Mad Flight Scientist wrote:
The moment due to the engine is basically net thrust of the asymmetric live engine * the distance from centreline - which is essentially independent of forward or aft cg.
The rudder moment is taken about the cg, so must be affected by fore/aft cg movement. So the rudder is less effective as the cg goes aft.
MFS, I have no doubt you're correct about the standard rules of calculating moments within the industry, however moments that are calculated about different datums cannot simply be added together. To use them, you have to convert them to the same data, which would require knowing c of g for the assymetric thrust moment.
The other thing to consider is that the moment itself is not that interesting without knowing the moment of inertia. Of course, moment of inertia is dependant on mass distribution.
I guess the only caveat here is actual experience with this condition. I.e. Does the c of g actually affect Vmcg? Certification people seem to think so. What is the experience of the ppruners who have flown these tests?
Matthew.