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Welcome to the CPL Performance question and answer forum. Please feel free to post your questions but more importantly also suggest answers for your forum colleagues. Bob himself or one of the other tutors will get to your question as soon as we can.
Hey guys, just got a question on the ppe website for performance. I guess the particular question is also an aero question.
Why is it that when you add weight you must fly at a faster airspeed for max range? If i was to fly faster i would require aditional power which would burn more fuel and i thought decrease range. Does the fact that you get there faster work out better for range even with the higher power setting?
It is not the speed alone that decides the efficiency of the wing, it's the ratio between lift and drag. For a particular aerofoil shape, the lift/drag ratio is determined by the angle of attack only. To fly at maximum efficiency you must fly at a particular angle of attack (for typical GA types this is somewhere near 4°). Lift is a product of both the speed and angle of attack of the wing so, if you need more lift (increased weight), you must fly faster if you don't want to change the angle of attack.
You would need more power to fly at the higher speed required if you were heavy, so range would be reduced at the increased weight. You just have to accept that.
It's the angle of attack that decides the lift/drag ratio.