Part-66 Module 6 flashcards

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

Austenitic stainless steel

Non-magnetic chromium-nickel steels that cannot be hardened by heat treatment, only by cold work, and are susceptible to intergranular corrosion after heating between 425 and 870 °C.

Sensitisation of stainless steel

Chromium carbide precipitation at grain boundaries when austenitic stainless steel is held at 425–870 °C, depleting chromium locally and causing intergranular corrosion; stabilised grades 321 and 347 resist it.

Tempering

Reheating hardened steel to below the lower critical temperature to relieve internal stress and reduce brittleness, trading some hardness and strength for improved toughness and ductility.

2024 aluminium alloy

Copper-bearing aluminium alloy with high strength and fatigue resistance but poor corrosion resistance, usually clad with pure aluminium (Alclad) when used for aircraft skins.

7075 aluminium alloy

Zinc-magnesium-copper alloy, one of the highest-strength aluminium alloys, used for highly stressed structures; it is notch sensitive and prone to exfoliation and stress corrosion, so it is always protected.

Solution heat treatment

Heating an alloy to a temperature that dissolves the alloying elements into solid solution, then quenching rapidly to retain a supersaturated solid solution before ageing.

Delamination

Separation between plies of a laminated composite, typically caused by impact, voids or poor cure; detected by tap testing or ultrasonic inspection and seriously reducing compressive strength.

Aramid fibre

Para-aramid (Kevlar) fibre with high tensile strength and impact resistance but low compressive strength; it absorbs moisture and fuzzes when cut or machined.

Lightning strike protection

Fine aluminium or copper mesh, or a conductive filled coating, embedded in the outer ply of a composite structure to conduct lightning current and prevent resin damage.

Galvanic corrosion

Corrosion caused by electrical contact between dissimilar metals in the presence of an electrolyte, in which the more anodic metal corrodes, accelerated by a large cathode-to-anode area ratio.

Stress corrosion cracking

Cracking produced by the combined action of tensile stress and a specific corrosive environment, often along grain boundaries; seen in high-strength aluminium and stainless steels.

Exfoliation corrosion

Corrosion that spreads along grain boundaries parallel to the surface, forcing layers of metal apart; typical of 7075 aluminium and prevented by cladding and protective finishes.

Grip length

The thickness of material a fastener clamps, measured from under the head to the start of the thread; it must be selected so the nut engages the correct number of full threads.

Edge distance

The distance from the centre of a fastener hole to the nearest edge of the part, normally at least two hole diameters to prevent tear-out under load.

Hi-Lok fastener

Two-piece fastener with a threaded pin and a frangible-collar nut; the collar shears at a designed torque so a consistent preload is obtained without a torque wrench.

Flareless fitting

Tube fitting in which a ferrule is swaged onto the tube by the nut, requiring no flaring; used in high-pressure hydraulic systems and reassembled only a limited number of times.

37-degree flared tube

Standard aircraft rigid tube end where the tube is flared at 37 degrees to mate with a flared fitting cone; the flare must be smooth, concentric and free of cracks.

Flexible hose

Hose of rubber or PTFE with braided reinforcement, used where vibration or relative movement prevents rigid tubing; it must be supported and installed within its minimum bend radius.

Spring rate

The load required to deflect a spring by unit distance; for a helical spring k = Gd⁴/(8D³N), so the rate falls as the number of active coils increases.

Shot peening

Bombarding a spring surface with small media to induce compressive residual stress, improving fatigue life by counteracting the tensile stress at the surface.

Spring set (scragging)

Preloading a spring beyond its working stress to produce controlled permanent deformation, stabilising its free length so that it does not change in service.

Brinelling

Permanent indentation of a bearing raceway caused by static overload or by impact while the bearing is stationary, producing vibration and early failure once rotation begins.

Tapered roller bearing

Bearing with conical rollers and raceways that carries combined radial and thrust load in one direction; mounted in opposed pairs and requiring preload or clearance adjustment.

Backlash

The clearance between mating gear teeth that allows lubrication and thermal expansion; too little causes overheating and seizure, too much causes impact noise and wear.

Swaged cable terminal

End fitting attached to a control cable by cold pressing with a specified tool and die; the completed assembly is gauge-checked and proof-loaded and inspected for wire slippage.

Turnbuckle

Threaded barrel connecting two cable terminals, one with a right-hand and one with a left-hand thread, used to adjust control cable tension and rigging.

Cable proof load

A specified tensile load applied to a completed cable assembly to verify terminal security, applied before installation and below the design breaking load.

7x19 cable

Stranded control cable made of seven strands of nineteen wires each, giving high flexibility for runs passing over pulleys, unlike the stiffer 1x19 construction.

Wire gauge (AWG)

Numbering system in which a smaller AWG number denotes a larger conductor cross-section, with lower resistance and higher current-carrying capacity.

Crimped terminal

Electrical connection made by mechanically deforming a terminal onto a conductor with a calibrated tool; reliability depends on correct tool and die selection and a pull test.

Coaxial cable

Cable with a central conductor surrounded by dielectric, a braided shield and an outer jacket, carrying high-frequency signals while shielding them from electromagnetic interference.

Bonding

Electrically connecting aircraft structure and components to provide a low-resistance return path for current, preventing static build-up, arcing and interference.