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Iran CAO CPL Theory study materials
Iran CAO CPL Theory study resources

Iran CAO CPL Theory practice questions

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Question 1Air Law

Under the Chicago Convention, what does a State's territory include for the purpose of sovereignty over airspace?

  1. Land and its territorial waters Correct answer.
  2. Only territory leased from another State
  3. Land areas only, without any territorial sea
  4. The high seas and airspace above them

Explanation

Article 1 recognises complete and exclusive sovereignty over the airspace above a State's territory, and Article 2 defines that territory as the land areas and adjacent territorial waters under the State's sovereignty, suzerainty, protection or mandate. The high seas are not part of any State's territory, so no sovereignty over their airspace is acquired by this rule.

Question 2Air Law

What minimum age and medical certificate does an applicant for an Iranian CPL need under ICAO Annex 1?

  1. 21 years and a Class 1 medical certificate
  2. 18 years and no medical certificate if flying VFR
  3. 18 years and a Class 1 medical certificate Correct answer.
  4. 17 years and a Class 2 medical certificate

Explanation

ICAO Annex 1 sets the minimum age for a CPL at 18 years and requires a current Class 1 medical assessment. A Class 2 certificate is not sufficient for commercial pilot privileges.

Question 3Air Law

Which document carried on board an internationally operated aircraft proves its nationality and registration?

  1. The certificate of registration Correct answer.
  2. The aircraft radio station licence
  3. The journey logbook
  4. The certificate of airworthiness

Explanation

Annex 7 requires a certificate of registration showing the nationality and registration marks, and it is one of the documents carried on board under the Chicago Convention. The certificate of airworthiness proves airworthiness, while the radio station licence authorises the radio installation.

Question 4Air Law

A power-driven aeroplane and a glider are converging at approximately the same altitude, with the glider on the left. Under Annex 2, which aircraft has the right of way?

  1. The aeroplane, as it is faster
  2. Neither, as both must turn left
  3. The aeroplane, as it is on the right
  4. The glider Correct answer.

Explanation

Annex 2's converging rule normally gives right of way to the aircraft on the right, but it also requires power-driven heavier-than-air aircraft to give way to gliders, airships and balloons. The glider therefore has right of way even though it is on the left.

Question 5Air Law

An Iranian-registered aircraft crashes in Turkey. Under Annex 13, which State is primarily responsible for instituting the investigation?

  1. The State of the Operator
  2. The State of Registry
  3. The State of Occurrence Correct answer.
  4. The State of Manufacture

Explanation

Annex 13 places the responsibility for instituting an accident investigation on the State of Occurrence. Other States with a legitimate interest, such as the State of Registry, Operator or Manufacture, may participate but do not replace that primary responsibility.

Question 6Air Law

During flight, an emergency requires immediate action that would breach a rule of the air. What does Annex 2 permit the pilot-in-command to do?

  1. Deviate as necessary and report it Correct answer.
  2. Deviate only if the aircraft is outside controlled airspace
  3. Delegate the decision to the operator's duty officer
  4. Nothing; ATC clearance must be obtained first

Explanation

Annex 2 permits the pilot-in-command to deviate from the rules to the extent necessary in an emergency that requires immediate action. The pilot must notify air traffic services and submit a report if required, and remains responsible for the safe conduct of the flight.

Question 7Air Law

In an ICAO Annex, what distinguishes a Standard from a Recommended Practice?

  1. A Standard is mandatory for Contracting States; a Recommended Practice is desirable Correct answer.
  2. A Standard concerns aircraft design; a Recommended Practice concerns crew licensing
  3. A Standard is issued by ICAO; a Recommended Practice is issued by the State of Registry
  4. A Standard applies only to scheduled airlines; a Recommended Practice applies to general aviation

Explanation

ICAO Standards are mandatory specifications that Contracting States must apply, and any difference must be notified to ICAO. Recommended Practices are desirable specifications whose uniform application is recognised as beneficial, but they are not binding in the same way.

Question 8Air Law

A permanent change to an instrument approach procedure in Iran is published in which AIP element?

