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You are quite welcome; truth be told, I don't need much of an excuse to go fly...it is one of the bona fide rewards of my job. I thank you very much for your candid and considered comments on our book. In my mind, criticism is the life-blood of an author, even more so a fledgling author as myself. I continue to learn with every effort. This is no different. I hope you will not object to a continuing exchange on this very important topic; y've made some cogent & focused observations that deserve further exploration.
"...black sections to be disturbingly undistilled."A fair comment. In all the decisions we had to make, this one and its ancillary cousins was one of the hardest. We chose literal starkness over literary largess. This had to play with the struggle to use informed or intelligent fiction to fill in the gaps. We chose not to make this work a journalistic work; our object was not to find or define the smoking gun, but rather to cause others to ask more pointed questions & seek more enveloping answers. The reality is, it is what it is; the die is cast; the criticism is valid nonetheless.
"...simple story: a small explosion inside the volatile empty tank..."Indeed, this is the essence of the argument. Design practice has, for many decades, involved the elimination of hazards, and where they cannot be eliminated, to achieve an acceptable level of safety to preclude realization of a hazard. It is the latter aspect that has driven fuel cell design since WW2. Obviously, I do not share your simplified assessment, and I do not believe most design engineers or safety engineers would either. It is my familiarity, experience and history with a variety of aircraft and design variants that leads me to be so skeptical of the popular image of a simple errant spark or catastrophic failure of one of the pumps or fuel quantity probes as the source of ignition. Is this simple scenario possible? Yes, absolutely; in fact, it is quantifiable to an extent. There is no such thing as perfect safety; we could not afford it even if it was possible. Now I fully realize it will be easy to discount my words...he's a pilot-engineer, former experimental test pilot, rationalizing his blind faith in aircraft design; those are choices for any reader/debater. However, I am compelled to say, the key is in the details of the design process. Below, I will offer some suggested questions or points of interest to aid in the understanding. But first, you refer to several of your articles as well as specific incidents that deserve comment.
From your clip of May 10, 1997 story:"catastrophic mechanical failure" - fact beyond question...the explosion of the CWT was just such an event. The CWT "...is what opened up the airplane and started the events. . . ."; again, beyond question. "The real question is what made it explode?" - the germane, root question. "...leaving a potentially dangerous mix of fuel and air" does not go far enough; it is not potentially dangerous; it is in fact dangerous. Virtually every fuel cell, fuel tank, drop tank or whatever contains a highly explosive fuel-air vapor. The military has implemented enhancements like nitrogen-inerting and 'explosafe' to reduce the volatility of fuel cell vapors, but the predominate design philosophy as I stated earlier is elimination of potential ignition sources. "...heat from the unit heated the fuel and air inside Flight 800's tank into a volatile vapor" is true for virtually every B-747 ever built operating in summer ramp conditions; this implies the heat from the cooling units produced the conditions when in fact the conditions exist any time the CWT is empty, winter, summer, ground or air. "Worn-out parts inside the center tanks of older 747s, in particular, are more likely to overheat, emit stray sparks and generate static electricity, the documents show..." is fundamentally wrong; while at face value, anyone would think this statement to be true, when you look at all the properly installed parts contained within fuel cells, this is about as near to impossible as we can get. The essence of this focus lies in the specifics of the design. To understand why I say this, you must look at the details of the design of each components and its operating environment. I could go further, but the interpretation of engineering or investigative safety testing can only be done in the context of the detail design. The discussion about fuel pumps overheating or over-voltage arching in fuel probes must be in that context. While I am not the fuel systems design engineer for Boeing or the B-747, I have witnessed similar fuel system tests for other aircraft. An overheated pump will not be itself ignite a fuel-air vapor. All electrical components I'm aware of are contained within multiple layers of isolation. I find Marsden's argument to be quite weak for a host of reasons. So, what are the questions:
Given authoritative answers to the above, I think you will find the acceptance of an internal ignition sources to be quite difficult. The other examples you cite involve external ignition sources...lightning, broken manifold spraying fuel, etc. Furthermore, if I recalled the B-747 CWT design drawings, the transfer & scavenge pumps are located at the rear of the tank, not the forward portion; even if they were in the forward portion of the tank, their location does not connect them with the documented burn damage. A small penetration in the vicinity of the forward wing spar [recovery part CW504 being of particular significance] could have been an external source.
