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Module 6 Materials and hardware: 50 practice questions

Real EASA paper: Category A 52 Q / 65 min · B1.1 80 Q / 100 min · B1.2 80 Q / 100 min · B1.3 80 Q / 100 min · B2 60 Q / 75 min · B2L 60 Q / 75 min · B3 80 Q / 100 min. Three options, 75% to pass. Answer key on the last page. From part66exam.com · independent study aid, not an official exam or a past paper.

1. Pulse-echo ultrasonic inspection of a composite has the advantage that it:
1. A. needs no couplant
2. B. works only on sandwich panels
3. C. needs access to one side only
2. On a wing, in which direction should the major axis of an elliptical corrosion dish-out run?
1. A. Spanwise
2. B. Chordwise
3. C. Diagonally at 45°
3. In AN bolt numbering, the length code '12' means:
1. A. 12/16 in (0.75 in)
2. B. 1 2/8 in (1.25 in)
3. C. 12/8 in (1.5 in)
4. How is moisture kept from entering the rear of an environment-resistant connector?
1. A. Fill the rear with general-purpose grease
2. B. Match wire outside diameter to the grommet sealing range
3. C. Wrap the backshell with adhesive tape
5. A rack and pinion converts:
1. A. linear motion into faster rotary motion only
2. B. high torque into high voltage
3. C. rotary motion into linear motion
6. A dark powder is seen leaking from around rivets in a joint that flexes in flight ('smoking rivets'). The likely cause is:
1. A. filiform corrosion under the paint
2. B. microbial contamination of the joint
3. C. fretting corrosion from small relative movement
7. Metal tubing size is specified by:
1. A. outside diameter and wall thickness
2. B. inside diameter of the bore only
3. C. mass per metre of tube length
8. The Charpy and Izod tests measure a material's:
1. A. static hardness, as depth of indentation
2. B. impact toughness, as energy absorbed by a notched specimen
3. C. fatigue strength, as cycles to failure
9. Cast aluminium bronze is used for bearings and pump parts because it:
1. A. is lighter than magnesium and titanium alloys
2. B. has strength and ductility and resists corrosion and fatigue
3. C. lubricates itself with embedded graphite flakes
10. A spring that is loaded beyond its elastic limit will:
1. A. take a permanent set and not return to its free length
2. B. become stiffer and return to a longer free length
3. C. always fracture immediately
11. What component is used where a control cable changes direction significantly?
1. A. A pulley
2. B. A fairlead
3. C. A pressure seal
12. Aramid (Kevlar-type) fibre composites are characterised by:
1. A. high stiffness and good electrical conductivity
2. B. high tensile strength but poor compressive strength
3. C. high compressive strength and brittleness
13. In the four-digit wrought aluminium alloy system, the 2xxx series has which main alloying element?
1. A. Copper
2. B. Zinc
3. C. Magnesium
14. Aluminium alloy nuts are NOT used on seaplanes with steel bolts because:
1. A. they cannot carry any shear loads
2. B. of the higher dissimilar-metal corrosion risk
3. C. they are heavier than steel nuts
15. The voltage drop in the main power wires from the generator or battery to the bus should not exceed:
1. A. 10 % of the regulated voltage
2. B. 2 % of the regulated voltage
3. C. 0.2 % of the regulated voltage
16. In some planetary reduction gears, the bell gear is on the propeller shaft and the pinion cage is held fixed. What is the result?