  1. A circular from the operator
  2. An AIP amendment Correct answer.
  3. An AIP supplement
  4. A NOTAM

Explanation

Permanent changes to AIP content are published through AIP amendments. AIP supplements normally carry temporary changes of long duration, while NOTAMs give short-notice temporary information.

Question 9Air Law

Under the Tokyo Convention 1963, which State has primary jurisdiction over an offence committed on board an aircraft in flight?

  1. The State overflown at the time of the offence
  2. The State of the operator's principal place of business
  3. The State where the next landing is made
  4. The State of registration of the aircraft Correct answer.

Explanation

The Tokyo Convention 1963 gives the State of registration primary jurisdiction over offences committed on board an aircraft in flight. Other States may exercise jurisdiction in specified circumstances, for example where the offence affects their territory or security.

Question 10Air Law

Under Article 33 of the Chicago Convention, when must Iran recognise a foreign certificate of airworthiness?

  1. Only when the aircraft is operated by an Iranian operator
  2. When the certificate is written in English and Persian
  3. Only when the certificate was issued by an ICAO member with a bilateral treaty
  4. When the issuing State's requirements equal or exceed ICAO minimum standards Correct answer.

Explanation

Article 33 requires recognition of certificates of airworthiness and licences issued by other Contracting States when their issuance requirements equal or exceed the minimum standards under the Convention. A State may refuse recognition where the requirements fall below those standards.

Question 11Air Law

An aircraft on the Iranian civil register displays the nationality mark "EP-". Under ICAO Annex 7, what does this mark identify?

  1. The aircraft manufacturer and model
  2. The operator's air transport licence number
  3. The airworthiness certificate category
  4. Iran, the State of Registry Correct answer.

Explanation

Annex 7 requires each aircraft to carry a nationality mark showing the State of Registry and a registration mark unique within that State. Iran's nationality mark is EP, so "EP-" identifies an aircraft on the Iranian register.

Question 12Air Law

During a flight in Iranian airspace, an ATC clearance conflicts with a rule of the air. Who is responsible for ensuring the aircraft complies with the Rules of the Air?

  1. The pilot-in-command Correct answer.
  2. The operator's chief pilot
  3. The air traffic controller who issued the clearance
  4. The CAO of the State of Registry

Explanation

Annex 2 places responsibility for compliance with the Rules of the Air on the pilot-in-command. An ATC clearance does not relieve the PIC of that responsibility, and the PIC must advise ATC if a clearance cannot be accepted safely.

Question 13Air Law

Which ICAO Annex contains the international Standards and Recommended Practices for the Operation of Aircraft?

  1. Annex 8
  2. Annex 6 Correct answer.
  3. Annex 2
  4. Annex 11

Explanation

Annex 6 contains Standards and Recommended Practices for the operation of aircraft, including Part I on international commercial air transport by aeroplanes. It addresses matters such as crew, flight operations and the operator's maintenance responsibilities.

Question 14Air Law

Under Article 6 of the Chicago Convention, what is required before an Iranian airline may operate a scheduled international air service into another contracting State?

  1. That State's special permission or authorization Correct answer.
  2. A flight plan filed with ICAO
  3. Registration of the aircraft in that State
  4. A CPL held by every passenger

Explanation

Article 6 of the Chicago Convention provides that no scheduled international air service may be operated over or into the territory of a contracting State except with the special permission or other authorization of that State. Bilateral air services agreements normally supply that authorization.

Question 15Air Law

Following an accident to an Iranian-registered aircraft in a foreign contracting State, which State must the State of Occurrence notify without delay under Annex 13?

  1. The nearest ICAO regional office
  2. Only the State of Manufacture
  3. The operator's financing State
  4. The State of Registry Correct answer.

Explanation

Annex 13 requires the State of Occurrence to send an accident notification without delay to the State of Registry, State of Operator, State of Design, State of Manufacture and ICAO, among others. The State of Registry is therefore the correct addressee among the options.

Question 16Air Law

Under Annex 2, except when taking off or landing, an aircraft flying over a congested area of a city must maintain a height of at least how much above the highest obstacle within 600 m of the aircraft?