"...the myriad ADs calling for fixes..." implies that ADs themselves are a definition of hazard; I must respectfully and categorically reject such an implication. I've read those ADs in detail; they are precautionary, investigative and preemptive, not an establishment of hazard or risk. OEMs struggle to find the correct balance between safety and alarm; it is never an easy task. The relevant B-747 ADs I've seen do not substantiate any hazard.
"For me the hard evidence points to the center scavenge pump or center-tank fuel probes (both unrecovered) as likely ignition sources." Unfortunately, I have seen no such hard evidence to justify this conclusion. Is it possible? Yes. However, if you look at the answers to the above design questions, I suspect you will back away somewhat from this conclusion.
As far as the discounting of the eyewitness data [seriously restricted as it is], I can only say I have watched many films and witnessed first hand numerous in-flight break-ups of various aircraft for various reasons. None of them match your description, nor do they even remotely match the CIA animation version. If the eyewitness data was so easily discounted, why on earth would the FBI persist in exclusion of the eyewitness data? Why would they create and maintain the major rift between themselves and the NTSB? There are just too many why's here. As we discussed, I do not mean to suggest, imply or otherwise lead anyone to think the answers lie within the eyewitness data; but, as I also stated, the eyewitness data is valuable nonetheless, and there is no logical reason to exclude it from public scrutiny.
"From Iran's perspective, if the downing of TWA 800 was such a heroic act of justifiable retaliation against a great Satan, why has no one stepped forward to bask in the associated glory?" Clearly, we failed to make that case, I guess. The answer is my mind lies in two parts: 1.) as stated in the Koran, retribution is a solemn if not sacred act for the wrongful taking of innocent life, and 2.) if our scenario is accurate, the involvement of state assets, i.e., the submarine, would, by defintion, classify the incident as an act of war. To truly devote Muslims, as the Iranian clergy and leadership at the time was, public recognition would not be consistent with the teachings of the Koran - gloating is not spiritual.
Byron, please excuse this laborious reply as well as any suggestion of disagreement. I am still searching for answers. Our book does not provide the answers. Our objective was to extend the investigation beyond the superficial condition of the currently available public information. This is one of the most aberrant aircraft investigations in history - from the FBI's intrusion, to the exclusion of eyewitness data, to the easy conclusion without a stitch of substantive evidence. My gut tells me there is much, much more to this incident than the press has been able to surface or the government has been willing to disclose. This thing stinks in so many ways. As I said, it is exceptionally easy to discount our scenario or my words, but why would a responsible, concerned citizen who happens to be an engineer, an experienced, former, experimental test pilot and who has been around aircraft all his adult life, think such things. I am not a conspiracist. I believe in my government. I believe in the inherent integrity of the investigators. Why? Simply restated: this thing stinks.
After this, you may not want to continue the exchange, and if so, I will understand. You have other stories to follow, develop and deliver. In the end, I am just a simple guy who sees this for what it is and wants to understand. I am still searching.
Thank you for your candor, your interest and your professionalism. I hope we can continue this exchange and others in the future. Thanks for visiting our little corner of paradise. Take care and best wishes.
Byron,
Cap did me the courtesy of including me in his reply to you and I wanted to add my voice to his on one aspect. First, let me thank you for your criticism, it is appreciated. You make many valid points.
The point I want to make is that the final character in the title of our book is a question mark, not an exclamation point. Our purpose in putting together the Iranian scenario was to formulate an explanation that took into account the available factual evidence (and all of it) and fill in the blanks to show how it might have occurred. The purpose in that was to raise legitimate questions regarding the process which occurred in the media and government inquiries into the TWA disaster. Those questions remain valid even today.
