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Iran CAO PPL Theory study materials
Iran CAO PPL Theory study resources

Iran CAO PPL Theory practice questions

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Question 1Air Law and ATC Procedures

Under ICAO Annex 1, what is the minimum age for the issue of a private pilot licence (aeroplane)?

  1. 17 years Correct answer.
  2. 16 years
  3. 21 years
  4. 18 years

Explanation

ICAO Annex 1 sets 17 years as the minimum age for a PPL applicant, while the CPL requires 18 years and the ATPL requires 21 years. The 16-year threshold applies to the student pilot licence and to the glider or balloon categories.

Question 2Air Law and ATC Procedures

For a PPL(A) holder acting as pilot-in-command of an aeroplane carrying passengers, ICAO Annex 1 requires the licence holder to have made within the preceding 90 days at least three take-offs and three landings. What is the additional condition on those take-offs and landings?

  1. They must be performed at night
  2. They must be performed on the same type or class of aeroplane Correct answer.
  3. They must be performed at a controlled aerodrome
  4. They must be performed with an instructor on board

Explanation

The recent-experience rule in Annex 1 requires the three take-offs and landings to be completed on the same type or class of aeroplane as the one to be flown, which ensures currency on the relevant aircraft. Currency on a different class does not satisfy the requirement.

Question 3Air Law and ATC Procedures

What is the validity period of a Class 2 medical certificate for a private pilot licence holder under 40 years of age, as specified in ICAO Annex 1?

  1. 24 months Correct answer.
  2. 36 months
  3. 12 months
  4. 60 months

Explanation

Annex 1 specifies a validity of 24 months for a Class 2 medical certificate where the holder is under 40 years of age. Once the holder reaches 40, the validity is reduced to 12 months.

Question 4Air Law and ATC Procedures

A private pilot's Class 2 medical certificate expires while the pilot is abroad and cannot be renewed before returning. Which statement best describes the pilot's position under ICAO rules?

  1. The privileges of the licence may not be exercised until a valid medical certificate is held Correct answer.
  2. The pilot may fly for up to 90 days provided the flight is within Iran
  3. The licence automatically remains valid for 30 days after expiry
  4. The pilot may continue to fly as pilot-in-command but only with a safety pilot

Explanation

A valid medical certificate is a condition for exercising licence privileges, so once it expires the pilot cannot act as pilot-in-command or as a required crew member. There is no automatic grace period built into the licence itself.

Question 5Air Law and ATC Procedures

Which document is required to be carried on board an aircraft engaged in international navigation under ICAO Annex 6?

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

Explanation

Annex 6 lists the documents to be carried on board, and the certificate of registration is among them, together with the certificate of airworthiness, the crew licences, the journey log and the operations manual where applicable. The maintenance programme and personal logbook are not carriage documents.

Question 6Air Law and ATC Procedures

An aircraft bears the nationality mark EP and the registration mark ABC. How must these marks appear on the fuselage of a fixed-wing aeroplane?

  1. EP-ABC in one continuous group on the fuselage, with the letters and hyphen of equal height Correct answer.
  2. EP on the fuselage and ABC on the fin as separate groups
  3. EP-ABC in one continuous group on the lower wing surface
  4. EP-ABC repeated on both sides of the tail fin only

Explanation

Annex 7 requires the nationality and registration marks to be painted on the fuselage as one continuous group, with letters and hyphen of the same height. For fixed-wing aircraft the marks must also appear on the lower surface of the wings.

Question 7Air Law and ATC Procedures

What is the general rule for the minimum height above the highest obstacle over congested areas of cities for a VFR flight, unless otherwise authorised by the State?

  1. 500 ft above the highest obstacle within a radius of 600 m
  2. 2 000 ft above the highest obstacle within a radius of 600 m
  3. 1 000 ft above the highest obstacle within a radius of 600 m Correct answer.
  4. 1 000 ft above the highest obstacle within a radius of 8 km

Explanation

ICAO Annex 2 requires flight over congested areas of cities to be at least 1 000 ft above the highest obstacle within a radius of 600 m from the aircraft. Elsewhere the rule is 500 ft above the surface and clear of persons and property.

