Free EASA Part-66 Module 6 Exam Flashcards

The first digit names the principal alloy type (4 is a molybdenum steel) and the second the series within it, so 41xx is the chromium-molybdenum family. The last two digits give carbon content in hundredths of a percent, so 4130 holds about 0.30 percent carbon, and carbon is what decides how hard it will quench.

Annealing cools the part slowly inside the furnace, giving the softest, most machinable result. Normalising cools it in still air, so it stays a little harder and stronger but has a refined, uniform grain. That is why normalising is called up after welding.

Magnetic particle inspection. It needs a ferromagnetic material to create the leakage field that holds the indicating particles over a defect. Aluminium, titanium and austenitic stainless steel have to be checked by dye penetrant or eddy current instead.

Those processes drive atomic hydrogen into the steel, which can cause a delayed brittle fracture under sustained load long after the job is signed off. The bake lets the hydrogen diffuse back out before the part enters service.

2024 is an aluminium-copper alloy and 7075 is aluminium-zinc. The 7000 series reaches higher static strength, while 2024 tolerates damage and fatigue better. That is why skins often use 2024 and heavily loaded machined fittings use 7075.

T3 means solution heat treated, then cold worked, then left to age naturally at room temperature. T6 means solution heat treated and artificially aged in an oven to peak strength. T73 is deliberately overaged, giving up a little strength in exchange for much better resistance to stress-corrosion cracking.

Keep chlorinated solvents, cadmium-plated tools and graphite pencil marks away from it. Chloride residues cause stress-corrosion cracking and cadmium embrittles titanium once the part sees heat, so only approved markers, cleaners and unplated tools are used.

Take an eddy current conductivity reading. Electrical conductivity shifts predictably as the temper changes, so the meter separates a correctly aged part from one that has been overheated or annealed by a fire or a repair.

Anything that does not break the surface. Penetrant works purely by capillary action into an open defect, so it suits aluminium, titanium and magnesium alike but misses subsurface voids, delamination and internal corrosion.

Alclad has a thin layer of nearly pure aluminium rolled onto each face, which corrodes sacrificially to protect the alloy core. Sanding through that layer exposes the core and the panel permanently loses its built-in protection.

Carbon gives the highest stiffness and strength for its weight. Glass is cheaper and electrically insulating. Aramid resists impact and abrasion but is weak in compression and absorbs moisture, so it is rarely used alone in a loaded skin.

A thermoset cures by an irreversible chemical reaction and cannot be remelted, so a repair needs fresh resin and a controlled cure cycle. A thermoplastic softens again on heating, which allows reforming and fusion welding.

The core holds two thin face sheets far apart, and those faces carry the bending load in tension and compression at a large distance from the neutral axis. The core itself only has to carry shear and keep the faces spaced.

A change in sound where the skin is no longer bonded to whatever lies beneath it. A sharp ring means sound structure and a dull, flat note marks a delamination or disbond near the surface.

Delamination separates plies within a single laminate. Disbond separates two joined parts, such as a skin from its honeycomb core or a doubler from a skin. Neither shows from outside, so both are found by tap test or ultrasonics.

It corrodes an aluminium core, attacks the adhesive bond line and can freeze at altitude, forcing the cells apart. It also reads on tap test and ultrasonics much like a disbond, which complicates the assessment.

Each ply carries load mainly along its own fibre direction, so the stack is engineered as a set of directions rather than a thickness. A ply laid at the wrong angle leaves that direction under-strength however many plies you add.

Sitka spruce. Other species are compared against it for strength and density, and a substitution is only acceptable where the approved data lists that species as equivalent or better for the member being replaced.

Wood is far stronger along the grain than across it, so grain running out at an angle turns a tension load into a splitting load. Approved data therefore caps the slope of grain; FAA AC 43.13-1B allows spruce no more than 1 in 15.

Ultraviolet light and ageing weaken the fibres long before the surface looks bad, and the dope finish hides the deterioration. A punch or pull test on the fabric is what decides whether the covering may stay in service.

Aerodynamic suction tries to lift the covering off the ribs in flight. The lacing carries that load into the rib; relying on the dope film alone would let the fabric balloon and the covering would fail progressively.

An anode, a cathode, an electrolyte joining them and a metallic path between them. Remove any one and corrosion stops, which is exactly how sealing, draining and insulating schemes are designed to work.

Chromate conversion coating. Anodising grows a much thicker oxide film that insulates, so bonding and earthing faces are conversion coated instead to keep the electrical path intact.

It needs two dissimilar metals in electrical contact with a shared electrolyte. The less noble metal then corrodes far faster than it would alone, which is why carbon fibre laid against aluminium is such a persistent problem.

