US unveils new rule on airplane fuel tanks

[Mark in CA]

I can't help wondering why this took so long (12 years almost to the day):

US unveils new rule on airplane fuel tanks - Yahoo! News (http://news.yahoo.com/s/ap/20080716/ap_on_go_ot/air_safety_fuel_tanks_7)

A device to prevent airplane fuel tanks from exploding must be installed on certain passenger jets and cargo planes. The new safety requirement applies to new passenger and cargo planes that have center wing fuel tanks. The rule also requires airlines to retrofit 2,730 existing Airbus and Boeing passenger planes over the next nine years with center wing fuel tanks with the changes. The retrofit schedule is based on the normal aircraft maintenance schedule.

[Tweetair]

About time but who will pay for it?As airlines face troubling times it is another cost they can ill afford.Aircraft have been flying safely without the mod so why do we need it?

[DC-8]

New 737's are being delivered with this system already installed. You may see it in the main wheel well, but it's still inop.

[Buzz Control]

This posted on Aviation Herald: News: Nitrogen to replace oxygen in center fuel tanks (http://avherald.com/h?article=409bf9a7&opt=0)

Nitrogen to replace oxygen in center fuel tanks
By Simon Hradecky, created Wednesday, Jul 16th 2008 19:20Z, last updated Wednesday, Jul 16th 2008 19:23Z
The US Department of Transport introduced a new rule today, that requires new airliners with center fuel tanks to be equipped with a system within two years, that replaces oxygen with nitrogen in the center fuel tanks. The rule also applies to all 2730 aircraft with center tanks already in operation, which need to be retrofitted with the system within 9 years.

This regulation was recommended by the National Transportation Safety Board NTSB as result of the investigation into the crash of flight TWA800, which had crashed before the coast of Long Island on July 17th 1996 following an explosion in the center fuel tank.

The regulation was opposed by the aviation industry claiming, the modifications required were too costly.

NTSB Chairman Mark Rosenker said: "The NTSB congratulates the DOT and the FAA on this important safety achievement. From tragedy we draw knowledge to improve safety and today's announcement represents a significant step toward avoiding future aviation accidents of this nature."

:ouch: My other question is.... Is this applicable to just centre fuel tanks or all fuel tanks???

[stadedelafougere]

Sooner or later it will have to be applied to all fuel tanks...

The following doc may bring interesting answers to the question: is it worth paying billions of dollars for a few lives saved per year?

http://www.fire.tc.faa.gov/pdf/99-73.pdf

[peter we]

About time but who will pay for it?As airlines face troubling times it is another cost they can ill afford.Aircraft have been flying safely without the mod so why do we need it?

The airlines will pay for it, they have avoided having to pay for it before and times is up, no more excuses. You would expect any aircraft bought in the last 12 years to have it installed already.

Haven't military aircraft had this for decades?

[56P]

The reason for the delay is that many are aware that the loss of TWA 800 was NOT caused by a CFT explosion.

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ARAP E-Mail on Tank Explosions

To whom it may concern,

At 1:00pmET today, the Discovery Channel presented its TWA800 "documentary". As a manufacturer of UL Listed steel fuel tanks, I was disturbed by the presentation of a "scientific test" which demonstrated that a Boeing 737 fuel tank under "similar conditions" would indeed explode if a spark were introduced to the tank. I am therefore compelled to write in the hope that someone with a vested interest might read this.
I sense serious defects with the test as presented. As a manufacturer of steel fuel tanks for both fuel oil and gasoline use, there are several basic axioms which guide our designs.* One basic tenet is that a properly designed and vented fuel tank will not explode, even when engulfed in fire. The issue with a fuel tank is not explosion-- it is rupture from overpressure from gases produced by boiling liquid. Provided that the tank is vented, it will not rupture. We don't worry about explosion as much as tank rupture from overpressure or tank structural failure from heat. Most important, however, is that a fuel tank fully engulfed will not explode because there is no oxygen in the tank. All of the "air" has been displaced by heavier-than-air fuel vapors. Remember that these tanks are vented-- these are not pressure vessels. So the residual fuel that would always be present in the tank would give-off vapors which displace the air out the vent. The Boeing 747 fuel tank in question had not been emptied. Presumably it had been quiescent on the ground for many hours prior to flight. The fuel tank should therefore have been fully saturated in fuel such that all "air" had been displaced. Furthermore, as the aircraft climbed, and pressure dropped, the tank would have further evacuated-- fresh air would not have been drawn into the vented tank until the aircraft descended. As air pressure dropped, so would the boiling point, resulting in a greater concentration of vapors and displacement of oxygen. Therefore, a spark or even an open flame could not have ignited the vapors.

Perhaps this explains why aircraft fuel tanks are not exploding all the time-- and car fuel tanks as well. In fact, TWA800 is the only aviation case I have knowledge of and I am an interested person who follows these things (I am a private pilot with a life-long aviation passion).

