TomM
It is a double edged sword! Extension of flaps on landing ie in the descent has the effect amongst other things of increasing drag and lift but the aircraft is descending so tapping into potential energy as another source of energy supplied by the engines.
The drag helps control the speed the lift allows the aircraft to fly at VREF for landing.
Takeoff is different we have the lift required to takeoff at a relatively slow speed but with that comes the drag.
Not just from the takeoff flap setting but from the gear and increased AOA!
The gear we get away quickly but we are at max N1 and at slow speed with no potential to tap into potential energy from the airframe should for any reason we need it and limited ability to reduce AOA.
Obviously the main concern in cleaning up in event of an engine failure or loss of power but there is another!
In still air all well and good but in shear conditions that slow speed can become critical.
Hence it is better to concentrate on flying the aircraft in a stable condition until well clear of the ground where you have the ability to tap into potential energy should you need to as well as reducing drag by reducing AOA before going from flap takeoff to zero.
Some say 400agl some 1000agl
Pace
Last edited by Pace; 16th Nov 2012 at 15:40.