NTSB experts have expended considerable time and effort determining the flammability of the fuel/air mixture in the Center Tank of the F800 747 aircraft.  Regardless of the reasons for the exact mixture ratio, be it elevated tank temperature, reduced pressure in the tank due to altitude, or agitation of the fuel or a combination of these we know the tank exploded and the object of our investigation should be to determine the ignition source for that explosion.

At the Public Hearing in Baltimore, Chairman Hall outlined the following as potential ignition sources:           

1. The Scavenge Pump:   Under normal circumstances the scavenge pump would not have been operating at the time of the accident.

2. Static Electricity generated in a crossfeed tube by fuel flow through the tube at a time when there would have been no flow through the tube.

3. Higher than normal voltage in the Fuel Quantity Indication System caused by short circuits with adjacent wires, which were never found.  Had they existed we could have expected  a malfunctioning fuel quantity system which was not mentioned by the operating crew.

4. Faulty Electrical Conduits:  None were identified during the investigation.

5. Bomb Damage:  The FBI reported they did not find evidence of such an occurrence.

6. Missile Fragment Damage was possibly found and not identified as such.

This presentation is intended to concentrate on Item 6  (Missile Fragment Damage)  as a
Possible ignition source for an explosion in the Center Wing Tank.

Was there evidence of missile firings in the vicinity of F800 the night of the accident?

The statements of over 100 eyewitnesses would indicate there were flarelike objects in the sky the night of the accident.

Is it possible for a shoulder launched missile to reach F800s altitude?  Richard Bott of 
Naval Weapons Facility at China Lake testified at the Baltimore hearing on this subject as follows:  “There is no question a missile could have reached TWA 800, the investigation was quickly narrowed to an examination for shoulder launched missiles.”
Bott also testified that in situations where a missile self destructs because it has missed its target you could expect as few as 1 or 2 fragment impacts on a 1000 square foot surface 100 feet from detonation.  His testimony also included a general description of damage expected in four zones around a missile impact.  It is interesting to note that Mr. Bott specified that distances generally beyond 20 feet from a detonation one could expect to find both high velocity, (4000’/sec,) and low velocity impacts.  With that in mind I Would call attention to what is apparently a low velocity puncture approximately 1” x 1” in the top wing skin at Right Wing Station 1542. 

The edges of this puncture are curled into the fuel vent surge tank and there is a yellowish orange material on the fracture surfaces.  

Would the energy required to punch a 1” x 1” hole in the top surface of the surge tank be sufficient to ignite a flammable mixture in the Surge Tank?  Based on information elicited from Dr. Merrit Birky at the NTSB Hearing it would be more than enough.

Would there have been a flammable mixture present in the Vent Surge Tank at the time of the Center Fuel Tank Explosion?  With the aircraft climbing, most of the content of the surge tank would have been vapor expelled from the large, nearly empty Center Wing Tank.  Therefore, according to the NTSB, it would have been explosive.

Throughout Mr. Bott’s testimony and the testimony of Mr. Wildie of the NTSB, they both stressed there were no entrance holes that allowed penetration through surrounding structure and in to the center tank and thus no source of ignition for the center tank explosion.  Similarly the FBI held that they found no sign of missile impact that could have caused the center tank to explode.  Both the FBI and the NTSB knew of the penetration at the right wing surge tank and they should have known the surge tank and the center tank vent would have contained vapors that, according to their own experiments, were flammable.  Evidently the reluctance to believe eyewitnesses may have seen a missile caused the investigative group to discount the possibility that the problem with center tank may have originated with the puncture in the surge tank at the right wing tip.  The puncture represents enough expended energy to ignite vapors in the surge tank which would then burn through the vent passages to the center wing tank igniting vapor in that nearly empty tank causing it to explode.  This sequence of events is based on evidence found in the wreckage and testimony of the various eyewitnesses and experts at the Baltimore Hearings.  It does not rely on some fictitious electrical spark that was caused by some imaginary electrical short circuit that was never found.

Any discussion of flame in the fuel tank vent system requires consideration of the Surge Tank Protection System and why it did not activate to protect the vents.  The Surge Tank Protection was designed to stop fires from entering the surge tank from outside by sensing a flash and releasing an extinguishing agent into the vent tank.  It would not be expected to activate by the circumstances described heretofore where the fire originated in the Surge Tank.

The NTSB description of the soot shading in the center tank vents would indicate an outward flow from the CWT to the Surge Tank.  Although I have described an initial burn into the center tank, it is to be expected that when the CWT exploded the predominate soot flow would be outward.  Additionally the higher temperature of the burn into the CWT may not have allowed soot to form.  The attached photograph of the damaged vent stringers shows the existing soot formations where the stringers have pulled loose from the underside of the wing top skin.  The photo is being attached to help the reader understand the physical location of the vents and is not being offered  for proof of the soot formations which are amply covered by the NTSB physical description of the vents.  HTM 

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