UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

NATIONAL VEHICLE AND FUEL EMISSIONS LABORATORY

2565 PLYMOUTH ROAD

ANN ARBOR, MI 48105-2498

 OFFICE OF

 AIR AND RADIATION

May 27, 2015

MEMORANDUM

SUBJECT: Vocational Vehicle Aerodynamic Testing Program

FROM: Lauren Steele, Environmental Engineer, OTAQ/ASD

TO: Greenhouse Gas Emissions Standards and Fuel Efficiency Standards for Medium- and 

Heavy-Duty Engines and Vehicles - Phase 2 - Docket EPA-HQ-OAR-2014-0827

Introduction

This memorandum describes a possible approach that EPA and NHTSA could use to recognize 

the fuel efficiency and GHG emission improvements from use of aerodynamic devices on vocational 

vehicles as part of the Phase 2 program. The data summarized below are from work completed as of 

March 2015 under an agreement with the California Air Resource Board (ARB) the National Renewable 

Energy Laboratory (NREL). NREL performed a series of coastdown tests on heavy-duty vocational 

vehicles with and without aerodynamic improvement devices to assess their performance. Excerpts of 

progress reports from which this summary is derived are attached as an appendix to this memorandum.

The devices tested were not intended to include all aerodynamic devices available for vocational 

vehicles, rather they are a sampling of the most common types of technologies that are currently

commercially available. Recognition of vocational aerodynamic technology within the Phase 2 GHG 

program would not need to be based solely on data obtained through this ARB-NREL agreement. 

Should other data become available, it would be taken into consideration as well.

Background

The vast majority of aerodynamic improvement technologies that have been evaluated through 

U.S. EPA’s SmartWay program and for compliance with the Phase 1 heavy-duty vehicle greenhouse gas 

standards have been devices primarily intended for heavy-duty Class 8 tractor-trailers. There is a data 

gap regarding the potential benefits of aerodynamic improvement technologies for use on heavy-duty 

vocational vehicles. ARB staff gathered information about aerodynamic controls for this vehicle 

category though literature reviews and stakeholder discussions prior to initiating the NREL study under 

ARB Agreement Number 11-600, NREL Contract Number FIA-12-1763. It is the intention of this 

current NREL study to complement previous work and explore the potential benefits of the most 

common aerodynamic improvement devices on box trucks using both coastdown and on-road steadystate techniques. The testing utilized two common vocational vehicle designs, a Class 4 and a Class 6 

box truck, which often operate at duty cycles with sufficient high-speed operation where aerodynamic 
2

devices could provide significant fuel savings. The overall intent of the NREL work is to estimate the 

expected benefits of several common types of vocational aerodynamic devices, as accurately as possible 

given limited test time and budget. 

Summary of NREL Test Program

Table 1 compares some features of the two heavy-duty vocational vehicles were that were tested 

and measured by NREL.

Table 1: Truck Descriptions

Vehicle Descriptor Class 6 Box Truck Class 4 Box Truck

Cab Style Conventional Low Cab Forward

GVWR 26,000 lbs 14,500 lbs

Nominal Box Length 26 feet 16 feet

Full Vehicle Length 37 feet 23 feet

Full Vehicle Height 12 ft 10 inches 11 feet

Average Widtha8 ft 4 inches 8 feet 1 inch

Minimum Ground Clearance 10 inches 5 inches

Note: 

a This calculation made by EPA not NREL

The NREL team evaluated the performance of three aerodynamic devices on the Class 6 truck 

and one device on the Class 4 truck, as shown in Table 2. Images of aerodynamic devices tested can be 

found in the Appendix to this document.

Table 2: Vocational Aerodynamic Technologies Assessed

VEHICLE BOX CHASSIS 

SKIRTS

FRONT (ROOF) 

FAIRING

REAR

FAIRING

WHEEL 

COVERS

Class 6 Box Truck X X X

Class 4 Box Truck X

Device Weight (lbs) 101 34 109 5

Coastdown testing was performed following the guidelines from SAE J1263, “Road Load 

Measurement and Dynamometer Simulation Using Coastdown Techniques” and SAE J2263, “Road 

Load Measurement Using Onboard Anemometry and Coastdown Techniques” with the additional 

calculation step of normalizing the results to STP from 40 CFR §1066.310-4. Table 3 presents 

preliminary coastdown results, which have been corrected for road grade, headwind/tailwind, air 

temperature, and air pressure. The NREL results are preliminary, whereas planned future work under the 

