Airframe machanics in the House??

[Donny]

I know this has nothing to do with guns, but...

Are there any airframe mechanics in the house?
Does anyone know how airplane fuels cells are built? What type venting/equalization scheme is used on them?
If the tanks are sealed after refueling, how are they kept equalized to keep from imploding as fuel is extracted to the engines?

Best Regards,
Don

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The most foolish mistake we could make would be to allow the subjected people to carry arms; history shows that all conquerers who have allowed their subjected people to carry arms have prepared their own fall.
Adolf Hitler

 

[C.R.Sam]

Don;.....a multitude of construction methods and materiels have been used, and are still being used. Sheet metal tank similar to car, cloth reinforced plastic ( fiberglass et all ), rubberish bags in supporting structure, built as part of wing structure with the seams gooped, etc etc.

Nearly all low altitude applications are vented to atmosphere, higher altitude stuff is often pressurized lightly to avoid fuel boiling off.

If you have specific application in mind, feel free to e me. I spent nearly forty years messin with aircraft, threw a few away, built one, tested some and loved gettin paid for havin fun.

Sam

 

[Dan]

I've spent a fair amount of time inside more than one type of fuel tank. As C.R. stated, there are differing construction methods. It would really be dependant on the type aircraft. Heavy cargo frames have different structural requirements than a light civil aircraft than a tactical rotary wing...

What type of aircraft do you have in mind?

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Dan

Si vis pacem para bellum!

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[Donny]

The reason I was asking about the fuel tanks was the Flight 800 business of several years ago.

I understand the premise of a pressure equalized system, I also understand the dangers of static charge, and ullage in the tanks.
I was under a false belief that the tanks were equalized with an inert gas to eliminate, or greatly reduce, the chances of a flash in the tank.

I remember working on pressurized Avionics because the high-pot systems were prone to arcing and eventual breakdown. It would seem a natural conclusion that the fuel systems be designed with the same considerations.

Best Regards,
Don

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The most foolish mistake we could make would be to allow the subjected people to carry arms; history shows that all conquerers who have allowed their subjected people to carry arms have prepared their own fall.
Adolf Hitler

 

[Jeff, CA]

A Dr. Loeb with the NTSB was one of the main investigators of TWA 800. He also investigated another fuel tank explosion some years ago, and at that time, petitioned the FAA to require empty fuel tanks to be inerted. The FAA did not make inerting mandatory. TWA 800's center fuel tank had not been inerted, and Dr. Loeb has been saying "I told you so".

 

[Dan]

I don't know how you could "inert" an empty fuel tank. That would require a system that would seal the tank from it's venting system and the addition of an inert gas.

Way too complex for a nonexistant problem.

The flt 800 explosion was most probably caused by the combination of a "pin hole" leak in a fuel line and an electrical spark. Both of which would have occured in a dry compartment - that is a non fuel cell compartment. Jet fuel, Jet "A" and its military equivalent JP-5, has a very high flash point and is not flammable unless atomized. Also it is rare that the wiring for an AC electrically powered component (pumps)is in a commercial A/C fuel tank. Usually electrical lines are placed in dry bays adjacent to the fuel cells. Normally, when an electrical short occurs, the circuit breaker for that phase the short occured on will pop. It is standard procedure for the flight crew then to pull the remaining C.B.s for the other 2 phases. Under no circumstances are the crew to reset a popped fuel componenet C.B.

I would guess that one of the fuel lines bearing fuel under pressure developed a pin hole leak, thus spewing atomized fuel into an enclosed dry compartment, was exposed to some sort of spark from an electrical component or even a static dishcarge. This in turn caused the explosion. A tragic fluke.

I guess what I'm trying to say is, I would think the explosion probably occured not in a fuel tank, but in an adjacent dry compartment. Sorry 'bout the rambling and redundant post!

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Dan

Si vis pacem para bellum!

Check me out at:
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[This message has been edited by Dan (edited May 14, 2000).]

 

[George Hill]

Hmmm - for Ultra lights I have used a pair of 2 liter Coke bottles as extended range "drop tanks".

Uh... Outta my legue here... shutting up...