FAA Aviation Mechanic - Airframe (AMA) cheat sheet

Primary structure includes wings, fuselage, empennage, and landing-gear attachments; failure would endanger flight safety.

Secondary structure includes fairings, wheel wells, and access panels; failure does not immediately endanger flight.

Stress = load ÷ cross-sectional area; strain = deformation ÷ original length.

Limit load is the maximum expected service load; ultimate load = limit load × 1.5, the factor of safety.

Tension pulls apart, compression pushes together, shear slides layers, bending combines tension and compression, and torsion twists.

A compression member can fail by buckling before reaching its crushing strength; slenderness increases buckling risk.

Sheet-metal bend allowance = neutral-axis arc length, based on bend angle, radius, thickness, and K-factor.

Typical minimum rivet edge distance is two rivet diameters from rivet center to sheet edge, unless the repair document specifies otherwise.

Composite delamination is detected by tap test, ultrasonic inspection, or visual swelling and cracking.

Pascal's law: pressure applied to a confined fluid is transmitted equally; force = pressure × piston area.

MIL-PRF-5606 and MIL-PRF-83282 hydraulic fluids are red; Skydrol phosphate-ester fluid is purple and uses compatible seals.

Ohm's law: E = I × R; DC power: P = E × I.

Series circuit: current is the same, voltage drops add; parallel circuit: voltage is the same, branch currents add.

Pitot pressure plus static pressure drives the airspeed indicator; the altimeter and VSI use static pressure.

The cabin outflow valve regulates air leaving the pressurized fuselage and controls cabin altitude and rate of change.

Torque links keep the landing-gear wheel aligned with the strut; shimmy dampers absorb rapid wheel oscillation.

Pneumatic deice boots remove ice after formation; thermal anti-ice prevents or limits ice formation on protected surfaces.

Fuel tank sump drains remove water and sediment; fuel vents prevent tank overpressure or vacuum.

Annual inspection is due every 12 calendar months; a 100-hour inspection is due within 100 hours of flight time for hire or flight-instruction aircraft.

Airworthiness Directives are mandatory; compliance is recorded and required before return to service.

FAA Form 337 records major repairs or alterations and is carried aboard the aircraft.

Dye penetrant finds surface cracks in nonporous materials; magnetic particle finds surface and near-surface cracks in ferrous metals.

Eddy current finds cracks and corrosion in conductive materials such as aluminum; ultrasonic finds internal flaws and delamination.

A borescope provides internal visual inspection through small access ports without major disassembly.

Corrosion indicators include blistered paint, discoloration, rivet staining, and powdery deposits.

Service bulletins are manufacturer recommendations and are not mandatory unless an AD or operator requirement makes them so.

A progressive inspection is an FAA-approved program that divides inspection items into scheduled segments.