FAA Fix For Fuel Tank Explosions

[LTNman]

The Federal Aviation Administration said today that it hoped to propose a rule this fall that would require the airlines to cut the risk of fuel tank explosions like the one that destroyed T.W.A. Flight 800.

The rule would take effect in 2006, 10 years after the T.W.A. Boeing 747 crashed off Long Island, killing 230 people, and would have a seven-year phase-in period. It would cover about 3,800 big jets registered in the United States and built by Boeing and Airbus. The agency is in discussions with European regulators, but has reached no agreement with them


For years after they understood the broad outlines of the T.W.A. accident — ignition of the fuel tank by an electrical spark — regulators have discussed a variety of approaches. They talked about altering jet fuel so that it would be less prone to turn to vapor, the form in which it is flammable, or pumping inert nitrogen into the empty space in tanks when planes are on the ground. Both were rejected as too expensive.

But in December 2002, the F.A.A. demonstrated an onboard system that takes compressed air from the plane engines and uses it to remove some of the oxygen from ordinary air, thus raising the level of inert nitrogen, if only fractionally. That nitrogen is then pumped into the fuel tanks.

"We're taking this step because we have found a practical solution," the F.A.A. administrator, Marion C. Blakey, said. "Once planes are equipped with inerting technology, we can close the book on fuel tank explosions," she added. "It's a major moment in the safety of aviation."

The safety fix is also notable for the extent to which the agency used in-house engineering to figure out how to solve the problem.

Airlines could still oppose the F.A.A. solution, however, because of the costs. Installation would probably cost $140,000 to $220,000 per plane, officials said, plus another $14,000 annually for operating costs, which is high but not a record for the agency. And $14,000 would represent only a small fraction of the annual operating cost of an aircraft.

Depending on the size of the plane and its fuel tanks, the system will weigh 100 to 200 pounds, and will require some extra fuel use by the engines to provide compressed air, according to John Hickey, director of the F.A.A's aircraft certification service.

Boeing has said it will use inerting technology in its new 7E7, which is still being designed. The F.A.A. intends to require it on American-registered Airbus A-380's. A prototype of that plane is supposed to fly later this year.

Ms. Blakey, asked why some planes would not be equipped with a preventive system until 2013, or 17 years after the accident, said that the installation could only be done during major maintenance. But she pointed out that the F.A.A. had already issued scores of orders for inspecting or replacing wiring or other electrical components, to reduce the risk of tank explosions. The F.A.A.'s original strategy for guarding against fuel tank explosion was to exclude any possibility of spark, but Ms. Blakey said that with three fuel tank explosions in the last 14 years, the agency did not believe that that approach was reliable.

"We all know that one accident of this type, one accident of any type on board an aircraft, is simply one too many, both for the families of victims and for our airlines," she said. "Reducing commercial fatal accident rates is our No. 1 objective."

But she added that fuel-tank explosions were occurring at the rate of roughly one every five years, raising the possibility of another before a fix is installed.

Flight 800 was initially thought to have been downed by a bomb or a missile, and aviation engineers took some time to come to full recognition of the fuel tank problem. At the time of the explosion of Flight 800, when the Boeing 747 left Kennedy International Airport for Paris on a hot July evening in 1996, many experts believed that it would be difficult for the tanks to explode, because the fuel/air mixture had too much fuel or because the fuel was cold and would not readily turn to a vapor, the form that burns or explodes.

But extensive tests by the National Transportation Safety Board after the crash determined that the fuel/air mixture was often within the range that could sustain an explosion. In the case of Flight 800, the plane was delayed on the ground, with its air conditioners running, giving off their heat to the center fuel tank. As the fuel warmed, its propensity to turn to vapor increased.

Because the plane was not fully loaded and was making a relatively short flight for a 747 with the prevailing winds, it did not need to carry a full load of fuel. As a result, the ground crews had not filled the center tank; it had a few inches of fuel at the bottom, and a lot of air. As the plane climbed into thinner air, pressure in the tank dropped, allowing more fuel to vaporize.

The Safety Board said it could not identify the source of the spark, but examinations of the wreckage, and of other old 747's, found a variety of wiring problems.

[Shuttleworth]

One part of the above caught my eye ..."The F.A.A. intends to require it on American-registered Airbus A-380's".
Bloody yanks .... grrrr....
Seems they have no way of competing with massive sales for this wonderful a/c so they try to damage it in other ways.
( Not invented here syndrome again?)