  1. 300 m (1 000 ft) Correct answer.
  2. 900 m (3 000 ft)
  3. 150 m (500 ft)
  4. 600 m (2 000 ft)

Explanation

Annex 2 requires that, except when necessary for take-off or landing, an aircraft over a congested area must fly at least 300 m (1 000 ft) above the highest obstacle within 600 m of the aircraft. This protects persons and property on the ground.

Question 17Air Law

Which of the following is a privilege of the holder of an ICAO-compliant CPL(A) issued by Iran's CAO?

  1. Acting as co-pilot in commercial air transport Correct answer.
  2. Approving instrument approach procedures
  3. Issuing certificates of airworthiness
  4. Commanding a commercial air transport flight without an ATPL

Explanation

Under Annex 1, a CPL(A) holder may exercise PPL privileges, act as pilot-in-command in non-commercial operations and act as co-pilot in commercial air transport. Command of commercial air transport requires the appropriate ATPL.

Question 18Air Law

Under Annex 2, when a controlled flight under IFR loses two-way radio communication and is flying in visual meteorological conditions, what should the pilot normally do?

  1. Return to the departure aerodrome regardless of weather
  2. Continue in VMC to the nearest suitable aerodrome Correct answer.
  3. Climb to the highest available level and hold
  4. Descend below 300 m and follow a road

Explanation

Annex 2 communication-failure procedures require a controlled IFR flight in VMC to continue in VMC, land at the nearest suitable aerodrome and report its arrival to the appropriate ATS unit. It should not climb and hold or descend below safe heights.

Question 19Air Law

Under the ICAO Annex 2 table of cruising levels, an IFR flight above 8 900 m (29 000 ft) on a magnetic track between 000° and 179° should normally be flown at which level?

  1. FL 290, 310, 330 and so on Correct answer.
  2. Any level above FL 290
  3. FL 300, 320, 340 and so on
  4. FL 280, 300, 320 and so on

Explanation

The Annex 2 cruising-level table assigns odd flight levels such as FL 290, 310 and 330 to IFR flights above 8 900 m on magnetic tracks 000° to 179°. Tracks 180° to 359° use even levels such as FL 300 and 320.

Question 20Air Law

Under Article 30 of the Chicago Convention, which authority may license the radio transmitting apparatus carried on board an aircraft engaged in international navigation?

  1. The State overflown
  2. The operator's headquarters State
  3. The State of Registry Correct answer.
  4. The ITU directly

Explanation

Article 30 of the Chicago Convention permits radio transmitting apparatus to be carried only if licensed by the appropriate authorities of the State in which the aircraft is registered. The State of Registry is therefore the licensing authority for the apparatus.

Question 21Air Law

Under Article 9 of the Chicago Convention, a contracting State may restrict or prohibit flights by other States' aircraft over specified areas of its territory for which reasons?

  1. Commercial protection of its national airline
  2. Military necessity or public safety Correct answer.
  3. Collection of customs duties on transit flights
  4. Seasonal noise abatement near residential areas

Explanation

Article 9 permits a contracting State to restrict or prohibit flights over certain areas for reasons of military necessity or public safety. Such restrictions must be applied uniformly to the foreign aircraft concerned and cannot be used simply to protect commercial interests or raise revenue.

Question 22Air Law

Under ICAO Annex 2, under what condition may a flight be conducted in formation?

  1. Only when all aircraft remain in VMC and maintain 1 000 ft vertical separation
  2. Only when the formation leader has a serviceable weather radar
  3. Only when each aircraft has filed a separate IFR flight plan
  4. By pre-arrangement of the pilots-in-command and ATS conditions in controlled airspace Correct answer.

Explanation

Annex 2 prohibits formation flight unless it is pre-arranged among the pilots-in-command of the aircraft taking part. In controlled airspace, the formation must also comply with conditions prescribed by the appropriate ATS authority, which may treat the formation as a single aircraft for navigation and position reporting.

Question 23Air Law

Under Annex 2, before starting which of the following must a flight plan be submitted?

  1. Any flight at night, whatever the airspace class
  2. Only an IFR flight in Class A airspace
  3. Any VFR flight in Class G airspace
  4. Any controlled flight or flight across international borders Correct answer.

