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CPL Helicopter study materials
CPL Helicopter study resources

CPL Helicopter practice questions

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Question 1Air Law and Operational Procedures

Under ICAO rules, what is the minimum horizontal distance a helicopter must maintain from cloud when operating under visual flight rules in Class G airspace at 1,500 ft AMSL during the day?

  1. Clear of cloud and in sight of the surface
  2. 2,000 m
  3. 1,500 m Correct answer.
  4. 800 m

Explanation

For helicopters in Class G airspace at or below the altitude specified for the region, the VFR cloud-distance requirement is 1,500 m horizontally with the aircraft clear of cloud and in sight of the surface. The reduced distance reflects the helicopter's lower speed and manoeuvrability compared with fixed-wing aircraft.

Question 2Air Law and Operational Procedures

A helicopter is being operated for the purpose of aerial work over a congested area. What minimum height above the highest obstacle must normally be maintained?

  1. 500 ft
  2. 1,000 ft Correct answer.
  3. 1,500 ft
  4. 300 ft

Explanation

Operations over congested areas of a city, town or settlement normally require a minimum height of 1,000 ft above the highest obstacle within a specified horizontal radius. This protects people and property on the ground from the consequences of an engine failure.

Question 3Air Law and Operational Procedures

What is the primary purpose of the pre-flight briefing of passengers before a helicopter flight?

  1. To verify that passengers have paid for the flight
  2. To familiarise passengers with safety equipment and emergency procedures Correct answer.
  3. To satisfy insurance requirements for the operator
  4. To record passenger weights for the load sheet

Explanation

The pre-flight briefing ensures passengers know how to use seat belts, doors, exits and life-saving equipment and understand the actions to take in an emergency. It is a regulatory safety requirement, not an administrative formality.

Question 4Air Law and Operational Procedures

On a standard aerodrome, what does a white letter 'H' painted in a circle indicate?

  1. A heliport or touchdown/landing area Correct answer.
  2. A taxi route for helicopters
  3. A parking area for fixed-wing aircraft
  4. A prohibited landing area

Explanation

The letter H inside a circle or square marks the touchdown and lift-off area of a heliport. Markings and lighting around it guide the pilot to the intended aiming point.

Question 5Air Law and Operational Procedures

Which document must be carried on board and be available for inspection during an international flight?

  1. The aircraft certificate of registration Correct answer.
  2. The company operations manual only
  3. The pilot's personal logbook
  4. The operator's maintenance schedule

Explanation

The certificate of registration is one of the documents that must be carried on board for international operations, together with the certificate of airworthiness and crew licences. It establishes the nationality of the aircraft.

Question 6Air Law and Operational Procedures

What does a steady red light signal directed at a helicopter in flight mean?

  1. Give way and continue circling
  2. Continue flying, no significance
  3. Yield and continue, but be alert Correct answer.
  4. Land at the nearest aerodrome

Explanation

A steady red light shown to an aircraft in flight means the aircraft must give way to other traffic and continue circling, remaining alert. It does not order a landing, which is signalled differently.

Question 7Air Law and Operational Procedures

In which of the following situations is a helicopter required to file a flight plan?

  1. When conducting a private flight within controlled airspace
  2. When flying across an international border Correct answer.
  3. When flying locally within the aerodrome traffic circuit
  4. When carrying out a short training detail

Explanation

A flight plan is required for flights that cross international borders, and for other flights specified by the state such as those in controlled airspace where the authority requires it. Local circuit and training flights normally do not require one.

Question 8Air Law and Operational Procedures

A helicopter has a maximum certificated take-off mass of 2,500 kg. Under the standard mass categories, how is it classified?

  1. Light Correct answer.
  2. Medium
  3. Super
  4. Heavy

Explanation

Light helicopters are those with a maximum certificated take-off mass of 7,000 kg or less. The 2,500 kg example therefore falls within the light category.

Question 9Air Law and Operational Procedures

What is the purpose of a helicopter's certificate of airworthiness?

