1 and 2

0 200 400 600 800 1000 1200 1400

0 5 10 15 20 25 30 35 40 45 Time (Min)EI CO (g/kg)

EI CO P2 EI CO P1Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Figure 123: Comparison of HC emission factor variatio n during flights with pilot 1 and 2. The much higher HC emission factor during taxi (pilot 1) can be explained by lower engine RPM. At low engine RPM, EI HC drastically increases with decreasing engine RPM.

Figure 124: Comparison of NO x emission factor variation during flights with pilot 1 and 2. Please note, that the decrease of EI NO x P2 (pilot 2) between 23 and 32 minutes after off-block is artificial, because of missing data points, as in figure 122.

Figure 125: Comparison of cumulative fuel consumption duri ng flight with pilot 1 and 2. In this example, pilot 2 chooses reduced cruise power. Hence the flight time is longer. Together with a suboptimal approach pattern, this adds up to higher total fuel consumption. HC Emission Factor Variation During Flight HBKIA, Pilot 1 and 2

0 20 40 60 80 100 120 140 160

0 5 10 15 20 25 30 35 40 45 Time (Min)EI HC (g/kg)

EI HC P2 EI HC P1

NOx Emission Factor Variation During Flight HBKIA, Pilot 1 and 2

-10

0 10 20 30 40 50

0 5 10 15 20 25 30 35 40 45

Time (Min)EI NOx (g/kg)

EI NOx P2 EI NOx P1

Cumulative Fuel Consumption HBKIA, Pilot 1 and 2

0 5 10 15 20 25 30 35

0 5 10 15 20 25 30 35 40 45 Time (Min)Fuel (kg)

Fuel Consumption P2 Fuel Consumption P1Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Figure 126: Comparison of cumulative CO emissions during flight with pilot 1 and 2. In this example, the lower power setting chosen by pilot 2 results in higher CO em issions. The highest portion of CO emissions occurs during taxi and take-off.

Figure 127: Comparison of cumulative HC emissions during flight with pilot 1 and 2. In this example, the lower power setting during taxi, chosen by pilot 2 results in hi gher HC emissions. During flight, HC emissions seem to be very similar between the two flights. The highest por tion of HC emissions occurs during taxi and take-off.

Figure 128: Comparison of cumulative NO x emissions during flight with pilot 1 and 2. In this example, the lower power setting during cruise and descent, chosen by pilot 2 results in lower NO x emissions. The highest portion of NO x emissions occurs during cruise. Cumulative CO Emissions HBKIA, Pilot 1 and 2

0 5000 10000 15000 20000 25000

0 5 10 15 20 25 30 35 40 45 Time (Min)CO (g)

CO Emissions P2 CO Emissions P1

Cumulative HC Emissions HBKIA, Pilot 1 and 2

0 100 200 300 400 500 600

0 5 10 15 20 25 30 35 40 45 Time (Min)HC (g)

HC Emissions P2 HC Emissions P1

Cumulative NOx Emissions HBKIA, Pilot 1 and 2

-100 0 100 200 300 400 500 600

0 5 10 15 20 25 30 35 40 45

Time (Min)NOx (g)

NOx Emissions P2 NOx Emissions P1Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 5.p) Emissions summary for a HBKIA mission, defi ned in 5.m) (300 HP injected traditional aircraft piston engine)

Table 9 HBKIA Pilot 1 Pilot 2 LTO Fuel (kg) 11.1 11.2 LTO CO (g) 9159 10932 LTO HC (g) 384 382 LTO NOx (g) 57 30
CR Fuel (Mission kg) 17 18 CR CO (Mission g) 7325 10108 CR HC (Mission g) 180 173 CR NOx (Mission g) 476 342
CR Fuel (kg/h) 49 43 CR CO (g/(h) 20929 24259 CR HC (g/h) 514 415 CR NOx (g/h) 1360 822
Taxi Time (Min.) 11 11 Take-off Time (Min.) 1 1 Climb Time (Min.) 3.5 3.5 Cruise Time (Min.) 21 25 Approach Time (Min.) 7.5 7.5

6) HBHFX (Carburated Engine Lyc O-320 Series)

6.a) HBHFX high accuracy in-flight m easurements: Installation of OBS2200

The FOCA low-cost in-flight measurement system described in Appendix 1 has some limitations for total HC and NO x and therefore, correction factors have to be applied, as described in Appendix 5. It was not clear, how good these corrections would work for the in-flight measurements, because calibration was only possible at ground level static condition s. Until then, no system could be found in the marked, which was portable, with a potential for inst allation in a small aircraft and which –at the same time - was showing emission certification accuracy. Through relations network and pure chance, HORIBATM company got to know about FOCA in-flight measurements and presented their po rtable emission measurement system (PEMS), originally designed for on-road high quality measurements of diesel trucks and cars. FOCA was interested to see whether the HORIBATM system woul d show comparable results to the low-cost system. HORIBATM was interested to know, whether their system (OBS2200) was able to operate in an aircraft, facing rather quick changes of ambient conditions. At th is time, the OBS2200 was not yet officially on the market. It was known from car measurements and tests in the Swiss alps, that the system would work at least down to an air pressure of about 850 hPa. A major difference in the measurement principle between the FOCA low-cost measurement system and the OBS2200 lies in the determination of mass flow (see Appendix 1). FOCA uses actual fuel flow meters (that have to be installed in the fuel li nes) and OBS2200 measures actual and ISA corrected exhaust volume flow. The HORIBATM exhaust flow me ter (which is a patented design) has to be installed in a straight part of t he exhaust tube of the engine. In a first step, the OBS2200 was used for ground static measurements of HBKEZ (see Appendix 3). The calculated fuel flow from exhaust flow and exhaust carbon content measurement (OBS2200) and the actual measured fuel flow in the fuel line were compared. Those measurements matched very well (within 1 to 3% difference). Former ground based measurements and calculated emission factors of HBKEZ could be compared to OBS2200 measurements. This was part of validation work for the results that were obtained with FOCA low-cost measurement system (Appendix 3). It would have been very useful to compare alsoReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern FOCA and HORIBATM in-flight measurements of HBKEZ and HBEYS. Unfortunately, there was no way for proper and safe installation of the HORIBATM exhaust flow meter on the wooden and plastic covered airframe of HBKEZ and HBEYS without drilling holes and altering the airframe structure. So FOCA was looking for another aircraft with similar engine and chose the AS02 (HBHFX). The installed engine, Lyc O-320-E2A is practically identical to the one installed in HBEYS, rated at 150 HP instead of 180 HP (HBEYS). The AS02 aircraft is a full metal des ign, very robust, main ly used for pilot schooland training. For noise reduction purposes, an additional muffler had been fitted and closer examination showed that the exhaust flow meter could be mounted instead of the muffler.

Picture 8: HB-HFX with original exhaust muffler (Gomolzig).

Moreover, the two large batteries, necessary for running the OBS2200 and the heated sampling line, could be installed below the seats, near the centre of gravity. However, zero fuel weight came close to maximum take-off weight which meant that planned flight time would be limited to half an hour per flight with a 45 minutes fuel reserve.

Details of the temporary major modification of HBHFX: - The exhaust sample line is much thicker (40 mm diameter) than the FOCA system line. So we screwed the line directly to the airframe, us ing aircraft clamps and existing screw holes. - The fixation of the exhaust probe system was a sheer replacement of the Gomolzig muffler by a stainless steel tube with the exhaust flow me ter between. The exhaust system replacing the Gomolzig muffler had exactly the same weight (3.6 kg). Exhaust flow was not hindered inside the tube. We had tested the installation during a one hour ground test, also at take off power, without anything becoming loose or falling o ff and without any noticeable drop in engine performance. During the ground test we also rolled on the runway, without taking off and the whole measurement system fully operating. - No existing aircraft system s were affected. Po wer supply was independent from aircraft.

Technical Influence

Limitations: - Vne = 120 MPHReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern - Max. Altitude 7000 ft QNH - Max. vertical acceleration = + 2g - Neg. vertical accelerations to be avoided
Cabin Safety:
- CO detector necessary - Emergency procedure: Emission measurement unit emergency stop button, closing down the whole system and valves immediately. - Gas main valves have to be closed manually.

Documents Affected:
- Flight Manual (AFM) (Including weight and balance for all possible test configurations)
Applicable Airworthiness Requirements
None, restricted admission for emission measurements

Installation documentation:

Exhaust system installed in lieu of the Gomolzig silencer. Stainless steel pipe with D = 60 mm, wall thickness 2.5 mm. Steel support welded, identical to holder of Gomolzig silencer, including rubber suspension. With flow meter in between. Mounting on the HBHFX. The flow meter between the supports is clamped to the pipe with a stainless steel muff. It can not fall, even if the rubber muffs were to be broken due to high temperature. The pipes have only a minimal spacing at the transition point underneath the muffs.

Detail of the flow meter. During the inflight measurements, a 0,5 mm aluminium plate is clamped between the metallic bridle and the rubber muff to prevent damaging. The connexions with the flow meter are welded. The measurement line is visible to the right on the picture. It is fixed on the fuselage by existing screws.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 BernBattery with plastic cover, specially created for the installation. Installation of both batteries underneath the front seats. They are fitting perfectlyin the place and can't slide. The lids protecting the batteries' contacts are open on the photo.

The back seat was taken off and a 2 cm thick wooden board was fixed on the fuselage. On the left side is the metallic support for the two little gas bottles. Batteries are mounted. Any possible upward movement of the batteries is prevented by the front seats once these are back in place.

Installation of the on board measurement system. The fixation is done with two clamps which are passing underneath the wooden board. The gas bottles (synth. air and He/H2) are fixed with 4 clamps to the metallic support. The pipe for He/H2 is made out of stainless steel with a reserve length of 1 m. The various links on the gas lines are tested with special gas leakage spray. A pressuredrop during measurement would be signalled by the system. Collector pipe is directly fixed to the fuselage by choke collars.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Collector pipe is fixed with choke collars directly screwed on the fuselage. The turbulences created by the collector pipe were investigated during the rolling test on runway in LSZB and did not interferewith the controls. In emergency, the canopy can be slide backward without hindrance.The airplane wears the inscription "Experimental" on both sides of the cockpit.

AFM Supplement

1. Description

Temporary installation of a measurement sy stem for in-flight emission measurements.

2. Operational Limits

V NE is reduced to 120 MPH

. Maximum pressure altitu de is limited to 7000ft.

Maximum vertical acceleration is limited to +2g. Negative vertical accelera tions shall be avoided.

Load planning: With a mass of 158 kg for Pilot and Expert, maximum ramp fuel is limited to 57 liter. Therefore, measurement flights ar e restricted to 30 minutes duration (plus reserve). (see point 6)

3. Emergency Procedures

Supplements to the primary AFM are: 1. Push emergency stop switch of OBS2200 (By doing so, all systems are cut off, all gas valves closed immediately) 2. The main valves of the two fuel gas bottles have to be closed manually by the measurement expert.

4. Normal Procedures

No change to basic AFM.

5. Performance

No change to basic AFM.

6. Mass and Balance

Basic empty mass, after - Removing of Gomolzig Silencer and back seat - Mounting of Exhaust Flow Meter and wooden board = 678 kgReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Mass and Centre of Gravity: Mass (kg) Moment (mkg) Remarks Basic empty 678 547 System (OBS 34kg, Gas 11kg) 45 85 Back seat position Batteries (2 peaces, 40 kg each) 80 110 Underneath front seats, position backend of pilot seats

Dry operating without crew 803 742 Lies within envelope (AFM B 5-2)

Configuration for first test flight Dry operating without crew 803 742 Pilot 79 80

Zero Fuel 882 822 Lies within envelope (AFM B 5-2)

Take-off mass for first test flight Dry operating without crew 803 742 Pilot 79 80 fuel (138 l) 100 85

982 907 Lies within envelope (AFM B 5-2)

Dry operating with full crew Dry operating without crew 803 742 Pilot + Expert 158 158

961 900 Lies within envelope (AFM B 5-2)

Take-off mass with full

crew Dry operating without crew 803 742 Pilot + Expert 158 158

fuel ( 53 l) 38 33 Max allowable ramp fuel = 57 Liter

999 933 Lies within envelope (AFM B 5-2)Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 7. System Description (see Installation Documentation)

Replacement of the Gomolzig silencer by an exhaus t flow meter (according picture documentation). Collector pipe fixed along fuselage, guided through the left cockpit window to the OBS2200 analyzer. Closed analyzer exhaust loop: Pumped exhaust samp le and water condensate are guided outside the cockpit. Two little gas bottles (He/H 2 , synthetic air) used for the analyzer are mounted on the metallic support on the wooden board. The measurement system prov ides an emergency shut down switch, which is positioned within reach of the measurement expert. The energy used for operating the measurement sy stem and the heated sampling line is provided independently from the electrical system of the aircraft. Two pressu re compensating dry batteries are fixed below the pilot and copilot seats. The batteries can not move in any direction and their contacts are covered. Monitoring of the cabin CO concentration is done with a CO-sensor (Quantum Eye) which is placed on the right hand side of the cockpit panel, clearly visible for the crew.

8. Maintenance

No change to basic AFM.

6.b) Real time emission mass determination during flight

CO, HC, NO x and CO 2 emission factors and the geographical coordinates from the GPS receiver have been displayed and recorded in real time during flight. The data recording interval was 1 second.

Picture 9: First departure of HB-HFX with OBS2200 fully operating.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern The flight pattern used for HBKEZ and KIA had to be shortened because of the limited fuel and therefore limited flight time:

- Departure at LSZB (Elevation 1673ft) - Continuous Climb to 5000ft (TO end at 4673ft) - Level off at 5000ft and maintain - Cruise phase with cruise lean at 5000ft - Descent and approach (L begin at 4673ft) - Landing at LSZB

Actual in- and outbound routes were chosen accordi ng to the visual approach chart (VAC), the meteorological and traffic situation.

Figure 129: Visualization of the flight track and the NO x mass from flight HBHFX 1537 (22.03.2006). Important phases of the flight and pilot operations, which affect emissions, are labelle d with yellow flags. The flight begins at Bern-Belp airport (LSZB) (right hand side of the picture). The aircraft is taking off from runway 32 and departure is flown outbound route Whiskey, leading first towards Bern (the capital of Switzerland). The climb continues in westerly direction. “End of LTO” marks the point, where th e aircraft reaches 3000ft above airport elevation. In this example, the coloured track indicates the amount of NO x mass flow in grams per second. A light blue and thin track means NOx mass emissions in the order of 0.005 grams/second, a red and large track means about 0.2 grams NOx per second. At top of climb, the aircraft is levelled off and accele rates for cruise. Cruise power is set and the air fuel mixture is adjusted to less rich conditions. With the lean ing procedure described in 1.c), NOx emissions get very high as peak EGT is reached (see r ed dot after “acceleration”). At the end of the adjustment (which is still a rich air/fuel mixture), NO x emissions stay rather high (orange track). This is the cruise phase, with the engine running more efficient, but with rather high NO x emissions. The orbit, which is shown on the left hand side of the picture, was only flown to demonstrate the wind situation. The airc raft was turning right with constant bank angle. The medium westerly wind produces a ground track with narrow turn, when the aircraft is turning towards the wind, and a wider turn, when the aircraft is flying with tail wind. That is why the ground track orbit is not a closed circle. Top of descent and the point where the aircraft is down at 3000ft above airport elevation are labelled accordingly. You can also see the effect of air /fuel mixture adjustments and th e use of carburetor heat on the NO x emissions during descent and approach. Wi th the air/fuel mixture enrichment, NO xemissions are reduced. At the end of downwind (right hand side of the picture), the NO x emissions get very low, as the power is very low and the mixture lever in the “full rich” position

.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Picture 10: HBHFX cockpit during measurement f light with cabin CO-detector (right hand side)

Picture 11: OBS2200 Laptop monitor duri ng measurement flight with HB-HFXat 2340 seconds after engine startup. The top line shows measured concentrations over time . At the bottom right, instantaneous values of the exhaust flow meter are displayed.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Table 10: Extract from data recording from 15:54:15 to 15:54:17 local time during take-off acceleration on the runway, showing the measured concentrations, sensor val ues and calculated values. (HBHFX, 1537, 22.03.2006)

FILLER_01 FILLER_02 ANALYZER_ V ANALYZER_ V ANALYZER_ V ANALYZER_ V ANALYZER_ V ANALYZER_ V

FILLER_03 absolute relative CO conc. CO2 conc. THC conc. NOx conc. H2O conc. A/F Alarm [s] [vol%] [vol%] [ppmC] [ppm] [vol%] 15:54:15 440 5.59 9.46 2078.00 396.00 11.37 12.66 15:54:16 441 5.69 9.38 2056.00 400.30 11.37 12.65 15:54:17 442 5.74 9.35 2041.00 394.00 11.37 12.64

SENSOR_01 SENSOR_02 SENSOR_03 SENSOR_04 SENSOR_05 SENSOR_06 GPS_01 GPS_02 GPSAV_01 Exh. Flow Exh. Temp. Exh. Press. Amb. Temp. Amb. Press. Amb. Humid. Latitude Longitude Altitude [m3/min] [degC] [kPa] [degC] [kPa] [%RH] [N/S] [W/E] [m] 5.65 491.22 97.77 12.98 94.56 61.92 N46.54.33.65 E7.30.10.656 508.90 5.55 507.67 97.71 13.00 94 .56 61.91 N46.54.33.99 4 E7.30.10.218 508.90 5.48 518.11 97.83 12.98 94 .56 61.89 N46.54.34.38 4 E7.30. 9.731 509.00

GPSAV_02 SENSOR_08 ANALYZER_ M ANALYZER_ M ANALYZER_ M ANALYZER_ M ANALYZER_ M ANALYZER_ M ANALYZER_MASS08 Velocity Battery CO mass CO2 mass THC mass NOx mass Fuel Power NOx corre. mass [km/h] [V] [g/s] [g/s] [g/s] [g/s] [g/s] [] [g/s] 46.00 22.83 6.13 16.30 0.11 0.07 8.27 129.96 0.07 51.50 22.83 6.13 15.88 0.11 0.07 8.13 127.81 0.07 57.00 22.95 6.10 15.62 0.11 0.07 8.03 126.25 0.06

NOx Mass (g/s) Emissions during Flight

46.88 46.89 46.9 46.91 46.92 46.93 46.94 46.95 46.96

7.1 7.15 7.2 7.25 7.3 7.35 7.4 7.45 7.5 7.55 LongitudeLatitude

Figure 130: NO x emissions during flight HBHFX 1537 (22.03.2006) , the same flight as shown in figure 129 but without geographical background information. With this illustration (“NO x worm”) the variation of NO xmass emissions during the flight can be seen very clearly. One “bubble” contains the NO xemissions integrated over 10 seconds flight time. The bubble size goes from around 0.05 to 2 grams NO x per 10 seconds.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern CO Mass Emissions during Flight

46.88 46.89 46.9 46.91 46.92 46.93 46.94 46.95 46.96

7.1 7.15 7.2 7.25 7.3 7.35 7.4 7.45 7.5 7.55
CO (g/s) Figure 131: CO emissions during flight HBHFX 1537 (22. 03.2006), the same flight as shown in figure 129 but without geographical background information. CO emissions are practically contrary to NO x : Very high during take-off and climb, lower during cruise and high during approach. The bubble size goes from around 9 to 70 (!) grams CO per 10 seconds.

