Good morning, Mr. Chairman and Members of the Board. As you have just said, the investigation into the crash of TWA flight 800 has been the most extensive and encompassing aviation accident investigation the Safety Board has ever undertaken. It has truly been a monumental effort for everyone involved. Most people are aware of the lengthy underwater recovery operations and the large-scale reconstruction of the airplane fuselage and parts of the cabin interior that took place on scene in Long Island - and indeed, that massive effort symbolizes the extent to which this investigation has gone in 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 just be an overview -- more detailed explanations will be provided by the investigators during their individual presentations over the next two days. But I think an overall summary at this point would be valuable to put things in context.

Cause of the inflight breakup

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 inflight 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 farther to the east, in 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."

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:

1. a structural failure and decompression;
2. a detonation of a high-energy explosive device (such as a bomb or a missile warhead); and
3. 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 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, 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% 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 (bomb or 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 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 injuries, and no localized severe damage or fragmentation of the seats, such as would be expected if a high-energy explosive device had detonated inside the airplane. The injuries to the occupants and the damage to the airplane were fully consistent with an inflight breakup and subsequent water impact.

In light of all this evidence, a bomb or missile strike has been ruled out as the initiating event of the inflight breakup.

The FBI did find trace amounts of explosive residue on 3 pieces of the wreckage. However, these 3 pieces contained no evidence of pitting, cratering, hot gas washing or petaling, 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 the 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 a 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 Structures "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, 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 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 flights. 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 Jet A fuel under the conditions experienced by flight 800 would be 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 scientists at the California Institute of Technology demonstrated that 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. Further, computer modeling of combustion in a full-scale tank confirmed that a localized ignition could generate pressure levels that would cause the damage we saw in the wreckage of the center wing tank from flight 800. Finally, previous fuel/air explosions in the center wing tanks of commercial airliners that contained Jet A fuel have confirmed that a center wing tank explosion involving Jet A fuel can result in destruction of an airplane. Specifically, I am referring to the November 1989 accident involving a Boeing 727 operated by the Colombian airline Avianca that occurred during the climb after takeoff, and the May 1990 accident involving a Boeing 737 operated by Philippine Air Lines that occurred on the ground at the airport.

The bottom line is that our investigation confirmed that the fuel/air vapor in the center wing tank was flammable at the time of the accident and that a fuel/air explosion with Jet A fuel was more than capable of generating the pressure needed to break apart the center wing tank and destroy the airplane. Together with the other physical evidence I have already mentioned, this leads to the inescapable conclusion that the cause of the inflight breakup of TWA flight 800 was a fuel/air explosion inside the center wing tank.

Search for the ignition source

The next obvious question is: what ignited the flammable vapor inside the center wing tank and caused the explosion? Our Systems Group Chairman, Bob Swaim, has devoted the past 4 years to this question. He and his group considered every conceivable potential ignition source. They did exhaustive research and testing - much of it with help and participation from outside experts - to better understand some of these potential ignition mechanisms. As a result of this work, we determined that a number of possible ignition sources were very unlikely in this case. It's important to note that ignition sources that were deemed unlikely under the circumstances of this case could be ignition sources under other circumstances. Bob Swaim, and others, will be prepared to further discuss these ignition sources later today if the Board has any questions about why they were deemed unlikely.

One ignition scenario that we could not deem unlikely, however, was that a short circuit involving electrical wiring outside the center wing tank somehow transferred excess voltage to fuel quantity indication system wiring leading to the center wing tank. Although the voltage in the fuel quantity indication system wiring is limited by design to a very low level, a short circuit from higher-voltage wires could allow excessive voltage to be transferred to fuel quantity indication system wires and enter the tank. We cannot be certain that this in fact occurred, but of all of the ignition scenarios that we considered, this scenario is the most likely.

As I said, Bob Swaim will be telling us much more about this part of the investigation later today.

Maintenance and aging of aircraft systems

The accident airplane was 25 years old at the time of the accident. The electrical wiring that was recovered showed definite signs of deterioration and damage. One of the things that Bob Swaim and his systems group did was examine the condition of electrical wiring in numerous transport category airplanes of various ages from a variety of different operators. What they found was that cracked and damaged wire insulation, contamination of electrical wiring, and noncompliant wiring repairs could be found throughout the transport fleet, but were especially common in older airplanes. Therefore, the condition of the accident airplane was not atypical for an airplane of its age. Although these types of conditions are common, they obviously increase the potential for short circuits to occur and, therefore, are a cause for concern. It became clear from our investigation that current maintenance practices do not adequately protect aircraft electrical wiring, especially with regard to older airplanes. In April of 1998, the Board issued six recommendations to the FAA, aimed at correcting several of the potentially hazardous conditions that we found on aircraft wiring. I am pleased to say that the FAA has taken action towards addressing all of those recommendations.

The potentially hazardous wiring conditions discovered in the context of this accident investigation, have focused attention on the need to change maintenance practices, and to ensure that the integrity and safety of aging airplane systems is maintained. The FAA has begun to address these issues by developing an Aging Transport Non-Structural Systems Plan, and establishing a rulemaking advisory committee. These initiatives are still ongoing, so we do not yet know the final results of these programs. Our draft report outlines our concerns in this area and includes a recommendation to ensure that all of the issues identified by the FAA's plan are addressed. Of course, we will be following the FAA's progress on these issues with great interest.