  1. It certifies the pilot's competence to fly the type
  2. It confirms the aircraft conforms to an approved design and is safe to operate Correct answer.
  3. It records the aircraft's maintenance history
  4. It authorises the operator to sell the aircraft

Explanation

The certificate of airworthiness confirms that the aircraft conforms to a type design approved by the state and is considered safe for flight when maintained in accordance with approved procedures. It is distinct from licensing of crew and from maintenance records.

Question 10Air Law and Operational Procedures

A pilot is flying a helicopter at night in Class G airspace. What minimum flight visibility must be maintained under standard ICAO VFR?

  1. 1,500 m
  2. 5 km Correct answer.
  3. 3 km
  4. 8 km

Explanation

For night VFR in Class G airspace, a flight visibility of at least 5 km is required, together with the standard cloud-clearance distances. The higher visibility reflects the reduced ability to see and avoid other traffic at night.

Question 11Air Law and Operational Procedures

What is the function of the aircraft's radio station licence?

  1. It authorises the installation and operation of radio equipment on the aircraft Correct answer.
  2. It certifies the radio equipment's serviceability
  3. It permits the aircraft to enter controlled airspace
  4. It authorises the pilot to use the radio

Explanation

The radio station licence is issued for the aircraft and authorises the installation and operation of the radio communication equipment fitted. The pilot's authority to transmit comes from the licence held by the pilot, not from the aircraft station licence.

Question 12Air Law and Operational Procedures

An aircraft is on final approach and a green light is flashed at it by the tower. What action should the pilot take?

  1. Continue circling and give way
  2. Land, but be prepared to go around Correct answer.
  3. Stop immediately
  4. Return to the starting point

Explanation

A series of green flashes directed at an aircraft on approach clears it to land, but the pilot must still be prepared to go around if the landing cannot be completed safely. The signal grants clearance, not an obligation to touch down.

Question 13Air Law and Operational Procedures

What does the abbreviation 'ATIS' stand for in aeronautical communications?

  1. Aircraft Tracking and Identification Service
  2. Automatic Traffic Information System
  3. Aerodrome Terminal Information Service Correct answer.
  4. Air Traffic Information Standard

Explanation

ATIS is the Aerodrome Terminal Information Service, which broadcasts current aerodrome information such as weather, runway in use and other operational data. Pilots use it to obtain essential information before contacting ATC.

Question 14Air Law and Operational Procedures

A helicopter is operating under IFR and the pilot loses radio communication. What is the standard action to take?

  1. Continue according to the last acknowledged clearance or the filed flight plan and land as soon as practicable Correct answer.
  2. Return to the departure aerodrome without delay
  3. Land immediately at the nearest suitable site
  4. Climb to the highest available level and circle

Explanation

When radio communication is lost, the pilot should continue in accordance with the last acknowledged clearance or, if none, the filed flight plan, and land as soon as practicable at a suitable aerodrome. The aim is to maintain a predictable, safe flight path.

Question 15Air Law and Operational Procedures

What does a flashing red light directed at a helicopter on the ground mean?

  1. Continue taxiing
  2. Return to the apron
  3. Taxi clear of the landing area
  4. Stop and hold position Correct answer.

Explanation

A flashing red light directed at an aircraft or vehicle on the ground means stop and hold position. It is a mandatory instruction from the tower and must be complied with immediately.

Question 16Air Law and Operational Procedures

Which of the following best describes a 'controlled flight into terrain' (CFIT) accident?

  1. An aircraft suffers structural failure in flight and descends out of control
  2. An aircraft collides with another aircraft on the ground
  3. An aircraft is flown into terrain or water while under control, usually because the crew is unaware of the hazard Correct answer.
  4. An aircraft is struck by lightning and loses control

Explanation

CFIT occurs when an airworthy aircraft under crew control is flown into terrain or water, typically because the crew is unaware of the impending hazard. It is a leading cause of fatal accidents and is addressed by terrain awareness and crew resource management training.

Question 17Air Law and Operational Procedures

A helicopter pilot wishes to operate in an area where a temporary restricted area has been established. What is the normal requirement?

