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NCAA AME Airframe study materials
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NCAA AME Airframe practice questions

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Question 1Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

On a semi-monocoque fuselage, what is the primary function of the longitudinal stringers?

  1. They carry the bending loads and stiffen the skin against buckling Correct answer.
  2. They transmit the engine torque directly to the firewall
  3. They form the pressure bulkheads at the nose and tail
  4. They provide the attachment points for the landing gear trunnions

Explanation

In semi-monocoque construction the skin carries much of the shear and hoop stress, while the stringers run lengthwise to stiffen the skin and share bending loads. They are not the primary torque or gear-attachment members, and bulkheads are separate transverse structures.

Question 2Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

A wing spar that is machined from a single solid aluminium billet is best described as which type of spar?

  1. Built-up spar
  2. I-beam spar
  3. Solid (machined) spar Correct answer.
  4. Truss spar

Explanation

A solid or machined spar is cut from a single billet, giving an integral web and caps with no riveted joints. Built-up spars are assembled from separate caps and web, and I-beam and truss descriptions refer to the cross-section or internal bracing arrangement rather than monolithic manufacture.

Question 3Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

In aircraft fabric covering, what is the purpose of the dope applied after the fabric is attached?

  1. It acts as a fire retardant only and has no tightening effect
  2. It replaces the need for rib stitching on the wing
  3. It shrinks the fabric taut and provides a tautening, weatherproof finish Correct answer.
  4. It dissolves the fabric surface to fuse the seams permanently

Explanation

Dope is a lacquer that shrinks as the solvent evaporates, tightening the fabric and sealing it against moisture. It does not fuse seams chemically, and it never substitutes for the mechanical attachment provided by rib stitching or screws.

Question 4Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

What is the main advantage of monocoque construction compared with a truss (framework) fuselage?

  1. It requires no formers or bulkheads of any kind
  2. It eliminates the need for any skin-to-frame fasteners
  3. It allows easier internal access to all frames for inspection
  4. It gives a higher strength-to-weight ratio because the skin carries the loads Correct answer.

Explanation

In monocoque construction the stressed skin carries the primary loads, giving an efficient strength-to-weight ratio and a smooth aerodynamic surface. It does not remove the need for frames and bulkheads, and internal access is generally more restricted, not easier.

Question 5Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

Which material is most commonly used for the skins of modern large transport aircraft because of its high strength-to-weight ratio and fatigue performance?

  1. Mild steel sheet
  2. Copper-nickel alloy
  3. Aluminium alloy such as 2024 or 7075 Correct answer.
  4. Cast iron plate

Explanation

High-strength aluminium alloys, typically 2024 and 7075, are widely used for aircraft skins because they combine low density with good strength and, when properly treated, acceptable fatigue and corrosion performance. Steel, copper alloys and cast iron are far too dense for primary skin use.

Question 6Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

In a hydraulically powered aircraft system, what is the function of the accumulator?

  1. It filters contaminants from the return line
  2. It regulates engine fuel flow to the burner
  3. It converts hydraulic pressure into electrical signals
  4. It stores pressurised fluid to absorb pressure surges and supply temporary flow Correct answer.

Explanation

A hydraulic accumulator contains a gas-charged chamber that stores pressurised fluid, damping pressure pulsations and providing a reserve of flow for peak demands. Filtration and pressure-to-signal conversion are performed by separate components, and fuel flow is unrelated to the hydraulic accumulator.

Question 7Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

What is the purpose of the pitot-static system on an aircraft?

  1. To cool the avionics bay during flight
  2. To supply pressure sources for airspeed, altitude and vertical speed instruments Correct answer.
  3. To control the cabin pressurisation outflow valve
  4. To provide electrical power to the flight instruments

Explanation

The pitot-static system provides total pressure from the pitot tube and static pressure from the static ports, which together drive the airspeed indicator, altimeter and vertical speed indicator. It does not supply electrical power, cooling air or cabin pressure control.

Question 8Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

What does the term 'balanced control surface' mean in aircraft primary flight controls?