Explanation

Annex 2 requires a flight plan to be submitted before any controlled flight and before any flight across international borders. Other flights may also require a flight plan when the appropriate ATS authority or the State concerned so prescribes.

Question 24Air Law

Under Article 5 of the Chicago Convention, what does a contracting State agree regarding aircraft of other contracting States engaged in non-scheduled international flights?

  1. Conclude a bilateral air services agreement before any non-scheduled operation is begun
  2. Obtain prior permission for every individual flight, with no exception even for a pure transit
  3. Make stops for traffic purposes in the territory without any conditions
  4. Fly into or transit the territory and make non-traffic stops without prior permission Correct answer.

Explanation

Article 5 gives aircraft of other contracting States engaged in non-scheduled international flights the right to fly into or transit a State's territory and to make stops for non-traffic purposes without prior permission. The State flown over retains the right to require landing and may prescribe routes or require special permission where safety of flight so demands.

Question 25Aircraft General Knowledge – Airframe, Systems and Powerplant

On an aircraft fitted with an oleo-pneumatic landing gear, which component absorbs the landing impact and dissipates the energy?

  1. The drag brace
  2. The oleo strut Correct answer.
  3. The torque link
  4. The brake pack

Explanation

The oleo strut combines compressed gas with hydraulic fluid metered through an orifice, so it cushions the landing impact and dissipates energy. Torque links and drag braces transmit structural loads but do not provide the main shock absorption.

Question 26Aircraft General Knowledge – Airframe, Systems and Powerplant

In a cantilever wing, which structural member is designed primarily to carry bending loads?

  1. The wing rib
  2. The leading-edge skin
  3. The stringer
  4. The wing spar Correct answer.

Explanation

The spar acts as the main beam of the wing and carries the bending moments generated by lift. Ribs maintain aerofoil shape, stringers stiffen the skin, and the skin carries shear and torsion.

Question 27Aircraft General Knowledge – Airframe, Systems and Powerplant

What is the primary purpose of a hydraulic accumulator in an aircraft hydraulic system?

  1. Store fluid under pressure Correct answer.
  2. Cool fluid before the reservoir
  3. Filter return-line fluid
  4. Select the relief valve

Explanation

An accumulator stores hydraulic fluid under gas pressure, which damps pressure surges and supplies additional flow during peak demand. It does not perform filtration, cooling, or relief-valve selection.

Question 28Aircraft General Knowledge – Airframe, Systems and Powerplant

Why must an aircraft fuel tank be vented to the atmosphere?

  1. To increase fuel pump pressure
  2. To stop refuelling overflow
  3. To maintain near-ambient tank pressure Correct answer.
  4. To let water drain to the sump

Explanation

Venting keeps the ullage at approximately ambient pressure as fuel is burned or as altitude changes, preventing a vacuum or overpressure that could stop fuel flow or damage the tank. Water draining and refuelling overflow are handled by separate sumps and overflow systems.

Question 29Aircraft General Knowledge – Airframe, Systems and Powerplant

In a normal 28 V DC aircraft electrical system, what is the main role of the battery while the engine-driven generator is online?

  1. Damp transients; supply emergency power Correct answer.
  2. Control the generator field current
  3. Generate AC for the avionics bus
  4. Supply all normal DC loads continuously

Explanation

The generator carries the normal DC load and also charges the battery; the battery stabilises bus voltage and supplies essential or emergency loads if generator power is lost. It is not the normal source for all DC loads and does not generate AC or regulate the field.

Question 30Aircraft General Knowledge – Airframe, Systems and Powerplant

What is the function of the cabin outflow valve in a pressurised aircraft?

  1. Provide emergency oxygen
  2. Supply conditioned air to the cabin
  3. Meter cabin outflow Correct answer.
  4. Limit differential pressure only

Explanation

The outflow valve is the controlled opening through which cabin air leaves the pressure hull; modulating it sets the cabin pressure schedule. The air-conditioning packs supply inflow, while relief valves and oxygen systems have separate functions.

