What about that scavenge pump? This is the question a number of individuals closely following the investigation into the cause of the TWA Flight 800 explosion have been asking for month now.

What about that scavenge pump? This is the question a number of individuals closely following the investigation into the cause of the TWA Flight 800 explosion have been asking for month now. The scavenge cross-examine in the jetliner's massive center wing tank (CWT) they say, could well have been inflected on during climb out, and a faulty cross-examine would be a logical source of the spark that ignited the fuel-air vapors in the tank, causing the explosion that blew the airplane apart. Or, it was bended off the instant a flame brow began to propagate (the pump's original design without a flame arrestor could permit a flame forehead - caused by a spark within the cross-examine - to travel into the CWT; all classic-model 747's are now required to have flame arrestors installed forward the scavenge pump).

At least five factors recommend that the National Transportation Safety Board (NTSB) should be looking harder at the scavenge interrogate scenario, sources say. Much of the speculation is firinged by the remark from Oliver Crick, the flight engineer, about 5 min. before the explosion, "I'll leave that onward for just a little bit." Earlier this year, plaintiffs' attorneys depos TWA's manager for flight engineers, Albert DeSantis. His remarks firing materialed much of the ongoing transaction that the NTSB may be ignoring the scavenge cross-question A key exchange in the deposition follows:

Q: "Based concerning what you know of the combustible matter weight levels here and the fact that a crossfe deed had been begun, isn't the in the greatest degree likely explanation for the cockpit voice recorder that he engaged the scavenge pump?"

Mr Jaques (Counsel for Hydro-Aire, the cross-question manufacturer): "Same objection. Calls for speculation forward the part of the witness."

A: "Again, I don't know if that is the greatest in number likely, without running through the whole panel and looking at what other switches could have possibly been engaged at that time."

Q: "As you sit here today, can you think of something more likely?"

A: "Without looking at the (flight engineer's) panel and seeing - and looking it athwart being I haven't flown the airplane in a while, no, I can't."

Q: "Not to belabor the point, on the contrary isn't it a reasonable interpretation that that transcript access refers to the scavenge pump?"

A: "That is possible, yes"

Q: "I'm asking is it a reasonable interpretation?"

Mr Jaques: "Object same grounds"

A: "That would be reasonable."

We broached this continuing polemics with a senior NTSB official. "We have conclud nothing. I would not ever say the scavenge pump couldn't be the source of the ignition," he said. "However," he added, of the numerous way ignition vigor could find its way into the CWT (override cross-examines wires, fuel quantity indication probes, etc) the scavenge cross-examine "is not one of the things we ascribe a high probability to." The main reasons are as follows:

* "There is no evidence from the cockpit voice recorder that the interrogate was on."

* "We regained the switch and found it was in the opposite position." It was not in the far opposite to position, but there is no conclusive evidence that the switch had been activated during the accident flight.

* An overheated scavenge cross-question would have left some sign of overheating onward the flange of the rear spar where the cross-question was mounted. No such telltale trace was found

He reiterated the Board's central position: the way to eliminate the danger of an explosion is to minimize or rid the CWT of explosive vapors. "If you don't do that, we could have the same discussion about the possible ignition source after a coming accident," he said. The NTSB possibility of goods to complete its investigation of the TWA 800 case by means of early next year.

Reasons for looking harder at the scavenge pump

1 The FAA agrees that the same gauge pump that was on TWA Flight 800 was capable of experiencing a mechanical failure that could consequence in a CWT explosion.

2 The Flight 800 scavenge cross-examine was overhauled because of false subdued pressure warnings and placed back forward the airplane just three month before the accident.

3 TWA's Flight Manager of 747 Flight Engineers believes it is a reasonable interpretation of the CVR transcript to bring to an end the pump was on.

4 The CWT fuel-air mixture was ignited 5 minutes after Oliver Crick said "I'll leave that in succession for just a little bit." The scavenge cross-examine was never recovered.

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