self sealing gas tanks

[renrich]

The F4U1 had wing tanks that were not selfsealing as the fuselage tank was. There was a CO2 bottle in the cockpit, unfortunately next to the CO2 bottle used to blow down the landing gear in an emergency. When going into combat the pilot could use the gas tank CO2 bottle to purge the wing tanks of gasoline and fumes. I say unfortunately because one Navy pilot when going into combat, chose the wrong bottle and blew down his gear thus leaving him a sitting duck and resulting in his demise. Admiral Connolly jumped all over Boone Guyton about this design deficiency and one of the bottles was moved to a new location.

[Marshall_Stack]

I read that the last version of the mighty Brewster Buffalo had the same feature (Co2 to purge the wing tanks).

[Cub Driver]

The USA had the huge benefit of being able to learn from the European battles before December 1941 and they were by no means common in the USA at that time.

Here's the experience of Curtiss-Wright: the plain vanilla P-40 (what ought to have been called P-40A) was without self-sealing tanks. Export models were sold to France, and Britain took these over as the Tomahawk I. The RAF asked for self-sealing tanks and two more thirty-caliber guns in the wings. Curtiss built these and Britain adopted them as the Tomahawk II, later called IIA. This was in the fall and early winter of 1940. Curtiss built essentially the same airplane for the U.S. Army as the P-40B.

These tanks has an exterior rubber membrane. An interior membrane was more effective, and Curtiss put this airplane into construction in the early months of 1941. To the RAF, this was the Tomahawk IIB. With a few modifications (notably a bracket for a centerline fuel tank) the same plane became the P-40C. (Tomahawk IIBs were also supplied to China for the American Volunteer Group, though apparently Curtiss retrofitted them with P-40B-type fuel tanks, and there were other anomalies.)

I'd always assumed that the rubber simply closed over the bullet hole by mechanical action, but more recently I've been told that there was a chemical reaction with the gasoline, causing the membrane actually to swell. In any event, an interior membrane was more effective than an exterior one, though it cut down on the gasoline the plane could carry (160 US gallons in the P-40B, 135 gallons in the P-40C).

First delivery of the Tomahawk IIA was October 1940. However, these planes weren't used in the BoB, and in the end all RAF Tomahawks went to North Africa or were seconded to Russia (and China!).

Blue skies! -- Dan Ford

Coming August 21: Flying Tigers: Claire Chennault and His American Volunteers, 1941-1942

[HoHun]

Hi Renrich,

>When did British and German ac start using self sealing gas tanks?

On German self-sealing tanks, you can find pages of interesting information here:

http://www.ww2aircraft.net/forum/oth...ysis-6399.html

(File Me 110 part 1, page 90 and following.)

In short, Vultee analyzed a captured Me 110 and found that the self-sealing tanks were of limited use, not as good as "current" US tanks but as good as US tanks of the same period (1939/1940). The installation of the tanks was considered superior to US installations as it was designed to reduce sparking, shrapnel generation and hydrostatic shock as far as possible (and facilitating maintenance at the same time).

12.7 mm bullets were considerably more effective than rifle calibre bullets in causing leaks, though the self-sealing capabilities only closed one half to two-thirds of the leaks caused by rifle-calibre fire in the test. (Against 12.7 mm, I'd say the tanks were only marginally effective.)

The Vultee article credits the Germans with being the first to introduce self-sealing tanks, but as this is wartime information, it might be inaccurate. The fuel tanks on the Me 110 are stamped May 1940, but I imagine that it might be possible to find out the aircraft's Werk-Nr., which usually enables the experts to deduce its production date. (I'd say from the description of the installation, the self-sealing tanks are unlikely to be a retrofit, so the production date would be good data for our timeline.)

Regards,

Henning (HoHun)

[JoeB]

Originally Posted by renrich

The F4U1 had wing tanks that were not selfsealing as the fuselage tank was. There was a CO2 bottle in the cockpit, unfortunately next to the CO2 bottle used to blow down the landing gear in an emergency. When going into combat the pilot could use the gas tank CO2 bottle to purge the wing tanks of gasoline and fumes.

I've read that some Corsairs also had an exhaust gas inerting system, exhaust gas rich in CO2 (but mostly inert nitrogen, just like the intake air), recirulated to the fuel tanks. Soviet Lavochkin fighters definitely featured such a system, and I half remember mention of the same system in late P-51D's, from a pilot's manual I used to have (but don't have now, could be misrecalling that). It's essentially what modern oil tankers do to ensure a non-explosive atmosphere in their cargo tanks in all phases of operation.