Question 8Air Law and ATC Procedures

Except when necessary for take-off or landing, at what minimum height must a VFR flight be conducted over an area that is not congested?

  1. 1 000 ft above the surface, clear of persons and property
  2. 1 500 ft above the highest obstacle within 8 km
  3. 500 ft above the surface, clear of persons and property Correct answer.
  4. 300 ft above the surface, clear of persons and property

Explanation

Annex 2 sets 500 ft above the surface as the minimum for VFR flight outside congested areas, provided the aircraft remains clear of persons and property on the ground. The higher 1 000 ft rule applies only over congested areas.

Question 9Air Law and ATC Procedures

In which class of airspace is VFR flight permitted with a clearance, while IFR and VFR flights are separated from each other and from all other traffic?

  1. Class F
  2. Class C Correct answer.
  3. Class A
  4. Class D

Explanation

In Class C airspace both IFR and VFR flights are permitted, and both receive separation from all other traffic. Class A admits only IFR flights, and Class D provides separation only between IFR flights.

Question 10Air Law and ATC Procedures

Which class of airspace permits both IFR and VFR flights and provides separation to IFR flights from other IFR flights, while VFR flights receive traffic information about other VFR flights?

  1. Class E
  2. Class B
  3. Class G
  4. Class D Correct answer.

Explanation

Class D provides separation between IFR flights and traffic information to VFR flights about other traffic. Class E separates IFR from IFR but does not provide traffic information to VFR flights in the same way.

Question 11Air Law and ATC Procedures

What is the standard cruising level for magnetic tracks from 000 to 179 degrees in the 3 000 ft to 8 000 ft band under the ICAO semicircular rule?

  1. Even thousands plus 500 ft
  2. Odd thousands plus 500 ft Correct answer.
  3. Odd thousands exactly
  4. Even thousands exactly

Explanation

For magnetic tracks 000 to 179 degrees, the semicircular rule assigns odd thousands plus 500 ft in the lower band, and odd thousands without the 500 ft suffix from FL 290 upwards. The reciprocal tracks use even thousands.

Question 12Air Law and ATC Procedures

What does a flashing red light signal directed at an aircraft on the ground mean?

  1. Cleared for take-off
  2. Taxi clear of the landing area in use Correct answer.
  3. Stop
  4. Return to starting point on the aerodrome

Explanation

A flashing red light to an aircraft on the ground means taxi clear of the landing area in use. A steady red light means stop, and a flashing white light means return to the starting point.

Question 13Air Law and ATC Procedures

An aircraft in flight receives a steady red light signal from the aerodrome control tower. What is the correct action?

  1. Return to the aerodrome for landing
  2. Give way to other aircraft and continue circling Correct answer.
  3. Continue flying and give way to other aircraft
  4. Land at the nearest suitable aerodrome

Explanation

For an aircraft in flight, a steady red light means give way to other aircraft and continue circling. It is distinct from the flashing red signal, which requires landing at the nearest suitable aerodrome.

Question 14Air Law and ATC Procedures

Two aeroplanes are approaching head-on and there is risk of collision. Which action is required by the rules of the air?

  1. The lower aircraft gives way
  2. The faster aircraft gives way
  3. Both alter heading to the left
  4. Both alter heading to the right Correct answer.

Explanation

When two aircraft are approaching head-on or nearly so, each shall alter its heading to the right. This produces a predictable pass with the other aircraft on the left.

Question 15Air Law and ATC Procedures

An aeroplane and a glider are converging at approximately the same level, and the aeroplane has the glider on its right. Which aircraft has the right of way?

  1. The faster aircraft
  2. The glider, because gliders have priority over powered aircraft Correct answer.
  3. The aircraft on the right, in all cases
  4. The aeroplane, because it is power-driven

Explanation

The right-of-way rules give priority to less manoeuvrable categories: balloons over all others, gliders over powered aircraft, and airships over aeroplanes and helicopters. The glider therefore has the right of way even when it is on the aeroplane's right.