As lifting and flaking layers. It is intergranular corrosion in a rolled or extruded product whose grains are long and flat, and the corrosion product occupies more volume than the metal it replaced, so the layers are forced apart.

A tensile stress that stays applied, whether from service load or locked-in residual stress; an environment that attacks the metal; and an alloy that is susceptible to it. Remove any one and the cracking stops, which is why overaged tempers and shot peening are specified on parts known to be at risk.

Where there is little material to grip or where vibration is a concern. A fine thread puts more engaged thread into the same length and resists loosening. Coarse threads assemble faster and cope better with soft, damaged or corroded material.

How tight the tolerance is between the mating threads: A marks an external thread and B an internal one. A higher class number means less clearance and a more precise fit, which matters where the joint must locate accurately or seal against pressure.

The thread root is a smaller diameter and a stress raiser, so the bolt would be sheared at its weakest section. The plain shank has to span the joint, and washers are used to adjust the grip rather than running threads through.

A joint that carries reversing or vibrating loads. Its shank is machined to fit the hole with almost no clearance, so the joint cannot work back and forth and hammer the holes oval over time.

A bolt has a defined unthreaded grip, is tightened by its nut and carries shear across that plain shank. A screw is usually threaded close to the head, is held to a lower strength standard and often drives into a tapped hole or anchor nut.

Most of the torque you apply is swallowed by friction rather than becoming bolt tension. Lubricating a thread that was specified dry sends far more of it into stretching the bolt, which can yield or fail it at the book figure.

On any joint where the bolt or nut itself turns in service, such as a hinge or clevis pin in a control linkage; rotation wears away the friction that provides the lock, so those joints take a castellated nut with a split pin. A pulley bolt may use one only when the nut clamps the bearing inner race so the bolt cannot turn.

A plain head is 1100 (A), a dimple is 2117 (AD), a single raised teat is 2017 (D) and a raised double dash is 2024 (DD). The marking gives you the alloy, which sets both the shear strength and whether heat treatment is needed.

After solution treatment they age-harden at room temperature and become too hard to drive without cracking the head. Refrigeration suspends that ageing, and once removed they must be driven inside the stated time limit or re-heat-treated.

So the system is still identifiable when the colour has faded, the bay is badly lit or the technician is colour blind. The tape carries the system name, a colour band and a geometric symbol together for that reason.

37 degrees. Common industrial flare fittings use 45 degrees, and mating a 37 degree cone into a 45 degree seat gives line contact instead of face contact, so the joint leaks and the flare eventually cracks.

It is a conical disc spring that delivers a high load over a very small deflection in very little space. Stacking them in the same direction raises the load, and alternating them raises the available travel.

Evenly spaced indentations in a race where the rolling elements sat during a static shock load, typically a heavy landing or a bearing driven in through the wrong ring. It is damage rather than wear, so the bearing is scrapped.

Spalling is fatigue flaking of a race or element surface after many load cycles, so it spreads progressively and roughens the running surface. Brinelling is a single overload indentation. Only spalling gives warning as rising noise and vibration.

Pressing on the other ring drives the load through the balls or rollers and brinells both races. The force has to pass only through the ring being fitted, never through the rolling elements.

Divide the teeth on the driven gear by the teeth on the driving gear. Sixty driven over twenty driving is 3 to 1, so the output turns at a third of the speed and carries roughly three times the torque, less losses.

Only the direction the output turns, plus the centre distance the train can span. It does not alter the overall ratio, because its tooth count appears in both meshes and cancels out.

Where the cable bends repeatedly around pulleys, which is typical of a primary flight control run. 7x19 uses more and finer wires, so it flexes with far less fatigue. 7x7 is stiffer and suits straighter, less worked runs.

No more than three on either terminal. Any more means too little thread is engaged inside the barrel, so the assembly cannot carry the rated cable load.

It holds control cable tension roughly constant as temperature changes. An aluminium airframe expands about twice as much as the steel cables, so without it the cables would slacken when hot and over-tighten when cold.

No, the opposite. A higher AWG number is a thinner conductor, so 22 AWG is smaller than 12 AWG. Undersizing a run causes voltage drop and overheating, so gauge is chosen from current and cable length together.

A shield on audio or low-frequency signal wiring is earthed at a single point so that no ground loop can circulate current and inject hum into the signal. A shield fitted for HIRF or lightning protection, or an RF coaxial screen, is bonded at both ends so induced current goes straight to structure. Follow the wiring manual for each cable.

A correct crimp is a gas-tight cold joint made with a controlled tool, so there is no heat-affected zone and no solder wicking into the strands. Wicked solder stiffens the wire exactly where it flexes, and it fails there.

Its characteristic impedance must suit the equipment and the antenna, commonly 50 ohms in aircraft communication and navigation installations. A mismatch reflects power back down the line instead of radiating it, showing as a high standing wave ratio.