  1. The surface is arranged so that part of its area lies ahead of the hinge line to reduce hinge moment Correct answer.
  2. The surface is driven by two independent hydraulic actuators
  3. The surface is trimmed only by electrical signals
  4. The surface is weighted so that its centre of gravity lies behind the hinge line

Explanation

A balanced control surface has a portion of its area forward of the hinge line, so aerodynamic forces on that area oppose the hinge moment and reduce the effort needed to move the surface. Adding mass behind the hinge would increase, not reduce, control forces, and dual actuators or trim signals do not constitute aerodynamic balancing.

Question 9Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

A riveted lap joint in an aircraft skin is being inspected. What is the primary purpose of the rivet pitch specification?

  1. To set the diameter of the drilled hole before riveting
  2. To determine the torque applied to the rivet gun
  3. To specify the colour coding of the rivet heads
  4. To ensure the rivets are spaced closely enough to prevent sheet separation and carry the shear load Correct answer.

Explanation

Rivet pitch is the centre-to-centre spacing of rivets; it must be close enough to prevent the sheets from separating between rivets and to distribute the shear load properly. It does not define head colour, gun torque or hole diameter, which are separate specifications.

Question 10Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

During a walk-around inspection you notice a row of rivets on a fuselage lap joint with dark streaks trailing aft from each head. What condition does this most likely indicate?

  1. A paint defect that has no structural significance
  2. Corrosion or fretting at the rivet holes requiring further inspection Correct answer.
  3. Over-torqued rivets that have been set too tightly
  4. Normal aerodynamic staining that requires no action

Explanation

Dark or black streaks from rivet heads usually indicate corrosion products or fretting at the joint, often called smoking rivets, and require investigation of the hole and surrounding skin. Normal aerodynamic staining is generally lighter and diffuse, and rivets are not torque-set, so over-torque is not applicable.

Question 11Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

In a pressurised fuselage, which structural member is designed to carry the pressure differential at the forward and aft ends of the cabin?

  1. The pressure bulkheads Correct answer.
  2. The circumferential frames
  3. The longitudinal stringers
  4. The wing spar carry-through

Explanation

Pressure bulkheads are transverse diaphragms that close the pressurised cabin at each end and carry the pressure differential as membrane and bending loads. Stringers and frames stiffen and shape the shell but do not seal the cabin ends, and the spar carry-through reacts wing loads.

Question 12Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

When checking a cable-operated primary flight control system, what is the effect of excessive cable tension on the aircraft structure and controls?

  1. It increases friction and wear and can overload the cable and pulleys Correct answer.
  2. It has no effect as long as the cable is not slack
  3. It reduces friction and improves control feel
  4. It automatically compensates for temperature changes

Explanation

Excessive cable tension increases friction in the pulleys and fairleads, accelerates wear and can overload the cable terminations and supporting structure. Correct rigging tension is specified for a reason; neither slackness nor over-tension is acceptable, and cables do not self-compensate for temperature.

Question 13Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

An aircraft hydraulic system uses a piston-type accumulator pre-charged with nitrogen. During pre-flight the accumulator pressure reads lower than the specified value. What is the most likely consequence?

  1. The hydraulic fluid will freeze in the lines
  2. The system will have reduced reserve flow and poorer pressure-surge damping Correct answer.
  3. The system will overheat because the fluid cannot expand
  4. The pump will run at a lower output pressure permanently

Explanation

A low nitrogen pre-charge reduces the usable stored fluid and the accumulator's ability to damp pressure surges and supply peak flow. It does not cause fluid freezing, permanently lower pump output, or overheating from blocked expansion; the pump output is set by the pump itself.

Question 14Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

What is the function of a shimmy damper on a nose landing gear assembly?

  1. To retract the gear into the wheel well
  2. To absorb the vertical landing impact loads
  3. To damp nose-wheel oscillations about the steering axis Correct answer.
  4. To lock the gear in the down position

Explanation

A shimmy damper resists rapid oscillatory rotation of the nose wheel about its steering axis, preventing shimmy during taxi and landing. Vertical impact loads are absorbed by the oleo strut or shock absorber, and gear locking and retraction are separate mechanisms.

Question 15Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

In a fuel system, what is the purpose of a vent line from the fuel tank to the atmosphere?