Question 16Air Law and ATC Procedures

What is the meaning of a white cross displayed in the signal square of an aerodrome?

  1. Runway surface unfit for use
  2. Glider flying in progress Correct answer.
  3. Aerodrome closed to all traffic
  4. Special precautions for landing required

Explanation

A white cross in the signal square indicates that glider flying is in progress and that special care is needed on the aerodrome. A horizontal red square with a yellow diagonal, by contrast, warns of special precautions for landing.

Question 17Air Law and ATC Procedures

A pilot observes a red and white vertical striped bar displayed in the signal square. What does it indicate?

  1. Right-hand traffic pattern in use Correct answer.
  2. Aerodrome accepts only IFR traffic
  3. Landing prohibited
  4. Left-hand traffic pattern in use

Explanation

A red and white striped bar in the signal square indicates that a right-hand circuit is in force. The absence of the bar means the standard left-hand pattern applies.

Question 18Air Law and ATC Procedures

Which condition must be met for a pilot to operate under special VFR within a control zone?

  1. The pilot must hold an instrument rating
  2. The flight must be conducted above the transition level
  3. The flight must remain clear of cloud and in sight of the surface, with a clearance from ATC Correct answer.
  4. The aircraft must be equipped with a serviceable autopilot

Explanation

Special VFR permits flight within a control zone when the weather is below normal VFR minima, provided the aircraft remains clear of cloud and in sight of the surface and an ATC clearance has been obtained. Ground visibility must also meet the State's specified minimum.

Question 19Air Law and ATC Procedures

For IFR flight in controlled airspace, what does the term 'transition level' mean?

  1. The level at which the vertical separation minimum changes from 1 000 ft to 2 000 ft
  2. The lowest flight level available for use above the transition altitude Correct answer.
  3. The altitude at which the altimeter is set to QNH
  4. The altitude below which IFR flight is not permitted

Explanation

The transition level is the lowest flight level available for use above the transition altitude, and it varies with the atmospheric pressure. Below it the altimeter is set to QNH, and at or above it the standard pressure setting is used.

Question 20Air Law and ATC Procedures

When must a pilot change the altimeter setting from QNH to the standard pressure setting of 1013.2 hPa?

  1. When cleared to enter Class D airspace
  2. When passing the transition altitude in the climb Correct answer.
  3. When the aircraft reaches FL 100
  4. When passing the transition level in the climb

Explanation

In the climb the altimeter is changed to the standard pressure setting when passing the transition altitude, and in the descent it is changed back to QNH when passing the transition level. The two references are deliberately different to keep a buffer between them.

Question 21Air Law and ATC Procedures

How is a position report expressed in degrees and minutes of latitude and longitude when the minutes are less than 10?

  1. The minutes are preceded by a zero Correct answer.
  2. The minutes are omitted
  3. The minutes are rounded to the nearest ten
  4. The minutes are given with a decimal point

Explanation

ICAO position-reporting conventions require each degree and minute group to be expressed with two or three digits as appropriate, so minutes below ten are preceded by a zero. This removes ambiguity in radio communication.

Question 22Air Law and ATC Procedures

Which phrase is used by a pilot to indicate that a transmission has been received in full and understood?

  1. WILCO
  2. STANDBY
  3. ROGER Correct answer.
  4. AFFIRM

Explanation

ROGER means that the transmission has been received in full. WILCO adds a commitment to comply, AFFIRM answers a question in the affirmative, and STANDBY indicates that the controller will call back.

Question 23Air Law and ATC Procedures

A pilot reads back a clearance and the controller replies 'READ BACK CORRECT'. What does this indicate?

  1. The pilot must contact the next frequency
  2. The read-back was incorrect and a new clearance follows
  3. The read-back was correct and the clearance is confirmed Correct answer.
  4. The clearance is cancelled

Explanation

The phrase READ BACK CORRECT confirms that the pilot's read-back matched the clearance as issued. If the read-back were wrong, the controller would say NEGATIVE followed by the correct version.

