Originally Posted by
A0283
Remember at least one all fatal crash with early Electra's where the complete engine plus nacelle and mounts vibration that you seem to describe took the wing off. It appeared that the wing was too stiff. Redesign changed the natural frequency.
Do not remember reading in that report about such earlier events. Which is rather amazing.
There were two - Northwest and Braniff. Actually, the wing wasn't too stiff - there were multiple issues - outer nacelle not stiff enough, engine mount damage from repeated hard landings, gearbox-to-engine structure failure, wing torsion. But that raises an interesting point. Metallurgy, composites, designs, construction have certainly changed since whirl mode. But what really is the airframe tolerance to the 'new' jet-age replacements from 'vibrations' compared to the very vibrating four-bladed props?