I85PREP
⌘ K
BDCA PPL Knowledge Exam study materials
BDCA PPL Knowledge Exam study resources

BDCA PPL Knowledge Exam practice questions

One question at a time. Build your BDCA PPL Knowledge Exam understanding.

First 50 of 200 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

Continue in the practice tool above to load more questions, 50 at a time.

Question 1Air Law and ATC Procedures

Under the ICAO Convention, which document constitutes the certificate of registration for an aircraft?

  1. The certificate of registration issued by the state of registry Correct answer.
  2. The radio station licence issued by the communications authority
  3. The certificate of airworthiness issued after inspection
  4. The aircraft journey log maintained by the operator

Explanation

The Convention on International Civil Aviation requires every aircraft engaged in international navigation to carry a certificate of registration issued by the state in which it is registered. The certificate of airworthiness is a separate document certifying fitness to fly, and the journey log and radio licence serve other purposes.

Question 2Air Law and ATC Procedures

Which body is responsible for establishing binding Standards and Recommended Practices adopted as Annexes to the Chicago Convention?

  1. The ICAO Council acting with the Air Navigation Commission Correct answer.
  2. The national civil aviation authority of the state of manufacture
  3. The United Nations Security Council
  4. The International Air Transport Association

Explanation

Annexes to the Chicago Convention are adopted by the ICAO Council, which is assisted in technical matters by the Air Navigation Commission. IATA is an industry trade association whose resolutions do not bind states, and individual national authorities implement rather than create the Annexes.

Question 3Air Law and ATC Procedures

What is the status of a Standard contained in an ICAO Annex for a contracting state that has not filed a difference?

  1. Binding on the state, which must implement it in national practice Correct answer.
  2. Applicable only to aircraft on international commercial flights
  3. Advisory guidance that the state may apply at its discretion
  4. Enforceable only after separate ratification by the state parliament

Explanation

A Standard is a binding specification whose uniform application is recognised as necessary for the safety of international air navigation. If a contracting state cannot comply, it must notify ICAO of a difference; absent such notification, the Standard is expected to be implemented.

Question 4Air Law and ATC Procedures

An aircraft registered in State A is operated on a flight wholly within State B. Which state exercises primary jurisdiction over the aircraft's airworthiness?

  1. State B, because the flight is entirely within its territory
  2. ICAO, because the flight crosses no national border
  3. State A, because it is the state of registry Correct answer.
  4. The state of the operator, because it controls the flight

Explanation

The state of registry retains responsibility for the airworthiness of the aircraft and for issuing its certificate of airworthiness. The state where the flight occurs may enforce its own operating rules but does not assume airworthiness jurisdiction merely because the flight is domestic to it.

Question 5Air Law and ATC Procedures

Which of the following must a private pilot licence holder carry on board when operating an aircraft internationally?

  1. The licence, medical certificate and aircraft documents Correct answer.
  2. The aircraft maintenance programme and engine logbooks
  3. A medical certificate only, if the licence is not required
  4. A copy of the Chicago Convention and its Annexes

Explanation

Pilots must carry their licence and current medical certificate, and the aircraft must carry its registration, airworthiness and radio documents. Maintenance records such as engine logbooks are kept by the operator but are not normally carried on board.

Question 6Air Law and ATC Procedures

In the absence of any special agreement, which rules govern the operation of an aircraft over the high seas?

  1. The rules published by the operator's home base
  2. The rules of the state of registry, applied over the high seas Correct answer.
  3. The rules of the nearest coastal state
  4. The rules of the state whose flight information region covers the area

Explanation

Over the high seas, aircraft operate under the rules of their state of registry, which has agreed to apply the Annex 2 rules without difference. Coastal states cannot impose their flight rules on the high seas, and flight information regions are service boundaries rather than legal jurisdictions.

Question 7Air Law and ATC Procedures

Which action by the pilot in command is required before an aircraft may be operated when it is not in an airworthy condition?

  1. Obtain a verbal approval from the local air traffic control unit
  2. Record the defect in the technical log and have it cleared Correct answer.
  3. Apply for a temporary change of registration
  4. Notify the nearest ICAO regional office

Explanation

Defects affecting airworthiness must be entered in the technical log and rectified or deferred in accordance with approved procedures before further flight. Air traffic control has no authority over airworthiness, and no ICAO office issues clearances for individual defects.

