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BDCA ATPL Knowledge Exam practice questions

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Question 1Air Law and ATC Procedures

Under the Convention on International Civil Aviation (Chicago Convention), which body is the permanent governing organ of the International Civil Aviation Organization?

  1. The Council Correct answer.
  2. The Air Navigation Commission
  3. The Assembly
  4. The Secretariat

Explanation

The Council is the permanent governing body of ICAO, elected by the Assembly for a three-year term and responsible for the ongoing direction of the organization's work between Assembly sessions. The Assembly meets at least once every three years and is not permanent, while the Air Navigation Commission and Secretariat are subordinate technical and administrative bodies.

Question 2Air Law and ATC Procedures

What is the principal purpose of ICAO Annex 14?

  1. Standards for the licensing of flight crew
  2. Procedures for aircraft accident investigation
  3. Rules for the issuance of air operator certificates
  4. Standards and recommended practices for aerodrome design and operations Correct answer.

Explanation

Annex 14 contains the Standards and Recommended Practices governing aerodrome physical characteristics, obstacle limitation surfaces, lighting, marking and operational services. It is the reference document for aerodrome planning and certification, distinct from personnel licensing or accident investigation.

Question 3Air Law and ATC Procedures

An aircraft registered in State A is operated by an operator whose principal place of business is in State B, and the aircraft is not used for international air services. Which State is responsible for issuing the certificate of airworthiness?

  1. State of the Operator only
  2. State of Design only
  3. State of Manufacture
  4. State of Registry Correct answer.

Explanation

The State of Registry is responsible for the airworthiness certification of aircraft on its register, and it may delegate certain functions but retains overall responsibility. The State of the Operator and State of Design have defined roles but do not replace the State of Registry for issuing the certificate of airworthiness.

Question 4Air Law and ATC Procedures

A flight crew member's licence was issued by one Contracting State but the pilot now flies an aircraft registered in another Contracting State. What action does the Chicago Convention require in principle?

  1. Complete re-examination and re-issue of the licence by the State of Registry
  2. Validation or rendering valid of the licence by the State of Registry Correct answer.
  3. Referral to ICAO for direct issue of a new licence
  4. No action, because licences are automatically valid worldwide

Explanation

Article 32 of the Chicago Convention provides that licences issued by one Contracting State shall be rendered valid by other Contracting States for the purpose of flight over their territory, subject to conditions. The receiving State validates the foreign licence rather than re-issuing it, and ICAO does not issue licences to individuals.

Question 5Air Law and ATC Procedures

In radiotelephony, what does the phraseology "STANDBY" mean when spoken by an air traffic controller?

  1. Repeat your last transmission
  2. Wait and I will call you Correct answer.
  3. Contact the next unit on the stated frequency
  4. Cleared for the requested manoeuvre

Explanation

STANDBY is an instruction meaning the pilot should wait and the controller will call back; it is not an approval or clearance. It differs from a clearance, which authorises an action, and from instructions to change frequency or repeat a transmission.

Question 6Air Law and ATC Procedures

An aircraft is instructed to hold at a VOR/DME fix on the 090 radial, right-hand pattern, with 1 minute inbound legs. On arrival over the fix, what is the correct entry procedure?

  1. Teardrop entry
  2. Parallel entry Correct answer.
  3. Direct entry
  4. Offset entry

Explanation

When the aircraft arrives over the holding fix tracking inbound on the holding radial with a right-hand pattern, the outbound leg requires a turn to the right, which corresponds to a parallel entry. Direct entry applies when approaching the fix within the sector that allows a turn onto the outbound leg in the holding direction without a procedure turn.

Question 7Air Law and ATC Procedures

What is the standard separation minimum applied between aircraft at the same level in controlled airspace above FL290 where RVSM is implemented?

  1. 500 feet
  2. 2000 feet
  3. 1000 feet Correct answer.
  4. 4000 feet

Explanation

Within designated RVSM airspace, the vertical separation minimum between suitably equipped aircraft is 1000 feet, reduced from the previous 2000 feet. This applies between FL290 and FL410 inclusive where the State has implemented RVSM.

Question 8Air Law and ATC Procedures

An aircraft on an IFR flight in controlled airspace loses two-way radio communication. Which action is consistent with the standard procedure when the aircraft is in visual meteorological conditions?

  1. Descend immediately to the lowest safe altitude and hold
  2. Turn back to the departure aerodrome at the last assigned level
  3. Squawk 7600 and continue at the last cleared level until intercepted
  4. Continue the flight in VMC and land at the nearest suitable aerodrome Correct answer.

Explanation

The standard lost-communication procedure requires the aircraft to continue in accordance with the last acknowledged clearance and, where visual meteorological conditions prevail, to continue in VMC and land at the nearest suitable aerodrome. Squawking 7600 is correct as an indication, but the flight path regulation is governed by the meteorological conditions and the acknowledged clearance.

Question 9Air Law and ATC Procedures

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

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

Explanation

In the ICAO light signal table, a flashing red light directed at an aircraft on the ground instructs the pilot to 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 10Air Law and ATC Procedures

In the ICAO phonetic alphabet, which word represents the letter Q?

  1. Quebec Correct answer.
  2. Quartz
  3. Quito
  4. Queen

Explanation

The ICAO phonetic alphabet uses Quebec for the letter Q, ensuring unambiguous transmission over radio. Each letter has one fixed word, and substituting other words defeats the purpose of standard phraseology.

Question 11Air Law and ATC Procedures

An aircraft has an emergency and the pilot wishes to alert all stations while retaining the ability to be addressed individually. Which signal should be used?

