NCAA Aircraft Maintenance Engineer Licence - Airframe (Nigeria)

Which aluminum alloy heat treatment designation indicates that the metal has been solution heat-treated and artificially aged?

• AT6
• BO
• CT3
• DF

What primary advantage does Alclad 2024-T3 aluminum sheet possess over unclad 2024-T3 aluminum sheet?

• ASuperior corrosion resistance due to a pure aluminum surface layer
• BHigher ultimate tensile strength than structural steel
• CIncreased resistance to high-temperature thermal degradation above 500°F
• DGreater hardness and scratch resistance during riveting operations

Which type of stress is produced inside a cantilever wing spar upper cap during level forward flight?

• ACompression stress
• BTension stress
• CTorsional shear stress
• DPure bearing stress

What type of aircraft structural design relies primarily on external skin, formers, and bulkheads to carry structural loads without heavy internal longitudinal framework?

• AMonocoque structure
• BPratt truss structure
• CSemi-monocoque structure
• DWarren truss structure

Which non-destructive testing (NDT) method is most effective for detecting internal subsurface delaminations in thick carbon-fiber reinforced polymer (CFRP) aircraft structures?

• AUltrasonic pulse-echo testing
• BDye penetrant inspection
• CMagnetic particle inspection
• DEddy current testing

Why must aramid fiber (Kevlar®) composite materials be drilled with special brad-point or diamond-coated drill bits?

• AAramid fibers tend to fray and fuzz rather than cut cleanly when standard twist drills ar…
• BKevlar is extremely brittle and shatters under normal high-speed steel drill pressure
• CAramid fibers generate toxic halogen gas when subjected to friction from twist drills
• DStandard twist drills instantly react chemically with epoxy matrix causing resin liquefac…

In composite repair, what function does release fabric (peel ply) serve when placed directly over a wet layup or prepreg repair patch?

• AIt provides a clean, textured surface for subsequent bonding and allows excess resin and…
• BIt acts as a permanent structural outer skin layer to absorb UV radiation damage
• CIt melts at cure temperatures to seal moisture permanently out of honeycomb cores
• DIt conducts electrical current evenly across the repair area to accelerate inductive heat…

What is the primary cause of intergranular corrosion in 2024 aluminum alloy?

• AImproper or slow quenching during heat treatment causing copper to precipitate along grai…
• BDirect exposure to pure hydraulic fluid (MIL-H-5606) at high temperatures
• CExcessive anodizing layer thickness exceeding 0.005 inches
• DOver-torquing structural fasteners beyond specified limits

Which type of sandwich core material is most vulnerable to internal moisture accumulation and core degradation if skin punctures occur?

• ANomex® honeycomb core
• BSolid closed-cell polymethacrylimide (PMI) foam core
• CSolid syntactic epoxy foam core
• DSolid aluminum honeycomb core with potted moisture barriers

When drilling titanium alloy structural components during airframe repairs, which cutting parameters should be maintained?

• ALow drill speed (RPM), heavy steady feed pressure, and continuous application of cutting…
• BHigh drill speed (RPM), light feed pressure, and dry unlubricated drilling
• CUltra-high speed pneumatic drilling with standard high-speed steel twist bits
• DIntermittent light tapping without cutting fluid to prevent thermal shock

A composite structural panel repair requires a resin matrix ratio of 60% carbon fiber fabric to 40% epoxy resin by weight. If the dry carbon fiber patch weighs 150 grams, how much mixed epoxy resin is required?

• A100 grams
• B60 grams
• C90 grams
• D150 grams

Stress corrosion cracking (SCC) in high-strength aluminum airframe components requires the simultaneous presence of which three factors?

• ASustained tensile stress, a susceptible material alloy composition, and a corrosive envir…
• BCompressive stress, low ambient humidity, and thermal insulation contact
• CTorsional stress, high electrical grounding resistance, and hydraulic fluid immersion
• DCyclic fatigue stress, inert gas coverage, and magnetic fields

What is the primary purpose of stop-drilling the extreme ends of a crack in an aluminum skin panel?

