Hi Golden Rivet
Quote: " Lowering the flaps in flight generally will cause a change in the pitching moment. The direction and degree of the change in pitch depend on the relative original position of the centre of pressure and the centre of gravity. The factors that contribute to this are
1. The increase in lift created by the increased wing area and chamber will lead to a pitch-up moment if the centre of pressure remains in front of the centre of gravity.
2. If the associated rearward movement of the centre of pressure is behind the centre of gravity, then this will produce a nose-down pitch.
3. The flaps will cause an increase in the downwash, and this will reduce the angle of attack of the tailplane, giving a nose-up moment.
4. The increase in drag caused by the flaps will cause a nose-up or nose-down moment depending on whether the flaps are above or below the lateral axis.
The overall change and direction in the pitching moment will depend on which of these effects is predominant. Normally, the increased lift created by extending the wing chord line when the flaps are extended is dominant and will cause a nose-up pitching tendency because the centre of pressure normally remains in front of the centr of gravity."
Hope this helps.