Question 8Air Law and ATC Procedures

What is the purpose of a Certificate of Airworthiness?

  1. To authorise commercial transport of passengers
  2. To confirm the aircraft meets the applicable airworthiness requirements Correct answer.
  3. To identify the owner of the aircraft for legal purposes
  4. To certify the competence of the flight crew

Explanation

The certificate of airworthiness is issued when the state of registry is satisfied that the aircraft conforms to an approved type design and is in a condition for safe operation. Ownership is recorded on the registration certificate, crew competence on licences, and commercial transport requires a separate operating authorisation.

Question 9Air Law and ATC Procedures

An aircraft is overdue at its destination and a search is initiated. Who is normally responsible for declaring the emergency phase and alerting search and rescue services?

  1. The air traffic services unit with which the flight plan was filed Correct answer.
  2. The state of registry's accident investigation board
  3. The operator's dispatch office, because it holds the flight plan
  4. The destination aerodrome fire service

Explanation

Alerting service is an air traffic services function; the ATS unit responsible for the flight plan declares the alert phases and notifies search and rescue. Operators may assist with information, but the formal alerting responsibility rests with ATS under Annex 11.

Question 10Air Law and ATC Procedures

Which service is provided to alert search and rescue organisations when an aircraft is in a state of emergency?

  1. Aerodrome control service
  2. Advisory service
  3. Flight information service
  4. Alerting service Correct answer.

Explanation

Alerting service notifies appropriate organisations when an aircraft needs search and rescue assistance and assists those organisations as required. Flight information and advisory services provide information, and aerodrome control handles traffic on and around the aerodrome.

Question 11Air Law and ATC Procedures

Which of the following correctly describes a control zone?

  1. Controlled airspace extending upwards from the surface around an aerodrome Correct answer.
  2. Uncontrolled airspace within 5 nautical miles of an aerodrome
  3. Airspace reserved exclusively for military aircraft
  4. Airspace above 5 500 feet only, around a major airport

Explanation

A control zone is controlled airspace that extends upwards from the surface to a specified upper limit around one or more aerodromes. It exists to protect aerodrome traffic and is not defined by a fixed lower level or by military reservation.

Question 12Air Law and ATC Procedures

In controlled airspace, what does a clearance issued by air traffic control authorise?

  1. A transfer of responsibility for terrain clearance to ATC
  2. Permission to proceed under specified conditions Correct answer.
  3. A guarantee that no other traffic will conflict with the flight
  4. An exemption from the rules of the air

Explanation

A clearance is an authorisation to proceed under conditions specified by ATC; it does not relieve the pilot of responsibility for the safe conduct of the flight. Pilots must still avoid traffic and terrain, and clearances never suspend the rules of the air.

Question 13Air Law and ATC Procedures

An aircraft is given the instruction 'hold short of runway 27'. What does this require the pilot to do?

  1. Stop before the runway holding position and await further clearance Correct answer.
  2. Remain on the taxiway until the tower transmits a landing clearance
  3. Continue taxiing and cross the runway without delay
  4. Enter the runway and stop at the centreline

Explanation

A hold short instruction requires the aircraft to stop before the designated runway holding position marking and not enter the protected runway area until further clearance is received. Crossing without an explicit clearance is a serious runway incursion.

Question 14Air Law and ATC Procedures

When a pilot reads back a clearance, what is the primary purpose of the readback?

  1. To give other aircraft time to copy the same clearance
  2. To satisfy a legal requirement to record the pilot's voice
  3. To allow the controller to verify the clearance was correctly understood Correct answer.
  4. To confirm the aircraft's radio equipment is serviceable

Explanation

Readback allows the controller to detect any misunderstanding and correct it before the aircraft acts on the clearance. It is a safety barrier against communication errors, not a voice-recording formality or a radio serviceability check.

Question 15Air Law and ATC Procedures

Which phrase should a pilot use to indicate that a transmission has been received but the requested action cannot be complied with?

  1. Say again
  2. Unable Correct answer.
  3. Wilco
  4. Standby

Explanation

'Unable' communicates that the pilot cannot comply with the request, and the pilot should state the reason if practicable. 'Standby' means wait, 'wilco' means will comply, and 'say again' requests repetition of a transmission.

Question 16Air Law and ATC Procedures

An aircraft on approach loses radio communication in instrument meteorological conditions. Which action is consistent with the standard ICAO communication failure procedure?