[Diesel8]

Actually, since the FAA is concerned that this might be an issue, they want to protect the A-380, to make sure it will never suffer from such an accident.

See, you can slant it anyway you like. Not every thing the yanks do needs to be taken as a personal insult or be part of a larger conspiracy.

[lomapaseo]

Great, now that we've earmarked all that $$$$ to save about one aircraft every seven years, the operators won't have the money to waste on unimportant stuff like CFIT system upgrades etc.

way to go public

[zerozero]

"We're taking this step because we have found a practical solution."

A solution to what? What 747 ever suffered a fuel tank explosion *before* or *after* TWA800?

<<The Safety Board said it could not identify the source of the spark>>

The source of the spark was a frickin' SAM.

Man oh man. What a long way to go for a cover-up. And guess who foots the bill? Boeing and the airlines.

Brilliant. Kick 'em while they're down.

[aviate1138]

zerozero, poor sad person, said....

"<<The Safety Board said it could not identify the source of the spark>>

The source of the spark was a frickin' SAM.

Man oh man. What a long way to go for a cover-up."

Aviate 1138 says.....

In the Americans against Terrorism Paranoia way of life, surely had there been one shred of evidence that the mythical missile had ruptured Anything on Flight 800 then we would have heard by now. After all it could have been used as more 9/11 propaganda to invade Iraq couldn't it?

Zerozero name, zero intelligence. 100% paranoia.

Aviate 1138

[Random Electron]

Isn't politics amazing.

Here we have an aircraft exploding in flight, and the investigators put it down to a fuel system weakness, but the aircraft type is allowed to continue to fly.

We have another, smaller aircraft from the same manufacturer which has had a number of crashes which are so far unexplained but the finger of suspicion is pointing at the rudder trim or yaw damper system (can't remember which), but that model is also allowed to continue to fly.

Then we have that large three engined aircraft suffering a catastrophic fire off Canada, crashing into the sea, identified as a fault with the IFE, but what about the aircraft design which allowed the fire to spread so quickly with such disastrous consequences, but what the heck, let's allow the aircraft to keep flying anyway.

But Concorde, which crashed as a rusult of an EXTERNAL factor, ie, runway debris, is grounded for over a year, and eventually killed off.

As I said, isn't politics a curious thing?

[weasil]

I would have thought the reason for retiring the Concorde was more to do with economics rather than politics?

Just a guess though...

[Random Electron]

I doubt it Weasil.

Unlike B.A, Air France were losing their shirt on Concorde operations, so with a merger with KLM on the table, and Concorde operations costing them a fortune, whats an Air France board to do?

Scrub the Concorde, a decision that EADS (formerly known as Airbus) were more than happy with.

That will make the books look a bit better for the KLM merger negotiations.

With Air France grounding Concorde, and the manufacturer withdrawing support, BA had no choice but to follow suit.

I'm sure it was politics, but anyway, I was talking about the various decisions taken about whether to ground a particular aircraft type or not. It's more than a little curious how these decisions have gone over the years.

The grounding of the Concorde following the Paris crash was the straw which broke the camels back, after 9/11.

[zerozero]

Aviate 1138--

Hey man, I won't sink to personal name-calling ok?

But if you were familiar with my other postings (I can forgive such an omission) you would realize that I'm quite critical of Bush Jr and his disasterous foreign policy. In short, I'm not searching for "more 9/11 propaganda to invade Iraq" because I'm of the opinion it's an unjust war to begin with.

Furthermore, TWA800 crashed *five* years before Sept. 11, 2001.

But more to the point, I never claimed terrorism--you did.

No group has ever claimed responsibility for that act. That fact along with the allegation of a cover up can only suggest one thing. I'll let you come to your own conclusions.

As for the "one shred" of evidence that's missing to point towards missle fire, well my friend, there's a ton of information out there and some of it is right here on pprune.

A simple search on TWA800 will reveal more than you asked for including testimony from some high ranking Army officers that actually witnessed the explosion, breakup and fall to earth.

In sum, thanks for allowing me the opportunity to expound on some important points and to explain that I was suspicious even in 1996 when I heard that the FBI was investigating along side the NTSB from the start.

Yes, that was several years before the average fat, dumb, ugly American became fat, dumb, ugly and paranoid.