Bottled gas systems have also been used in a/c for tank inerting, regulators having been going back and forth on a rule that all airliners have this since the TWA Flight 800 disaster, apparently from an explosive atmosphere in a fuel tank and source of spark from malfunctioning deepwell pump. US carriers had similar systems, using CO2, even at the beginning of WWII.

The problems with tank inerting to protect against fire from combat damage are two 1) in many circumstances the fuel mixture in the tank is too rich to support combustion, so the system is overkill as far an explosion strictly inside the tank but 2) the systems don't help that much once the gas gets outside the tank from a hole shot in it, and either forms an explosive mixture within a wing or fuselage structure, or just destroys the plane by fire. Therefore self sealing systems to try to prevent tank leakage, were more to the point.

However USN figures for period Sep '44-Aug '45, with great majority of tanks in combat self sealing, were that only 11% of a/c hit in the fuel system recovered safely. Self sealing tanks seemed to mainly benefit pilot rather than plane survival.

Joe

[FLYBOYJ]

Originally Posted by JoeB

Bottled gas systems have also been used in a/c for tank inerting, regulators having been going back and forth on a rule that all airliners have this since the TWA Flight 800 disaster, apparently from an explosive atmosphere in a fuel tank and source of spark from malfunctioning deepwell pump. US carriers had similar systems, using CO2, even at the beginning of WWII.

The only system as such I ever heard of is a portion of cooled bleed air being ducted back to the fuel tanks to keep "head pressure" on the fuel within the tanks not only ensuring a positive flow from the tanks but reducing fumes. Mind you this system is on turbine aircraft or turbo props. I did work on P2Vs very briefly and don't recall any type of fuel tank purge on that aircraft, but then again all we did was get it ready for a ferry flight.

As far as inert gasses being used in current airlines, I don't think its happening except for newer airliners. (Mind you I've been out of Heavy aircraft maintenance for about 4 years now). I do know that the C-5 and the C-17 has such as system, but some of the airliners and larger military aircraft I've worked on (DC-9, 10, B727, P-3 and C-130) did not have such a system (or at least to my memory).

[Kurfürst]

This is the fuel tank of the 109E, originally posted by George Hopp.

I am not expert on this but it looks like to me as being made of rubber, and given the 110's case shown by HoHun above, I suppose it's a self sealing one, too.

Unfortunately, contemporary reports of the 109E do not address the question of protection much, what is clear is that the aircraft had armor plating behind it's fuel tanks in the fuselage (which also provided protection for the pilot).

[renrich]

Self sealing tanks besides reducing fuel carried also added a good deal of weight, one reason the F4F4 weighed considerably more than the early F4F3s w/o self sealing tanks.

[FLYBOYJ]

When I worked for Flight Systems, we were droning F-4s. Some of the aircraft droned had a self sealing tanks that had a "foam" within the tank. One of the things we had to do was remove this stuff. If my memory serves me right it was mainly on the RF-4s. The mechanics who had to do this job hated it...

[Sgt. Pappy]

If I manage to get some tickets for the bus tomorrow, I'll be sure to get my arse into the museum at which I work. It's my day off but being a Spitfire finatic, I'm going to check the History of Spitfire production, modifications and serial numbers manual.... HUGE book... over 700 pgs with 15" x 12" size, size 10 font

From what I know, the only Spitfire I's that had self-sealing tanks had only the lower tank sealed and not all of them had it. Spitfire V's, you must remember, were often only modified in that they carried the new engine and its accommodations (i.e. larger oil cooler). The bottom tank was sealed like on the I and II. Not sure about the IX.

[pbfoot]

I tried every book on the spit we had at Russells and the best info was the original I tried to look at it but the panels covering the fuel tank were on so I had no joy you can see what I mean

[mad_max]

Pappy,

I think your on to something about the top tank. If I remember I read about that tank causing
many badly burned pilots. It was right in front of the bulkhead behind the instrument
panel and fumes and of course flames would blow back into the cockpit.

Of course I maybe quite wrong also!

[HoHun]

Hi Joe,

>I've read that some Corsairs also had an exhaust gas inerting system, exhaust gas rich in CO2 (but mostly inert nitrogen, just like the intake air), recirulated to the fuel tanks.

This link mentions CO2 fire suppression system as well as the retro-fitting of self-sealing liners in Japanese H6K flying boats:

Lt. Tsuneo Hitsuji*- Shootout Between H6K5 Mavis and B-17

Regards,

Henning (HoHun)

[HoHun]

Hi again,

>(As so often, McIndoe worked wonders in the treatment of the author of "Guinea Pigs". Wish I'd remember the name - unfortunately, I have mislaid the book. It really made a deep impression on me.)

I just found the book - it's "Tale of a Guinea Pig" by Geoffrey Page.

Regards,

Henning (HoHun)