“Everything was better with us, everything was worse with them”
Perhaps as an additional form of protection for already well protected plane if extra weight wasn’t too much of an issue. The fuel tank extinguishing system is usually best known from N1K2-J and few other late war types, however it’s important to know where the use started to understand why only Japanese used them.
The first uses in combat that I can find were with A6M5 and G4M, both of which didn’t have self-sealing fuel tanks at that point. It is well known how IJN took very long to implement self-sealing tanks into their aircraft. In this IJA wasn’t far ahead as their early “leakproof” tanks, which are said to have been only somewhat effective against .30cal. The jump from mainly rifle caliber armed Chinese fighters to US fighters of 1942 and onwards with up to 6x.50cals was too big for Japanese to keep up. In the same year they were still trying to acquire more advanced fuel tank protection technology from Germany. In fighter aircraft Japanese only fielded satisfactory self-sealing tanks from start of 1944, though improvements were still desired. Compare this to other major air powers of the war.
Early on with IJN aircraft, it appears those fuel tank extinguishers weren’t even expected to save the aircraft, but rather put out the fire so the valuable aircrew would have time to jump. The danger was even worse, because non self-sealed tanks didn’t only catch fire easily, but they could also quickly “deform” and explode from large caliber hit and the following fire.
Later on Japanese developed effective self-sealing fuel tanks, but these became thicker and heavier than comparable Allied types. This was mainly a problem for single engine fighters as it was difficult to fit these type of tanks into the wings without sacrifing fuel load. Army was satisfied with Ki-84 with fully self-sealing tanks, even when the range was slightly less than desired. Ki-61 probably couldn’t just switch to the thickest tank type as it’s said these had fuel tank extinguishers as well. Anyway IJN and Mitsubishi had very different approach to this problem: J2M and A7M were made with non self-sealing wing tanks. Only the fuselage tank was self-sealing and all tanks had extinguishers.
The fuel tank extinguishing system was overall very simple: They were just tanks with piping and thermostat as trigger. I don’t see any reason to suspect why the system itself wouldn’t be effective, but without dozens of reports it is impossible to write down any kinds of statistics how they changed results of the combat. This is further complicated by all the very different types of aircraft where the system was used. Furthermore an aircraft which would get to test the system in combat, was already damage, thus it had lower chances of getting back home to report. There are still Japanese archives where something related could be found, but how comprehensive report would one realistically expect?
At any rate the flaws of the system are very obvious:
- CO² or nitrogen bottles and their piping added weight.
- The system could be damaged by hits.
- There was only one shot for each fuel tank.
- It didn’t seal the tank like a self-sealin fuel tank.
Overall well made self-sealing fuel tanks were a better option.
There are few things I have not seen mentioned in other sources than that book:
-IJA used nitrogen extinguishers. I do not know if these changed to CO².
-Some variants of Ki-21, Ki-48 and Ki-49 had extinguishers.