When I was interviewed by a reporter from the Santa Barbara News-Press about the book, he asked me "Do you really think the Iranians shot down that plane?" My response was that if I were the prosecutor or defense attorney trying a murder case, no reporter would dare ask me whether I personally believed in the guilt or innocence of the accused. It is irrelevant and unethical for an advocate to give his own opinion. What the advocate must do is to weave the available evidence into a construct which the jury can view to make their own conclusions. That advocate's job is much the same as a journalist's, to gather the facts, make minimal value judgments beyond confirmation of facts and if the conclusion is not readily apparent, give the reader as much help in reaching a conclusion as he can, without fabrication or adjudication on the part of the journalist. That was our goal in the book. However, as authors we had a lower standard of proof than either the prosecutor or defense has, we merely needed to prove to our readers that there was good reason to keep asking questions or to make sure that the next time we do things differently.
In answer to your specific question about why the Iranians did not readily admit their complicity in the shoot down, if, indeed, it was a worthy act of retribution, I answer this: Like all nation states, Iran has a public and a secret agenda. The United States government has many covert activities that it feels are reasonable and necessary for the nation to carry out, but which it would never admit to publicly. Likewise, Iranian leaders, even the radical theocrats, spent much of the last two decades undoing the negative world image that their Islamic Revolution/Hostage Crisis era gave them. They realize they must act diplomatically (at least overtly), even if they also carry out the well-documented covert terrorist activities for which Iranian national leaders have been indicted in German courts and elsewhere. If they did carry out the shoot down, for either geo-political or retribution reasons, it would be extremely foolhardy if they made public note of it, especially if they had gotten away scot-free. If their test use of the submarine insertion tactic was successful, they would never announce it, for fear that their sub base on the Arabian Sea would have a similar fate to the Libyan Intelligence HQ or downtown Baghdad or Belgrade.
The bottom line for me on the Iranian issue, and it is really a separate issue from the main TWA question, is that the Iranian scenario could have happened and it could still happen, in that form or some other tactically plausible form. The Cold War may have ended, but I am not entirely sure the world is really a safer place. The threat and the weapons of choice have merely changed. Both the Pax Romana and the Pax Britannia ended when the geo-political and strategic pre-eminence of the super-power(s) dissolved and allowed lesser forces like the Visigoths and the Kaiser to challenge the superpower(s) without fear of immediate and total annihilation. So too, the Cold War period (even with Korea, Viet Nam and Afghanistan) can be viewed as a stable period in relation to the first half of the century, and I perceive we are moving into a very tenuous period in which resurgent nationalistic and theocratic forces are at work everywhere, putting world peace and stability in jeopardy. If our "white icon" chapters do not provide a true answer, they, at least, provide a warning.
I fear I have added to what Cap calls a "laborious answer," but I trust in your understanding of my purpose.
Sincerely,Cap:
I don't mind at all. And I certainly respect the viewpoints you expressed in your previous response. I really have no qualms about your perspective differing from mine. I hope you feel the same way. I don't think there's anything wrong with disagreeing about which way the evidence leans. Such discussions, I believe, are part and parcel of a healthy, reasoned debate.
Cheers,Subject:
Byron,
Thank you very much. To be candid, Byron, the exchange of views, ideas, and philosophy w/ you was a dream come true. I love the debate...the clash of ideas; it is so invigorating. I most certainly respect your views. We knew there would be many who would disagree, who would discount the questions we raise, and who would attempt to label our work as a trivial attempt of deranged conspiracists. We knew those things going in. In fact, we agonized over many aspects of the book with those doubts in mind. The open, dynamic and vigorous conflict of words, ideas, thoughts, views and feelings is what makes democracy so grand & glorious. Kevin said it far better than me; he hit the essence precisely. I hope we can continue our dialogue. Again, thank you so much for taking your precious time to provide such an eloquent response; we are honored. Take care & stay in touch.
