View Full Version : ATPL POF question
During flap down selection in a continuous straight and level flight at constant IAS and weight:
Choose one answer.
a. the lift coefficient and the drag coefficient increase.
b. the total boundary layer becomes laminar.
c. the stall speed increases.
d. the centre of pressure moves aft.
right answer is "d".
Why not "a"? Or both of them is right?
cheers
zondaracer
5th Jul 2011, 21:11
It is not "A" because you are maintaining "straight and level" flight. If you lower flaps, you will increase your coefficient of lift, causing you to climb... So you put your nose down to decrease coefficient of lift down to your original coefficient of lift on order to maintain straight and level.
Key words: straight and level, constant IAS and weight
mad_jock
5th Jul 2011, 21:41
A is bollcks because as the previous poster states your at constant IAS and S &L so you would expect to increase the power input but CL would remain the same but the Cd would increase.
B is bollocks because if it wasn't you would be on the dirty side of the drag curve. I might happen but I doudt it.
C. The joker card of the oppersite to what actually happens.
D. The most plausable
These questions you will always get one like C which you can discount as being simply wrong then 3 others which have there merits. Then pick the one that is most plausable.
Thx zondaracer Its what I thought, but was not sure.
Thx mad_jock