Hi
diesel in aviation, is still making is first baby steps (in the fixed wing world) so to "jump" to the rotory world, will take a little more time (i think ...
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plus, if you think, for example, in the "Uncle Robby" models, where we like it or not they are the best/more selled models, until there is a "new kid on the block" they don't need to improve/go step futher using diesel engine... (don't know if make my point...
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only to know, another brand that advertises aero diesel engines for years, but still don't know how it goes this days is
ZOCHE aero-diesel
happynewyear
regards