Factual Information 131 Aircraft Accident Report
1.16.5.2 Laboratory Testing of Jet A Fuels—California Institute of
Technology
A review of Jet A combustion data available when the TWA flight 800 accident
occurred revealed that insufficient research data were available to adequately address the
specific issues germane to the characteristics of a CWT explosion.
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Therefore, the Safety
Board contracted with explosion dynamics experts at the CIT Graduate Aerodynamics
Laboratory to conduct a comprehensive experimental and analytical investigation of the
combustion behavior of Jet A fuel. This included flammability research to identify
conditions under which Jet A fuel/air mixtures are flammable and combustion research to
determine the characteristics (for example, explosion peak pressures and flame speeds) of
Jet A fuel combustion. The issues of ignition energy, temperature, altitude (pressure),
mass loading, weathering, and fuel chemistry
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were investigated because of their
criticality to the explosion of the CWT.
The flammability research focused on defining the conditions at which Jet A fuel
vapor was found to be flammable.
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A precision test fixture was developed to generate
fuel vapors over a large range of temperature and pressure conditions, and an electronic
spark system was developed to ignite the vapors while accurately measuring the ignition
energy supplied. Hundreds of tests were performed
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to determine the flammability limits
of the fuel vapor, as a function of ignition energy, fuel temperature, pressure (to simulate
altitude), fuel mass loading, and fuel weathering. The test conditions were selected to
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Electrical conductivity for fuel is the ability of the fuel to dissipate a static charge, and the unit of
measure is picosiemens per meter. For additional information regarding the results of fuel tests conducted
during this investigation, see Powerplants Group Chairman’s Factual Report, dated February 25, 1997. This
fuel sample was also analyzed for chemical composition. For additional information, see the University of
Nevada report, “Sampling and Analysis of Vapors from the Center Tank of a Test Boeing 747-100 Aircraft,”
dated November 1997.
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According to the experts at CIT, the Jet A flammability data at the time of the accident included
limited data on flammability properties found in the industry standard references (Kuchta, J. M. et. al. 1985.
Aircraft Mishap Fire Pattern Investigations
. Final Report APWAL-TR-85-2057. Aero Propulsion
Laboratory.; and Zabetakis, M. G. 1965.
Flammability Characteristics of Combustible Gases and Vapors.
Bulletin 627. Bureau of Mines.), much of which was without direct attribution. However, the CIT experts
indicated that much of the Jet A flammability data that existed at the time of the accident appeared to have
been derived from the following three technical reports: Nestor; Ott, E. 1970.
Effects of Fuel Slosh and
Vibration on the Flammability Hazards of Hydrocarbon Turbine Fuels within Aircraft Fuel Tanks
. Technical
Report AFAPL-TR-70-65. Fire Protection Branch of the Fuels and Lubrication Division. Wright Patterson
Air Force Base, Ohio; and Kosvic et. al. 1971.
Analysis of Aircraft Fuel Tank Fire and Explosion Hazards
.
Technical Report AFAPL-TR-71
-07
. Air Force Aero Propulsion Laboratory, Wright Patterson Air Force
Base, Ohio.
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Fuel chemistry variations commonly result from different formulations of Jet A fuel and can be
affected by variations in fuel supply, fuel supplier, fuel handling, and/or mass loading.
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For additional information regarding these tests, see CIT/Graduate Aeronautical Laboratory. 1999.
Spark Ignition Energy Measurements in Jet A
. Explosion Dynamics Laboratory Report FM97-9. Also, see
CIT/Graduate Aeronautical Laboratory. 2000.
Spark Ignition Measurements in Jet A: Part II.
Explosion
Dynamics Laboratory Report FM99-7.
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Initially, these tests were performed using single component hydrocarbon fuels (methane and
propane) to validate the experimental procedures and test results when compared to previously published
research on these fuels. However, subsequent tests were performed using Jet A fuel/fuel vapors.