DOT/FAA/AR-04/8 

Office of Aviation Research 

Washington, D.C. 20591

Limiting Oxygen Concentration 

Required to Inert Jet Fuel Vapors 

Existing at Reduced Fuel Tank 

Pressures—Final Phase 

August 2004 

Final Report 

This document is available to the U.S. public 

through the National Technical Information 

Service (NTIS), Springfield, Virginia 22161. 

U.S. Department of Transportation 

Federal Aviation Administration
NOTICE 

This document is disseminated under the sponsorship of the U.S. 

Department of Transportation in the interest of information exchange. The 

United States Government assumes no liability for the contents or use 

thereof. The United States Government does not endorse products or 

manufacturers. Trade or manufacturer's names appear herein solely 

because they are considered essential to the objective of this report. This 

document does not constitute FAA certification policy. Consult your local 

FAA aircraft certification office as to its use. 

This report is available at the Federal Aviation Administration William J. 

Hughes Technical Center's Full-Text Technical Reports page: 

actlibrary.tc.faa.gov in Adobe Acrobat portable document format (PDF). 
Technical Report Documentation Page

1. Report No.

DOT/FAA/AR-04/8

2. Government Accession No. 3. Recipient's Catalog No.

 4. Title and Subtitle 

LIMITING OXYGEN CONCENTRATION REQUIRED TO INERT JET FUEL

5. Report Date

August 2004 

VAPORS EXISTING AT REDUCED FUEL TANK PRESSURES—FINAL 

PHASE

6. Performing Organization Code

7. Author(s)

Steven M. Summer

8. Performing Organization Report No. 

9. Performing Organization Name and Address

Federal Aviation Administration 

William J. Hughes Technical Center 

Airport and Aircraft Research and 

10. Work Unit No. (TRAIS)

Development Division 

Fire Safety Branch 

Atlantic City International Airport, NJ 08405

11. Contract or Grant No.

12. Sponsoring Agency Name and Address

U.S. Department of Transportation

13. Type of Report and Period Covered

Final Report 

Federal Aviation Administration 

Office of Aviation Research 

Washington, D.C. 20591 

14. Sponsoring Agency Code

 

ANM-100

15. Supplementary Notes

This report is an extension of the initial Technical Report published as DOT/FAA/AR-TN02/79. 

16. Abstract

This report discusses experiments to determine the reduction in oxygen concentration required to prevent a fuel tank explosion. 

A simulated aircraft fuel tank containing JP-8 fuel of an amount equivalent to a mass loading of approximately 4.5 kg/m3

 was 

used to determine the limiting oxygen concentration (LOC) at pressures corresponding to altitudes ranging from 0 to 38,000 ft. 

In addition, the peak pressure rise was measured at various altitudes (pressures) due to ignition occurring at O2 levels 

approximately 1% to 1.5% above the LOC. 

From these tests, it was determined that the LOC at sea level through 10,000 ft is approximately 12% O2, with a linear increase 

from 12% at 10,000 ft to approximately 14.5% at 40,000 ft. Tests with various sparks/arcs as ignition sources at sea level 

showed little variation in results, with the LOC ranging from 11.9% to 12.8%. The single ignition event falling below 12% O2 is 

attributed to inherent error in the oxygen measurement system, whose sensitivity is stated to be ±1% of the full-scale value (25% 

O2). In addition, a heated surface capable of igniting a flammable fuel air mixture proved insufficient for ignition in a tank 

inerted to just 14%. Peak pressures resulting from ignition at oxygen concentrations 1% to 1.5% above LOC values decreased as 

the altitude was increased to 30,000 ft, while the duration to reach the peak pressure increased. 

17. Key Words 

Fuel, Fuel tank, Flammability, Ignition, Inert, Jet A, JP-8, 

Limiting oxygen concentration, Nitrogen inerting

18. Distribution Statement 

This document is available to the public through the National 

Technical Information Service (NTIS) Springfield, Virginia 

22161.

19. Security Classif. (of this report)

 Unclassified 

20. Security Classif. (of this page)

 Unclassified

21. No. of Pages

 43

22. Price

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized 
TABLE OF CONTENTS 

Page 

EXECUTIVE SUMMARY vii 

1. INTRODUCTION 1 

1.1 Background 1 

1.2 Aviation Fuel Specification and Characteristics 1 

1.3 Scope of Experiments 3 

2. EXPERIMENTAL APPARATUS 4 

2.1 Test Article 4 

2.2 Pressure Measurement 6 

2.3 Vapor Measurement 6 

2.3.1 Hydrocarbon Analysis 7 

2.3.2 Oxygen Analysis 8 

2.4 Ignition Sources 8 

2.5 Spark/Arc Energy Calculation Method and Results 9 

3. EXPERIMENTAL PROCEDURES 11 

3.1 Methane Validation Tests 11 

3.2 JP-8 Liquid Fuel Tests 11 

4. DISCUSSION OF RESULTS 12 

4.1 Methane Validation Tests 12 

4.2 JP-8 Liquid Fuel Tests 13 

4.2.1 Long-Duration Oil Burner Transformer Tests 13 

4.2.2 Engine Spark Igniter Tests 21 

4.2.3 Short-Duration Oil Burner Transformer Tests 22 

4.2.4 Four Hundred-Cycle Short to Ground Ignition Tests 23 

4.2.5 Hot-Surface Vapor Ignition Tests 23 

5. CONCLUSIONS 24 

6. REFERENCES 24 

iii
APPENDICES 

A—Commercial and Military Aviation Fuel Specifications

B—JP-8 Liquid Fuel Test Data

LIST OF FIGURES

Figure Page 

1 Typical Flash Point Temperatures of Jet A and Jet B Fuel Blends 2 

2 Typical Industry-Accepted Plots of Jet Fuel Flammability Limits 3 

3 Schematic of Experimental Setup 5 

4 Thermocouple Locations 6 

5 Ullage Vapor Sampling System 7 

6 Voltage and Current Traces of (a) J-57 Engine Igniter, (b) Oil Burner Transformer 

Ignition Sources, and (c) 400-Cycle Short 10 

7 Experimental Methane LFL Data 13 

8 Limiting Oxygen Concentration Data Results—Aluminum Plate Relief 

Mechanism 14

9 Limiting Oxygen Concentration Data Results— Foil Diaphragm Relief 

Mechanism 14

10 Limiting Oxygen Concentration Data Results—Minimum and Maximum Values 

for Ignition and Nonignition 15 

11 Limiting Oxygen Concentration Data Results—Fuel-Air Ratio and Fuel Vapor 

Concentration vs Oxygen Concentration (Sea Level) 16 

12 Limiting Oxygen Concentration Data Results—Fuel-Air Ratio and Fuel Vapor 

Concentration vs Oxygen Concentration (10,000 ft) 17 

13 Limiting Oxygen Concentration Data Results—Fuel-Air Ratio and Fuel Vapor 

Concentration vs Oxygen Concentration (20,000 ft) 17 

14 Limiting Oxygen Concentration Data Results—Fuel-Air Ratio and Fuel Vapor 

Concentration vs Oxygen Concentration (30,000 ft) 18 

iv
15 Limiting Oxygen Concentration Data Results—Fuel-Air Ratio and Fuel Vapor 

Concentration vs Oxygen Concentration (38,000 ft) 18 

16 Peak Pressure Rise vs Altitude at O2 Concentrations 1% to 1.5% Above the LOC 19 

17 Ignition Time Duration vs Altitude at O2 Concentrations 1% to 1.5% Above the 

LOC 20 

18 Engine Igniter Test Results (Sea Level) 21 

19 ASTM D 86 Distillation Curves and Flash Point Data of JP-8 and Hexane 

Mixtures 22

LIST OF TABLES 

Tables Page 

1 Altitude-Pressure Data 4 

2 Measured Spark/Arc Energies 9 

3 Nonvented, Full Vessel Ignition Pressure Results 20 

4 Short-Duration Oil Burner Transformer Test Results 22 

5 Four Hundred-Cycle Short Test Results 23 

6 Hot-Surface Vapor Ignition Test Results 24 

v
LIST OF ACRONYMS

FAA Federal Aviation Administration 

CWT Center wing tank 

LOC Limiting oxygen concentration 

NTSB National Transportation Safety Board 

LFL Lean flammability limit 

ASTM American Society of Testing and Materials 

HAVI Hot-surface vapor ignition 

THC Total hydrocarbon 

FID Flame ionization detector 

FAR Fuel-air mass ration 

UFL Upper flammability limit 

HST Hot-surface temperature 

vi
EXECUTIVE SUMMARY

Aircraft fuel tank protection has become of great importance within the aviation community 

since the fatal accident of TWA flight 800, a Boeing 747, over East Moriches, NY, in July 1996. 

The National Transportation Safety Board determined that the “probable cause of the TWA 

flight 800 accident was an explosion of the center wing fuel tank (CWT), resulting from ignition 

of the flammable fuel-air mixture in the tank.” As a result, the Federal Aviation Administration 

(FAA) is conducting research aimed at reducing or eliminating the flammability exposure time

of such heated CWTs. Much consideration is being given to the design and optimization of a 

system using nitrogen inerting. In this process, nitrogen or nitrogen-enriched air is used to 

reduce oxygen concentration within the fuel tank to a level that prevents the ignition of 

flammable ullage vapors. This type of system has been implemented in several military aircraft; 

however, the high cost and weight combined with low reliability make those designs impractical 

for transport category aircraft. Recent advances in gas separation technologies may make it 

possible to design an economic and reliable means of inerting commercial aircraft fuel tanks. 

However, to optimize such a system, more data on fuel flammability and inerting gas 

requirements are needed. The goal of the research effort discussed herein is to determine the

oxygen concentration necessary to render the fuel tank ullage inert. This value is termed the

limiting oxygen concentration (LOC). 

The tests were conducted at the FAA William J. Hughes Technical Center, Atlantic City 

International Airport, NJ, in a facility capable of creating pressures corresponding to altitudes 

ranging from 0 to 38,000 ft. From these tests, it was determined that the LOC at sea level 

through 10,000 ft is approximately 12% O2, with a linear increase from 12% at 10,000 ft to 

approximately 14.5% at 40,000 ft. Tests with various sparks and arcs as ignition sources at sea 

level showed little variation in results with the LOC ranging from 11.9% to 12.8%. In addition,

a heated surface capable of igniting a fuel-air mixture proved insufficient for ignition in a tank 

inerted to just 14%. Peak pressures resulting from ignition at oxygen concentrations 1% to 1.5%

above LOC values decreased as the altitude was increased to 30,000 ft, while the duration to 

reach the peak pressure increased. Further experiments to examine the rise in peak pressure as a

function of both altitude and oxygen concentration are needed. The results contained in this 

report should be useful in the design, sizing, and optimization of future aircraft inerting systems 

and add to the overall knowledge base of jet fuel flammability characteristics. 

vii/viii
1. INTRODUCTION.