Question 24Air Law and ATC Procedures

An aircraft is intercepted by a military aircraft and receives the instruction to follow. Which action should the pilot take first?

  1. Attempt to establish radio communication with the intercepting aircraft on the emergency frequency Correct answer.
  2. Immediately descend to the lowest safe altitude
  3. Turn away from the intercepting aircraft and increase speed
  4. Squawk 7700 and shut down the transponder

Explanation

Annex 2 and the PANS-ATM interception procedures require the intercepted aircraft to attempt radio contact with the intercepting aircraft or the appropriate ATC unit, using the emergency frequency if necessary, and to follow the visual signals. The pilot should also select the appropriate transponder code.

Question 25Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

In a normally aspirated piston engine, what is the primary purpose of the carburettor venturi?

  1. To create a low-pressure region that draws fuel from the main jet Correct answer.
  2. To cool the incoming air before it enters the cylinders
  3. To increase the compression ratio at high power settings
  4. To regulate the oil pressure supplied to the bearings

Explanation

The venturi narrows the induction passage, so air accelerates and its static pressure falls. This pressure drop across the main jet draws fuel into the airstream, where it atomises and mixes with the air. The other components of the carburettor then meter and control this mixture.

Question 26Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

A piston engine is fitted with a fixed-pitch propeller. Which statement describes the effect of selecting a lower power setting in level flight?

  1. Engine rpm decreases because the propeller absorbs less power at the lower throttle setting Correct answer.
  2. Engine rpm remains constant because the propeller pitch is automatically adjusted
  3. Engine rpm increases because the reduced manifold pressure allows the propeller to speed up
  4. Engine rpm decreases and the propeller blade angle changes to maintain thrust

Explanation

With a fixed-pitch propeller, blade angle cannot change, so the only way the propeller can absorb less power is by turning more slowly. Closing the throttle reduces power output and rpm settles at a new equilibrium. This is why rpm is used as an indirect indication of power on such aircraft.

Question 27Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

What does the airspeed indicator actually measure, and how is the displayed value derived?

  1. Ground speed, derived from GPS position updates
  2. Dynamic pressure, converted to a speed using standard sea-level density Correct answer.
  3. Static pressure, converted to altitude using the standard atmosphere
  4. True airspeed, derived from outside air temperature

Explanation

The airspeed indicator compares pitot (total) pressure with static pressure; the difference is dynamic pressure. The instrument mechanism converts this pressure difference into a speed assuming standard sea-level air density. Because actual density varies with altitude and temperature, indicated airspeed differs from true airspeed.

Question 28Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

During a walk-around inspection, hydraulic fluid is found weeping from a landing gear actuator seal. What is the most appropriate immediate action?

  1. Report the defect and have it assessed before flight Correct answer.
  2. Continue the flight and monitor fluid quantity in flight
  3. Top up the reservoir and dispatch without further action
  4. Wipe the area clean and treat the leak as serviceable

Explanation

Any fluid leak from a hydraulic actuator indicates a possible seal failure that can worsen rapidly under pressure and lead to loss of the system. The defect must be recorded and assessed against the maintenance manual before the aircraft flies. Cleaning or topping up only hides the symptom.

Question 29Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

Which instrument uses only the static pressure source and will therefore continue to work if the pitot tube becomes blocked?

  1. Vertical speed indicator
  2. Altimeter Correct answer.
  3. Airspeed indicator
  4. Airspeed indicator and vertical speed indicator only

Explanation

The altimeter is connected only to the static source, so a blocked pitot tube does not affect it. The airspeed indicator relies on the difference between pitot and static pressure and would be unreliable. The vertical speed indicator also uses static pressure, but option 1 is the single best answer among the pure static instruments listed.

Question 30Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

What is the function of the magneto in an aircraft piston engine ignition system?

