Mike Marron wrote:

snip




Although I have a 4-stroke behind me when I fly nowadays,
2-strokes have evolved into extraordinarily reliable engines
and I've accumulated more than 1,500 hrs. flying aircraft
equipped with "grassroot" 2-stroke engines. We normally
premix the oil 50:1 (not Castor oil) but except when starting
after a prolonged period of inactivity, they rarely emit the
characteristic blue 2-cycle smoke anymore. Given their
impressive power-to-rate ratio, 2-cycles are ideal for light sport
A/C. For example, in 1993 an intrepid Alaskan pilot flew a 2-stroke
over Mt. McKinley's 20,320 ft. summit, and on Sept. 29, 2000, Czech
pilot Jan Bem set a world altitude record of 26,546 ft. overflying
the peak of Annapurna, Nepal, in the Himalaya Mountains while
flying a 2-stroke powered trike. The U.S. military still uses 2-cycle
engines on numerous different remotely-controlled surveillance
drones.

Has the Orbital design been applied to any aviation 2-strokes? After
Honda licensed it in the 90s there was much anticipation of a new,
cleaner generation of high-output, lightweight 2-stroke bikes, but it
hasn't happened yet.