Carbon dioxide (CO₂) fuel tank fire extinguishers for aircraft

[Would you like to see this in-game?]
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Anyone knowledgeable about WWII aircraft has certainly heard of self-sealing fuel tanks. To put it simple, they are rubber tanks, which seal the bullet holes to prevent fuel leaking out in highly flammable aerosol form. As aircraft guns got heavier and more numerous, the self-sealing tanks also had to get sturdier and heavier, but against heavy damage even just wasn’t enough. For that reason Japanese began to use CO₂= carbon dioxide fire extinguishers to better protect their aircraft.

CO₂ fire extinguishing system installed in N1K2-J.

In Japan this appears to have become almost a standard feature for new frontline fighter and bomber variants around mid 1944. In case of certain variants of A6M, D4Y and B6N, it was used as their only fuel tank protection without self-sealing tanks and appears to have been quite lacking alone. Most other aircraft with this system had self-sealing fuel tanks as well and apparently it worked as intended. For example pilots from both sides recognized how N1K2-J and late Ki-61 did not explode if ignited as they could put out the fire very quicky. An intersting exception were Mitsubishi J2M and A7M. Their fuselage tanks had possibly the thickest coating in single seat fighters of their time (30mm), while their wing tanks had no selfsealing protection at all and relied solely on the CO₂ extinguishers.

An Allied report about a captured J2M2. Early on this system was manually operated, but later an automatic thermostat trigger was used instead.

Overall this should be a key component of many Japanese aircraft, just like any other way of protecting the fuel tanks. After all the game makes a clear difference from non self-sealing tanks to self-sealing tanks. Similarly Soviet aircraft have had neutral gas pressurization system from the very beginning of the game. Functionally it would be very much like the engine fire extinguishers already in game and would likely be a researchable modification.

A list of planes which are known to have had this system. Among them are bombers and several prototypes:

Spoiler

A6M5 and all following variants
A7M1, A7M2
N1K1-J, N1K2-J, N1K2-Ja
J2M all variants
J5N1
J6K1
Kikka
D4Y2*
B6N2, B6N2a*
P1Y1
H8K2, H8K3
Ki-67
Ki-61-I Hei and Tei
Ki-61-II Kai
Ki-83
Ki-93
Ki-100-I and -II
Ki-102

*These might have had just engine extinguishers.

For now I have not found mention of these in game fighters having the system, though I would bet they had it as well:

Spoiler

Ki-87
Ki-94-II
Ki-108 (build from Ki-102)
Ki-109 (build from Ki-67)
J7W1

Ki-84 appears to be a notable exception, specially considering how numerous fighter aircraft it was in the late war. One of the documents listing CO₂ canisters has an empty line for it and there are very detailed reports about this fighter, which would likely mention the system if it was there.

Sources

Spoiler

U.S. Strategic Bombing Survey: Translations and Interrogations number 22, pages 25 and 32
国立国会図書館デジタルコレクション

Operational japan fighters. Intelligence summary no. 283-4 August, supplement CONTENTdm

Japanese Heavy Fighters 1937-1945, Dariusz Paduch, 2022

Japanese Secret Projects: Experimental aircraft of the IJA and IJN 1939-1945, Edwin M. Dyer, 2009

X-Planes of the Imperial Japanese Navy & Army, Nohara, 2000

Famous Airplanes of the World: Kyofu, Shiden, Shiden-Kai Extended Edition, Bunrindo, 2020

Kawasaki Ki-61 Hien / Ki-100 (Monographs), Leszek A. Wieliczko, 2014

3 Likes

+1 for realism

Any additional information about the Japanese WWII era extinguisher system is very welcome!
I have also heard that some Cold War era jets had fuel tank extinguishers, but nothing precise so far. Can anyone confirm this?

Here is a page about the system installed in A6M5.

For some reason the CO2 system of Shiden and Shiden Kai are very well recorded, but finding anything about their seat armor has proven impossible.

1 Like

+1, but does this mean the shiden family shouldn’t have an engine extinguisher?

In the Shiden system scheme there is the engine extinguisher:
image

I’m dumb, for some reason I thought the arrows are reversed, to take the co2 into the extinguishers.

1 Like

+1