  1. To allow air to enter and leave the tank as fuel is consumed or expands, preventing pressure build-up or vacuum Correct answer.
  2. To drain water from the lowest point of the tank
  3. To supply fuel to the engine-driven pump
  4. To transfer fuel between tanks during flight

Explanation

Vent lines equalise pressure between the tank and atmosphere so that fuel can be drawn out without creating a vacuum and so that expanding fuel or vapour can escape safely. Water drains and fuel transfer use separate lines and valves, and the engine pump draws from the tank outlet.

Question 16Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

What is the primary function of the firewall in an engine installation?

  1. To store engine oil during flight
  2. To isolate the engine compartment from the rest of the aircraft in the event of a fire Correct answer.
  3. To support the engine mount and carry all engine loads
  4. To provide cooling airflow to the engine

Explanation

The firewall is a fire-resistant barrier that prevents flames and hot gases from reaching the cockpit or other compartments. Engine loads are carried by the engine mount, cooling is provided by cowling and baffles, and oil is stored in a separate tank or sump.

Question 17Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

A composite aircraft skin shows a dull, whitish area after an impact. What does this most likely indicate?

  1. The paint has been applied too thinly
  2. The composite has been over-cured during manufacture
  3. Delamination or matrix cracking requiring inspection Correct answer.
  4. Normal surface oxidation with no structural meaning

Explanation

Whitening or a dull patch on a composite surface after impact often indicates matrix cracking, delamination or broken fibres beneath the surface, which requires further inspection such as tap testing or ultrasound. It is not a normal ageing effect, and over-cure or thin paint would not produce this localised impact signature.

Question 18Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

What is the purpose of the static dischargers fitted to the trailing edges of aircraft control surfaces?

  1. To act as aerodynamic vortex generators
  2. To provide a lightning strike attachment point
  3. To dissipate static electricity accumulated during flight and reduce radio interference Correct answer.
  4. To measure the aircraft's airspeed accurately

Explanation

Static dischargers, or static wicks, bleed off accumulated static charge into the atmosphere so that it does not discharge across radio antennas and cause interference. They do not measure airspeed, are not designed as lightning attachment points, and are not vortex generators.

Question 19Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

When rigging a flight control system, why is it important that the control surface neutral position matches the rigging marks?

  1. To reduce the weight of the control surface
  2. To increase the maximum deflection of the surface
  3. To ensure symmetrical control response and correct trim with the aircraft in level flight Correct answer.
  4. To allow the surface to move without hinges

Explanation

Rigging marks define the neutral position that gives symmetrical deflection and correct trim; mis-rigging can cause roll or yaw bias and increased drag. Neutral rigging does not change surface weight, maximum deflection limits or the need for hinges.

Question 20Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

In an aircraft pneumatic system, what is the purpose of the pressure regulator valve?

  1. To reduce and maintain a constant downstream pressure from a higher source pressure Correct answer.
  2. To increase the pressure to the maximum available
  3. To convert pneumatic pressure into hydraulic pressure
  4. To filter water from the pneumatic supply

Explanation

A pressure regulator reduces the higher supply pressure to a controlled, constant downstream pressure for systems such as anti-icing or pressurisation. It does not boost pressure, filter water or convert pneumatic energy into hydraulic pressure.

Question 21Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

An aircraft is found to have a crack initiating at a fastener hole in a wing lower skin. Which factor most directly explains why cracks commonly initiate at such holes?

  1. Stress concentration at the hole edge combined with cyclic loading Correct answer.
  2. The skin is thinner at the holes than elsewhere
  3. The holes are always drilled too large
  4. Fastener holes are never inspected

Explanation

A hole concentrates stress at its edge, and repeated pressurisation and flight loads produce cyclic stress that can initiate a fatigue crack there. Hole size, local skin thickness and inspection frequency are separate variables and do not by themselves explain the initiation site.

Question 22Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

A wing is designed with multiple spars and a stressed skin. During flight, the upper skin is primarily in compression while the lower skin is in tension. Which structural idealisation best explains this?

