Expert: Paul Soderman - 6/24/2009

Question
Hello Paul,
I'm building an experimental plane and considering conversion to a diesel engine. I'm trying to establish a break even (if there is any) between the advantage of the higher torque on a propeller against a lower shaft power (smaller engine, lighter).
What could you suggest as a first way forward to have a quick evaluation on feasibility of such a project.

Kind regards, Martin

Answer
Martin
You haven't given me very much information.  How do you get higher torque with less shaft power ?  I am not an engine expert so may not be able to help you anyway.  Generally, you need high torque for takeoff when the propeller is working hard.  The requirement depends on the propeller performance curves and the aircraft takeoff weight and drag and takeoff distance.  To really analyze this you need someone who can evaluate your propeller versus aircraft takeoff and cruise requirements.
Paul