  1. Continue according to the last acknowledged clearance and the published communication failure procedure Correct answer.
  2. Circle overhead the last reporting point until radio contact is restored
  3. Land at the nearest available aerodrome regardless of the flight plan
  4. Descend immediately below cloud and proceed visually to the nearest aerodrome

Explanation

On communication failure in IMC, the pilot should follow the last received and acknowledged clearance and then the published communication failure procedure for the route. This normally involves maintaining the assigned level for a specified period before descending in accordance with the procedure.

Question 17Air Law and ATC Procedures

What is the meaning of the transponder code 7700?

  1. Unlawful interference
  2. Radio communication failure
  3. General emergency Correct answer.
  4. Loss of navigation capability

Explanation

Code 7700 is the general emergency code and alerts ATS that the aircraft is in distress or urgency. Code 7600 indicates radio failure and code 7500 indicates unlawful interference; there is no dedicated code for loss of navigation capability.

Question 18Air Law and ATC Procedures

An aircraft is intercepted by a military aircraft. What should the intercepted pilot do first?

  1. Follow the interceptor's instructions and, if possible, establish radio contact Correct answer.
  2. Descend to the lowest safe altitude and accelerate
  3. Squawk 7600 and continue the original route
  4. Immediately change heading away from the interceptor

Explanation

An intercepted aircraft should attempt to establish radio communication and follow the intercepting aircraft's signals and instructions. Maneuvers that surprise the interceptor, such as sudden turns or descents, can be misinterpreted and must be avoided.

Question 19Air Law and ATC Procedures

Which of the following is a recommended practice for avoiding wake turbulence behind a heavy aircraft on approach?

  1. Follow closely so as to remain within the same air mass
  2. Fly slightly below the preceding aircraft's flight path and land before its touchdown point
  3. Remain above the preceding aircraft's flight path and land beyond its touchdown point Correct answer.
  4. Approach at a higher speed to reduce time in the wake

Explanation

Wake vortices sink and drift outward, so a following aircraft should stay at or above the preceding aircraft's path and touch down beyond its touchdown point. Flying below the path places the aircraft directly in the descending vortex cores.

Question 20Air Law and ATC Procedures

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

  1. Return to the starting point
  2. Taxi clear of the runway in use
  3. Stop Correct answer.
  4. Give way to other aircraft and continue taxiing

Explanation

A steady red light directed at an aircraft on the ground means stop. A red flashing light means taxi clear of the runway in use, and a green flashing light permits taxiing.

Question 21Air Law and ATC Procedures

An aircraft on final approach receives a series of red flashes from the aerodrome control tower. What does this signal mean?

  1. Give way and continue circling
  2. Clear to land
  3. Aerodrome unsafe, do not land Correct answer.
  4. Continue approach, expect landing clearance

Explanation

A series of red flashes directed at an aircraft on approach warns that the aerodrome is unsafe and that landing is prohibited. A steady green light means cleared to land, and a steady red light means give way and continue circling.

Question 22Air Law and ATC Procedures

For the purpose of the rules of the air, at what height above the highest obstacle within a horizontal radius of 600 metres is an aircraft normally considered to be over a congested area?

  1. 150 metres
  2. 600 metres
  3. 300 metres Correct answer.
  4. 1 000 metres

Explanation

An aircraft is deemed to be over a congested area of a city, town or settlement when it is flown at a height of 300 metres or more above the highest obstacle within a horizontal radius of 600 metres of the aircraft. This definition supports minimum height and noise-abatement rules.

Question 23Air Law and ATC Procedures

Two aircraft are approaching head-on and there is a risk of collision. What action should each pilot take?

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

Explanation

When two aircraft are approaching head-on or nearly so and a risk of collision exists, each shall alter its heading to the right. This produces a predictable separation because both pilots turn in the same direction.

Question 24Air Law and ATC Procedures

An aircraft is on a converging course with another aircraft of the same category, and the other aircraft is on the right. Which aircraft has the right of way?

  1. The aircraft on the left
  2. The aircraft at the lower altitude
  3. The aircraft on the right Correct answer.
  4. The aircraft that first reported its position

Explanation

When two aircraft of the same category converge at approximately the same level, the aircraft on the right has the right of way. The other aircraft must give way, normally by passing behind and below if necessary.

