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CAA NZ AME Licence Exam - Rotorcraft study materials
CAA NZ AME Licence Exam - Rotorcraft study resources

CAA NZ AME Licence Exam - Rotorcraft practice questions

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Question 1Rotorcraft airframe systems and structures

On a helicopter with a fully articulated main rotor head, what is the primary function of the drag (lead-lag) hinge?

  1. To damp vertical vibration transmitted to the mast
  2. To change blade pitch collectively during autorotation
  3. To permit in-plane blade movement and relieve chordwise loads at the hub Correct answer.
  4. To allow blade flapping in response to cyclic input

Explanation

The drag hinge allows each blade to lead and lag slightly within the plane of rotation as its velocity and drag vary around the disc, which relieves chordwise bending loads at the blade root. Flapping is handled by the separate flapping hinge, and pitch change is handled by the pitch horn and bearings.

Question 2Rotorcraft airframe systems and structures

A semi-rigid (teetering) two-blade main rotor differs from an articulated head in that it relies on which feature to accommodate flapping?

  1. A single central teetering hinge with a trunnion Correct answer.
  2. Individual flapping hinges at each blade root
  3. Elastomeric lead-lag bearings at each grip
  4. Pitch links acting as torsion bars

Explanation

A semi-rigid head permits flapping by teetering about a single central hinge, so one blade rises as the other falls. There are no individual flapping hinges per blade, which is the key structural distinction from a fully articulated head.

Question 3Rotorcraft airframe systems and structures

During a static balance check of a main rotor blade, the blade is found to be tail-heavy. What is the accepted corrective action?

  1. Increase the blade tracking tolerance
  2. Add weight at the blade tip to shift the chordwise balance
  3. Remove material from the trailing edge skin
  4. Add weight along the leading edge near the tip Correct answer.

Explanation

A tail-heavy blade has its chordwise centre of gravity too far aft, so mass must be added forward, typically along the leading edge, to move the centre of gravity to the specified position. Manufacturers specify the location and limits for balance weights.

Question 4Rotorcraft airframe systems and structures

What is the purpose of the swashplate assembly in a helicopter rotor control system?

  1. To provide the drive for the tail rotor
  2. To absorb lead-lag loads from the blades
  3. To transfer engine torque to the main rotor mast
  4. To convert non-rotating control inputs into rotating blade pitch changes Correct answer.

Explanation

The swashplate has a non-rotating and a rotating ring; the non-rotating ring is tilted or raised by the flight controls, and the rotating ring transfers that motion through pitch links to the blades. This is how collective and cyclic inputs reach a rotating rotor head.

Question 5Rotorcraft airframe systems and structures

A helicopter main rotor blade shows a small nick on the leading edge of the stainless steel abrasion strip. Which document governs whether the blade may remain in service?

  1. The airworthiness directive index
  2. The engine maintenance manual
  3. The aircraft flight manual limitations section only
  4. The blade manufacturer's maintenance manual damage tolerance charts Correct answer.

Explanation

Blade damage limits such as nick depth, length and spacing are published by the blade or rotor system manufacturer in the maintenance manual. The flight manual does not contain structural repair limits, and generic documents cannot substitute for the specific charts.

Question 6Rotorcraft airframe systems and structures

In a helicopter tail boom, what is the primary structural role of the vertical fin?

  1. To provide directional stability and counteract main rotor torque in cruise Correct answer.
  2. To carry the tail rotor thrust loads into the boom
  3. To support the horizontal stabiliser only
  4. To house the tail rotor drive shaft bearings

Explanation

The vertical fin provides weathercock stability and, in forward flight, offsets some of the main rotor torque so less tail rotor thrust is needed. Tail rotor thrust loads are carried by the tail rotor gearbox and its mounting structure.

Question 7Rotorcraft airframe systems and structures

Why are most helicopter tail rotor drive shafts supported by hanger bearings at intervals along the tail boom?

  1. To prevent whirling and excessive shaft deflection between supports Correct answer.
  2. To allow the shaft to be dismantled in flight
  3. To provide lubrication to the tail rotor gearbox
  4. To increase the shaft rotational speed

Explanation

A long, slender drive shaft would tend to whirl and deflect at its critical speed, so hanger bearings support it at intervals to keep the shaft stable. They also help accommodate boom flexing and alignment.

