When the National Safety Transportation Board (NTSB) conducted experiments in June to duplicate the last few hours of TWA Flight 800, equipment from the Desert Research Institute was on board to collect samples of fuel vapor in the plane's center fuel tank. The NTSB was trying to determine why the Paris-bound plane broke apart in flight and crashed in darkness off the Atlantic coast of Long Island on July 17, 1996, with the loss of all 230 people aboard.
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| Dr. John Sagebiel in DRI's Organic Chemistry Laboratory with the nine canisters that collected fuel tank vapor on the simulations of TWA Flight 800. Each test flight required three of the smaller canisters, compared to the larger versions behind Sagebiel which are typically used in urban air quality studies. |
NTSB investigators speculate that heat from the craft's air conditioners, which are located beneath the center tank and were running continuously during the wait on the ground, raised the temperature of the vapor in the tank. An increase in vapor temperature makes it more susceptible to ignition from the heat of an electrical short or a spark. The vapor-filled canisters from the test flight were immediately flown to Dr. Sagebiel at DRI's Organic Chemistry Laboratory in Reno. Sagebiel, an environmental chemist in DRI's Energy and Environmental Engineering Center, said the explosive force of vapor can increase greatly at higher concentrations, so his analysis looked at how much the fuel vapor became concentrated during the flight test.
DRI normally uses these procedures to analyze air pollutants at much lower concentrations than the fuel vapor, Sagebiel said. ?What was important here was collecting a precise, representative sample of the vapor in the tank. It's as critical as obtaining an exact sample of a city's air quality condition, so our capabilities were very applicable for this. DRI's involvement in the tests stemmed from a referral by a scientist at the University of Nevada, Reno. James Woodrow, a UNR environmental chemist, was contracted by NTSB to conduct laboratory tests of fuel samples obtained from the Athens airport where TWA 800 had topped off its tanks before flying to New York.
Woodrow conducted a laboratory-scale version of the flight simulations, employing a process known as headspace sampling. The fuel was heated in 22 milliliter glass vials at 30, 40, and 50 degrees centigrade (86, 104, and 122 degrees Fahrenheit), with varying amounts of liquid in the vials. This simulates varying levels of fuel in the tank from very little up to about half full,? Woodrow said. ?Using gas chromatography, the mix of the volatile hydrocarbons that are produced in the vapors can be determined and should indicate the explosive potential of the vapor that was in the tank under the conditions that occurred shortly before the accident.
Dr. James Seiber, director of UNR's Center for Environmental Sciences and Engineering, and Woodrow, laboratory manager at the Center, had previously studied the vapor composition of various petroleum products while employed at the University of California-Davis.
Once the DRI and UNR analyses were completed, the results were sent to NTSB, which then forwarded them to scientists at the California Institute of Technology for further tests related to the center fuel tank. NTSB hopes to be able to issue a final report on the accident by early December.