ARB agreement includes repeated coastdown tests, steady-state tests, and further analysis of the data 

and refinement of the processing code.
3

Table 3: Preliminary Coastdown Results

VEHICLE 

TYPE CONFIGURATION CD*A [m

2

]

a DELTA 

CD*A [m

2

]

b

Class 6 Box 

Truck

Reference Average 5.64 -

With Chassis Skirt 4.86 0.82

With Front Fairing 5.24 0.52

With Chassis Skirt & Front Fairing 5.16 0.60

With Wheel Covers 5.34 0.03

With Chassis Skirt, Front Fairing, and Wheel Covers 5.25 0.49c

Class 4 Box 

Truck

Reference 5.28 -

With Rear Fairing 5.01 0.27

Notes:

a Central values are presented for CDA and Delta CDA. See appendix for high/low estimates.

b Changes in CDA (deltas) are determined for each device using separate baseline test runs, not the average of the 

reference runs shown here. 

c Crosswind conditions on this test date put these results in question.

Possible Phase 2 Approach to Vocational Aerodynamics

The agencies are considering adopting provisions in the Phase 2 HD GHG program to enable

chassis manufacturers to obtain credit for installation of aerodynamic devices on vocational vehicles. 

One potential approach is to offer delta CDA values as optional inputs in the GEM simulation tool 

associated with certain aerodynamic devices. Manufacturers who install (or instruct another entity to 

install) an eligible device on an eligible vehicle would select the appropriate input and GEM would 

apply the pre-defined delta CDA to the default CDA that is already programmed in GEM for the 

applicable vehicle weight class.

For such an approach to be practical, the agencies believe this would require that the certifying

manufacturer have knowledge of and some degree of control over the size and shape of the vehicle in its 

final built form. To address cases where business relationships or other factors enable chassis 

manufacturers to do this, the agencies are proposing delegated assembly provisions in the regulations. 

See 40 CFR 1037.621. 

If the agencies were to adopt this approach based on the preliminary NREL results, it would 

likely be necessary to restrict eligibility of vocational vehicles that could be certified with an improved 

CDA in GEM to those meeting the characteristics described in Table 4 below. If additional data become 

available to the agencies, quantifying the effect of changes in vehicle frontal area and/or length on delta 

CDA for specific devices, the vehicle size eligibility could be broadened. To ensure that vehicles 

applying for this credit would be most likely to benefit from aerodynamic technology in the real world, 

the agencies may choose to restrict eligible vehicles to those that meet the segmentation criteria in 40 

CFR 1037.510(c) specifying certification using the Regional duty cycle in GEM.
4

Table 4: Characteristics of Vehicles Potentially Eligible to Gain GEM Credit for Aerodynamics

VEHICLE TYPE GVWR CHASSIS LENGTH FRONTAL AREA

Low Cab Forward

Box Truck

10,001 to 19,500 lb

(Class 3-5)

7 m (+- 0.3 m) 8.0 m

2

(+- 0.2 m

2

)

Conventional Cab 

Box Truck

16,001 lb to 33,000 lb

(Class 5-7)

11 m (+- 0.3 m) 9.3 m

2

(+- 0.2 m

2

)

The frontal areas in Table 4 are based on calculations using measurements of vehicle dimensions 

from NREL that are found in the appendix plus other dimensions transmitted to the ARB and EPA 

during this project. The formula specified in SAE J1263 (used with light-duty vehicles) where frontal 

area is estimated by multiplying the total vehicle height and the maximum vehicle width by 80 percent, 

was not used. If that protocol had been used, the resulting estimates of frontal area would have been 7.0 

m

2

for the low cab forward truck and 8.1 m2for the conventional cab truck versus 8.0 m2and 9.3 m2, 

respectively, from Table 4.

Based on the preliminary NREL results, the agencies are considering a narrow range of eligible 

aerodynamic devices: box chassis skirts and front (roof) fairings for larger trucks; and rear fairings

(tails) for smaller trucks. Depending on additional data that may become available to the agencies 

during the comment period, quantifying the effect of different devices on delta CDA for specific 

vehicles, the device eligibility could be broadened. Table 5 presents some ranges of possible delta CDA 

values (derived from Table 3), which could be in the range of pre-defined technology improvement 

values made available in GEM under certain circumstances.