Cheers,Kevin and Cap:
Guess it's my turn to get laborious. You're overlooking the fact that most often the vapors in an "empty" center tank are too cool to ignite. In TWA 800's case the combination of warm weather and extended ground operation of the AC packs heated the vapors above flash point, when only a tiny spark was needed for ignition. Keep in mind Boeing argued a variation of what you've suggested: the company insisted there were no conditions under which the vapors could heat above flashpoint. Investigators had to run the AC packs on a 747 under the same conditions TWA 800 experienced to discover that assertion was false. I agree with you that an empty fuel tank does not pose a hazard most of the time, otherwise we'd see more explosions. Indeed, had the TWA jet flown a while longer the center tank would have cooled enough to where a stray spark in the center tank would have been harmless.
You ought to take a closer look at the 737 explosion in the Philippines and the B52 explosion at Sawyer AFB. Both those cases provide hard, historical evidence of distinct, well-understood instances of stray sparks from a faulty internal system igniting fuel vapors, the former involving a fuel sensing component, the latter a dry-running fuel pump. These two explosions served as precursors, if you will, of TWA 800.
There is a well-explained theory about how the missing scavenge pump could have emitted a spark precisely in the area where investigator know for certain, based on the rebuilt center tank, the initiating explosion occurred -- a few feet forward of the missing pump. The theory, which has something to do with the physics of gathering forces in a closed space, was outlined in detail by an expert hired by one of the plaintiff lawyers, Lee Kreindler, and submitted to the NTSB. Kreindler, by the way, helped expose the erroneous botched-CIA-sting scenario that clouded the investigation of Pan Am 103 for so long.
Also I believe some of TWA 800's missing fuel probes -- possible sources of electrical sparks -- were located in the vicinity of the initiating explosion. The fuel tank ADs, the 737 Philippines explosion, and United Flight 811 (the 747 whose forward cargo door was back-driven open past weak locks near Honolulu in 1989, killing nine passengers) all underscore how a spurious electrical charge can, indeed, jump wires on complex aircraft electrical systems with disastrous results.
Contrary to your assertions, the evidence confirming the possibility and plausibility of accidental ignition of explosive fuel tank vapors from an internal aircraft system source is both extensive and substantive. By contrast, the singular explanation you've proposed -- that the witness reports, FBI's fumbling and Middle East political backdrop all somehow add up to an untraceable terrorist's missile, or fragment thereof, providing the ignition source -- is, in my opinion, comparatively weightless.
The more important issue here is to focus on what TWA 800 is trying to tell us in terms of preventing a similar disaster. I do not believe the lesson is better tracking of Iranian submarines. The aviation safety community ought to be moving aggressively to mitigate hazards posed by aging aircraft systems, such as dry-running fuel pumps or various sources of spurious electrical sparks that could ignite fuel tank vapors we now know can and will, under some conditions, rise above flashpoint.
The danger of fomenting an Iranians-did-it scenario is that you may detract from a focus on addressing aging aircraft systems.
Sincerely,Byron,
Well, now, we upped the ante at little haven't we. Neither one of us appears to be making headway with the other. There is a limit to this exchange, however I would like to clarify a few points. I shall start with the last first.
"The danger of fomenting an Iranians-did-it scenario is that you may detract from a focus on addressing aging aircraft systems."
I appreciate your admonition. In fact, aging aircraft has been a professional concern for many years; you can find considerable evidence of my professional engineering position at Raytheon Aircraft regarding the aging aircraft issue. For this event, it is a risk we feel we must take. It is categorically not our purpose to distract anyone from the root cause of any accident/disaster/catastrophe. But, what if we are correct? And, I will restate below...above all the bizarre accidents in aviation history, this one alone stands out beyond all the others; that fact alone deserves attention & scrutiny. Kevin and I, with agonizing reluctance, chose to take pen in hand on this incident. We have placed ourselves in the harsh light of public criticism for one reason and one reason only - the truly unique characteristics of this investigation. Quite frankly, I prefer fiction to non-fiction. Neither of us professes to be investigative reporters as you are. We are simply two, concerned citizens who see considerable strangeness enveloping TWA 800 and are disturbed by the ease with which the media and public are ignoring that strangeness.
