There is an asymmetry of lift with one engine inoperative, assuming that the slipstream passes over the wing. This
might allow for asymmetry of induced drag, which could give rise to reduced VMCA when IGE.
The live engine (propeller not jet?) generates slipstream over part of the wing & therefore more lift, while the windmilling engine generates disturbed air over part of its wing.
In practice asymmetry of lift is counteracted with aileron towards the live engine to maintain some specified angle of bank.
There is an asymmetry of induced drag associated with this aileron use - failed engine wing is operating at an increased AoA due to displaced aileron. However, I would have thought it negligible. Perhaps in some aircraft types the aileron drag asymmetry has a measurable effect on VMCA in ground effect, hence the restriction.
FlyingForFun - in my interpretation, Part 23 doesn't make comments based on the safety or otherwise of particular flight test manoeuvres. Perhaps it should!
cheers to all,
O8