Question 8Rotorcraft airframe systems and structures

On a skid-type landing gear, what is the purpose of the cross tubes?

  1. To provide attachment for the ground handling wheels only
  2. To act as the primary anti-torque device
  3. To carry fuel between the skids
  4. To attach the skids to the airframe and absorb landing loads Correct answer.

Explanation

Cross tubes connect the two skids and attach the gear to the fuselage, and they flex to absorb landing and ground loads. They are the main structural members transferring gear loads into the airframe.

Question 9Rotorcraft airframe systems and structures

A helicopter is fitted with skid landing gear and the skid shoes are worn through to the tube. What is the correct course of action?

  1. Replace or repair the skid tube in accordance with the maintenance manual Correct answer.
  2. Reduce the maximum landing weight and continue
  3. Continue in service if the tube is not punctured
  4. Apply paint to the worn area and return to service

Explanation

Skid shoes protect the tube from abrasion, and wear through to the tube means the protective and structural limits may be exceeded. The maintenance manual defines allowable wear and the repair or replacement scheme, which must be followed.

Question 10Rotorcraft airframe systems and structures

What is the function of the collective pitch control in a helicopter?

  1. To change the pitch of all blades equally and thereby control rotor thrust Correct answer.
  2. To control engine power directly through the throttle only
  3. To tilt the rotor disc fore and aft for pitch attitude
  4. To vary tail rotor pitch for yaw control

Explanation

The collective changes pitch on all blades simultaneously and equally, increasing or decreasing total rotor thrust. Cyclic tilts the disc for directional control, and the tail rotor pedals handle yaw.

Question 11Rotorcraft airframe systems and structures

A main rotor blade tracking check shows one blade flying higher than the others in the same azimuth. Which adjustment is typically used to correct this on a conventional articulated head?

  1. Mast nut torque
  2. Drag hinge damper replacement
  3. Pitch link length adjustment Correct answer.
  4. Swashplate bearing preload

Explanation

Blade tracking is corrected by adjusting the pitch link length so each blade flies in the same tip path plane at a given azimuth. The maintenance manual gives the tracking procedure and limits.

Question 12Rotorcraft airframe systems and structures

What type of stress is primarily carried by the main rotor mast in a helicopter during normal flight?

  1. Combined tension, bending and torsion Correct answer.
  2. Torsion from engine torque only
  3. Pure shear from blade drag
  4. Compression only

Explanation

The mast carries engine torque as torsion, rotor thrust as tension, and bending moments from cyclic flapping and coning. The mast is therefore designed for a combined loading condition, not a single stress type.

Question 13Rotorcraft airframe systems and structures

On a helicopter with a bearingless main rotor head, how is blade flapping motion accommodated?

  1. Through sliding splines on the mast
  2. Through flexure of the composite yoke or strap Correct answer.
  3. Through the drag hinge only
  4. Through a conventional flapping hinge pin

Explanation

A bearingless head uses a flexible composite yoke or strap that bends to allow flapping, lead-lag and pitch change. This eliminates conventional hinges and bearings and reduces part count and maintenance.

Question 14Rotorcraft airframe systems and structures

Why is the tail rotor gearbox mounted on the vertical fin rather than at the end of a long unsupported shaft?

  1. To allow the tail rotor to turn in either direction
  2. To reduce the number of drive shaft sections and shorten the unsupported shaft length Correct answer.
  3. To increase tail rotor thrust by raising its position
  4. To eliminate the need for tail rotor pitch control

Explanation

Mounting the gearbox at the fin places the final drive close to the tail rotor and allows the shaft to be supported in shorter sections, reducing whirling and vibration. The position is dictated by structural and driveline considerations.

Question 15Rotorcraft airframe systems and structures

A helicopter has a rigid rotor head with no flapping hinges. How are flapping moments handled?

  1. By the swashplate bearings
  2. By the flexibility of the blades and hub absorbing the moments Correct answer.
  3. By the drag hinges alone
  4. By the tail rotor compensating

Explanation

A rigid rotor relies on blade and hub flexibility to accommodate the flapping that would otherwise be absorbed by hinges. The blades bend at the root, and the hub is designed to withstand the resulting moments.