For the record, the only reason the Islamic Republic of Iran has entered this story is their profound, open and substantial support of terrorism - so-called state-sponsored terrorism. As we've stated many times, our scenario is NOT a definitive answer or substantiation beyond a reasonable doubt. But, as Kevin so eloquently stated, this is a statement of probable cause in a circumstantial evidence case. As a point of focus, given a criminal event, they were the only group with the motive, means, and professed determination to execute such an act; thus, the center-point focus. We have tried to separate the Islamic religion and the Iranian people from the radical and, at the time overtly supportive, theocratic political leadership of IRI. Agreed, we have not established their culpability beyond a reasonable doubt; that is not our responsibility or purpose. So, in deference to your admonition, I feel the need to persist on a few points.
Spurious electrical faults have always been a design as well as an operational problem. You cite one of the most infamous - United 811. I have done many hours of testing and seen first hand what induced current from high-powered, electromagnetic interference can do to aircraft systems. Your contention, as well as others, of the potential of a higher probability of electrical anomalies due to aging systems does not match all the related data in this case. Is the popular scenario possible? Yes, absolutely. I can neither prove it nor disprove it. I have seen first hand many variations of spurious electrical faults due to failure, external inducement, poor design and many others. The elements that keep hanging me up on this particular incident and the purported popular scenario of an internal electrical fault are the all the investigative anomalies foisted upon the NTSB.
"…AC packs heated the vapors above flash point, when only a tiny spark was needed for ignition."
This is not an unusual occurrence. In fact, in summer or hot climates like Saudi Arabia, I would say this is normal. To my knowledge, kerosene-based fuel, as in common usage by commercial and military turbine aircraft, do not spontaneously combust, which means there must be a sufficient energy source [e.g., spark] to ignite the vapor. The implication of this line of reasoning is that the overheated fuel somehow contributed to the explosion. The conditions in the TWA 800 CWT are common in many aircraft in hot conditions, and certainly other B-747 aircraft in similar conditions. The bottom line, from everything I have seen is, the fuel temperature and fuel-air vapor pressure/temperature, although elevated above expected levels still required an ignition source. Granted, the elevated vapor pressure and temperature made the requisite energy of the ignition source less, but does not suggest or validate an internal event. I go back to my comments in the previous message regarding design philosophy and practice. Pumps can and have overheated, burned up and not become an ignition source. Fuel probes have experienced over-voltage events, arced internally and not become an ignition source.
"Contrary to your assertions, the evidence confirming the possibility and plausibility of accidental ignition of explosive fuel tank vapors from an internal aircraft system source is both extensive and substantive."
I do not agree with your assertion of '...extensive and substantive' evidence of internal ignition. I have not see it. Citing the Philippines Airlines B-737 accident in Manila and the USAF B-52 accident at Sawyer AFB no more substantiates the claim of a simple electrical fault than our citing the FBI recalcitrance regarding the eyewitness data or Iranian state-sponsored terrorism as substantiating the missile or terrorist hypotheses. Do they establish a precedent or precursor? To an extent, yes. And, I would feel much better embracing your "...simple story..." if information already in hand was freely released, and a free and open debate was allowed to occur to eliminate the many investigative anomalies. To date, TWA 800 is the only investigation I am aware of that has withheld important supporting data whether relevant or not. Why are we not offended by these restrictions on public information? Normally, the NTSB process presents evidence as it was collected, puts it into context, establishes or refutes any contribution to the cause, and draws a clear picture of what happened. In fact, from the preliminary report, the typical reconstruction of events from the CWT explosion to conclusion is classic, engineering, investigative analysis and reporting. The post-event sequences are not in question. It is what happened prior to CWT detonation and the incredible investigative abnormalities that are in question. Could this be a distraction as you assert? Yes, although not by design, intention or purpose.
