cointyro
New Member
I was reading through my new copy of Gleim's PP knowledge test prep book, and came to a section on W&B. Namely, one of the question explanations stated that a plane with an aft CG flies at a lower angle of attack, and also stalls at a lower speed.
I was trying to reason this out in my head and couldn't figure it out.
In straight and level flight, lift must equal weight; and lift is proportional to the coefficient of lift times the amount of air deflected vertically by the wing.
A lower AoA means a lower coefficient of lift; and slower flight means less air vertically deflected by the wing. This would suggest, in my interpretation, that if you're in straight and level flight, if you decrease your AoA AND your airspeed (a double whammy), your lift drops especially and you'll descend.
So how does an aft CG cause lower AoA and lower stall airspeeds (in level flight) when compared to normal CG? In either case lift must be the same...
Does this have to do with the fact that induced drag (the horizontal component of lift, usually directed rearward) is typically less at lower AoAs?
Thanks for any clarification on the matter! In my studying, I first have to understand the why behind aircraft behavior ... this makes it easier for me to reason out the answer when I've forgotten the "memorized by-rote" answer.
Now if I could just figure the reasoning behind compass deviations (ANDS, etc.) ... I think I'll stick to the memorization tools for that
I was trying to reason this out in my head and couldn't figure it out.
In straight and level flight, lift must equal weight; and lift is proportional to the coefficient of lift times the amount of air deflected vertically by the wing.
A lower AoA means a lower coefficient of lift; and slower flight means less air vertically deflected by the wing. This would suggest, in my interpretation, that if you're in straight and level flight, if you decrease your AoA AND your airspeed (a double whammy), your lift drops especially and you'll descend.
So how does an aft CG cause lower AoA and lower stall airspeeds (in level flight) when compared to normal CG? In either case lift must be the same...
Does this have to do with the fact that induced drag (the horizontal component of lift, usually directed rearward) is typically less at lower AoAs?
Thanks for any clarification on the matter! In my studying, I first have to understand the why behind aircraft behavior ... this makes it easier for me to reason out the answer when I've forgotten the "memorized by-rote" answer.
Now if I could just figure the reasoning behind compass deviations (ANDS, etc.) ... I think I'll stick to the memorization tools for that