Table 5: Possible Aerodynamic Technology Improvement Values (Delta CDA, m

2

)

BOX CHASSIS 

SKIRTS

FRONT 

FAIRING

FRONT FAIRING

AND SKIRTS

REAR 

FAIRING

Conventional Cab 

Box Truck (Class 5-7)

0.6 to 0.9 0.4 to 0.6 0.5 to 1.0 -

Low Cab Forward 

Box Truck (Class 3-5)

- - - 0.1 to 0.4

Certification 

Conditions

Regional duty cycle, Delegated assembly agreement

To illustrate the effect on vehicle fuel efficiency reflected in GEM of changes in a vocational 

vehicle’s CDA, the agencies have simulated some example effectiveness values for the following 

combinations of devices and vehicles: a LHD vocational vehicle with only a rear fairing and both a 

chassis skirt and a front fairing; and a MHD vocational vehicle with only a front fairing and both a 

chassis skirt and a front fairing. These cases are shown in Table 6. 
5

Table 6: Vehicle Cases Simulated in GEM

VEHICLE TECHNOLOGY WEIGHT IN LBS EXAMPLE DELTA CDA (m2)

Light heavy-duty vocational 

vehicle (Class 3-5)

Rear Fairing 109 0.2

Chassis Skirts & Front 

Fairing

135 1.0

Medium heavy-duty vocational 

vehicle (Class 6-7)

Front Fairing 34 0.4

Chassis Skirts & Front 

Fairing

135 1.0

Each of these cases was run in GEM twice: once ignoring the added weight of the device and a 

second time adding the weight of the device, as reported by NREL. This is done for illustrative 

purposes, to show the likely effects of added weight on the simulated vehicles in GEM. Physics would 

suggest that added mass may cause the overall effectiveness of an aerodynamic device to be diminished 

by varying amounts depending on the driving patterns of a vehicle.

The results in 

Table 7 represent technology effectiveness where the mass of the aerodynamic device has been 

disregarded. The results in Table 8 represent technology effectiveness where the mass of the 

aerodynamic device has been taken into account by allocating half to the static test weight and half to a 

diminished payload.

In the results presented below, some of the cases involve the same combination of technologies -

chassis skirt and front fairing - on both a LHD vehicle and a MHD vehicle. The differences in these 

results reflect the differences in the vehicle parameters in GEM, including a different engine, 

transmission, chassis weight and payload. In comparing these cases, it appears the LHD vehicle benefits 

more from the aerodynamic technology than the MHD vehicle does, though it also appears to be more 

sensitive to changes in weight.
6

Table 7: Example GEM Improvements

Vocational Aerodynamics Effectiveness 

Disregarding Weight Effects

MEDIUM HEAVY-DUTY LIGHT HEAVY-DUTY

Baseline Front Fairing Chassis Skirt & 

Front Fairing

Baseline Rear Fairing Chassis Skirt & 

Front Fairing

CDA 5.4 5 4.4 5.4 5.2 4.4

65mph CO2 Emission (g CO2/ton-mi) 211 201 186 401 391 353

55mph CO2 Emission (g CO2/ton-mi) 171 164 153 314 308 280

Transient CO2 Emission (g CO2/ton-mi) 244 243 240 367 365 358

Effectiveness over 65 mph 4.5% 11.8% 2.4% 12.0%

Effectiveness over 55 mph 4.1% 10.5% 2.2% 10.8%

Effectiveness over Transient 0.6% 1.8% 0.5% 2.4%

Regional Cycle Effectiveness 

 (50% Transient, 28% 55 mph, 22% 65 mph)

2.3% 5.8% 1.3% 6.7%

Multi-Purpose Cycle Effectiveness 

 (82% Transient, 15% 55 mph, 3% 65 mph)

1.2% 3.0% 0.8% 3.7%

Urban Cycle Effectiveness 

 (94% Transient, 6% 55 mph)