  1. The pilot may enter if the flight is conducted under VFR
  2. Permission must be obtained from the authority responsible for the restriction Correct answer.
  3. No action is required if the flight is below 500 ft
  4. The pilot may enter provided the transponder is switched on

Explanation

Entry into a restricted area normally requires prior permission from the authority that established the restriction. The restriction exists because of a specific hazard or activity, and VFR or altitude alone does not grant access.

Question 18Air Law and Operational Procedures

What is the standard phraseology used to acknowledge a clearance that requires readback?

  1. 'Roger' followed by the callsign
  2. Read back the clearance in full, including the callsign Correct answer.
  3. 'Affirm' followed by the callsign
  4. 'Wilco' followed by the callsign

Explanation

Clearances that must be read back, such as route, altitude and frequency instructions, should be read back in full with the aircraft callsign to confirm correct reception. 'Roger' and 'Wilco' acknowledge receipt but do not confirm the content.

Question 19Air Law and Operational Procedures

A helicopter is approaching an aerodrome where the windsock indicates a strong crosswind exceeding the aircraft's demonstrated crosswind limit. What is the correct course of action?

  1. Land anyway because the windsock is advisory
  2. Reduce approach speed to compensate
  3. Proceed to an alternative aerodrome or runway with acceptable conditions Correct answer.
  4. Increase approach angle to shorten exposure

Explanation

The demonstrated crosswind limit is a limiting value for the aircraft and must be respected. If conditions exceed it, the pilot should divert to a suitable alternative rather than attempt a landing outside the limit.

Question 20Air Law and Operational Procedures

In the event of an engine failure in a helicopter, what is the primary purpose of the autorotative descent?

  1. To reduce the rate of descent to zero
  2. To increase forward speed for a forced landing
  3. To restart the engine using airflow
  4. To maintain rotor RPM and use the stored energy to make a controlled landing Correct answer.

Explanation

Autorotation uses the upward flow of air through the rotor to keep the blades turning and store energy, allowing a controlled descent and landing after engine failure. The rotor RPM must be managed carefully to preserve this energy.

Question 21Air Law and Operational Procedures

A helicopter is being dispatched on a flight over water beyond gliding distance from land. What equipment is normally required?

  1. A fire extinguisher only
  2. A spare set of rotor blades
  3. Only a first-aid kit
  4. Life jackets for each occupant and a life raft Correct answer.

Explanation

Flights over water beyond gliding distance from land require flotation equipment such as life jackets for each occupant and a life raft, together with associated survival equipment. These items provide a means of survival after a ditching.

Question 22Air Law and Operational Procedures

A pilot is planning a flight that will cross several national boundaries. Which statement about the carriage of documents and the flight plan is correct?

  1. Only the pilot licence is required on board
  2. The flight plan may be filed after departure
  3. No flight plan is needed if the flight remains below 1,000 ft
  4. The flight plan must be filed and the aircraft documents, including registration and airworthiness certificates, must be carried Correct answer.

Explanation

International flights require a flight plan to be filed before departure and the aircraft must carry its registration and airworthiness certificates and crew licences. These requirements ensure identification, airworthiness and crew competence can be verified.

Question 23Air Law and Operational Procedures

What is the purpose of a 'clearance limit' in an ATC clearance?

  1. The minimum fuel required for the flight
  2. The time by which the aircraft must land
  3. The point to which the aircraft is cleared to proceed Correct answer.
  4. The maximum altitude the aircraft may fly

Explanation

The clearance limit is the point to which an aircraft is cleared to proceed, such as an aerodrome or a navigation fix. Beyond that point the aircraft must obtain a further clearance before continuing.

Question 24Air Law and Operational Procedures

A helicopter is operating in Class C airspace. What is required of the pilot?

  1. An ATC clearance is required and the aircraft must be equipped as specified Correct answer.
  2. Only a radio is required
  3. The pilot may operate without a transponder at all times
  4. No clearance is required if the flight is VFR

Explanation

Class C airspace requires an ATC clearance for all flights and mandates specified communication, navigation and surveillance equipment, typically including a transponder. VFR flight does not exempt the pilot from these requirements.

