On: How Qantas Ferried an Engine on the Wing of a 747

[drewkett]

I would guess it's a flutter problem. Flutter is when an aircraft becomes dynamically unstable due to the interaction between the aircraft structure and the air around it. Certain aircraft are more prone to flutter than others such that it occurs at speeds closer to its max airspeed. The type of engine and how it's attached to the wing can have a big effect on flutter since it's a large mass that's hanging off the wing. As a result the same aircraft with different engines can have significantly different flutter properties.

https://en.m.wikipedia.org/wiki/Aeroelastic_flutter#Flutter

[stergios → drewkett]

An oscillation builds up in the wing span to the point where the wing self destructs. Here's an video example from the development of the 747:

http://www.airspacemag.com/videos/category/flight-today/wing...