• ATo relieve stress concentrations by distributing stress over a larger radius hole
• BTo provide access holes for cleco temporary fasteners during patching
• CTo allow chemical corrosion inhibitors to penetrate inside the crack tip
• DTo create alignment points for optical laser structural measurement

Calculate the bend allowance (BA) for a 90° bend in 0.040-inch thick 2024-T3 aluminum sheet using a bend radius (R) of 0.1875 inches (3/16 in). Use the standard formula BA = N × (0.01743 × R + 0.0078 × T).

• A0.322 inches
• B0.228 inches
• C0.415 inches
• D0.187 inches

An airframe repair requires joining two 0.045-inch thick aluminum sheets using 1/8-inch (0.125 in) diameter MS20470AD rivets. What is the required minimum total rivet length (L)? (Formula: L = Grip + 1.5 × D)

• A5/16 inch (0.3125 in)
• B1/4 inch (0.250 in)
• C3/8 inch (0.375 in)
• D3/16 inch (0.1875 in)

For a structural sheet metal repair using 5/32-inch diameter rivets, what is the minimum acceptable edge distance (measured from the center of the rivet hole to the edge of the sheet)?

• A5/16 inch (2D)
• B5/32 inch (1D)
• C15/32 inch (3D)
• D5/8 inch (4D)

What is the setback (SB) for a 90° bend in a sheet metal part with a bend radius (R) of 0.250 inches and sheet thickness (T) of 0.064 inches?

• A0.314 inches
• B0.186 inches
• C0.250 inches
• D0.378 inches

How is a 2117-T aluminum alloy rivet (MS20470AD) identified by its manufactured head marking?

• AA single recessed dimple in the center of the head
• BTwo raised dashes on opposite sides of the head
• CA single raised dot in the center of the head
• DA smooth manufactured head with no markings

Why must 2024-T4 ('DD') aluminum rivets be stored in a freezer sub-zero storage container after heat treatment until driven?

• ATo retard age-hardening so they remain soft enough to drive without cracking
• BTo prevent surface oxidation and pitting corrosion prior to installation
• CTo shrink shank diameter temporarily for interference fit hole insertion
• DTo prevent volatile copper alloying elements from evaporating

When preparing sheet metal skin for flush riveting, under what condition is machine countersinking permitted instead of dimpling?

• AWhen the top sheet thickness is equal to or greater than the depth of the rivet head
• BWhen the top sheet thickness is less than 0.032 inches thick
• CWhenever 2117-T rivets are installed in magnesium alloy skins
• DOnly when double-flush riveting soft 1100 aluminum sheet

What is the industry standard color code for Cleco temporary sheet metal fasteners used for 1/8-inch (#30 hole) rivets?

• ACopper
• BZinc / Silver
• CBrass / Gold
• DBlack

What is the recommended minimum transverse pitch (distance between parallel rows of rivets) in a multi-row lap joint repair layout?

• A75% of the rivet pitch (typically 2.5 to 3 times rivet diameter)
• B100% of the edge distance (2 times rivet diameter)
• C5 times sheet thickness
• DEqual to 12 times rivet diameter

What is the purpose of drilling relief holes at the intersection of bend lines in sheet metal channel fittings?

• ATo prevent stress concentration and tearing of the metal at the corner intersection durin…
• BTo provide drain locations for accumulated fuel in wing stringers
• CTo allow clearance for blind rivet heads installed in corner flanges
• DTo reduce overall structural weight by eliminating non-structural metal

Why is a flush patch (insert patch with doubler) preferred over an external lap patch for high-speed aircraft outer skin repairs?

• AIt maintains smooth aerodynamic airflow and eliminates parasitic drag while restoring str…
• BIt requires 50% fewer rivets than an external surface lap patch
• CIt eliminates the need for anti-corrosion primer between skin and doubler
• DIt allows structural welding of heat-treated 7075-T6 aluminum alloys

Which elastomer seal material must be used in hydraulic components operating with Skydrol® phosphate ester hydraulic fluid?

• AEthylene propylene rubber (EPR / EPDM)
• BBuna-N (Nitrile rubber)
• CNeoprene rubber
• DNatural gum rubber

What fundamental principle of fluid dynamics states that pressure applied to a confined fluid is transmitted equally and undiminished in all directions?

