Roll/yaw as BEagle explains i.e. there is generally more side area (fin and fuselage) aft of the CoG, so if the aircraft is rolled the tail will tend to slip sideways slower than the nose hence yaw.
Blobber, you have to consider roll in isolation - if you introduce pitch (back pressure) then additional factors come into play and it all comes under 'Far Too Difficult'. In EoC 1, when demonstrating the secondary effect of roll, you cannot introduce back pressure or it all goes tits-up.
Trimming (in pitch) is necessary to offset any imbalance in the lift/weight and thrust/drag vectors: The thrust and drag vectors do not generally act on the same point in the vertical plane (e.g. Catalina, engines above fuselage in wings, or B737 below wings), thus when thrust is changed the thrust/drag coupling changes and retrimming is necessary. Changing airspeed changes the drag vector rather than thrust, but the principle is the same. Lift/weight similar but at right angles to thrust/drag and will generally change with airspeed and e.g. fuel burnoff.
Last edited by DB6; 26th Mar 2007 at 15:32.
Reason: to add a bit