  1. The wing carries only torsional loads through the skin
  2. The wing acts as a beam in bending, with the skin and spar caps carrying the bending stresses Correct answer.
  3. The wing carries loads only through the ribs
  4. The wing acts as a pressure vessel carrying only hoop stress

Explanation

A wing behaves largely as a beam in bending, so the upper surface is compressed and the lower surface is stretched while the spar caps and skin carry the bending stresses. Hoop stress belongs to pressurised shells, torsional loads are carried by the closed skin box, and ribs distribute loads rather than carrying them alone.

Question 23Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

A transport aircraft experiences a sudden loss of cabin pressure. Which structural component is most directly responsible for resisting the resulting pressure differential loads at the fuselage shell?

  1. The wing attachment fittings
  2. The stressed skin and frames acting as a pressure vessel Correct answer.
  3. The floor beams alone
  4. The passenger seats

Explanation

The pressurised fuselage shell, comprising the stressed skin and circumferential frames, acts as a pressure vessel and carries the hoop and longitudinal pressure loads. Floor beams, seats and wing fittings have other functions and do not resist the pressure differential.

Question 24Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

During a structural repair, a doubler is to be riveted over a cracked skin. Why must the rivet pattern and doubler size be calculated rather than chosen arbitrarily?

  1. To match the paint colour of the surrounding skin
  2. To ensure the doubler carries its share of the load and restores the strength of the original structure Correct answer.
  3. To reduce the number of rivets needed for appearance
  4. To allow the doubler to be removed easily in service

Explanation

A repair doubler must be sized and riveted so that it transfers load across the crack and restores the strength and stiffness of the original structure without creating new stress concentrations. Appearance, rivet count for cosmetics and ease of removal are not structural criteria.

Question 25Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

An aircraft with a truss-type fuselage is being assessed after a hard landing. Which members are most likely to have been overloaded, and why?

  1. The diagonal and vertical members, because they carry the shear and bending loads induced by the landing impact Correct answer.
  2. The wing spar, because it reacts the fuselage loads
  3. The fabric covering, because it carries all the landing loads
  4. The cockpit seats, because they are the primary load path

Explanation

In a truss fuselage the diagonal and vertical members form the load path for shear and bending, so a hard landing concentrates stress in these members and their joints. Fabric covering, seats and the wing spar do not carry the fuselage landing loads in that manner.

Question 26Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

In a semimonocoque wing structure, what is the primary role of the stringers?

  1. They provide the attachment points for the landing gear only
  2. They stiffen the skin and carry bending loads in combination with the skin Correct answer.
  3. They carry all the torsional load and replace the need for ribs
  4. They act as the sole load path for wing bending, making the skin non-load-bearing

Explanation

Stringers are longitudinal members that stiffen the skin against buckling and share bending loads with the stressed skin. The skin and stringers together form the effective load-carrying upper and lower surfaces. Ribs, not stringers, maintain the aerofoil shape and transfer loads to the spars.

Question 27Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

What distinguishes a monocoque fuselage from a semimonocoque fuselage?

  1. The monocoque design relies on the stressed skin for almost all loads, with little internal framing Correct answer.
  2. The monocoque design uses a welded steel truss as its main load path
  3. The monocoque design uses only stringers and no skin
  4. The monocoque design has no skin at all and relies on frames

Explanation

A true monocoque structure carries primary loads in the stressed skin, with frames used mainly to hold the shape and prevent buckling. Semimonocoque construction adds substantial stringers and frames so the skin and framing share the loads. This is why pure monocoque is rare in larger aircraft.

Question 28Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

Which structural member of a wing carries the concentrated loads from the wing skin and stringers into the fuselage attachment fittings?

  1. The leading-edge strip
  2. The spar Correct answer.
  3. The rib
  4. The aileron

Explanation

Spars are the main spanwise beams; they collect loads from the skin and stringers and transfer them to the fuselage through attachment fittings. Ribs distribute loads chordwise and maintain shape, but the spar is the primary bending member. This is why spar inspection is a critical structural task.

Question 29Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

What is the function of a wing rib in a stressed-skin wing?