1.1 BACKGROUND. 

Aircraft fuel tank protection has become of great interest within the aviation community since

the fatal accident of TWA flight 800, a Boeing 747, over East Moriches, NY, in July 1996. The 

National Transportation Safety Board (NTSB) determined that the “probable cause of the TWA 

flight 800 accident was an explosion of the center wing fuel tank (CWT), resulting from ignition 

of the flammable fuel/air mixture in the tank” [1]. The NTSB [1] further concluded that

contributing factors to the accident were that the design and certification of the aircraft required 

only the preclusion of all potential ignition sources to prevent a fuel tank explosion. No 

measures were taken to reduce heat transfer or inert the fuel tank. 

In several aircraft configurations, including the B747, the environmental conditioning system 

packs are located beneath the CWT. The hot bleed air from this system, passing directly 

underneath the tank, is the driving force behind the generation of flammabable fuel vapor in the 

ullage. In fact, the Aviation Rulemaking Advisory Committee’s Fuel Tank Harmonization 

Working Group [2] found that heated CWTs contain a flammable fuel-air mixture 30% of the 

total flight time compared with only 4% to 6% of the flight time for unheated CWTs and 2% to 

4% for typical unheated main wing tanks. 

The Federal Aviation Administration (FAA) is currently conducting research aimed at reducing 

or eliminating the flammability exposure time of CWTs. Much consideration is being given to 

the design and optimization of a system involving nitrogen inerting. In this process, nitrogen or 

nitrogen-enriched air would be used to reduce the oxygen concentration within the fuel tank to a 

level at which ignition could not be supported by the flammable vapors. Inerting systems have 

been implemented in several military aircraft; however, the high cost and weight combined with

low reliability make military designs impractical for transport category aircraft. Recent advances 

in gas separation technologies may make it possible to design an economic and reliable means of 

inerting aircraft fuel tanks. However, to optimize such a system, more data concerning fuel 

flammability and inerting gas requirements are needed throughout the operational envelope of a 

fuel tank, including the effect of various possible ignition sources. 

1.2 AVIATION FUEL SPECIFICATION AND CHARACTERISTICS.

In the United States, specific requirements relative to aviation turbine fuel properties is set forth

by the American Society of Testing and Materials (ASTM) Standard D 1655. This standard 

limits itself to the commercial grade fuels Jet A, Jet A-1, and Jet B. Jet A and Jet A-1 are the

most commonly used aviation fuels, differing only in their freezing point (-40°C for Jet A and 

-47°C for Jet A-1). Both are derived from kerosene and have a relatively high flash point, set at 

a minimum of 38°C (100°F). 

Jet B fuel, on the other hand, is rarely used today. Jet B is essentially the same as JP-4, a 

standard U.S. military fuel that was used until 1988 when a transition to JP-8 (a fuel which is

very similar to Jet A) was initiated [3]. In addition, the U.S. military also currently uses the high 

flash point (60°C), kerosene-based JP-5 fuel for U.S. Navy carrier-based aircraft. While 

ASTM D 1655 does not control the specifications for these military fuels, a listing of their 

1
corresponding requirements can be found in the Handbook of Aviation Fuel Properties [4]. 

These specifications, for JP-4, -5, and -8, as well as those from ASTM D 1655 for Jet A, Jet A-1, 

and Jet B, are given in appendix A for convenience. 

The fuel used in the experiments discussed within this report was JP-8, which can be treated 

approximately as Jet A (see appendix A for a direct comparison). With regards to the chemical 

composition of Jet A, ASTM D 1655 states that these fuels “shall consist of refined 

hydrocarbons derived from conventional sources including crude oil, natural gas liquids, heavy 

oil, and tar sands.” There are no provisions given for the exact composition of the fuel, and as 

such, the properties of any given fuel batch can vary from that of any other, provided that they 

meet the minimum specifications set forth in ASTM D 1655. This lack of a definitive 

composition results in fuels that consist of hundreds of chemical species. 

Regarding the flammability properties of aviation fuels, the two most widely used parameters are 

the fuel’s flash point and flammability limits, given in terms of altitude and temperature data. 

The flash point of a liquid fuel is defined as the lowest temperature at atmospheric pressure, at 

which sufficient vapor is released by the fuel to support ignition. The current standardized 

methods for determining the flash point are ASTM D 56 and ASTM D 3828. Both methods

place a sample of fuel in a closed cup and heat it at a constant rate. A small flame is introduced 

into the cup, and the lowest temperature at which ignition is observed is referred to as the flash 

point. Figure 1, as taken from reference 4, shows a graph of approximate flash points versus

blends of Jet A and Jet B fuels. 

Fuel Composition by Volume

Flash Point (ASTM D93) 

Temperature, °C 

FIGURE 1. TYPICAL FLASH POINT TEMPERATURES OF JET A AND 

JET B FUEL BLENDS 

2
The flammability limits of a given fuel provide more information than the flash point

measurement, especially when presented as regions of flammability in terms of altitude and fuel 

temperature. At any given altitude (pressure), a fuel will have a lean (or lower) flammability 

limit (LFL) and a rich (or upper) flammability limit. Within these limits, ignition of vapors may 

occur, while outside the limits there should be no observed combustion phenomenon. Over the 

years, there have been numerous experiments to determine the flammability limits of aviation 

turbine fuels. A typical plot of these limits, including ignition energies, for Jet A and Jet B fuels 

is shown in figure 2, as taken from reference 3. 

FIGURE 2. TYPICAL INDUSTRY-ACCEPTED PLOTS OF JET FUEL

FLAMMABILITY LIMITS 

Both the flash point and flammability limits given above assume isothermal and equilibrium 

conditions, not taking into account such things as possible condensation of the fuel vapor and 

variation of the ullage composition. To provide useful data for fuel tank inerting requirements, 

data on the reduction of fuel flammability as a function of oxygen depletion are needed. 

1.3 SCOPE OF EXPERIMENTS.

The purpose of the experimental research discussed in this report is to further quantify the 

oxygen concentrations required to protect against the ignition of JP-8 fuel vapors at altitudes 

ranging from 0 to 38,000 ft. This data will aid in the design of nitrogen-inerting systems for use 

in aircraft fuel tanks. Throughout the experiments, the lowest oxygen concentration resulting in 

ignition of the ullage fuel vapors is referred to as the limiting oxygen concentration (LOC). 

3
2. EXPERIMENTAL APPARATUS.

2.1 TEST ARTICLE. 

The experiments discussed within this report were conducted at the FAA William J. Hughes 

Technical Center Pressure Fire Modeling Facility. This facility houses a 10-m3

 vessel capable of 

withstanding a maximum working pressure of 650 psi. An attached vacuum pump evacuated the 

chamber to pressures corresponding to desired altitudes. The pressures corresponding to each 

altitude tested can be found in table 1. 

TABLE 1. ALTITUDE-PRESSURE DATA 

Altitude

(thousand feet) 

Pressure 

(psia)

0 14.70

10 10.25

20 6.97

30 4.61

38 3.22

The vented fuel tank test article placed within the 10-m3

 vessel was approximately 0.25 m3 (9 ft3) 

in volume. It was equipped with 12 K-type thermocouples, sample lines for hydrocarbon and 

oxygen vapor sampling, thermostatically controlled hot plates with a capacity of 1650 watts, and 

a 6-in.-diameter mixing fan used to ensure a homogeneous ullage vapor mixture. A fuel pan, 

measuring 9.5 by 9.5 in., was placed in the center of the fuel tank. A 10- by 10-in. opening in 

the fuel tank’s roof was fitted with interchangeable pressure relief mechanisms of either a springloaded 1/4-in.-thick aluminum plate or a foil diaphragm.

The aluminum plate mechanism was used in the early phases of testing to gain general 

knowledge of the LOC at each altitude, while the diaphragm was used to more accurately 

determine the LOC. In the case of the aluminum plate, an ignition was said to occur if there was 

noticeable movement of the plate; whereas, with the latter mechanism, ignition was said to occur 

only if the diaphragm was ruptured during the test. 

In addition, two piezoresistive pressure transducers installed in the tank were used at oxygen 

concentrations approximately 1% to 1.5% above the LOC at each altitude. These tests were

performed in hopes of providing more knowledge of the pressure rises associated with these lowlevel oxygen tests so as to increase confidence that any chemical reactions near the LOC would

not result in pressure increases that might impact the structural integrity of the tank. 

A bank of nitrogen bottles, connected to the fuel tank and controlled via a solenoid valve, served 

the dual purpose of controlling the ullage oxygen concentration and extinguishing any flames

resulting from ignition of the ullage vapors. In addition, a bottle of 100% methane was 

connected to the fuel tank, for use during the validation tests, in which the LFL for methane was

determined and compared to published data [5]. 

4
The 12 thermocouples were used to record liquid fuel, ullage, and tank wall temperatures for the

purpose of test monitoring and for use in fuel vapor modeling work currently being undertaken 

in a joint effort by the FAA and Professor C.E. Polymeropoulos of Rutgers University [6]. Two 

thermocouple trees, placed within the tank, held a total of four ullage thermocouples. There 

were two thermocouples on each tree, which were placed a third of the way up from the bottom 

of the tank and a third of the way down from the top. Two thermocouples were placed on the 

floor directly above the two heating elements, and one was placed in the middle of the floor, 

directly under the fuel pan in between the two heating elements. In addition, one thermocouple 

was used to record the liquid fuel temperature, and another thermocouple was placed at the

center of each sidewall. 

A spark/arc gap was located in the front left corner of the fuel tank. This gap consisted of two 

1/16-in.-diameter tungsten electrodes that used a micrometer for gap width control and 

adjustment springs for electrode alignment. The gap width was set at approximately 7 mm

throughout testing because this has been shown to be the optimum electrode spacing for ignition 

testing with methane [7]. Throughout testing, these electrodes were powered by two different 

spark/arc generators—an arc-generating oil burner transformer and a J-57 engine spark igniter. 