  1. To convert low-tension battery voltage into the high-tension voltage needed at the spark plugs Correct answer.
  2. To advance and retard the ignition timing according to manifold pressure
  3. To earth the spark plugs when the engine is shut down
  4. To supply a continuous spark for the duration of the power stroke

Explanation

A magneto is a self-contained generator that produces high voltage for the spark plugs without relying on the aircraft battery. It uses a rotating magnet and coil to induce the high-tension pulse. This independence is why magnetos are used rather than battery coil ignition.

Question 31Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

Why is engine oil temperature monitored in flight?

  1. To confirm that the oil is thin enough to reduce friction in the accessory gearbox
  2. To check that the oil cooler flap is fully closed during descent
  3. To ensure the oil is warm enough to flow and cool enough to maintain its lubricating properties Correct answer.
  4. To verify that the oil pressure gauge is reading correctly

Explanation

Oil must be warm enough to circulate and reach all bearing surfaces, yet not so hot that it loses viscosity or begins to break down. Monitoring temperature allows the pilot to manage cowl flaps, power and cooling. It is a direct check on the oil system's thermal state.

Question 32Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

In a light aircraft electrical system, what is the purpose of the master switch?

  1. To reset the circuit breakers automatically after an overload
  2. To control the fuel boost pump independently of the battery
  3. To connect or disconnect the battery and alternator from the main bus Correct answer.
  4. To select which magneto is active during run-up

Explanation

The master switch is the main contactor control that ties the battery and the alternator to the electrical bus. It allows the whole electrical system to be energised or isolated with one action. This is why it is used for emergency shutdown of electrical power.

Question 33Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

An aircraft is climbing at a constant indicated airspeed. What happens to true airspeed as altitude increases?

  1. True airspeed remains equal to indicated airspeed
  2. True airspeed decreases in proportion to the decrease in temperature
  3. True airspeed increases because air density decreases Correct answer.
  4. True airspeed decreases because the air is thinner

Explanation

Indicated airspeed reflects dynamic pressure, which depends on density. As altitude rises, density falls, so a given dynamic pressure corresponds to a higher true speed through the thinner air. This is why true airspeed is always higher than indicated airspeed at altitude.

Question 34Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

During a descent with the carburettor heat selected ON, the pilot notices a gradual rise in manifold pressure and smoother running. What is the most likely explanation?

  1. The mixture has become too rich and the engine is flooding
  2. The engine is over-speeding because the propeller is under-loaded
  3. The throttle valve has been opened further by the linkage
  4. Carburettor ice that had formed is melting and the mixture is returning to normal Correct answer.

Explanation

Carburettor heat raises the temperature of the induction air, melting any ice that had accumulated in the venturi or throttle body. As the restriction clears, manifold pressure rises toward the value set by the throttle and the mixture becomes correct again. This improvement after selecting heat is a classic confirmation that ice was present.

Question 35Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

A constant-speed propeller is set to 2400 rpm and the aircraft enters a climb at full throttle. What does the propeller governor do to maintain the selected rpm?

  1. It feathers the blades to reduce drag
  2. It opens the wastegate to limit manifold pressure
  3. It increases blade angle to absorb the extra power Correct answer.
  4. It decreases blade angle to absorb the extra power

Explanation

In a climb at full throttle the engine tends to produce more power, which would increase rpm. The governor senses the overspeed and increases blade angle so the propeller absorbs more power and rpm stays at the set value. Blade angle changes are the governor's only means of controlling rpm.

Question 36Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

Why must the fuel selector be positioned to a tank containing fuel before starting an engine that has been idle?

  1. To keep the electric boost pump from over-pressurising the system
  2. To ensure the engine-driven pump draws fuel rather than air from an empty line Correct answer.
  3. To allow the mixture control to be set to idle cut-off
  4. To prevent air from entering the fuel pump and causing a vapour lock

Explanation

If the selector points to an empty tank or OFF, the engine-driven pump draws air and the engine will not start or will run briefly and stop. Selecting a tank with fuel ensures a liquid supply to the pump and carburettor. This is a standard pre-start check in the cockpit drill.