Question 25Aircraft General Knowledge – Airframe, Systems and Powerplant

In a semi-rigid rotor system, what is the primary function of the elastomeric or flapping hinge assembly at the blade root?

  1. To allow the blade to feather freely without any pilot input
  2. To lock the blade pitch at a fixed angle during all flight phases
  3. To permit individual blade flapping while transmitting centrifugal and driving loads to the hub Correct answer.
  4. To eliminate the need for a tail rotor anti-torque system

Explanation

A semi-rigid head uses a hinge that lets each blade flap up and down to relieve the lift asymmetry in forward flight, while still carrying centrifugal force and driving torque into the mast. Pitch change is controlled separately through the pitch horn and control links, not by the flapping hinge.

Question 26Aircraft General Knowledge – Airframe, Systems and Powerplant

Why is a freewheeling unit (sprag clutch) fitted between the engine and the main rotor transmission?

  1. To disconnect the tail rotor drive during ground handling
  2. To allow the rotor to keep turning after engine power is lost so autorotation remains possible Correct answer.
  3. To step up rotor RPM to a value higher than engine RPM
  4. To smooth out engine torque pulses before they reach the mast

Explanation

The freewheeling unit transmits drive in one direction only, so when engine RPM falls below rotor RPM the rotor can overrun the transmission. This decoupling is what allows the rotor to keep rotating and produce lift in autorotation after a power failure.

Question 27Aircraft General Knowledge – Airframe, Systems and Powerplant

During a normal start of a turboshaft engine fitted with a starter-generator, which sequence best describes the start cycle?

  1. The starter cranks the engine to full rated RPM before any fuel is admitted
  2. Fuel is admitted at zero RPM and the combustion gases spin the compressor up
  3. The starter cranks the compressor to a self-sustaining speed, then fuel and ignition are introduced Correct answer.
  4. Ignition and fuel are introduced first, then the starter motor cranks the compressor

Explanation

The starter must accelerate the compressor to a speed where airflow and compression are sufficient to support combustion and where the turbine can then take over. Fuel and ignition are introduced only after the engine has reached the correct motoring speed, and the starter drops out at self-sustaining speed.

Question 28Aircraft General Knowledge – Airframe, Systems and Powerplant

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

  1. To convert non-rotating pilot control inputs into rotating blade pitch changes Correct answer.
  2. To measure rotor RPM for the tachometer indication
  3. To provide the mechanical drive from the engine to the tail rotor
  4. To absorb the centrifugal loads generated by the rotor blades

Explanation

The swashplate has a stationary lower ring moved by the cyclic and collective, and a rotating upper ring linked to the blade pitch horns. Tilting or raising the swashplate therefore changes blade pitch cyclically or collectively as the blades rotate.

Question 29Aircraft General Knowledge – Airframe, Systems and Powerplant

A helicopter is fitted with a skid-type landing gear. What is the main advantage of this arrangement compared with wheels?

  1. It allows the helicopter to be steered on the ground
  2. It permits easier ground taxiing under power
  3. It provides better energy absorption in a hard landing
  4. It gives a lighter, simpler structure with fewer moving parts Correct answer.

Explanation

Skid gear is a simple tubular structure with no wheels, brakes or oleo struts, so it saves weight and reduces maintenance. The trade-off is that ground handling requires wheels or a dolly and taxiing is not normally possible.

Question 30Aircraft General Knowledge – Airframe, Systems and Powerplant

In a hydraulically boosted helicopter control system, what happens if hydraulic pressure is lost in flight?

  1. Manual control forces rise and may require reduced speed and gentle inputs Correct answer.
  2. The cyclic becomes lighter because boost is removed
  3. The controls lock in their last position
  4. The rotor disc pitch automatically freezes at a fixed value

Explanation

Most light helicopter boost systems are irreversible or partially irreversible, so losing pressure leaves direct mechanical control but with much higher stick forces. The pilot must slow down and fly smoothly to stay within the available manual authority.