Bob Swaim will be talking more about this part of our investigation tomorrow.

Design and certification issues

Our examination of the numerous potential ignition sources - and the recognition that many of these ignition sources cannot be reliably eliminated - led us to another concern: the adequacy of the current certification philosophy, which assumes that a flammable fuel/air mixture exists in fuel tanks at all times and attempts to preclude fuel tank explosions solely by eliminating all ignition sources. We concluded that this approach is seriously flawed because experience has demonstrated that all possible ignition sources cannot be reliably eliminated and, further, it is not rational to believe that we can predict all possible ignition sources. Therefore, the most effective approach to preventing fuel tank explosions is to eliminate flammable vapors inside fuel tanks in addition to attempting to eliminate ignition sources.

The results of the flight tests and the flammability research I discussed earlier are especially significant because they indicate that many commercial aircraft may routinely operate with flammable fuel/air vapor inside their fuel tanks. In particular, airplanes that have air conditioning packs located directly beneath their center wing tanks are especially likely to operate with flammable vapor in those tanks because of the large amount of heat generated by these packs. The FAA has recognized this, and has proposed rulemaking that would preclude the use of such designs in the future, unless the design includes a means for reducing the transfer of heat to the fuel tank. One of the concerns we have, however, is that not enough has been done to reduce flammability in existing designs and the current fleet.

This accident would not have occurred, but for the flammable vapor in the center wing tank. And we believe that perhaps the most valuable lesson that can be learned from this accident - and our best hope for preventing similar accidents in the future - lies in recognizing this fact.

The draft report that you have before you does not propose any new recommendations to address fuel tank flammability. But, as you know, the Safety Board already recommended, in December of 1996, that the FAA preclude the operation of transport-category airplanes with explosive fuel-air mixtures in fuel tanks. The Board specifically asked the FAA to consider airplane design modifications, such as fuel tank inerting systems that would make the fuel/air mixture non-flammable. In addition to this long-term recommendation, the Board also asked the FAA to require more immediate, short-term, changes - specifically, to require modifications in operational procedures that would reduce the potential for flammable fuel/air mixtures in fuel tanks.

As I just mentioned, the FAA has initiated rulemaking aimed at minimizing fuel tank flammability in newly-designed airplanes. In addition, the FAA is also evaluating the use of directed ventilation to cool the center wing tank area, the use of ground-conditioned air instead of air conditioning packs when airplanes are on the ground, and fuel-tank inerting systems (both on-board for future designs, and ground-based for the existing fleet). Each of these approaches has some benefit to the existing fleet. But at this time fuel-tank inerting appears to be the most promising method for dramatically reducing fuel tank flammability in both future designs and in the existing fleet.

In addition to our concerns about fuel tank flammability - this investigation and several others, have brought to light some broader issues regarding aircraft certification. For example, there are questions about the adequacy of the risk analyses that are used as the basis for demonstrating compliance with many certification requirements. We believe that the certification approach could be improved by requiring a reliable independent means for overcoming or counteracting any potential failure that could cause catastrophic results - regardless of the calculated probability of that failure. Although these issues are raised in the draft report on this accident, they are not examined in depth. However, we believe these would be appropriate issues to explore in depth as part of the Board's upcoming safety study on aircraft certification.

Witnesses

The final topic that we will address is the reported witness observations. In particular, we will discuss the 258 witnesses who reported seeing a streak of light. There has been a persistent belief, by some (outside the investigation), that the streak of light reported by these witnesses was a missile attacking the airplane. As I have already explained, the physical evidence indicated irrefutably that a missile did not strike the airplane. Nonetheless, because of the media attention and public interest in these witness reports, we analyzed all of the witness documents in great detail in an attempt to understand what the witnesses might have seen. We studied all 736 witnesses for whom we had documentation, including those who reported seeing a streak of light.

As Dr. David Mayer will explain in more detail during his presentation tomorrow, almost all of the witness accounts are consistent with their having observed some portion of the accident sequence. In particular, after the center wing tank explosion and the separation of the nose portion a few seconds later, the airplane continued in its crippled flight for roughly 30 seconds or more, during which time burning fuel from the damaged airplane likely appeared as a streak of light. A small percentage of the reported witness observations (56 of them) were not completely consistent with the airplane's flight path. However, these accounts can also be explained in a number of different ways. As I said, David Mayer will be discussing all of this in more detail tomorrow.

Conclusion

In closing, I would like to reiterate that the physical evidence irrefutably indicated that the first pieces to depart the airplane were from the forward part of the center wing tank; that there was no evidence of a bomb or missile strike, but rather of an overpressure event inside the center wing tank; and that research, tests, and previous accidents demonstrate beyond any doubt that the overpressure was the result of a Jet A fuel/air vapor explosion in the center wing tank.

The safety issues in this accident relate to fuel tank flammability, potential ignition sources, and maintenance and aging of aircraft electrical wiring. I think aviation safety will best be served if we can focus our attention primarily on those issues.

This concludes my remarks.

Mr. Al Dickinson will now address the on-scene portion of the accident investigation. Immediately following his remarks, Mr. Jim Wildey will discuss the breakup sequence of the airplane and take questions.