[Sonic Bam]

Here we go again - conspiracy theories rise like the Pheonix from the ashes (no pun intended - a lot of people died).

The engineers have identified a fix or a least a system to minimise the risk. Everybody concerned with aviation should be looking to promote safety once the risk is identified and quantified.

Saying that, this is going to cost the industry MILLIONS.

[Blacksheep]

Why should it cost the industry millions? The customers aren't interested in safety, they just want to pay a hundred and fifty bucks to fly from New York to Sydney with a 48 inch seat pitch, VOD entertainment and free booze all the way. Something's got to give and if the travelling public are to be protected from every minute risk at tremendous cost, then its the travelling public that ought to pay. And so they did until something called "De-Regulation" reared its head.

De-Regulation was a political gimmick, supposedly meant to remove the restrictive practices that kept fare prices high and open up free competition to the benefit of the public. Many of those allegedly restrictive practices were the industry's way of paying for meeting tightly controlled airworthiness standards. But if we are to be regulated tightly enough to eliminate every possible cause of an accident then we need those so-called artificially inflated fare prices to pay for meeting the regulations. Joe Public will never pay for his own safety unless he is obliged to and as long as he wants cheap travel he should be prepared to accept the increased risk.

[jettison valve]

I don´t want to enter the debate whether inerting is reasonable or not...
But when it comes to the A380, this aircraft should be "safe" of this system: The Air Generation Units will be located -forward- of the -wing- tanks; and on the passenger aircraft, there won´t even be a centre tank, let alone a heated one.
FedEx (and EK?) has ordered freighters, yes. But then again: No "heated" centre wing tank...

I guess they´ll have to find another way to slow down the A380...

J.V.

[Smedley]

Part of the TWA investigation took part in a lab, where they tried to ignite a similar tank under ideal conditions. After weeks of attempting to get an explosion, they quit.

Wunnaful, just wunnaful.

[EasyBaby]

Im not going to promote the whole missle/bomb or any other unexplained incident that brought down TWA 800, but there is one thing that has me wondering. When looking at the wreckage, especialy the rear part of the aircraft, that was supposed to have dived into the sea at over 450mph, it all looks rather undamaged. Looking at photos of another aircraft that dived into the sea in the same way (DC-9 that crashed into the Mediterrainean, i'll try get the photo) the fuselage is crumpled, much the same way as a flattened peice of carboard. The TWA fuselage doesn't seem to have this damage, yet from the reconstruction videos the aircraft dives straight into the ocean. There are large portions of the aircraft skin that retains it's shape. So did the aircraft dive into the ocean at sped or not? I just can't believe the there isn't more crumpling of the fuselage. Any thoughts, or explainations?

[lomapaseo]

...So did the aircraft (TW800) dive into the ocean at sped or not? I just can't believe the there isn't more crumpling of the fuselage. Any thoughts, or explainations?

I don't recall the details of all the radar returns, but the aircraft did break up above the sea while in the so called dive and many of the pieces simply fell to the sea thereafter.

[56P]

Just a thought re TWA 800! Under Annex 13, a law enforcement agency may parallel any investigation UNTIL it has been established whether or not a crime has been committed. IF the crash was indeed caused by an explosion in the centre tank, why does the FBI (who should have withdrawn) STILL refuse to release radar data and satellite photos?

[lomapaseo]

Just a thought re TWA 800! Under Annex 13, a law enforcement agency may parallel any investigation UNTIL it has been established whether or not a crime has been committed. IF the crash was indeed caused by an explosion in the centre tank, why does the FBI (who should have withdrawn) STILL refuse to release radar data and satellite photos?



Radar data germain to the accident is released by the NTSB. Other data including satelite images is either not germain to the accident based on other evidence or is classified since it would reveal capabilities that were not designed for aircraft accident reconstruction.

All such data that was pertinent was made available to the investigators. Data generated outside the official report as well as priveledged data is considered private by agencies/organizations other than the NTSB

[GlueBall]

zerozero ..if you suspect it to have been a missle, then it must have been something bigger than a shoulder launched SAM. And if that's the case, then a lot of people (sailors) are keeping quiet about it.

[Dagger Dirk]

The first post in this thread is from a NY Times article by Matthew Wald dated 17 Feb 2004.

http://www.freerepublic.com/focus/f-news/1080052/posts

The FAA has since announced that this initiative (and many others) is to be shelved until the following decade (at which time it will be announced that it's irrelevant as the affected airplane types are no longer operating and because there's no-one left in the agency who can recall why they were going to do it in the first place)..