1. A. Propeller turns with the crankshaft, same speed
2. B. Propeller turns opposite to the crankshaft, reduced speed
3. C. Propeller is locked stationary
17. Fatigue corrosion failure occurs in two stages. What happens in the second stage?
1. A. The pits fill with oxide and stop growing
2. B. Cracks grow by fatigue even if corrosion stops
3. C. The part heals once dried and painted
18. A bulkhead union fitting is used to:
1. A. join two hoses without any clamps
2. B. reduce the pressure in the line
3. C. carry a line through a bulkhead
19. Why are austenitic stainless steels such as 18-8 NOT hardened by heat treatment?
1. A. They do not form martensite on quenching
2. B. They melt below the hardening temperature
3. C. They contain too much carbon
20. A cylindrical roller bearing compared with a ball bearing of the same size can carry:
1. A. a greater thrust load
2. B. a greater radial load
3. C. more shaft misalignment
21. A helical compression spring is designed to:
1. A. shorten under load and push back on the parts it separates
2. B. lengthen under load and pull its ends together
3. C. twist about its axis to store torque
22. Why are cable tension regulators fitted on large aircraft?
1. A. To hold tension as the structure expands
2. B. To limit the travel of control surfaces
3. C. To damp flutter of the control surface
23. Why are non-tautening sealers or dopes used on polyester fabric?
1. A. Polyester cannot absorb any liquid coating
2. B. Tautening dope blocks the UV fillers
3. C. Tautening dope could overstress the airframe
24. Pitting corrosion has been removed from an aluminium skin. What must be checked before refinishing?
1. A. That the blend-out is within the damage limits
2. B. That the surface now responds to a magnet
3. C. That the Barcol reading has doubled
25. Which thread diameter determines the fit between a nut and a bolt?
1. A. The pitch (effective) diameter
2. B. The major (crest) diameter
3. C. The minor (root) diameter
26. Polyimide (Kapton-type) wire insulation is thin and tough, but its main disadvantage is:
1. A. it melts at a relatively low temperature
2. B. it absorbs fuel and swells in service
3. C. it can crack and arc-track when damaged
27. In a gear train, the 'driven' gear is the one that:
1. A. receives motion from another gear
2. B. is attached to the power source
3. C. always has the fewest teeth
28. In a metal-ion concentration cell between faying surfaces, corrosion occurs:
1. A. at the centre, where metal-ion concentration is highest
2. B. evenly across the whole surface
3. C. at the edges, where metal-ion concentration is lowest
29. Flexible hoses are classed by pressure. A medium-pressure rubber hose typically has:
1. A. no reinforcement at all
2. B. four spiral steel wire layers
3. C. one wire braid reinforcement
30. In a tensile test, the ultimate tensile strength of a steel specimen is:
1. A. the stress at which permanent deformation starts
2. B. the maximum load divided by the original cross-sectional area
3. C. the load at fracture divided by the final area
31. In a gas turbine, the main shaft bearing that locates the rotor axially and carries thrust is normally a:
1. A. roller bearing
2. B. plain bearing
3. C. ball bearing
32. Which cable locations are classed as critical fatigue areas needing close inspection?
1. A. Straight runs midway between widely spaced pulleys
2. B. Sections passing through pressure seals and nowhere else
3. C. Over pulleys, through fairleads and within 1 ft of swaged fittings
33. Which fibre type gives the best resistance to very high temperatures, for example in heat shields?
1. A. Ceramic fibre
2. B. Aramid fibre
3. C. E-glass fibre
34. For a Rockwell B-scale test, which weight is used and which dial numbers are read?
1. A. Both weights; read the black numbers
2. B. No weight; read the black numbers
3. C. The red weight; read the red numbers
35. A self-locking nut can be reused provided that:
1. A. it still has its minimum prevailing (locking) torque
2. B. it has not been used more than once
3. C. it turns freely by hand onto the bolt
36. In the MS27400-series connector coding, class 'Y' identifies a connector that is:
1. A. environment-resisting, box mounted
2. B. hermetically sealed
3. C. fitted with a potting form
37. A planetary (epicyclic) gear set is often used in propeller reduction gearboxes because it:
1. A. gives large reduction on a common axis
2. B. reverses the propeller rotation
3. C. needs no lubrication in service
38. Corrosion that forms inside the narrow gap between two overlapping skins is called:
1. A. galvanic dissimilar-metal corrosion
2. B. direct chemical attack by acid
3. C. crevice (concentration cell) corrosion
39. Low-carbon steel (about 0.10 to 0.30 % carbon, SAE 1010 to 1030) is typically used for:
1. A. balls and rollers of antifriction bearings
2. B. safety wire, cable bushings and threaded rod ends
3. C. flat springs and coil springs of all sizes
40. Rolling elements and races of aircraft ball bearings are usually made of:
1. A. heat-treated aluminium alloy
2. B. high-carbon chromium steel
3. C. grey cast iron
41. A clip-locking turnbuckle is secured by:
1. A. safety wire wrapped four times on each shank
2. B. a cotter pin through the barrel centre
3. C. spring clips inserted in slots in barrel and terminals
42. Why is a glass-fibre ply placed between a carbon-fibre repair patch and aluminium structure?
1. A. To add lightning strike protection
2. B. To act as a removable peel ply
3. C. To isolate them and prevent galvanic corrosion
43. Which NDT method can check an aluminium alloy part for heat damage as well as cracks?
1. A. Eddy current conductivity testing
2. B. Magnetic particle inspection
3. C. Visual inspection with a 10x magnifier
44. A clevis bolt is used:
1. A. in high-tension applications only