Question 16Rotorcraft airframe systems and structures

What is the purpose of the static droop stops on a main rotor head?

  1. To limit blade flapping upward in high-g manoeuvres
  2. To lock the swashplate during maintenance
  3. To set the collective pitch range
  4. To limit blade flapping downward when the rotor is stationary or turning slowly Correct answer.

Explanation

Droop stops prevent blades from drooping excessively and striking the tail boom or fuselage when rotor speed is low and centrifugal force is insufficient to keep them coned. They are distinct from flapping stops that limit upward motion.

Question 17Rotorcraft airframe systems and structures

What is the primary structural function of the helicopter fuselage keel beam in a skid-equipped airframe?

  1. To house the avionics bay only
  2. To mount the tail rotor gearbox
  3. To carry landing loads and provide a continuous load path across the belly Correct answer.
  4. To support the main rotor mast only

Explanation

The keel beam runs along the belly and provides a continuous structural path that carries landing and ground handling loads into the airframe. It is a primary load-bearing member of the fuselage structure.

Question 18Rotorcraft airframe systems and structures

What is the purpose of the anti-flap or flapping stop in a helicopter rotor hub?

  1. To control the blade pitch angle
  2. To set the lead-lag angle
  3. To limit upward blade flapping travel and prevent excessive coning Correct answer.
  4. To prevent blades from drooping on shutdown

Explanation

Flapping stops limit the upward flapping travel of the blades so that coning and flapping angles stay within structural limits. Droop stops handle downward travel, and pitch and lead-lag are controlled by other means.

Question 19Rotorcraft airframe systems and structures

What is the reason for the coning angle built into a main rotor blade in flight?

  1. To balance the upward thrust with the downward centrifugal and weight forces Correct answer.
  2. To reduce tail rotor thrust requirements
  3. To increase blade pitch in forward flight
  4. To allow the blade to lead the hub in rotation

Explanation

In flight, rotor thrust acts upward on the blade while centrifugal force acts outward and blade weight acts downward, and the blade settles at a cone angle where these balance. The angle increases with thrust and decreases with rotor speed.

Question 20Rotorcraft airframe systems and structures

During a main rotor blade chordwise balance check, what does a leading-edge-heavy blade indicate?

  1. The blade is spanwise out of balance
  2. The blade tracking is out of adjustment
  3. The blade has excessive coning
  4. The chordwise centre of gravity is forward of the specified position Correct answer.

Explanation

Chordwise balance is about the position of the blade's centre of gravity along the chord line. A leading-edge-heavy blade has its centre of gravity too far forward, which may require weight added aft or material removed forward according to the manual.

Question 21Rotorcraft airframe systems and structures

What is the function of the tail rotor pitch change mechanism?

  1. To drive the tail rotor at constant speed
  2. To vary tail rotor blade pitch and control yaw thrust Correct answer.
  3. To balance the main rotor spanwise
  4. To support the tail rotor gearbox

Explanation

The tail rotor pitch change mechanism, operated by the anti-torque pedals, varies blade pitch to change tail rotor thrust and therefore yaw. Rotor speed is governed by the drive system, not by pitch change.

Question 22Rotorcraft airframe systems and structures

A helicopter main rotor blade has an elastomeric bearing in the lead-lag axis. What advantage does this offer over a conventional drag hinge with a friction damper?

  1. It increases blade flapping angle
  2. It allows the blade to change pitch without a pitch link
  3. It removes the need for blade tracking
  4. It eliminates the need for lubrication and reduces maintenance Correct answer.

Explanation

Elastomeric bearings use bonded rubber and metal layers that flex without sliding surfaces, so they need no lubrication and require less maintenance than conventional bearings and dampers. They still perform the same lead-lag function.

Question 23Rotorcraft airframe systems and structures

What is the primary purpose of the horizontal stabiliser on a helicopter tail boom?

  1. To improve pitch stability and reduce nose-down attitude in forward flight Correct answer.
  2. To carry the tail rotor gearbox loads
  3. To support the tail rotor drive shaft
  4. To provide anti-torque thrust

Explanation

The horizontal stabiliser generates a downward or upward aerodynamic force that improves pitch stability and helps maintain a more level attitude at speed. Anti-torque is provided by the tail rotor, and drive shaft support is a separate structural function.