0.8% 2.1% 0.6% 2.7%
7

Table 8: Example GEM Improvements with Added Weight

Vocational Aerodynamics Effectiveness 

With Added Device Weight

MEDIUM HEAVY-DUTY LIGHT HEAVY-DUTY

Baseline Front Fairing Chassis Skirt & 

Front Fairing

Baseline Rear Fairing Chassis Skirt & 

Front Fairing

CDA 5.4 5 4.4 5.4 5.2 4.4

Static Test Weight (kg) 11,408 11,416 11,439 7,257 7,282 7,288 

Payload (tons) 5.60 5.59 5.57 2.85 2.82 2.82

65mph CO2 Emission (g CO2/ton-mi) 211 201 187 401 395 357

55mph CO2 Emission (g CO2/ton-mi) 171 164 154 314 311 284

Transient CO2 Emission (g CO2/ton-mi) 244 243 242 367 369 363

Effectiveness over 65 mph 4.5% 11.2% 1.4% 10.9%

Effectiveness over 55 mph 4.1% 9.9% 1.2% 9.7%

Effectiveness over Transient 0.6% 1.1% -0.6% 1.1%

Regional Cycle Effectiveness

 (50% Transient, 28% 55 mph, 22% 65 mph)

2.1% 5.1% 0.3% 5.4%

Multi-Purpose Cycle Effectiveness 

 (82% Transient, 15% 55 mph, 3% 65 mph)

1.0% 2.2% -0.3% 2.4%

Urban Cycle Effectiveness 

 (94% Transient, 6% 55 mph)

0.7% 1.4% -0.6% 1.4%
1

APPENDIX

Aerodynamic Drag Reduction Technologies for Heavy-Duty Vocational 

Vehicles – Preliminary Coastdown Results
2

January and February, 2015

Aerodynamic Drag Reduction Technologies for Heavy-Duty Vocational 

Vehicles – Preliminary Coastdown Results

The National Renewable Energy Laboratory (NREL) under ARB Agreement Number 11-600, NREL 

Contract Number FIA-11-1763 has performed a series of coastdown tests on heavy-duty vocational 

vehicles with and without aerodynamic improvement devices to assess their performance. These results 

are preliminary and future work under this agreement will include additional repeats and steady -state 

tests to help refine these results at a later date. The procedure used for coastdown testing followed the 

general guidelines outlined in SAE J1263 and SAE J2263 and uses calculation from CFR 1066.310 

where applicable.

Coastdown Track

The current coastdown track is located at the Front Range Airport east of Denver, CO. The east runway, 

which runs in a north-south direction, has an access road along the east side of it. A portion of that road, 

as seen by the red line in Figure 1, is used for coastdowns. The track runs in a north-south direction. The 

southern end of the track has an average grade of 0.4%.

Track Profile
3

Data Processing

Data is collected at 5Hz during the coastdown. An ISAAC data recorder monitors OBD information as 

well as logging velocity from a Garmin 18x-5Hz which is used in the data post processing. Since the 

track has a slight grade the north and south profiles differ.

0

1

2

3

4

5

6

7

8

Elevation Change [meters]

Latitude

North end of 

track

Avg. 0.4% 

grade

South

North
4

The following road load equation is used to describe the behavior of the vehicle:

 − 

∆h

∆

=  + 1

2

 



At each time step interval the total force on the vehicle can be calculated using the following equation:

 = 

 = 

 − 

∆

The effective mass (me) was calculated for the class 6 box truck by adding 56.7 kg to the measured 

vehicle mass for each tire making road contact. For the class 4 city van the ratio of rotating mass to 

measured vehicle mass was kept the same. After correcting for elevation change using the road grade 

survey each interval point in plotted and a least-squares regression is used to determine the coefficients.

In the polynomial fit the ‘B’ term is fixed at zero and ‘A’ and ‘C’ coefficients are assigned as follows

 = 

 =  = 1

2

 

Then ‘D’ term can be corrected for standard conditions as follows

 = 



293

98.21


5

The Vehicles
6
7

The Aerodynamic Devices

Device Vehicle Total Weight

Wheel Covers 26’ Box Truck 2.2 kg (4.8 lbs)

Front Fairing 26’ Box Truck 15.5 kg (34.1 lbs)

Side Skirts 26’ Box Truck 45.9 kg (101 lbs)

Rear Fairing 16’ LCF Truck 49.5 kg (109 lbs)

Preliminary Results

All error estimates shown are 95% confidence intervals.

