Originally Posted by
B2N2
Anything deflected in the airstream will produce extra drag hence trimmable horizontal stabilizers on transport category aircraft.
Center of pressure ( center of lift ) needs to have a certain position relative to CG otherwise stability issues arise.
You've got to see the whole rather then a single component.
Ideally there is no up or down force as this would be the lowest drag scenario. Whether this is achieved for any significant amount of time, I don't know.
With large swept back wing aircraft CG changes with (wing) fuel burn.
OK ... so essentially the ideal situation is to have 0 trim, but this is rarely possible due numerous other factors such as pax seating, cargo in the hold etc?
That offers me a different perspective, because the impression of gotten so far in my studying of stability is that aircraft are intended to have a forward CoG in flight, to give positive stability in case of an upgust etc and that the horizontal stabilizer is designed to counteract this by producing a downforce. I was wondering what happened in the rare instance that it wasn't possible to have a fwd CoG and so my initial question arose ...