Do a search for Lockheed Electra, Tell City Crash, 1960 I believe.
Reference that with propeller whirl mode, and you should come up with
all you'll ever need to know about resonant frequency as relates to
destructive force.

Hmmm. If it happened to another Electra in 1960, that says a lot.
The crash I'm talking about happened in 1938.

I guess maybe they DIDN'T address the problem...?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"