So this thread is mighty misleading.

[sammypilot]

Most of you are missing the point. If the FAA say that you should "inert" your tanks and you don't do it then, come any form of incident involving a fuel tank (it doesn't even have to be an explosion) the lawyers will slaughter the airline concerned. They finished off Swissair good style.

The seven years of grace are equally useless because if you have an accident in that period the lawyers and the juries are going to say - "Well you could have done it but you chose to wait."

[CaptainSandL]

It is not only the 747 which has suffered a fuel tank explosion, although it was the most newsworthy example. This from http://www.b737.org.uk/fuel.htm

“To date, two 737's, 737-400 HS-TDC of Thai Airways on 3 Mar 2001 and 737-300 EI-BZG operated by Philippine Airlines on 5 Nov 1990 have been destroyed on the ground due to explosions in the empty centre fuel tank. In 1996, the very high profile TWA 800, a 747-100 mid-air explosion was also determined to have originated in an empty centre fuel tank.

The common factor in all three accidents was that the aircraft had empty center fuel tanks. However even an empty tank has some unusable fuel which in the heat will evaporate and create an explosive mixture with the oxygen in the air. These incidents, have sparked (sic) debate about fuel tank inerting. This is universally considered to be the safest way forward, but very expensive and possibly impractical. The NTSB recommended many years ago to the FAA that a fuel tank inerting system be made mandatory, but the FAA have repeatedly rejected it on cost grounds.

Boeing is now developing a Flammability Reduction System (FRS), this uses bleed air ducted to air separation modules that remove about 50% of the oxygen. This is then mixed with air from a nitrogen generating system and sent to the fuel tank to give almost inert, nitrogen rich, fuel tank air. The FAA Technical Center has determined that an oxygen level of 12% is sufficient to prevent ignition, this is achievable with one module on the 737 but will require up to six on larger aircraft.

Boeing flight tested a 747-400 in summer 2003 with a prototype FRS, data from which will be used to define the production system. A scaled down version of the 747 system was due to be installed on a 737-NG for flight testing in 2004. Boeing will then fit the FRS into some 737 & 747's for in-service evaluation after certification. A 737-200 has been also acquired by the FAA Technical Center for conversion into a fuel tank inerting system testbed.

In Feb 2004 the FAA announced a NPRM that will require a fuel inerting system to be installed on all airliners by 2011.”

Given that this is probably something that could affect any airliner eventually, I don’t see why anybody should object to the FAA insisting on a fuel inerting system. Especially on new airliners since they can design in the system at mimimal cost compared to a retrofit. Also, a 7 year notice period is hardly draconian and merely reflects the rarity of the problem.

[hobie]

Boeing has said it will use inerting technology in its new 7E7, which is still being designed.

This does tend to support the view that the concept is valid :confused:

[GlueBall]

CaptainSandL ...good research compilation. :ok:

[WindSheer]

I have read endlessly on the TWA800, and I have no doubt in my mind that this was a huge military 'cock-up' leading to the downing of a 747 and countless innocent lives.

Concorde was removed from service days after the paris crash due to a freak sequence of events. 747's still litter our skies, harnessing this apparently lethal fault. Its all nonsense.

While I agree there is a definate 'issue' with centre tanks, they certainly shouldn't be linked IN ANY WAY to the TWA incident because the aircraft was shot down. As the yanks say, PERIOD!

:suspect:

[Few Cloudy]

Seems to be on - or after a spell on - the ground, that this type of explosion has occurred. Maybe there wasn't a spark at all.

After the tank empties in flight there is much less chance of an environmental overheat (although I did collect a HP Victor from a check in St Athan once and had blisters on the bomb bay tank afterwards from a loose hot air duct...)

Why not then start with a ground based system to fill intentionally empty tanks with nitrogen after landing?

This could involve a nitrogen truck and the mod would be addition of a (Schrader) valve and a bit of tubing to the tank. In this way much of the engineering work and costs might be saved.

[Frangible]

Well said FC. The need to replenish the nitrogen once into flight may be obviated by the lower environmental temperatures. And there's no weight penalty to a ground-based system.

