Review of the data obtained from the emulation flight test revealed that the CWT vapor samples had fuel/air mass ratios(247) of 0.034, 0.046, and 0.054 on the ground during taxi and as the airplane climbed through about 10,000 and 14,000 feet msl (see table 7). According to scientific literature(248) and tests conducted by experts at the California Institute of Technology (CIT), the lower flammability limit (LFL) of Jet A fuel is at a fuel/air mass ratio of 0.032 to 0.038.(249)
(245) For additional information regarding the vapor sampling mechanism and the handling and testing of the vapor samples collected, see the Flight Test Group Chairmanís Factual Report, dated November 19, 1997. Also, see the DRI report, ìSampling and Analysis of Vapors from the Center Wing Tank of a Test Boeing 747-100 Aircraft,î dated November 1997.
(246) Two sampling bottles were used for each vapor sample acquisition. One bottle was used to purge the sampling line and manifold, and the other, subsequently, was used to collect a valid vapor sample.
(247) The fuel/air mass ratio is a measure of the mass of fuel in a mixture divided by the mass of the air in that mixture. In the context of this flight test sample, it is a measure of the mass of the fuel in the ullage divided by the mass of the air in the ullage.
(248) Nestor, L. 1967. Investigation of Turbine Fuel Flammability within aircraft Fuel Tanks. Final Report DS-67-7. Naval Air Propulsion Test Center, Naval Base, Philadelphia, Pennsylvania. Also, Shepherd, J. E.; Nuyt, C. D.; and Lee, J. J. 2000. Flashpoint and Chemical Composition of Aviation Kerosene (Jet A). Graduate Aeronautical Laboratories, CIT. Explosion Dynamics Report FM99-4.
(249) From May 29 to 31, 1998, Boeing performed additional ground tests, with technical support from the Safety Board, to investigate the 747-100 CWT thermal and vapor environment. These tests were conducted at Pinal Air Park in Marana, Arizona, using a 747-100 series airplane leased from Evergreen Airlines and were similar in scope to the JFK flight tests conducted by the Safety Board. Testing was performed in a hot ambient environment (outside air temperatures above 95° F), with all three of the airplaneís air conditioning packs operating. The tests were conducted in the following conditions: (1) a nearly empty fuel load in the CWT (50 gallons, similar to TWA 800), with uninsulated air conditioning packs; (2) 50 gallons of fuel in the CWT, with thermally insulated air conditioning packs; and (3) 12,000 pounds of fuel in the CWT, with uninsulated air conditioning packs. Temperature and vapor measurements of the CWT indicated that a flammable condition existed during ground operations during each of the three tests. For additional information, see Summary Data Report: B-747-100 Center Wing Tank Ground Testing at Marana, Arizona, dated January 20, 2000.