Question 31Aircraft General Knowledge – Airframe, Systems and Powerplant

What is the purpose of feathering a propeller after an engine failure?

  1. Lock the blades in fine pitch for starting
  2. Maximise takeoff thrust
  3. Minimise drag from the windmilling propeller Correct answer.
  4. Prevent propeller overspeed

Explanation

Feathering turns the blades to a high angle so the relative airflow meets the leading edge with minimum rotation and drag, reducing asymmetric yaw after engine failure. Fine pitch is used for starting and takeoff, not for feathering.

Question 32Aircraft General Knowledge – Airframe, Systems and Powerplant

In a continuous-loop engine fire detection system, what does a break in the sensing element normally cause?

  1. Automatic discharge of the fire bottle
  2. A false fire warning only in flight
  3. A fault indication or open-loop warning Correct answer.
  4. No warning because the loop is redundant

Explanation

A continuous-loop detector monitors element continuity; a break creates an open circuit that the control unit interprets as a loop fault, often displayed as an open-loop or fault warning. Fire bottles are discharged by crew action, not automatically by a break.

Question 33Aircraft General Knowledge – Airframe, Systems and Powerplant

A hydraulic fuse is installed in the line supplying a wing flap actuator. Which condition is designed to make the fuse close?

  1. High return-line temperature
  2. A blocked return filter
  3. Low reservoir fluid level
  4. Excess flow after rupture Correct answer.

Explanation

A hydraulic fuse closes when flow through it exceeds a set value for a short time, isolating a ruptured downstream line and preserving system pressure and fluid. It does not respond directly to reservoir level, temperature, or return-filter blockage.

Question 34Aircraft General Knowledge – Airframe, Systems and Powerplant

An engine continues to run when the ignition switch is selected to OFF. Which fault is the most likely cause?

  1. Open magneto P-lead Correct answer.
  2. Shorted P-lead to ground
  3. Excessively lean mixture
  4. Worn spark plug electrode

Explanation

The magneto P-lead grounds the primary circuit when the switch is OFF; if the P-lead is open, the magneto remains hot and the engine can keep running. A shorted P-lead would ground the magneto continuously and prevent normal operation.

Question 35Aircraft General Knowledge – Airframe, Systems and Powerplant

In a semi-monocoque aircraft fuselage, what is the primary function of the frames?

  1. They hold the fuselage shape and support the skin. Correct answer.
  2. They form the outer aerodynamic surface and carry all shear loads.
  3. They carry the main bending loads along the length of the fuselage.
  4. They provide the wing attachment points and the engine mount fittings.

Explanation

Frames are transverse members that maintain the fuselage cross-section and stabilise the skin against buckling. Longitudinal members such as longerons carry the main bending loads, so frames do not serve that primary role.

Question 36Aircraft General Knowledge – Airframe, Systems and Powerplant

What is the purpose of a shimmy damper fitted to a nose landing gear?

  1. To absorb vertical landing loads before the oleo strut operates.
  2. To damp rapid nose-wheel oscillations about the steering axis. Correct answer.
  3. To lock the nose wheel in the centred position during retraction.
  4. To apply the wheel brake automatically when the gear is extended.

Explanation

A shimmy damper introduces hydraulic or friction damping to suppress rapid nose-wheel oscillations about the steering axis. It does not carry vertical loads or lock the gear; those tasks belong to the oleo strut and centring or lock mechanisms.

Question 37Aircraft General Knowledge – Airframe, Systems and Powerplant

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

  1. It directs fluid to the emergency system whenever normal pump pressure fails.
  2. It maintains a constant system pressure by continuously varying pump output.
  3. It prevents the accumulator from discharging during normal operation.
  4. It returns excess fluid to the reservoir above a set pressure. Correct answer.

Explanation

A pressure relief valve is a safety device that opens at a preset pressure and returns excess fluid to the reservoir. It protects the system from overpressure but does not regulate normal pump output or control accumulator discharge.

Question 38Aircraft General Knowledge – Airframe, Systems and Powerplant

In a 28 V DC aircraft electrical system, what is the purpose of the voltage regulator associated with the engine-driven generator?