Question 31Aircraft General Knowledge – Airframe, Systems and Powerplant

What is the function of the tail rotor in a conventional single main rotor helicopter?

  1. To increase the rotor RPM during autorotation
  2. To counteract main rotor torque and provide yaw control Correct answer.
  3. To provide additional lift in forward flight
  4. To cool the main gearbox oil

Explanation

The main rotor torque reaction would spin the fuselage in the opposite direction, and the tail rotor thrust opposes this to hold heading. Varying tail rotor thrust through the pedals also gives the pilot yaw control.

Question 32Aircraft General Knowledge – Airframe, Systems and Powerplant

Why must the main rotor blades be free to flap (or the hub be flexible) in forward flight?

  1. To equalise lift between the advancing and retreating sides as relative airflow changes Correct answer.
  2. To permit the blade to be folded for storage in flight
  3. To allow the blade to change its chord length
  4. To reduce the rotor RPM at high forward speed

Explanation

The advancing blade sees a higher relative airspeed than the retreating blade, so without flapping it would produce much more lift and a large rolling moment. Flapping lets the advancing blade rise and the retreating blade descend, which balances the lift across the disc.

Question 33Aircraft General Knowledge – Airframe, Systems and Powerplant

What is the purpose of the collective pitch control?

  1. To tilt the rotor disc fore and aft for pitch attitude control
  2. To control the engine fuel flow directly
  3. To change blade pitch equally on all blades and thereby control total rotor thrust Correct answer.
  4. To vary tail rotor pitch for yaw control

Explanation

The collective raises or lowers the pitch of all blades simultaneously and equally, which changes the total thrust produced by the disc. Because thrust changes also affect power required, the collective is normally linked to the throttle or governor.

Question 34Aircraft General Knowledge – Airframe, Systems and Powerplant

A pilot notices that engine oil pressure is falling steadily while oil temperature rises in cruise. What is the most appropriate interpretation?

  1. Normal behaviour as the oil thins at operating temperature
  2. An indication that the oil cooler is over-cooling the oil
  3. A sign that the engine is running too rich
  4. A possible loss of oil or oil pump degradation requiring precautionary action Correct answer.

Explanation

Falling pressure combined with rising temperature suggests the oil is escaping, aerating or not being pumped efficiently, which can lead to rapid engine damage. The pilot should reduce power and land as soon as practicable rather than treat it as normal.

Question 35Aircraft General Knowledge – Airframe, Systems and Powerplant

What is the main purpose of a centrifugal compressor in a turboshaft engine?

  1. To mix fuel with air in the combustion chamber
  2. To raise the pressure of the incoming air before combustion Correct answer.
  3. To reduce the temperature of the exhaust gases
  4. To drive the tail rotor gearbox

Explanation

The compressor accelerates air outward and diffuses it, converting velocity into pressure so that combustion can occur at high pressure and the turbine can extract useful work. Fuel mixing and combustion occur downstream in the combustion chamber.

Question 36Aircraft General Knowledge – Airframe, Systems and Powerplant

During autorotation, what is the function of the tail rotor?

  1. To supply air to the engine for a relight
  2. To maintain heading and control yaw as torque is no longer present Correct answer.
  3. To increase the rate of descent for a steeper approach
  4. To drive the main rotor through the freewheeling unit

Explanation

With the engine disengaged there is no main rotor torque to oppose, but the tail rotor still provides yaw control and directional stability. The pilot uses the pedals to hold heading and to align the aircraft before touchdown.

Question 37Aircraft General Knowledge – Airframe, Systems and Powerplant

What is the purpose of the mast bumping limitation in a teetering (semi-rigid) rotor system?

  1. To prevent the blade tips from touching the tail boom
  2. To limit the maximum rotor RPM during autorotation
  3. To avoid excessive flapping that lets the hub contact the mast during low-G conditions Correct answer.
  4. To stop the swashplate from rotating with the mast

Explanation

In a teetering head the blades can flap so far that the hub strikes the mast if the disc is unloaded, as in a pushover or low-G manoeuvre. Pilots must avoid abrupt cyclic inputs that reduce disc loading and must respect the low-G limits.