In addition to these two ignition sources, a hot surface was also used in a brief set of tests 

concerning hot-surface vapor ignition (HSVI). All of these ignition sources are discussed in 

detail in section 2.4, and a discussion of the methods used and results of energy calculations of 

the spark/arc generators is provided in section 2.5. 

All test equipment was controlled through solid-state relays, powered by toggle switches located 

within a trailer directly outside the test facility. The trailer also housed all computer and data

acquisition equipment. Schematics of this test setup, including thermocouple placements, are 

shown in figures 3 and 4. 

Video

Camera THC

Analyzer

Right Test Track

Left Test Track

10 m Pressure

Vessel

3 Analyzer Bypass

Sample Line O 

Analyzer 2

Heater

Spark 

Source

Fan

= Thermocouple Feedthrough

N Lines 2

House

Air Line

Pressure Transducers

FIGURE 3. SCHEMATIC OF EXPERIMENTAL SETUP (PLAN VIEW) 

5
Left T/C Tree Right T/C Tree

Liquid JP-8 Fuel Fuel Pan

= Thermocouple Bead

6.

0" 6.

0" FIGURE 4. THERMOCOUPLE LOCATIONS 

2.2 PRESSURE MEASUREMENT.

Two piezoresistive pressure transducers were used in testing at ullage oxygen concentrations 

approximately 1% to 1.5% greater than the determined LOC at each altitude. A Kulite model 

XT-130 and an Endevco model 8530C were employed and both were operated at a frequency of

1 kHz. Though manufactured by different companies, both have similar electronics and work on 

the same theory of operation, thus giving similar readings. In a method similar to Shepherd, et

al. [8], to protect these transducers from the high temperatures associated with the ignition, it was 

necessary to place them in protective housings with a 3/8-in.-thick, sintered porous metal disc in

front of the diaphragms. These protective housings act as a flame arrestor, protecting the 

transducers from the impinging flame front. 

2.3 VAPOR MEASUREMENT.

Ullage hydrocarbon and oxygen concentrations were measured with dedicated hydrocarbon and 

oxygen analyzers connected to the test article via 1/4-inch sample lines. Among the

considerations taken into account when designing the sampling systems were condensation of the 

fuel vapors, fouling of the sensors, depletion of the sample, and maintaining the necessary 

pressures and flow rates for each of the analyzers. A schematic of the sample trains employed is 

shown in figure 5 and detailed descriptions of each are given in sections 2.3.1 and 2.3.2 as well 

as brief summaries of the measurement principles of each analyzer. 

6
B

THC

Analyzer

Pressure Vessel

B

Oxygen

Analyzer

Heated Sample Line

Unheated Sample Line

B

Ball Valve

T-Fitting 3-Way Valve

Flowmeter

Pressure Regulator

Diaphragm Pump

Bulkhead Fitting

KEY

Cal. Gas Inlet

Bypass

THC Intake

Oxygen Intake

Oxygen Return

Sample

Overflow

Locations

Ice-Temperature Bath

Flow Meter 

FIGURE 5. ULLAGE VAPOR SAMPLING SYSTEM 

2.3.1 Hydrocarbon Analysis.

Hydrocarbon concentrations were measured throughout the tests with a total hydrocarbon (THC) 

analyzer using flame ionization detector (FID) technology. The full length of the sample line 

was maintained above 300°F with analog temperature controllers. This sample line was routed 

outside the rear of the vessel, into a series of ball valves, and into the hydrocarbon analyzer. The 

ball valves were used to switch the sampling process from inside the fuel tank to the ambient air 

outside the pressure vessel. This was done for two reasons. First, it was necessary to ensure that 

during ignition, the analyzer was not sampling from the fuel tank because it would damage the 

sensor. Second, it was necessary to intermittently draw a vapor sample from the tank because 

continuous sampling would result in a severe depletion of the sample. In addition, for tests at 

altitude, an external diaphragm-type pump was used between the ball valves and the analyzer to 

achieve the necessary flow rate through the detector. A flow meter on the bypass end of the 

analyzer was used to confirm the required sample flow rate. Limitations of the sample pump 

prevented experiments above altitudes of 38,000 ft. Testing at higher altitudes resulted in 

insufficient flow on the outlet of the pump. This caused a reversal in flow direction at the 

sample overflow location, thus diluting the vapor sample. 

7
Calibration of the THC analyzer was performed by flowing mixtures of varying propane 

concentration directly into the calibration ports of the analyzer. This calibration was then 

checked by allowing the calibration gas to flow through the pump into the sample inlet to ensure 

that there was no variance between the sample line and the calibration line. 

The measurement principle of an FID analyzer is based on the ionization of organically bound 

carbon atoms in a hydrogen flame. The vapor sample is mixed with a hydrogen fuel mixture

prior to reaching the burner, where the high temperature of the hydrogen flame causes reaction of

the hydrocarbon compounds. Ions produced by this combustion are detected by the electrodes of 

the FID, and the resulting current is amplified and outputted. This output is proportional to the 

number of carbon atoms for all hydrocarbon molecules and provides accurate THC 

measurements in terms of a volumetric concentration relative to the calibration gas. 

2.3.2 Oxygen Analysis.

A Rosemount OM-11 EA oxygen analyzer was used to record the tank oxygen concentrations

throughout the test program. Using a diaphragm-type pump in conjunction with a pressure 

regulator and flow meter to maintain a steady flow and pressure, the sample was drawn from the 

tank through an ice temperature bath, into the analyzer, and then recirculated back into the tank.

A backpressure regulator on the return side ensured positive flow back into the test article. The

ice temperature bath was used to condense out the hydrocarbons from the sample prior to 

reaching the oxygen sensor, which was found to be sensitive to these liquids. Calibration was 

performed by inserting mixtures of varying oxygen concentration into the sample line upstream 

of the diaphragm pump. 

The OM-11 is, in essence, a partial pressure-sensing device. It uses a polarographic oxygen 

analysis technique, whereby two electrodes immersed in potassium chloride gel permit the

diffusion of oxygen across a Teflon membrane. The rate of this diffusion is proportional to the 

partial pressure of oxygen on the outside of the membrane. The OM-11 converts this partial 

pressure into a reading of volumetric percent oxygen concentration, having an output on a scale 

of 0 to 5 Vdc. 

2.4 IGNITION SOURCES.

A range of ignition sources were employed throughout the testing. The initial ignition source 

was an oil burner transformer connected to an analog timer, which provided a low-power arc of

both short (0.1 second) and long durations (1 second). High-powered sparks were then obtained 

through two methods: (1) a spark igniter taken from a J-57 engine provided a very short-duration 

(175 μseconds), high-powered spark and (2) a hard short of a 120 V, 400-cycle line to ground 

provided a spark of approximately 0.01 second in duration with an energy of approximately 

2-3 Joules. In addition to these arcs and spark, a heated metal block was used as a hot-surface 

ignition source. The heated metal block, which measured 1′′ x 3′′ x 6′′ long, was heated by two 

0.75′′ diameter heating rods that passed through the unit and was monitored by a thermocouple 

mounted to the top surface. A wide range of ignition sources were tested to determine any

variation in the LOC due to ignition source duration and power (energy). 

8
2.5 SPARK/ARC ENERGY CALCULATION METHOD AND RESULTS.

To quantify the characteristics of the sparks and arcs used in testing, measurement of both

voltage and current at the point where the high-voltage leads entered the fuel tank were made. A 

Tektronix P6015A high-voltage probe was used for voltage measurement and an Ion Physics 

model CM-10-L was used for current measurement. Both probes were connected to a Tektronix 

THS730A oscilloscope, which was used to record the two traces and transport them to a personal 

computer where calculations could be performed. With the voltage and current data, the energy 

deposited into the gap was calculated by 

(1) ∫ =

1

0

t

E VIdt

These measurements and calculations were performed for both the short- and long-duration oil 

burner transformer arc, the engine igniter spark, and the 400-cycle short. The results of these

measurements are shown in table 2, while the voltage and current traces for the engine igniter 

and portions of the traces for the oil burner transformer and 400-cycle short are shown in figures 

6(a), (b), and (c). The oil burner and engine igniter both provided very repeatable traces and 

energy calculations, while the 400-cycle short had some amount of variability to it. The 

calculated energies for three sparks generated with the 400-cycle short method provided energy 

calculations ranging from 1.8-2.8 Joules. Although the engine igniter provided a spark of equal 

energy to the long-duration oil burner transformer arc, it is generated in a small fraction of a 

second, thus providing a much more powerful spark. 

TABLE 2. MEASURED SPARK/ARC ENERGIES 

Ignition Source 

Time Duration 

(s) 

Energy 

(Joules) 

Oil Burner Transformer 1.0 0.5 

Oil Burner Transformer 0.1 0.08 

J-57 Engine Igniter 0.000175 0.5 

400-cycle short 0.01 1.8-2.8 

In addition, noise tests were conducted to determine if noise levels on either of the probes were 

large enough to effect this energy calculation. These tests clearly indicated that any noise on 

either of the probes was insufficient to have affected energy calculations in any significant way. 

9
(a) 

(b) 

-8

-6

-4

-2

0

2

4

6

8

-0.005 -0.003 -0.001 0.001 0.003 0.005 0.007 0.009 0.011 0.013 0.015

Time (s)

Voltage

-200

-150

-100

-50

0

50

100

150

200

Current

Voltage

Current

(c) 

FIGURE 6. VOLTAGE AND CURRENT TRACES OF (a) J-57 ENGINE IGNITER, (b) OIL 

BURNER TRANSFORMER IGNITION SOURCES, AND (c) 400-CYCLE SHORT 

10
3. EXPERIMENTAL PROCEDURES.

3.1 METHANE VALIDATION TESTS. 

Prior to each test, the test article was purged with shop air to remove any remaining methane 

vapors. The hydrocarbon analyzer was calibrated with a certified bottle of 5 percent methane

balanced in nitrogen and was zeroed with 100% nitrogen. The vessel door was closed and 

sealed, and data acquisition was initiated. A solenoid valve was opened to introduce methane 

into the test article. The ullage vapors were monitored with the hydrocarbon analyzer, providing 

time for complete mixing of the methane vapors. Once the desired methane concentration

stabilized, a 1-second spark initiated the combustion process. This was repeated at numerous 

methane concentrations until ignition, defined in these tests as visual observation of movement 

of the blowout plate, was unobtainable. This level was then noted as the LFL and was compared 

to published data [5]. 

