[quote=JA Boomer;435212]The primary reasons are that diesels engines tend to be more robust, thus heavier and larger than similar aviation gasoline aircraft engines. Diesel engines also tend to work at slower speeds (lower rpm's) than avgas engines, which is a disadvantage for a prop. Diesels also suffer from poor cold weather performance, so you can see this may be a problem in some climates and at altitude.
Slow revving is good. Most propellers are not efficient at over about 3,000 rpm. That's true even for the WW2 piston engined fighters.
The MAIN reason that diesel engines have not caught on significantly though, is probably just because aviation gasoline is an institution. It was the first fuel for aircraft, and no one ever really looked back.
Until WW2, it was ordinary 'motor spirit' (ie petrol) that was recommended in the user manuals of the time
Probably be hard pressed to find aircraft grade diesel around, where as avgas is still quite common.
Is there such a thing as 'aircraft grade' diesel?
I do think you will see an increase in the number of diesel powered aircraft in the coming years. Primarily because the demand for avgas is declining (has been since 1957). The primary form of avgas (100LL) and many other grades still contain lead additives, so there is also a push to get rid of it for environmental and health reasons. Also, the rising price of crude doesn't help things.
I wonder how successful it would be in putting a diesel engine in place of the Lycoming or Continental on the existing metal aircraft like Cessnas or Pipers? I suspect that they are generally dragmasters that need to be over-powered in able to fly at all!
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