Originally posted by John Weber
Thanks for the corrections Dirty Birdy, I was trying to write that post and teach a class on gas turbine engine maintenance at the same time and got a little distracted. Anway, engineers at GM's Allison Division concluded after exhaustive research that yaw induced cyclic vibrations from the Electra's big fourbladed propellers excited the wings natural resonant frequency and led to wing flutter. A contributing factor according to an article posted in Air and Space magazine:
http://www.airspacemag.com/ASM/Mag/I...FM/Hammer.html
was prior engine mount damage. Apparently engineers redesigned the engine mount and the problem was solved. No mention is made of CAT in the article but it could have been a contributing factor in setting up the initial yawing motion that triggered the whirl mode.
J.W.
I got my information from an article in Aviation Week or it might have been Newsweek shortly after the incidents. The name of the article was "Caught in CATs Claws".
I found I had to take the AC from Chicago to Minneapolis or take a bus. The airline assured me that with the restricted airspeed I had nothing to worry about. I did not enjoy the flight.