Question 38Aircraft General Knowledge – Airframe, Systems and Powerplant

Which statement correctly describes the function of the engine governor (throttle correlator) in a piston helicopter?

  1. It controls the mixture strength at high altitude
  2. It limits the maximum altitude at which the helicopter can hover
  3. It disengages the clutch during autorotation
  4. It automatically adjusts throttle to maintain rotor RPM as collective pitch changes Correct answer.

Explanation

Raising collective increases the power required, which would otherwise drag rotor RPM down, so the correlator or governor opens the throttle to hold RPM. This reduces pilot workload and keeps the rotor within its operating range.

Question 39Aircraft General Knowledge – Airframe, Systems and Powerplant

What is the primary structural role of the main rotor mast?

  1. To act as the primary anti-torque structure
  2. To provide the oil supply path to the tail rotor gearbox
  3. To carry the rotor thrust and bending loads into the transmission and airframe Correct answer.
  4. To house the engine exhaust duct

Explanation

The mast transmits lift, thrust and bending moments from the rotor head down into the main gearbox and airframe structure. It is a highly loaded component and its fatigue life is carefully managed.

Question 40Aircraft General Knowledge – Airframe, Systems and Powerplant

Why is a torque meter or torquemeter fitted to a turboshaft helicopter?

  1. To indicate the tail rotor thrust available
  2. To measure the fuel flow to the combustion chamber
  3. To display the compressor inlet temperature
  4. To indicate the power being delivered to the rotor so the pilot can respect transmission limits Correct answer.

Explanation

Torque is a direct measure of the power the engine is delivering through the transmission, so it is used to keep within gearbox and drive-shaft limits. It is particularly important in hover and during high-power manoeuvres.

Question 41Aircraft General Knowledge – Airframe, Systems and Powerplant

What is the effect of retreating blade stall on helicopter handling?

  1. The aircraft pitches nose-down and rolls toward the advancing side
  2. The rotor RPM increases rapidly beyond limits
  3. The aircraft pitches nose-up and rolls toward the retreating side Correct answer.
  4. The tail rotor loses effectiveness first

Explanation

When the retreating blade reaches its critical angle of attack it stalls, reducing lift on that side, so the disc rolls toward the retreating blade and the aircraft pitches nose-up. The remedy is to reduce collective, increase rotor RPM and lower airspeed.

Question 42Aircraft General Knowledge – Airframe, Systems and Powerplant

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

  1. To prevent the blades from changing pitch
  2. To limit upward coning in high-G manoeuvres
  3. To hold the blades in the folded position during flight
  4. To limit downward blade flapping when the rotor is turning slowly or stopped Correct answer.

Explanation

At low rotor RPM there is little centrifugal force to hold the blades out, so they droop and could strike the tail boom or fuselage. Droop stops limit this downward travel, and they are normally disengaged once RPM builds up.

Question 43Aircraft General Knowledge – Airframe, Systems and Powerplant

Which of the following best describes the purpose of the combustion chamber in a gas turbine engine?

  1. To extract work from the exhaust gases to drive the compressor
  2. To compress the incoming air before it reaches the turbine
  3. To add heat energy to the air at approximately constant pressure Correct answer.
  4. To cool the turbine blades before they enter the exhaust

Explanation

In the combustion chamber fuel is burned with the compressed air, raising the gas temperature and energy content while pressure stays roughly constant. The hot high-energy gas then expands through the turbine and nozzle.

Question 44Aircraft General Knowledge – Airframe, Systems and Powerplant

What is the significance of the never-exceed rotor RPM (power-on) limit?