3.2 JP-8 LIQUID FUEL TESTS.

Prior to each test, the test article was purged of any remaining vapors with shop air until the 

ullage oxygen content was approximately 20.9%, and the hydrocarbon concentration was below 

2000 ppm-C3H8. The hydrocarbon analyzer was calibrated and linearized with certified bottles 

of 2, 3, 4, and 6 percent propane balanced in nitrogen. The oxygen analyzer was subsequently 

calibrated with certified bottles of 12% and 16% oxygen with a nitrogen balance. In addition, 

both analyzers were zeroed with a bottle of 100% nitrogen. 

Following this calibration and a check of all critical devices, 3/8 of a gallon of JP-8 fuel was

carefully measured, poured into the fuel pan, and placed in the center of the fuel tank. The 

pressure vessel was hydraulically sealed and the vacuum pump was used to evacuate the 

chamber to the approximate pressure corresponding to the desired altitude. Data collection was 

initiated. The nitrogen solenoid valve was opened to introduce nitrogen into the tank. The flow 

of nitrogen was introduced in stages, while monitoring the ullage oxygen concentration. When

the desired oxygen concentration was achieved, all nitrogen flow was terminated, and the fuel 

heating process was started. 

The oxygen and hydrocarbon concentrations within the fuel tank were periodically checked 

throughout the test, with the fan being used periodically to ensure a well-mixed ullage vapor 

space. Upon achieving the desired ullage vapor concentration, the oxygen analyzer pump was

turned off, and the hydrocarbon analyzer was switched to sample from ambient air. This was

done to prevent combustion products from fouling the gas analyzer sensors. 

At this point, video tape recording was initiated and the fuel vapor mixture was subjected to 

several sparks/arcs. In the case of the HSVI tests, the heated block was running and monitored 

throughout the test at between 50% to 70% full load and turned to full load as the desired ullage

vapor concentration was achieved. The hot-surface temperature (HST) was monitored 

throughout. In all test cases, if ignition, as defined in section 2.1, was not observed, the test was 

terminated, and the tank was considered inert under these conditions. 

11
To obtain worst-case scenario data, it was desired to perform testing at near-stoichiometric 

mixtures. Calculations of the stoichiometric mixture were performed by approximating the fuel 

vapor as a hydrocarbon with composition CxHy. Using an existing computer model developed 

by Ivor Thomas, the FAA’s Chief Scientific and Technical Advisor for Fuel Systems, a ratio of

y:x was obtained, as well as the vapor’s molecular weight. These calculations, with the input of 

a stoichiometric fuel-air mass ratio (FAR) of 0.068, resulted in y/x = 1.99 and MWvapor = y + 12x 

= 126.54. With this information, it was then determined that the approximate fuel vapor was 

C9.05H18.01. This could then be substituted into a stoichiometric chemical equation 

C9.05H18.01 + a[O2 + 3.76N2] → bCO2 + cH2O +dN2 

Solving this equation for the coefficients a, b, c, and d results in 

C9.05H18.01 + 13.55[O2 + 3.76N2] → 9.05CO2 + 9H2O +50.96N2 

From this, the fuel-air mole ratio can be determined as 

( )( ) 1.53%

1 4.76 13.55

1 = + =

air

fuel

mol

mol

Therefore, the stoichiometric mixture in terms of parts-per-million of fuel vapor (ppmfuel) is

given by 15,267 ppmfuel. To obtain this value in terms of propane, it is simply multiplied by the

carbon ratio, in this case 9.05/3. This then results in an approximate stoichiometric mixture of 

46,155 ppm-C3H8. Performing this same set of calculations for a 12% O2 environment, one finds 

a stoichiometric 12% O2 air mixture of approximately 24,000 ppm-C3H8. As testing showed, 

and as discussed in section 4.2.2, this stoichiometric mixture at a reduced O2 concentration

resulted in the lowest values of the LOC despite initial thoughts that a stoichiometric 21% O2 air 

mixture would be needed. Therefore, the majority of testing was conducted at and around this

fuel-air ratio. 

4. DISCUSSION OF RESULTS.

4.1 METHANE VALIDATION TESTS. 

As discussed previously, prior to performing any ignition experiments with aviation fuel, a series 

of validation tests were performed with methane in air mixtures. Because pressure was not 

measured in these experiments, ignition was defined by visual observation of the movement of 

the blowout plate, which resulted from a pressure buildup within the tank. 

The experimental data for this series of tests is shown in figure 7, in terms of ignition and 

nonignition criteria. The data show that the LFL of methane lies somewhere between 5.3% and 

5.35% methane, matching closely the value 5.3% given by Lewis and von Elbe [5]. Therefore, it 

was concluded that the experimental apparatus and methods employed were suitable for ignition 

testing. 

12
FIGURE 7. EXPERIMENTAL METHANE LFL DATA 

4.2 JP-8 LIQUID FUEL TESTS. 

The majority of tests with liquid JP-8 fuel were conducted using the oil burner transformer as the 

ignition source with an arc duration of 1 second. These tests were conducted with both the 

1/4-in. aluminum plate and foil diaphragm pressure relief mechanisms and at altitudes ranging 

from 0 to 38,000 ft. Subsequent tests used the other various ignition sources in an attempt to 

verify any dependency of the LOC with ignition source. Tests with the short-duration oil burner 

transformer, engine igniter, and hot surface focused on sea level conditions because this is the

region that drives the design criteria for an inerting system. All test data discussed herein 

relative to the JP-8 liquid fuel test sets are shown in tabular format in appendix B. 

4.2.1 Long-Duration Oil Burner Transformer Tests.

The initial oil burner transformer tests were conducted with a spring-loaded, 1/4-in. aluminum 

plate used as the pressure relief mechanism and a 1-second arc duration. As noted previously, 

ignition under these test conditions was characterized by movement of this blowout plate. The 

tests were conducted in the range of 0 to 30,000 ft, in increments of 10,000 ft. At each altitude, 

ignition was attempted at an initial ullage concentration of 20.9% O2 followed by reduced 

oxygen concentrations until ignition was no longer observed under the given test conditions. 

The results from this set of tests are shown in figure 8 as oxygen concentration plotted against 

altitude. 

The data in figure 8 clearly indicate that LOC increases with increasing altitude. However, the 

precise nature of this trend could not be established due to data scatter and an insufficient 

ignition and nonignition criterion. These results were useful in subsequent tests to determine the 

LOC as a function of altitude. The upward trend in LOC is not observed at 30,000 ft in figure 8 

due to an insufficient hydrocarbon sample flow at this low pressure. Prior to continuing with 

further testing, this issue was resolved. 

13
FIGURE 8. LIMITING OXYGEN CONCENTRATION DATA 

RESULTS—ALUMINUM PLATE RELIEF MECHANISM 

To better define the LOC, the aluminum plate pressure relief mechanism was replaced with a foil 

diaphragm. With this new relief mechanism, ignition was defined simply by rupture of the foil,

allowing for a more definitive measure of ignition and nonignition. These tests were carried out 

in a similar fashion as those depicted in figure 8, with the upper limit of testing being at or 

slightly above the LOC determined from the previous tests. This set of tests was also expanded 

to include a higher altitude of approximately 38,000 ft, the upper limit at which the 

instrumentation was capable of accurate vapor measurement. The results are presented in figure

9, again as oxygen concentration plotted against altitude. In addition, figure 10 shows the

minimum O2 concentration resulting in ignition along with the maximum O2 concentration

resulting in nonignition at each altitude. 

FIGURE 9. LIMITING OXYGEN CONCENTRATION DATA RESULTS— 

FOIL DIAPHRAGM RELIEF MECHANISM 

14
FIGURE 10. LIMITING OXYGEN CONCENTRATION DATA RESULTS—MINIMUM 

AND MAXIMUM VALUES FOR IGNITION AND NONIGNITION 

From these results, there is a clear indication that an increase occurs in the LOC as altitude is 

increased. The LOC rises steadily from a value approximately 12% O2 at sea level and 10,000 ft

to approximately 14.5% O2 at 40,000 ft. 

The sea level LOC data is consistent with previous data, as shown in Zinn’s work from 1971 

[10], in which Zinn performed an extensive literature search of several inerting-level requirement

data sets. Zinn found that the resulting LOC determined by these experiments varied 

approximately 1 percent, falling in the 11.5% to 12% O2 range. Military aircraft inerting

systems, however, have used a level of 9% as their design criteria as a result of a Bureau of 

Mines suggestion of using a 20% safety margin [11]. In fact, even when a high-energy 

incendiary projectile is used as the ignition source, much of the research that this 9% value is

based on show little to no gain in lowering the oxygen concentration from 12% to 9% [12 and 

13]. 

While there is not much published data available for the LOC at altitude, Stewart and Starkman 

[14] did perform some altitude work with both carbon dioxide and nitrogen inerting. Their data,

however, was generated by using flame propagation as the ignition and nonignition criteria. If 

any visible flame front occurred within the tank, it was considered an ignition. The resulting

pressure rise was not used as a criterion, and it is noted in their report that at times flame

propagation occurred with little or no resulting pressure rise. As a result of this difference in

criterion, Stewart and Starkman’s data set tends to be lower than the data generated here, starting 

at approximately 9.8% O2 at sea level and increasing to approximately 10.8% at 30,000 ft and

13% at 60,000 ft. While the disparity in criteria does not allow for direct comparison of this data 

to the data presented in this report, it does verify the trend of decreasing inerting-level 

requirements (higher LOC) as altitude is increased. 

15
Figures 11-15 depict the data from these tests as approximated fuel-air mass ratio and volumetric 

fuel vapor concentration versus volumetric oxygen concentration for each of the five altitudes 

tested. A large majority of the tests were conducted at sea level, because this is the most 

important region in the design of an inerting system. From the 50 tests conducted at sea level, 18 

were conducted in the range of 11% to 12.5% O2. Of these 18 tests, only four resulted in 

ignition, and only one of the nine tests at or below 12% O2 ignited. In addition, figure 11 shows 

a series of tests conducted at 21% O2 with varying fuel-air ratios. This short series of tests was 

conducted to determine the approximate LFL of the fuel. From the figure it is evident that this 

value occurs somewhere between a FAR of 0.026 and 0.027. 