Why is it so easy to ignore these glaring investigative anomalies in the work of the NTSB - an agency that prides itself on thorough, exhaustive, methodical, engineering investigations and has a significant record of such work? This is the only event I am aware of that has had so many restrictions, obstacles and limitations placed on the proven expertise of the NTSB. Is it connected to anything else? Perhaps not. But, why is this event the only one? These anomalies have not occurred in Swiss Air 111 or Egypt Air 990, and yet both accidents have disturbingly similar characteristics to TWA 800. Why is it so easy to accept these anomalies - unique in the annals of aircraft accident investigations? Why have we not seen all the eyewitness data? Why have we not seen the detailed analysis of CW504? Why was Charlie Bassett not asked to do the proper, thorough, determination analysis of the red-stain material? Why? Why? Why? Far too many why's for an event of this nature. Could it be that the FBI's zealousness and intrusive actions created this onerous aura surrounding TWA 800? Yes, certainly; but, it is undeniably still present to this day. And, it could also be, there is much more to this disaster than we are aware; thus, our reluctant submission to public criticism.
You have studied many notable aircraft accidents. You have won the prestigious Pulitzer Prize for your reporting on the B-737 rudder actuator problem as the primary cause factor in both the Colorado Springs and Pittsburgh accidents. Those two accidents were two of the hardest accidents the NTSB has had to investigate. Those investigations along with virtually every other investigation the NTSB has conducted use a well-established, time-proven process for causal determination. I am certain you have read many NTSB reports, both preliminary and final. I am sure you can see the unique strangeness of this particular incident. Do these investigative anomalies bother you, or cause you to question what is unsaid? I cannot refute your claim of a "...simple story..." any more than I can prove a terrorist event. If this incident was so simple to explain, why do these unique anomalies persist to this day? We are not trying to distract but to seek answers, just as the NTSB doggedly did in all the other accidents they have investigated.
After Swiss Air 111 and Egypt Air 990, I received many messages via a variety of means seeking my endorsement of conspiracy theories that linked those accidents to TWA 800. There are many similarities of these two later accidents with TWA 800. But, I have no suspicions about those two subsequent, similar accidents. I have confidence the NTSB [CTSC for SR111] will clearly define the cause factors in those accidents; I also believe the NTSB can determine the cause of TWA 800 if all these constraints are removed. I want the same resolution to TWA 800. I want the NTSB to be allowed to do their normal professional jobs without interference and openly report their findings to the world as they have done on very other accident they have investigated. I do not want this accident to be so far outside all the other NTSB investigations. The NTSB has not been allowed to do their job as they have done so well on all other accident investigations. Until they are, we shall persist, and hope others are equally disturbed by the unique anomalies of the TWA 800 tragedy.
I truly appreciate your journalistic skepticism, and I thank you for your continued exchange on this important topic. I doubt I have shaken your confidence, but it is always worth a try. I believe one day we will know definitively what happened to TWA 800 just as we know the cause of United 811. I have faith. I just cannot see the '…simple story…' in clear, definitive terms, yet. We shall see. Take care.
