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Douglas -

Not a direct answer to your question, but...   Aerobatic performers and weekend enthusiasts like myself tend to favor
composite props mainly because they induce far less torsional loads on the crankshaft during gyroscopic maneuvers.  For
instance, a Pitts with a metal prop doing a snap rolls has to withstand 55,000 in-lb at the crank!  Yowch.

Having flown a Pitts S-2B with both 2-blade metal Hartzell and 3-blade composite MT, I will say that the flywheel effect
is markedly less with the MT.  And I felt that the engine ran smoother with the MT, because those blades (thin glass
covering over wood core) absorb vibration quite well.  I also flew a 3-blade Hartzell composite (Kevlar!) and found the
vibration level to be somewhere between the metal Hartzell and the glass/wood MT.

And yes, aerobatic engines have lower TBO's.  I think that's due to a combination of frequent and rapid power changes,
generally high power settings, torsional loads, and momentary oil starvation during maneuvers.  Vibration is typically
the least of our worries.  :-)

Regards,
DJ Molny
Extra 300/L, N133DF
Lancair someday, maybe


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