Self sealing fuel tanks

[Red Admiral]

I've always wondered how do self-sealing fuel tanks work?

Could anybody tell me?

[GregP]

[edit] ....

Early attempts involved surrounding the outside of metal tanks with a material that expanded in contact with fuel. This worked, after a fashion, for bullet entry holes but did little to protect against bullet exit holes, which were much larger.

Later, the tanks were made from a soft material that sealed itself when punctured. These tanks were suspended in harnesses so they did not contact the skin, which could have sharp edges when punctured. This cost weight and much-needed fuel volume, and later tanks (after the war)were integral despite the losss of sealing capability.

More modern tanks, such as those on the A-10 Warthog, are protected in several ways, including spraying with fire-retardant foam when punctured, being separated from the fuselage armor, and being near the center of gravity, making it harder to hit.

All self-sealing tanks are self sealing with regard to small leaks. None are self-sealing with regard to "big hits," but the modern ones have fire retardant foam and check valves to shut off fuel to the tank if compromised.

Interesting things, self-sealing tanks ....

[Grifo]

This below is an example of generic sealed tank: on the left there is the bare metal tank, and on the right the same wrapped up by sealing material foil.

http://img.villagephotos.com/p/2005-8/1059285/Serbatoio.jpg

Cheers

[montanamotor]

Grifo, Greg, Red Admiral,

early in WWII, aircraft fueltanks were sealed externally with suede leather against puncture! The USA and other Allies later used kind of internal sealing bladders, made of foam-rubber. These in the beginning had a distinctive - and disturbing - tendency to collapse while fuel was drained from them during flight, ad the bladder's walls later would stick together (vulcanized together by the dilluting (?) effects of gasoline on natural rubber) and hence, the bladder couldn't be refilled to maximum again.

This problem even caused losses in the US-Navy, until it was detected and fixed during a closer examination in 1941. Problem was, that the internal fuel-gauges would indicate the tank being full, while in fact it would contain only a 50 % filling - or less. At one date in mid-1941, 50 percent of all aircraft on board of US-carriers were grounded due to collapsed fuel-bladders in their tanks...

The germans, instead, would keep the exterior suede leather sealing for their aircraft's fueltanks through to VE-day. After this date, this hide was a much sought-after and precious war booty, and many officers rounded up every known german aircraft dump for this tank sealing leather, to have stylish gloves and travelling bags made from this highest-quality, exquisitely tanned leather.

Cheers,

Montanamotor[8D]

[curmudgeon]

quote:Originally posted by montanamotor

Grifo, Greg, Red Admiral,

early in WWII, aircraft fueltanks were sealed externally with suede leather against puncture! The USA and other Allies later used kind of internal sealing bladders, made of foam-rubber. These in the beginning had a distinctive - and disturbing - tendency to collapse while fuel was drained from them during flight, ad the bladder's walls later would stick together (vulcanized together by the dilluting (?) effects of gasoline on natural rubber) and hence, the bladder couldn't be refilled to maximum again.
...

The germans, instead, would keep the exterior suede leather sealing for their aircraft's fueltanks through to VE-day. After this date, this hide was a much sought-after and precious war booty, and many officers rounded up every known german aircraft dump for this tank sealing leather, to have stylish gloves and travelling bags made from this highest-quality, exquisitely tanned leather.


I understood British aircraft used latex/soft rubber in a narrow tank surrounding the fuel tank. The rubber/latex expanded and solidified in response to petrol.

Someone (RV Jones?) commented that the Brits were behind on this because some delightful bean-counter redefined 'self-sealing' to 'crashproof' some time after WW I ... and crashproof was impossible to achieve (you can see the logic - in peacetime aircraft are lost to crashes not to machine gun bullets)