The Discovery Channel presentation is defective:
1. The test tank was freshly filled and immediately tested, not allowing time for the atmosphere within the tank to saturate with vapors as would have been the case with the TWA800 aircraft.
2. The test tank had air circulation fans installed within, which would have both inhibited evacuation of air and introduced fuel droplets into the air. The 747 had no such mixing fans.
3. The test tank was tested at atmospheric pressure. The TWA800 event occurred at 15,000 feet or so, where pressure is greatly reduced.
4. The test tank was artificially heated by a salamander perhaps producing spot overheating. The TWA tank would have been both at uniform temperature and would have cooled substantially during the climb.
Furthermore, the flash point of Jet-A is well above 100F. The test was performed at approx 125F, presumably below the flash point of Jet-A. A flammable liquid can only ignite in free air when the flash point is exceeded. Artificially introduced droplets were probably introduced in the test. In fact, the test appears to be so defective as to be contrived such that the test tank was indeed a "bomb" producing desired results.

I am disturbed that this is presented to the gullible public as fact and the final word. I believe that the facts of metallic tank construction weigh strongly against the "results of the scientific test" presented on Discovery. Those of us who manufacture steel fuel tanks know this.

I have no political ax to grind and am not a conspiracy nut. However, as an engineer, a pilot, a person of knowledge and a manufacturer of fuel tanks, I have severe doubts that the TWA800 tank exploded from an internally introduced spark. The reasons presented above substantiate those doubts.

I hope that this letter will help advance your search for the truth.

Thomas Debrey, President
Simplex, Inc.

[Carnage Matey!]

The reason for the delay is that many are aware that the loss of TWA 800 was NOT caused by a CFT explosion

Of course it wasn't. It was shot down by aliens who then bumped off Princess Di who was the only witness.:rolleyes:

[Piltdown Man]

56P: Thank you for posting. Regularly we have to hop through a hoop because it is decreed by our governments. Here is a typical case. Too often they go in a particluar direction because they are led by those with vested interests. Unfortunately our "leaders" do not listen to those with a contradictory view and merely dismiss them as un-informed and/or ignorant. It's good to hear from someone who "knows nothing".

PM

[RadarMaggot]

The only fact is that someone is going to make a :mad:load of money off this new system...

[Hunter58]

CM

Interesting speculation. About as interesing and realistic as the fuel tank explosion theory itself.

(Just wondering howcome a center fuel tank explosion would shear off the forward part of the aircraft when the minimum resistance part for doing that was the main wingspar while a 'simple' section 41 related structural failure would have had similar effects without having to question of how the main spar would have blown out and nothing else)

[Fool 'n' Tameez]

For an industry that emphasizes the importance of safety, the level of resistance to this is dissapointing. All very well FUDing the findings of the TWA accident, which occurred out to sea with parts mangled and hard to come by, but how about the Thai 737 whose centre tank exploded on the ground a few years later? Very little doubt to what happened there.

[lomapaseo]

For an industry that emphasizes the importance of safety, the level of resistance to this is dissapointing. All very well FUDing the findings of the TWA accident, which occurred out to sea with parts mangled and hard to come by, but how about the Thai 737 whose centre tank exploded on the ground a few years later? Very little doubt to what happened there.

Be careful of including the psychic theories and so called fuding the findings under the guise of the "industry"

The so called industry consists of the regulators, the manufacturers/designers and the operators To my knowledge they have not filed objections to the factual findings of the investigation. However the recommendations go beyond the factual findings and presume a level of risk for future operations to justify the implementaion of an imperfect control to this risk. As in all safety related control actions there must be a balance between meaningful gains in safety (lowering of risk) against the amount of resources that are to be expended to gain this advantage.

for example ask what other higher risk safety items (like enhanced GPWS) may not be given a comparitive amount of resources

[NVpilot]

I am disturbed that this is presented to the gullible public as fact and the final word. I believe that the facts of metallic tank construction weigh strongly against the "results of the scientific test" presented on Discovery. Those of us who manufacture steel fuel tanks know thisOf no surprise to anyone that looks into the rest of the TWA 800 investigation, some choose to keep their heads buried in the sand. :ugh:

[contractor25]

Your statements do make a lot of sense, however in training courses now mandatory in Europe for aircraft maintainance personnel (SFAR88), the suggestion is made that the main cause of the TWA800 story is the heat coming of the aircon packs located directly below the centre fuel tank. the tank had only unusable fuel in it, given the size of the centre tank it is doubtful the remaining fuel would have created enough vapour to evacute the tank completly of oxygen.
A spark arced across chafed wiring further downstream the wiringloom, which then lead into the fueltank via the fuelquantity wiring.

[Flash2001]

Interesting post by Mr. Debrey. He obviously knows what he is talking about. Yet it seems there was a low order explosion in the centre wing tank. Could someone who knows that aircraft's fuel system say if there is more than one vent to that tank? If there was, then any air movement, wind etc. might replace the saturated vapour in the tank with air thus leaning the mixture.