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Special Event

NTSB Aviation Safety Director Bernard Loeb Testifies at TWA Flight 800 Final Report Review

Aired August 22, 2000 - 9:57 a.m. ET


BILL HEMMER, CNN ANCHOR: Back to Washington, Bernard Loeb now at the microphone, the second of many who will speak at these two-day public hearings. Bernard Loeb is the -- from the NTSB. He's the rector of the Office of Aviation Safety, now speaking.


BERNARD LOEB, DIR., NTSB OFFICE OF AVIATION SAFETY: ... reconstruction of the airplane fuselage and parts of the cabin interior that took place on scene on Long Island. And, indeed, that massive effort symbolizes the extent to which this investigation has gone, and leaving no stone unturned.

Al Dickinson, the investigator in charge, will be discussing the on-scene portion of the investigation in his opening remarks, so I will not go into detail about that at this time.

What I am going to do is to summarize the significant findings of our investigation. This will be just an overview. More detailed explanations will be provided by investigators during their individual presentations over the next two days. But I think an overall summary of what you will be hearing would be valuable to put things in context.

First, we knew almost immediately after the accident that TWA Flight 800 had experienced an in-flight breakup. This was strongly suggested by the radar data. There was a loss of transponder returns, and the primary radar returns indicated that pieces had departed the airplane and were fairly widely dispersed in the ocean.

The wreckage recovery locations made it evident relatively early in the investigation that the in-flight breakup was initiated by an event in the area of the fuselage near the forward part of the center wing tank. Specifically, pieces from the forward part of the center wing tank and adjacent areas of fuselage were recovered from the westernmost portion of the wreckage field, the portion of the wreckage field closest to JFK Airport, from where Flight 800 took off. This first wreckage area is referred to as the Red Zone.

The recovery of the pieces from the Red Zone indicated that they were the first pieces to separate from the airplane. The nose portion of the airplane was found further to the east and what was labeled the Yellow Zone, indicating that this portion of the airplane separated later in the breakup sequence. And most of the remaining wreckage was found in the easternmost portion of the wreckage field farthest from JFK, which was labeled the Green Zone.

Further, analytical studies of the trajectories of the departing pieces of the airplane were consistent with the wreckage recovery findings. This basic evidence, the radar data and the wreckage recovery locations, indicated that the airplane broke up in flight and that the breakup initiated in the area of the fuselage near the forward part of the center wing tank.

On the basis of this initial information, we considered several possible causes for the initiation of the in-flight breakup: a structural failure and decompression; a detonation of a high-energy explosive device, such as a bomb or missile warhead; and a fuel/air vapor explosion in the center wing tank.

We found no evidence that a structural failure and decompression initiated the breakup. A thorough examination of the wreckage by our engineers and metallurgists did not reveal any evidence of fatigue, corrosion or any other structural fault that could have led to the breakup.

As a side note, I would like to mention that there was absolutely no evidence of an in-flight separation of the forward cargo door, one of the many theories suggested to us by the members of the public. The physical evidence demonstrated that the forward cargo door was closed and latched at water impact.

We also considered the possibility of a bomb or missile. However, high-energy explosions leave distinctive damage signatures on the airplane structure, such as severe pitting, cratering, hot gas washing and petalling. No such damage was found on any portion of the recovered airplane structure. And as you know, more than 95 percent of the airplane was recovered.

Our investigators, together with many outside participants from the parties to the investigation, closely examined every piece of recovered wreckage. All of the participants agreed that none of the wreckage exhibited any of the damage characteristic of a high-energy explosion. That is, of a bomb or a missile.

Further, no missing portions of fuselage were large enough to represent the entry of a missile. You may have noticed that some of the photographs of the reconstruction show what appear to be several large missing areas, such as those that are shown on the screen now.

However, almost all of the fuselage structure in these areas is actually attached to the adjacent pieces but has been folded back or crushed in such a way that it does not cover its original area. Therefore, these large gaps that appear to exist in the reconstructed fuselage do not represent areas of damage that could have been caused by a missile.

In addition, we found no localized area of severe thermal or fragmentation issues and no localized severe damage or fragmentation of the seats, as such as would be expected if a high-energy explosive device had detonated inside the airplane. The injuries to the occupants and the damage of the airplane were fully consistent with an in-flight breakup and subsequent water impact. In light of all this evidence, a bomb or missile strike has been ruled out as an initiating event of the in-flight breakup.

The FBI did find trace amounts of explosive residue on three pieces of the wreckage. However, these three pieces contain no evidence of pitting, cratering, hot gas washing or petalling, which would have been there had these trace amounts resulted from a bomb or missile.

Further, these trace amounts could have been transferred to these pieces in various ways. For example, in connection with ferrying troops during the Gulf War or during dog-training explosive detection exercises that were conducted on the accident airplane about one month before the accident.

There is also the possibility that the explosive residues could have been deposited on the wreckage during or after recovery operations as a result of contact with the military personnel ships and vehicles used during those operations. We don't know exactly how the explosive residues got there, but we do know from the physical evidence I've just discussed that the residues were not the result of the detonation of a bomb.