Total HC Mass Emissions during Flight

46.88 46.89 46.9 46.91 46.92 46.93 46.94 46.95 46.96

7.1 7.15 7.2 7.25 7.3 7.35 7.4 7.45 7.5 7.55
Total HC (g/s)

Figure 132: Total HC emissions during f light HBHFX 1537 (22.03.2006), the sa me flight as shown in figure 129 but without geographical background information. HC emissi ons are particularly high during take-off and climb, lower during cruise and higher during approach. The bub ble size goes from around 0.4 to 1.2 grams HC per 10 seconds.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Fuel Consumption during Flight

46.88 46.89 46.9 46.91 46.92 46.93 46.94 46.95 46.96

7.1 7.15 7.2 7.25 7.3 7.35 7.4 7.45 7.5 7.55
Fuel (g/s)

Figure 133: Fuel flow during flight HBHFX 1537 (22.03.200 6), the same flight as shown in figure 129 but without geographical background information. The fuel flow is particularly high during take-off and climb, lower during cruise, stays practically the same during descent and is even increasing during approach! This can be explained by the fact, that according to the AFM, the mixture was se t to full rich conditions at the end of the approach check. The bubble size goes from 83 grams of fuel per 10 seconds at take-off, to 55 grams per 10 seconds during cruise (around 27 liters per hour), 56 grams per 10 seconds dur ing descent and 60 grams per 10 seconds in downwind before base and final turn. The final approach bubbl es represent 33 grams of fuel per 10 seconds.

6.c) OBS2200 confirms typical emission factors for Lycoming carbureted engines

Table 10: Mean emission factors for Lyc O-320-A3A. Fuel EF CO EF HC EF NOx EF CO2 [kg/s] [g/kg] [g/kg] [g/kg] [g/kg] TA mean 0.0013 690 16.0 1.6 2044 TO mean 0.0083 815 12.6 6.7 1857 CL mean 0.0079 837 15.1 6.9 1816 CR mean 0.0058 410 11.6 37.0 2498 AP mean 0.0048 696 13.7 19.4 2042
In-fight emission factors obtained with HBEYS and t he FOCA low-cost measur ement system are confirmed with HBHFX and OBS2200. In addition to that, the emission factor for CO 2 is calculated during the whole flights of HBHFX, in one second intervals. The low mean value of around 2 kg CO 2 per kg fuel, which is shown above, is not surprising, because of the low combustion efficiency with very high CO emission factors. The theoretical CO 2 emission factor for complete combustion and AVGAS100LL would be 3.17 kg CO 2 per kg fuel.

For LTO CO 2 calculations of typical aircraft piston eng ines, it is suggested to use 2 kg CO 2 per kg fuel instead of 3.17 kg CO 2 per kg fuel (see also 3.g), if CO emissions are counted separately.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 6.d) OBS2200 time trend chart and confirmati on of high HC emission factors at flight idle

Figure 134: This is the same flight as shown in section 6.b) (HBHFX, 1537, 22.03.06) displayed as time trend chart from OBS2200. On top of the figure, you can see the CO concentration in red and the CO 2 concentrations in blue colour. In the middle, NO x concentrations are given in yellow and total HC (THC) concentrations in green colour. The part on the bottom of the figure shows the fuel flow in orange and the flight vertical profile (GPS altitude) in violet colour. At about 200 seconds on the time scale there is a significant NO x , THC, CO and fuel flow peak. This is the moment, when the pilot performs the engine run-up with magneto check. The next peaks during taxi indicate a short engine RPM increase to accele rate the aircraft after a stop. At about 450 seconds, the engine goes to full power (maximum f uel flow) for take-off. During climb, NO xconcentrations decrease and CO concentrations increase due to decreasing air density and fixed mixture setting. At about 1050 seconds, the aircraft is levelled off and accelerated, which c an be seen on the increased fuel flow. At about 1100 seconds, power is reduced a nd the air/fuel mixture adjusted to less rich conditions. There is a significant increase in NO x and decrease in CO concentration, as shown in figures 130 and 131. THC is not reduced very much, which is also corresponding to FOCA previous results, obtained with the low-cost measur ement system. Top of descent is at about 1400 seconds. As explained before, the fuel flow does not decrease significantly, because t he mixture is set to richer conditions. Turning base and final approach begin at about 2000 seconds. Shortly before touch-down the engine is set to flight idle. At this point of time there is a drastic increase in THC concentration (black dart). This is a confirmation of the results obtain ed with FOCA low-cost meas urement system (see 3.c with explanations for this effect).Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Picture 12: Ready for airborne measurements

Picture 13: The HB-HFX project team33-05-003 Piston Engine Emissions_Swiss FOCA_Appendix3_070605_rit Federal Department of the Environment, Transport, Energy and Communications DETEC

Federal Office of Civil Aviation FOCA Aviation Policy and Strategy Environmental Affairs



# AIRCRAFT PISTON ENGINE EMISSIONS

Appendix 3: Power Settings and Procedures for Static Ground Measurements

Picture 1: Ground measurement (HB-KIA)

FOCA, CH-3003 Bern

Reference: 0 / 3/33/33-05-003 ECERT Contact person: Theo Rindlisbacher Tel. +41 31 325 93 76, Fax +41 31 325 92 12, theo.rindlisbacher@bazl.admin.ch This document has been released for publication by FOCA, Aviation Policy and Strategy, Director M. Zuckschwerdt, 11.06.2007Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 

## Contents Page 1. The problem of piston engine power definitions 3

2. Theoretical power calculation 3

3. Engine manifold pressure (MAP) and RPM for power determination 3

4. Correlation of fuel flow and propeller power 4

5. Adjustment of ground measurement power settings (Fuel Flow Method) 7

5.1 Step 1: Comparison of in-flight and static ground measurements of HBKEZ (example) 7

5.2 Step 2: Power setting methodology fo r static ground measurements 8

5.2.1 Determination of maximum fuel flow 8

5.2.2 Power settings other than maximum propeller power 9

5.3 Step 3: Application of the power setting methodology (step 2) 9

5.3.1 Comparison of ground and late r in-flight measurements 11

5.3.2 Adjustments to the fuel flow method for complex aircraft/engines 14
5.3.3 Temperature corrections for normally aspirated carburetted piston engines 15

6. Recommended ground measurement power setting procedures for emission tests 17

6.1 Selection of methodology 17

6.2 Procedure for determination of maximum fuel flow 17

6.2.1 Fuel flow calibration 17

6.2.2 Preparing the aircraft for a maximum fuel flow (and emission) measurement 18

6.3 Simple fuel flow method 19

6.3.1 Fuel flow for all modes 19

6.3.2 Recommended procedure 20

6.4 Combined MAP & fuel flow method 21

6.4.1 Preparations 21

6.4.2 Recommended procedure 22

7. Example for measurement documentation 23Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 1. The problem of piston engine power definitions

The term „horse power“ is not very well defined. G enerally, quite a variety of definitions and measurement methodologies are used which cause (at least) s light variations in the final numbers. As far as aircraft piston engines and propeller aircraft are co ncerned, the following terms could be identified:

- Brake horsepower (BHP): Strictly speaking, BHP is the me asure of an engine's horsepower without the loss in power caused by the gearbox, generator , water pump and other auxiliaries. The prefix "brake" refers to where the power is measured: at the engine's output shaft, as on an engine dynamometer. In aircraft piston engine manuals, po wer is often given in brake horsepower.

- Propeller horsepower : The horsepower that is delivered to the propeller. Most of the tested aircraft piston engines do not have a reduction gear or other auxiliaries that mi ght cause a significant loss of power through e.g. friction. Therefore, propeller ho rsepower is considered very near brake horse power under these circumstances.

- Rated horsepower : The normal maximum allowable power output of the aircraft piston engine. In power charts of aircraft piston engine manuals, this number is often equal to maximum brake horse power.

2. Theoretical power calculation (scientific SI-system 1 )

The power ( P ) which is delivered to the propeller is calculated by multiplying the torque ( M ) by the angular velocity ( 

### ω ) of the propeller shaft.



### ω ⋅ = M P (1)

Angular velocity and RPM ( 

### n ) have the following relationship:



### n ⋅ = π ω 2 (2) where 

### n is the number of revolutions per second.

Equation (2) in (1):



### n M P



### ⋅ ⋅ = π 2 (3)

At 2400 RPM (= 40.00 per second) and a torque of 400 Newtonmeter, the power equals about 100 Kilowatt (around 135 HP, depending on the definition).

This simple example shows that when knowing RPM and torque at the propeller shaft, engine propeller power is defined and can be determined exactly. Piston engine aircraft cockpits give information about engine RPM but do not usually have a torque indica tor. It would have been very costly to install a torque meter between engine shaft and propeller and to make this design airworthy for the in-flight tests. So, this straightforward way of determini ng propeller power for the emission measurements could not be followed.

3. Engine manifold pressure (MAP) and RPM for power determination

MAP indicates the absolute pressure of the air/f uel mixture between the throttle and the cylinder inlet valve. The measuring gauge has a sealed capsule a nd a capsule that is exposed to manifold pressure. It is normally calibrated to inches of mercury, where 29.92 In Hg is the standard pressure. At full throttle, and in the case of a normally aspirated engi ne, the MAP will indicate nearly the value of the absolute pressure of the ambient air. For such engines, at full throttle, MAP is always a little bit lower

1 SI = système international, kg, meter, second,...Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern than ambient air pressure due to losses in the i nduction system. If the throttle is reduced, the MAP decreases. If the engine has stopped, the MAP shows ambient absolute air pressure. A turbocharged engine achieves MAP above ambient pressure.

BHP (and propeller horsepower as described in a)) are almost directly related to MAP and engine RPM. The power output from a piston engine depends on both, engine RPM and the difference in pressure between the inside of the cylinders and the atmosphere outside the engine.

But one has to be careful: When climbing at const ant MAP and RPM, since the pressure in the manifold is constant, the reduction in ambient temperat ure increases the density of air in the manifold, resulting in a gradual increase in power. Constant MAP is maintained by opening the throttle during climb until the throttle is fully open. In other words: 23 In Hg is more power at 10 000 feet than it is at sea level. This has to be taken into account for ground measurement power settings, if they are based on MAP.

4. Correlation of fuel flow and propeller power

First of all, it must be noted, that for a given thru st, the fuel flow is NOT constant. The problem with piston engine thrust is that we get less thrust for the same fuel flow, as velocity is increased. (This is completely different from what happens in a jet). But:

Piston engine fuel flow is constant for a given amount of power . This was the starting point to look for the correlation between fuel flow and propeller power.

Table 1: Determination of propeller horsepower with H BEYS. Example sheet (source: “In flight Abgasmessung BAZL/CCUW”, R = rich, L = lean, FT = full throttle) HBEYS (DR400-180R) O-360-A3A Sensenich 76EM8S5-0-58 Gomolzig AVGAS100LL Stargas 898
Flights from 30.04.03, 13.08.03 and 21.08.03:

Flight Altitude QNH (ft) Date Nr. Ambient Air Pressure (hPa) Pressure Altitude (ft) Relative Humidity (%) (rounded) OAT (°C) "Powersetting" RPM (1/min) MAP (In Hg) Fuel Mixt. T Zyl. (°C) T Oil (°C) Fuel Flow (l/h) 4000 30.4. cruise 2400 20 R 200 80 35 4000 cruise 2500 23 R 205 80 49 2000 13.8. 2 952 1647 40 24 FT, acceler. 2410 27 R 210 80 56 2000 3 923 2430 40 23 FT, vy 2500 27 R 200 80 58 2000 5 905 2916 40 23 Reduced 2050 18 R 210 85 26 2000 7 928 2295 40 23 Approach 1580 14 R 180 80 14 2000 9 924 2403 40 23 FT, vy 2510 28 R 200 80 59 2000 11 907 2862 40 23 Reduced 2080 17 R 200 85 26 2000 13 928 2295 40 23 Approach 1520 12 R 170 80 10 4000 13.8. 3 855 4266 30 22 FT, vy 2500 25 R 210 92 57 4000 5 841 4644 30 21 Reduced 2070 17 R 200 95 28 4000 7 863 4050 30 21 Approach 1580 12 R 180 95 15 4000 9 859 4158 30 22 FT, vy 2530 25 L 210 85 40 4000 11 842 4617 30 21 Reduced 2050 16 L 220 98 20 4000 13 863 4050 30 21 Approach 1410 11 L 190 92 10 6000 13.8. 3 799 5778 30 20 FT, vy 2510 24 R 210 95 55 6000 5 781 6264 30 18 Reduced 2060 15 R 200 92 25 6000 7 803 5670 30 18 Approach 1440 10 R 180 85 8 6000 9 795 5886 30 20 FT, vy 2570 24 L 210 82 44 6000 11 780 6291 30 18 Reduced 2070 16 L 210 90 20 6000 13 801 5724 30 18 Approach 1490 10 L 180 82 11 4000 21.8. 2 866 3969 50 16 cruise 2440 20 R 210 75 38 4000 3 868 3915 50 16 cruise 2330 20 lambda =1 200 80 29 Measurement System Fuel Silencer Propeller Engine AircraftReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Propeller horsepower calculations were based on ambient air pressure values and hand written power curves from Textron/Lycoming. Figure 1 shows an example for the engine model O-360 A series, marvel carburettor and an engine cylinder compression ratio of 8.5 : 1.

Propeller Load Horsepower O-360 A Series Marvel Carburetor, Compression Ratio 8.5 : 1

40 65 90 115 140 165 190

1700 1900 2100 2300 2500 2700 Drehzahl [1/min]Brake Horsepower [hp]

Figure 1: Power Curve Lycoming Model O-360 A Series, Curve No. 10350-A (Textron/Lycoming) digitalized.

Propeller horsepower was assumed very near brake horsepower (see section a)). The calculated values for propeller horsepower, the measured fuel flow , MAP, ambient air pressure and flight mode were normalized and plotted together (figures 2 and 3).

HB-EYS, "mixture rich" ambient air pressure 781 bis 952 hPa

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

0 0.2 0.4 0.6 0.8 1
Share on maximum fuel flow Propeller horsepower

Manifold pressure (MAP)

RPM

Ambient air pressure

Flight mode (Final, Downwind, Cruise, Take-off) Linear (Propeller horsepower)

Figure 2: Normalized selected engine parameters in function of fuel flow (mixture rich ). Example: At 45% (=0.45) of maximum fuel flow, propeller power is at 40% (=0.4) , manifold pressure at 60% (=0.6) and engine RPM at 82% (=0.82) of the maximum value.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern HBEYS, mixture lean, ambient air pressure 780 to 868 hPa

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

0 0.2 0.4 0.6 0.8 1
Share on maximum fuel flow Propeller horsepower

Manifold pressure (MAP)

RPM

Ambient air pressure

Flight mode (Final, Downwind, Cruise, Take-off) Linear (Propeller horsepower)

Figure 3: Normalized selected engine parameters in function of fuel flow (mixture lean)
It can be seen from figures 2 and 3 that for the inve stigated engine, propeller horsepower and fuel flow correlate quite nicely (R 2 = 0.98), better than MAP or RPM. MAP is also directly related to ambient pressure and figure 2 shows that for a certain propeller power, the MAP is varying, although fuel flow a nd propeller horsepower are kept constant.

Fuel Flow versus Brake HP Analysis for Lyc IO-360 A Series @ Best Power Mixture

40 50 60 70 80 90 100

40 50 60 70 80 90 100
Percent of max. Brake HPPercent of max. Fuel Flow @ Best Power Mixture

2700 RPM Best Power 2600 RPM Best Power 2400 RPM Best Power 2200 RPM Best Power

Figure 4: In-flight fuel flow versus brake horsepo wer for different propeller adjustments (HBKEZ). Restrictions: Especially for low power settings below 40% of maximum fuel flow, significant deviations from the linear relationship can occur, because the piston engine efficiency is not a constant over the full power range. This can be seen in this figure, which shows an analysis for an injected aircraft piston engine with variable pitch propeller at best power mixture (HBKEZ, Appendix 2).Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Generally, the linear relationship between propeller ho rsepower and fuel flow at higher power settings could be reproduced, also for other engine-propeller combinations. Fuel flow was equally found useful to account for changes in ambient conditions. As ambient air pressure and air density decrease 2

, engine power decreases which is well translated into fuel flow decrease (at constant mixture setting). Therefore it is considered sufficiently accurate for those emission measurements, which are not intended for certification, to use fuel flow as t he major parameter for engine propeller horsepower settings.

The FOCA low cost emission measurement system (s ee Appendix 1 and 5) requires a direct fuel flow measurement. The fuel flow transducer, which has to be installed and calibrated on the aircraft, can therefore serve as propeller horsepo wer setting device at the same time.

5. Adjustment of ground measurement power settings (Fuel Flow Method)

FOCA tries to produce emission factors and fuel flow data for emission inventory purposes at the highest possible cost efficiency. Therefore, besides a low-cost measurement system with sufficient accuracy (as described in Appendix 1), a methodol ogy for static ground measurements is needed.

Primary goal: Find ground power settings that are re presentative of typical in-flight modes and emissions.

Results from in-flight emission tests (see Appendix 2) were used to select appropriate settings for ground measurements.

• Step 1: Take in-flight measurement results and try to reproduce them at static ground measurements.

• Step 2: Derive power setting methodology for static ground measurements

• Step 3: Take an aircraft that has not been measured in-flight, apply the power setting methodology (step 2) for static ground measurements, followed by in-flight measurements to validate the methodology.

