first question here, so please be gentle!
I'm reading an entry-level engineering course book and am currently up to discussion of aircraft design.
There's one particular statement that is unclear to me:
Turning with the wing level is aerodynamically inefficient and the inner wing loses a lot of lift because it is moving relatively slowly through the air.
Does this mean that, for maximum lift efficiency, a wing has to be horizontally level? I understand that the upward pressure beneath the aerofoil is greater than that above it pressing down, so how does the upward pressure change beneath the aerofoil change when an aircraft is turning? Does downward pressure increase?
Best Answer
Lift is a function of the speed of the air from the leading edge to the trailing edge. In a flat turn, the inner wing is moving slower than the outer wing therefore there will be a difference in the amount of lift produced.
But in fact, an airplane can not change direction by flat turning this way. Rolling into the turn by the use of the ailerons is the way a plane turns. This causes part of the lift to be directed into the turn and used to pull the plane around the turn. Think vectors.
The slowed inner wing will still produce less lift and the rudder is used to compensate against the tendency to slip into the turn further. The elevator is used to raise the angle of attack again to compensate for decreased vertical lift in the the turn. Angle of attack is the angle that the wing makes relative to the air flow. A higher angle of attack at the same speed creates more lift. To a point.