Erroneous Claims About The TWA Flight 800 Disaster

Caltech Explosion Dynamics Labratory ^ | Caltech Explosion Dynamics Labratory

[Asmodeus]

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Background Facts Glossary Documents 1/4-Scale Experiments Misconceptions

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Misconceptions

Unfortunately, misinformation about aviation kerosene combustion and misrepresentations about the official investigation of TWA 800 and the investigators have been published in print and on the worldwide web. The most common of these erroneous claims are discussed below:

You can put a match out in Jet A at room temperature so it can't possibly explode inside an aircraft fuel tank.

False. You can do this with many fuels that have sufficiently high flash or fire points. At room temperature, a combustible liquid fuel has enough heat capacity to absorb all the energy and extinguish a small match flame without raising the fuel surface temperature above the fire or flash point. A flame cannot be sustained over a liquid fuel until the surface temperature exceeds the fire point. A flash will not result unless the fuel temperature and vapor space are above the flash point. [Kuchta and Clodfelter] This does not apply to the case of TWA 800 because a) the explosion occurred in the fuel vapor-air mixture and did not require a fire on the fuel surface, b) the fuel and air inside the tank were hotter than the flash point, and c) the effective flash point was lowered due to the lower outside air pressure at the altitude of the explosion. The Jet A involved in the Center Wing Tank (CWT) explosion had a flash point temperature of about 115 F and the decreased air pressure at the explosion altitude of 13.8 kft lowered the effective flash point to about 100 F. [Exhibit20S] The temperatures inside the tank were between 100 and 130 F, and at some points, as high at 140 F. [Exhibit 23F]

The CWT of TWA Flight 800 was completely empty of fuel.

False. It is impossible to completely empty the center wing using the fuel system due to the location of the scavenge pump, the nature of the tank bottom surface, the division of the tank into bays, and the arrangement of the fuel probes that supply the fuel quantity instrumentation system. At least 50 to 100 gallons of fuel will remain even when the fuel quantity system indicates no fuel is remaining. [NTSB Final report]

The CWT of TWA Flight 800 did not contain enough air to support combustion.

False. This is apparently derived from the notion that fuel tank ullages in automobiles are generally too rich to support combustion. Jet A is a much less volatile fuel than gasoline and the situation is very different in an aircraft fuel tank than an automobile. The fuel tanks in an airplane are vented directly to the outside atmosphere and each time the plane descends from cruising altitude, a fresh supply of air is brought into the tank ullage by the vent system. The amount of fuel added to this air by evaporation is determined by the vapor pressure of the fuel, which has a maximum level of about 1 to 1.5% of atmosphere pressure for a tank containing 50-100 gallons of Jet A heated up to 60C - a situation comparable to TWA 800. [Exhibit 20D] The rich flammability limit for Jet A is probably above 6% by volume, far higher than any possible conceivable fuel concentration that would have existed in the TWA 800 situation. In contrast, the fuel vapor concentration in the ullage of a gasoline tank can be as high as 40% on a warm day.

The fuel in the CWT of TWA Flight 800 was cold.

False. Fuel and fuel tank temperatures were measured in flight tests with a Boeing 747. The temperatures at the time of the explosion ranged up to 60 C in the fuel layer at the bottom of the tank. [Exhibit 23F]

The vents in the CWT would prevent the pressure from building up during an explosion inside the tank.

False. The effects of venting were studied in the ¼-scale testing program and shown to be insignificant. The venting system area is too small to relieve the pressure from an explosion, even one that takes more than several seconds to pressurize the tank. [Exhibit 20E, 20O]

The NTSB investigators were unable to make Jet A explode in any tests.

False. Several hundred combustion experiments with Jet A were conducted to determine the peak overpressure, flame speed, and ignition energy. The conditions of these experiments bracketed the range of conditions observed in the flight tests. [Exhibits 20D, L, P, T]

The NTSB investigators had to use an ultra-sensitive explosive mixture of propane and hydrogen in ¼-scale testing because they were unable to get Jet A to explode.