Test Vehicle Aerodynamic Device(s) Am [lbf] Dadj [lbf/mph2

] μ CdA [m2]

Road Load @ 

55 mph [lbf]

Road Load @ 

45 mph [lbf]

Class 6 Box Truck Baseline (Wheel Covers) 130.2 ± 9.2 0.141 ± 0.007 0.0076 ± 0.0005 5.35 ± 0.27 556 ± 14 415 ± 10

Class 6 Box Truck Wheel Covers 130.8 ± 11 0.142 ± 0.006 0.0076 ± 0.0006 5.42 ± 0.21 562 ± 17 419 ± 13

Class 6 Box Truck Baseline (Skirts) 144.6 ± 17.3 0.158 ± 0.011 0.0085 ± 0.001 6 ± 0.43 622 ± 37 464 ± 27

Class 6 Box Truck Side Skirts 141.2 ± 15.2 0.144 ± 0.011 0.0082 ± 0.0009 5.47 ± 0.4 576 ± 43 432 ± 32

Class 6 Box Truck Baseline (Front Fairing) 134.7 ± 13.8 0.153 ± 0.007 0.0079 ± 0.0008 5.83 ± 0.27 599 ± 18 445 ± 13

Class 6 Box Truck Front Fairing 137.4 ± 8 0.14 ± 0.006 0.0081 ± 0.0005 5.32 ± 0.21 560 ± 16 420 ± 12

Class 6 Box Truck Front Fairing + Skirts 125.5 ± 10.2 0.136 ± 0.005 0.0073 ± 0.0006 5.18 ± 0.19 538 ± 13 401 ± 9

Class 6 Box Truck Baseline (All) 132.7 ± 15 0.15 ± 0.009 0.0078 ± 0.0009 5.72 ± 0.34 588 ± 20 437 ± 15

Class 6 Box Truck Front Fairing + Skirts + Covers 137.9 ± 7.4 0.138 ± 0.004 0.008 ± 0.0004 5.26 ± 0.16 557 ± 10 418 ± 7

Class 4 City Van Baseline (Rear Fairing) 126.9 ± 3.3 0.139 ± 0.003 0.0128 ± 0.0003 5.29 ± 0.12 548 ± 10 408 ± 7

Class 4 City Van Rear Fairing 124.8 ± 6.8 0.133 ± 0.005 0.0125 ± 0.0007 5.05 ± 0.2 526 ± 20 394 ± 15

Coefficients - Includes Correction for Road Grade and Adjustment to Standard Temperature and Pressure
8

Observed Change Without Wind Correction

Aerodynamic Device(s) μ CdA 

Road Load 

@ 55 mph

Road Load 

@ 45 mph

Wheel Covers -0.5% ± 1.2% -1.3% ± 1.3% -1.1% ± 1.1% -1% ± 1%

Side Skirts 3.4% ± 2.1% 8.8% ± 0.8% 7.3% ± 1.3% 6.8% ± 1.2%

Front Fairing -1.8% ± 1.5% 8.9% ± 0.7% 6.4% ± 1.5% 5.6% ± 1.3%

Front Fairing + Skirts 8.7% ± 2.2% 11.2% ± 0.8% 10.2% ± 0.9% 9.9% ± 0.8%

Front Fairing + Skirts + Covers -3.1% ± 0.9% 7.9% ± 0.8% 5.3% ± 0.6% 4.4% ± 0.5%

Rear Fairing 1.6% ± 0.7% 4.5% ± 0.5% 3.9% ± 0.5% 3.6% ± 0.5%

Observed Change - Without Wind Correction

Test Vehicle Aerodynamic Device(s) Am [lbf] Dadj [lbf/mph2

] μ CdA [m2]

Road Load @ 

55 mph [lbf]

Road Load @ 

45 mph [lbf]

Class 6 Box Truck Baseline (Wheel Covers) 129.7 ± 8.8 0.141 ± 0.009 0.0075 ± 0.0005 5.37 ± 0.34 556 ± 20 415 ± 15

Class 6 Box Truck Wheel Covers 128.9 ± 15.8 0.14 ± 0.008 0.0075 ± 0.0009 5.34 ± 0.29 553 ± 14 413 ± 11

Class 6 Box Truck Baseline (Skirts) 141 ± 16.1 0.149 ± 0.012 0.0082 ± 0.0009 5.68 ± 0.47 593 ± 28 444 ± 21

Class 6 Box Truck Side Skirts 146.1 ± 22.3 0.128 ± 0.014 0.0085 ± 0.0013 4.86 ± 0.54 533 ± 35 405 ± 26

Class 6 Box Truck Baseline (Front Fairing) 136.5 ± 12.2 0.151 ± 0.007 0.008 ± 0.0007 5.76 ± 0.29 595 ± 15 443 ± 11