5.1 Step 1: Comparison of in-flight and st atic ground measurements of HBKEZ (example)

Normalised Emission Factors HBKEZ, full throttle On the left: in-flight, On the right: static on ground measurement

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

Rel. EF CO 0.864 0.907 0.884 0.923 0.903 0.905 0.904 0.895 0.898 0.902 0.912 0.914 0.916 0.946 0.94 0.967 0.985 1 0.88 0.88 0.88 0.897 0.914 0.922 0.933 0.945
Rel. EF HC 0.669 0.827 0.74 0.972 0.743 0.83 0.788 0.738 0.771 0.745 0.767 0.796 0.791 1 0.802 0.964 0.987 0.997 0.7 0.662 0.649 0.774 0.799 0.859 0.775 0.808
Rel. EF NOx 1 0.882 0.745 0.537 0.482 0.482 0.472 0.399 0.369 0.519 0.514 0.495 0.474 0.478 0.582 0.412 0.333 0.304 0.628 0.609 0.587 0.69 0.706 0.817 0.761 0.837
Normalised Fuel Flow 0.972 0.958 0.986 0.986 0.986 0.986 0.986 1 1 1 0.986 0.986 0.986 0.972 0.944 0.958 0.944 0.93 0.93 0.93 0.93 0.944 0.972 0.986 0.986 0.972 TO 1673f TO 1673f TO 2300f TO 3000f TO 3500f TO 3500f TO 3500f TO 3500f TO 3500f TO 3500f TO 3500f TO 3500f TO 3500f TO 4000f TO 4300f TO 5000f TO 6000f TO 7000f TO Stand TO Stand TO Stand TO Stand TO Stand TO Stand TO Stand TO Stand

Figure 5: Comparison of emission factors for CO, HC and NO xfrom in-flight and static on ground tests at full throttle. Flights were performed up to a pressure alti tude of 7000ft and different ambient conditions. NO x is highest at ground level, CO and HC are highest at high altitude (mi xture full rich). Please note that all HC measurements were based on NDIR, not on FID.

2 Air density decrease: Mainly through increase of ambient air temperature. Humidity increase had little effectReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Normalised Emission Factors HBKEZ, Climb On the left: in-flight, On the right: static on ground measurement

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

Rel. EF CO 0.973 0.953 0.949 0.945 0.942 0.94 0.937 0.601 0.596 0.531 0.429 0.47 0.521 0.509 0.542 0.985 0.971 0.972 0.972 1 0.994 0.962 0.942 0.951 0.918 0.952
Rel. EF HC 0.759 0.787 0.813 0.814 0.852 0.857 0.865 0.492 0.518 0.664 0.498 0.392 0.4 0.692 0.701 0.79 1 0.768 0.76 0.792 0.794 0.838 0.682 0.678 0.714 0.68
Rel. EF NOx 0.091 0.07 0.07 0.072 0.07 0.071 0.071 0.526 0.54 0.787 0.849 1 0.807 0.896 0.799 0.078 0.088 0.086 0.083 0.095 0.095 0.084 0.074 0.068 0.085 0.07
Normalised Fuel Flow 1 0.983 1 0.983 1 1 1 0.8 0.8 0.767 0.767 0.767 0.767 0.75 0.75 0.867 0.85 0.85 0.85 0.85 0.867 0.883 0.983 0.983 0.883 0.983 CL 3000f CL 3500f CL 3500f CL 3500f CL 3500f CL 3500f CL 3500f CL 3500f CL 3500f CL 3500f CL 3500f CL 3600 CL 4500 CL 4500f CL 5500f CL Stand CL Stand CL Stand CL Stand CL Stand CL Stand CL Stand CL Stand CL Stand CL Stand CL Stand

Figure 6: Comparison of emission factors for CO, HC and NO x from in-flight and static on ground tests at climb. Flights were performed up to a pressure altitude of 5500 ft and different ambient conditions. The second set of inflight measurements starting from 3500ft to 5500ft (in the middle of the figure) has been measured with fuel mixture adjustment during climb (as described in Appendix 2, section 4.f)). All ground me asurements were performed with mixture full rich, with fuel flow guided power setting (suffix “alt”) and MAP guided power setting (“v3”). Please note that all HC measurements were based on NDIR, not on FID.

Normalised Emission Factors HBKEZ, Approach On the left: in-flight, On the right: static on ground measurement

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

Rel. EF CO 0.87 0.75 0.97 0.93 0.9 0.9 0.85 0.97 0.88 0.96 0.96 0.95 0.94 0.94 0.94 0.93 0.93 0.92 0.93 0.92 0.92 0.92 1 1 0.99 0.99 0.99 0.99 0.99 1 0.94 0.94 0.94 0.9
Rel. EF HC 0.75 0.79 1 0.88 0.72 0.73 0.75 0.89 0.74 0.83 0.76 0.78 0.78 0.79 0.8 0.83 0.78 0.79 0.77 0.77 0.81 0.8 0.91 0.79 0.79 0.84 0.86 0.8 0.88 0.79 0.76 0.74 0.77 0 .75
Rel. EF NOx 0.63 1 0 0.15 0.57 0.56 0.81 0.06 0.57 0.14 0.48 0.45 0.44 0.44 0.49 0.52 0.49 0.52 0.55 0.5 0.43 0.44 0.35 0.38 0.39 0.41 0.37 0.39 0.37 0.47 0.46 0.46 0.48 0. 5
Normalised Fuel Flow 0.68 0.49 0.36 0.19 0.96 0.91 1 0.6 0.45 0.91 0.68 0.79 0.77 0.74 0.74 0.72 0.7 0.77 0.72 0.79 0.79 0.77 0.66 0.66 0.66 0.66 0.66 0.66 0.68 0.72 0.66 0.66 0.66 0.77 AP 160 AP 200 AP 250 AP 260 AP 320 AP 320 AP 320 AP 320 AP 350 AP 350 AP 350 AP 350 AP 350 AP 350 AP 350 AP 350 AP 350 AP 350 AP 350 AP 350 AP 350 AP 350 AP Sta AP Sta AP Sta AP Sta AP Sta AP Sta AP Sta AP Sta AP Sta AP Sta AP Sta AP Sta

Figure 7: Comparison of emission factors for CO, HC and NO xfrom in-flight and static on ground tests at approach. Flights were performed from a pressure altitude of 3500ft and different ambient conditions. Flight measurements show significant variations coming from di fferent approach power settings. All ground measurements were performed with mixture full rich, with fuel flow guided power setting (suffix “alt”) and MAP guided power setting (suffix “v3”). Please note that all HC m easurements were based on NDIR, not on FID.

5.2 Step 2: Power setting methodology for static ground measurements

The first version of the methodology is solely based on fuel flow measurements for power settings at ground level.

5.2.1 Determination of maximum fuel flow

Generally, in order to get measurement results that ar e near standard sea level conditions, it is helpful if the test location is situated at low altitude airpor ts. Many airports in the Swiss Midlands are at about1500ft AMSL. If measurements are performed during cold days in winter and high ambient air pressure, the density altitude can be reduced to around 0 ft AMSL. Under these conditions a normally aspirated piston engine can produce its maximum rated propeller power and its maximum fuel flow. Moreover, measurements at low ambient temperatures have the advantage of better engine cooling and better prevention of “hot spots” inside the engine cowling during the static tests.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern For practical reasons, it was not possible for FOCA to do all the ground static tests at density altitudes around 0ft AMSL.

However, the maximum fuel flow at different ambient conditions between winter and summer showed relatively small differences. Although, high humidity also reduces air density, the significant portion of difference is generated by ambient air temperature variations (see also section 5.3.3). Additionally, part of the variation has to be attributed to the fuel flow transducers limited accuracy.

Examples for total variations (all flights, take-off and all ground measurements, full throttle, high RPM):

HBEYS 57 < max. fuel flow < 60 liters/hour HBKEZ 68 < max. fuel flow < 71 liters/hour

Keeping in mind that the emission measurements we re primarily designed for inventory purposes, reflecting operational conditions, the variation se emed acceptable. However, when ever possible, FOCA tried to measure normally aspirated piston eng ines at low density altitude, giving highest possible propeller power and fuel flow at full throttle. Of course, influence of ambient air pressure was not an issue for ground level static tests in the case of turbocharged engines. And:

There was no significant difference in maximum fuel flow at full throttle with the aircraft standing or with the aircraft accelerating on the runway.

For details of the measurement procedure, see section 6.

5.2.2 Power settings other than maximum propeller power

Table 2 was generated from in-flight and ground measur ement comparisons in order to match fuel flow and emissions obtained with ground measurements as good as possible to in-flight conditions. (Examples are given in figures 5 to 7 of section 5.1)

Table 2: Percent of maximum fuel flow for a ll selected aircraft modes (mixture “full rich”)

Mode % of maximum fuel flow Take off 100 Climb out 85 Cruise 65 Approach 45 Taxi AFM

The power setting for the different modes is established by adjusting the throttle to bring the indicated fuel flow to the corresponding % fuel flow calculat ed value. The taxi mode is treated differently: The engine is running at the recommended RPM for wa rm up according to AFM/engine operation manual. (Details in section 6)

Example: Max. fuel flow 70 liter / hour -> Clim b out setting 70 liter /hour * 0.85 = 60 liter / hour

5.3 Step 3: Application of the power setting methodology (step 2) for static ground measurements with an aircraft that has not been measu red in-flight, followed by in-flight measurements

The fuel flow methodology developed in step 2 was applied to the high performance piston engine aircraft HBKIA. It was considered demanding to ma tch static ground and in-flight measurements of such an aircraft, because of variabl e pitch propeller and an automatic ai r/fuel mixture adjustment of the engine (Appendix 2, Section 5). Therefore, this aircra ft was considered an interesting choice to test the fuel flow method.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Picture 2: Preparations for ground st atic emission measurements of HB-KIA

Picture 3: Preparations for ground st atic emission measurements of HB-KIAReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 5.3.1 Comparison of ground and later in-flight measurements

General remark: The in-flight tests following the grou nd static tests have been flown in very different ambient conditions, pressure altitudes and someti mes including individual operational behaviour of different pilots (Appendix 2). It could not be the aim to match a certain flight exactly with a certain ground measurement. The main goal was, to develop the methodology so far that emission factors (resulting from ground measurements) were in the range of values occurring in-flight. The following figures show emission factors and fuel flow in relation to their maximum values obtained within all the measurements. If the engine and the measurement syst em would perform absolutely identical at each flight, all in-flight pillars in the figure would be equal to 1. In reality, there are already significant differences within a certain flight mode. We consider t he methodology useful, if it is able to produce the same pillar height range as compared to the in-flight pillars for the different species and the fuel flow (see figures below).

Normalised Emission Factors HBKIA, full throttle On the left: static on ground, On the right: in-flight

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

Rel. EF CO 0.932 0.922 0.922 0.952 0.985 0.985 0.764 0.772 0.757 0.753 0.707 0.812 0.795 0.878 0.85 0.858 0.836 0.808 0.817 0.82 0.824 0.894 0.931 0.87 0.949 0.973 0.917
Rel. EF HC 0.461 0.491 0.491 0.637 0.53 0.53 0.791 0.797 0.836 0.837 0.807 0.74 0.782 0.584 0.557 0.77 1 0.563 0.484 0.484 0.529 0.412 0.534 0.478 0.484 0.5 0.546
Rel. EF NOx 0.354 0.504 0.569 0.558 0.463 0.463 0.927 0.907 0.932 0.943 1 0.823 0.686 0.756 0.753 0.676 0.719 0.778 0.824 0.812 0.805 0.724 0.565 0.675 0.662 0.531 0 .624
Normalised Fuel Flow 0.96 0.96 0.96 0.952 0.952 0.952 0.98 0.98 0.993 0.993 0.962 0.962 0.962 1 0.962 0.962 0.962 0.951 0.96 0.96 0.96 0.96 0.941 0.962 0.941 0.952 0.952 TO 0000 TO 0000 TO 0000 TO 0000 TO 0000 TO 0000 TO LSZG TO LSZG TO LSZG TO LSZG TO LSZG TO LSZG TO LSZG TO 1700 TO 1700 TO LSZB TO LSZB TO 2300 TO 3000 TO 3000 TO 3000 TO 3000 TO 3000 TO R 3000 TO R 3500 TO 4000 TO 4000

Figure 8: Comparison of normalized emission factors for ta ke-off power settings of all ground and in-flight measurements of HBKIA. The ground static results are represented by the first six sets of columns on the left. HC emissions were measured with NDIR (Appendix 1).



### Mean differences between ground an in-flight measurements HB-KIA, take-off

0 20 40 60 80 100 120 140

EF CO EF HC EF NOx Fuel Flow% Ground measurement In-flight measurement

Figure 9 : Relative difference in mean emission factor s between ground and in-flight measurements with indicated standard deviation for HB-KIA, take-off.

Discussion of take-off mode: The take-off fuel flow is stable within 5% for all measurements. CO emission factors tend to be higher at static conditions by around 10% wi th the exception of high altitude take-offs. NO x emission factors seem to be around 30% lowe r at static conditions. However, in absolute terms, the difference is in the order of gram s / kg fuel. HC emission factors have a tendency to be lower than in-flight at low altitudes.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Normalised Emission Factors HBKIA, climb mode On the left: static on ground, On the right: in-flight

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

Rel. EF CO 0.904 0.882 0.847 0.812 0.821 0.831 0.801 0.737 0.879 0.838 0.837 0.878 0.814 0.977 0.837 0.911 0.995 0.906 0.956 0.787 0.827 0.827 0.918 0.843 0.961 0. 933 0.968
Rel. EF HC 0.501 0.511 0.548 0.709 0.838 0.823 0.712 0.562 0.749 1 0.71 0.603 0.674 0.66 0.828 0.715 0.865 0.671 0.759 0.642 0.641 0.627 0.654 0.597 0.67 0.775 0.81 5
Rel. EF NOx 0.374 0.614 0.757 0.806 0.782 0.722 0.831 1 0.521 0.816 0.668 0.278 0.746 0.542 0.786 0.245 0.368 0.651 0.13 0.921 0.841 0.856 0.521 0.826 0.342 0.61 0.1 82
Normalised Fuel Flow 0.948 0.948 0.948 0.921 0.928 0.921 0.92 0.856 0.921 0.962 0.877 0.877 0.877 0.921 0.92 1 0.92 0.941 0.921 0.941 0.921 0.921 0.846 0.921 0.941 0.888 0.89 2 CL 0000 CL 0000 CL 0000 CL LSZG CL LSZG CL LSZG CL LSZG CL LSZG CL LSZG CL R CL LSZG CL LSZG CL LSZG CL 0000 CL R CL 2300 CL R CL 2300 CL 3000 CL 3000 CL 3000 CL 3000 CL R 3000 CL 3000 CL 3000 CL 3300 CL 4000

Figure 10: Comparison of normalized emission factors for climb mode of all ground an d in-flight measurements of HBKIA. The ground static resu lts are represented by the first three sets of column s on the left. HC emissions were measured with NDIR (Appendix 1).



### Mean differences between ground and in-flight measurements, HB-KIA, climb mode

0 20 40 60 80 100 120 140

EF CO EF HC EF NOx Fuel Flow% Ground measurement In-flight measurement

Figure 11: Relative difference in mean emission factors between ground and in-flight measurements with indicated standard deviation for HB-KIA, climb mode.
Discussion of climb mode: The variation of in-flight emission factors can be rather significant. In this example, this is especially the case for NO x emission factors. Nevertheless, matching of mean values for all in-flight emission factors to the ground meas urement values is considered acceptable with the exception of EF HC. It must be noted, that HC em issions had been measured with NDIR instead of FID (Appendix 1) only. Therefore, the composition of HC had an influence on the total value and this could be part of the difference.

Normalised Emission Factors HBKIA, approach mode On the left: static on ground, On the right: in-flight

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

Rel. EF CO 0.9225 0.8976 0.9133 0.9002 0.8941 0.8887 1 0.9614 0.7058 0.882 0.7082 0.854 0.8084 0.855 0.6775 0.7779 0.8039 0.8074 0.7743 0.7446 0.7591
Rel. EF HC 0.9157 0.9601 0.9228 0.9441 1 0.9962 0.9409 0.933 0.7817 0.7652 0.8024 0.74 0.9145 0.9502 0.7552 0.8021 0.8505 0.8075 0.7592 0.8507 0.7715
Rel. EF NOx 0.3176 0.3438 0.2592 0.2755 0.2857 0.3128 0.2315 0.2546 0.8716 0.4581 0.9936 0.5168 0.6037 0.404 1 0.6615 0.5878 0.5793 0.5062 0.5854 0.5489
Normalised Fuel Flow 0.9283 0.9283 0.9283 0.9283 0.9283 0.8491 0.8491 0.9245 0.9925 0.9849 0.9849 0.9849 0.8868 0.9245 0.9849 0.9849 1 0.9849 0.9623 0.9245 0.9434 AP 0000 AP 0000 AP 0000 AP 0000 AP 0000 AP 0000 AP 2400 AP 3000 AP 3000 AP 3000 AP 3000 AP 3000 AP 3200 AP 3200 AP 4000 AP 4000 AP 4000 AP 4000 AP 4500 AP 5000 AP 5000

Figure 12: Comparison of normalized emission factors fo r approach mode of ground an d in-flight measurements of HBKIA. The ground stat ic results are represented by the firs t six sets of columns on the left.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 

### Mean differences between ground and in-flight measurements, HB-KIA, approach mode

0 20 40 60 80 100 120 140

EF CO EF HC EF NOx Fuel Flow% Ground measurement In-flight measurement

Figure 13: Relative difference in mean emission factors between ground and in-flight measurements with indicated standard deviation for HB-KIA, approach mode.
Discussion of approach mode: NO x emission factors have the tendenc y to be significantly lower at ground tests than in flight. The contrary is true for CO and HC. This can be explained by the fact that the engine is running at a less rich air/fuel mixtur e during flight, most probably due to the automatic mixture adjustment in the engine (Appendix 2, section 5).

Normalised Emission Factors HBKIA, cruise mode On the left: static on ground, On the right: in-flight

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00

Rel. EF CO 0.97 0.94 0.94 0.81 0.80 0.79 0.79 0.81 0.66 1.00 0.71 0.87 0.64
Rel. EF HC 0.34 0.38 0.38 0.86 0.87 0.80 0.86 0.88 0.82 0.93 0.80 1.00 0.87
Rel. EF NOx 0.60 0.67 0.67 0.80 0.81 0.83 0.81 0.80 1.00 0.57 0.92 0.74 0.99
Normalised Fuel Flow 1.00 1.00 1.00 0.92 0.92 0.92 0.92 0.94 0.93 0.94 0.93 0.94 0.93 0 CR LR

GND 0 CR LR GND 0 CR LR GND CR 5500 CR 5500 CR 5500 CR 5500 CR 5500 CR 5500 CR 5500 CR 5500 CR 5500 CR 5500

Figure 14: Comparison of normalized emission factors fo r cruise mode of ground and in-flight measurements of HBKIA. The ground static resu lts are represented by the first three sets of column s on the left. HC emissions were measured with NDIR (Appendix 1). Mixture was set “rich of EGT peak”. (For details see section 6 )



### Mean differences between ground and in-flight measurements, HB-KIA, cruise mode

0 20 40 60 80 100 120 140

EF CO EF HC EF NOx Fuel Flow% Ground measurement In-flight measurement

Figure 15: Relative difference in mean emission factors between ground and in-flight measurements with indicated standard deviation for HB-KIA, approach mode.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Discussion of cruise mode: Cruise mode emission factors are extremely dependent on pilot’s choice for the mixture setting (Appendix 2). In-flight result s show the variation between settings of different pilots. It was found that the mean value for lambda (Appendix 5, section c)) for the standard mixture setting condition “rich of EGT peak” was around 0.93 to 0.95. In ground tests, after setting the power reference, the mixture setting was adjusted to this range of lambda (see section 6 for details). It is interesting to see, that although CO emission factors seem to be higher and NO x emission factors lower for the ground measurement, the HC emission fact ors are significantly lowe r. A similar situation can be seen in climb mode (figure 11). No l ogical explanation could be found, because HC emission factors should normally correlate with CO. Howe ver, as mentioned before, HC emissions had been measured with NDIR instead of FID (Appendix 1) only.
5.3.2 Adjustments to the fuel flow method for complex aircraft/engines

For aircraft equipped with manifold pressure gauge, the fuel flow method was combined with manifold pressure preset values (section 6.4). This pr ocedure further improved matching between ground and in-flight data. For the engine Teledyne/Continental IO-550-B of HB-KIA, the following ground based emission factors were obtained with this method:

Table 3: Fuel flow and mean emission factors for TCM IO-550-B (times are not relevant here)

The data presented in table 3 have been checked against the flights ECERT 57 and 64 (Appendix 2, sections 5.o) and 5.p)) in order to show a better ma tch with in-flight measured emission inventories.