Question 25Air Law and ATC Procedures

What is the minimum vertical separation normally applied by air traffic control between aircraft in controlled airspace above flight level 290?

  1. 1 000 feet Correct answer.
  2. 300 metres
  3. 600 metres
  4. 2 000 feet

Explanation

Above flight level 290, the reduced vertical separation minimum of 1 000 feet applies to suitably equipped aircraft in designated airspace. Below that level, the conventional minimum is also 1 000 feet in most areas, with 2 000 feet used where RVSM is not applied.

Question 26Air Law and ATC Procedures

Which document normally provides proof that an aircraft has been registered in a particular State?

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

Explanation

The certificate of registration is the document that records an aircraft on the national register of the State and identifies the owner and the registration mark. It establishes nationality, while other documents deal with airworthiness, crew competence, or radio equipment.

Question 27Air Law and ATC Procedures

An aircraft is parked on an apron with its engines running and a person walks toward it. What does a steady red light directed at that person from the control tower mean?

  1. Clear the apron without delay
  2. Proceed with caution
  3. Stop immediately Correct answer.
  4. Return to the terminal building

Explanation

Light signals addressed to persons or vehicles on the movement area follow the same basic colour code used for aircraft: a steady red light means stop. The signal is a direct instruction and the person should halt and await further instructions.

Question 28Air Law and ATC Procedures

Under the Convention on International Civil Aviation, what is the primary role of the International Civil Aviation Organization?

  1. To investigate accidents occurring in the territory of any member State
  2. To develop and adopt international standards and recommended practices for civil aviation Correct answer.
  3. To operate air traffic control services in oceanic airspace on behalf of member States
  4. To certify the airworthiness of individual aircraft on behalf of national authorities

Explanation

ICAO is a specialised agency that adopts Annexes containing standards and recommended practices, which member States then implement through their own national regulations. It is a standard-setting and coordinating body and does not itself provide operational services, certify aircraft, or conduct accident investigations.

Question 29Air Law and ATC Procedures

A pilot plans a flight under visual flight rules in controlled airspace at 2 500 ft above mean sea level in Class C airspace. Which statement describes the clearance requirement?

  1. An air traffic control clearance must be obtained before entering the airspace Correct answer.
  2. No clearance is required provided the aircraft remains clear of cloud
  3. Only a flight plan needs to be filed before departure
  4. A clearance is required only when flying above 3 000 ft

Explanation

Class C airspace is controlled airspace in which all flights require an ATC clearance, and the aircraft must also comply with the applicable VFR weather minima. Filing a flight plan or remaining clear of cloud does not substitute for the clearance itself.

Question 30Air Law and ATC Procedures

An aircraft is being operated on an international flight and the pilot in command holds a licence issued by the State of registry. Which State is responsible for ensuring that the licence complies with the minimum standards of Annex 1?

  1. The State of the operator's principal place of business
  2. The State that issued the licence Correct answer.
  3. The State of first landing on the route
  4. The State whose airspace is being overflown

Explanation

Under the Convention, each contracting State is responsible for licensing its own flight crew and for ensuring that the licences it issues meet the minimum standards of Annex 1. Other States may recognise such licences, but they do not thereby take over responsibility for the standard of the issuing State's certification.

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

In a four-stroke aircraft piston engine, during which stroke does the intake valve normally close?

  1. At the end of the intake stroke, near bottom dead centre Correct answer.
  2. During the exhaust stroke, just before top dead centre
  3. During the compression stroke, shortly after bottom dead centre
  4. At the start of the power stroke, near top dead centre

Explanation

The intake valve opens as the piston begins the intake stroke and closes at the end of that stroke, close to bottom dead centre. Closing at this point traps the fresh charge so the piston can compress it on the following upward stroke.

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

What is the primary function of the magneto in a piston engine ignition system?

  1. To regulate the charging rate of the aircraft battery
  2. To supply low-voltage current to the starter motor
  3. To convert low-voltage direct current into high-voltage pulses for the spark plugs Correct answer.
  4. To measure manifold pressure for the engine gauge

Explanation

A magneto is a self-contained generator that uses rotating magnets and a coil to produce the high voltage needed to jump the spark plug gap. Because it generates its own current, ignition continues even if the aircraft electrical system fails.

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

On an aircraft fitted with a constant-speed propeller, what does the propeller governor do?