FIGURE 11. LIMITING OXYGEN CONCENTRATION DATA RESULTS—FUEL-AIR 

RATIO AND FUEL VAPOR CONCENTRATION VS OXYGEN CONCENTRATION 

(SEA LEVEL) 

16
FIGURE 12. LIMITING OXYGEN CONCENTRATION DATA RESULTS—FUEL-AIR 

RATIO AND FUEL VAPOR CONCENTRATION VS OXYGEN 

CONCENTRATION (10,000 ft) 

FIGURE 13. LIMITING OXYGEN CONCENTRATION DATA RESULTS—FUEL-AIR 

RATIO AND FUEL VAPOR CONCENTRATION VS OXYGEN 

CONCENTRATION (20,000 ft) 

17
FIGURE 14. LIMITING OXYGEN CONCENTRATION DATA RESULTS—FUEL-AIR 

RATIO AND FUEL VAPOR CONCENTRATION VS OXYGEN 

CONCENTRATION (30,000 ft) 

FIGURE 15. LIMITING OXYGEN CONCENTRATION DATA RESULTS—FUEL-AIR 

RATIO AND FUEL VAPOR CONCENTRATION VS 

OXYGEN CONCENTRATION (38,000 ft) 

18
Although excessive amounts of condensation at low altitudes precluded testing at a 

stoichiometric fuel-air mixture, later testing, as discussed in section 4.2.2, showed that the lowest 

values for LOC occurred at a near stoichiometric mixture for a fuel-12% O2 air mixture. 

Upon completion of these LOC tests, it was desired to measure the pressure rises caused by 

ignition, seen at low-oxygen concentrations, and examine the effect of increasing altitude. The

two pressure transducers were used as described in section 2.2. Tests were conducted at altitudes

from 0 to 30,000 ft, with the foil diaphragm acting as the pressure relief mechanism. Testing 

was limited to oxygen levels approximately 1% to 1.5% above the LOC values previously 

determined and shown in figure 10. 

Both transducers recorded similar values, and the averaged results are shown in figures 16 and 

17. Figure 16 depicts the peak pressure rise versus altitude. From this plot, a decrease in the 

peak pressure is observed as altitude is increased from 0 to 30,000 ft. Figure 17 depicts the time

duration to reach the peak pressure plotted versus altitude. The time duration increases as

altitude is increased. 

It should be noted, however, that with these particular tests, after the diaphragm ruptured, the 

transducers were reading the pressure of the entire chamber. It is for this reason that the peak

pressures recorded in figure 16 seem relatively small, and similarly, that the time durations in 

figure 17 are relatively long. Since the vessel volume is approximately 40 times the volume of 

the fuel tank, the peak pressures shown in figure 16 are approximately 1/40 of the potential 

pressure rise occurring in a closed, nonvented environment. This appears to be consistent with 

Shepherd, et al.’s [15] work, in which they recorded pressure rises near 50 psig occurring at 

pressures equivalent to an altitude of approximately 15,000 ft. 

0

0.5

1

1.5

2

2.5

0 10 20

Altitude (kft)

Pressure Rise (psig)

30

FIGURE 16. PEAK PRESSURE RISE VS ALTITUDE AT O2 CONCENTRATIONS 

1% TO 1.5% ABOVE THE LOC 

19
0

2

4

6

8

10

12

0 10 20

Altitude (kft)

Time Duration to Reach Peak Pressure (s)

30

FIGURE 17. IGNITION TIME DURATION VS ALTITUDE AT O2 CONCENTRATIONS 

1% TO 1.5% ABOVE THE LOC 

The pressure rise data was further verified by a brief set of experiments that were conducted 

within the full-pressure vessel with no postignition pressure relief. In these tests, a 3- by 6-foot 

fuel pan was placed inside the vessel with the equivalent fuel loading as in previous tests. 

Heating the fuel was achieved by three of the identical hot plates used in the 9-ft3

 tank attached 

to the bottom of the pan. Ignition was achieved using the same transformer, connected to two 

1/8-in. steel electrodes. Vessel pressure was recorded by a 0 to 200 psi sealed gauge, diaphragmtype transducer. Due to large condensation effects within this chamber, tests were only able to 

be conducted at altitudes above 20,000 ft. The results of these tests can be seen in table 3. 

TABLE 3. NONVENTED, FULL VESSEL IGNITION PRESSURE RESULTS 

Altitude

(thousand ft) 

Oxygen 

Concentration 

Initial 

Pressure 

(psia)

Final 

Pressure 

(psia)

Differential 

Pressure 

(psia)

Differential/Initial 

Pressure 

(psia)

20 21.0% 6.9 33.7 26.8 3.88

20 15.0% 6.8 30.5 23.7 3.49

38 21.0% 3.5 16.1 12.6 3.60

38 17.3% 3.8 16.5 12.7 3.34

Extrapolating the results in figure 16 to include a data point of approximately 0.3 psig at 38,000 ft, 

it can be seen that at both altitudes the nonvented data is approximately 42 times the vented

pressure results. This data also shows that the ullage oxygen concentration has little or no effect

20
on the resulting pressure rise from ignition, and the ratio of differential to initial pressure does 

not vary much with either altitude or oxygen concentration. 

4.2.2 Engine Spark Igniter Tests.

Results of tests conducted with the J-57 engine igniter are shown in figure 18. In an attempt to 

verify that testing was being performed at the optimum hydrocarbon concentration, these tests 

were conducted within several fuel vapor concentration ranges. These consisted of those at 

levels near that of a stoichiometric 12% O2 air mixture (i.e., 0.035 < FAR < 0.04), those at levels

near that of a stoichiometric 21% O2 air mixture (i.e., 0.065 < FAR < 0.07), and several that fell

between these two ranges. 

FIGURE 18. ENGINE IGNITER TEST RESULTS (SEA LEVEL) 

Due to the high amount of condensation occurring in the test tank, it was necessary to slightly 

modify the test fuel to be able to achieve those higher fuel vapor concentrations. Being that 

hexane has flammability properties that closely mimic that of jet fuel and has a rather low boiling 

point, it was decided to spike the test fuel with varying amounts of hexane, as noted in the figure. 

To verify that this modification did not drastically affect the fuel, distillation curves and flash 

points were taken of the JP-8 and JP-8/Hexane mixtures. The results of these tests are shown in 

figure 19. From this figure, it is observed that the addition of hexane affected the fuel primarily 

by increasing the quantity of low-boiling point components, thereby reducing the fuel’s flash 

point. Above 20% distillation, however, little effect is seen between the different JP-8/Hexane 

mixtures. 

21
0

100

200

300

400

500

600

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

% Distilled

Temperature (°F)

JP-8 (No Hexane Added), FP = 114.8°F

JP-8 (20 cc Hexane Added), FP = 91.8°F

JP-8 (30 cc Hexane Added), FP = 81.7°F

JP-8 (40 Hexane Added), FP = 78.3°F

JP-8 (100 cc Hexane Added), FFlash lashpoi Pointnt Unk Unknonowwnn

FIGURE 19. ASTM D 86 DISTILLATION CURVES AND FLASH POINT DATA OF 

JP-8 AND HEXANE MIXTURES

There were 15 tests conducted at the stoichiometric 21% O2 mixture, consisting of ullage O2

concentrations from 11.9% to 13.7%. Not one of these 15 tests resulted in ignition. Of the 18 

tests conducted at FARs below this, the lowest ullage O2 concentration resulting in ignition was

12.3%. Interestingly, this value of the LOC occurred at a near stoichiometric mixture for a fuel12% O2 air mixture as opposed to the initial thought that a stoichiometric mixture for 21% air 

would need to be used to obtain the lowest LOC value. It is believed that the inerting agent has 

effectively lowered the upper flammability limit (UFL), thereby resulting in a mixture that is too 

rich at the higher vapor concentrations. 

4.2.3 Short-Duration Oil Burner Transformer Tests.

Table 4 summarizes the results of six tests conducted using the oil burner transformer with a

0.1-second arc duration. The tests were performed at near stoichiometric mixtures for a fuel12% O2 background environment and at ullage O2 concentrations ranging from 12.5% to 14.3% 

at sea level conditions. Of these tests, three resulted in ignition, all at O2 concentrations greater 

than 12.8%. Below this value, no ignition was achieved. 

TABLE 4. SHORT-DURATION OIL BURNER TRANSFORMER TEST RESULTS 

O2

Concentration 

Total 

Hydrocarbons 

(ppm-C3H8) 

Approximated

% Volume of 

Jet A 

Approximated 

Fuel-Air Mass 

Ratio Ignition?

12.5% 23000 0.7667 0.033 No

12.8% 22000 0.7333 0.032 No

12.8% 23500 0.7833 0.034 No

14.3% 24500 0.8167 0.035 Yes

13.2% 23000 0.7667 0.033 Yes

12.9% 24000 0.8000 0.034 Yes

22
4.2.4 Four Hundred-Cycle Short to Ground Ignition Tests. 

Table 5 summarizes the results of tests conducted using the 400-cycle short to ground spark 

generation method. Again, tests were performed at near stoichiometric mixtures for a fuel-12% 

O2 background environment. Ullage O2 concentrations ranged from 11.0% to 13.6% at sea level 

conditions. In this data, the first observation of an ignition occurring below 12.0% O2 is noted, 

with one of the five ignitions occurring at 11.9% O2. However, it is also observed that there are 

numerous nonignitions at values of 12.1% O2 and under. This single ignition event below 12% 

O2 is, therefore, attributed to inherent error in the oxygen measurement system, whose sensitivity

is stated to be ±1% of the full-scale value (25% O2). Though the ignition source was four to five 

times more energetic than the largest spark used in previous attempts, the LOC did not change in 

any significant manner. 

TABLE 5. FOUR HUNDRED-CYCLE SHORT TEST RESULTS 

O2

Concentration

Total 

Hydrocarbons 

(ppm-C3H8)

Approximated

% Volume of 

Jet A

Approximated 

Fuel-Air Mass 

Ratio Ignition?

