Question

How do the required CL and AOA for a Piper M350 at 4,000 lbs change with changes in airspeed? (Provide specific examples)

What happens if the required CL is larger than CL_max of your airfoil, and what speed regime is usually associated with that condition?

Answer 1

If required CL is larger than CLmax of your airfoil, it will result in aircraft to stall.

CL max of an aircraft depends on the value of the maximum usable angle of attack. Now, from where does this angle of attack limitation come from? Actually it can come from many sources. Here are some

1. Stall : the angle of attack beyond which the the flow over the wing is separated and the wing no longer produces lift. No lift , No flight. The lift at this angle of attack then becomes the max CL value. For delta wings, this limitation is never hit since other limitations are much smaller than this.
2. Minimum pitch acceleration limit : this limit comes basically from the control power of elevators. As the angle of attack increases, elevator powered reduces. If beyond certain angle , the elevator is not efficient to pitch the aircraft, then that angle becomes the limitation and CL at that AoA becomes max CL.
3. Lateral/directional stability requirement : as the AoA increases, the stability of the aircraft reduces. the angle of attack beyond which the aircraft is no more stable becomes the limitation on angle and thus on CL max. Generally, directional stability limit is hit before lateral stability limit.

https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak/media/07_phak_ch5.pdf

Please go through the above link for a detailed description to your doubt