R-3350/B29 Question

[LysanderUK]

Reading the various accounts of engine reliability and fire problems in the B29, the details of exactly why the early gen 3350's were so failure/fire prone never seems to be fully explained. Can anyone explain, or point me in the direction of a good write up, exactly what the details of the problems were?

[Cvairwerks]

Here's a link to an article on some of the early engine problems.

https://www.enginehistory.org/Piston/Wr ... R-3350.pdf

[gemmer]

Here's a link to an article on some of the early engine problems.

https://www.enginehistory.org/Piston/Wr ... R-3350.pdf

Not much info on engine fires. I find it interesting that articles that do deal with 3350 engine fires usually put more focus on the firewall design and don't say much about the forward facing exhaust collector ring design and resulting cooling problems. Speculation is that the design was a production expedient.

[sandiego89]

I believe the early fire problems were largely due to overheating, especially in the rear bank of cylinders on the 3350's as there was inadequate cooling air reaching the rear bank. The engine cowlings were tight for maximum streamlining. Compounding things was the exhaust configuration and the use of magnesium components in the engine to reduce weight. Further compounding things was the high ambient temperatures in India and the Marianas, high gross weights, inadequate fire suppression bottles, and a firewall that often failed to contain a fire, resulting in burn through to the main spar.

So hot engine + inadequate cooling + magnesium +high ambient temp + max RPM (over weight) = fire potential

and once a magnesium fueled fire gets going, potential burn through