11.00% 24,600 0.8200 0.035 No

11.80% 24,500 0.8167 0.035 No

12.00% 23,000 0.7667 0.033 No

12.10% 21,000 0.7000 0.030 No

12.10% 22,000 0.7333 0.032 No

12.10% 22,000 0.7333 0.032 No

12.40% 23,500 0.7833 0.034 No

12.40% 23,900 0.7967 0.034 No

11.90% 23,000 0.7667 0.033 Yes

12.20% 22,000 0.7333 0.032 Yes

12.40% 21,500 0.7167 0.031 Yes

13.20% 24,600 0.8200 0.035 Yes

13.60% 22,000 0.7333 0.032 Yes

4.2.5 Hot-Surface Vapor Ignition Tests.

To ensure that the heated surface was a credible ignition source, the initial HSVI test was 

conducted in a noninerted atmosphere. The results of these tests are summarized in table 6. A

violent ignition was observed at 21% O2 as the HST approached approximately 1350°F. Six 

subsequent tests were performed with ullage O2 concentrations ranging from 11.3% to 14.0%, 

again with near stoichiometric concentrations for a fuel-12% O2 air mixture. During all the tests 

(except for the tests at 11.5% and 11.3% O2), as the HST approached approximately 1200°F, 

some slight puffs of smoke could be seen emanating from the vent of the fuel tank; however, no 

ignition events were observed in any of the tests, even as the surface was heated above 1400°F. 

23
TABLE 6. HOT-SURFACE VAPOR IGNITION TEST RESULTS 

O2

Concentration 

Total 

Hydrocarbons 

(ppm-C3H8) 

Approximated 

% Volume of 

Jet A 

Approximated 

Fuel-Air Mass 

Ratio 

Maximum 

HST Ignition?

21% 25,500 0.8500 0.037 1350 Yes

14% 26,000 0.8667 0.037 1430 No

13.1% 23,000 0.7667 0.033 1420 No

12.7% 24,000 0.8000 0.035 1440 No

11.5% 26,000 0.8667 0.037 1430 No

11.3% 21,500 0.7167 0.031 1420 No

5. CONCLUSIONS.

From these tests, it was determined that the limiting oxygen concentration (LOC) at sea level 

through 10 kft is approximately 12% O2, with a linear increase from 12% at 10 kft to 

approximately 14.5% at 40 kft. Tests with various sparks and arcs, with energies ranging from

0.08-2.8 Joules under sea level conditions, showed little variation in results with the LOC 

ranging from 11.9% to 12.8%. The single ignition event falling below 12% O2 is attributed to 

inherent error in the oxygen measurement system, whose sensitivity is stated to be ±1% of the 

full-scale value (25% O2). Also, a heated surface capable of igniting a fuel-air mixture proved

insufficient for ignition in a tank inerted to just 14% O2. Pressure data showed that peak 

pressures resulting from ignition at oxygen concentrations 1% to 1.5% above LOC values 

decreased as the altitude was increased to 30,000 ft, while the time duration to reach the peak 

pressure increased. 

6. REFERENCES.

1. “Accident Report: In-Flight Breakup Over the Atlantic Ocean Trans World Airlines 

Flight 800 Boeing 747-131, N93119, near East Moriches, New York, July 17, 1996,” 

National Transportation Safety Board, NTSB/AAR-00/03, August 23, 2000. 

2. Aviation Rulemaking Advisory Committee, “Fuel Tank Harmonization Working Group, 

Final Report,” ARAC, 1998. 

3. Fuel Flammability Task Group, “A Review of the Flammability Hazard of Jet A Fuel 

Vapor in Civil Transport Aircraft Fuel Tanks,” FAA Report DOT/FAA/AR-98/26, June 

1998. 

4. “Handbook of Aviation Fuel Properties,” Coordinating Research Council Report No. 

530, 1983. 

5. Lewis, B. and von Elbe, G., Combustion, Flames and Explosions of Gases, 3rd edition, 

Academic Press, 1987. 

6. Polymeropoulos, C.E., “Multi-Component Fuel Vaporization in a Simulated Aircraft Fuel 

Tank,” Third International Aircraft Fire and Cabin Safety Research Conference 

Proceedings, FAA report DOT/FAA/AR-02/48, October 2001. 

24
7. Esseghir, M. and Polymeropoulos, C. E., “Spark Ignition of Near the Lean Limit CH4-Air 

Mixtures at Low Pressures,” Combustion and Flame, Vol. 73, 1988. 

8. Shepherd, Krok, Lee, Brown, Lynch, Samaras, and Birky, “Results of 1/4 Scale 

Experiments, Vapor Simulant and Liquid Jet A Tests,” NTSB Docket No. SA-516, 

Exhibit, No. 20O, 2000. 

9. Thomas, I., “Fuel Air Ratio Calculator,” http://www.fire.tc.faa.gov/systems/fueltank/ 

FAR1g.xls, October 30, 2001 Version. 

10. Zinn Jr., S.V., “Inerted Fuel Tank Oxygen Concentration Requirements,” FAA Report 

FAA-RD-71-42, August 1971. 

11. Kuchta, J.M., “Oxygen Dilution Requirements for Inerting Aircraft Fuel Tanks,” Bureau 

of Mines Safety Research Center, in: Second Conference on Fuel System Fire Safety, 

Washington, D.C., FAA, pp. 85-115, May 1970. 

12. Tyson, J.H. and Barnes, J.F., “The Effectiveness of Ullage Nitrogen-Inerting Systems

Against 30-mm High-Explosive Incendiary Projectiles-Final Report,” NWC TP 7129, 

May 1991. 

13. Anderson, C.L., Test and Evaluation of Halon 1301 and Nitrogen Inerting Against 

23 mm HEI Projectiles,” AFFDL-TR-78-66, May 1978. 

14. Stewart, P.B. and Starkman, E.S., “Inerting Conditions for Aircraft Fuel Tanks,” WADC 

Technical Report No. 55-418, September 1955. 

15. Shepherd, J.E., Krok, J.C., and Lee, J.J., “Jet A Explosion Experiments: Laboratory 

Testing,” NTSB Docket No. SA-516, Exhibit No. 20D, 1997. 

25/26
APPENDIX A—COMMERCIAL AND MILITARY AVIATION FUEL SPECIFICATIONS

ASTM D 1655 Detailed Specifications of Commercial Aviation Turbine Fuels 

Property Jet A or Jet A-1 Jet B 

COMPOSITION 

Acidity, total mg KOH/g

Aromatics, vol % 

Sulfur, mercaptan, weight % 

Sulfur, total weight % 

Max 

Max 

Max 

Max 

0.10 

25 

0.003 

0.30 

... 

25 

0.003 

0.3 

VOLATILITY 

Distillation temperature °C: 

10% recovered, temperature 

20% recovered, temperature 

50% recovered, temperature 

90% recovered, temperature 

Final boiling point, temperature 

Distillation residue, % 

Distillation loss, % 

Flash point, °C 

Density at 15°C, kg/m3

Vapor pressure, 38°C, kPa 

Max 

Max 

Max 

Max 

Max 

Max 

Max 

Min 

Max 

205 

... 

Report 

Report 

300 

1.5 

1.5 

38 

775 to 840 

... 

... 

145 

190 

245 

... 

1.5 

1.5 

... 

751 to 802 

21 

FLUIDITY 

Freezing point, °C 

Viscosity -20°C, mm2

/s 

Max 

Max 

-40 Jet A 

-47 Jet A-1 

8.0 

-50 

COMBUSTION 

Net heat of combustion, MJ/kg 

One of the following requirements shall be met: 

Luminometer number, or 

(2) Smoke point, or 

(3) Smoke point, mm, and 

_________Naphthaleness, vol % 

Min 

Min 

Min 

Min 

Max 

42.8 

45 

25 

18 

3.0 

42.8 

45 

25 

18 

3.0 

CORROSION 

Copper strip, 2 h at 100°C Max No. 1 No. 1 

THERMAL STABILITY 

JFTOT (2.5 h at control temperature of 260°C min) 

Filter pressure drop, mm Hg 

Tube deposits less than Max 25 

3 

25 

3 

CONTAMINANTS 

Existent gum, mg/100 mL 

Water reaction: 

 Interface rating 

Max 

Max 

7 

1b 

7 

1b 

A-1
Detailed U.S. Military Requirements of Aviation Turbine Fuels as Taken From Reference A-1 

Property JP-4 JP-5 JP-8

COMPOSITION 

Acidity, total mg KOH/g

Aromatics, vol % 

Sulfur, mercaptan, weight % 

Sulfur, total weight % 

Color, Saybolt 

Max 

Max 

Max 

Max 

Max 

0.015 

25.0 

5.0 

0.001 

0.4 

Report 

0.015 

25.0 

5.0 

0.001 

0.4 

Report 

0.015 

25.0 

5.0 

0.001 

0.3 

Report 

VOLATILITY 

Distillation temperature °C: 

Initial boiling point, temperature 

10% recovered, temperature 

20% recovered, temperature 

50% recovered, temperature 

90% recovered, temperature 

Final boiling point, temperature 

Distillation residue, % 

Distillation loss, % 

Explosiveness, % 

Flash point, °C 

Gravity, °API (15°C) 

Density at 15°C, kg/m3

Vapor pressure, 37.8°C, kPa (psi) 

Max 

Max 

Max 

Max 

Max 

Max 

Max 

Max 

Max 

Min 

Max 

Max 

Report 

Report 

145 

190 

245 

270 

1.5 

1.5 

... 

... 

45-57 

751-802 

14-21 

Report 

205 

Report 

Report 

Report 

290 

... 

... 

50 

60 

36-48 

788-845 

... 

Report 

205 

Report 

Report 

Report 

300 

1.5 

1.5 

38 

37-51 

775-840 

FLUIDITY 

Freezing point, °C 

Viscosity -20°C, mm2

/s 

Max 

Max 

-58 

... 

-46 

8.5 

-50 

8.0 

COMBUSTION 

Aniline-gravity product, or 

Net heat of combustion, MJ/kg 

Smoke point, or 

Hydrogen content (wt %) 

Min 

Min 

Min 

Min 

5250 

42.8 

20.0 

13.6 

4500 

42.6 

19.0 

13.5 

42.8 

19.0 

13.5 

CORROSION 

Copper strip, 2 h at 100°C Max 1b 1b 1b 

THERMAL STABILITY 

JFTOT ∆P (mm Hg) 

JFTOT Tube Color Code 

Max 

Max 

25 

<3 

25 

<3 

25 

<3 

CONTAMINANTS 

Existent gum, mg/100 mL 

Particulates (mg/liter)

Water reaction interface

Water separation index modified 

Filtration time (minutes) 

Max 

Max 

Max 

Min 

Max 

7 

1 

1b 

70 

15 

7 

1 

1b 

85 

... 

7 

1 

1b 

70 

... 

A-2
Detailed U.S. Military Requirements of Aviation Turbine Fuels as Taken From Reference A-1 

Property JP-4 JP-5 JP-8

ADDITIVES 

Anti-icing (vol %) 

Antioxidant 

Corrosion inhibitor 

Metal deactivator 

Antistatic 

0.10-0.15 

Required 

Required 

Option 

Required 

0.10-0.15 

Required 

Required 

Option 

... 

