NCAA AME Airframe flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Limit load

The maximum load expected in normal service operation. Structure must support limit load without permanent deformation, and ultimate load is set at 1.5 times this value.

Ultimate load

Limit load multiplied by the safety factor of 1.5. The structure must withstand ultimate load for at least three seconds without failure, although permanent deformation is permitted.

Primary structure

Structure whose failure would endanger the aircraft, such as spars, wing skins, pressure bulkheads and fuselage frames. Repairs require approved data and certified sign-off.

Secondary structure

Structure that carries only aerodynamic or minor local loads, such as fairings, cowlings and floor panels. Damage limits are defined in the Structural Repair Manual.

Fail-safe design

A design philosophy where redundant load paths or crack-stopping features allow damage to be detected before it becomes critical. Requires mandated inspection programmes.

Safe-life design

A design philosophy where a component is retired after a calculated fatigue life before cracks can initiate. No inspection for cracks is relied upon.

Exfoliation corrosion

Corrosion that follows grain boundaries parallel to the surface, lifting metal into flakes or layers. Common in extruded and rolled sections, it needs structural assessment rather than simple blending.

Galvanic corrosion

Corrosion caused by electrical contact between dissimilar metals in the presence of an electrolyte. Carbon fibre and aluminium are a classic pair requiring isolation barriers.

Stress corrosion cracking

Cracking that results from the combined action of a sustained tensile stress and a corrosive environment. Often appears as branching cracks in high-strength alloys or landing gear components.

Alclad sheet

Aluminium alloy sheet clad with a thin layer of commercially pure aluminium. The cladding corrodes sacrificially to protect the stronger alloy core from corrosion.

Rivet edge distance

The distance from the centre of a rivet hole to the nearest edge of the sheet. It is normally at least twice the rivet diameter to prevent tear-out under load.

Rivet pitch

The centre-to-centre spacing between adjacent rivets in a row. Typical values range from four to six rivet diameters, set by the SRM for each joint.

Mass balance weight

A weight fitted to a control surface to move its centre of gravity ahead of the hinge line, preventing flutter. It must be restored after painting or repair.

Cable tension check

A rigging check using a tensiometer to confirm control cables are within the temperature-corrected tension range in the maintenance manual, preventing slack or overstress.

CPCP

Corrosion Prevention and Control Programme. A scheduled inspection regime targeting known corrosion-prone areas, with findings beyond limits escalated to structural evaluation.

Allowable damage limit

The maximum damage size that may be blended out or left unrepaired per the Structural Repair Manual, beyond which an approved repair is mandatory.

Lightning strike protection

A conductive mesh or foil layer on composite structure that dissipates lightning current. After a strike, delamination is checked by tap test or NDT.

Hydraulic relief valve

A valve that limits system pressure by bypassing fluid back to return, set below the proof pressure of components to prevent damage from overpressure.

Pressurized reservoir

A hydraulic reservoir pressurized by bleed air or a spring to maintain positive inlet pressure at the pump, preventing cavitation at altitude.

Weight and balance envelope

The certified range of aircraft weight and centre of gravity within which flight is permitted. It must be re-established after major repair or modification.

Airworthiness directive

A mandatory instruction issued by the authority to correct an unsafe condition. It must be accomplished within the stated compliance time and recorded in the maintenance records.

Bonding resistance check

A measurement confirming low electrical resistance between aircraft structure and designated points, ensuring static discharge and lightning current paths before refuelling.

Tear strap

A circumferential or longitudinal reinforcing member bonded or riveted to skin that stops a running crack, a key feature of damage-tolerant fuselage design.

Stringer

A longitudinal stiffening member attached to skin or frames that carries bending loads and helps arrest cracks. Often secondary but can be primary in wing structure.

Bulkhead

A transverse structural member that carries concentrated loads or closes a pressure compartment. Pressure bulkheads are primary structure and repairs need approved data.

Zinc-rich primer

A protective coating applied to aluminium and steel that corrodes sacrificially to protect the base metal. Applied before topcoat in corrosion-prone areas.

Faying surface

The mating surface between two joined parts, such as skin and stringer. It traps moisture and is a prime corrosion site, so it is sealed during assembly.

Delamination

Separation between layers of composite laminate, often caused by impact or lightning. Detected by tap test or ultrasonic inspection before repair per SRM.

Control surface travel check

A rigging verification that each control surface moves through its specified angular range in both directions, with correct stops and no binding, per the maintenance manual.

Pitot-static system leak check

A test pressurizing the pitot and static lines to confirm no leakage, ensuring accurate airspeed, altitude and vertical speed indications after system disturbance.

Fuel tank inerting

A system that replaces oxygen in the ullage with nitrogen-rich air to reduce flammability. Its operation and servicing are part of fuel system maintenance.

Empty weight

The weight of the aircraft including structure, powerplant, fixed equipment and unusable fuel and oil. It is re-weighed after major modification and used for CG calculation.