The problem with the Osprey, if I'm thinking about the same one as you, is related to the extreme diameter of the rotors and the aerodynamic effect of sharp turns while descending. Basically, the inboard rotor "stands still" while the plane executes a sharp turn around it, while the outboard rotor gains speed. With a single rotor there is no separation to induce the differential lift, and on the Harrier the thrust is not dependant on a horizontal rotation. The differential is not huge, but it's enough to increase the rate of roll -- a nasty feedback loop.

There's more than one. :)

Part of the problem, according to what I read, is the "fly-by-wire" system. Apparently all of this stuff is (supposed to be) automated, so the pilots don't have to worry with it. (Side effect, they can't override/change it)

Add to that that the systems are multiply redundant (complicating the software, isolating bad systems and deciding which systems to use, etc.

The aerodynamics of the bird I don't think are *that bad*. The civvie version apparently isn't having the problems, or else their software's got the problems compensated for.

So I don't know about that particular problem, its entirely possible - with a piston airplane, turning 2300 RPM, there's a HUGE pull to the side when you are angled up (thus increasing the lift on the prop coming "down" to the relative wind, and decreasing it to the "up" side).. A turn like that might end up with some problems similar. (I'd have thought the length of the mass arm would prevent it from doing that much).

I'd also think the Chinook would have had similar problems, and had most of them sorted out.......

Addison