  1. It limits the maximum manifold pressure available at full throttle
  2. It feathers the propeller automatically whenever power is reduced
  3. It regulates the mixture strength delivered to the cylinders
  4. It changes the pitch of the blades to maintain the selected RPM Correct answer.

Explanation

The governor senses engine RPM and adjusts oil pressure to the propeller hub so blade pitch changes to hold the RPM selected with the cockpit control. If RPM tends to rise above the setting, the governor increases pitch to load the engine more.

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

Which statement correctly describes the purpose of the aircraft static system?

  1. It provides ambient pressure to the altimeter, airspeed indicator and vertical speed indicator Correct answer.
  2. It supplies pressure to the engine-driven fuel pump
  3. It supplies ram air pressure to the airspeed indicator only
  4. It provides pitot pressure to the turn coordinator

Explanation

The static system vents undisturbed ambient pressure to the instruments that need a pressure reference. The altimeter, airspeed indicator and vertical speed indicator all use static pressure, while the pitot system supplies only total pressure to the airspeed indicator.

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

What is the main purpose of the alternator in a light aircraft electrical system?

  1. To convert alternating current into direct current for the battery
  2. To protect the wiring from excessive current
  3. To generate electrical power while the engine is running Correct answer.
  4. To store electrical energy for use during engine start

Explanation

The engine-driven alternator produces the electrical power used in flight and replenishes the battery. Its output is rectified so that the direct-current system and battery receive the correct polarity.

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

What is the function of the empennage in a conventional aeroplane?

  1. It forms the primary lifting surface
  2. It houses the fuel tanks and provides wing attachment
  3. It provides longitudinal and directional stability and control Correct answer.
  4. It carries the main landing gear loads

Explanation

The empennage comprises the horizontal and vertical stabilisers with their elevators and rudder. These surfaces give stability about the pitch and yaw axes and provide the control inputs for those axes.

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

Why is avgas dyed and graded by octane rating?

  1. To show the fuel's freezing point
  2. To identify the fuel's colour for night refuelling only
  3. To indicate the fuel's sulphur content
  4. To indicate the fuel's resistance to detonation under compression Correct answer.

Explanation

Octane rating expresses how well a fuel resists detonation when compressed in the cylinder. Higher-rated fuel allows higher compression and manifold pressure without the uncontrolled combustion that can damage an engine.

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

What does the red line on an aircraft tachometer indicate?

  1. The maximum continuous RPM approved for the engine Correct answer.
  2. The RPM at which the engine should be cruised
  3. The idle RPM with the throttle closed
  4. The RPM at which the magneto check must be performed

Explanation

The red radial line marks the maximum RPM that may be used continuously without exceeding engine limitations. Exceeding it can overstress the engine and propeller and is outside the approved operating range.

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

An aircraft is climbing at a constant indicated airspeed with the throttle fully open. What happens to manifold pressure as altitude increases?

  1. It remains constant because the throttle is fully open
  2. It increases because the air becomes denser
  3. It rises until the wastegate opens and then remains fixed
  4. It decreases because ambient pressure falls with altitude Correct answer.

Explanation

With a fixed throttle setting, manifold pressure reflects ambient pressure downstream of the throttle. As the aircraft climbs, ambient pressure falls, so the manifold pressure reading decreases even at full throttle.

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

During a magneto check at run-up, the engine runs smoothly on the left magneto but nearly stops when switched to the right. What is the most likely cause?

  1. The right magneto is faulty or its lead is grounded Correct answer.
  2. The propeller governor is set too coarse
  3. The left magneto is faulty and should be replaced
  4. The mixture is too rich at run-up power

Explanation

A large RPM drop or rough running on one magneto indicates that the selected magneto is not producing a good spark. The fault lies with the right magneto circuit, so the aircraft should not be flown until it is corrected.

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

What is the effect of moving the mixture control to lean during cruise at altitude?

  1. It advances the ignition timing automatically
  2. It increases manifold pressure by opening the throttle
  3. It increases the fuel flow to cool the engine
  4. It reduces the fuel flow to match the reduced air density Correct answer.

Explanation

At altitude the air density is lower, so less fuel is needed to maintain the correct fuel-to-air ratio. Leaning reduces fuel flow to prevent an excessively rich mixture that would foul plugs and waste fuel.

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

Why must the carburettor heat control be selected to cold before take-off in an aircraft with a float carburettor?