Question 24Rotorcraft airframe systems and structures

A helicopter is parked with the rotor stationary and the blades are resting on their droop stops. What does this indicate?

  1. The blades have reached their maximum downward flapping limit Correct answer.
  2. The swashplate is locked in the full up position
  3. The blades are at their maximum coning angle
  4. The drag dampers have failed

Explanation

With no centrifugal force, blades droop until they contact the droop stops, which limit downward flapping travel. This is normal for a stationary rotor and protects the airframe from blade contact.

Question 25Rotorcraft airframe systems and structures

Why are the main rotor blade grips often made from titanium or steel rather than aluminium alloy?

  1. To reduce the weight of the rotor head
  2. To improve the aerodynamic shape of the blade root
  3. To withstand the high alternating loads and fatigue at the blade root attachment Correct answer.
  4. To allow the blade to be folded more easily

Explanation

Blade grips carry concentrated alternating loads from flapping, lead-lag and centrifugal force, so they need high fatigue strength and toughness. Titanium and steel provide this better than aluminium alloy in this highly stressed location.

Question 26Rotorcraft airframe systems and structures

On a helicopter with a fully articulated main rotor head, what is the function of the lead-lag (drag) hinge?

  1. It locks the blade to the hub so that all in-plane loads pass directly into the mast.
  2. It permits blade pitch to change without loading the pitch link in torsion.
  3. It allows the blade to rise and fall about the hub to accommodate dissymmetry of lift.
  4. It allows the blade to accelerate and decelerate in the plane of rotation as its in-plane velocity varies around the disc. Correct answer.

Explanation

In forward flight each blade's in-plane velocity changes through the cycle, producing Coriolis and periodic drag forces. The lead-lag hinge lets the blade move fore and aft in the disc plane so those loads are absorbed by a damper rather than being fed into the hub as bending. Flapping, by contrast, is handled by the flapping hinge.

Question 27Rotorcraft airframe systems and structures

A main rotor blade is found to have a spanwise centre of gravity forward of the feathering axis. What is the practical consequence for the rotor system?

  1. The blade will vibrate only in the lead-lag plane at the rotor's rotational frequency.
  2. The blade will tend to twist toward increased pitch, loading the pitch link and promoting flutter. Correct answer.
  3. There is no consequence provided the blade is statically balanced chordwise.
  4. The blade will tend to twist nose-down and increase pitch as centrifugal force acts on the offset mass.

Explanation

With the mass ahead of the feathering axis, centrifugal force produces a moment that twists the blade toward higher pitch. This loads the pitch control system and reduces flutter margin, which is why blades are built with the chordwise centre of gravity at or slightly aft of the feathering axis.

Question 28Rotorcraft airframe systems and structures

What is the purpose of the swashplate assembly in a helicopter rotor system?

  1. It transfers non-rotating control inputs from the fuselage to the rotating blades while allowing the rotor to turn. Correct answer.
  2. It supports the mast in the transmission and carries rotor thrust into the airframe.
  3. It damps lead-lag motion of each blade in the rotating system.
  4. It provides the gear reduction between the engine and the main rotor mast.

Explanation

The swashplate has a stationary ring that receives inputs from the cyclic and collective, and a rotating ring that turns with the mast and drives the pitch links. This lets pitch commands pass from a non-rotating frame into the rotating blade system.

Question 29Rotorcraft airframe systems and structures

In a helicopter tail boom of semi-monocoque construction, what is the primary role of the skin?

  1. It acts purely as a fairing and carries no structural load.
  2. It carries only torsional loads, with all bending taken by the internal frames.
  3. It carries shear and, being stabilised by stringers and frames, contributes significantly to bending strength. Correct answer.
  4. It carries the tail rotor thrust as a pure axial tension load.

Explanation

In semi-monocoque structure the skin is stabilised by stringers and frames and works in shear and tension to resist bending and torsion. It is a load-carrying member, not merely a cover, which is why skin damage and fastener condition are structurally significant.

Question 30Rotorcraft airframe systems and structures

During inspection, a crack is found at a bolt hole in an aluminium alloy tail boom frame. Which repair approach is normally acceptable?