Table 4: Comparison of emission results from in-fli ght full mission measurements (ECERT 57 and 64) and emission results based on the ground measurement data sheet (T able 3). For the calculation based on the data sheet, the average pilot 1 and pilot 2 times were used, as indicated on the bottom of the table. HBKIA Pilot 1 Pilot 2 Average Pilot 1 and 2 Based on Data Sheet LTO Fuel (kg) 11.1 11.2 11.1 11.8 LTO CO (g) 9159 10932 10046 11337 LTO HC (g) 384 382 382 218 LTO NOx (g) 57 30 43 40
CR Fuel (Mission kg) 17 18 17.5 19.1 CR CO (Mission g) 7325 10108 8716.5 9008 CR HC (Mission g) 180 173 176.5 103 CR NOx (Mission g) 476 342 409 438
CR Fuel (kg/h) 49 43 46 49.7 CR CO (g/(h) 20929 24259 22594 23498 CR HC (g/h) 514 415 464.5 268 CR NOx (g/h) 1360 822 1091 1142
Taxi Time (Min.) 11 11 11 11 Take-off Time (Min.) 1 1 1 1 Climb Time (Min.) 3.5 3.5 3.5 3.5 Cruise Time (Min.) 21 25 23 23 Approach Time (Min.) 7.5 7.5 7.5 7.5Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 

### Comparison of in-flight emission results for a full mission and emission results based on data sheet (HB-KIA)

0 20 40 60 80 100 120 140 160

L T

O

Fuel (

kg

)

L T

O

CO (

g) LT

O

HC (g)

L T

O

NO x

( g)

CR F

ue

l (

Mi

ss

io

n

kg

) CR CO (Mission g)

C

R

HC ( M

issio n g

)

CR

N

Ox (M i ss

i on g)

C

R

Fu e l (

k g/h) CR CO (g/(h)

C

R

HC ( g /h) CR NOx (g/h)% Average Pilot 1 and 2 Based on Data Sheet

Figure 16: Relative comparison of in-flight emission resu lts for a full mission and emission results based on the data sheet of table 3. Emission results bas ed on ground measured data for fuel, CO and NO xmatch the emissions of the selected flights by 3 to 8% difference. HC emissions, based on the data sh eet, are significantly lower (by 42%). It looks as if the differences in HC emissions between in-flight and ground measurements are systematic. It must be noted that the HC emissi on factors presented in table 3 were measured with a FID for total HC. Inflight measurement of HC could only be done with t he NDIR sensor and total HC had to be estimated (see Appendix 5). Standard deviations for in-fli ght emissions are only based on the tw o flights and are t herefore not statistically robust.

5.3.3 Temperature corrections for normally aspirated carburetted aircraft piston engines
The value of ambient air density (which is a functi on of ambient air temperature) can influence the air/fuel ratio in the carburettor significantly, much more than ambient humidity. Changing air/fuel ratio (and therefore changing lambda) changes the value of emission factors (even with all other factors remaining constant).
To compensate for temperature effects on emission factors for normally aspirated carburetted engines, two simple correction formulas are suggest ed, shifting the values to approximately 15°C outside air temperature (see Appendix 5). The correction repr esents present state of investigation and has not been developed any further.

Table 5: Generally, lambda gets lower at higher temperatur es (the engine runs „richer“). The taxi mode of this particular engine is behaving differently and is not repres entative for this class of engines. (Example from HBEYS, LycO-360, Marvel carburettor). Mode lambda 10.03.04 /1°C lambda 17.03.04 / 20°C cold minus warm

TO 0.708 0.704 0.004 TO 0.704 0.692 0.012 TO 0.701 0.689 0.012 CL 0.759 0.747 0.012 CL 0.762 0.743 0.019 CL 0.757 0.732 0.025 CR 0.827 0.813 0.014 CR 0.834 0.811 0.023 CR 0.827 0.806 0.021 AP 0.763 0.746 0.017 AP 0.766 0.748 0.018Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern AP 0.772 0.75 0.022 TA 1.338 1.371 -0.033 TA 1.333 1.359 -0.026 TA 1.343 1.386 -0.043 CR L 0.994 0.96 0.034 CR L 1.001 0.973 0.028 CR L 0.996 0.966 0.03

CO emission factor in function of ambient temperature and pressure at full throttle HB-EYS

1100 1200 1300

ModeEFCO (g/kg Fuel)

CO 1167 1183 1192 1225 1231 1247 1260 1259 1271 1279 1264 TO 1°C 946hPa TO 1°C 946hPa TO 1°C 946hPa TO 20°C 960hPa TO 20°C 960hPa TO 22°C 954hPa TO 22°C 954hPa TO 27°C 951hPa TO 30°C 951hPa TO 30°C 952hPa TO 30°C 952hPa

Figure 17: Example for temperature dominated EF CO in crease. Ambient pressure is QFE. Several measurements at the same temperature and QFE also show statistical differences resulting from measurement inaccuracies and engine performance fluctuations.

EF CO (T)

y = 3.1259x + 1176.5 R 2 = 0.9381

1160 1180 1200 1220 1240 1260 1280 1300

0 5 10 15 20 25 30 35 Ambient Air Temperature (°C)EF CO (g/kg Fuel)

Figure 18: Example of linear correction of EF CO in functi on of ambient air temperatur e. At 15°C, the EF CO is assumed to be 1223 g/kg fuel (HB-EYS). See Appendix 5, section f) for first order approximation formulas.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 6. Recommended ground measurement power setting procedures for emission tests

6.1 Selection of methodology

.

6.2 Procedure for determination of maximum fuel flow

6.2.1 Fuel flow calibration

The fuel flow measurement system, either already existing in the airc raft or installed for the measurements only, should be calibrated. Th is can normally only be done with f light testing, which requires to certify the installation. The fuel flow transducer used by FOCA (Appendix 1) is a certified design and can be installed in terms of a major aircraft modifi cation. Calibration of the transducer was achieved by

- Marking the position of the airc raft wheels before first refuelling. - Refuelling the aircraft with the fuel re aching a clearly defined optical reference. - Running the fuel flow system during flights, which last several hours. - Noting the time integrated fuel consumption indi cated by the fuel flow system until next refuelling. - Parking the aircraft with the same balance exac tly at the position where the previous refuelling took place. - Refuelling the aircraft to the prev iously defined optical reference. - Noting the relation between tanked amount of fuel and fuel flow system indicated fuel consumption. - Correcting the calibration factor according to the fuel flow transducer manual. After installation in the aircraft, the factory pre-calib ration value of the fuel flow transducer was often within 5% of the determined calibration value. Aircraft/Engine combination withinstalled and calibrated fuel flow transducer

Combined MAP & fuel flow method Section 6.4 Manifold pressure (MAP) gauge installed & MAP values existent in flight manual?

Simple fuel flow method Section 6.3 Determination of maximum fuel flow Section 6.2

NO YESReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 6.2.2 Preparing the aircraft for a maximu m fuel flow (and emission) measurement

As mentioned before, determination of maximum f uel flow (maximum propeller horsepower) of normally aspirated piston engines should be made at low density altitudes (low ambient air temperature and high ambient air pressure conditions). At a densit y altitude of 0 ft, the engine will behave similar to sea level due to a similar “weight of char ge” in the inlet. Practical recommendations:

• Wheels are secured with wheel chocks and fully braked by the pilot

• The measurement car is placed behind the main wing and in a sufficient distance to the tail wing, outside the propeller st ream and without obstructing t he aircraft, should the aircraft move forward.

• If the engine is equipped with a variable pitch propeller, the pitch setting is “high RPM”.

• The engine has to be perfectly warmed up.

• When going to full throttle, the aircraft is obs erved from outside with permanent radio contact between observer and pilot.

• Full throttle static conditions should generally not last more than one minute. Engine temperatures have to be observed carefully.

• This configuration can be used for the whole emission measurement

Picture 4: Determination of maximum fuel flow (static m easurement). The aircraft brakes are fully applied and the wheels secured by wheel choc ks.

After determination of maximum fuel flow, the engine is idling at the RPM which is suggested according to the aircraft flight manual (AFM), in order to cool down. During this time, the corresponding fuel flows, belonging to Climb out, Cruise (mixture rich ) and Approach can be calculated, as described in section 6.3 and 6.4 respectively.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Picture 5: Emission measurement of a Microlight (Swiss Ecolight) aircraft, normally used for glider towing. The power to weight ratio of this aircraft is such that the to wing rope is necessary to hold the aircraft in position during full throttle operation.

6.3 Simple fuel flow method

6.3.1 Fuel flow for all modes

All power settings are derived from the following table:

Table 6: Percent of maximum fuel flow for a ll selected aircraft modes (mixture “full rich”)

Mode % of maximum fuel flow Take off 100 Climb out 85 Cruise 65 Approach 45 Taxi AFM

The power setting for the different modes is established by adjusting the throttle to bring the indicated fuel flow to the corresponding % that has been calculated out of the maximum fuel flow.

Important:

• If the engine has manual mixture adjustments, all settings from table 6 correspond to mixture “full rich”.

• The taxi mode is treated differently: The engine is running at the recommended RPM for warm up according to the AFM/engine operation manual. Therefore, in order to measure taxi mode, the engine power is set by the recommended engi ne RPM and the resulting fuel flow is measured.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern • Cruise power for engines with manual mixture control: The initial power setting is adjusted with “mixture full rich” at 65% of maximum fuel flow , according to table 6. The final cruise setting (CRUISE LEAN) for the measurement will be obtained by leaning the mixture to lambda = 0.93 (see 5.3.1), while maintaining the RPM from the initial power setting. (It is recommended to use an exhaust emission measurement system , which is capable of computing the lambda values from measured concentrations in stantly, see more details in 6.3.2.)

Example : Max. fuel flow = 70 liter / hour

Î Climb out setting = 70 liter /hour * 0.85 = 60 liter / hour Î Cruise initial setting with mixture full rich = 46 liter / hour Î Cruise lean setting by leaning to lambda = 0.93 and maintaining RPM. Now, the fuel flow and emission concentrations are measured. Fuel fl ow is usually between 50 and 55% of maximum fuel flow and would result in around 37 liter / hour for this example Î Approach setting = 32 liter / hour Î Taxi setting = Taxi RPM according engine/a ircraft manual, usually around 7 liters / hour.

6.3.2 Recommended procedure

• We recommend going from high power to low power measurements, at least three measurements per power mode and a VHF radio communication between pilot and measurement team.

• The first measurement would be again the maximum fuel flow (max. power) measurement. At this occasion, the repetition of maximum fuel fl ow is a check for the first maximum fuel flow measurement.

• As soon as measured concentrations are stabl e, data are recorded. The pilot should note atleast fuel flow, RPM and engine temperatures during the measurements. (This can be a demanding task, with the airframe vibrating and hav ing to hold the throttle lever in its position.)

• After the measurements, the engine power is reduced to the recommended Taxi/Idle setting for cooling down.

• The measurement for climb out mode is prepa red and if necessary, measurement equipment is checked again for calibration and zero points.

• The pilot is then asked to set the throttle to reac h the climb out fuel flow value, calculated asdescribed above. As soon as the fuel flow reading is reported to be stable and measured concentrations are stable, the next data recording begi ns. The pilot should note at least fuel flow, RPM and engine temperatures during the measurements, as above.

• After measurement, the engine power is again reduced to the recommended Taxi/Idle setting for cooling down.

• This procedure is repeated down to taxi mode.

Cruise mode:

• As described in the example above, the measurement of the cruise mode is special, if the engine is equipped with a manual mixture adjustment. The pilot is asked to set the throttle to reach the cruise fuel flow value at mixtur e “full rich”, calculated as described above. As soon as the fuel flow reading is reported to be stable, the mixture is slowly leaned to lambda = 0.93. The corrections (“a bit richer, a bit leane r”) are transmitted from the measurement team to the pilot. The pilot has to make sure that RPM remain constant. If not, a throttle adjustment is necessary, followed by a mixture adjustment. At stable conditions, the data recording begins. The pilot should again note at least fuel flow, RPM and engine temperatures after stable conditions have been established, as mentioned above. The adjustment of static cruise powercan take more than one minute and therefore it is vital to observe engine temperatures carefully. Engine cylinder head temperatures are risi ng and there is less engine cooling, because the aircraft is not moving forward.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 6.4 Combined MAP & fuel flow method

More complex aircraft, especially those fitted wi th a variable pitch propeller or even constant speed propeller need a MAP gauge, which is generally a reasonable power indicator (see section 3). Engine parameter comparison of in-flight and ground measurements showed a potential for improvements by use of MAP. This method is referred as “V5” in FOCA piston engine emissions data sheets.

6.4.1 Preparations

From Airplane Operations Manual (AFM), typical MAP values for climb and cruise mode are recorded. We suggest a reference pressure altitude of sea level for climb mode and 5000ft for cruise mode.

Normally, no MAP values are given in the AFM for approach mode . From in-flight test we recommend a pre-selected mean value of 18 InHg and minimum 44% of maximum fuel flow at mixture “full rich” (Appendix 2).

The MAP values are input to the measurements, as shown with the orange fields in figure 19.

For take-off mode , no pre-selected MAP value is necessary. However, at full power with a normally aspirated engine, the value is an indication fo r ambient air pressure. Near sea level it can read around 29 InHg (Because of some inefficiencies in the engine induction system it does not fully reach the value of ambient air pressure with the engine running at full power). However, it is possible to get nearly 100% of rated maximum prope ller horsepower at 27 InHg too, if the air is cold and therefore dense enough. That is one reason, why we recommend doing the measurements at low altitude airports and cold ambient temp eratures (low density altitudes). With the variable pitch propeller, a pre-selected RPM value, normally the maximum allowed RPM for take-off, is necessary. This is indicated in the dark blue fields in figure 19. For all static ground measurements we recommend to leave propeller pitch at “high RPM”.

Taxi mode power is selected by RPM, according to AFM, as with the simple fuel flow method. RPM input is indicated in light blue in figure 19. MAP and fuel flow for taxi mode will result from measurements. US gal/h U S gal/h or l/h 1/min. 1/min. Max. FF R (AFM/Test) RPM TA RPM TO (AFM) In HG ft In HG ft MAP 65%CR (AFM) MAP 85% CL (AFM) In HG ft In HG ft MAP AP (Test) MAP TA (Test)

Meas. Nr. Mode/Mixt. MAP FF FF/ MFF (%) FF Check MAP RPM input RPM λ input λ 1 TO F.T. min. 95 2 TO F.T. min. 95 3 TO F.T. min. 95 4 CL 0.0 min.77 5 CL 0.0 min.77 6 CL 0.0 min.77 7 CR R 0.0 min. 51 8 CR R 0.0 min. 51 9 CR R 0.0 min. 51 10 CR L 0.0 min. 45 0.93 11 CR L 0.0 min. 45 0.93 12 CR L 0.0 min. 45 0.93 13 AP 0.0 min. 44 14 AP 0.0 min. 44 15 AP 0.0 min. 44 16 TA 0.0 min. 09 17 TA 0.0 min. 09 18 TA 0.0 min. 09 Figure 19: Engine data input and recording sheet us ed by FOCA. All entries from measurements go into the yellow coloured fields, brown fields are MAP predefined values, red fields the calculated relations of measured fuel flow to maximu m fuel flow and green fields contain minimum percentage of maximum fuel flow that should be ac hieved in the power setting (fuel flow check).Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 6.4.2 Recommended procedure

• We recommend going from high power to low power measurements with at least three measurements per power mode

• There should be a VHF radio communication bet ween the pilot and the measurement team.

• All measurements should be done with propeller pitch “high RPM”.

• The first measurement would be again the maximum fuel flow (max. power) measurement. At this occasion, the repetition of maximum fuel fl ow is a check for the first maximum fuel flow measurement.

• As soon as measured concentrations are stabl e, data are recorded. The pilot should note atleast fuel flow, RPM and engine temperatures during the measurements. (This can be a demanding task, with the airframe vibrating and hav ing to hold the throttle lever in its position.)

• After the measurements, the engine power is reduced to the recommended Taxi/Idle setting for cooling down.

• The measurement for climb out mode is prepa red and if necessary, measurement equipment is checked again for calibration and zero points.

• The pilot is then asked to set the throttle to reach the climb out MAP value. As soon as the MAP reading is reported to be stable and measured concentrations are stable, the next data recording begins. The pilot should note at l east fuel flow, RPM and engine temperatures during the measurements, as above. The fuel flow is transmitted to the measurement team and it is checked that the value fulf ills the minimum requirement (E.g. minimum 77% of the maximum fuel flow for climb, see figure 17, green colu mn). If the minimum fuel flow is not reached, throttle should be increased accordingly.

• After measurement, the engine power is again reduced to the recommended Taxi/Idle setting for cooling down.

• This procedure is repeated down to taxi mode.

