Aircraft Systems 2 Lesson 4 TDF

Aborted takeoff

A takeoff that is terminated prematurely when it is determined that some condition exists that makes takeoff or further flight dangerous.

Amphibian

An aircraft with a landing gear that allows it to operate from both water and land surfaces.

Antiskid system

An electrohydraulic system in an airplane’s power brake system that senses the deceleration rate of every main landing gear wheel.

Automatic adjuster

A subsystem in an aircraft disk brake that compensates for disk or lining wear. Each time the brakes are applied, the automatic adjuster is reset for zero clearance, and when the brakes are released, the clearance between the disks or the disk and lining is returned to a preset value.

Backplate

A floating plate on which the wheel cylinder and the brake shoes attach on an energizing-type brake. bead (tire component). The high-strength carbon-steel wire bundles that give an aircraft tire its strength and stiffness where it mounts on the wheel.

Bead seat area

The flat surface on the inside of the rim of an aircraft wheel on which the bead of the tire seats.

Bleeding of brakes

The maintenance procedure of removing air entrapped in hydraulic fluid in the brakes. Fluid is bled from the brake system until fluid with no bubbles flows out.

Bungee shock cord

A cushioning material used with the non-shock absorbing landing gears installed on older aircraft. Bungee cord is made up of many small rubber bands encased in a loose-woven cotton braid.

Camber (wheel alignment)

The amount the wheels of an aircraft are tilted, or inclined, from the vertical. If the top of the wheel tilts outward, the camber is positive. If the top of the wheel tilts inward, the camber is negative.

Carcass (tire component)

The layers of rubberized fabric that make up the body of an aircraft tire.

Centering cam

A cam in the nose-gear shock strut that causes the piston to center when the strut fully extends. When the aircraft takes off and the strut extends, the wheel is straightened in its fore-and-aft position so it can be retracted into the wheel well.

Compensator port

A small hole between a hydraulic brake master cylinder and the reservoir.

Deflator cap

A cap for a tire, strut, or accumulator air valve that, when screwed onto the valve, depresses the valve stem and allows the air to escape safely through a hole in the side of the cap.

Dragging brakes

Brakes that do not fully release when the brake pedal is released. The brakes are partially applied all the time, which causes excessive lining wear and heat.

Energizing brake

A brake that uses the momentum of the aircraft to increase its effectiveness by wedging the shoe against the brake drum.

Expander tube brake

A brake that uses hydraulic fluid inside a synthetic rubber tube around the brake hub to force rectangular blocks of brake-lining material against the rotating brake drum. Friction between the brake drum and the lining material slows the aircraft.

Fading of brakes

The decrease in the amount of braking action that occurs with some types of brakes that are applied for a long period of time.

Fusible plugs

Plugs in the wheels of high performance airplanes that use tubeless tires.

Hydroplaning

A condition that exists when a high-speed airplane is landed on a water-covered runway.

Multiple-disk brakes

Aircraft brakes in which one set of disks is keyed to the axle and remains stationary.

Nonenergizing brake

A brake that does not use the momentum of the aircraft to increase the friction.

Oleo shock absorber

A shock absorber used on aircraft landing gear.

Ozone

An unstable form of oxygen produced when an electric spark passes through the air. Ozone is harmful to rubber products.

Ply rating

The rating of an aircraft tire that indicates its relative strength. The ply rating does not indicate the actual number of plies of fabric in the tire; rather it indicates the number of plies of cotton fabric needed to produce the same strength as the actual plies.

Pressure plate

A strong, heavy plate used in a multiple-disk brake. The pressure plate receives the force from the brake cylinders and transmits this force to the disks.

Retread

The replacement of the tread rubber on an aircraft tire.

Scissors

A name commonly used for torque links. See torque links.

Segmented-rotor brake

A heavy-duty, multiple-disk brake used on large, high-speed aircraft. Stators that are surfaced with a material that retains its friction characteristics at high temperatures are keyed to the axle. Rotors which are keyed into the wheels mesh with the stators. The rotors are made in segments to allow for cooling and for their large amounts of expansion.

Shimmy damper

A small hydraulic shock absorber installed between the nosewheel fork and the nosewheel cylinder attached to the aircraft structure.

Shimmy

Abnormal, and often violent, vibration of the nose wheel of an airplane. Shimmying is usually caused by looseness of the nose wheel support mechanism, but may also be caused by tire imbalance.

Shuttle valve

A type of hydraulic valve mounted on the landing gear and brake actuator cylinders.

Single-disk brakes

Aircraft brakes in which a single steel disk rotates with the wheel between two brake-lining blocks. When the brake is applied, the disk is clamped tightly between the lining blocks, and the friction slows the aircraft.

Single-servo brake

A brake that uses the momentum of the aircraft rolling forward to help apply the brakes by wedging the brake shoe against the brake drum.

Slippage mark

A paint mark that extends across the edge of an aircraft wheel onto a tube-type tire. When this mark is broken, it indicates that the tire has slipped on the wheel, and there is good reason to believe that the tube has been damaged.

Spongy brakes

Hydraulic brakes whose pedal has a spongy feel because of air trapped in the fluid.

Squat switch

An electrical switch actuated by the landing gear scissors on the oleo strut. When no weight is on the landing gear, the oleo piston is extended and the switch is in one position, but when weight is on the gear, the oleo strut compresses and the switch changes its position.

Stress riser

A location where the cross sectional area of the part changes abruptly. Stresses concentrate at such a location and failure is likely. A scratch, gouge, or tool mark in the surface of a highly stressed part can change the area enough to concentrate the stresses and become a stress riser.

Toe-in

A condition of landing gear alignment in which the front of the tires are closer together than the rear. When the aircraft rolls forward, the wheels try to move closer together.

Toe-out

A condition of landing gear alignment in which the front of the tires are farther apart than the rear. When the aircraft rolls forward, the wheels try to move farther apart.

Torque links

The hinged link between the piston and cylinder of an oleo-type landing gear shock absorber.

Trunnion

Projections from the cylinder of a retractable landing gear strut about which the strut pivots to retract.