Class 6 Box Truck Front Fairing 142.4 ± 12.1 0.138 ± 0.006 0.0084 ± 0.0007 5.24 ± 0.24 559 ± 19 421 ± 14

Class 6 Box Truck Front Fairing + Skirts 122.8 ± 11 0.136 ± 0.007 0.0071 ± 0.0006 5.16 ± 0.26 533 ± 15 397 ± 12

Class 6 Box Truck Baseline (All) 131.9 ± 13.9 0.151 ± 0.01 0.0077 ± 0.0008 5.74 ± 0.37 588 ± 21 437 ± 16

Class 6 Box Truck Front Fairing + Skirts + Covers 139.4 ± 8.9 0.138 ± 0.006 0.0081 ± 0.0005 5.25 ± 0.24 557 ± 14 419 ± 10

Class 4 City Van Baseline (Rear Fairing) 126 ± 4 0.139 ± 0.005 0.0127 ± 0.0004 5.28 ± 0.2 546 ± 16 407 ± 12

Class 4 City Van Rear Fairing 129.5 ± 4.6 0.132 ± 0.008 0.013 ± 0.0005 5.01 ± 0.32 528 ± 25 396 ± 19

Coefficients - Includes Correction for Road Grade, Headwind/Tailwind and Adjustment to Standard Temperature

and Pressure Conditions
9

Observed Change With Wind Correction

Aerodynamic Device(s) μ CdA 

Road Load 

@ 55 mph

Road Load 

@ 45 mph

Wheel Covers 0.6% ± 1.4% 0.5% ± 1.4% 0.6% ± 0.4% 0.6% ± 0.5%

Side Skirts -2.6% ± 1% 14.5% ± 0.8% 10.2% ± 1.2% 8.8% ± 1.1%

Front Fairing -4.1% ± 1.6% 9.1% ± 0.8% 6% ± 0.7% 5% ± 0.6%

Front Fairing + Skirts 11.8% ± 2.1% 10.5% ± 0.8% 10.4% ± 0.8% 10.3% ± 0.7%

Front Fairing + Skirts + Covers -4.9% ± 1% 8.5% ± 0.8% 5.3% ± 0.5% 4.2% ± 0.4%

Rear Fairing -2.8% ± 0.7% 5.2% ± 0.5% 3.3% ± 0.3% 2.7% ± 0.3%

Observed Change - With Wind Correction

Vehicle Aerodynamic Device(s)

Wind Speed 

[mph] Wind N Wind E Air Temp [C] Atm P [Bar] Dew Pt [C]

Class 6 Box Truck Baseline (Wheel Covers) 3.4 0.6 3.2 12.0 0.828 -9.0

Class 6 Box Truck Wheel Covers 3.5 1.9 1.1 13.3 0.828 -10.2

Class 6 Box Truck Baseline (Skirts) 8.9 4.4 5.0 11.5 0.837 -6.7

Class 6 Box Truck Side Skirts 8.8 4.5 1.2 12.6 0.836 -7.3

Class 6 Box Truck Baseline (Front Fairing) 3.8 0.6 -0.5 14.4 0.832 -10.3

Class 6 Box Truck Front Fairing 3.3 -1.0 -2.7 15.2 0.832 -9.6

Class 6 Box Truck Front Fairing + Skirts 3.4 1.5 -2.5 17.8 0.831 -9.2

Class 6 Box Truck Baseline (All) 4.7 0.2 2.9 11.6 0.834 -12.2

Class 6 Box Truck Front Fairing + Skirts + Covers 9.2 0.3 9.1 14.6 0.833 -10.9

Class 4 City Van Baseline (Rear Fairing) 14.1 0.0 13.9 6.1 0.834 -6.5

Class 4 City Van Rear Fairing 13.7 -3.4 13.1 6.7 0.833 -6.0

Average Weather Conditions
10

Discussion

These results are preliminary and planned future work includes additional repeats and steady -state tests. 

Also, data analysis efforts and refinement of the processing code are ongoing and may also affect future 

results. Under the test condition of “All* (see note)” please note that changing wind conditions shown in 

the weather conditions table for this test, predominately the eastern crosswind which increased 

dramatically between the baseline (all), and the test condition. This may have significantly affected this 

data point and the condition will be repeated once weather permits.