  1. Assess against the approved structural repair manual and fit a doubler or replacement frame as specified. Correct answer.
  2. Stop-drill the crack and return the aircraft to service without further assessment.
  3. Fill the crack with structural adhesive and apply a protective coating.
  4. Weld the crack using standard aluminium filler rod and dress flush.

Explanation

Structural repairs must follow approved data, and for a crack at a bolt hole this typically means a specified doubler, oversize fastener scheme or frame replacement. Heat-treatable aluminium alloys used in airframes are generally not field-weldable to restore strength, so welding is not an approved remedy.

Question 31Rotorcraft airframe systems and structures

What is the function of the freewheel unit (sprag clutch) in a helicopter transmission?

  1. It provides the final gear reduction to the main rotor mast.
  2. It disconnects the tail rotor drive during autorotation.
  3. It limits torque to the main gearbox during hard collective pulls.
  4. It allows the rotor to overrun the engine so that the rotor can autorotate if engine power is lost. Correct answer.

Explanation

The freewheel unit transmits engine torque in one direction only. If engine power falls below rotor speed, the rotor overruns the drive so that it can continue turning and autorotation is possible. It also permits one engine to drive the system in a multi-engine installation.

Question 32Rotorcraft airframe systems and structures

Why must the tail rotor drive shafting in a helicopter be aligned and balanced to close tolerances?

  1. To prevent the shaft from turning faster than the tail rotor gearbox rating.
  2. To maintain a fixed tail rotor pitch setting.
  3. To limit whirl and vibration that would otherwise load the hanger bearings and couplings. Correct answer.
  4. To ensure the shaft can be removed without disturbing the gearboxes.

Explanation

A misaligned or unbalanced shaft produces whirl and vibration that rapidly distress hanger bearings, couplings and the boom structure. Alignment and balance keep the shaft running smoothly within its critical speed margin.

Question 33Rotorcraft airframe systems and structures

A helicopter with skid landing gear has a hard landing. Which inspection finding would most strongly indicate that the airframe absorbed significant energy?

  1. Light scuffing on the skid tube end caps.
  2. Loose fasteners on the skid shoe retaining clips.
  3. Paint worn through on the underside of the skid shoes.
  4. Permanent set or wrinkling of the cross tubes and deformation of the attachment saddles. Correct answer.

Explanation

The cross tubes and their attachments are designed to deflect and absorb landing energy. Permanent deformation or wrinkling indicates the structure has yielded and requires assessment against the maintenance manual limits. Cosmetic wear on shoes is normal service wear.

Question 34Rotorcraft airframe systems and structures

What is the purpose of the hydraulic damper fitted between the blade and hub on some articulated rotor heads?

  1. To damp lead-lag oscillation and prevent ground resonance. Correct answer.
  2. To lock the blade during rotor start-up.
  3. To hold the blade at a fixed coning angle in flight.
  4. To provide the force needed to change blade pitch.

Explanation

The damper resists in-plane (lead-lag) motion of the blade. Without adequate damping, the lead-lag oscillation can couple with the airframe on its landing gear and develop ground resonance, so damper condition is a critical airworthiness item.

Question 35Rotorcraft airframe systems and structures

On a helicopter, which component reacts the torque of the main gearbox to the fuselage?

  1. The gearbox mounting struts and their attachments, often through a torque reaction link. Correct answer.
  2. The swashplate rotating ring.
  3. The collective pitch lever quadrant.
  4. The mast thrust bearing.

Explanation

Engine torque delivered to the rotor produces an equal and opposite reaction on the gearbox casing. This is carried into the fuselage through the gearbox mounts and, where fitted, a dedicated torque reaction link so the fuselage does not rotate under the rotor.

Question 36Rotorcraft airframe systems and structures

What is the primary function of the engine-to-transmission coupling in a helicopter drivetrain?

  1. To provide the gear reduction from engine to main rotor.
  2. To measure engine torque for the cockpit gauge.
  3. To transmit torque while accommodating small misalignments between engine and gearbox shafts. Correct answer.
  4. To act as the rotor brake during shutdown.