Separately, consider that inerting could be a useful protection against the remote possibility of being hit by a MANPAD. The DHL over Baghdad took the warhead in a full tank. Had it been half full, it might well have gone up.

[DingerX]

Ugh, conspiracy theories again.

Someone mentioned comparing the fuses of TWA800 with a "DC 9 that crashed in the mediterranean". (Itavia, perhaps?)

There's a lot more compelling evidence for that DC-9 being shot down then there is for TWA 800; and even so, I doubt we'll ever conclusively know the answer in the Ustica case.

When that Itavia flight went down, the official statement that it was a bomb was released very quickly, in the days following the accident, and three weeks before the news broke of the Libyan MiG-21 wreckage in Calabria (which occurred sometime before).

When TWA 800 went down, the investigating authorities were very slow to release their findings; yet days after the event, the news that the center tank was on fumes and 50-60 degrees C was included (without hypothesis) in the journalist's reports.

Missiles do knock down airliners, and we have plenty of cases where they do, including missiles fired by the US. The evidence for TWA 800 is just weak; on the other hand, a fuel tank explosion, given the conditions, makes a lot of sense: sure it's a rare event, but thank God we don't have common events bringing down planes very much.

Comparing the Concorde to these things is ridiculous, given the very rare usage of the concorde. Given the rate of failures, if the concorde were as common as the 737 (with its miysterious rudder issues), then several times a week they'd be suffering damage from tire blowouts, including fuel leaks. And once a month there'd be a horrible crash.

Most big explosions happen in Hollywood. Fuel tanks are only at risk for catastrophic explosions when the quantity of fuel remaining (and the heat) is such to create an ideal fuel-air mixture for a spark to set off. A cheap way to remove the oxygen from those tanks is a good thing, even if it's a remote possibility.

Oh and the Swissair MD-11 fire pretty much killed MD-11 production.

[wsherif1]

The TWA 800 accident actual cause!

There were No missiles and No bombs! The Center Wing Fuel Tank Explosion was not the initial cause of the accident!

TWA 800 encountered a strong aircraft wake vortex at 20:31:12! (Radar evidence and Boston Air Traffic Control's communication to the preceding aircraft, proves the existence of the aircraft traffic!

A 13.5 foot section of the keel beam was torn out of the aircraft's structure, along with the two air conditioning machines, and the first two bulkheads of the center wing fuel tank! These items, along with others, fell into the "Red" debris zone. No items in the "Red" zone exhibited any soot, smoke, or explosive damage!

The Flight Data Recorder (FDR) continued to record until 20:31:20 at which time the FDR and both cockpit clocks stop! The time of the actual explosion, eight seconds after the initial break-up of the structure!

There was a completely stable air mass that evening, the ocean was as calm as a mill pond, (first clue!) In these weather conditions there is little or no dissipation of the preceding aircraft's vortices, or the fuel vapors exiting from TWA 800's wing tip vents!

At the time of the explosion the wing tip vent fuel was ignited and these instantaneous flame fronts streaked down the aircraft's flight path towards the ground! Thus, the eye witness reports of, "missile trails"!

I have copies of both the original and the NTSB modified FDR charts, which I have enlarged to show the radical deviations in all systems at 20:31:12, the NTSB's "End of Data" line, which is the time of the initial aircraft turbulence encounter!

The NTSB claim that the continuation of the FDR chart is from another AA flight is not correct. There is no three inch tape separation to indicate two different flight recordings! The TWA 800 FDR tape is continuous!

If this accident's real cause had not been covered up, the AA 587 accident may not have occurred! (An increase in aircraft separation standards would probably have been ordered.)..

This accident should alert the "industry" to the high inertia problem involving large, massive, aircraft structures, i.e., the Boeing 747 and now the Airbus 380!

[zerozero]

The only difference in how I feel about this subject is that one year ago I didn't fly the 747-200.

This year I'm qualified on the 747-200 and while I realize that doesn't make me an expert on her systems I can honestly say that I've received instruction from and fly regularly with guys who have been flying this airplane for 30 years--some are ex-military--and even they think TWA 800 was brought down by something besides a fuel tank explosion.

How's that for a run-on sentence? No time to edit right now.

I don't believe I've ever advanced a terrorist or military theory. It could've been either (or both?!). I'm just saying I don't believe there to be a design flaw in the fuel system.

A design flaw *will* repeat itself given time and cycles. The 747 has both.

It's a fantastic design.