  1. It maintains the aerofoil shape and transfers loads between skin and spars Correct answer.
  2. It provides the hinge line for the flap
  3. It seals the fuel tank from the outside air
  4. It carries the entire wing bending moment on its own

Explanation

Ribs give the wing its chordwise profile, support the skin and stringers, and redistribute loads to the spars. They also help prevent skin buckling between spars. They are not the primary bending member, which is the spar.

Question 30Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

Aircraft structural fasteners are generally classified by which characteristic in maintenance documentation?

  1. Their colour and surface finish
  2. The manufacturer's country of origin
  3. Their head type and the method by which they are locked or secured Correct answer.
  4. Their weight alone

Explanation

Solid rivets, blind rivets, Hi-Lok, and lockbolt fasteners are identified by head style and locking method, which determines installation and removal procedures. This classification drives the correct tooling and inspection criteria. Surface finish and origin do not define fastener type.

Question 31Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

What is the purpose of a lightning diverter strip bonded to a composite aircraft skin?

  1. To reduce aerodynamic drag at high speed
  2. To conduct lightning current away from critical structure and dissipate it safely Correct answer.
  3. To indicate the presence of static electricity to ground crew
  4. To improve radio reception on the VHF band

Explanation

Composite skins do not conduct lightning current like aluminium, so metallic diverter strips provide a controlled path that carries current away from critical structure. This protects the structure from delamination and puncture. It has no role in radio reception or drag reduction.

Question 32Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

What does the term 'fail-safe' mean in aircraft structural design?

  1. The structure has a single redundant load path only
  2. The structure is designed to fail at a predictable load
  3. The structure never requires inspection because it cannot fail
  4. The structure can sustain damage to a limited extent without catastrophic failure until the damage is found Correct answer.

Explanation

Fail-safe design uses multiple load paths or crack-arrest features so that a partial failure does not lead to loss of the aircraft. It depends on inspection programmes to detect the damage before it propagates. It does not mean the structure is immune to failure.

Question 33Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

In a cable-operated flight control system, what is the purpose of a turnbuckle?

  1. To lock the control surface in the neutral position
  2. To change the direction of cable travel
  3. To adjust and maintain cable tension Correct answer.
  4. To protect the cable from chafing

Explanation

Turnbuckles are threaded fittings that allow the rigger to set and adjust cable tension, then lock it with safety wire. Pulleys change cable direction, and fairleads protect against chafing. Locking the surface neutral is a rigging outcome, not the turnbuckle's function.

Question 34Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

A control surface is described as mass-balanced. What does this mean?

  1. The surface is balanced by springs in the control circuit
  2. The surface is made heavier than the wing to resist flutter
  3. Weight is added ahead of the hinge line to move the centre of gravity toward the hinge Correct answer.
  4. The surface is balanced aerodynamically by a trim tab

Explanation

Mass balancing places weight ahead of the hinge line so the surface's centre of gravity is at or forward of the hinge, preventing flutter. It is a structural mass distribution measure, not an aerodynamic or spring device. Loss of balance weights is a serious airworthiness defect.

Question 35Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

A wing skin panel shows a series of small cracks running between adjacent fastener holes along the spar cap. Which action is most appropriate?

  1. Assess against the approved structural repair manual and apply an approved repair or replacement Correct answer.
  2. Apply a coat of primer over the cracks and return to service
  3. Ignore the cracks because they are between holes
  4. Drill out the cracks and leave the holes open

Explanation

Cracks between fastener holes indicate fatigue and must be evaluated against approved data before repair or replacement. Unapproved field fixes are not acceptable for primary structure. Leaving open holes or painting over cracks does not restore structural integrity.

Question 36Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

When inspecting a bonded composite repair on a control surface, which method is commonly used to detect disbonds without damaging the repair?

  1. Tap testing or ultrasonic inspection Correct answer.
  2. Magnetic particle inspection
  3. Dye penetrant inspection
  4. Eddy current inspection

Explanation

Tap testing and ultrasonic inspection are suited to detecting voids and disbonds in bonded composite joints. Magnetic particle and eddy current methods require conductive ferromagnetic or metallic materials. Dye penetrant detects surface-breaking defects only and cannot find internal disbonds.

Question 37Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

Why are close-tolerance (interference-fit) fasteners used in some wing skin joints?

