There is air in the tanks. There’s plenty of evidence for that you can find by doing an Internet search. Here’s an example:
Later this year, the FAA plans to order reductions in the flammability of gases that float in the void above Jet A fuel in airliner tanks. Airlines and manufacturers will be able to meet the requirement by using systems based on a prototype developed by the FAA—an onboard inert-gas generation system (OBIGGS), which replaces much of the air in a fuel tank with nitrogen, a gas that does not support combustion. The technology “will virtually eliminate the possibility of future fuel tank explosions,” FAA Administrator Marion Blakey said in February when announcing the agency’s plans to recommend that 3,800 Boeing and Airbus airliners be fitted with inerting technology.
http://www.airspacemag.com/how-things-work/safer-fuel-tanks-5883916/?no-ist
Go to page 131 of the NTSB report and you’ll find the extensive testing and research done on the flammability of the fuel air mixture in the center tank of TWA 800 at the accident altitude.
http://www.ntsb.gov/investigations/AccidentReports/Reports/AAR0003.pdf
I am not disputing that there is air in the tanks. I am merely pointing out that at 13,000 feet, it is unlikely to be sufficiently dense to initiate combustion without being compressed to a higher density... and that's if you have a strong enough ignition source, which they didn't.
Go to page 131 of the NTSB report and you’ll find the extensive testing and research done on the flammability of the fuel air mixture in the center tank of TWA 800 at the accident altitude.
I am pretty sure I am going to regret wading through this section of document.
According to that report:
Published research involving pure hydrocarbon fuels260 estimated the LFL of these fuels at sea level to be a fuel/air mass ratio of 0.036 to 0.041. Published research involving Jet A fuels261 estimated the LFL for Jet A to be a fuel/air mass ratio of 0.032 to 0.035, for pressure between 0.4 and 1.0 atmospheres. Although the LFL was not explicitly tested for during CIT’s research, the lowest fuel/air mass ratio ignited was calculated at 0.038 at 13,800 feet msl, using 80 J spark energy.
80 joule spark energy? 80 amps for 1 second? That's trying pretty hard to light something on fire, don't you think? That would light paper on fire, let alone fuel vapor.
Also the report requires the fuel to be at a temperature of 96.4° F. Max temperature for that day was 86 degrees, presumably at the hottest part of the day.
Also the flight took place at 8:31 p.m., which was well after the peak heat of the day.
Looks like they are trying real hard to salvage that theory.
Yes. The most important point, however, is that an intrinsically safe sensor cannot supply enough heat to ignite that fuel even if the fuel-to-air mixture was ripe for an explosion. The sensor is a low voltage, low current device that would deliver no spark even if shorted out. The intrinsically safe barrier between the sensor and the rest of the plane would prevent sufficient heat from being generated in the sensor even if the sensor's signal wires were connected to the 480 volt batteries of a tow tug.