Electra LEAP
The first thought on someone’s (objective) mind would be Whirl Mode.
Absent the main spar couple at low Hertz, the power line (especially outboard) can inflict serious damage to the wing, especially the more sensitive, less reinforced structures, specifically the piano hinges at the ailerons. This type of hinge is light, easy to service (exposed), and relatively inexpensive. It is efficient in the distribution of stress, but falls short of a design consideration that might include profound asymmetric vibration.
As I stated before, Lockheed’s “experimental” test of Flap/Aileron fouling was not to do with aerodynamic loads. That ship sailed in 1957, and no unknown “spill” or vortex generated stresses were unknown.
It was specifically designed to “exonerate” engine/propellor induced damage to the aileron. That is why the jack was removed from the experimental system.
Any success with FOIA?
Of importance would be the eyewitness accounts of the “engine noise” alteration(s). Again, most of the noise produced by a heavy turbo prop is propellor related, and any changes in tone would suggest pitch change (isolated to one system?). Something to look for would be oscillations in tone and volume, (surge) which would suggest problems related to thrust, and especially (if found) a system which has lost its steady state.
The rolling release, the turn onto the center line, the known Slop in the primary cabling, and the damage signature on the aileron suggest an early failure, at full power. An early and uncommanded roll would have had everything to do with lack of climb angle (who has time to increase pitch with such a serious problem showing up, and especially if one is considering an abort of the takeoff?) and also the very early “turn”.
edit. As a student pilot when I encountered the Whirl Mode on the Electra (as a passenger), I was thinking about p-factor as a source of vibration, since it would have been changing rapidly with each rotation of each blade. The propellors angle of attack would have been chaotic, to say the least. The noise we heard in the cabin was from Hell....
Last edited by Concours77; 7th Feb 2018 at 15:00.