More on propeller mach speed

[Mike Kimball]

I got curious with recent research and discussion and decided to take a look
at some typical, modern (term used loosely except for the Lancair) aircraft.
I found the following:

Piper Archer - Takeoff RPM 2700, propeller diameter 76 inches, mach speed
0.815
Cessna 172 - Same as the Archer
Cessna 152 - Takeoff RPM 2750, propeller diameter 69 inches, mach speed
0.756
Cessna 182 - Using a BlackMac 3-blade, scimitar blade design conversion,
takeoff RPM 2600, propeller diameter 80 inches, mach speed 0.826
Lancair 4P - Cont. TSIO-550, Takeoff RPM 2600, 3 or 4 blade, all approved
props are 76 inch diameter, mach speed 0.786

Clearly, the spam-can manufacturers adhear to Ken's "around 0.8 mach"
philosophy. Slow planes versus fast planes doesn't seem to matter with the
Lancair in the same boat. Lot's more thinking to do before I decide whether
or not to make a change.

Mike
044SR




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