  1. It controls the speed of the generator drive to keep frequency constant.
  2. It limits field current to keep bus voltage within its design range. Correct answer.
  3. It converts alternating current from the generator into direct current for the battery bus.
  4. It disconnects the battery from the bus during engine start.

Explanation

The voltage regulator senses bus voltage and adjusts generator field current so the output stays within the design range. This protects the battery and electrical equipment from over-voltage while allowing the generator to carry the bus load.

Question 39Aircraft General Knowledge – Airframe, Systems and Powerplant

What is the main purpose of a precooler in a gas-turbine bleed-air system?

  1. To reduce bleed-air temperature before it reaches the air-conditioning pack. Correct answer.
  2. To filter oil contamination from the bleed air.
  3. To remove water vapour from the bleed air before it enters the cabin.
  4. To increase bleed-air pressure for cabin pressurisation.

Explanation

Engine bleed air leaves the compressor at high temperature, so a precooler uses cooling air to reduce its temperature before it enters the air-conditioning pack. This protects pack components and allows the air to be conditioned to a suitable cabin temperature.

Question 40Aircraft General Knowledge – Airframe, Systems and Powerplant

What is the function of the propeller governor in a constant-speed propeller system?

  1. It synchronises propeller RPM with the engine ignition timing.
  2. It feathers the propeller automatically whenever the RPM falls below idle.
  3. It changes the propeller blade angle directly with engine manifold pressure.
  4. It meters oil to the propeller to hold the selected RPM. Correct answer.

Explanation

The propeller governor senses RPM and meters engine oil to or from the propeller hub, changing blade angle to hold the RPM selected by the pilot. It works through flyweights and a pilot valve, not by direct manifold-pressure control.

Question 41Aircraft General Knowledge – Airframe, Systems and Powerplant

In a turbocharged reciprocating engine, what is the function of the wastegate?

  1. It bypasses intake air around the compressor to prevent an overboost condition.
  2. It regulates fuel flow to match compressor output.
  3. It controls oil flow to the turbocharger bearings.
  4. It routes exhaust gas around the turbine to control boost. Correct answer.

Explanation

The wastegate valve modulates how much exhaust gas reaches the turbine. Opening it bypasses gas around the turbine, slowing the compressor and limiting boost; closing it increases turbine drive and boost.

Question 42Aircraft General Knowledge – Airframe, Systems and Powerplant

Why is the hydraulic reservoir in many aircraft pressurised with air or nitrogen?

  1. To allow the accumulator to be charged with hydraulic fluid.
  2. To prevent pump cavitation and keep a positive supply at the pump inlet. Correct answer.
  3. To cool the hydraulic fluid by increasing its contact with air in the reservoir.
  4. To increase the maximum pressure available at the actuators.

Explanation

Pressurising the reservoir maintains a positive feed pressure at the pump inlet, which helps prevent cavitation and keeps fluid flowing under all attitudes and flow demands. The pressure is low and is not intended to raise actuator pressure or charge the accumulator.

Question 43Aircraft General Knowledge – Airframe, Systems and Powerplant

How does a balance tab reduce the control force required from the pilot?

  1. It moves opposite the surface and creates a moment assisting deflection. Correct answer.
  2. It moves with the control surface and increases the effective surface deflection.
  3. It adds weight ahead of the hinge line to move the centre of gravity forward.
  4. It locks the control surface in neutral when the pilot releases the controls.

Explanation

A balance tab is linked so that it deflects opposite to the control surface. This creates an aerodynamic moment that helps move the surface, reducing the stick force the pilot must apply.

Question 44Aircraft General Knowledge – Airframe, Systems and Powerplant

In a gas-turbine engine, what is the purpose of the compressor bleed valves that open at low engine speed?

  1. To supply cabin bleed air only when the engine is running at idle.
  2. To prevent compressor surge by relieving pressure in the rear stages. Correct answer.
  3. To cool the turbine blades during engine start.
  4. To increase mass flow through the turbine during acceleration.

Explanation

At low engine speed the rear compressor stages cannot accept the airflow delivered by the front stages, so bleed valves open to release air and reduce the pressure rise. This prevents compressor stall or surge during starting and acceleration.