[WindSheer]

I thoroughly agree.

I would like to know how many cycles the worlds inventory of 747-200's have done. If it had been a design flaw it would have happened again, and possibly again and again.

I have got my theory of the aircraft being 'un-intendidly' <---- is that even a word :p , shot down due to the governments behaviour the months after the accident.
Evidence went missing at crucial times etc, there was a massive cover up probably resulting in huge pay offs and secrecy contracts etc.

As I said that is only my humble opinion, the actual cause may differ, but it certainly wasn't fuel!

[moggiee]

For the conspiracy theorists - think about this.

SAMs very rarely cause an aeroplane to explode into lots of little bits the way that TWA 800 did. The typical SAM (or indeed air to air missile) relies upon a proximity fuse and warhead fragmentation and schrapnel to slice off big chunks of the airframe, causing the aeroplane (or what is left of it) to fall out of the sky. The result is that the debris is generally found to be in large pieces.

TWA 800 disintegrated in lots of little bits - the debris being much more compatible with an on-board rather than external explosion. So unless a bomb was on board the aeroplane then it was some part of the aeroplane itself (i.e. centre fuel tank pumps and associated vapour) which caused the explosion in the first place.

[Flight Safety]

The technology used the create these new onboard nitrogen inerting systems is Hollow Fiber Membrane technology.

Here's a link to an explanation of this technology.

IGS Generon System (http://www.igs-global.com/generon/technology.htm)

With all of the discussion of missiles and terrorism in this thread, no one has mentioned that this technology makes airliners safer in today's higher threat environments. The US military has been using nitrogen inerting in aircraft since WWII, to help prevent fires and explosions when fuel tanks are hit.

Here's a link to an FAA article on this technology:

FAA Fuel tank inerting (http://www.faa.gov/newsroom/factsheets/2003/factsheets_030729.htm)

Here's a quote from this article that illustrates the protection offered to an aircarft that's being fired upon:

What is a fuel tank inerting system?

An inerting system replaces the oxygen in the fuel tank with an inert gas such as nitrogen, preventing the potential ignition of fuel vapor.

Inerting systems have been used on military aircraft since World War II. Until now, inerting of the fuel tanks has been used to minimize combat explosions and battle damage. On high-speed airplanes such as the XB-70, an inerting system was used to prevent ignition of the fuel due to the heating effects of supersonic speeds.

Many different techniques have been used in the inerting systems on military aircraft. On World War II-era airplanes, engine exhaust was typically used to produce the inert gas. More recently, nitrogen has been used to render the fuel tank inert. Various techniques exist for separating nitrogen from air for use in inerting, the simplest and most reliable being the membrane technology that is used in the FAA-developed inerting system prototype.
This technology is a good thing, both to prevent future fuel tank explosions, and to help you survive if someone fires on your aircraft.

[WindSheer]

Hmmmmmmm Clever point!!


Has this been brought in to prevent fuel tank explosions OR to help towards preventing another 747 being blown out of the sky.


Hmmmmmmmmm:p

[ZQA297/30]

"Has this been brought in to prevent fuel tank explosions OR to help towards preventing another 747 being blown out of the sky."

Would that be accidentally or intentionally, then? :hmm:

[Ignition Override]

There is much enlightening info on this topic.

A certain book written about the TWA tragedy referred:
1) to the 'fact' that the FBI (for the first time after an aircraft accident?) rode on the first boats which took law enforcement people to the crash location.

2) that the debris was tightly sealed in a building with unusually high security to prevent access. All accident investigations require some security-but this much?

3) that some sort of missile (propellant?) residue was found on some cabin seats or other debris.

Is any of this true, or none of it true? If some of it is, then why the FBI involvement and such high security, unless a terrorist group secretly claimed to have done it, or a military missile somehow tracked the plane and had the range to hit it? Maybe a missile impact would have produced different damage, but there are so many bizarre facts connected with this case. Even an AF Reserve helicopter pilot with a squadron on Long Island claimed to have seen a missile streak towards the 747. He was interviewed by the media, but he seems to have said nothing after the initial appearance. Is any of the true? I have no idea if there really was some sort of conspiracy (clearly this happens only in the US...let's forget the charges made "over there" or "over here" about Diana's death in the Paris tunnel....), but whether any such proof could ever be released to the media, is very unlikely.