0.10-0.15 

Option 

Required 

Option 

Required 

OTHER 

Conductivity (pS/m

Service 

NATO Code No. 

200-600 

All 

F-40 

... 

Navy 

F-44 

200-600 

USAF 

F-34; F-35 

REFERENCES

A-1. “Handbook of Aviation Fuel Properties,” Coordinating Research Council Report No. 

530, 1983. 

A-3/A-4
Ignition Source 

Alt 

(kft) %O2

Total HC 

ppm-C

H3 8

Approximate

d % 

Volume of J

et A 

Approximate

d

Fuel-Air Mass 

R

atio Ignition?

Foil/Plate

? Notes 

Oil Burner (Long) 0 13.30% 24,000 0.8000 0.035 No Plate Oil Burner (Long) 0 12.50% 27,000 0.9000 0.039 No Plate Oil Burner (Long) 0 13.00% 27,000 0.9000 0.039 No Plate Oil Burner (Long) 0 21.00% 17,500 0.5833 0.025 No Foil Oil Burner (Long) 0 21.00% 18,000 0.6000 0.026 No Foil Oil Burner (Long) 0 12.00% 19,000 0.6333 0.027 No Foil Oil Burner (Long) 0 12.50% 19,800 0.6600 0.028 No Foil Oil Burner (Long) 0 12.20% 19,900 0.6633 0.029 No Foil Oil Burner (Long) 0 12.30% 20,600 0.6867 0.030 No Foil Oil Burner (Long) 0 12.30% 22,300 0.7433 0.032 No Foil Oil Burner (Long) 0 11.30% 24,100 0.8033 0.035 No Foil Oil Burner (Long) 0 12.20% 24,500 0.8167 0.035 No Foil Oil Burner (Long) 0 11.80% 24,500 0.8167 0.035 No Foil Oil Burner (Long) 0 11.40% 25,000 0.8333 0.036 No Foil Oil Burner (Long) 0 11.20% 27,000 0.9000 0.039 no Foil Oil Burner (Long) 0 11.20% 28,000 0.9333 0.040 no Foil Oil Burner (Long) 0 12.10% 30,000 1.0000 0.043 No Foil Oil Burner (Long) 0 12.60% 30,000 1.0000 0.043 No Foil Oil Burner (Long) 0 11.80% 32,000 1.0667 0.046 No Foil Oil Burner (Long) 0 12.00% 32,000 1.0667 0.046 No Foil Oil Burner (Long) 0 12.70% 34,000 1.1333 0.049 No Foil Oil Burner (Long) 0 18.00% 23,000 0.7667 0.033 Yes Plate Oil Burner (Long) 0 15.50% 23,500 0.7833 0.034 Yes Plate Oil Burner (Long) 0 14.50% 23,500 0.7833 0.034 Yes Plate Oil Burner (Long) 0 21.00% 24,000 0.8000 0.035 Yes Plate Oil Burner (Long) 0 14.50% 24,000 0.8000 0.035 yes Plate Oil Burner (Long) 0 16.35% 24,000 0.8000 0.035 yes Plate Oil Burner (Long) 0 21.00% 24,000 0.8000 0.035 yes Plate 

APPENDIX B—JP-8 LIQUID FUEL TEST DATA

B-1
Ignition Source 

Alt 

(kft) %O2

Total HC 

ppm-C

H3 8

Approximate

d % 

Volume of J

et A 

Approximate

d

Fuel-Air Mass 

R

atio Ignition?

Foil/Plate

? Notes 

Oil Burner (Long) 0 14.50% 24,300 0.8100 0.035 yes Plate Oil Burner (Long) 0 19.65% 25,000 0.8333 0.036 yes Plate 

Oil Burner (Long) 0 16.00% 25,500 0.8500 0.037 Yes Plate Oil Burner (Long) 0 13.60% 24,000 0.8000 0.035 Yes Foil Oil Burner (Long) 0 21.00% 19,300 0.6433 0.028 Yes Foil Oil Burner (Long) 0 21.00% 19,400 0.6467 0.028 Yes Foil Oil Burner (Long) 0 13.10% 20,000 0.6667 0.029 Yes Foil Oil Burner (Long) 0 21.00% 21,000 0.7000 0.030 Yes Foil Oil Burner (Long) 0 12.60% 22,300 0.7433 0.032 Yes Foil Oil Burner (Long) 0 21.00% 23,500 0.7833 0.034 Yes Foil Oil Burner (Long) 0 21.00% 24,000 0.8000 0.035 Yes Foil Oil Burner (Long) 0 13.20% 25,000 0.8333 0.036 Yes Foil Oil Burner (Long) 0 14.30% 25,000 0.8333 0.036 Yes Foil Oil Burner (Long) 0 12.50% 26,000 0.8667 0.037 Yes Foil Oil Burner (Long) 0 13.00% 23,000 0.7667 0.033 Yes Foil Oil Burner (Long) 0 12.00% 26,800 0.8933 0.039 Yes Foil Oil Burner (Long) 0 12.10% 27,000 0.9000 0.039 Yes Foil Oil Burner (Long) 0 15.20% 27,000 0.9000 0.039 Yes Foil Oil Burner (Long) 0 12.30% 28,300 0.9433 0.041 Yes Foil Oil Burner (Long) 0 13.70% 29,000 0.9667 0.042 Yes Foil Oil Burner (Long) 0 12.80% 30,000 1.0000 0.043 Yes Foil Oil Burner (Long) 0 14.70% 36,000 1.2000 0.052 Yes Foil Oil Burner (Long) 10 13.3% 25,000 0.8333 0.036 No Foil Oil Burner (Long) 10 12.5% 27,000 0.9000 0.039 No Foil Oil Burner (Long) 10 11.5% 28,000 0.9333 0.040 No Foil Oil Burner (Long) 10 11.5% 27,000 0.9000 0.039 No Foil Oil Burner (Long) 10 11.0% 38,000 1.2667 0.055 No Foil Oil Burner (Long) 10 12.3% 35,000 1.1667 0.050 No Plate Oil Burner (Long) 10 12.3% 35,000 1.1667 0.050 Yes Foil Oil Burner (Long) 10 12.0% 35,000 1.1667 0.050 Yes Foil 

B-2
Ignition Source 

Alt 

(kft) %O

Total HC 

ppm-C

H

Approximate

d % 

Volume of J

et A 

Approximate

d

Fuel-Air Mass 

R

atio Ignition?

Foil/Plate

? Notes 

B-3

2 3 8

Oil Burner (Long) 10 21.1% 25,000 0.8333 0.036 Yes Plate Oil Burner (Long) 10 17.9% 26,000 0.8667 0.037 Yes Plate Oil Burner (Long) 10 16.3% 25,500 0.8500 0.037 Yes Plate Oil Burner (Long) 10 13.2% 24,000 0.8000 0.035 Yes Plate Oil Burner (Long) 10 12.4% 24,000 0.8000 0.035 Yes Plate Oil Burner (Long) 20 11.50% 27,000 0.9000 0.039 No Foil Oil Burner (Long) 20 11.20% 29,000 0.9667 0.042 No Foil Oil Burner (Long) 20 12.1% 33,000 1.1000 0.047 No Foil Oil Burner (Long) 20 13.0% 34,000 1.1333 0.049 No Foil Oil Burner (Long) 20 16.0% 26,000 0.8667 0.037 No Plate Oil Burner (Long) 20 17.0% 30,000 1.0000 0.043 No Plate Oil Burner (Long) 20 14.4% 30,000 1.0000 0.043 No Plate Oil Burner (Long) 20 12.9% 30,000 1.0000 0.043 No Plate Oil Burner (Long) 20 12.6% 31,000 1.0333 0.045 No Plate Oil Burner (Long) 20 11.8% 34,000 1.1333 0.049 No Plate Oil Burner (Long) 20 13.8% 27,000 0.9000 0.039 Yes Foil Oil Burner (Long) 20 13.60% 27,000 0.9000 0.039 Yes Foil Oil Burner (Long) 20 16.0% 33,000 1.1000 0.047 Yes Plate Oil Burner (Long) 20 21.0% N/A N/A N/A Yes Plate Oil Burner (Long) 20 18.5% N/A N/A N/A Yes Plate Oil Burner (Long) 30 13.7% 35,000 1.1667 0.050 No Foil Oil Burner (Long) 30 13.90% 30,000 1.0000 0.043 No Foil Oil Burner (Long) 30 12.70% 49,000 1.6333 0.070 No Foil Oil Burner (Long) 30 12.25% 33,000 1.1000 0.047 No Foil Oil Burner (Long) 30 13.5% 47,000 1.5667 0.068 No Foil Oil Burner (Long) 30 14.3% 54,000 1.8000 0.078 No Foil Oil Burner (Long) 30 14.6% 40,000 1.3333 0.058 No Foil Oil Burner (Long) 30 14.8% 52,000 1.7333 0.075 No Foil Oil Burner (Long) 30 13.4% 49,000 1.6333 0.070 No Foil Oil Burner (Long) 30 14.3% 39,000 1.3000 0.056 No Foil 
Ignition Source 

Alt 

(kft) %O

Total HC 

ppm-C

H

Approximate

d % 

Volume of J

et A 

Approximate

d

Fuel-Air Mass 

R

atio Ignition?

