Yes, the 2 stroke burns 50% more fuel for the same HP, but the point I
was trying to make was that since the 2 stroke powered aircraft can be
built lighter all around (on account of its lighter engine), you can
use a smaller engine (which consumes less fuel) and still fly the same
payload. This relationship is unique to aircraft since weight means
SO much.


"Richard Isakson" wrote in message ...
"Jay" wrote ...
I've been under the impression that 4 stroke engines get better gas
mileage in aircraft due to their higher BSFC numbers. But I've
recently realized that since the 4 stroke engines are so much heavier
than a same horse powered 2 stroke you end up having to design a
larger aircraft (and engine) to carry the original intended payload
plus the additional weight of the engine. So in the end, a purpose
built 2 stroke airplane will be smaller, lighter may even get better
gas mileage.

Not so, Jay. The two stroke burns fifty percent more fuel then the four
stroke so you have to carry fifty percent more fuel weight. For an airplane
with fuel for a four hour cruise, both airplanes weigh about the same.

Rich