  1. They improve fatigue life by reducing load transfer through the hole and lowering stress concentration Correct answer.
  2. They eliminate the need for sealant in fuel tanks
  3. They permit the joint to be disassembled repeatedly without wear
  4. They allow faster installation than standard rivets

Explanation

Interference-fit fasteners fill the hole tightly, reducing cyclic stress at the hole edge and improving fatigue performance. They are more difficult to install, not faster. They do not replace sealant in integral tanks or guarantee repeated disassembly.

Question 38Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

A pressurised fuselage has a door surround structure. What is the main structural concern at the door cut-out?

  1. Reduced fuel capacity near the door
  2. Increased aerodynamic drag from the door
  3. Interference with the cabin lighting circuit
  4. Concentration of pressure and shear loads around the opening requiring reinforcing frames Correct answer.

Explanation

Cut-outs interrupt the load path in a pressurised shell, so reinforcing frames and doublers are needed to carry the concentrated pressure and shear loads around the opening. This is a fatigue-critical region that receives special inspection attention. Drag, fuel, and lighting are unrelated concerns.

Question 39Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

What is the purpose of a shear tie in a semimonocoque fuselage?

  1. To carry the entire cabin pressure load longitudinally
  2. To connect frames to the skin and transfer shear loads between them Correct answer.
  3. To provide the attachment for the passenger seats
  4. To act as a primary bending member along the fuselage

Explanation

Shear ties join frames to the skin so that shear loads are transferred between the frame and the shell. They help stabilise the skin and maintain the frame-skin load path. They are not primary longitudinal bending members and do not carry pressure loads on their own.

Question 40Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

In an aircraft hydraulic system, what is the function of the selector valve?

  1. To store pressurised fluid for peak demand
  2. To direct hydraulic pressure to the chosen actuator and route return fluid back to the reservoir Correct answer.
  3. To regulate system pressure by bypassing excess fluid
  4. To filter contamination from the hydraulic fluid

Explanation

The selector valve controls the direction of flow to an actuator, determining which side is pressurised and which returns to the reservoir. Pressure regulation is the job of the pressure regulator or relief valve. Accumulators store energy, and filters remove contamination.

Question 41Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

A hydraulic system uses a pressure relief valve in addition to a pressure regulator. Why is this necessary?

  1. The relief valve replaces the reservoir in an emergency
  2. The relief valve provides a backup path that opens if system pressure exceeds a safe limit Correct answer.
  3. The relief valve increases system pressure during heavy load
  4. The relief valve filters fluid before it reaches the actuator

Explanation

The relief valve is a protective device that opens at a set pressure to prevent overpressure if the regulator fails or a pressure surge occurs. The regulator maintains normal operating pressure. The relief valve does not boost pressure, filter fluid, or replace the reservoir.

Question 42Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

In a light aircraft fuel system, what is the function of the fuel selector valve?

  1. To drain water from the lowest point of the system
  2. To automatically meter fuel into the carburettor
  3. To allow the pilot to select which tank supplies the engine Correct answer.
  4. To indicate the quantity of fuel in each tank

Explanation

The selector valve lets the pilot choose the tank feeding the engine and shut off fuel when needed. Fuel metering is done by the carburettor or fuel control unit. Quantity indication comes from the fuel gauges, and water is removed through drain valves.

Question 43Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

What is the purpose of a fuel boost pump in an aircraft fuel system?

  1. To measure the fuel flow to the engine
  2. To provide a positive fuel supply to the engine-driven pump, especially at altitude or during manoeuvres Correct answer.
  3. To transfer fuel between tanks only during refuelling
  4. To cool the fuel before it enters the engine

Explanation

Boost pumps maintain positive pressure at the inlet of the engine-driven pump, preventing vapour lock and ensuring continuous supply during climbs, manoeuvres, or when tank outlets are uncovered. They do not measure flow or cool the fuel. Some types can transfer fuel, but that is not their primary purpose.

Question 44Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

What is the purpose of the cabin pressure outflow valve?