Foil/Plate

? Notes 

B-4

2 3 8

Oil Burner (Long) 30 14.0% 43,000 1.4333 0.062 No Foil Oil Burner (Long) 30 18.0% 32,000 1.0667 0.046 No Plate Oil Burner (Long) 30 12.0% 43,500 1.4500 0.063 No Plate Oil Burner (Long) 30 13.4% 45,000 1.5000 0.065 No Plate Oil Burner (Long) 30 14.10% 33,000 1.1000 0.047 Yes Foil Oil Burner (Long) 30 14.10% 37,000 1.2333 0.053 Yes Foil Oil Burner (Long) 30 16.0% 47,000 1.5667 0.068 Yes Foil Oil Burner (Long) 30 15.4% 32,000 1.0667 0.046 Yes Foil Oil Burner (Long) 30 15.1% 30,000 1.0000 0.043 Yes Foil Oil Burner (Long) 30 14.2% 36,000 1.2000 0.052 Yes Foil Oil Burner (Long) 30 14.4% 43,000 1.4333 0.062 Yes Foil Oil Burner (Long) 30 21.0% N/A N/A N/A Yes Plate Oil Burner (Long) 30 16.0% 26,000 0.8667 0.037 Yes Plate Oil Burner (Long) 30 15.5% N/A N/A N/A Yes Plate Oil Burner (Long) 38 17.20% 46,000 1.5333 0.066 No Foil Oil Burner (Long) 38 14.70% 45,000 1.5000 0.065 no Foil Oil Burner (Long) 38 15.40% 47,000 1.5667 0.068 no Foil Oil Burner (Long) 38 15.40% 48,000 1.6000 0.069 no Foil Oil Burner (Long) 38 21.00% 23,000 0.7667 0.033 no Foil Oil Burner (Long) 38 21.00% 22,800 0.7600 0.033 no Foil Oil Burner (Long) 38 16.10% 51,000 1.7000 0.073 yes Foil Oil Burner (Long) 38 16.40% 45,000 1.5000 0.065 yes Foil Oil Burner (Long) 38 15.70% 45,000 1.5000 0.065 yes Foil Oil Burner (Long) 38 16.30% 1.8333 0.079 yes Foil Oil Burner (Long) 38 16.00% 45,000 1.5000 0.065 yes Foil Oil Burner (Long) 38 16.00% 40,000 1.3333 0.058 yes Foil Oil Burner (Long) 38 15.70% 42,500 1.4167 0.061 yes Foil Oil Burner (Long) 38 15.60% 40,000 1.3333 0.058 yes Foil Oil Burner (Long) 38 21.00% 34,000 1.1333 0.049 yes Foil Oil Burner (Long) 38 21.00% 34,000 1.1333 0.049 yes Foil 

55,000 
Ignition Source 

Alt 

(kft) %O

Total HC 

ppm-C

H

Approximate

d % 

Volume of J

et A 

Approximate

d

Fuel-Air Mass 

R

atio Ignition?

Foil/Plate

? Notes 

B-5

2 3 8

Oil Burner (Long) 38 21.00% 29,500 0.9833 0.042 yes Foil Oil Burner (Long) 38 21.00% 29,000 0.9667 0.042 yes Foil Oil Burner (Long) 38 21.00% 25,000 0.8333 0.036 yes Foil Oil Burner (Long) 38 21.00% 24,500 0.8167 0.035 yes Foil 

Oil Burner (Short) 0 12.50% 23,000 0.7667 0.033 No Foil Oil Burner (Short) 0 12.80% 22,000 0.7333 0.032 No Foil Oil Burner (Short) 0 12.80% 23,500 0.7833 0.034 No Foil Oil Burner (Short) 0 14.30% 24,500 0.8167 0.035 Yes Foil Oil Burner (Short) 0 13.20% 23,000 0.7667 0.033 Yes Foil Oil Burner (Short) 0 12.90% 24,000 0.8000 0.035 Yes Foil 

J-57 En

gine

Igniter 

0 11.7

0

%

2

4,0

0

0

0.8

0

0

0

0.0

3

5

N

o

F

oil

J-57 En

gine

Igniter 

0 11.7

0

%

2

4,0

0

0

0.8

0

0

0

0.0

3

5

N

o

F

oil

J-57 En

gine

Igniter 0 12.3

0

%

2

4,0

0

0

0.8

0

0

0

0.0

3

5

N

o

F

oil

J-57 En

gine

Igniter 

0 12.3

0

%

2

4,5

0

0

0.816

7

0.0

3

5

N

o

F

oil

J-57 En

gine

Igniter 0 12.2

0

%

2

6,0

0

0

0.8

6

6

7

0.0

3

7

N

o

F

oil

J-57 En

gine

Igniter 

0 12.3

0

%

2

8,0

0

0

0.9

3

3

3

0.0

4

0

N

o

F

oil

30 cc of Hexane added to fuel. 

J-57 En

gine

Igniter 

0 12.10

%

3

2,0

0

0 1.0

6

6

7

0.0

4

6

N

o

F

oil

40 cc of Hexane added to fuel. 

J-57 En

gine

Igniter 0 12.0

0

%

3

8,0

0

0 1.2

6

6

7

0.0

5

5

N

o

F

oil

40 cc of Hexane added to fuel. 

J-57 En

gine

Igniter 

0 12.5

0

%

4

5,5

0

0 1.516

7

0.0

6

5

N

o

F

oil

100 cc of Hexane added to fuel. 

J-57 En

gine

Igniter 

0 12.8

0

%

4

5,5

0

0 1.516

7

0.0

6

5

N

o

F

oil

100 cc of Hexane added to fuel. 

J-57 En

gine

Igniter 0 12.3

0

%

4

6,0

0

0 1.5

3

3

3

0.0

6

6

N

o

F

oil

100 cc of Hexane added to fuel. 
Ignition Source 

Alt 

(kft) %O

Total HC 

ppm-C

H

Approximate

d % 

Volume of J

et A 

Approximate

d

Fuel-Air Mass 

R

atio Ignition?

Foil/Plate

? Notes 

B-6

2 3 8

J-57 En

gine

Igniter 

0 12.3

0

%

4

6,0

0

0 1.5

3

3

3

0.0

6

6

N

o

F

oil

100 cc of Hexane added to fuel. 

J-57 En

gine

Igniter 0 13.0

5

%

4

6,0

0

0 1.5

3

3

3

0.0

6

6

N

o

F

oil

100 cc of Hexane added to fuel. 

J-57 En

gine

Igniter 

0 13.7

0

%

4

6,0

0

0 1.5

3

3

3

0.0

6

6

N

o

F

oil

100 cc of Hexane added to fuel. 

J-57 En

gine

Igniter 

0 12.0

0

%

4

6,5

0

0 1.5

5

0

0

0.0

6

7

N

o

F

oil

100 cc of Hexane added to fuel. 

J-57 En

gine

Igniter 0 12.3

0

%

4

6,5

0

0 1.5

5

0

0

0.0

6

7

N

o

F

oil

100 cc of Hexane added to fuel. 

J-57 En

gine

Igniter 

0 12.6

5

%

4

6,5

0

0 1.5

5

0

0

0.0

6

7

N

o

F

oil

100 cc of Hexane added to fuel. 

J-57 En

gine

Igniter 0 11.9

0

%

4

8,0

0

0 1.6

0

0

0

0.0

6

9

N

o

F

oil

100 cc of Hexane added to fuel. 

J-57 En

gine

Igniter 

0 11.9

0

%

4

8,0

0

0 1.6

0

0

0

0.0

6

9

N

o

F

oil

100 cc of Hexane added to fuel. 

J-57 En

gine

Igniter 

0 12.10

%

4

8,0

0

0 1.6

0

0

0

0.0

6

9

N

o

F

oil

100 cc of Hexane added to fuel. 

J-57 En

gine

Igniter 0 12.4

0

%

4

8,0

0

0 1.6

0

0

0

0.0

6

9

N

o

F

oil

100 cc of Hexane added to fuel. 

J-57 En

gine

Igniter 

0 12.8

0

%

4

8,0

0

0 1.6

0

0

0

0.0

6

9

N

o

F

oil

100 cc of Hexane added to fuel. 

J-57 En

gine

Igniter 

0 12.10

%

4

9,0

0

0 1.6

3

3

3

0.0

7

0

N

o

F

oil

100 cc of Hexane added to fuel. 

J-57 En

gine

Igniter 0 12.7

0

%

4

9,0

0

0 1.6

3

3

3

0.0

7

0

N

o

F

oil

100 cc of Hexane added to fuel. 

J-57 En

gine

Igniter 

0 12.3

5

%

2

3,0

0

0

0.7

6

6

7

0.0

3

3

Y

es F

oil

J-57 En

gine

Igniter 

0 12.5

0

%

2

3,0

0

0

0.7

6

6

7

0.0

3

3

Y

es F

oil

J-57 En

gine

Igniter 

0 12.5

5

%

2

3,0

0

0

0.7

6

6

7

0.0

3

3

Y

es F

oil

J-57 En

gine

Igniter 

0 12.8

0

%

2

3,5

0

0

0.7

8

3

3

0.0

3

4

Y

es F

oil
Ignition Source 

Alt 

(kft) %O2

Total HC 

ppm-C

H3 8

Approximate

d % 

Volume of J

et A 

Approximate

d

Fuel-Air Mass 

R

atio Ignition?

Foil/Plate

? Notes 

J-57 En

gine

Igniter 

0 12.5

0

%

2

5,0

0

0

0.8

3

3

3

0.0

3

6

Y

es F

oil

20 cc of Hexane added to fuel. 

J-57 En

gine

Igniter 

0 12.8

5

%

2

8,0

0

0

0.9

3

3

3

0.0

4

0

Y

es F

oil

J-57 En

gine

Igniter 0 12.5

0

%

3

0,0

0

0 1.0

0

0

0

0.0

4

3

Y

es F

oil

20 cc of Hexane added to fuel. 

J-57 En

gine

Igniter 

0 12.6

0

%

3

0,0

0

0 1.0

0

0

0

0.0

4

3

Y

es F

oil

20 cc of Hexane added to fuel. 

J-57 En

gine

Igniter 

0 12.4

0

%

31,5

0

0 1.0

5

0

0

0.0

4

5

Y

es F

oil

20 cc of Hexane added to fuel. 

400-Cycle Short 0 11.00% 24,600 0.8200 0.035 No Foil 400-Cycle Short 0 11.80% 24,500 0.8167 0.035 No Foil 400-Cycle Short 0 12.00% 23,000 0.7667 0.033 No Foil 400-Cycle Short 0 12.10% 21,000 0.7000 0.030 No Foil 400-Cycle Short 0 12.10% 22,000 0.7333 0.032 No Foil 400-Cycle Short 0 12.10% 22,000 0.7333 0.032 No Foil 400-Cycle Short 0 12.40% 23,500 0.7833 0.034 No Foil 400-Cycle Short 0 12.40% 23,900 0.7967 0.034 No Foil 400-Cycle Short 0 11.90% 23,000 0.7667 0.033 Yes Foil 400-Cycle Short 0 12.20% 22,000 0.7333 0.032 Yes Foil 400-Cycle Short 0 12.40% 21,500 0.7167 0.031 Yes Foil 400-Cycle Short 0 13.20% 24,600 0.8200 0.035 Yes Foil 400-Cycle Short 0 13.60% 22,000 0.7333 0.032 Yes Foil 

B-7/B-8