Cruise mode:

• As described in the simple fuel flow method, the measurement of cruise mode following the climb mode is special, if the engine is equippe d with a manual mixture adjustment. The pilot is asked to set the throttle to reach the crui se MAP value at mixture “full rich”. As soon as the MAP, RPM and fuel flow reading are reported to be stable, the mixture is slowly leaned to lambda = 0.93. The corrections (“a bit richer, a bit leaner”) are transmitted from the measurement team to the pilot. The pilot has to make sure that RPM remain constant. If not, a throttle adjustment is necessary, followed by a mixture adjustment. At stable conditions, the data recording begins. The pilot should again note at least fuel flow, RPM and engine temperatures after stable conditions have been established, as mentioned above. Again, the adjustment of static cruise power can take more than one minute and therefore it is vital to observe engine temperatures carefully. Engine cylinder head temperat ures are usually rising and there is less engine cooling, because the aircraft is not moving forward.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 7. Example for measurement documentation

FOCA Groundmeasurement VERSION I.V5 Injected Eng./CS Prop. Meas. Nr. 78 A/C Reg. HB NCO

Aircraft Commander 114 Full Cycle

Engine Lyc IO-540-T4A5D Engine Hours 1817 Crew

Prop HC-C2YR-1 Fuel Injector standard PIC G. Staude Expert rit Silencer standard Rated P. (HP) 260 Warm up Block Time Flight Time Fuel AVGAS 100LL 13:20 14:05 Equipment Stargas 898, Mexa-1150 HFID Check Oil Temp.> 60°C

Day 13. Dez 06 Wind (° / kn) calm Dewpoint (°C) NIL Airport (ft) 1575 PA 1071 Begin LT 14.57 Uhr Air T (°C) 3 QNH (hPa) 1031 DA 9
US gal/h U S gal/h or l/h 1/min. 1/min. Max. FF R 85 (AFM/Test) RPM TA 1000 2700 RPM TO (AFM) In HG ft In HG ft MP 65% CR 22.5 SL (AFM) MP 85% CL 25 SL (AFM) In HG ft In HG ft MP AP 17.9 SL (Test) MP TA 11.8 (Test)

Meas. Nr. Mode/Mixt. % Power FF FF/ MFF (%) FF Check MP RPM input RPM λ input λ 1 TO F.T. 84 99 min. 95 27.2 2700 2620 0.749 2 TO F.T. 83 98 min. 95 27.2 2700 2620 0.749 3 TO F.T. 83 98 min. 95 27.2 2700 2620 0.749 4 CL 25.0 74 87 min.77 25 2590 0.76 5 CL 25.0 74 87 min.77 25 2590 0.759 6 CL 25.0 74 87 min.77 25 2590 0.757 7 CR R 22.5 61 72 min. 51 22.5 2480 0.773 8 CR R 22.5 61 72 min. 51 22.5 2480 0.773 9 CR R 22.5 61 72 min. 51 22.5 2480 0.771 10 CR L 22.5 49 58 min. 45 22.5 2350 0.93 0.947 11 CR L 22.5 49 58 min. 45 22.5 2350 0.93 0.95 12 CR L 22.5 49 58 min. 45 22.5 2350 0.93 0.943 13 AP 17.9 37 44 min. 44 18 2120 0.809 14 AP 17.9 37 44 min. 44 18 2120 0.811 15 AP 17.9 37 44 min. 44 18 2120 0.812 16 TA 11.8 12 14 min. 09 11.8 1000 1000 0.8 17 TA 11.8 12 14 min. 09 11.8 1000 990 0.794 18 TA 11.8 13 15 min. 09 11.8 1000 980 0.781
Figure 20: Practical example of the engine data input f ile for a Lyc IO-540 measurement (Aircraft HB-NCO). The file contains relevant aircraft and engine data, ambient co nditions and (in this case) predefined MAP values from AFM, measured fuel flow, MAP, RPM and lambda (compare to figure 19).

Stargas NDI Horiba FID Meas. Nr. Mode/Mixture FF CO (Vol. %) CO2 (Vol. %) HC (ppm) HC (ppmC) O2 (Vol. %) NO (ppm) Lambda Airpr. (hPa) Humidit y Air T (°C) 1 TO 84 9.027 8.68 170 2300 0.16 198 0.749 964 3 2 TO 83 8.954 8.79 136 2000 0.09 165 0.749 964 3 3 TO 83 8.994 8.79 136 2200 0.09 127 0.749 964 3 4 CL 74 8.528 8.85 164 2200 0.17 226 0.76 964 3 5 CL 74 8.522 8.92 145 2100 0.11 180 0.759 964 3 6 CL 74 8.571 8.85 137 2100 0.1 137 0.757 964 3 7 CR R 61 7.877 8.97 149 2400 0.15 251 0.773 964 3 8 CR R 61 7.877 8.97 149 2100 0.15 251 0.773 964 3 9 CR R 61 7.96 9.07 135 2100 0.1 216 0.771 964 3 10 CR L 49 2.058 12.63 64 1400 0.25 2191 0.947 964 3 11 CR L 49 1.945 12.64 57 1400 0.24 2296 0.95 964 3 12 CR L 49 2.116 12.61 62 1300 0.2 2066 0.943 964 3 13 AP 37 6.782 9.49 155 2500 0.35 364 0.809 964 3 14 AP 37 6.664 9.61 136 2200 0.3 389 0.811 964 3 15 AP 37 6.649 9.59 130 2300 0.31 389 0.812 964 3 16 TA 12 8.173 7.89 744 6400 1.77 42 0.8 964 3 17 TA 12 8.389 7.8 655 6600 1.7 39 0.794 964 3 18 TA 13 8.547 7.86 538 7000 1.34 40 0.781 964 3
Figure 21: Measured exhaust conc entrations (Measurement HB-NCO ). Data entries are checked for plausibility and variation (First measurement quality check).Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern NDIR FID Meas Nr. EI CO [g/kg] EI HC [g/kg] EI HC [g/kg] EI NOx [g/kg] LTO 1 1015.51348 18.0651925 14.8165072 3.041351843 TO 2 1006.90822 14.4248084 12.8788933 2.53347117 TO 3 1008.03576 14.3923887 14.1195705 1.94350651 TO 4 977.859871 17.7578546 14.4453432 3.538319905 CL 5 974.182434 15.6446866 13.746553 2.809509427 CL 6 980.950534 14.8000098 13.7629223 2.140895179 CL 7 930.226235 16.6431938 16.2298584 4.047256074 CR R 8 931.862325 16.6431938 14.2261031 4.054374423 CR R 9 931.68529 14.9187271 14.0750912 3.451986958 CR R 10 280.070402 8.20343786 10.9100221 40.71209449 CR L 11 266.544 7.35811704 10.9863414 42.96159664 CR L 12 287.420635 7.92668518 10.111635 38.31702853 CR L 13 828.306316 17.9240617 17.4843281 6.070071338 AP 14 815.276508 15.7268266 15.4123325 6.497985909 AP 15 814.676326 15.0659279 16.1373549 6.50785081 AP 16 987.375305 86.835632 44.2747876 0.692802229 TA 17 1004.68735 75.897227 45.2626966 0.637741339 TA 18 1008.17031 61.5586021 47.281799 0.644227734 TA Figure 22: Calculated emission factors (according Appendix 5)

Figures 23 and 24: Visualization of CO and HC emission factors for the measured engine modes. CO Emission Factors

0 200 400 600 800 1000 1200

ModeMass (g/kg Fuel)

CO 1016 1007 1008 977.9 974.2 981 930.2 931.9 931.7 280.1 266.5 287.4 828.3 815.3 814.7 987.4 1005 1008 TO TO TO CL CL CL CR R CR R CR R CR L CR L CR L AP AP AP TA TA TA

HC Emission Factors

0 10 20 30 40 50 60

ModeMass (g/kg Fuel)

HC NDIR 18.07 14.42 14.39 17.76 15.64 14.8 16.64 16.64 14.92 8.203 7.358 7.927 17.92 15.73 15.07 86.84 75.9 61.56
HC FID 14.82 12.88 14.12 14.45 13.75 13.76 16.23 14.23 14.08 10.91 10.99 10.11 17.48 15.41 16.14 44.27 45.26 47.28 TO TO TO CL CL CL CR R CR R CR R CR L CR L CR L AP AP AP TA TA TAReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Figure 25: Visualization of NO xemission factors for the measured engine modes. Visualization is used for a second measurement quality check.

Figures 26 and 27: Visualization of measured fuel fl ow and RPM. During subsequent measurements of one particular power mode, fuel flow and RPM should be maintained constant. NOx Emission Factors

0 5 10 15 20 25 30 35 40 45 50

ModeMass (g/kg Fuel)

NOx 3.0414 2.5335 1.9435 3.5383 2.8095 2.1409 4.0473 4.0544 3.452 40.712 42.962 38.317 6.0701 6.498 6.5079 0.6928 0.6377 0.6442 TO TO TO CL CL CL CR R CR R CR R CR L CR L CR L AP AP AP TA TA TA

Fuel Flow

0 10 20 30 40 50 60 70 80 90

ModeFuel Flow (l/h)

Fuel 84 83 83 74 74 74 61 61 61 49 49 49 37 37 37 12 12 13 TO TO TO CL CL CL CR R CR R CR R CR L CR L CR L AP AP AP TA TA TA

RPM

0 500 1000 1500 2000 2500 3000

ModeRPM (1/Min.)

RPM 2620 2620 2620 2590 2590 2590 2480 2480 2480 2350 2350 2350 2120 2120 2120 1000 990 980 TO TO TO CL CL CL CR R CR R CR R CR L CR L CR L AP AP AP TA TA TAReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Figures 28 and 29: Visualization of measured MAP and lambda. During subsequent measurements of one particular power mode, MAP should be maintained constant an d lambda should result in practically constant values. (Third check for measurement quality). For engines wi th manual air/fuel mixture adjustment, like the engine measured in this example, the CR L (cruise leaned) lambda value should be kept constant as well, with a value around 0.93, as described in 6. 3.1, 6.3.2 and 6.4.2. In th is example, the CR L lambda values vary between 0.943 and 0.95.



## Statistical Basis for Calculation

Number of Measurements per powersetting 

## 3

Factor for 90% Confidence Level (T-Test, Assumption: Normal Distribution) 

## 2.92 Figure 30: Before computing mean values per power mode , the statistical functions for determining a 90% confidence interval are defined. For this very small sample of only three measurements per power mode, a T-test is suggested. Manifold Pressure

0 5 10 15 20 25 30

ModeManifold Pressure (in Hg)

Man. Pr. 27.2 27.2 27.2 25 25 25 22.5 22.5 22.5 22.5 22.5 22.5 18 18 18 11.8 11.8 11.8 TO TO TO CL CL CL CR R CR R CR R CR L CR L CR L AP AP AP TA TA TA

Lambda

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

ModeLambda

Lambda 0.749 0.749 0.749 0.76 0.759 0.757 0.773 0.773 0.771 0.947 0.95 0.943 0.809 0.811 0.812 0.8 0.794 0.781 TO TO TO CL CL CL CR R CR R CR R CR L CR L CR L AP AP AP TA TA TAReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern TO Emp. Mean Emp. St.Dev. Mean stat. Error 90% CI Fuel Flow (kg/s) EI CO [g/kg] 1010.15 4.68 2.70 4.47 0.0167 EI HC [g/kg] 13.94 0.98 0.57 2.05 EI NOx [g/kg] 2.51 0.55 0.32 1.53

CL Emp. Mean Emp. St.Dev. Mean stat. Error 90% CI Fuel Flow (kg/s) EI CO [g/kg] 977.66 3.39 1.96 3.80 0.0148 EI HC [g/kg] 13.98 0.40 0.23 1.30 EI NOx [g/kg] 2.83 0.70 0.40 1.73

CR Emp. Mean Emp. St.Dev. Mean stat. Error 90% CI Fuel Flow (kg/s) EI CO [g/kg] 931.26 0.90 0.52 1.96 0.0122 EI HC [g/kg] 14.84 1.20 0.69 2.26 EI NOx [g/kg] 3.85 0.35 0.20 1.21

AP Emp. Mean Emp. St.Dev. Mean stat. Error 90% CI Fuel Flow (kg/s) EI CO [g/kg] 819.42 7.70 4.45 5.73 0.0074 EI HC [g/kg] 16.34 1.05 0.61 2.12 EI NOx [g/kg] 6.36 0.25 0.14 1.03

TA Emp. Mean Emp. St.Dev. Mean stat. Error 90% CI Fuel Flow (kg/s) EI CO [g/kg] 1000.08 11.14 6.43 6.89 0.0025 EI HC [g/kg] 45.61 1.53 0.88 2.56 EI NOx [g/kg] 0.66 0.03 0.02 0.36

CR L Emp. Mean Emp. St.Dev. Mean stat. Error 90% CI Fuel Flow (kg/s) EI CO [g/kg] 278.01 10.59 6.11 6.72 0.0098 EI HC [g/kg] 10.67 0.48 0.28 1.44 EI NOx [g/kg] 40.66 2.32 1.34 3.15

Figure 31: Calculation of empirical mean, empirical stand ard deviation, mean statistical error and 90% confidence interval based on T-test. Mean HC emission factors are only based on the FID values. The fuel flow in kg/s is calculated from fuel flow in litres/hour by using a fuel dens ity of 0.72 kg/litre, if actual density at 15°C is not known.



### Carbonmonoxide CO

0.00 200.00 400.00 600.00 800.00 1000.00 1200.00

TO CL CR AP TA CR L
ModeEF [g/kg Fuel]

Figure 32: Visualization of mean statistical error and 90% co nfidence interval (two bars with emission factor value for each power mode) for EF CO.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 

### Hydrocarbons HC

0.00 10.00 20.00 30.00 40.00 50.00 60.00

TO CL CR AP TA CR L
ModeEF [g/kg Fuel]

Figure 33: Visualization of mean statistical error and 90% co nfidence interval (two bars with emission factor value for each power mode) for EF HC (based on FID).



### Nitrous Oxydes NOx

0.00 10.00 20.00 30.00 40.00 50.00

TO CL CR AP TA CR L
ModeEF [g/kg Fuel]

Figure 34: Visualization of mean statistical error and 90% co nfidence interval (two bars with emission factor value for each power mode) for EF NO x . Please note the limitations for NO x measurements with the FOCA low-cost measurement system, as described in Appendix 1 and 5. Systematic errors are not included in this statistical analysis.

Picture 6: Documentation of the fuel flow transducer installation (in the middle of the picture). The orange wire leaving to the left is carrying the pulses from the transducer to the fuel flow indicator in the cockpit. This installation is NOT certified fo r in-flight operation.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Federal Office of Civil Aviation, Environmental Affairs ENGINE EXHAUST EMISSIONS MEASUREMENT PISTON ENGINES

ENGINE IDENT Lyc IO-540-T4A5D INJECTOR standard

UNIQUE ID NUMBER PF12 INJECTION NOZZLE

-

ENGINE TYPE 6Cyl. 4Stroke RATED POWER (Poo) (HP) 260 Air cooled PROPELLER TYPE HC-C2YR-1

DATA STATUS TEST ENGINE STATUS

x EMISSION INVENTORY NEWLY MANUFACTURED ENG. PRE-REGULATION x USED ENGINE CERTIFICATION DEDICATED TO PRODUCTION REVISED OTHER (SEE REMARKS)

MEASUREMET STATUS CURRENT ENGINE STATUS GROUND BASED FIXED PITCH PROP x IN PRODUCTION

x GROUND BASED VARIABLE PITCH PROP OUT OF PRODUCTION OUT OF SERVICE EMISSIONS STATUS DATA CORRECTED TO REFERENCE TEMPERATURE DATA CORRECTED TO REFERENCE (ANNEX 16 VOLUME II)
IV5 CALCULATION METHODOLOGY VERSION NUMBER

MEASURED DATA

MODE POWER SETTING (%) TIME (minutes) FUEL FLOW (kg/s) EI HC (g/kg) EI CO (g/kg) EI NOx (g/kg) PM (...) (...) TAKE-OFF 100 0.3 0.0167 13.9 1010 3 CLIMB OUT 85 2.5 0.0148 14.0 978 3 CRUISE 65 60 0.0122 14.8 931 4 APPROACH 45 3 0.0074 16.3 819 6 TAXI 12 12 0.0025 45.6 1000 1 CRUISE LEAN 65 60 0.0098 10.7 278 41 LTO TOTAL FUEL (kg) or EMISSIONS (g) 5.63 138 5341 17 CRUISE 1HOUR FUEL (kg) or EMISSIONS (g) 35.3 376 9808 1435
NUMBER OF TESTED ENGINES 1111 NUMBER OF TESTS 3333

ATMOSPHERIC CONDITIONS FUEL BAROMETER QNH (hPa) 1031 SPEC AVGAS 100LL TEMPERATURE (°C)) 3 HC C7H13 DEW POINT (°C)

- DENSITY ALTITUDE (ft) 9

MANUFACTURER: REFERENCE: TEST ORGANIZATION: FOCA 33-05-003.001 groundmeasurement78.injected. TEST LOCATION: LSPL constantspeed.IV5.1.HBNCO_061213_rit TEST DATES: 13. Dez 06 Expert: T. Rindlisbacher

REMARKS:

Figure 35: Final data sheet for Lyc IO-540-T4A5D as provided by FOCA for download.33-05-003 Piston Engine Emissions_Swiss FOCA_Appendix4_070605_rit Federal Department of the Environment, Transport, Energy and Communications DETEC

Federal Office of Civil Aviation FOCA Aviation Policy and Strategy Environmental Affairs



# AIRCRAFT PISTON ENGINE EMISSIONS

Appendix 4: Nanoparticle Measurements and Research for Cleaner AVGAS

Picture 1: Nanoparticle measurements of two differ ent aircraft piston engines fuelled with leaded and unleaded aviation gasoline. (Oberpfaffenhofen Airport (EDMO), Germany)

FOCA, CH-3003 Bern

Reference: 0 / 3/33/33-05-003 ECERT Contact person: Theo Rindlisbacher Tel. +41 31 325 93 76, Fax +41 31 325 92 12, theo.rindlisbacher@bazl.admin.ch This document has been released for publication by FOCA, Aviation Policy and Strategy, Director M. Zuckschwerdt, 11.06.2007Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 

### Contents Page 1. Background, motivation and project partners 3 1.1 Research programme 3 1.2 Research goals 3

2. General results for nanoparticle emissions of an aircraft gasoline engine, running 3 under rich air/fuel conditions (AVGAS 100 LL) 2.1 Preparations 3 2.2 SMPSTM system layout and descripti on for particle measurements 4
2.3 Results 6
2.4 Picture documentation of first non-vo latile nanoparticle measurements 9

3. Looking for particle emission improvem ents: First tests with unleaded 11 AVGAS (AVGAS 91/96 UL) 3. 1 Introduction and description of AVGAS 91/96 UL 11 3.2 Composition of measured AVGAS 100LL (560 mg Pb / liter) 11
3.3 Used aircraft 12
3.4 Results for HB-EYS 12
3.5 Conclusion for HB-EYS tests 13
3.6 Results for SE-KEI 13
3.7 Air/fuel mixture ratio for HB-EYS and SE-KEI 14
3.8 Discussion 15
3.9 Conclusions for AVGAS 91/96 UL 15

4. Change from SMPSTM to Engine Exhaust Particle SizerTM (EEPS 3090TM) system for 15 aircraft piston engine nanoparticle measurements
4.1 Introduction 15 4.2 EEPSTM system description 15 4.3 Application of EEPSTM for aircraft piston engine measurements 16
4.4 EEPSTM results 18
4.5 First conclusions for EEPSTM measurements 19

5. Research for AVGAS 100LL substitution and emission reduction 19
5.1 Test fuels 20
5.2 Test location 20
5.3 Used aircraft 20 5.4 Measurement systems 20 5.5. Power settings 21
5.6 Results 22
5.7 Discussion 31
5.8 First conclusions 32Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 

### 1. Background, motivation and project partners

The results for most in-flight tests documented in Appendix 2 showed engine operation at extremely rich air/fuel ratios. It is known that fuel rich conditions can form soot nanoparticles even in gasoline engines. Given the fact that standard aviation gasolin e is still leaded today, there was even more evidence for possible nanoparticle emissions.
Through the European AERONET network, Swiss FOCA started collaboration wi th the Institute of Combustion Technology of the German Aerospace C entre (DLR) in Stuttgart (Germany), recognizing their vast experience in nanoparticle measurement techniques and their high reputation in research of aero engine combustion processes. DLR Oberpfa ffenhofen (Germany) provided the necessary infrastructure for the aircraft on ground measurement s at Oberpfaffenhofen Airport (Germany).
At the same time and through AERONET as well, Swiss FOCA got to know Swedish HjelmcoTM Company, the only producer of lead free AVGAS worldwide, which is meeting ASTM D910 AVGAS specifications. The company can in 2007 claim more t han 26 years of lead free AVGAS flying experience in Sweden.
At a later step, collaboration started with German TSITM. The company provided their fast response engine exhaust particle sizer (EEPSTM) for in-field testing.
Research for cleaner, lead free AVGAS was done in Sw itzerland, at St. Stephan Airport (LSTS) in the Swiss Alps. The airport is a former military air port, privately owned and belongs to the company “prospective concepts”, which generously provided their infrastructure.