False. As discussed above, explosions were obtained in numerous experiments with Jet A in the laboratory and in the ¼-scale tests. Several hundred experiments with Jet A were carried out in laboratory tests [Exhibits 20T, L]. The first series of experiments in the ¼-scale facility used a hydrogen-propane mixture to simulate Jet A. The purpose of using this mixture was to simulate flame propagation in a tank that was at a different temperature and pressure than the explosion altitude. The way in which this was accomplished and the choice of the simulant mixture are documented in Exhibits 20E and O. Subsequent experiments in this facility used Jet A at the temperatures and pressures corresponding to the conditions in TWA 800 at the explosion altitude. A movie from a Jet A experiment was shown at the August 22, 2000 board meeting illustrating the explosive combustion of Jet A vapors in the CWT model. This experiment demonstrates that sufficient pressure was created to reach the failure pressure on SWB3 despite the presence of venting and the failure of the model SWB3 and FS panels. [Exhibits 20O, P]

The NTSB investigators had to use excessively large spark energy in their ¼-scale testing.

False. A spark was never used to ignite the ¼-scale tests and ignition energy studies were not a part of the ¼-scale testing program. Extensive results are available on ignition energy in separate laboratory tests [Exhibits 20T, L]. The ignition system used in the ¼-scale was actually a hot filament ignition system and no sparks were created. [Exhibit 20O]

The NTSB investigators had to use a torch in order to start combustion in Jet A laboratory experiments.

False. Jet A vapor-air mixtures were ignited by many different ignition sources in the Caltech experiments. Experiments were conducted with spark ignition sources [Exhibits 20T and L] with energies ranging between 1 mJ and 100 J and the ¼-scale experiments simply used a hot filament [Exhibit 20O]. The preliminary experiments discussed in Exhibit 20D used a flame jet from a ½-inch diameter nozzle, comparable to some of the smaller openings in the spanwise beams and spars within the tank. Other experiments with pools of liquid creating vapor-air mixtures in the entire ullage with spark ignition in both the laboratory testing [Exhibit 20L and T] and hot filaments in the ¼-scale experiments [Exhibit 20O, P] demonstrate that the explosion of Jet A vapor mixtures in an ullage over a thin layer of fuel is associated with a propagating flame (deflagration) in the vapor-air mixture rather than a pool fire on the liquid layer. The combustion time is sufficiently short so that the combustion is completed before appreciable venting occurs. [see ¼-scale experiment number 67 - Exhibit 20P]

__________[snip]__________

Complete Report Here

[bmwcyle]

The Peoples Republic of California issues a report.

[the_doc]

Good article. (But it doesn't address the really serious complaints which some of us have about the overall investigation or its conclusions.)

[BlackbirdSST]

Well, there was a theory put forth immediately following the "accident", then years of effort finally pull together enough "test" results to prove the theory. How about that! Still a non-believer...Blackbird.

[FReepaholic]

>...You can put a match out in Jet A at room temperature so it can't possibly explode inside an aircraft fuel tank. False...<<

How 'bout a missile?? Will THAT ingnite the F/A mixture???

[Eastbound]

I liked the CIA video better.

[John O]

That's odd. The article doesn't explain anything about the missiles that were seen by multiple witnesses.

(Don't bother responding A, We've discussed this enough to know that you won't change your mind no matter how well the facts support a shootdown.)

God Save America (Please)

[jlogajan]

you won't change your mind no matter how well the facts support a shootdown

Ha ha ha ha ha ha ha ha ha ha!

[Asmodeus]

"The article doesn't explain anything about the missiles that were seen by multiple witnesses."

The "Missile Witnesses" Myth

[eno_]

It's pretty good until you get to here:

This experiment demonstrates that sufficient pressure was created to reach the failure pressure on SWB3 despite the presence of venting and the failure of the model SWB3 and FS panels...

...A spark was never used to ignite the ¼-scale tests and ignition energy studies were not a part of the ¼-scale testing program. Extensive results are available on ignition energy in separate laboratory tests [Exhibits 20T, L]. The ignition system used in the ¼-scale was actually a hot filament ignition system and no sparks were created.

The problem is that tests on the 1/4 scale model produced, at best, a slowly expanding flame-front (they mention taking several seconds to propagate throug the tank) that, in theory, could have raised pressure to the point you might get structural failure. This is not an "explosion," as normally understood.

Nor was it was ever shown that such a failure would break the nose off the plane - as opposed to, say, blowing out a panel in the tank. They never actually made the 1/4 size model to model structural strength, much less failure modes - just the dimensions. They never got the model to fail structurally. So they are left with saying that they produced enough pressure to, theoretically, make a real 747 fail.

