Atlantic Southeast Airlines Flight 529 - Wikipedia, the free encyclopedia
I believe this one was due to the manufacturing process. The blades actually have a portion of their shank hollowed out on the PW 120. Improper peening of the interior and chlorine on the cork that is supposed to keep the moisture out seem to be factors according to distant memory. Accurate records enabled investigators to find the exact guy who made the errors.
Here are two that I studied during my Masters coursework:
Convair 580 and
Embraer Brasilia
I think you are confusing the ASA529 with the Lake Central CV580. The Aeroproducts props on the CV580 (and some L-188s) has the hollow blade shank with helical splines and an actuating piston inside each shank. In that case, one piston was not nitrided per spec (actually one of a bad batch of ten), and became disengaged. The blades migrated rapidly to fine pitch (they ALWAYS do), oversped and came apart, and practically cut the fuselage in two.
ASA529 had the helical pitch actuation tube - axial within the prop shaft - wear out so the blades were free to migrate rapidly to fine pitch (they ALWAYS do), and although the aircraft was slow enough to prevent destructive overspeed, the drag was insurmountable and the aircraft uncontrollable. The curious fact in this case was that H-S claimed during prop certification that the blades should go to COARSE pitch upon failure - despite maybe 5 decades of experience to the contrary. Neither H-S nor the FAA personnel were astute enough to challenge this assertion!
BTW - The politician who died was Sen. John Tower of Texas. Also killed was an astronaut, Manley "Sonny" Carter.
Interesting speculation:
IF the Brasilia failure had occurred at high IAS, the overspeed might have caused the prop blades to fail, but their lightweight composite design might have prevented them from penetrating the fuselage, which had occurred in the CV580 accident.