1.1 Research programme:
Step 1: Nanoparticle measurements of a gasoline piston aircraft engine running under rich air/fuel conditions, using standard leaded AVGAS (AVGAS 100LL)
Step 2: Nanoparticle measurements of gasoline piston aircraft engines running under rich air/fuel conditions, using AVGAS 100LL (leaded) and the Swedish AVGAS 91/96 UL (unleaded).
Step 3: Optimization of AVGAS 91/96 UL for higher k nocking margin and lowest possible emissions. Use of three aircraft (three differ ent engines) and ten different fuels.

1.2 Research goals:
1) Development and testing of a ground and in-f ield nanoparticle measurement methodology and measurement system. 2) Determination of nanoparticle emissions from aircraft piston engines. 3) Investigating possible emission im provements by use of unleaded AVGAS. 4) Use of knowledge for support, development and application of nanoparticle measurements also for jet engines. This goal is connected with international activities in ICAO CAEP 1 of Swiss FOCA.



### 2. General results for nanoparticle emi ssions of an aircraft gasoline engine, running under rich air/fuel conditions (AVGAS 100 LL)

2.1 Preparations
Step one of the research program started in April 2004. Measurements took place in Oberpfaffenhofen EDMO (Germany). The test aircraft was HB-KEZ whose engine (Lyc IO-360 series) had shown very rich combustion at mixture “full rich” co nditions (see Appendix 2, section 4d).

1 Commitee on Aviation Environmental Protection of the Intern ational Civil Aviation Organizati on, defining standards and recommended practices also for environment al aircraft/engine certification.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Gaseous emissions of HB-KEZ were measured with t he FOCA “low cost” system as described in Appendix 1. The methodology, which was used for the ground power settings, is described in Appendix 3, section 6.4.

Table 1: Measured CO and CO2 concentrations of HBKEZ on 13 th April 2004 for different standard power settings, as described in Appendix 3, sect ion 6.4. (TO = take-off, CL = climb, CR = cruise (rich), AP = approach, TA = taxi, CR L= cruise lean). Running on very rich air/fuel ratio is represented by extremely high CO concentrations and low CO2 concentrations. The m easurement numbers were assigne d for the particle measurements Meas. Nr. LTO CO (Vol. %) CO2 (Vol. %) - TO 12.506 6.99 6 CL 12.654 6.84 9 CR 12.674 6.82 12,11 AP 13.665 6.23 13,15 TA 10.536 8.06

18 CR L 1.42 13.63

2.2 SMPSTM system layout and description for particle measurements
Non-volatile nanoparticles are extremely small particles in the range of 10 to 500 nanometers (one hundred thousandth of a millimeter). There is growi ng concern about negative health effects from such particles. They are formed as a result of incomplete combustion. Some of them are potentially toxic and the small size allows them to easily enter t he human body deep into the lungs and to penetrate even into nerve cells and the brain. Measurement systems (including sampling processes) need to be sophisticated. General metrics are the size and number distribution (concentration). The first measurements were performed with a SM PSTM (Scanning Mobility Particle Sizer) System TSI 3080TM. Such a system classifies the particles first by their size. The classification is done with electrostatic forces in a so called DMA (Differential M obility Analyzer). When a certain size class is “filtered”, the number per volume (controlled by samp le flow and known dilution) is counted in a CPC (Condensation Particle Counter) (figure 1). The sc anning and counting through the size range of 10 to 500 nm usually can take several minutes. This is the measurement time per power mode.

Figure 1: System layout for nanopar ticle measurements with an electrostatic classifier and CPC. Explanations are given in the text. [TSITM] Diluter



## CPC Pure Nitrogen

Exhaust Probe Heated Line

DiluterReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Figure 2: Scheme of a CPC (Condensation Particle Co unter) used for counting the number of particles of a certain class of size (Example: TSITM Model 3775). [TSITM]

Picture 2: Stainless steel exhaust probe and heated sampling line (150°C). Total length 4.5 meters.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern For best measurement results, the sampling line has to be as straight and as short as possible. The DLR sampling line measures 4.5 meters only. The ma terial has to be stainless steel, heated to 150°C. Other materials like TeflonTM would absorb fractions of the particles. The exhaust is diluted by a heated DekatiTM diluter 1:10. Dilution air is nitrogen wi th a minimum quality of 4.5. For calibrating sampling line losses, DLR/Wahl has developed and pat ented a nanoparticle generator, which produces particles at defined and adjustable sizes. Calibration of sampling lines for size dependent losses has been carried out. However, absent such calibration in the international measurement community for the time being, it has not been applied to the meas urements, for reasons of comparison with other engine types and engine technology.

2.3 Results
Figure 3 shows a typical example of a particle size distribution from an aircraft gasoline piston engine, running on AVGAS 100LL (leaded fuel) under rich air/fuel ratio. For the different power modes,

• the mean diameter varied between 49 and 108 nm and

• the total concentration between 5.7 to 8.6 times 10 million particles per cubic centimeter. With an assumed specific density for soot of 1.2,

• the estimated mass concentration was around 10 000 micro grams per cubic meter

. (see picture 3)

The result for this gasoline engine is very comparable to the number-size distribution of a typical diesel passenger car engine without particle filter (see figure 4)!

Figure 3: Number-size distribution of HB-KEZ engine at approach mode. The mean particle diameter is around 100 nm and the total concentration is in th e order of 10 million particles per cubic centimeter.

Figure 4: Number-size distribution of a typical diesel passenger car (CDI) at 2000 RPM (increased idle) for comparison to the HB-KEZ measurements [C. Wahl/M. Kapernaum/DLR 2004l]Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern At lower power settings, exhaust has been pumped through sample cartridges at controlled flow rate for later HC speciation with HPLC (High Performa nce Liquid Chromatography). Pumping time usually was 2 minutes. Figure 5 shows the result for the m easurement of Carbonyls at approach mode. Thespeciation was obtained by analysis of the filter material with a gas chromatograph and mass spectrometer. Surprising was the amount of produced formaldehyd (see figure 6).

Figure 5: Detected carbonyls at approach mode. [C. Wahl/M. Kapernaum/DLR 2004]

Figure 6: Summary of carbonyl me asurements at climb mode (nr. 6), approach mode (nr. 12) and taxi mode (nr. 15). [C. Wahl/M. Kapernaum/DLR 2004]

Formaldehyde is dominating carbonyl emission s of the tested engine, running on AVGAS 100LL at standard very rich air/fuel mixture. Blindwert

ppb mg/kg Fuel ppb mg/kg Fuel ppb mg/kg Fuel ppb Formaldehyd 8337,48 92,49 6346,26 68,98 5867,59 68,24 21,29 Acetaldehyd 999,68 16,27 744,04 11,87 848,79 14,48 7,08 Propanal 639,90 13,73 532,20 11,19 707,13 15,91 0 Aceton 98,92 2,12 95,11 2,00 95,59 2,15 10,26 1-Buten-3-on 831,43 21,53 781,08 19,82 862,45 23,41 0 Methacrolein 213,53 5,53 184,10 4,67 198,74 5,40 0 Butanal 87,75 2,34 0 0 0 0 0 Benzaldehyd 347,12 13,61 297,51 11,43 333,92 13,72 0 o-Toluolaldehyd 162,52 7,21 141,79 6,17 136,54 6,35 0 m-Toluolaldehyd 294,13 13,06 260,23 11,32 281,54 13,10 0 p-Toluolaldehyd 79,40 3,52 80,54 3,50 71,96 3,75 0

Summe 12091,88 191,42 9462,85 150,95 9404,27 166,51 38,63 Nr. 6 Nr. 12 Nr. 15 0 10 20 30 40 50 60 70 0 50 100 150 200 250 300 3501,3-DinitrobenzeneDNPH 

### HPLC-chromatogram carbonylcompounds sample No. 12o-,m-,p-ToluenealdehydeBenzaldehydeMethacrolein1-Buten-3-oneAcetonePropionaldehydeAcetaldehydeFormaldehydeAcetyl-DNPHAbsorption (365 nm)



### t [min]Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Picture 3: Poster presented at the 8 th International ETH-Conference on Combustion Generated Particles, 16 th – 18 th August 2004, Zurich, Switzerland [C. Wahl/M. Kapernaum/DLR]Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 2.4 Picture documentation of first no n-volatile nanoparticle measurements

Picture 4: “In-field laboratory” at Oberpfaffenhofen Airport (EDMO) and candidate aircraft HB-KEZ.

Picture 5: SMPS (on the left) with DMA (the vertic al tube). The CPC is installed behind the Laptop.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Picture 6: This picture was taken during approach mode measurement. The SMPS is placed in the back compartment of the car (as shown in picture 5) and is brought as nearly as possible to the aircraft, for shortest possible sampling li ne and lowest possible particle losses.

Picture 7: Measurement team which performed – to our knowledge – the first successful measurement of non-volatile nanoparticles of an aircraft gasoline piston engine. From left to right: Manfred Kapernaum, Claus Wahl (both DLR Stuttgart), We rner Bula, Theo Rindlisbacher (both FOCA)Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 

### 3. Looking for particle emission impro vements: First tests with unleaded AVGAS (AVGAS 91/96 UL)
3. 1 Introduction and description of AVGAS 91/96 UL
Through AERONET network, FOCA came into contact with Lars Hjelmberg from Swedish HjelmcoTMOil company, which in 2007 is producing unleaded AVGAS since more than 26 years. Unleaded AVGAS has become a standard fuel in Sweden. Because it meets the AVGAS standard ASTM D910, no Supplemental Type Certificate (STC) for the aircraft is needed to use t hat fuel. It is important to notice, that the AVGAS specifications do not prescribe any minimum lead content. The only limitation for the use of the Swedish fuel comes from the lower av iation octane rating compared to the leaded AVGAS 100LL. The engine manufacturer Textron Lycoming has included AVGAS 91/96UL, which is Hjelmco,s second generation of unleaded AVGAS, as an approv ed alternate aviation gasoline for a large number of their engines already in the year 1995. The engi nes with type numbers are listed in service instruction No. SI 1070. Generally speaking, only highest pr essure ratio engines, especially turbocharged gasoline piston engines, can not use AVGAS 91/96 UL in their standard configuration.
Swiss FOCA had AVGAS 91/96 UL analyzed and some interesting properties were found: - The fuel is composed of a surprisingly low number of components compared to 100LL - The components are extremely pure - There is no benzene, no sulphur - There is no dye (the fuel is clear like water) - The fuel meets AVGAS specification ASTM D910
A hypothesis was set up, that the use of AVGAS 91/96 UL instead of AVGAS 100LL could significantly reduce particle emissions, both in terms of mass and in terms of number.
To test the hypothesis, two aircraft whose engine s are in the manufacturers list for running onunleaded AVGAS 91/96 UL, were selected. Both engines were run on AVGAS 100LL ( max lead content 560 mg / liter) and on unleaded 91/96 UL. DLR used the SMPS (as described in section 2), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX) for particle properties investigation. Additionally, DLR performed aldehyde tests (DNPH method). E ngine power for selected power modes (Take-off, Climb, Cruise, Approach and Taxi) was adjusted ac cording to the FOCA methodology for static on-ground tests, as de scribed in Appendix 3, sections 6.2 and 6.3.
3.2 Composition of measured AVGAS 100LL (max 560 mg Pb / liter)

Figure 7: Composition of measured AVGAS 100LL [C. Wahl/M. Kapernaum/DLR]Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 3.3 Used aircraft
HB-EYS Type: Robin DR400 SE-KEI Type: Piper PA28 Warrior II Owner: Swiss Confederation Owner: Hjelmco Oil, Sweden Engine: Lyc O-360 series, 180 HP Engine: Lyc O-320 series, 160 HP Carburetor Carburetor

3.4 Results for HB-EYS

Figure 8: Non-volatile particle number concent rations for AVGAS 100LL and 91/96 UL in function of propeller power (HB-EYS). [C. Wahl/M. Kapernaum/DLR]

Figure 9: Total non-volatile particle mass concentration for AVGAS 100LL and 91/96 UL in function of propeller power (HB-EYS) [C . Wahl/M. Kapernaum/DLR]Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Figure 10: Using EDX, both, Lead (Pb) and Bromi de (Br) containing particles from AVGAS 100LL exhaust could be identified (HB-EYS). In the picture on the left, the location of the spectrum 1 is indicated with a tag. [C Wahl/DLR].

3.5 Conclusion for HB-EYS tests
- AVGAS 100LL forms soot and lead bromide particles.- Besides lead additive, also bromides must be contained in AVGAS 100LL. (Bromides are actually used as scavenger, which should help to reduce lead deposits in the engine...) - Running HB-EYS on AVGAS 91/96 UL (lead free) still gives some lead bromides, which can be explained by the fact that the engine has b een running on leaded fuel for its whole life and there are huge lead deposits e.g in the oil pan of the engine.
The use of AVGAS 91/96 UL in HB-EYS gives a signif icant reduction in non-vo latile particle concentration and mass.

3.6 Results for SE-KEI

Figure 11: Non-volatile particle number concent rations for AVGAS 100LL and 91/96 UL in function of propeller power (SE-KEI). [C. Wahl/M. Kapernaum/DLR]Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Figure 12: Total non-volatile particle mass concentration for AVGAS 100LL and 91/96 UL in function of propeller power (SE-KEI) [C. Wahl/M. Kapernaum/DLR]

3.7 Air/fuel mixture ratio for HB-EYS and SE-KEI
Combustion quality is greatly influenced by the air/fuel mixture. The air/fuel mixtures at different power settings were recorded, using the FOCA analyzer described in Appendix 1.

0.6 0.7 0.8 0.9

1 1.1 1.2

TAKE- O

FF CL I MB O

UT CR UIS E APPRAOCH TAXI
CR UIS E L e anLambda Lyc O-360 Lyc O-320

Figure 13: Comparison of air/fuel mixture ( Lambda) between the measured Lyc O-360 (HB-EYS) and Lyc O-320 (SE-KEI) for different power modes during the AVGAS 100LL measurements. The engine Lyc O-360 of HB-EYS runs on a significa ntly richer air/fuel mixture than that of SE-KEI, with the exception of the taxi mode. For expl anation of lambda, see Appendix 5.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 3.8 Discussion
The carburetor system of SE-KEI is behaving differently from that of HB-EYS. Especially at high power, the engine of SE-KEI is running less rich than that of HB-EYS. Apart fr om different carburetor systems and tuning, the four blade pr opeller of SE-KEI might add to that effect, providing the air intake system with slightly increased manifold pressure. As a result of this different behavior, the shapes of the corresponding curves in figures 8 and 11, and in figures 9 and 12 respectively, are very different. However, in both cases, with use of AVGAS 91/ 96 UL, the mass and number concentrations are significantly reduced.

3.9 Conclusions for AVGAS 91/96 UL

• The use of AVGAS 91/96 UL gives a significant reduction in non- volatile particle concentration and mass, compared to AVGAS 100LL

• AVGAS 91/96 UL has no lead and no bromide emissions

.

• As described in the introduction, the highes t pressure ratio piston engines equipped with a RPM invariant ignition system are not allowed to use AVGAS 91/96 UL. Given the fact, that

• unleaded AVGAS has a significantly su perior environmental performance,

• unleaded AVGAS can increase engine operational sa fety (no spark fouling, no lead deposits, still tight aviation gasoline specs, mo re than 26 years Swedish experience)

• unleaded AVGAS is needed for state-of-the art engine management and the use of exhaust after treatment systems like catalysts, research and regulatory initiatives are necessa ry to further develop and promote AVGAS 91/96 UL as a full substitute for AVGAS 100LL (see section 5).

4. Change from SMPSTM to Engine Exhaust Pa rticle SizerTM (EEPS 3090TM) system for aircraft piston engine nanoparticle measurements

4.1 Introduction
The Engine Exhaust Particle SizerTM (TSI EEPS 3090TM) spectrometer is a fa st-response instrument that measures very low particle number concentratio ns in diluted exhaust. It offers a time resolution of 10 times per second, which makes it well-suited fo r dynamic and transient tests. It was developed for continuous measurement of entire test cycles. It m easures the size distribution and number concentration of engine exhaust particle emissions in the range from 5.6 to 560 nanometers. Compared to the SMPSTM, the TSI EEPS 3090TM system

• measures fast response (real time) particle number-size-distributions (+)

• significantly reduces engine running time (+)

• makes particle emissions in transient power settings visible (+)

• shows whether a certain power setti ng produces stable emissions (+)

• has a reduced size resolution and a reduced overall accuracy (-)

4.2 EEPSTM system description
[Source: TSITM]: The instrument draws a sample of t he exhaust flow into the inlet continuously. Particles are positively charged to a predictable le vel using a corona charger. Charged particles are then introduced to the measurement region near the cent er of a high-voltage electrode column and transported down the column surrounded by HEPA-filtered sheath air. A pos itive voltage is applied to the electrode and creates an electric field that repels t he positively charged particles outward according to their electrical mobility. (Figure 14) Charged particles strike the respective electrometer s and transfer their charge. A particle with higher electrical mobility strikes an electr ometer near the top; whereas, a parti cle with lower electrical mobility strikes an electrometer lower in the stack. This multiple-detector arrangement using highly sensitive electrometers allows for simultaneous concentrati on measurements of multiple particle sizes.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern The Model 3090 uses a real-time data inversion to deconvolute data. The inversion accounts for variability in particle charge, image charge, multiple volt ages on the center rod, and detection time to present a size distribution

Figure 14: EEPSTM flow schematic [TSITM]

4.3 Application of EEPSTM for airc raft piston engine measurements

Between 29 th March and 4 th April 2005, one year after the first non-volatile nanoparticle measurements in Oberpfaffenhofen, Germany, the same aircraft (HB-KEZ) with the same engine was measured again, this time with TSI EEPS 3090TM. The main goals were:

• Application test for in-field measurement with EEPSTM at low ambient temperatures

• Comparison to SMPSTM measurements

• Reproducibility test
The measurement arrangement and the sampling line were identical to the measurements of April 2004 (see section 2.2) with the exception that the SMPSTM was r eplaced by the EEPSTM and the dilution ratio adjusted to 1 : 100.
Ambient temperatures were as low as 9°C with a relative humidity of nearly 100%. At those ambient conditions, the EEPSTM was working in-field withou t any problems. However, measurements for comparison with SMPSTM results were made later, at dry ambient conditions.
The methodology, which was used for the ground power settings of the engine, was identical to the procedure of 2004 (as described in Appendix 3, section 6.4). In 2004, the SMPSTM measurements were limited to low power settings, due to the necessary sampling time of two minutes and the limited engine running time, with the aircraft standing on ground.
With EEPSTM it was possible to measure the high power settings as well: The measurement team could visually follow the stabilization of the number- size distribution on the PC screen. Engine running times at high power with the aircraft standing could be reduced to less than half a minute. ExhaustReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Picture 8: EEPSTM measurements with HB-KEZ at Oberpfaffenhofen (EDM O), Germany, March 2005

Picture 9: EEPSTM installed in the back Picture 10: Small ground power unit for compartment of a car. In-field supply of electricity.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 4.4 EEPSTM results

Figure 15: While the power setting is constant, the nu mber-size distributions show a constant shape in successive measurements at a rate of 10 times per second. (Proof for engine emission flow rate stability and combustion and measurement stability.)