It's not like there is a dire shortage of 747 airframes in which full-scale testing could have been done.

The article is also tendentious about how hard it is to accidentally get an explosive fuel-air mixture. The odds of this happening in the real world could, of course, be estimated by figuring out the full range of pressure and temperature combinations and seeing which are likeliest to occur. Tellingly, they cite data indicating the fuel in a real 747 could have been warm (60C) but no data on whether that would have, in fact, in a real 747, caused an explosive mixture. They were measuring the fuel temperature - odd that they would not measure the fuel in the air in the tank. Perhaps beacuse the odds are astronomically low in the real world, with realistic scenarios.

[templar]

Well ... I wonder if I now need to worry about my diesel rabbit exploding.

[eno_]

I like Asmodeuses favorite cite of a CIA satellite showing that the large explosion occurred at about 5000 feet.

This sat imagry was never released and probably never existed. These kinds of wild-ass assertions based on secret information put Asmodeus in the same category as the tinfoilers that theorize that it was an EMP weapon or meteorite. It is like seeing the results of a shooting and theorizing that Martians came down and blasted the victim with a death ray - despite all the people who saw the victim get shot.

Doubly ironic since Asmodeus says all the witnesses did not see what they saw, while Asmodeus sees this CIA sat image that nobody else has seen.

[eno_]

Yes, you do. Be very worried.

[Cold Heat]

Stuff it! this entire exercise is a waste of time.

What do I base this on?

The answer is simple. There were enough inconsistencies and even fruedian slips by the people in charge of this investigation to render the fuel tank story as suspect.

This is where it will remain. Just like the JFK investigation.

Whatever!

[Deguello]

"The "Missile Witnesses" Myth"

That is a cocky comeback to the question. What about the full page ad taken out in the Washington Times by the witnesses what want to be heard but are denied?

See the ad here:http://twa800.com/images/times-8-15-00.gif or at your local library in case that you think that the ad is a fabrication.

[Asmodeus]

You've just labeled Ian Goddard, the first king of the hill of the "shootdown" conspiracy theorists, a "tinfoiler".

Ian Goddard's EMP Theory

[Young Werther]

Yeah! Put a firecracker in mah favorite beer can and when it goes off the can will shrink inward! Just like the CWT tank in TWA 800!

This same aircraft survived a lightning strike which transited the CWT but, somehow, a spurious spark ingited the CWT residual fuel. Right!!!

[RayChuang88]

I have to start rolling my eyes skyward when people have to start digging out those ridiculous theories about the loss of TW 800.

Let's consider the following:

1. The plane exploded at 13,800 feet off the ground. That is above the flight envelope of the Stinger and Russian-made MANPAD's in service today.

2. There is NO evidence of an impact or blast fragmentation pattern on any of the four JT9D turbofans. This is especially important since MANPAD's are IR-seeking missiles, and a MANPAD would far more likely hit the engines, not the center of the plane.

3. There is NO evidence of a blast fragmentation pattern from the warhead of a Standard SM-2 missile. This eliminates the theory that a US Navy destroyer or frigate accidentally fired an SM-2 missile and it hit the plane.

The fuel-tank explosion is probably the most plausible theory, given that fuel vapor can have extremely explosive properties. Has anyone seen what a fuel-air explosive (FAE) bomb can do when a cloud of flammable fuel or powdered aluminum is spread over a wide area and ignited?

[Asmodeus]

It's hilarious that a "shootdown" tinfoiler like you would say that Ian Goddard, another "shootdown" guy, is a tinfoiler because he came up with his EMP "shootdown" Theory and animated graphic due to the lack of physical evidence of the traditional military missile "shootdown" you've been alleging.

[the_doc]

This is not an "explosion," as normally understood.

Good point. A deflagration is not the same as a detonation, and the pressure effects of these are different. (I was a professional engineer before I became a doctor, but I read the article too quickly to pick up on what you are now showing me.)

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I also appreciate what you are saying about the structural strength questions in scale-model testing. They really did need to do full-scale tests, I think. (Interestingly, explosion lab guys should realize this--right?--since structural issues are a big part of what they usually address.)

There was enough at stake in the TWA 800 investigation to warrant full-scale testing.

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I am also surprised by the speculation that the fuel may have been 60 degrees C. That's hot.