About nitrogen inerting in fuel tanks, there was one known such fatal accident among tens of thousands of flights aboard US-built aircraft per year. How would the FAA's almost secret, safety "cost/benefit" analysis see such a modest loss of life as justification for the huge expense, unless it is a huge attempt (by more than the FAA alone) to keep public/media attention from focusing on any OTHER cause? To divert public attention c o u l d be the main priority here. To hit two birds with one stone, attention can be diverted while time goes by and the public forgets about nitrogen inerting thingies, which might cost airlines nothing. It might only cost the US airlines money.

Anyway, with politics and foreign relations always the highest priority, which even help determine which foreign airlines are deemed safe enough to fly into the US (create the correct paperwork and don't seriously insult the State Department in certain contexts), the administrators might not want to push any bankrupt airline over the edge; these top administrators are all political appointees, as are the heads of the DOT, FBI and Justice Departments etc. The FAA once had a former Thunderbird pilot as the man "in-charge" (:cool: ), to put it very loosely.

[lomapaseo]

wsherif1

Deja blew

again

more of the same old

nothing new under the sun

[UNCTUOUS]

As Dagger Dirk pointed out back on page two of this thread, the FAA, sometime in the latter half of 2004, resiled from any inert gas solution for tank flammability - at least for a number of years to come.

My question is: "Does anybody have a reference to that delay (preferably an FAA online document or alternatively a news article covering that delay and the other program that were to be delayed due to economic astringencies)????

UNC

[GlueBall]

I'm a Boeing driver but I am no fan of Boeing center tank design. As mentioned earlier, besides the TW800 center tank explosion, there are two well documented B737 center tank explosions.

The Boeing center tank design flaw is that the center tank pumps are inside the center tank. Because the center tank fuel is used before the main tank fuel there is always the chance of having the center tank pump(s) still running long after the tank is empty. When pumps run dry they overheat. Automatic shutoff switching or thermal overheat cut-off switching can be faulty.

The superlative center tank pump design dates back to the mid 50s when the DC8 was designed. The visionary Mr. Douglas had positioned the center tank fuel pump inside the adjacent main tank, a fail safe design that provides continuous cooling in case the pump doesn't get shut off when the center tank goes dry.

Repositioning Boeing center tank fuel pumps into an adjacent main tank would preclude the greatest volatility of center tank explosions.

:ooh: :ooh: :ooh:

[Ignition Override]

Good points Glueball:

Were the pumps in certain fuselage tanks in the KC-135 (etc) very similar to any civilian center tank pumps?

The mechanic who recently worked on our plane at a small airport had worked on some -135s at Elmendorf AFB, in Anchorage, Alaska. He told us recently that many years ago, he warned a pilot to keep the fuselage pumps off, unless a little fuel was still indicated on the gauges, to prevent overheating, and when the pilot saw that the mechanic had turned the pump (s) off, the aircraft commander quickly switched the pumps back on. The fact that the mechanic/engineer was enlisted might have been a factor. We know how certain officers will prefer to disregard an experienced enlisted man's advice...

The same pilot later died, along with the rest of his airborne crew (of course) when, as Aircraft Commander (maybe such a decision was made only to demonstrate his authority?), he operated those pump long after the tank was dry, the pumps overheated and exploded debris ignited fumes or whatever else was nearby. I can't remember if he said whether the -135's aircraft "Dash One" pilot manual had cautions or warnings about such pump(s).

This is not to suggest that anything like this happened to the TWA 747. On the contrary, are any of the other allegations, about the FBI, the unusually high level of security for the debris or the missile residue true??

:confused:

[lomapaseo]

Repositioning Boeing center tank fuel pumps into an adjacent main tank would preclude the greatest volatility of center tank explosions.


I have no idea what is being claimed here.

What do the fuel pumps have to do with volatility.?

Anybody willing to translate this into engineering terms.

[GlueBall]

Yes, lomapaseo: No need to get into engineering minutea about "spontaneous combustion." It is self evident, for example, that if one puts a piece of paper on something that gets very hot (but doesn't glow or burn), like maybe on a hot brake...and you'll see that the paper will burn without a flame or spark. Another example would be like a diesel engine ...which has compression and combustion without the benefit of ignition (spark plugs)...you know a little about pressure and heat, don't you?

