Originally Posted by Ramendala
Have you seen the Lightning? Supposedly this is a redesigned airplane but it's bones look an awful lot like the Lancair 320. Just stick a serious climb FP prop on the nose
This seems to be one of the most misunderstood LSA perfomance requirements. The requirement is that the airplane meets the 120 kt max. speed requirement at max continous power, not max continous RPM. Because of this you must meet the speed requirement when operating at max contious RPM and a manifold pressure that at the RPM you are using, provides max rated continous power.
Putting a flatter prop on that requires a throttle reduction to stay within the engines RPM limit and the resultant limit in speed, does not meet the ASTM requirement for LSA
Originally Posted by WyoDave
I don't really keep up with LSA rules. But would it be possible to write in some continuous power limitations like Cub Crafters has done with the Super Sport Cub to keep cruise speed down? There is probably more to it than that...
This is probably the only possible way to do it, but as Mel already metioned, I think anyone doing so is walking a very fine line. If an identical engine is also rated at a higher power output in another aircraft I would think the FAA will likely have some raised eyebrows eventually.
Over the years there have been different type certificated airplane models that have used different models of an engine with it rated (or derated) at different power outputs so maybe they are ok with it.