Axes Quiz: Mastering Flight Control with Ailerons

Study Notes

Flight Control

Directional control of a fixed-wing aircraft takes place around the lateral, longitudinal, and vertical axes using flight control surfaces.
There are two major groups of flight control surfaces: primary (main) and secondary (auxiliary).

Primary Flight Control

Ailerons are attached to the outboard trailing edge of both wings and rotate the aircraft around the longitudinal axis (roll) when moved.
Elevator is attached to the trailing edge of the horizontal stabilizer and rotates the aircraft around the lateral axis (pitch) when moved.
Rudder is attached to the trailing edge of the vertical stabilizer and rotates the aircraft around the vertical axis (yaw) when moved.

Lateral Control

Moving the control stick or yoke to the left causes the right aileron to go down (left aileron goes up) and rolls the aircraft to the left.
Aileron reversal (aeroelasticity effect) can occur in high dynamic pressures and wings with low torsional rigidity, causing the aircraft to roll in the opposite direction.

Longitudinal Control

Moving the control stick forward deflects the elevator downward (tail goes up) and causes the nose to go down.
Elevator deflection is affected by the center of gravity (CG) location:
- CG ahead of the center of pressure (CP): requires bigger deflection of elevator, high longitudinal stability, and bigger control force.
- CG behind CP: requires smaller deflection of elevator, smaller control force, and low longitudinal stability.

Directional Control

Pressing the right rudder pedal deflects the rudder to the right (tail goes left) and yaws the aircraft to the right.
Rudder is used to overcome adverse yaw at the beginning of a turn, and also during crosswind and one-engine operation.
Rudder limiters are fitted to prevent involuntary motion of the rudder and limit its movement unless commanded from the flight deck.

Hybrid Control Surfaces

Ruddervator (rudder and elevator) combines pitching and yawing functions.
Elevon (elevator and aileron) combines pitching and rolling functions.

Secondary or Auxiliary Devices

High lift devices provide a compromise between high cruising speed and low landing speed.
Flaps are located on the inboard wing trailing edge and can be extended for takeoff and landing and retracted for cruise.
Aileron-rudder coupling: when the pilots turn the control wheel, the rudder deflects in the correct direction for a coordinated turn.

Other Control Surfaces

Stabilator: a movable horizontal tail section that combines the action of both the horizontal stabilizer and the elevator.
Variable incidence stabilizer: a horizontal stabilizer with adjustable angle of incidence to minimize drag when trimming the aircraft in flight.
Canards: a small wing or horizontal airfoil ahead of the main lifting surfaces that creates lift and holds the nose up.

Description

Test your knowledge of flight control surfaces in fixed-wing aircraft, including primary and secondary controls, and how they rotate the aircraft around the lateral, longitudinal, and vertical axes. Learn about ailerons and their role in flight control.