FAA A&P Mechanic key terms

A mandatory FAA rule issued when an unsafe condition is found in a type-certificated product. It specifies required inspections or modifications and must be complied with and recorded before further flight.

FAA approval of the design of an aircraft, engine, or propeller that meets the applicable airworthiness standards. It establishes the approved configuration against which later alterations and repairs are judged.

FAA form used to document a major repair or major alteration and to approve the aircraft for return to service. It identifies the work performed and the approved data relied upon.

An FAA publication giving nonregulatory guidance, acceptable methods, and procedures for meeting regulations. AC 43.13-1B, for example, describes acceptable methods and practices for aircraft repair.

A manufacturer's notice recommending inspection, modification, or part replacement on its product. It becomes mandatory only when the FAA issues an Airworthiness Directive requiring compliance.

FAA approval for a manufacturer to produce replacement parts for type-certificated products. The holder must show the part is identical to, or a suitable replacement for, the original.

A twisting force applied to a fastener, measured in pound-inches or pound-feet. Correct torque stretches the fastener and clamps the joint so it resists vibration and loosening.

A locking method in which soft stainless wire is threaded through fastener holes and twisted so any loosening pulls the wire tight. It is installed with the correct pull direction and pigtail.

Inspection methods such as dye penetrant, magnetic particle, eddy current, ultrasonic, and radiographic testing that find defects without damaging the part. Selection depends on material and the flaw being sought.

Corrosion caused by electrical contact between dissimilar metals in the presence of an electrolyte. The less noble metal becomes anodic and wastes away; isolation and protective finishes prevent it.

The computation confirming that loaded weight and center of gravity fall within approved limits. Out-of-limit loading reduces performance and controllability and can overstress structure.

Regulations governing aircraft maintenance, preventive maintenance, rebuilding, and alteration. They define who may perform and approve work and what records must be made.

Regulations for certifying airmen other than flight crew, including mechanics and repairmen. They set experience requirements and the privileges and limitations of a mechanic certificate.

Twelve commonly cited error precursors in maintenance, such as fatigue, complacency, distraction, and poor communication. Recognizing them helps technicians build defenses against mistakes.

A stressed-skin structure where the skin carries shear and tension while stringers, frames, and bulkheads stiffen it and carry bending loads. It is the usual construction for modern fuselages and wings.

A longitudinal member fastened to the skin that stiffens it and helps carry bending loads. Stringers run spanwise in wings and lengthwise along a fuselage.

A chordwise member that gives an airfoil its shape and supports the skin and stringers. Ribs transfer aerodynamic loads to the spar.

The main spanwise beam of a wing or stabilizer that carries bending and shear loads. It is usually built from caps and a web and is a critical inspection item.

A transverse structural member that shapes the fuselage and carries concentrated loads from fittings such as wing attachments or landing gear. Pressurized aircraft use bulkheads as pressure boundaries.

The tail assembly of an aircraft, comprising the horizontal and vertical stabilizers and their control surfaces. It provides stability and pitch and yaw control.

The hinged control surface on the horizontal stabilizer that controls pitch. Deflecting it changes tail downforce and rotates the aircraft about its lateral axis.

A landing gear shock absorber that uses compressed gas as a spring and hydraulic fluid forced through an orifice as a damper. It absorbs landing loads and damps rebound.

A pressure vessel holding gas separated from hydraulic fluid by a bladder, diaphragm, or piston. It stores energy for peak demands and smooths pressure surges and pump pulsation.

A valve that controls how fast air leaves a pressurized cabin, thereby setting cabin altitude and pressure differential. It works with the pressure controller and cabin safety valves.

An inflatable rubber strip bonded to a leading edge that expands to crack and shed accumulated ice. Boots are cycled by a pneumatic system when icing conditions are encountered.

The rigging value measured with a tensiometer that keeps a control cable taut without overloading structure. It is set with turnbuckles and corrected for temperature at the time of measurement.

A chemical treatment that forms a thin, conductive, corrosion-resistant film on aluminum and improves paint adhesion. It is applied after cleaning and before priming.

The intake, compression, power, and exhaust sequence that a reciprocating engine cylinder repeats every two crankshaft revolutions. Each cylinder produces one power stroke per cycle.

A self-contained, engine-driven ignition unit that generates its own high voltage. Aircraft engines use two independent magnetos for redundancy, and both must be grounded to stop the engine.

A cylinder leakage check in which regulated air is applied at top dead center and the pressure held is compared with the input. Low readings indicate leaking rings, valves, or head gaskets.

A valve that routes exhaust gas around the turbine to control boost. It opens to limit manifold pressure and closes as altitude increases to maintain the scheduled power.

A propeller whose blade angle is changed automatically by a governor to hold a selected engine RPM as load varies. This lets the engine run at efficient settings for takeoff and cruise.

A unit that senses engine speed and meters oil pressure to the propeller hub to change blade angle. Flyweights balanced against a speeder spring hold the selected RPM.

A breakdown of airflow through a turbine compressor that causes a bang, power loss, and possible overtemperature. Causes include abrupt throttle movement, foreign object damage, and distorted inlet air.

A turbine engine indication of exhaust gas temperature leaving the engine, used to set power and monitor limits. Abnormally high values warn of overtemperature or hot-section distress.

The unit that meters fuel to a turbine engine according to throttle position, compressor speed, and ambient conditions. It schedules acceleration fuel and protects against overspeed and overtemperature.

The gap between the rocker arm and the valve stem that allows for thermal expansion. It is measured with a feeler gauge and set to the manufacturer's cold-engine specification.

A small turbine engine that supplies electrical power and bleed air, usually on the ground. It has its own starting, fuel, oil, and control systems and is not used for propulsion.