2. B. where the bolt must be tightened with a spanner
3. C. in shear applications such as control cable fittings
45. Before mating a connector, the technician should check:
1. A. that the pins are lightly soldered
2. B. for bent pins, damaged inserts and contamination
3. C. that the grommet has been removed
46. Why do turboprop engines usually have more than one stage of reduction gearing?
1. A. Their output shaft speeds are very high
2. B. Their propellers turn faster than the turbine
3. C. To reverse the propeller for braking
47. Silver-plated contacts show a brown-to-black film. What causes this?
1. A. Galvanic attack by aluminium
2. B. Tarnishing in the presence of sulphur
3. C. Whisker growth from humidity
48. The Brinell hardness test determines hardness by measuring the:
1. A. diameter of the impression made by a hardened ball
2. B. depth of penetration of a diamond cone
3. C. rebound height of a diamond-tipped hammer
49. In a correctly rigged cable control system, 'spring-back' is:
1. A. the stretch of the cable when the aircraft is cold
2. B. the small extra push to take the cockpit control to its stop
3. C. the travel lost when a turnbuckle is safetied
50. What scarf slope is normally used when splicing a solid wood spar?
1. A. About 10 to 1
2. B. About 2 to 1
3. C. About 30 to 1

Answer key

1. C — In pulse-echo inspection a single transducer sends a pulse and receives echoes from the back wall and any defect. Only one side needs access, and the echo timing shows the depth of the defect.
2. A — Dish-outs are elliptical with the major axis spanwise on wings and horizontal stabilisers, longitudinally on fuselages, and vertically on vertical stabilisers.
3. B — The length code's first digit is whole inches and the last digit is eighths of an inch. '12' is therefore 1 and 2/8 in, which is 1 1/4 in.
4. B — Moisture entry through the rear is prevented by matching the wire outside diameter to the rear grommet's sealing range and terminating only one wire per crimp contact. Unused cavities get sealing plugs.
5. C — The pinion is a small gear meshing with a toothed bar (rack). Turning the pinion moves the rack in a straight line, as used in some steering and actuator mechanisms.
6. C — Fretting corrosion is caused by slight repeated movement between tight surfaces. The wear debris oxidises and forms dark powder that streaks from the joint. Loose rivets must be investigated and replaced.
7. A — Rigid tubing is sized by outside diameter (in 1/16 in steps) and wall thickness. Both must be known to select a replacement, because the same OD is made in different wall thicknesses.
8. B — Charpy and Izod tests break a notched specimen with a swinging pendulum and record the energy absorbed in joules. This measures toughness under sudden loading and shows whether the steel is brittle, for example at low temperature.
9. B — Cast aluminium bronze (about 89 % copper, 9 % aluminium) has high strength with ductility and resists corrosion, shock and fatigue, so it is used in bearings and pump parts.
10. A — Past the elastic limit the material yields; the spring keeps a permanent deformation (set) and its preload and rate are no longer as designed.
11. A — Pulleys guide cables round changes of direction with minimum friction. Fairleads and rub strips guide cables in nearly straight runs, and pressure seals seal cables passing through pressure bulkheads.
12. B — Aramid fibres are yellow, light and very tough in tension, so they resist impact and vibration well. Their compressive strength is poor, they absorb moisture and they are hard to cut and drill.
13. A — The first digit identifies the main alloying element: 2xxx copper, 3xxx manganese, 4xxx silicon, 5xxx magnesium, 6xxx magnesium and silicon, 7xxx zinc. 2024 is the best-known 2xxx alloy.
14. B — Aluminium nuts on cadmium-plated steel bolts are allowed in shear on landplanes but not on seaplanes, where salt water greatly increases dissimilar-metal corrosion.
15. B — With the generator carrying rated current, or the battery at the 5-minute rate, the drop in the main power wires to the bus should not exceed 2 % of the regulated voltage. Separate limits apply between the bus and the equipment.
16. B — With the sun gear driving, the cage stationary and the bell gear mounted on the propeller shaft, the propeller turns at reduced speed but in the opposite direction to the crankshaft.
17. B — In the first stage corrosion and cyclic stress together cause pitting and cracks. The second stage is essentially fatigue, with the crack propagating from the pits even if the corrosive environment is removed; failure can occur far below the uncorroded fatigue limit.
18. C — Bulkhead fittings have a longer threaded body with a locknut, so they can be secured through a bulkhead while lines connect to each side.
19. A — Austenitic stainless steels keep an austenitic structure when cooled, so quenching does not form martensite. They are strengthened by cold working instead.
20. B — Rollers make line contact with the races instead of point contact, so a roller bearing carries more radial load. Standard cylindrical roller bearings carry little thrust and need good alignment.
21. A — Compression springs are open-coiled and resist being squeezed; extension springs are close-coiled with hooks and resist being pulled apart; torsion springs resist twisting.
22. A — Aluminium airframes expand and contract with temperature much more than steel cables. Tension regulators automatically take up or release slack so cable tension stays nearly constant.
23. C — Polyester is tautened by heat shrinking. Tautening dope applied over it may make the fabric too taut, putting excess stress on the airframe, so dope-based systems use non-tautening nitrate dope as the sealant.