If you read a little about the Thai Airways B734 center tank explosion you'll learn that the center tank pump was running dry, for whatever reason, whether it was a faulty thermal cut-off switch, or whether it was a faulty flow control switch...the end result was that the pump got so hot and either caused a spontaneous fuel-air-vapor combustion, or caused insulation on electrical connectors or wiring to become frayed from excessive heat which may have generated a spark...

The facts are that Boeing has a history of center fuel tank explosions...and Douglas doesn't. Thirty five year old DC8s today are still plowing the skies ...with 35-year-old fuel tank wires and no fuel tank explosions. Additionally, Douglas uses "feed box" design which keep main tank pumps, positioned inside the feed boxes, always fully submerged and primed.

Positioning center fuel tank pumps inside adjacent main tanks is a variation of fail safe fuel system design philosophy.

:eek: :eek: :eek:

[jettison valve]

GlueBall,

Partially agreed; dry running of pumps is not a clever idea.

But: You can also prevent dry running of pumps when they are located inside a transfer/reserve tank. Routing of the attached plumbing is the trick.
Furthermore, you can build pumps and the pump canisters explosion proof. Today´s pumps can run dry extensively, and you can even throw tons of debris into them - you won´t see an ignition source. Yet, if there would be one, flame traps would prevent propagation.
Finally, thermal fuses are installed to prevent overheating of the pump.
I probably forgot some devices; nevertheless: Future fuel systems should be pretty safe!

Cheers,
J.V.

[Flight Safety]

The FAA has recently concluded flight tests on both an A320 and a NASA 747, of a simplified OBIGGS system for fuel tank inerting. The following FAA .pdf reports discuss the OBIGGS system design used on each aircraft, flight test parameters, and test results. They are interesting reading for anyone interested in the current state-of-the-art in on-board nitrogen gas generation fuel tank inerting systems.

Airbus A320 flight test results - June 2004 - 1.25MB (http://www.fire.tc.faa.gov/pdf/03-58.pdf)

NASA 747-100 flight test results - December 2004 - 8.8MB (http://www.fire.tc.faa.gov/pdf/04-41.pdf)

[jettison valve]

Flight Safety,

Yep, and they have just issued Special Conditions for a 747 Flammability Reduction System:

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgSC.nsf/0//126825FD59C6DD1B86256FA900619F1C?OpenDocument

Thanks for the links!

Cheers,
J.V.

[Flight Safety]

I read somewhere that the simplified OBIGGS used for the 747 test weighed in at about 100 pounds, and would be lighter for smaller aircraft. That's not bad.

The only real issue I see from the flight tests, is a noted degradation in the performance of the ASMs (Air Separation Modules - contained the hollow fiber membranes) that accumulates with usage time. The cause is not know yet, and could effect the long term performance of these systems. It is known that hydrocarbons and HFMs don't react well together, and particulate matter tends to clog the HFM, so maybe these are the causes.

[Frangible]

The only conspiracy theory worth commenting on concerns Ustica (Moderators: can't you find a separate home for TWA800 conspiracy theorists?). The Itavia DC-9 was, as near as could be scientifically determined, broke up in flight after a bomb blew up in the toilet. That was the near-certain conclusion (near only because he is an appropriately conservative investigator) of Frank Taylor, recently retired head of Cranfield Aviation Safety Institute in a highly detailed report several years ago commissioned by the Italian investigating magistrates and published in a past issue of the journal of the International Society of Air Safety Investigators.

[barit1]

Earlier posts mention estimated compliance costs for the new system.

Methinks the astute beancounter will be looking for savings, not costs. For example, there should be a measurable savings in hull and liability insurance cost, once the inerting system is mature enough to save an airplane every few years.

It's usually too easy to point to costs, without considering the flipside.

[lomapaseo]

Earlier posts mention estimated compliance costs for the new system.

Methinks the astute beancounter will be looking for savings, not costs. For example, there should be a measurable savings in hull and liability insurance cost, once the inerting system is mature enough to save an airplane every few years.

It's usually too easy to point to costs, without considering the flipside.

In the scheme of things I don't believe the insurrance carrieres care a twit about reducing premiums for so little reduction in risk to their bottom line. They have a tendancy to look at the worldwide overall risk to themselves for all carriers and all transport types.

After that you may argue about the saving of one B747 in some many years (is it 1 out of 20 yrs? and maybe argue for 10% of this as kickback insuree credit spread out over all operators of the type.

extremely insignificant compared to the costs of the retrofit.