Explanation

The coupling transmits drive torque and tolerates the small angular and axial misalignments inevitable between separately mounted engine and gearbox. Flexible elements such as diaphragm or elastomeric couplings are used, and their condition is critical because failure means total loss of drive.

Question 37Rotorcraft airframe systems and structures

A helicopter main rotor blade shows a small nick on the leading-edge abrasion strip that is within the permitted limits. What is the correct action?

  1. Leave it untouched and record it as deferred until the next major inspection.
  2. Replace the blade because any leading-edge damage is unserviceable.
  3. Apply a patch of aluminium tape over the nick.
  4. Blend out the damage in accordance with the maintenance manual and restore the surface finish. Correct answer.

Explanation

Damage within published limits is normally blended out to a smooth profile using the method and depth limits in the maintenance manual, then the protective finish is restored. This prevents stress concentration and further cracking while keeping the blade serviceable.

Question 38Rotorcraft airframe systems and structures

Why is the main rotor mast in many helicopters designed as a hollow tube?

  1. To allow the pitch links to pass through its centre.
  2. To carry bending and torsion efficiently while minimising weight and providing a route for control rods or wiring. Correct answer.
  3. To permit the mast to flex and provide flapping.
  4. To allow oil to circulate from the gearbox to the rotor head.

Explanation

A hollow section places material away from the neutral axis, giving high bending and torsional stiffness for low weight. The bore also provides a convenient route for control rods or wiring in some designs. Flapping is not obtained by mast flexing in a conventional design.

Question 39Rotorcraft airframe systems and structures

What does a spectrometric oil analysis programme on a helicopter main gearbox primarily detect?

  1. The presence of water in the oil.
  2. Incorrect oil viscosity at operating temperature.
  3. Blockage of the oil filter element.
  4. The onset of abnormal wear by identifying elevated concentrations of specific wear metals. Correct answer.

Explanation

Spectrometric oil analysis measures the concentration of wear metals such as iron, copper and aluminium in the oil. A trend of rising levels indicates abnormal wear of particular components, giving early warning before a failure develops.

Question 40Rotorcraft airframe systems and structures

A helicopter exhibits a vertical vibration that is worst at the rotor's rotational frequency (1 per rev). Which area should be investigated first?

  1. Main rotor blade tracking and balance. Correct answer.
  2. Engine compressor balance.
  3. Tail rotor balance and driveshaft alignment.
  4. Landing gear damper condition.

Explanation

A once-per-revolution vertical vibration is characteristically associated with the main rotor system, such as out-of-track or out-of-balance blades. Tail rotor and engine problems normally appear at their own higher frequencies.

Question 41Rotorcraft airframe systems and structures

What is the purpose of the collective pitch stick in a helicopter?

  1. It controls tail rotor pitch for yaw.
  2. It changes the pitch of all main rotor blades together to control total rotor thrust. Correct answer.
  3. It selects rotor brake operation on the ground.
  4. It changes blade pitch cyclically to tilt the rotor disc.

Explanation

The collective raises or lowers the pitch of all blades simultaneously, changing total lift and therefore climb or descent, and is normally linked to engine power control. Cyclic pitch, which tilts the disc, is a separate control.

Question 42Rotorcraft airframe systems and structures

Why are the pitch change bearings in a tail rotor hub inspected for freedom of movement and wear?

  1. Because they set the tail rotor coning angle.
  2. Because they transmit drive torque from the gearbox to the blades.
  3. Because stiffness or wear prevents full pitch range and can cause control feedback or blade flutter. Correct answer.
  4. Because they carry the tail rotor thrust into the gearbox.

Explanation

The pitch change bearings must allow smooth rotation of the blade about its feathering axis through the full range. Stiffness or excessive play restricts pitch authority and can produce control feedback or flutter, so freedom of movement is checked during inspection.

Question 43Rotorcraft airframe systems and structures

A helicopter is fitted with a bearingless main rotor head using composite flexure arms. What maintenance concern is most important for these flexures?

  1. Measuring the flexure's electrical resistance to confirm bonding.
  2. Detection of delamination, cracks or fibre damage that would reduce their stiffness and fatigue life. Correct answer.
  3. Checking that the flexure pivot bolts are free to rotate.
  4. Verifying that the flexure can be bent to full flapping travel by hand without load.