Question 37Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

What is the purpose of the alternate air source on an aircraft with a mechanically driven supercharger?

  1. To supply cooled air to the cabin
  2. To provide induction air if the normal intake becomes blocked by ice Correct answer.
  3. To increase the mixture strength during climb
  4. To bypass the supercharger at high altitude

Explanation

The normal induction intake can become blocked by ice or foreign matter, starving the engine of air. The alternate air door opens to draw air from inside the cowling, allowing the engine to keep running. It is a safety feature against induction system blockage.

Question 38Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

A pilot observes that the ammeter shows a discharge after starting and remains so in cruise. Which condition is most consistent with this indication?

  1. The voltage regulator is overcharging the battery
  2. The alternator has failed and the battery is supplying the electrical load Correct answer.
  3. The starter motor is still engaged
  4. The battery is fully charged and the alternator is regulating correctly

Explanation

A continuous discharge in cruise means the electrical load exceeds the alternator output and the battery is making up the difference. This typically indicates an alternator or regulator failure. The battery will eventually be depleted, so the flight should be managed accordingly.

Question 39Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

How does a vertical speed indicator produce an immediate indication of climb or descent?

  1. By integrating the airspeed over time
  2. By measuring the rate of change of static pressure through a calibrated leak Correct answer.
  3. By sensing the angle between the aircraft and the airflow
  4. By comparing pitot pressure with static pressure

Explanation

The VSI receives static pressure into a capsule and into a surrounding case connected through a calibrated leak. When altitude changes, the capsule and case pressures differ momentarily, deflecting the needle. The leak allows the case pressure to catch up, so the needle returns to zero in level flight.

Question 40Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

A turbocharged engine is climbing and the pilot observes that manifold pressure is rising toward the maximum continuous limit. What is the correct action?

  1. Lean the mixture to full rich to cool the charge
  2. Reduce throttle or adjust the wastegate to keep manifold pressure within limits Correct answer.
  3. Select carburettor heat to reduce manifold pressure
  4. Increase the throttle setting to maintain climb power

Explanation

A turbocharger can raise manifold pressure beyond the engine's certified limit as altitude increases. The pilot must reduce throttle or modulate the wastegate to keep boost within the placarded limit. Exceeding it risks detonation and structural damage.

Question 41Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

What is the primary reason for preheating engine oil in cold weather before start?

  1. To increase the octane rating of the fuel
  2. To prevent the magnetos from misfiring
  3. To reduce the electrical load on the starter motor
  4. To ensure oil flows to bearings and galleries that would otherwise be starved Correct answer.

Explanation

Cold oil becomes very viscous and may not flow quickly enough to protect bearings during the critical first moments after start. Preheating restores flow and reduces wear. It also makes starting easier, but bearing protection is the primary safety reason.

Question 42Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

An aircraft has a fixed landing gear and a nose-wheel steering system linked to the rudder pedals. During taxi, the pilot finds steering stiff and the nose wheel does not centre. Which system should be inspected first?

  1. The nose-wheel steering and shimmy damper assembly Correct answer.
  2. The fuel quantity indicating system
  3. The magneto timing
  4. The pitot-static system

Explanation

Stiff steering and a nose wheel that fails to centre point directly to the steering linkage or the shimmy damper. These components are subject to wear and are checked during maintenance. The other systems listed have no influence on ground steering.

Question 43Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

What is the effect of a blocked static source on the airspeed indicator during a climb?

  1. The airspeed indication decreases toward zero
  2. The airspeed indication increases toward the maximum Correct answer.
  3. The airspeed indication becomes erratic and oscillates
  4. The airspeed indication remains constant regardless of actual speed

Explanation

With the static source blocked, static pressure inside the instrument stays at the value trapped when the blockage occurred. As the aircraft climbs, true ambient pressure falls, so the difference between pitot and trapped static pressure grows. The airspeed indicator therefore reads increasingly high, even though actual speed is unchanged.

Question 44Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

Why is the mixture leaned during a cruise climb at high altitude in a normally aspirated engine?