  1. Below this RPM the engine will not start
  2. Above this RPM the blade tips may reach supersonic speed and cause vibration and structural loads Correct answer.
  3. Above this RPM the tail rotor stops producing thrust
  4. Below this RPM the governor disengages

Explanation

Exceeding the upper RPM limit increases tip speed, which raises drag and can produce shock waves, vibration and high stresses on blades and hub. It also risks overspeeding the transmission, so the limit must be respected.

Question 45Aircraft General Knowledge – Airframe, Systems and Powerplant

What is the function of the clutch in a piston-engine helicopter drivetrain?

  1. To engage the engine drive gradually so the rotor is not shock-loaded at start Correct answer.
  2. To disconnect the tail rotor in flight
  3. To change the gear ratio between engine and rotor
  4. To allow the rotor to overrun the engine in autorotation

Explanation

At start the engine idles while the rotor is stationary, and the clutch brings the rotor up to speed smoothly without snatching. The one-way freewheeling unit, a separate component, handles autorotation overrun.

Question 46Aircraft General Knowledge – Airframe, Systems and Powerplant

Which statement about the static and dynamic rollover of a skid-equipped helicopter is correct?

  1. Dynamic rollover requires the engine to be shut down
  2. Dynamic rollover can occur when one skid is pivoting about a ground contact point with insufficient corrective cyclic Correct answer.
  3. Static rollover is caused by excessive rotor RPM
  4. Static rollover only happens with wheels

Explanation

If one skid is trapped or dragging while the other lifts, the aircraft pivots about that contact point and the rolling moment can grow faster than the pilot can correct. Prompt, correct cyclic input toward the raised side and lowering collective are required.

Question 47Aircraft General Knowledge – Airframe, Systems and Powerplant

What is the purpose of the engine bleed-air system on a turboshaft helicopter?

  1. To provide hydraulic pressure for the flight controls
  2. To cool the main gearbox oil
  3. To increase the fuel flow to the combustion chamber
  4. To supply compressed air for cabin heating, anti-ice and engine starting Correct answer.

Explanation

Bleed air is tapped from the compressor and used for services such as cabin heating, engine and airframe anti-ice, and sometimes for starting. Using bleed air reduces the power available, so it must be considered in performance planning.

Question 48Aircraft General Knowledge – Airframe, Systems and Powerplant

A helicopter with a fully articulated rotor head has flapping, lead-lag and feathering hinges. What is the purpose of the lead-lag hinge?

  1. To allow the blade to speed up and slow down in the disc plane as its drag varies Correct answer.
  2. To allow the blade to flap up and down
  3. To lock the blade to the hub for storage
  4. To allow the blade to change pitch during rotation

Explanation

As a blade advances and retreats, its airspeed and drag change, so it tends to accelerate and decelerate within the disc plane. The lead-lag hinge accommodates this in-plane motion and relieves the resulting chordwise loads, and dampers are usually fitted to control it.

Question 49Aircraft General Knowledge – Airframe, Systems and Powerplant

Why is a mixture control provided on a piston helicopter engine?

  1. To adjust the fuel-to-air ratio as altitude and temperature change Correct answer.
  2. To select the fuel tank in use
  3. To set the rotor RPM before takeoff
  4. To control the oil pressure in the engine

Explanation

As the aircraft climbs, air density falls, so the fuel flow must be leaned to keep the correct fuel-to-air ratio and avoid an over-rich mixture. The mixture control also allows the engine to be shut down by cutting the fuel supply.

Question 50Aircraft General Knowledge – Airframe, Systems and Powerplant

On a piston-engine helicopter, what is the purpose of the freewheeling unit (sprag clutch) in the transmission?

  1. It allows the rotor system to turn independently of the engine during autorotation Correct answer.
  2. It synchronises the engine and rotor RPM during start-up
  3. It limits engine torque to protect the main gearbox
  4. It disengages the tail rotor drive during ground handling

Explanation

The freewheeling unit is a one-way clutch that transmits drive from the engine to the rotor but overruns when the rotor turns faster than the engine. This lets the rotor keep turning after engine power is lost or the engine is idling, so autorotation remains possible. Without it, the rotor would be dragged down to engine speed and the glide capability would be lost.