Explanation

Composite flexures carry flap, lag and pitch motions by elastic bending, so their integrity depends on the laminate being free of delamination, cracks and impact damage. Such defects reduce stiffness and fatigue life and can lead to catastrophic failure, so they are inspected carefully.

Question 44Rotorcraft airframe systems and structures

What is the function of the transmission oil cooler in a helicopter?

  1. To filter metallic particles from the oil.
  2. To remove heat generated by gear meshing and bearing friction so oil temperature stays within limits. Correct answer.
  3. To pressurise the gearbox for seal integrity.
  4. To heat the oil during cold starts.

Explanation

Gear and bearing friction generates substantial heat in the main gearbox, and the oil cooler rejects this to the air or fuel so that oil temperature remains within the approved range. Overheating degrades the oil and risks component damage.

Question 45Rotorcraft airframe systems and structures

In a helicopter, what is the structural significance of the main rotor mast-to-gearbox attachment?

  1. It allows the mast to be removed without supporting the rotor head.
  2. It transmits rotor thrust, bending moments and torque into the gearbox casing and hence the airframe. Correct answer.
  3. It carries the collective control input to the swashplate.
  4. It provides the feathering axis for the blades.

Explanation

The mast attachment is a primary load path. It transfers rotor thrust, in-plane loads and the resulting bending moments, plus drive torque, into the gearbox and airframe, so its condition and correct assembly are critical to structural integrity.

Question 46Rotorcraft airframe systems and structures

What is the purpose of the horizontal stabiliser on the tail boom of some helicopters?

  1. To support the tail rotor gearbox structurally.
  2. To counteract main rotor torque in the hover.
  3. To improve pitch stability and control in forward flight by generating a restoring moment. Correct answer.
  4. To provide additional lift in the hover.

Explanation

The horizontal stabiliser produces aerodynamic forces that damp pitch disturbances and improve longitudinal stability in forward flight. It is not effective in the hover because there is little airflow over it.

Question 47Rotorcraft airframe systems and structures

A helicopter tail rotor blade has a spanwise centre of gravity displaced from the feathering axis. What is the main concern?

  1. Increased tail rotor drive shaft torque.
  2. Excessive tail rotor coning in the hover.
  3. Loss of tail rotor thrust.
  4. Flutter and high loads in the pitch change mechanism. Correct answer.

Explanation

A mass offset from the feathering axis produces centrifugal twisting moments that load the pitch change mechanism and reduce flutter margin. Tail rotor blades are therefore balanced chordwise as well as spanwise.

Question 48Rotorcraft airframe systems and structures

What is the function of the rotor brake on a helicopter?

  1. To limit rotor overspeed during flight.
  2. To lock the swashplate during maintenance.
  3. To hold the rotor stationary during shutdown and reduce the time to stop. Correct answer.
  4. To prevent the rotor from autorotating in the event of engine failure.

Explanation

The rotor brake is applied on the ground to stop and hold the rotor after shutdown, reducing the time the rotor takes to coast down and preventing wind-driven rotation. It is not used in flight.

Question 49Rotorcraft airframe systems and structures

Why is a helicopter tail boom often attached to the fuselage with a bolted joint rather than being welded?

  1. To allow the boom to be removed and to avoid heat effects on heat-treated alloys. Correct answer.
  2. To allow the boom to flex freely in flight.
  3. Because bolts are lighter than welds.
  4. Because welded joints cannot carry bending loads.

Explanation

Bolted joints allow the boom to be detached for transport or repair and avoid welding heat effects in aluminium alloys that would reduce strength. Correctly designed bolted joints are fully capable of carrying the boom loads.

Question 50Rotorcraft airframe systems and structures

What does the term 'ground resonance' describe in a helicopter with an articulated rotor?

  1. Vibration caused by the tail rotor at ground idle.
  2. A self-excited coupling between in-plane blade motion and airframe rocking on its landing gear. Correct answer.
  3. The vibration felt when the skids contact the ground on landing.
  4. The tendency of the rotor to overspeed during autorotation.

Explanation

Ground resonance occurs when the lead-lag motion of the blades couples with the airframe rocking on its landing gear, causing the oscillation to grow rapidly. Adequate lead-lag damping and correct landing gear condition prevent it.