Fuel economy in the air (diesel airplanes?)
 

So I was reading the thread I can no longer find a while ago, and the thought has been roiling around in my mind since... Most prop planes are spark-ignition, aren't they?

Has anyone ever built a diesel prop plane?

Good question. I'm intrigued. (Actually, I'm Christ. Intrigued is another member.) Nonetheless, I'm interested to see what kind of information gets dragged up in this thread.

...yes, diesel engines were used a lot during the 1920's-1930's:

http://74.125.155.132/search?q=cache...&ct=clnk&gl=us

...on a similar note -- I'd like to know "why?" EPA-fuel economy "guidelines" haven't also been applied (shoved up?) to the aircraft industry yet?

i have to imagine diesels are somewhat differently affected by altitude since their compression ratio is much more critical to combustion

What better excuse can there be to put a turbo on an engine. Although I was thinking in terms of a <10,000ft. type of plane.

The German Junkers bombers of WWII were diesel-powered.

That's why they make chokes.

Design the engine to run efficiently at high alt, and at low alt, it'll probably blow up, so you either set it up to only use a max amount of fuel, which is pig-rich at low alt, and perfect at high alt, or you set it up with a choke, so that it runs as a smaller displacement engine (effective displacement) at low alt, and runs "normally" at high alt.

...uh, guys, two words: turbocharger and wastegate


...turbo's were usually used on ALL high-altitude engines, especially fighters.

IIRC the main concern is fuel gelling and emergency air restarts, they see some real cold conditions.

theres a couple hits for diesel airplane on youtube
http://www.youtube.com/watch?v=l0BhcIT2V1s
(mentions Vulcan Diesel at 3:50 )
http://www.youtube.com/watch?v=Y-ybGay_-t8