Unlike the other two scenarios I've just mentioned, a structural failure or high-energy explosive, the third scenario we considered, a Jet A fuel/air explosion in the center wing tank, was consistent with the physical evidence. Specifically, as I've already mentioned, the wreckage recovery locations indicated that the first pieces to depart the airplane were from in and around the front of the center wing tank.

Based on these recovery locations and damage characteristics, the investigative group led by Jim Wildey, known as the Metallurgy and Structure Sequencing Group, determined that the earliest event in the breakup sequence was an overpressure inside the center wing tank that caused structural failure of its forward part. This overpressure event started the breakup sequence that ultimately resulted in the destruction of the airplane.

I would like to emphasize that all of the parties to the investigation, as well as numerous outside experts and researchers, have agreed with the findings of the sequencing group. Jim Wildey will be explaining the breakup sequence a little later today.

The point I would like to make now is simply that the initial breakup sequence and early departure of pieces from in and around the center wing tank clearly indicate that the breakup was initiated by an overpressure inside the center wing tank. Given that there was no high-energy explosion in this or any other area of the airplane, this overpressure must have been caused by a fuel/air explosion inside the center wing tank.

However, questions were raised early in the investigation about whether the conditions necessary for a fuel/air explosion could have existed inside the accident airplane's center wing tank; and also whether a Jet A fuel/air explosion could generate sufficient pressure to break apart the fuel tank and destroy the airplane.

To address the first issue, the Safety Board conducted flight tests at JFK in July of 1997 using a 747 leased from Evergreen Airlines. Several test flights were conducted under conditions similar to those experienced by Flight 800. The fuel/air vapor inside the center wing tank was measured at various locations during the flight.

The temperatures inside the center wing tank at the altitude at which the accident occurred, approximately 13,800 feet, ranged between 101 and 127 degrees Fahrenheit. Extensive work done by scientists at the California Institute of Technology showed that the Jet A fuel under the conditions experienced by Flight 800 would have been flammable at these temperatures. In fact, their work demonstrated that fuel vapors under those conditions may have been flammable at temperatures as low as 96 degrees. Dr. Joseph Kolly will be talking more about this research later today.

The second issue, whether an explosion of Jet A fuel could generate sufficient pressure to break apart the fuel tank and destroy the airplane, was also put to rest in the investigation. Laboratory tests and quarter-scale tests under the direction of scientist at the California Institute of Technology demonstrated the pressures exceeding the structural limitations of the forward portion of the center wing tank were produced from the combustion of a Jet A fuel/air mixture similar to the one that existed in the center wing tank of TWA Flight 800.

HEMMER: Bernard Loeb, again, giving his testimony there live at those open public hearings in Washington regarding the fate of TWA Flight 800 from four years ago, this past July.

A couple of things, conclusions: a massive breakup in flight on a massive scale. We knew that from the evidence it hit the water shortly thereafter. No evidence of a high-energy explosion. And you saw the graphic on the screen there saying, quote, "bomb or missile strike ruled out."

That's the latest from there. Back to Susan Coughlin with us.

And, Susan, what was your take on the testimony we heard?

SUSAN COUGHLIN, CNN AVIATION ANALYST: Well, my take, Bill, is exactly what we were discussing earlier, that the NTSB is painstakingly walking through this investigation to look at whether there was -- three things that Dr. Loeb discussed: whether there was a structural failure of the airplane that might have caused it to crash; whether there was a detonation, either internally or externally, that could have caused the breakup of the airplane; and third, whether the conditions existed for a fuel/air vapor explosion.

And it's very clear going through the evidence that Dr. Loeb recited that they had eliminated to everyone's satisfaction structural failure of the airplane, detonation. And now they're moving their investigation and their focus into this Jet A, air/vapor explosion and walking through why they're so convinced that that was the case.

HEMMER: A couple of things stick out in my mind from that time, being up in East Moriches myself. There was so much damage spread out over such a wide area. 747s do not typically just drop out of the sky. And if you remember what was happening in the country at the same, the Summer Games opened up two days later and that bomb in the Olympic Park happened nine days after that. I guess there's reason why the public was thinking, anyway, this could have been a terrorist act, correct?

COUGHLIN: Absolutely. But that was the same reason that the government was, or the FBI was involved in this investigation for such a lengthy time, was that the environment in this country and the mood at the time and previous events would have dictated that that would be one of the things they'd look for.

But let me also say, Bill, that in every investigation that the NTSB does, the FBI is asked to come in and has a statutory obligation to come in to rule out a criminal act or an act of sabotage in the immediate aftermath of a transportation accident, whether it be aviation or rail or any other. And so it was highly appropriate despite the environment at the time for the FBI to have been involved; and to this extent was certainly unusual, but warranted in the circumstances.

HEMMER: Susan Coughlin, thanks again for your insight there, live from Washington. Susan, thank you again.

It was back on July 17, 1996, almost 1,500 days ago, when Flight 800 went down, killing all 230 people on board. We'll track those meetings, not only today but also tomorrow, and let you know what we glean off the meetings there in Washington.



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