Figure 16: Example of a number-siz e distribution of non-volatile pa rticles for approach mode of the HB-KEZ engine, measured with EEPSTM. With a mean diameter of 100 nm and an overall total concentration of 8 * 10 7 particles / cm3, the SMPSTM values for approach mode were confirmed.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Figure 17: EEPSTM measurement of a power cycle. Each slice represents the mean of 1 second measurement time. The left axis shows the measurement time, the x-axis in front the particle size and the z-axis on the right shows the particle number per cm3, as measured after dilution. The first set of number-size distributions on top of the figure belongs to the climb power setting, followed by cruise power (12.33.57), approach power ( 12.34.37) and taxi power setting (12.35.00). The approach power number-size distribution shown in figure 16 is tak en from this cycle and is marked in light blue.

4.5 First conclusions for EEPSTM measurements

• The system showed robustness with respect to low ambient temperatures and high relative humidity

• The results of the SMPSTM measurements hav e generally be confirmed for the different modes (see section 2.3, picture 3)

• For the first time, nanoparticle emissions duri ng transient aircraft piston engine power conditions could be observed.

• Engine running time was very short compared to SMPSTM measurements.

5. Research for AVGAS 100LL substitution and emission reduction
Following the conclusions from section 3.9, the Swedish producer of unleaded AVGAS, Hjelmco Oil, provided FOCA with a variety of different unleaded AVGAS fuels. The main goal was to find a lead free AVGAS that would have a similar high aviation octane rating like 100LL with superior emissions performance and economically feasible production cost s. In other words: The research is aimed to find an environmentally beneficial and safe full substitu te for AVGAS 100LL. Please note that aviation octane rating is not directly comparable to the research octane number (ROZ) used e.g. for car gasoline. An AVGAS 100 may have a ROZ well above 105. So, an avia tion fuel rated at “100” has a significantly higher octane rating than lead free car gasoline. The composition of the research fuels is known to DLR and FOCA but is part of a confidentiality agreement because this is propriet ary data. Therefore, the fuels from HjelmcoTM are just labeled “A” to “H” in this documentation.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 5.1 Test fuels
Fuel A: Standard unleaded AVGAS 91/96UL, as tested before (section 3). Fuel B to H: unleaded AVGAS which, in comparison to Fuel A, had one ore more components replaced and/or additives. Fuel I: Standard leaded AVGAS 100LL Fuel J: Standard MOGAS (lead free car gasoline with 98 ROZ, tested in Rotax engine)
Fuels D, F and G have the highest aviation octane ra ting of all tested unleaded fuels, with fuel G reaching nearly 100, so being comparable to AVGAS 100LL from that point of view.

5.2 Test location
The test location was St. Stephan (LSTS), a former mi litary Airport in the Swiss Alps. The infrastructure was generously provided by the pr ivate company “prospective concepts”.

Picture 11: Test location St. Stephan, Swiss Alps

5.3 Used aircraft
HB-EYS Type: Robin DR400 SE-KEI Type: Piper PA28 Warrior II Owner: Swiss Confederation Owner: Hjelmco Oil, Sweden Engine: Lyc O-360 series, 180 HP Engine: Lyc O-320 series, 160 HP Carburetor (Fuels A to I) Carburetor (Fuels A to I)
HB-WAD Type: Ikarus C-42 (Microlight/Ecolight) Owner: A. Liechti, Switzerland Engine: Rotax 912S, 100HP, Carburetor (Fuels A to C and J)
5.4 Measurement Systems
For gaseous emissions, the FOCA measurement s ystem as described in Appendix 1 was used. For particle emissions, the EEPSTM measurement system, described in section 4 of this appendix, wasused. Simultaneous measurement with both systems was made possible by two separate heated sampling lines. In addition, at lower power settings, exhaust has been pumped through sample cartridges at a controlled flow rate for later HC speciation (C arbonyl measurements). Pumping time usually was 2 minutes. The speciation was obtained by analysis ofthe sample cartridges with HPLC (High Performance Liquid Chromatography) in the DLR laboratory.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Picture 12: Gaseous emission analyzers in the white car on the left (FOCA), particle analyzers in the blue-green car on the right (DLR).
5.5 Power settings
Engine power for selected power modes (Take-off, Climb, Crui se, Approach and Taxi) was adjusted according to the FOCA methodology for static on-gro und tests, as described in Appendix 3, sections 6.2 and 6.3.It must be noted that t he airport elevation of 3274 ft AMSL (with the prevailing air density at the time of measurement) reduced the maximu m propeller power output of the tested engines to about 88%, compared to sea level standard conditions.

Picture 12: Measurement of SE-KEI engineReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 5.6 Results
As described in section 3.7, the two tested Lycomi ng engines have a quite different air/fuel mixturecharacteristic. The Rotax engine is running less rich at high power than the Lycoming engines. Therefore, if all three engines independently show the same trend, we consider this as a more general effect, not only valid for one particular aircraft piston engine. As far as particle emissions are concerned, we focus on the results for the SE-KEI engine. The re ason is given by the fa ct that the engine of HBEYS has been running on leaded fuel for its whole life (more than 1600 hours). Wi th a lot of lead deposits in the engine, significant amounts of parti cles have been detected in the exhaust even with unleaded fuel. The SE-KEI engine has the sa me basic design as the HB-EYS engine.
5.6.1 Ranking of the fuels in terms of emission factors for gaseous emissions
The resulting fuel consumption for a certain power se tting in terms of fuel mass did not differ significantly between the tested fuels. This means that measured differences in emission factors directly translate in different emission levels.
The figures 18, 19, 21 and 22 show the CO and HC emissions ranking of the tested fuels for full throttle and climb out mode of SE-KEI and HB-EYS. Tw o groups of fuel can be distinguished: A, E, I, H and C, D, B, G, F. The second group shows a sign ificant drop in CO and HC emissions. This effect is shown with both, the SE-KEI and the HB-EYS engine. For the lower CO and HC emissi ons group of fuel, one of the original components of the fuel A had been replaced by another.
The figures 20 and 23 show the CO and HC emissions ranking between fuels A, B, C and J, as tested with HB-WAD and the Rotax engine. The lowest emissions have been measured for fuel B and C, confirming the result and corresponding to fuel group two above. Fuel J (MOGAS) showed the lowest total HC emissions of the four fuels, but significant ly the highest carbonyl emissions, which is shown in tables 2 to 4.

For the HC speciation (Carbonyl measurements) , the following carbonyls have been detected:
Formaldehyde CH 2 O Acetaldehyde CH 3 CHO Propargylaldehyde CHCCHO Acetone CH 3 OCH 3 Propionaldehyde CH 3 CH 2 CHO Crotonaldehyde CH 3 CHCHCHO i-Butanale i-C 3 H 7 CHO Benzaldehyde C 6 H 5 CHO Methylglyoxal CH 3 COCHO o-Toluene – aldehyde CH 3 C 6 H 4 CHO m-Toluene – aldehyde CH 3 C 6 H 4 CHO p-Toluene – aldehyde CH 3 C 6 H 4 CHO

The ranking for the total carbonyl emissions has been analyzed for different power settings (see examples in tables 2 to 4). A representative ranking is given below. It is given with falling total carbonyl emissions from left to right:

• SE-KEI (no carbonyl measurement for fuel B)
F, G, D, C (first group) and H, A, E, I (second group)

• HB-EYS
B, D, C, F, G (first group) a nd E, H, A, I (second group)

• HB-WAD
J (MOGAS), B, C (first group) and A (second group)
Interestingly, the fuels with the lowest CO and lo west total HC emissions produce the highest total carbonyl emissions. In contrast, the (leaded) AVG AS 100LL produces the lowest total carbonyl emissions.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Relative Comparison of CO emission factors for different fuels (SE-KEI, St. Stephan, Switzerland, May 2006)

0 20 40 60 80 100

FUEL A FUEL E FUEL I FUEL H FUEL C FUEL D FUEL B FUEL G FUEL F F.T. / CL

Figure 18: Ranking of the CO emission factors for the tested fuels (SE-KEI engine in climb out mode/full throttle). AVGAS 100LL (Fuel I) is set to 100%.

Relative Comparison of CO emission factors for different fuels (HBEYS, St. Stephan, Switzerland, May 2006)

0 10 20 30 40 50 60 70 80 90 100

FUEL A FUEL E FUEL I FUEL H FUEL C FUEL D FUEL B FUEL G FUEL F F.T. / CL

Figure 19: Ranking of the CO emission factors for the tested fuels (HB-EYS engine in climb out mode/full throttle). AVGAS 100LL (Fuel I) is set to 100%.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Relative Comparison of CO emission factors for different fuels (HB-WAD, St. Stephan, Switzerland, June 2006)

0 20 40 60 80 100 120

FUEL A FUEL J FUEL B FUEL C F.T. / CL

Figure 20: Ranking of the CO emis sion factors for the tested fuels A, B, C and J with the ROTAX engine at climb out/full throttle setting. MOGAS (car gasoline, fuel J) is set to 100%.

Relative Comparison of HC emission factors for different fuels (SE-KEI, St. Stephan, Switzerland, May 2006)

0 20 40 60 80 100

FUEL I FUEL A FUEL E FUEL H FUEL D FUEL B FUEL F FUEL C FUEL G F.T. / CL

Figure 21: Ranking of the HC em ission factors for the tested f uels (SE-KEI engine in climb out mode/full throttle). AVGAS 100LL (Fuel I) is set to 100%.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Relative Comparison of HC emission factors for different fuels (HBEYS, St. Stephan, Switzerland, May 2006)

0 10 20 30 40 50 60 70 80 90 100

FUEL I FUEL A FUEL E FUEL H FUEL D FUEL B FUEL F FUEL C FUEL G F.T. / CL

Figure 22: Ranking of the HC emission factors for the tested fuels (HB-EYS engine in climb out mode/full throttle). AVGAS 100LL (Fuel I) is set to 100%.

Relative Comparison of HC emission factors for different fuels (HBWAD, St. Stephan, Switzerland, June 2006)

0 20 40 60 80 100 120

FUEL A FUEL C FUEL B FUEL J F.T. / CL

Figure 23: Ranking of the HC emis sion factors for the tested fuels A, B, C and J with the ROTAX engine at climb out/full throttle setting. MOGAS (car gasoline, fuel J) is set to 100%.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Table 2: Carbonyl emission fact ors for fuel A, B, C and J (MOGAS). Results for approach mode (HBWAD).[DLR C. Wahl/M. Kapernaum]
Approach mode Carbonyls Fuel J Fuel C Fuel B Fuel A

mg/kg Fuel mg/kg Fuel mg/kg Fuel mg/kg Fuel Formaldehyde 338.25 269.39 290.64 282.20 Acetaldehyde 44.95 97.56 83.22 49.41 Propargylaldehyde 4.55 4.52 5.43 2.20 Acrolein 34.33 34.83 32.66 22.67 Propanaldehyde 2.61 0.79 0.81 3.56 i-Butanaldehyde 24.46 13.04 12.21 15.36 Benzaldehyde 79.70 7.95 8.26 72.43 Methacrolein 69.24 145.73 101.76 69.64 o-Toluolaldehyde 19.709 0 0 2.48 p-Toluolaldehyde 43.42 0 0 1.37 m-Toluolaldehyde 0 0 0 2.73 2,5-Dimethylbenzaldehyde 13.586 000 3,4-Dimethylbenzaldehyde 23.059 000 2,4-Dimethylbenzaldehyde 24.297 000

Sum 722.16 573.82 534.98 524.05

Table 3: Carbonyl emission factors for fuel A, B, C and J (MOGAS). Results for cruise mode (HBWAD). [DLR C. Wahl/ M. Kapernaum]
Cruise 65% power Carbonyls Fuel J Fuel C Fuel B Fuel A

mg/kg Fuel mg/kg Fuel mg/kg Fuel mg/kg Fuel Formaldehyde 306.36 261.48 288.23 269.60 Acetaldehyde 55.62 103.62 96.84 36.69 Propargylaldehyde 3.65 2.50 2.75 1.29 Acrolein 23.42 23.34 22.38 16.15 Propanaldehyde 3.89 0.94 1.44 2.55 i-Butanaldehyde 28.53 9.56 9.38 0 Benzaldehyde 89.38 5.34 9.60 66.84 Methacrolein 82.01 92.48 88.73 60.57 o-Toluolaldehyde 21.90 0 0 1.45 p-Toluolaldehyde 17.97 0 0 1.60 m-Toluolaldehyde 34.57 0 0 2.79 2,5-Dimethylbenzaldehyde 15.97 0 0 0 3,4-Dimethylbenzaldehyde 26.55 0 0 0 2,4-Dimethylbenzaldehyde 28.34 0 0 0

Sum 738.14 499.25 519.35 459.51Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Table 4: Carbonyl emission factors for fuel A, B, C and J (MOGAS). Results for climb mode/full throttle (HBWAD) [DLR C. Wahl/ M. Kapernaum]
Climb/Full throttle Carbonyls Fuel J Fuel C Fuel B Fuel A

mg/kg Fuel mg/kg Fuel mg/kg Fuel mg/kg Fuel Formaldehyde 389.16 344.79 386.22 230.63 Acetaldehyde 71.34 220.80 234.52 39.41 Propargylaldehyde 4.02 2.09 2.92 1.37 Acrolein 55.55 74.15 69.53 20.55 Propanaldehyde 7.49 3.26 2.46 0.71 i-Butanaldehyde 15.43 9.88 10.60 30.76 Benzaldehyde 130.85 15.99 25.70 62.24 Methacrolein 142.81 154.95 154.60 0 o-Toluolaldehyde 29.67 0 0 2.67 p-Toluolaldehyde 71.01 0 0 1.74 m-Toluolaldehyde 0.00 0 0 2.74 2,5-Dimethylbenzaldehyde 22.06 0 0 0 3,4-Dimethylbenzaldehyde 37.57 0 0 0 2,4-Dimethylbenzaldehyde 41.44 0 0 0

Sum 1018.39 825.91 886.56 392.81

The figures 24, 25 and 26 show the NOx emissions ranking of the tested fuels. The two groups of fuels mentioned for the CO and HC emissions ranking are confirmed with all engines, but this time the ranking of the fuels is the other way round, with MOGAS and the C, D, B, G, F fuels producing the highest NOx emissions.

Relative Comparison of NOx emission factors for different fuels (SE-KEI, St. Stephan, Switzerland, May 2006)

0 50 100 150 200

FUEL F FUEL G FUEL B FUEL D FUEL C FUEL H FUEL E FUEL I FUEL A F.T. / CL

Figure 24: Ranking of the NOx emission factors for the tested fuels (SE-KEI engine in climb out mode/full throttle). AVGAS 100LL (Fuel I) is set to 100%.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern Relative Comparison of NOx emission factors for different fuels (HBEYS, St. Stephan, Switzerland, May 2006)

0 20 40 60 80 100 120 140

FUEL F FUEL G FUEL B FUEL D FUEL C FUEL H FUEL E FUEL I FUEL A F.T. / CL

Figure 25: Ranking of the NOx em ission factors for the tested fuels (HB-EYS engine in climb out mode/full throttle). AVGAS 100LL (Fuel I) is set to 100%.

