In flight simulation, secondary controls are any flight control that is not associated with the primary flying controls of the aircraft, such as:

• Flap position
• Undercarriage or landing gear
• Throttles
• Trim system
• Spoilers
• Speed brake
• Wheel brakes

Flap Position

Wings are provided with flaps¹, articulated sections of the trailing edge of the wing that change the wing characteristics of lift. When the flaps are retracted, the wing generates less lift for a given speed; at the slow speeds needed during the landing phase of flight, the wings would produce insufficient lift without flaps. On landing, the flaps are extended to change the shape of the wing and increase the lift at slower speed. Flaps are often used on take-off. In the cockpit the flap control is usually a lever that can be moved to a variety of discrete detented positions. At their most simple these positions are: Up, Take-off, & Landing.

Undercarriage

All aircraft are equipped with an undercarriage or landing-gear. In some aircraft this gear is fixed, in others it is retractable. Aircraft with retractable gear have a control in the cockpit to raise and lower it, with indicator lights to show the position of the gear and gear doors.

Fixed gear is usual on slow, light aircraft. Retractable gear is normal for high speed heavy aircraft. When extended, the undercarriage creates a lot of aerodynamic drag that reduces the flying efficiency of the aircraft. When the gear retracts, it completely retracts into the body of the aircraft, covered by doors that present a smooth contoured surface when closed.

Throttles

Though engines are important, they are secondary to the primary flying controls. When the engine stops, a pilot still needs to control the aircraft while deciding what to do next. Some aircraft are equipped with automatic throttle control via the autopilot. In single seat or tandem cockpit aircraft, the throttle lever is on a quadrant to the left of the pilot. In large aircraft with side-by-side seating, the throttle quadrant is between the pilot and co-pilot in the the centre console.

Trim System

The trim system makes fine adjustments to the settings of the ailerons, elevators, and rudder. As fuel is consumed, the trim of the aircraft changes. As the speed changes, the trim changes. Strong winds can make keeping the aircraft pointing in the correct direction difficult. These changes in trim can force the pilot to apply constant pressure to the controls in an effort to keep the aircraft pointed properly. A trim system enables the pilot to trim these forces to zero and thus reduce pilot fatigue.

Tabs, very small trailing-edge sections of the ailerons, elevators, and rudder are articulated and moved under control of the trim system. On landing, the pilot must slow the aircraft and raise the nose to control the rate of descent; this is done by pulling back on the joystick or control column, requiring a lot of force; elevator trim enables the pilot to relax backward pressure while maintaining the nose-up attitude.

Modern trim systems are usually electrically actuated. In older aircraft the trim was controlled by trim wheels mechanically connected to the trim tabs. In light, low performance aircraft, trim is accomplished by direct mechanical connections to the trim tabs.

Spoilers

High-speed sub-sonic aircraft are often equipped with devices to spoil the lift of the wing. Spoilers are used to produce rapid descent of the aircraft, they are hydraulically operated panels that extend into the slipstream. Sometimes spoilers are controlled asymmetrically to assist turning of the aircraft.

Speed Brake

Speed brakes do just that, reduce the speed of the aircraft by extending panels into the slipstream. Speed brakes are nearly always used on landing of heavy commercial jet aircraft, deploying automatically when the main gear settles onto the runway. Dive-bombing aircraft use speed brakes to prevent the aircraft from exceeding the airframe speed limit.

Wheel Brakes

Wheel brakes take over on the ground at low taxiing speeds when speed brakes are ineffective. Differential braking is possible to assist turning of the aircraft. Wheel brakes are controlled by the pilot by pressing forward on the tops of the rudder pedals with the toes of the foot. Left toe-brake controls the left wheel brakes in the main gear, right toe-brake the right wheel brakes.