Question 45Aircraft General Knowledge – Airframe, Systems and Powerplant

On an aircraft landing gear, what is the purpose of the torque links (scissor links) fitted to the shock strut?

  1. Absorb the vertical landing loads and dissipate the energy as heat.
  2. Keep the wheel aligned with the gear leg and transmit braking torque to it. Correct answer.
  3. Provide lateral stability during taxi and damp out shimmy oscillations.
  4. Allow the gear leg to fold during retraction and lock it down when extended.

Explanation

Torque links connect the upper and lower halves of a shock strut. They allow the strut to telescope vertically while preventing relative rotation, so the wheel stays aligned with the gear leg and brake reaction torque is carried into the structure. Vertical load absorption is the job of the oleo-pneumatic strut itself, and shimmy damping is provided by a separate damper.

Question 46Aircraft General Knowledge – Airframe, Systems and Powerplant

In an aircraft air-cycle air conditioning system, what is the function of the water separator?

  1. Remove condensed water from the conditioned air before it enters the cabin. Correct answer.
  2. Remove oil contamination from the engine bleed air supply.
  3. Cool the bleed air before it passes through the primary heat exchanger.
  4. Add moisture to the cabin air to maintain a comfortable relative humidity.

Explanation

In a typical air-cycle machine the water separator is located downstream of the cooling turbine, where the air is at its coldest. It removes entrained water droplets so that the cabin distribution system does not fog up or form ice. The separator does not humidify the cabin air, cool the bleed air, or act as an oil filter.

Question 47Aircraft General Knowledge – Airframe, Systems and Powerplant

In a split-bus DC electrical system, what is the purpose of the bus tie contactor?

  1. It joins the two main buses when required and isolates them after a generator failure. Correct answer.
  2. It disconnects the battery from the essential bus during engine starting.
  3. It limits the maximum current that each generator can supply to its bus.
  4. It converts 28 V DC into 115 V AC for the instrument and avionics buses.

Explanation

A split-bus system normally keeps the left and right main buses separate so that a fault on one side does not affect the other. The bus tie contactor closes to let one generator supply both buses when needed and opens automatically to isolate a failed generator or a short circuit. Current limiting is performed by current limiters or circuit breakers, and AC conversion is performed by inverters or transformers.

Question 48Aircraft General Knowledge – Airframe, Systems and Powerplant

Which condition is most likely to cause a gas-turbine engine compressor to surge?

  1. A rapid throttle increase at low engine speed. Correct answer.
  2. Operation at high altitude with the compressor bleed valves fully open.
  3. A partially blocked fuel nozzle that makes the fuel-air mixture leaner than scheduled.
  4. A gradual increase in bleed-air demand while engine speed remains constant at cruise power.

Explanation

Surge occurs when the compressor cannot maintain delivery pressure against the downstream system, so flow reverses momentarily. Snapping the throttle open at low RPM accelerates the fuel schedule faster than the compressor can accept, pushing the operating point past the stall line. Steady bleed demand, open bleed valves, and a lean mixture do not by themselves move the compressor into surge.

Question 49Aircraft General Knowledge – Instrumentation

In a light aircraft, the airspeed indicator is connected to which pressure sources?

  1. Pitot pressure only
  2. Total pressure and cabin pressure
  3. Pitot and static pressure Correct answer.
  4. Static pressure only

Explanation

The airspeed indicator computes dynamic pressure as pitot (total) pressure minus static pressure, so it must be connected to both the pitot tube and the static source. A single-source connection would not produce the pressure difference that represents airspeed.

Question 50Aircraft General Knowledge – Instrumentation

With the altimeter subscale set to the aerodrome QNH, an aircraft parked on the ramp will indicate which quantity?

  1. pressure altitude
  2. height above the aerodrome reference point
  3. flight level
  4. altitude above mean sea level Correct answer.

Explanation

QNH is the mean sea level pressure at the aerodrome, so when it is set the altimeter reads altitude above mean sea level. QFE would give height above the aerodrome, while 1013.25 hPa gives pressure altitude and flight levels.