Relative Comparison of NOx emission factors for diffe rent fuels (HB-WAD, St. Stephan, Switzerland, June 2006)

0 10 20 30 40 50 60 70 80 90 100

FUEL J FUEL B FUEL C FUEL A F.T. / CL

Figure 26: Ranking of the NOx emission factors fo r the tested fuels A, B, C and J with the ROTAX engine at climb out/full throttle setting. MOGAS (car gasoline, fuel J) is set to 100%.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 5.6.2 Ranking of the fuels in terms of particle emissions

0 10 20 30 40 50 60 70 80 90 100 0 1x10 8 2x10 8 3x10 8 4x10 8 5x10 8 

### SE

Fuel A Fuel B Fuel C Fuel D Fuel E Fuel F Fuel G Fuel H Fuel I# / cm3



### Power %

Figure 24: Particle number concentration for the diffe rent test fuels (SE-KEI engine) in function of propeller power. [DLR, C. Wahl, M. Kapernaum]

0 10 20 30 40 50 60 70 80 90 100 0 1x10 15 2x10 15 3x10 15 4x10 15 5x10 15 6x10 15 

### SE

Fuel A Fuel B Fuel C Fuel D Fuel E Fuel F Fuel G Fuel H Fuel IEI Soot [# /kg Fuel]



### Power %

Figure 25: Emission factor for the num ber of soot particles per kg fuel for the different test fuels (SEKEI engine) in function of propeller power. [DLR, C. Wahl, M. Kapernaum]Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 0 20 40 60 80 100 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 

### SE

Fuel A Fuel B Fuel C Fuel D Fuel E Fuel F Fuel G Fuel H Fuel IGeometric Mean [nm]



### Power %

Figure 26: Geometric mean diameter of emitted nanop articles for the different test fuels (SE-KEI engine) in function of propeller pow er. [DLR, C. Wahl, M. Kapernaum]

0 10 20 30 40 50 60 70 80 90 100 0 1 2 3 4 5 6 7 8 9 

### SE

Fuel A Fuel B Fuel C Fuel D Fuel E Fuel F Fuel G Fuel H Fuel Img/m3



### Power %

Figure 27: Emitted particle mass per exhaust volume for the different test fuels (SE-KEI engine) in function of propeller power. [DLR, C. Wahl, M. Kapernaum]Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 

### SE

Fuel A Fuel B Fuel C Fuel D Fuel E Fuel F Fuel G Fuel H Fuel IEI Soot [mg/kg Fuel]



### Power %

Figure 28: Emission factor for emitted particle mass fo r the different test fuels (SE-KEI engine) in function of propeller power. [DLR, C. Wahl, M. Kapernaum]

5.7 Discussion:
For gaseous emissions, an effect of different additi ves can not be clearly identified. If differences existed, they would be below the m easurement accuracy of the FOCA analyzer system. However, differences occurring from different compositi on of the fuels are clearly visible:
One way to maintain an acceptable level of octane nu mber without using lead-tetra-ethyl is by adding oxygen containing substances to the fuel. The effect of this is most pronounced with the tested lead free car gasoline (MOGAS, fuel J). The additional oxygen provided by the fuel reduces CO and total HC emissions and increases NOx emissions. In fa ct, the tested MOGAS contained large amounts of MTBE 2 . This substance might be the cause for the sign ificantly high carbonyl emissions of the tested MOGAS. In addition to that, a substance like MTBE c an pose a certain risk for the contamination of drinking water.
In order to rank the tested fuels with respect to particle emissions, the fuels can be separated into three groups:
The fuels A, B and C have the lowest particle number concentrations and the smallest particle diameter, leading to the lowest particle mass emissions. (group 1)
Fuel I (AVGAS 100LL) has the highest particle number concentrations and the highest particle diameters, leading to the highest particle mass emissions. (group 3)
The fuels D, E, F, G, and H (group 2) are situated between the group 1 and 3 fuels. The higher particle emissions of this group of fuels compared to gr oup 1 can be explained by a fuel additive, which is missing in the group 1 fuels. However, particle number concentrations and particle mass emissions are still lower than with AVGAS 100LL (group 3).

2 MOGAS sold in Switzerland and analyzed in 2006 contained qui te large quantities of MTBE (Methyl tert-butyl ether).Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern As we have seen, there is no lead free highest oc tane fuel producing the lowest possible emissions (CO, total HC, Carbonyls, NOx and particles) am ong the tested fuels. A compromise seems to be needed, weighing the different trade-offs.

5.8 First conclusions
As far as particle emissions are concerned, the standard unleaded AVGAS 91/96UL (Fuel A) has again proven its superior environmental performance.
If not highest octane number is required, an AVGAS li ke fuel C seems to be a valuable compromise.
Fuel G, which would have the potential to fully replace AVGAS 100LL from point of view of aviation octane rating, has a better environmental perform ance than AVGAS 100LL, but worse than e.g. fuel C.

Picture 13: The measurement team. From left to ri ght: C. Wahl, M. Kapernaum (both DLR), L. Hjelmberg (Hjelmco), T. Rindlisbacher, W. Bula (both FOCA)

Picture 14: HB-WAD (with Rotax engine) was generously pr ovided for the fuel tests by A. Liechti, Switzerland. Many thanks also to K. Moser (first to the right, the pilot of HB-WAD), who contributed to the measurements in his spare time.33-05-003 Piston Engine Emissions_Swiss FOCA_Appendix5_070605_rit Federal Department of the Environment, Transport, Energy and Communications DETEC

Federal Office of Civil Aviation FOCA Aviation Policy and Strategy Environmental Affairs



# AIRCRAFT PISTON ENGINE EMISSIONS

Appendix 5: Calculation of Emission Factors

FOCA, CH-3003 Bern

Reference: 0 / 3/33/33-05-003 ECERT Contact person: Theo Rindlisbacher Tel. +41 31 325 93 76, Fax +41 31 325 92 12, theo.rindlisbacher@bazl.admin.ch This document has been released for publication by FOCA, Aviation Policy and Strategy, Director M. Zuckschwerdt,11.06.2007 CO HC

NO

CO2 O2

H20

N2 CO Emissions

0 200 400 600 800 1000 1200 1400

ModeMass (g/kg Fuel)

CO

CO 1207.6 1224 1232.5 1039.6 1027.9 1045.1 801.15 780.35 808.13 1064.5 1058.2 1038.5 920.14 888.48 890.31 230.95 219.4 227.63

TO TO TO CL CL CL CR CR CR AP AP AP TA TA TA CR L CR L CR L

HC Emissions

0 2 4 6 8 10 12 14 16 18 20

ModeMass (g/kg Fuel)

HC

HC 12.957 13.139 13.154 10.12 10.14 10.121 9.4066 9.5797 9.7432 14.778 15.452 15.106 17.61 17.436 17.832 3.435 4.4517 4.6837

TO TO TO CL CL CL CR CR CR AP AP AP TA TA TA CR L CR L CR L

NOx Emissions

0 5 10 15 20 25 30 35 40 45 50

ModeMass (g/kg Fuel) NOx

NOx 1.6541 1.636 1.5795 3.0254 3.1254 3.0511 7.8972 10.021 9.0769 2.6446 2.6857 2.8899 1.8298 1.7986 1.6997 42.887 42.905 42.92

TO TO TO CL CL CL CR CR CR AP AP AP TA TA TA CR L CR L CR L 

### Measured Concentrations Emissions g/kg fuelCalculation Methodology
CO HC

NO

CO2 O2

H20

N2 CO Emissions

0 200 400 600 800 1000 1200 1400

ModeMass (g/kg Fuel)

CO

CO 1207.6 1224 1232.5 1039.6 1027.9 1045.1 801.15 780.35 808.13 1064.5 1058.2 1038.5 920.14 888.48 890.31 230.95 219.4 227.63

TO TO TO CL CL CL CR CR CR AP AP AP TA TA TA CR L CR L CR L

HC Emissions

0 2 4 6 8 10 12 14 16 18 20

ModeMass (g/kg Fuel)

HC

HC 12.957 13.139 13.154 10.12 10.14 10.121 9.4066 9.5797 9.7432 14.778 15.452 15.106 17.61 17.436 17.832 3.435 4.4517 4.6837

TO TO TO CL CL CL CR CR CR AP AP AP TA TA TA CR L CR L CR L

NOx Emissions

0 5 10 15 20 25 30 35 40 45 50

ModeMass (g/kg Fuel) NOx

NOx 1.6541 1.636 1.5795 3.0254 3.1254 3.0511 7.8972 10.021 9.0769 2.6446 2.6857 2.8899 1.8298 1.7986 1.6997 42.887 42.905 42.92

TO TO TO CL CL CL CR CR CR AP AP AP TA TA TA CR L CR L CR L CO Emissions

0 200 400 600 800 1000 1200 1400

ModeMass (g/kg Fuel)

CO

CO 1207.6 1224 1232.5 1039.6 1027.9 1045.1 801.15 780.35 808.13 1064.5 1058.2 1038.5 920.14 888.48 890.31 230.95 219.4 227.63

TO TO TO CL CL CL CR CR CR AP AP AP TA TA TA CR L CR L CR L

HC Emissions

0 2 4 6 8 10 12 14 16 18 20

ModeMass (g/kg Fuel)

HC

HC 12.957 13.139 13.154 10.12 10.14 10.121 9.4066 9.5797 9.7432 14.778 15.452 15.106 17.61 17.436 17.832 3.435 4.4517 4.6837

TO TO TO CL CL CL CR CR CR AP AP AP TA TA TA CR L CR L CR L

NOx Emissions

0 5 10 15 20 25 30 35 40 45 50

ModeMass (g/kg Fuel) NOx

NOx 1.6541 1.636 1.5795 3.0254 3.1254 3.0511 7.8972 10.021 9.0769 2.6446 2.6857 2.8899 1.8298 1.7986 1.6997 42.887 42.905 42.92

TO TO TO CL CL CL CR CR CR AP AP AP TA TA TA CR L CR L CR L 

### Measured Concentrations Emissions g/kg fuelCalculation MethodologyReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 

## Contents Page
a) Introduction 3

b) List of abbreviations 3

c) Calculation of EF (Equations used fo r FOCA ground measurements and data sheets) 3

d) Equations for "low cost" measurement system described in Appendix 1 for AVGAS 4 (used for FOCA in-flight measurements and comparative ground measurements)

e) Equations for "low cost" measurement sy stem described in Appendix 1 for DIESEL 6

f) Correction of ambient air temperature influence on normally aspirated piston engines 7

g) Statistical checks 7

h) Fuel flow 7Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern a) Introduction

Measured concentrations are converted to emission factors (EF) on the basis of molar masses. The fuel flow measurement is necessary for power setti ng checks (Appendix 3) and to calculate LTO emissions. The basic calculation is taken from „Advisory Circ ular“ AC34-1A of the Federal Aviation Administration (FAA). If a low cost gas measurement system is used , as described in appendix 1, some corrections (section d) and the use of equation (5) for the calculati on of air/fuel ratio to stoichiometric air/fuel ratio are suggested.

b) List of abbreviations

M Air Molar mass of dry air 28.966 g/mol M HC Molar mass of exhaust-HC, as Methane CH 4 16.040 g/mol M CO Molar mass of CO 28.011 g/mol M NO2 Molar mass of NO 2 46.088 g/mol M NO Molar mass of NO 30.010 g/mol M NOx Molar mass of NOx, 15% NO 2 , 85% NO 32.412 g/mol M C Molar mass of carbon C 12.011 g/mol M H Molar mass of hydrogen H 1.008 g/mol

V CO2 Volume fraction of CO 2 in dry air 0.0003

[HC] Mean concentration of exhaust-HC vol/vol [CO] Mean concentration of CO vol/vol wet [CO 2 ] Mean concentration of CO 2 vol/vol wet [NOx] Mean concentration of NOx (NO+NO 2 ) vol/vol wet [NOx] = 1.18 [NO] 1

m Number of C atoms in char. fuel molecule 7 (AVGAS / MOGAS), 12 (JET A1) n Number of H atoms in char. fuel molecule 13 (AVGAS / MOGAS), 23 (JET A1)

c) Calculation of EF (Equations used for FOCA ground measurements and data sheets) 

# [ ] [ ][ ][ ] ( )



# [ ][ ][ ] ( )



# [ ][ ][ ] ( ) ) 3 ( 1 ) / ( 10 18

. 1 ] [ ) ( ) 2 ( 1 ) / ( 10 ] [ ) ( ) 1 ( 1 ) / ( 10 ) (

2 3

2 2 3

2 2 3

2

CO H C NOx CO H C HC CO H C CO



### V A M m n M M HC CO CO NO NOx EF V A M m n M M HC CO CO HC HC EF V A M m n M M HC CO CO CO CO EF

⋅ + ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

+ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

+ + ⋅
= ⋅ + ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

+ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

+ + = ⋅ + ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

+ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

+ + =

where 

# ( )

Air H C 

### M M m n M A ) / ( +

= λ (4) and 

### λ with equation (5) or directly calculated by system.

The calculation of 

### λ (Lambda) is done with the following approximation (5) where CO2, O2 und CO are measured concentrations in volume% and HC6NDIR the NDIR HC reading in Hexane ppm.

1 Conservative assumption FOCA / DLRReference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 

### ) 10 6 6 2 ( 0088

. 0 4 7261

. 1 1 ) 2 ( 0088

. 0

2 5

. 3 5

. 3 4 7261

. 1 2 2 2

4

−



### ⋅ ⋅ + + ⋅ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛

− + + ⋅ ⎪ ⎪ ⎭ ⎪ ⎪ ⎬ ⎫

⎪ ⎪ ⎩ ⎪ ⎪ ⎨ ⎧

− + ⋅ + + +

= NDIR HC CO CO CO CO

CO CO O CO CO

λ (5)

General definition of 

### λ (Lambda):



### rich lean tric stoichiome Fuelmass Airmass measured Fuelmass Airmass

: 1 : 1 ) ( : ) ( :

< > =

λ λ λ

d) Equations for “low cost” measurement system described in Appendix 1 for AVGAS/MOGAS engines (used for FOCA in-flight measurements and comparative ground measurements)

EF(HC)

Many NDIR HC analyzers (like the one that FOCA uses for in-flight tests) read HC concentrations in hexane equivalents. Please note that in the standard calculation formulas for EF(CO), (HC) and (NOx) above, the HC concentrations have to be methane based. Parallel measurements with a hot FID HCanalyzer have shown that correction factors for the NDIR HC values can be derived. The HC correction factor counts for hexane to methane conversi on and for partial to total HC measurement. Because of fuel, engine and power dependent HC composition, the factor is not a constant:



### Relation of FID HC to NDIR HC EF without correction (AVGAS/MOGAS)

0 5 10 15 20 25 30 35 40

8-10 10-12 12-14 14-16 16-18 18-20 20-22 22-24 24-26 26-28 28-30
Classified Correction FactorFrequency

Figure 1: Distribution of the HC correction factor , based on 141 measurements with 8 different engines and all power modes. The derived mean correction factor for EF(HC) is 16.3. Depending on the engine, the engine power condition and the fuel, the error band of the NDIR HC measurement compared to the total HC measurement with FID will be +- 25%.

The magnitude of possible errors in EF(HC), wh en using NDIR HC measurement systems can be considered acceptable for the purpose of emission in ventories, but it is significant. Therefore, FOCA uses an additional hot FID for all ground measurements and FOCA engine datasheets are all based on hot FID measurements where no estimations and HC correction factors are necessary.Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern EF(CO)

The effect on EF(CO) when using NDIR HC values inst ead of FID HC values is small. On the basis of 90 measurements with 5 different engines, the resulting correction factor is 0.9839 . When using this correction and NDIR HC values, the error band is +- 1% compared to FID HC.

EF(NOx)

The effect on EF(NOx) when using NDIR HC values in stead of FID HC values is small. On the basis of 90 measurements with 5 different engines, the correction factor is 0.9839 , equal to E( CO) correction. The error band - when using this correction and NDIR HC values - is +- 1% compared to FID HC. The electrochemical NOx sensor which is used in the FOCA low cost measurement system (Appendix 1) is in fact a NO sensor and does not account for NO2. After comparativ e measurements the correction factor for NO to NOx conversion was set to 1.18 together with an assumption for M NOx (as defined in section b). The possible error band is assumed +- 10%.

Equations: 

# [ ] [ ][ ][ ] ( )



# [ ][ ][ ] ( )



# [ ][ ][ ] ( ) ) 8 ( 1 ) / ( 10 6 18

. 1 ] [ 9839

. 0 ) ( ) 7 ( 1 ) / ( 10 6 ] 6 [ 3

. 16 ) ( ) 6 ( 1 ) / ( 10 6 9839

. 0 ) (

2 3

2 2 3

2 2 3

2

CO H C NOx CO H C HC CO H C CO



### V A M m n M M NDIR HC CO CO NO NOx EF V A M m n M M NDIR HC CO CO NDIR HC HC EF V A M m n M M NDIR HC CO CO CO CO EF

⋅ + ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

+ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

+ + ⋅

⋅ = ⋅ + ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

+ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

+ + ⋅ = ⋅ + ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

+ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

+ + ⋅ =

used together with equations (4) and (5).

- INTENTIONALLY LEFT BLANK -Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern e) Equations for “low cost” measurement system described in Appendix 1 for DIESEL engines

Similarly to what has been said in section d), co rrection factors for HC have been derived for diesel engines:



### Relation of FID HC to NDIR HC EF without correction (Diesel Engine)

0 5 10 15 20

2-4 4-6 6-8 8-10 10-12
Classified Correction FactorFrequency

Figure 2: Distribution of the HC correction factor , based on 36 measurements with 2 different engines and all power modes. The derived mean correction factor for EI(HC) is 5.8. Depending on the engine, the engine power condition and the fuel, the erro r band of the NDIR HC measurement compared to the total HC measurement with FID can be +- 40%.

EF(CO)

The effect on EI(CO) when using NDIR HC values in stead of FID HC values is very small. On the basis of 36 measurements with 2 different engines, the correction factor is 0.9976 . When using this correction and NDIR HC values the error ba nd is +- 0.3% compared to FID HC.

EF(NOx)

The effect on EI(NOx) when using NDIR HC values in stead of FID HC values is small. On the basis of 36 measurements with 2 different engines, the correction factor is 0.9976 , equal to EI(CO) correction. When using this correction and ND IR HC values the error band is +- 0.3% compared to FID HC. The electrochemical NOx sensor which is used in the FOCA low cost measurement system (Appendix 1) is in fact a NO sensor and does not account for NO2. After comparativ e measurements the correction factor for NO to NOx conversion was set to 1.18 together with an assumption for M NOx (as defined in section b). The possible error band is assumed +- 10%.

Equations (next page):Reference: 0 / 3/33/33-05-003.022

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Federal Office of Civil Aviation (FOCA), Environmental Affairs, CH-3003 Bern 

# [ ] [ ][ ][ ] ( )



# [ ][ ][ ] ( )



# [ ][ ][ ] ( ) ) 11 ( 1 ) / ( 10 6 18

. 1 ] [ 9976

. 0 ) ( ) 10 ( 1 ) / ( 10 6 ] 6 [ 8

. 5 ) ( ) 9 ( 1 ) / ( 10 6 9976

. 0 ) (

2 3

2 2 3

2 2 3

2

CO H C NOx CO H C HC CO H C CO



### V A M m n M M NDIR HC CO CO NO NOx EF V A M m n M M NDIR HC CO CO NDIR HC HC EF V A M m n M M NDIR HC CO CO CO CO EF

⋅ + ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

+ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

+ + ⋅

⋅ = ⋅ + ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

+ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

+ + ⋅ = ⋅ + ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

+ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

+ + ⋅ =

used together with equations (4) and (5).

f) Correction of ambient air temperature influence on normally aspirated piston engines

HC and CO emission factors for normally aspirated piston engines have been shown to be significantly temperature dependent, mainly because of air density va riations and its influence on the air/fuel mixture. To correct the emission factors to 15°C, the following equations are suggested:

CO Measurement :EF CO(15°C) = 3.1259*(15 - T) + EF CO(T) (12) HC Measurement: EF HC(15°C) = 0.0164*(15 - T) + EF HC(T) (13)

Ambient air humidity primarily seems to have an e ffect on NOx emissions. However, these emissions are very low at “full rich” condi tions and therefore no significant correction could be established.

g) Statistical checks

For each engine and power mode, a minimum of three valid measurements has been defined. The confidence interval (90% Conf. Level) is deter mined with a T-Test and assumed normal distributed values.

h) Fuel flow

The fuel flow is normally measured in liters/hour or US gallons/hour. The standard calculation of the fuel flow in kg/s is done with a mean fuel densit y of 0.72 kg / liter for AVGAS/MOGAS and of 0.80 kg / liter for DIESEL/JETA1.