• APascal's Law
• BBernoulli's Principle
• CBoyle's Law
• DCharles's Law

A hydraulic system operates at a system pressure of 3,000 psi. If a landing gear extension actuator piston has an effective diameter of 3.0 inches, what total extending force is produced by the actuator? (Use Area = π × r²)

• A21,206 lbs
• B9,000 lbs
• C28,274 lbs
• D14,137 lbs

In a hydraulic brake system, a mechanical pedal input applies a force of 50 lbs onto a master cylinder piston with an area of 0.5 sq in. If this pressure is transmitted to a wheel brake slave cylinder piston with an area of 4.0 sq in, what output force is exerted on the brake pads?

• A400 lbs
• B200 lbs
• C100 lbs
• D800 lbs

What are the primary functions of a hydraulic accumulator installed in an aircraft high-pressure hydraulic system?

• ATo store fluid under pressure, absorb fluid pressure surges, and provide emergency pressu…
• BTo remove entrained air bubbles and cool hydraulic fluid before returning to reservoir
• CTo meter fluid flow rate automatically based on pilot control stick deflection
• DTo convert hydraulic pressure directly into alternating electrical current

What gas must be used to pre-charge aircraft hydraulic accumulators, and why?

• ADry nitrogen, because it is an inert gas that prevents explosive oil-vapor combustion und…
• BCompressed shop air, because it contains oxygen which stabilizes synthetic hydraulic oils
• CPure carbon dioxide, because it cools hydraulic fluid during rapid discharge cycles
• DPure hydrogen gas, because of its light weight and low molecular density

How does a variable-displacement axial-piston hydraulic pump alter its fluid output flow rate while maintaining constant shaft RPM?

• ABy adjusting the angle of the internal swashplate (cam plate)
• BBy varying input shaft gear reduction ratios via an internal clutch
• CBy throttling the main pump suction line inlet valve
• DBy recirculating excess fluid through a high-pressure electric bypass valve

What is the function of a hydraulic shuttle valve in an aircraft landing gear extension or brake system?

• ATo automatically switch an actuator feed line to an emergency pressure source if primary…
• BTo regulate system working pressure down to instrument operating limits
• CTo lock landing gear actuators mechanically in the down and locked position
• DTo mix main and auxiliary hydraulic fluids to equalize fluid viscosity

What primary protection does a system pressure relief valve provide in a hydraulic system?

• AIt acts as a safety device to prevent excessive pressure buildup that could burst hydraul…
• BIt maintains a constant fluid flow rate regardless of engine RPM changes
• CIt prevents hydraulic fluid from flowing backward into the reservoir when the pump stops
• DIt traps high pressure in accumulator chambers during ground servicing

A double-acting hydraulic cylinder has a piston area of 5.0 sq in and a stroke length of 10.0 inches. How many cubic inches of hydraulic fluid are required to extend the cylinder piston fully?

• A50 cubic inches
• B25 cubic inches
• C5 cubic inches
• D500 cubic inches

Why are thermal relief valves installed in hydraulic actuator lines that can be isolated by closed selector valves?

• ATo relieve dangerous pressure buildup caused by thermal expansion of trapped hydraulic fl…
• BTo heat hydraulic fluid automatically during high-altitude operations
• CTo bypass high-viscosity cold fluid around actuator piston seals during start-up
• DTo release trapped air bubbles into the atmosphere when fluid temperature exceeds 100°C

What color is mineral-base hydraulic fluid MIL-H-5606 dyed for identification in aircraft systems?

• ARed
• BPurple
• CGreen
• DBlue

Which aircraft control surfaces are categorized as primary flight controls?

• AAilerons, elevators, and rudder
• BTrailing edge flaps, leading edge slats, and trim tabs
• CSpoilers, speed brakes, and anti-servo tabs
• DFowler flaps, slotted flaps, and ground spoilers

What is the aerodynamic purpose of incorporating differential aileron travel into an aircraft flight control rigging system?

