Aircraft
flight control surfaces allow a pilot to adjust and control the aircraft's flight
attitude.
Development of an effective set of flight controls was a critical advance in the development of the aircraft. Early efforts at fixed-wing aircraft design succeeded in generating sufficient lift to get the aircraft off the ground, but once aloft, the aircraft proved uncontrollable, often with disastrous results. The development of effective flight controls is what allowed stable flight.
This article describes controls used on a fixed wing aircraft of conventional design. Other fixed wing aircraft configurations may use different control surfaces but the basic principles remain. The controls (stick and rudder) for rotary wing aircraft (
helicopter or
autogyro) accomplish the same motions about the
3 axes of rotation, but manipulate the rotating flight controls (main rotor disk and tail rotor disk) in a completely different manner
TURNING OF THE A/CRAFT
Unlike a boat, turning an aircraft is not normally carried out with the rudder. With aircraft, the turn is caused by the horizontal component of lift. The lifting force, perpendicular to the wings of the aircraft, is tilted in the direction of the intended turn by rolling the aircraft into the turn. As the bank angle is increased the lifting force, which was previously acting only in the vertical, is split into two components: One acting vertically and one acting horizontally.
If the total lift is kept constant, the vertical component of lift will decrease. As the weight of the aircraft is unchanged, this would result in the aircraft descending if not countered. To maintain level flight requires increased positive (up) elevator to increase the angle of attack, increase the total lift generated and keep the vertical component of lift equal with the weight of the aircraft. This cannot continue indefinitely. The wings can only generate a finite amount of lift at a given air speed. As the
load factor (commonly called G loading) is increased an accelerated aerodynamic
stall will occur, even though the airplane is above its 1G stall speed.
The total lift (load factor) required to maintain level flight is
directly related to the bank angle. This means that for a given airspeed, level flight can only be maintained up to a certain given angle of bank. Beyond this angle of bank, the aircraft will suffer an accelerated stall if the pilot attempts to generate enough lift to maintain level flight.