Cheers,
TWA 747 WASN'T FIRST TO EXPLODE IN MIDAIR -- TWENTY YEARS AGO, IRANIAN FREIGHTER CRASHED IN SPAIN Wednesday, 07/24/1996-- NEWS -- FINAL -- Page A1 -- 15 inches
The crash of TWA Flight 800 was not the first time witnesses on the ground watched as a Boeing 747 burst into flames and tumbled to Earth. In the week since the TWA crash, many commentators, from retired investigators to academic safety experts, have publicly said there was no precedent for a 747 exploding into flames in flight. That has led to speculation of a terrorist bomb in the TWA case. But twenty years ago, in a crash that drew little public attention, a former Continental Airlines 747-100, converted into a freighter for the Iranian air force, exploded in flight near Madrid, Spain. As the jet descended into Madrid in a heavy rainstorm on May 9, 1976, witnesses reported it caught fire and exploded, losing its left wing as it careened to Earth. All 17 on board were killed, including four Tehran-based Boeing employees on the flight. U.S. aviation authorities studied the Madrid crash but were unable to pinpoint a cause. The authorities suspected, but never officially concluded, that either a spark from an electrically driven valve or a bolt of lightning touched off a fiery explosion that ripped apart the plane's wing. The scenario most widely considered was that leaking jet fuel had accumulated and mixed with air inside a "dry bay" section of the wing, above the engine, to create a highly combustible vapor. Boeing has since strengthened the sealants in the dry bays of 747s to prevent leaks. There are no known parallels between the Madrid and TWA crashes. All that's known by investigators, still in the early stages of retrieving and analyzing wreckage, is that the TWA jet exploded into a ball of flames last week off Long Island, N.Y., as the result of a bomb, a missile or catastrophic mechanical failure. Thus far, they have found no traces of explosives on the wreckage recovered from the waters off Long Island. Boeing spokesman Doug Webb had no specific information about the Madrid crash that might be applicable to the TWA tragedy, which killed all 230 on board. "At this point, we're looking at every possibility," Webb said this morning. Bob Barlett, spokesman for the National Transportation Safety Board, said investigators continue to concentrate on retrieving perishable evidence, but intend to "review the history of all similar cases," including the Madrid crash, in due course. In the Madrid case, the left wing landed some distance from the main wreckage, its skin torn off in a pattern indicating an explosion ignited inside the wing. Another theory investigators postulated but never proved in the Madrid case held that an unusual gust of wind or turbulence overloaded the wing. The Madrid crash had ramifications in the United States. After the U.S. Air Force found fuel had leaked into the wing dry bay areas of the two 747s it then operated, the Federal Aviation Administration in late June 1976 ordered all 747 operators to immediately inspect for fuel leaks in the wing dry bay and engine strut, Aviation Week & Space Technology, a respected industry trade magazine, reported at the time. Most found leaks, the magazine reported. ----------------------- 747-100 wing fuel tanks ----------------------- All the fuel on a 747-100 is stored in wing tanks. In a 1976 crash, investigators hypothesized that fuel could have leaked into a sealed cavity above one of the engines, called a dry bay, creating a combustible vapor that ignited. Dry bay: An empty, sealed compartment located inside the wing and directly above the engines, adjacent to wing fuel tanks. Fuel tanks: Jet-wing compartments store thousands of gallons of jet fuel. Cutlines: KNIGHT-RIDDER NEWSPAPERS / SEATTLE TIMES: 747-100 WING FUEL TANKS (SEE END OF TEXT) Copyright 1996 Seattle Times Company Storyid: 2340819, Keywords: CRASH OF TWA FLIGHT 800 Subject: Art: ILLUSTRATION |
TWA FLIGHT 800 -- BLAST SOUND QUESTIONED -- MEMOS WARNED ABOUT
FUEL LEAKS ON 747S, URGED EXTRA CAUTION
08/21/96 -- News -- (A1 -- FINAL EDITION ) -- includes ILLUSTRATION
by BYRON ACOHIDO
credit: SEATTLE TIMES AEROSPACE REPORTER
------------------------------------------------------------------ INVESTIGATORS are examining a section of the plane for clues on what caused the belly and right wing tanks to rupture and burn in the crash last month.
------------------------------------------------------------------
Federal aviation and Boeing service records contain extensive documentation about where the wing and belly tanks on 747s are susceptible to leaks that can cause fire.
NTSB Vice Chairman Robert Francis, who is heading the investigation into the crash of TWA Flight 800, has declined to compare how much credence investigators are giving to the bomb vs. leaky fuel theories.
But investigators have been piecing together the section of the plane they believe will provide them with the most clues on what caused the belly and right wing tanks to rupture and burn, a sequence that most likely began about a half a minute after things began to go wrong shortly after it departed New York's John F. Kennedy Airport bound for Paris.