  1. To reduce the load on the alternator
  2. To compensate for the decreasing air density and maintain the correct fuel-to-air ratio Correct answer.
  3. To increase the fuel flow for better cooling
  4. To raise the octane rating of the fuel

Explanation

As altitude increases, air density falls while the carburettor meters fuel according to the airflow it senses. Without leaning, the mixture becomes progressively richer than optimum. Leaning restores the correct fuel-to-air ratio for efficient combustion and smooth running.

Question 45Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

A pilot notices that the oil pressure gauge reads zero shortly after take-off while oil temperature remains normal. What is the most likely consequence if the flight continues?

  1. The propeller will automatically feather to protect the engine
  2. The engine will continue to run normally because temperature is normal
  3. The fuel flow will increase to compensate
  4. Engine damage may occur rapidly because lubrication has been lost Correct answer.

Explanation

Oil pressure is the indication that oil is reaching the bearings. A zero reading means lubrication has been lost, and damage can occur within seconds even if temperature still reads normally. The correct response is to reduce power and land as soon as practicable.

Question 46Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

Why does an aircraft piston engine use two independent magnetos rather than one?

  1. To reduce the weight of the ignition harness
  2. To allow the engine to run on either magneto alone and to improve combustion efficiency Correct answer.
  3. To permit the engine to run without a battery
  4. To double the voltage delivered to each spark plug

Explanation

Two magnetos provide redundancy so that a failure of one does not stop the engine. They also fire two spark plugs per cylinder, which shortens the flame path and improves combustion. The run-up check confirms each magneto operates correctly.

Question 47Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

An aircraft is equipped with a constant-speed propeller and a manifold pressure gauge. During descent, the pilot reduces manifold pressure below the rpm setting. What is the risk?

  1. The engine will run too lean and detonate
  2. The turbocharger will overboost the engine
  3. The alternator will drop offline
  4. The propeller may drive the engine, causing an overspeed or engine damage Correct answer.

Explanation

In descent the propeller can absorb energy from the airflow and drive the engine if manifold pressure is set too low relative to rpm. This condition, sometimes called the propeller driving the engine, can cause rpm to rise and stress the engine. The standard technique is to reduce power in the correct order and avoid low manifold pressure with high rpm.

Question 48Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

What does an exhaust gas temperature gauge indicate to the pilot during mixture leaning?

  1. The oil temperature at the exhaust valve
  2. The exact fuel-to-air ratio at all times
  3. The cylinder head temperature only
  4. The peak EGT, which occurs near the stoichiometric mixture and is used as a reference for setting mixture Correct answer.

Explanation

As the mixture is leaned, EGT rises to a peak and then falls as the mixture becomes too lean to burn efficiently. Peak EGT provides a repeatable reference point from which the pilot can set a richer or leaner mixture as recommended. It is a relative indicator, not a direct readout of fuel-to-air ratio.

Question 49Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

An aircraft with a hydraulically operated retractable landing gear has a gear-up warning horn that sounds when the throttle is retarded. What does this indicate?

  1. The warning horn circuit is faulty and should be ignored
  2. The gear selector is in the up position and the system is normal
  3. The landing gear is not down and locked while power is reduced for landing Correct answer.
  4. The hydraulic pump has failed

Explanation

The warning system is designed to alert the pilot when the throttle is retarded for landing but the gear is not down and locked. It is a deliberate safeguard against a gear-up landing. The correct response is to check gear position and extend it if necessary.

Question 50Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)

On an aircraft equipped with a constant-speed propeller, which instrument indication directly reflects the power output of the engine during cruise at a fixed propeller setting?

  1. Fuel flow indicator
  2. Manifold pressure gauge Correct answer.
  3. Exhaust gas temperature gauge
  4. Cylinder head temperature gauge

Explanation

For a given propeller RPM, the power developed by a piston engine is closely related to the pressure in the intake manifold, which is shown by the manifold pressure gauge. Pilots therefore use manifold pressure together with RPM to set and monitor cruise power. The other gauges show mixture or thermal condition rather than the actual power being produced.