CAA NZ AME Aeroplanes 1 (Subject 4) key terms

The main longitudinal load-bearing member of a wing or stabiliser, designed to carry bending and shear loads from lift or tail forces into the fuselage attachment points.

A transverse structural element that gives an aerofoil its designed cross-sectional shape, supports the skin, and transfers loads between skin, stringers and spar.

A longitudinal stiffening member riveted to the skin and frames, running spanwise or lengthwise, that carries axial and shear loads and stabilises the skin against buckling.

A structural concept in which the skin alone carries the primary loads, with little or no internal framework; efficient in torsion but prone to buckling under compression.

Construction where the skin is supported by frames and stringers so loads are shared between skin and internal structure; the standard approach for pressurised aeroplane fuselages.

A transverse fuselage member that maintains the cross-sectional shape, supports the skin and stringers, and carries concentrated loads such as floor beams and pressure bulkhead reactions.

A sealed transverse structure, typically at the forward and aft ends of the pressurised cabin, that reacts cabin differential pressure and transmits it into the fuselage shell.

A sheet of fuselage or wing skin, often chemically milled or machined to varying thickness, that carries shear, pressure and part of the bending load while forming the aerodynamic surface.

The difference between cabin pressure and ambient pressure at altitude; it loads the fuselage shell in hoop and longitudinal tension and is limited by the aircraft's maximum certified value.

A tank that stores hydraulic fluid, accommodates thermal expansion and pump demand, allows air and contaminants to settle, and is normally pressurised to prevent pump cavitation.

A hydraulic component containing gas behind a piston or bladder that stores pressurised fluid energy, damps pressure surges and supplies a limited reserve for emergency or transient demands.

Formation and collapse of vapour bubbles in hydraulic fluid caused by local pressure falling below vapour pressure, producing noise, erosion and loss of pump performance.

A device that converts mechanical drive into fluid flow; engine-driven pumps are usually variable-displacement axial-piston types, while electric pumps are commonly fixed-displacement gear or piston types.

A pressure-limiting valve that opens to return excess fluid to the reservoir, protecting the system from overpressure if a pump control or pressure regulator fails.

A directional control valve, manually or electrically operated, that routes hydraulic pressure and return flow to extend, retract or hold an actuator such as a landing gear or flap cylinder.

A flow-limiting device that shuts off fluid flow above a set rate, isolating a failed line or component and preserving pressure and fluid for the rest of the system.

An electrically driven pump inside a fuel tank that supplies pressurised fuel to the engine feed line, prevents vapour lock at altitude and provides transfer or scavenge functions.

A condition in which fuel vaporises in lines or pumps, usually at high altitude or high temperature, displacing liquid fuel and causing loss of flow or engine power.

A valve that selects which tank or group of tanks feeds the engine or engines, and may also provide an off position and crossfeed between left and right systems.

A fuel system configuration allowing either engine to draw from tanks on the opposite side, used to balance fuel, extend range after a pump failure or manage an asymmetric fuel load.

An electrical heating element in the pitot tube that prevents ice blockage of the total pressure port, whose failure causes erroneous or frozen airspeed indications.

A flush opening on the fuselage that supplies ambient static pressure to the altimeter, airspeed indicator and vertical speed indicator; blockage or icing causes serious instrument errors.

Compressed air taken from a turbine engine compressor stage and used for cabin pressurisation and air conditioning, wing and engine anti-ice, and engine starting.

The controlled supply of conditioned air to the cabin and regulation of outflow so that cabin altitude and rate of change remain within limits throughout the flight profile.

A motor-driven valve in the pressurised shell that modulates the rate at which cabin air escapes, thereby controlling cabin pressure and cabin altitude.

A unit that regulates generator voltage, monitors frequency, overvoltage, overcurrent and feeder faults, and controls connection and disconnection of the generator to its bus.

A common electrical conductor that distributes power from sources to multiple circuit breakers and loads, and that can be split or isolated to contain faults.

A resettable protective device that opens a circuit automatically on overload, and in aircraft is often thermally actuated and used as a switch for some systems.

External electrical supply equipment connected to the aircraft on the ground to power buses and systems for maintenance, starting and pre-flight checks without using aircraft generators.

A unit that computes airspeed, altitude, vertical speed, Mach number and temperature from pitot and static pressures and temperature inputs, and supplies them to displays and other systems.

A solid-state sensor that converts pitot or static pressure into digital data for the air data computer and other users, replacing long pneumatic lines and mechanical instruments.

A system of gyros and accelerometers, usually with GPS aiding, that provides attitude, heading and rate data to displays and flight control computers without a mechanical vertical gyro.

A self-contained navigation system using laser or fibre-optic gyros and accelerometers to compute position, velocity and attitude, typically aligned on the ground before flight.

A small hinged surface on a primary control that moves in the opposite direction to the main surface, generating an aerodynamic moment that helps the pilot move the control.

A small adjustable surface on a primary flight control used to balance steady stick or pedal forces in a chosen flight condition, reducing pilot workload.

A movable aerofoil such as an aileron, elevator, rudder, flap or spoiler that changes the aerodynamic forces on the aircraft to control attitude or configuration.

A digital computer that processes pilot and sensor inputs and commands actuator movement in fly-by-wire systems, often with multiple channels and built-in redundancy.

A hydraulic, pneumatic or electric device that converts supplied power into linear or rotary motion to move a control surface, flap, gear or valve.

A wheel-speed sensing system that modulates brake pressure to prevent wheel lock and tyre skidding, preserving directional control and minimising stopping distance.

A system that automatically applies a selected level of braking after touchdown or during a rejected take-off, reducing crew workload and giving consistent stopping performance.

The assembly of struts, wheels, tyres and brakes that supports the aircraft on the ground and absorbs landing and taxi loads, usually retractable in cruise.

The main landing gear leg containing an oleo (air-oil) damping element that absorbs touchdown energy and dissipates it, reducing loads into the airframe.

A unit that senses engine or propeller speed and adjusts propeller blade pitch through a pilot valve and pitch-change mechanism to hold a selected rpm.

A propeller whose blade angle is automatically varied by a governor to maintain a selected engine speed as power and airspeed change.

Rotating propeller blades to approximately the flight direction of the relative airflow, minimising drag and windmilling after an engine failure or shutdown.

The static and dynamic correction of mass distribution in a propeller assembly to limit vibration, which otherwise causes fatigue in blades, hub and engine mounts.

The structure of tubes or a forged frame that attaches the powerplant to the airframe, carrying engine loads and isolating them into fuselage or nacelle structure.

A fire-resistant bulkhead separating the engine compartment from the rest of the aircraft, penetrated only by controlled, fireproofed lines and controls.

A mandatory instruction issued by the state of design and adopted by the authority of registry, requiring inspection, modification or limitation to correct an unsafe condition.

A manufacturer-issued document describing recommended inspection, modification or maintenance action; it becomes mandatory only when an airworthiness directive or regulation requires it.

A certification, signed by authorised maintenance personnel, that stated maintenance has been completed and the aircraft or component is fit for return to service within specified limits.

The formal certification that maintenance has been carried out in accordance with applicable requirements and that the aircraft or component may be released to service.

Visual examination of internal engine or structure areas using a fibre-optic or video scope inserted through ports, avoiding disassembly for checks such as compressor blade condition.

Inspection methods such as dye penetrant, magnetic particle, eddy current, ultrasonic and radiographic testing that reveal defects without damaging the part.