To HDi: someone did build a prototype piston engine as you suggest in the 1990s. It would have been quite heavy. It never got off the test bench but that doesn't mean it would be no good. But it must be able to meet the skeptics' views if it's to get Certificated.
But what you need for an aero engine in the apparently conflicting requirements of simplicity and sophistication. Simplicity for reliability and costs and weight, sophistication for economic high performance. I think my design - if applied to a multicylinder engine would fit that mould.
To Wayne: I don't know about a Rotary. Interesting idea. Propellers are liable to break with vibration and a rotary would get round that, they're smooth. (My multi cylinder concept - nothing new in more than one cylinder!!! - would be pretty smooth, esp being 2-stroke).
A rotary with modern smooth burning diesel injection technology might work quite nicely.
Malc
