Ng pitch up when extending flaps
 

sorry but have to ask, due Centre of Pressure moving forward due greater wing area or just extra lift being created?

thanks

pin

C of P will move aft when flaps are extended.

As usual it'll be a combination of effects but I'd suggest the largest is increased downwash creating higher alpha on the horizontal stabiliser.

Hmmm "trailing edge or leading edge flaps ??"..Due to the effects that the leading edge is "Initially faster" The COP does momentarily move forward..Then as Chesty has answered its a catch up..

There are several things going on when you extend trailing edge flaps ---

1. You're increasing the lift due to increase in wing area and geometry. This results in a balloon. The C-17 deploys spoilers when extending flaps as anti-ballooning action. The change in geometry can be visualized as both a change in chamber, which results in an instantaneous increase in local angle of attack, as well as different lift characteristics (CL, CD, & CM_alpha vs alpha).

2. You're increasing the down wash on the horizontal stabilizer, resulting in a pitch down.

3. Anytime you change the span wise lift distribution on a swept wing, you get a pitch change. The manufacturer tries to minimize this by careful placement of the trailing edge flaps. Some aircraft (B707, B747), you can split the outboard and inboard trailing edge flaps and extend one set to affect a change in pitch.

Selecting Flaps2 on the A320 will cause a +200ft balloon. I've seen pilots miss catching the GS because of this. Most of us gray-hairs have figured this out.

The MU2 solved a similar problem by extending the flaps in small increments so the trim could keep up with the pitch change.