OT: Self Sealing Fuel Tanks and other things that keep me up at nite

I assume the rubber lined tanks stopped leaks from AAA, etc. but didn't the hot metal set off the fuel anyway. Just trying to figure out why hot lead and flak did not always set fuel on fire.....

and at 30k feet or so its often 40-50 degrees below zero. At that temp could engines really still overheat? seems like the radials on a B-17 would be easily cooled by that air temp...

thx - Craig

Reply to
Craig
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Plenty of planes with self-sealing tanks blew up when an 88mm shell made a direct hit. At the other end of the spectrum, if a .50 caliber solid round hit a fuel tank that wasn't self-sealing, you could count on gasoline leaking out of the tank, which would allow the volatile vapor to go places it ought not, like the engine compartment. Ka-boom. If that same tank is self-sealing, little or no gas leaks out and the fire/explosion hazard is drastically reduced. Also, fuel retained means the plane is more likely to have enough to get home. Between the 88mm and the .50 cal there is quite a spectrum of heat and mass in the projectiles that might hit a fuel tank. I suspect there were damn few fuel tanks that would reseal after a hit from an MK 108.

Can't say much about engine cooling, except that I wonder if the density of the air has something to do with the rate of cooling. At 30K feet, the air is mighty thin.

Mark Schynert

Reply to
Mark Schynert

It all depends upon the volume of air going past the engine. The cowl flaps regulate how much air gets around and through the cylinders. It should also be remembered that "cool" is a relative term. An engine has an optimal operating temperature; you don't want it to get either too hot or too cold since either condition will cause Bad Things(tm) to happen.

If battle damage either tore off some cowl flaps or jammed them shut, then the engines would not operate properly, and let's not even go near what would happen to a Merlin with a round in the glycol lines...

Reply to
Jeff C

"Mark Schynert" wrote

. . .

An 88mm shell has somewhere between 10 and 15 lbs of high explosive in them. Even if the tanks were bone dry the plane would be destroyed. Aircraft are relatively fragile things. Aircraft guns 20mm and above had explosive projectiles, but I'm not sure if the German 15mm guns did.

KL

Reply to
Kurt Laughlin

Not to mention that at that altitude and over that distance, would a 50 cal round have enough time to cool off by the time it actually impacted it's target? I'd think that that would give rise the to the streaming vapor type detonation that you describe more often than the tank explosion.

That and the possibility that there may not be enough viable fuel/air mixture inside the tank to give rise to a detonation...just guessing...

Reply to
Rufus

Bad Things (tm)...LOVE it!

Reply to
Rufus

I called my Dad. Talk to your fathers they walked this road long before you did. He said self sealing tanks were a blessing in crash landings and 'eddy bitty' pieces of AA shrapnel. A direct hit and in his words "....poop your pants and either watch your past life pass in front of you or enjoy the ride down." Call your Dad up and talk to him before he's gone and that source of information, back up and love is gone forever. Mike IPMS

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Reply to
Mike Keown

Good advice...

Reply to
Rufus

They had explosive rounds down to 7.92x57mm using picric acid as early as the beginning of WWI....these rounds weren't all that popular with any users as they were a might unstable. IIRC they were originally developed as anti-airship rounds, I've long since lost all my old 8mm data on a hard drive that died but this one sticks in my mind.

Certa> An 88mm shell has somewhere between 10 and 15 lbs of high explosive in them.

Reply to
Ron

Zackly!

Ken

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Ken Leonard ken snipped-for-privacy@NOSPAM.earthlink.net [Edit it to make it work.]

Reply to
Ken Leonard

In the Spring of 1918 the Germans introduced an incendiary round for their fighter pilots to use and a number of german pilots were killed when the ammo ignited in their ammo boxes while in flight. It was a problem particular to the Fokker D-7 and it was thought that hot engine gases and the July temperatures caused the unstable ammo to cook off. D-7's were to be seen with all manner of extra holes/vents cut in their cowling panels to alleviate the problem thereafter.

Bill Shuey

Reply to
William H. Shuey

FWIW Back in the 60's the CO of my reserve unit was a former 15th Air Force Bombardier/Navigator on B-24's. He said that they routinely flew with the bomb bay doors "cracked" because they had had aircraft blow up in flight for no apparent reason. They finally figured out that it was gas fumes leaking from their auxiliary bomb bay gas tanks that caused the explosions, this at 24 to 30 thousand feet. Yes, it can happen up there too.

Bill Shuey

Reply to
William H. Shuey

"William H. Shuey" wrote

Incendiary rounds aren't explosive, but more like fusees, matches or the like, ignited by propellant gases. Explosive rounds require an explosive train and preferably a fuzing mechanism. Small caliber projectiles dispense with the fuze and - in most cases - have some sort of percussion device in the nose.

KL

Reply to
Kurt Laughlin

Interesting. Made me recall how JFK's brother was killed when his Liberator exploded in Operation Aphrodite(?). Cause is supposedly unknown. Could this have been a probable cause?

Sean

Reply to
Sean

Yes, but I've also heard it speculated that the arming mechanism for the explosives might have been defective, and that arming the warhead actually set it off. B-24s (especially the C-109 tanker version) were notorious for mid-air fuel vapor explosions, although the bomber version was usually at risk only if it first suffered battle damage.

Mark Schynert

Reply to
Mark Schynert

Craig,

Self-sealing fuel cells were not rubber lined metal tanks. They were fabricated from layers rubber and a chemically treated rubber that reacted with the fuel. The fuel cells were fabricated to be flexible for installation into spaces in the wings, etc. or semi-rigid such as bomb bay auxiliary fuel tanks. Several plys of rubber made up the cell. The inside ply was a fuel resistant rubber. Ameripol was one brand name for this fuel resistant rubber. The sealing compound was in the middle of the outer coat and the inner reinforcing layers. When pierced by bullet, the fuel reacts chemically with the sealing compound causing it to expand and seal the hole. The hole would be sealed for relatively short time. Damage could be so severe that the cell would not seal.

Liquids do not burn. Only vapors burn. Vapors must be mixed with sufficient oxygen to support combustion. A hot fragment entering a fuel cell would be rapidly cooled by the fuel within if fuel is present or the oxygen content of the empty cell may not support combustion. Some aircraft like the F4U-1 and F4U-1A Corsair had integral wing fuel tanks that were non-sealing. A vapor dilution system admitted carbon dioxide gas into the fuel tank "for making the atmosphere above the fuel inert, for protection from gunfire during combat..."

Even at altitude an engine can be overheated depending on how the engine is operated. Many accounts are in print detailing pilot anxiety over cylinder head temperatures and engine failures at altitude.

Don

Craig wrote:

Reply to
Don Fenton

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