"F. Baum" wrote in
oups.com:

On Nov 8, 9:29 am, Dudley Henriques wrote:

Dud,
Isnt Harmonics and Whirl Mode Flutter two diferent things ? I used
to fly a turboprop that had Whirl Mode issues (And a crash
resulting from this), but not any resonance restrictions. On the
other hand, I flew Scouts that when equiped with a certain
propeller (For banner towing) had restrictions on certain RPM
ranges because of resonance issues.

KFB

Yes, in the true sense of definition. I haven't done any research on
the Electra crashes and the cause. It was my understanding that whirl
mode was a direct cause link.
Exactimundo. In the later Electra it was, but I doubt they had much
knowledge of this in 1938. In fact, Whirl mode wasnt much of an issue
until the 1950s when they started using small (By comparison)
lightwieght engine/gearboxes with massive props mounted on long moment
arms. I would argue that the harmonics/ resonance issue that brought
down the 1938 Electra is a completely different kettle of fish.

Any Harmonics interface would probably have
been considered as a peripheral result of how the whirl mode
transmitted through the resonant frequency of the structure.

Whoa! Slow down, your making my head hurt .

Understanding the entire sequence is fairly complicated.
See Bertie's post above this one. I believe he has explained it
fairly well. DH

Once again, Bertie saves the day


Ta da.

But I'm only repeaing what little i know about it.
Best check with an expert before you go out and design your own
airliner.


Bertie