• ATo eliminate or minimize adverse yaw during roll entries by raising the up-moving aileron…
• BTo increase maximum pitch authority at low airspeed landing approaches
• CTo prevent wingtip flutter during supersonic acceleration
• DTo equalize control cable tension during high G turns

When rigging flight control cables in an all-metal aircraft, why must cable tension be adjusted strictly according to ambient temperature using a cable tension compensation chart?

• ABecause aluminum airframe structure expands and contracts at a higher thermal rate than s…
• BBecause steel cables stretch rapidly under high ambient heat due to copper annealing
• CBecause control cable grease solidifies at cold temperatures, locking turnbuckles
• DBecause pulley bearing diameters decrease under hot weather conditions

When safetying an aircraft control cable turnbuckle using the double-wrap spiral method, what safety wire diameter is required for 1/8-inch control cables?

• A0.040 inch stainless steel wire
• B0.020 inch soft copper wire
• C0.057 inch brass wire
• D0.015 inch aluminum wire

What is the aerodynamic function of an anti-servo tab attached to the trailing edge of an all-movable stabilator?

• AIt moves in the same direction as the trailing edge of the stabilator to increase stick f…
• BIt moves in the opposite direction to reduce pilot control yoke force to zero
• CIt deploys automatically at Mach 0.8 to act as a pitch trim brake
• DIt deflects downward only when landing flaps extend to offset nose-up pitching

During inspection of push-pull control rod end fittings, how is proper thread engagement verified prior to safetying?

• ABy attempting to pass a piece of safety wire through the inspection witness hole in the r…
• BBy measuring exposed threads with a vernier caliper to ensure exactly 3 threads remain ou…
• CBy applying 100 in-lbs torque to the rod end ball joint with a dial wrench
• DBy checking that the locknut touches the end of the threaded shank

What is the primary difference in operation between a balance tab and a spring tab on a control surface?

• AA balance tab moves proportionally to surface displacement at all speeds, whereas a sprin…
• BA balance tab is electrically driven by trim motors, whereas a spring tab is purely hydra…
• CA balance tab assists roll control, whereas a spring tab operates exclusively on ground s…
• DA balance tab increases control force stick feel, whereas a spring tab eliminates aerodyn…

After swaging a terminal fitting onto a flight control cable, how must the quality of the swaged joint be inspected?

• AUsing a go/no-go gauge to verify shank outer diameter and inspecting for surface cracks
• BPerforming a dye penetrant inspection over the entire cable strand length
• CHeating the swaged fitting with a torch to observe solder flow
• DX-raying the cable core to measure inner strand elongation

What function do flight spoilers (spoilerons) perform when deployed asymmetric (on one wing only) during in-flight banked turns?

• AThey assist ailerons in lateral roll control by dumping lift on the down-going wing
• BThey act as longitudinal pitch trimmers to prevent nose-down pitching
• CThey extend leading-edge camber to prevent high-angle-of-attack wing stall
• DThey equalize hydraulic pressure between left and right primary flight control actuators

Why must control surfaces (such as elevators or ailerons) be rebalanced in accordance with manufacturer limits following structural repair or painting?

• ATo prevent catastrophic control surface flutter caused by aerodynamic and mass unbalance…
• BTo ensure automatic autopilot disconnect during turbulence
• CTo equalize weight distribution between main landing gear wheels
• DTo lower control surface drag coefficient during supersonic cruise

What is the proper procedure for servicing a completely deflated oleo-pneumatic shock strut with fluid and gas?

• AFully compress the strut, fill with specified hydraulic fluid to the level plug hole, ext…
• BInflate with dry nitrogen to maximum pressure first, then pump in hydraulic fluid under 3…
• CFill the strut completely to the top with hydraulic fluid while fully extended, then cap…
• DInflate with compressed air until the strut reaches maximum extension, then add 1 quart o…

What component inside an oleo-pneumatic shock strut controls the rate of hydraulic fluid flow between the lower piston and upper cylinder during landing impact compression and recoil?

• AMetering pin and orifice plate
• BHydraulic shuttle spool
• CThermal expansion compensator
• DVariable swashplate piston