24. A — Corrosion removal reduces material thickness. The depth and area of blend-out must be measured and compared with the limits in the structural repair manual; if exceeded, a repair or replacement is needed.
25. A — The flanks of the threads bear on each other at the pitch diameter, so it controls the fit. Thread micrometers and the three-wire method measure the pitch diameter.
26. C — Polyimide insulation has high strength and temperature resistance, but it can crack at tight bends and, once damaged, can carbonise and sustain arc tracking. It must be handled and inspected carefully.
27. A — The driving gear is connected to the power source and turns the driven gear. The driven gear may be larger or smaller depending on whether speed is reduced or increased.
28. C — Where the electrolyte has a high concentration of metal ions, the metal is cathodic; where the concentration is low, it is anodic. At faying surfaces the edges, where ions are washed away, corrode.
29. C — Low-pressure hose (below about 250 psi) has fabric braid; medium-pressure hose has one wire braid; high-pressure hose (up to 3000 psi) has two or more wire braids.
30. B — Ultimate tensile strength is the highest engineering stress the specimen carries: the maximum load divided by the original cross-sectional area. Yield strength is the stress at which permanent set begins.
31. C — Ball bearings take both radial and axial (thrust) loads and are used to locate each spool axially. Roller bearings carry radial load and allow axial movement for thermal expansion.
32. C — Critical fatigue areas are anywhere the cable runs over, under or around a pulley, sleeve or fairlead, any section where it is flexed or rubbed, and within 1 ft of a swaged-on fitting.
33. A — Ceramic fibres keep their strength at very high temperatures and are used for heat shields, firewall parts and engine components. Aramid and glass fibres, and their resins, are limited to much lower temperatures.
34. C — Colours guide the set-up: for the B scale use the red weight (100 kg) and read the red numbers; for the C scale add the black weight to the red (150 kg) and read the black numbers.
35. A — The locking feature wears with use. A self-locking nut may be reused only if it still needs at least the minimum prevailing torque to run on; a nut that turns freely by hand has lost its locking action.
36. B — In the MS connector information sheet, class E is environment-resisting box and through-bulkhead mounting, class P is potting, class T is environment-resisting wall and jam-nut mounting, and class Y is hermetically sealed.
37. A — Planetary gears share load between several planet gears, are compact and keep input and output shafts on the same axis. They are common in turboprop and helicopter gearboxes.
38. C — In a crevice, the trapped electrolyte has different oxygen and metal-ion levels from the open surface. This concentration cell makes the crevice anodic, so corrosion develops between the skins.
39. B — Low-carbon steel is used for safety wire, certain nuts, cable bushings and threaded rod ends, and in sheet and tube for secondary or moderately stressed parts. Medium-carbon steel suits forgings and surface hardness; high-carbon steel suits springs.
40. B — Balls, rollers and races are made from hard, wear-resistant high-carbon chromium steel (such as SAE 52100) or corrosion-resistant bearing steels. Cages may be steel, bronze or polymer.
41. C — Clip-locking turnbuckles have slots in the barrel and terminal shanks. Two spring locking clips are inserted and engaged, preventing rotation. Clips are not reused.
42. C — Carbon is cathodic to aluminium, so direct contact with moisture present causes galvanic corrosion of the aluminium. An insulating glass-fibre ply or sealant separates the two materials.
43. A — Overheating changes the temper and electrical conductivity of aluminium alloys. Eddy current conductivity meters detect this change, and eddy current probes also find surface cracks.
44. C — Clevis bolts have a round, slotted or recessed head turned with a screwdriver. They are for shear loads only, for example in control system linkages, and never in tension.
45. B — Bent or recessed pins, damaged inserts, moisture and debris cause poor contact or shorts. Connectors are inspected and mated fully, and coupling rings secured.
46. A — Because of the high output speed of gas turbines, turboprop engines use more than one stage of reduction gearing to bring the propeller to an efficient speed.
47. B — Silver tarnishes in the presence of sulphur, forming a brown-to-black film. Tin is subject to whisker growth, and gold is highly corrosion resistant.
48. A — The Brinell test presses a 10 mm hardened ball into the metal under a fixed load (3000 kg for ferrous metals) and measures the diameter of the impression with a microscope. The diameter is converted into a Brinell hardness number from a table.
49. B — With the cable properly rigged, the control surface should reach its stops before the cockpit control. Spring-back is the small extra push needed for the cockpit control to reach its own mechanical stop.
50. A — Scarf joints in solid wood are cut at a slope of about 10:1 (and not less than 12:1 in plywood), giving a large glue area. The bevels must be accurate and smooth for full contact.

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