The center section, between rows 17 and 28, is where the blast is believed to have originated, a source said. Those seats are near where the central fuel tank is located and where the wings are attached to the plane.
An explosive device precisely placed in the passenger cabin above the belly tank or in a cavity adjoining the belly or wing tank would punch a crippling hole in the airplane's most vulnerable, volatile area.
Another way things could have gotten started is if fuel or fuel vapors leaking from the belly or wing tanks accidentally ignited in an adjacent cavity.
"It may have been a two-staged event," said Mike Hynes, an independent crash investigator from Frederick, Okla. "You could've had a malfunction of some kind . . . followed by a big splash of fuel going off."
Federal aviation and Boeing service records on the 747 show several ways that the wing and belly tanks on 747s are susceptible to leaks that can cause fire.
-- Fuel and fuel vapors can seep past each of the thousands of fasteners used to form the front wall of the belly tank. To account for this design characteristic, Boeing applied a rubber-like sealant, called CAT-A-LAC, on the heads of each fastener. As an extra measure of protection against leaks, Boeing also called for application of the sealant on the other end of all the fasteners.
But in 1989 Boeing sent a service document to 747 operators warning that "the secondary fuel barrier may not have been properly applied to some areas . . . An inspection of an airplane in production revealed that the back side of fasteners and brackets may not have been coated as these areas were shielded from the spray. This coating is required to prevent fuel or fuel vapors from entering the cargo and passenger compartments in the event of a failure of a primary fuel seal or a crack in the center section structure."
In 1991, the FAA gave airlines 30 months to inspect for this production oversight and apply the secondary barrier.
TWA officials have said that the Flight 800 jet complied with this and other federal directives.
-- Another FAA directive, last updated in 1994, instructs 747 operators to repeatedly inspect hundreds of fasteners in a 10 foot length of the wing tanks above each of the inboard engines - an area in close proximity to the fractured and scorched parts of Flight 800's right wing. Fastener holes on jets with more than 13,000 flights are prone to begin cracking and leaking near the inboard engines and into cavities where electrical pumps and wiring are housed.
-- Most recently, an airline discovered that when electrical insulation on a 747's fuel pump failed (the plane was on the ground at the time), electricity burned a hole in the pump's case, letting fuel leak and then igniting it.
On Aug. 7, in a move officials said was not related to Flight 800, the FAA proposed a directive requiring regular testing and possible replacement of 747 fuel pumps. Following a 90-day comment period, the FAA will decide whether to issue the order.
An extensive account of how a small fire or explosion near the 747's fuel system during flight can escalate in disaster was detailed in the late 1970s when the safety board concluded a 30-month investigation into the 1976 fire and explosion of an Iranian air force 747-100 near Madrid.
In that case, investigators believe lightning struck a wing, causing a fuel sensor to emit an electrical spark that ignited fuel vapors inside the wing.
An initial flash fire and explosion breached the wing skin above the engine and sent flames licking forward in the slip stream to consume a small section of the wing's front fiberglass edge.
Once breached, the Madrid jet's wing skin began peeling back, causing the wing frame to twist and bend. The buckling of the wing caused the outboard engine to begin oscillating wildly from side to side.
The engine snapped off leaving its fuse pins - fasteners designed to break if the aircraft pitched up or down too drastically - intact.
Flight 800's two right engines were found separated from the right wing, with the fuse pins from both engines still in tact on the right wing. The left engines were also recovered separated from the wing.
As the Madrid jet's wing disintegrated, thousands of gallons of jet fuel spilled into the air, creating a highly combustible cloud of fuel vapor, which fed and multiplied the original small explosion.
Officials have declined to say whether they are discussing the possibility of something akin to the Madrid disaster in the TWA 800 crash.
associated cutlines:
CHRIS SOPRYCH, JAMES MCFARLANE / SEATTLE TIMES: DID FUEL LEAK CAUSE EXPLOSION?
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