OK guys, help me out here: I can't believe that the prop of a dead engine would rotate at gliding speed. It doesn't on my microlight (Rotax-503, 2 cyl, 500cc, 50hp), it didn't the only time I tried engine off in a Cessna 150 (Lycoming, 4 cyl, 2-3,000cc?, 110hp).
I can't see a prop just leisurely rotating at 120-140kts being attached directly to the crankshaft of a 30-40 liter 12-18 cyl monster. Not to mention the case when it's (the engine) is full of holes and debris.
IMHO you stop the engine - prop stops with it, feathered or not would only affect the amount of drag it should generate. Anyone knows any different?
(In a dive and other daft conditions it would be possible to turn the engine just by the sheer speed/power of airflow blah-blah-blah. I'm talking about "normal" situation here that is if PFL is ever normal

).
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-lynx-
13 Sqn RAF