  1. To supply oxygen to the passenger masks
  2. To relieve pressure only when the cabin exceeds maximum differential
  3. To admit fresh air into the cabin from the engine bleed system
  4. To regulate the rate at which cabin air leaves the aircraft, thereby controlling cabin altitude Correct answer.

Explanation

The outflow valve modulates the discharge of cabin air so that cabin pressure and rate of change are controlled. Inflow is provided by the air conditioning and pressurisation system, not the outflow valve. Pressure relief is a separate safety function, and oxygen supply is independent.

Question 45Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

In a pneumatic system, what is the purpose of the bleed air precooler?

  1. To remove oil from the bleed air for the fuel system
  2. To increase the pressure of bleed air for the hydraulic reservoir
  3. To cool the engine oil during ground operation
  4. To reduce the temperature of hot engine bleed air before it enters the air conditioning system Correct answer.

Explanation

The precooler uses fan air or another cooling medium to reduce bleed air temperature to a level suitable for downstream components. This protects ducts, valves, and the air conditioning system from excessive heat. It does not boost pressure, clean fuel, or cool engine oil.

Question 46Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

A pitot-static system blockage in the static line will most directly affect which instrument indications?

  1. Heading indicator and turn coordinator only
  2. Airspeed indicator and turn coordinator only
  3. Attitude indicator and heading indicator only
  4. Airspeed indicator, altimeter, and vertical speed indicator Correct answer.

Explanation

All three pressure instruments, the airspeed indicator, altimeter, and vertical speed indicator, use static pressure. A static line blockage therefore affects all three. The turn coordinator is gyroscopic and does not use static pressure, and the heading indicator is likewise independent of the static system.

Question 47Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

An aircraft is being rigged and the aileron travels exceed the limits given in the maintenance manual. What is the correct action?

  1. Adjust the control stops and rigging to the approved limits before flight Correct answer.
  2. Record the discrepancy and defer it to the next annual inspection
  3. Leave the travel as found because larger travel improves roll rate
  4. Reduce the travel by fitting a larger control wheel

Explanation

Control surface travel limits are airworthiness requirements and must be set within the approved rigging tolerances using the control stops. Excessive travel can cause overstressing or loss of control authority. It cannot be deferred or compensated by fitting a different control wheel.

Question 48Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

A landing gear shock strut is serviced with nitrogen and hydraulic fluid. What is the primary function of the nitrogen charge?

  1. To act as a spring that absorbs shock loads and returns the strut to extension Correct answer.
  2. To provide hydraulic pressure for the brakes
  3. To lubricate the sliding piston inside the strut
  4. To prevent corrosion of the inner cylinder

Explanation

In an oleo strut, the gas charge acts as the spring while the hydraulic fluid provides damping, so the nitrogen absorbs and dissipates landing loads. Lubrication and corrosion protection are secondary effects of the fluid. Brake pressure comes from the separate hydraulic system.

Question 49Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

During a structural repair, a crack in an aluminium skin is stop-drilled before a doubler is fitted. What is the purpose of stop-drilling?

  1. To provide a pilot hole for the doubler rivets
  2. To allow sealant to be injected into the crack
  3. To make the crack easier to see during later inspections
  4. To remove the sharp crack tip and reduce further stress concentration and crack growth Correct answer.

Explanation

Stop-drilling places a round hole at the crack tip, removing the sharp notch that concentrates stress and slowing further propagation until the repair is completed. It is not a rivet pilot hole and does not seal the crack. The repair still requires an approved doubler or patch.

Question 50Airframe structures and airframe systems (per Nig. CARs Part 7 / NCAA-AC-PEL 018 syllabus scope)

A composite sandwich panel on a control surface has absorbed moisture and shows a soft area when tapped. What is the most likely cause?

  1. A manufacturing error in the paint finish
  2. Disbonding between the skin and the core, often following impact or water ingress Correct answer.
  3. Normal ageing of the outer skin without any structural effect
  4. Excessive stiffness of the core material

Explanation

A dull or soft tap response in a sandwich panel usually indicates a disbond between skin and core, which can follow impact or water ingress and freeze-thaw cycling. This reduces stiffness and load-carrying capability. Paint finish and normal ageing do not produce a local soft area.