NCAA AME Airframe key terms

A stressed-skin fuselage or wing design in which skin carries part of the load but is stiffened internally by stringers, frames and bulkheads, with a smaller number of heavy spars or longerons taking the primary bending loads.

A structural concept in which the outer covering of the aircraft carries aerodynamic and structural loads, usually working together with internal frames and stringers rather than merely enclosing the structure.

A longitudinal stiffening member riveted to the inside of the skin, running spanwise or lengthwise, which carries bending loads with the skin and prevents the skin from buckling between frames.

A heavy transverse structural member that carries concentrated loads, closes a pressure compartment, or provides a hard attachment point for wings, landing gear or empennage fittings.

A transverse hoop-shaped member in a fuselage that maintains the cross-sectional shape, supports stringers and skin, and distributes local loads around the shell.

A main longitudinal structural member of a truss or beam-type fuselage, taking primary bending and tension loads and often serving as the attachment line for fittings and frames.

A fuselage built as a framework of tubes joined in triangles, where members carry tension or compression and the fabric or skin covering is largely non-structural.

A flat plate riveted or bolted at a joint between structural members to transfer load across the connection and to reinforce the junction.

Local out-of-plane deflection of thin skin between its supporting stringers and frames, which may be permitted in some designs but must be controlled to prevent fatigue or permanent deformation.

The centre-to-centre spacing of rivets along a row; it is specified by the manufacturer because incorrect pitch weakens the joint or promotes skin cracking.

The distance from the centre of a fastener to the nearest edge of the material; too small a value allows the fastener to tear out under load.

A permanent mechanical fastener installed by deforming its shank so that it clamps two or more sheets together; common aircraft types include solid, blind and Hi-Lok fasteners.

The process of holding a solid rivet's shop head against a bucking bar while the manufactured head is driven, so the shank expands and fills the hole to form the driven head.

Electrochemical deterioration of a metal caused by environmental attack, dissimilar metal contact, or breakdown of protective coatings; types include galvanic, pitting, exfoliation and stress corrosion.

Corrosion produced when two dissimilar metals are in electrical contact in the presence of an electrolyte, so that the more anodic metal is consumed.

A layered, flaking form of corrosion that attacks the grain structure of rolled or extruded aluminium alloys, often starting at edges, fastener holes or poorly protected surfaces.

Cracking of a metal under the combined action of sustained tensile stress and a corrosive environment, often occurring in high-strength aluminium alloys and stainless steels.

The electrical interconnection of aircraft metallic structure and components to provide a low-resistance return path, reduce static discharge risk and limit galvanic corrosion between dissimilar metals.

A protective coating applied to bare aluminium before paint, providing corrosion inhibition and a key for subsequent topcoat adhesion.

Aluminium sheet or plate clad with a thin layer of commercially pure aluminium, which corrodes preferentially and so protects the stronger alloy core.

Examination of wooden airframe structure for decay, compression failures, glue-line separation and moisture ingress, using visual checks, probing and tap testing.

The bonded connection between wooden members; its strength depends on correct surface preparation, clamping pressure and adhesive, and it is inspected for voids and separation.

The main spanwise beam of a wing or control surface that carries bending and shear loads and to which ribs and skin are attached.

A chordwise member that forms the aerofoil contour, supports the skin, transfers loads to the spar and maintains the wing's shape.

The primary load-carrying structure of a wing formed by front and rear spars, upper and lower skins and ribs, often enclosing an integral fuel tank.

A fuel tank formed by sealing a structural cavity within the wing or fuselage, using sealed seams, fasteners and access panels instead of a separate bladder.

The aircraft system that stores, transfers, vents and delivers fuel to the engines at the required pressure and flow, including tanks, pumps, valves and quantity indication.

A valve that allows the crew to select which tank or tanks supply the engine(s), and which may also provide an OFF position for shutdown or fire control.

A system that transmits power through pressurised fluid to operate actuators for landing gear, brakes, flight controls and other loads, comprising reservoir, pump, valves, lines and actuators.

A tank that stores hydraulic fluid, accommodates thermal expansion and provides a head of fluid to the pump inlet; it is checked for level and pressurisation.

A directional control valve that routes hydraulic pressure to the chosen side of an actuator to extend, retract or hold a component.

The assembly of struts, wheels, brakes and associated mechanisms that supports the aircraft on the ground, absorbs landing loads and permits ground manoeuvring.

An oleo-pneumatic landing gear leg that absorbs landing impact by forcing hydraulic fluid through an orifice while compressing nitrogen, then dissipates the energy on rebound.

A hinged scissor linkage on a landing gear strut that prevents the piston from rotating within the cylinder while still allowing it to slide in and out.

A wheel-speed sensing system that modulates brake pressure to prevent wheel lock and maintain directional control and stopping performance on slippery runways.

The wheel-mounted unit, typically multiple disc, that converts kinetic energy into heat by friction to slow or stop the aircraft.

The system of cables, rods, pulleys, bellcranks, actuators and surfaces by which the pilot controls pitch, roll and yaw, including primary and secondary controls.

The measured preload in a control cable; it must be set within limits to prevent slack, flutter or excessive bearing load, and is checked with a tensiometer.

An adjustable barrel-and-terminal fitting used to set control cable tension, secured after adjustment by lockwire or a locking clip.

A pivoted lever that changes the direction of a control cable or rod and may alter the mechanical advantage within a flight control linkage.

A small hinged surface on a primary control that is deflected to produce a balancing aerodynamic moment, reducing the stick force needed to hold a given attitude.

A tab linked to the fixed structure so that it deflects opposite to the primary control, producing a moment that assists the pilot in moving the surface.

A rigid tubular control member that transmits both tension and compression loads between bellcranks, levers or control surfaces.

The system of pitot tube, static ports, lines and instruments that supplies ram and static pressure for airspeed, altimeter and vertical speed indications.

A forward-facing probe that senses total pressure from the airflow; it must be kept clear of ice, insects and blockage, and its heater checked where fitted.

An opening on the aircraft skin that supplies undisturbed ambient static pressure to the pitot-static instruments; blockage causes erroneous altitude and airspeed readings.

A pressure instrument that displays height above a selected reference by measuring static pressure; it must be set to the correct pressure datum before flight.

A common distribution point that connects a power source to a group of circuits, allowing loads to be supplied and isolated through circuit breakers or fuses.

A resettable protective device that opens a circuit when current exceeds its rating, protecting wiring from overheating and fire.

A small conductive wick fitted to trailing edges that bleeds static electricity from the airframe into the atmosphere, reducing radio interference.

The system that maintains cabin pressure at a selected differential above ambient by controlling outflow, using seals, outflow valves and pressure controllers.

A valve that regulates the rate at which cabin air escapes to atmosphere, thereby controlling cabin altitude and rate of change under the command of the pressure controller.

The difference between cabin pressure and outside ambient pressure; it must not exceed the structural limit of the pressure hull.

A mandatory instruction issued by the state of registry requiring inspection, modification or limitation of an aircraft or component to correct an unsafe condition.

A manufacturer-issued document recommending inspection or modification of a product; it is not automatically mandatory unless made so by an airworthiness directive or operator requirement.

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