  1. To prevent the engine from overboosting during the take-off climb
  2. To keep the fuel from vaporising in the lines
  3. To avoid excessive cylinder head cooling on the ground
  4. To ensure the engine receives full power and unfiltered hot air is not used Correct answer.

Explanation

Carburettor heat bypasses the air filter and warms the intake air, which reduces the density of the charge. Applying it for take-off would reduce available power, so it must be selected off for full power.

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

What is carburettor icing most likely to occur at an outside air temperature of about 5 degrees Celsius with high humidity?

  1. Because the air filter becomes blocked with ice
  2. Because the fuel vaporisation and venturi effect cool the mixture below freezing Correct answer.
  3. Only when the temperature is below freezing
  4. Because the engine oil thickens in cold weather

Explanation

Fuel vaporisation and the pressure drop in the venturi absorb heat, so the mixture temperature can fall well below the outside air temperature. Moisture in the air then freezes on the throttle valve and venturi even on mild days.

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

A pilot notices that the ammeter shows a discharge after the alternator fails in flight. What is the most appropriate immediate action?

  1. Turn off all fuel pumps to save electrical power
  2. Reset the master switch repeatedly until the ammeter shows charge
  3. Reduce electrical load and land as soon as practicable Correct answer.
  4. Increase RPM to maximum to restore the alternator

Explanation

With the alternator failed, the battery is the only source of electrical power and its endurance is limited. Shedding non-essential electrical loads conserves battery energy and allows time to reach a suitable landing site.

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

What happens to the indicated airspeed if the pitot tube becomes blocked while the static system remains open, during a climb?

  1. The airspeed indication remains roughly constant
  2. The airspeed indication falls toward zero Correct answer.
  3. The airspeed indication fluctuates rapidly
  4. The airspeed indication increases toward the maximum

Explanation

A blocked pitot traps a fixed pressure in the capsule, while static pressure falls during the climb. The instrument interprets the growing difference as a decreasing speed, so the indication falls toward zero.

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

What is the purpose of the vacuum system in a light aircraft with gyroscopic instruments?

  1. It supplies air to the engine cylinders
  2. It pressurises the cabin for crew comfort
  3. It operates the landing gear retraction mechanism
  4. It drives the attitude indicator and heading indicator Correct answer.

Explanation

Engine-driven vacuum pumps create suction that spins the gyros in the attitude and heading indicators. The turn coordinator is usually electrically driven, which provides some redundancy if the vacuum source fails.

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

Why is a turbocharger used on some light aircraft engines?

  1. To reduce the fuel consumption at low altitude only
  2. To cool the induction air before it reaches the cylinders
  3. To drive the propeller at a constant speed
  4. To maintain manifold pressure and power as altitude increases Correct answer.

Explanation

An exhaust-driven turbine drives a compressor that raises intake pressure above ambient. This allows the engine to maintain manifold pressure and power at higher altitudes where a normally aspirated engine would lose performance.

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

What is indicated by a rising cylinder head temperature together with a falling oil pressure during a climb?

  1. Normal behaviour that requires no attention
  2. Evidence that the magnetos are correctly timed
  3. Possible overheating that warrants reducing power and enriching the mixture Correct answer.
  4. A sign that the oil has become too cold

Explanation

High cylinder head temperature with falling oil pressure suggests the engine is running too hot and the oil is thinning. Reducing power and enriching the mixture lowers combustion temperature and helps restore normal readings.

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

What is the function of the oil cooler bypass valve in an aircraft engine lubrication system?

  1. It allows oil to bypass the cooler when the oil is cold and thick Correct answer.
  2. It filters metal particles from the oil
  3. It maintains oil pressure at a fixed value
  4. It prevents oil from reaching the bearings at high pressure

Explanation

When the oil is cold its viscosity is high and it may not flow easily through the cooler. The bypass valve routes oil around the cooler until it warms and thins, protecting the engine from oil starvation.

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

What is the purpose of the feathering feature on a multi-engine aircraft propeller?

  1. To set a finer pitch for take-off acceleration
  2. To increase thrust during a single-engine climb
  3. To lock the propeller at a fixed RPM for cruise
  4. To align the blades with the airflow to reduce drag from a failed engine Correct answer.

Explanation

Feathering rotates the blades to a high-pitch angle so their leading edges face the relative airflow. This minimises drag and asymmetric yaw from a windmilling propeller after an engine failure.