  1. PAN PAN spoken three times
  2. SECURITE spoken three times
  3. The urgency signal followed by the callsign only
  4. MAYDAY spoken three times Correct answer.

Explanation

MAYDAY, spoken three times, is the distress signal indicating grave and imminent danger and requiring immediate assistance. PAN PAN indicates urgency without immediate danger, and SECURITE announces a safety message.

Question 12Air Law and ATC Procedures

What is the meaning of the transponder code 7500?

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

Explanation

Special purpose codes are 7500 for unlawful interference, 7600 for radio communication failure and 7700 for a general emergency. These codes must be selected without voice transmission when the situation requires it.

Question 13Air Law and ATC Procedures

Under ICAO rules, when must a flight plan be submitted for a flight that will cross an international boundary?

  1. At least 10 minutes before departure
  2. No flight plan is needed if the flight is under VFR
  3. At least 60 minutes before departure unless the State prescribes otherwise Correct answer.
  4. Immediately after take-off

Explanation

ICAO Annex 2 requires a flight plan to be submitted before departure, and for flights crossing international borders the standard practice is at least 60 minutes before departure unless the appropriate authority prescribes otherwise. The flight plan allows air traffic services to prepare for the flight and coordinate with adjacent units.

Question 14Air Law and ATC Procedures

What is the minimum horizontal distance from cloud that a VFR flight must maintain in Class C airspace at 5000 feet AMSL in a State that applies the standard ICAO minima?

  1. 500 metres
  2. 300 metres
  3. 5 kilometres
  4. 1500 metres Correct answer.

Explanation

In Class C airspace at and above 3000 feet AMSL, the standard VFR minima include a horizontal distance from cloud of 1500 metres and a vertical distance of 300 metres, with flight visibility of 5 kilometres. The lower minima of 500 metres apply only in certain lower-level or special airspace cases.

Question 15Air Law and ATC Procedures

What does Class D airspace provide under the ICAO airspace classification?

  1. IFR and VFR flights with no ATC service provided to VFR
  2. IFR flights only, all separated from each other
  3. IFR and VFR flights are permitted and all receive an ATC service, with IFR separated from IFR and traffic information given to VFR Correct answer.
  4. IFR and VFR flights with separation provided between all aircraft

Explanation

Class D permits both IFR and VFR flights; all receive an air traffic control service, IFR flights are separated from each other, and traffic information is passed to VFR flights about other traffic. Separation is not provided between VFR flights or between VFR and IFR flights in Class D.

Question 16Air Law and ATC Procedures

An aerodrome has a runway designated 27. What is the approximate magnetic direction of the runway centreline?

  1. 027 degrees
  2. 270 degrees Correct answer.
  3. 072 degrees
  4. 207 degrees

Explanation

Runway designators are the magnetic heading of the runway centreline rounded to the nearest 10 degrees, with the last digit omitted. A runway designated 27 therefore has a centreline heading of approximately 270 degrees magnetic.

Question 17Air Law and ATC Procedures

What is the purpose of a runway holding position marking at an aerodrome?

  1. To indicate the start of the take-off run available
  2. To indicate where an aircraft must stop before entering a runway, unless cleared Correct answer.
  3. To show the touchdown zone of the runway
  4. To mark the boundary of the apron

Explanation

Runway holding position markings consist of yellow lines across the taxiway at the point where an aircraft must stop unless it has an explicit clearance to enter or cross the runway. They protect the runway strip from inadvertent incursion by taxiing aircraft.

Question 18Air Law and ATC Procedures

An operator's minimum equipment list allows dispatch with an inoperative item. Which statement best describes the legal basis for this?

  1. The State of Registry approves the MEL, which defines the conditions under which the aircraft may be operated with specified equipment inoperative Correct answer.
  2. The MEL applies only to non-commercial flights
  3. The operator may self-authorise any inoperative item without State involvement
  4. The MEL replaces the certificate of airworthiness permanently

Explanation

The MEL is approved by the State of Registry and specifies the equipment that may be inoperative, the rectification intervals and any operational or maintenance procedures required. It provides a controlled deviation from the airworthiness requirements without invalidating the certificate of airworthiness.

Question 19Air Law and ATC Procedures

Under the Chicago Convention, what is the status of the Annexes adopted by the Council?

  1. They are advisory guidance with no obligation on Contracting States
  2. They are Standards and Recommended Practices that Contracting States undertake to implement, with notification of differences Correct answer.
  3. They are directly binding laws in every State without any national implementation
  4. They apply only to aircraft engaged in non-scheduled operations

Explanation

Annexes contain Standards, which are mandatory for Contracting States to implement, and Recommended Practices, which are desirable, and States must notify ICAO of any differences. National regulations implement the Annexes, so they are not directly self-executing in domestic law.

Question 20Air Law and ATC Procedures

Which factor determines the classification of an occurrence as an accident rather than a serious incident under Annex 13?

  1. Whether the flight was conducted under IFR or VFR
  2. Whether the occurrence was reported by the pilot or by the operator
  3. Whether the aircraft was above or below 10 000 feet
  4. Whether a person was fatally or seriously injured, or the aircraft sustained substantial damage or was missing Correct answer.

Explanation

Annex 13 defines an accident by the consequences: a person is fatally or seriously injured, the aircraft sustains damage or structural failure beyond defined limits, or the aircraft is missing or inaccessible. A serious incident involves circumstances indicating a high probability of an accident but without those consequences.

Question 21Air Law and ATC Procedures

An aircraft is intercepted by a military aircraft. According to ICAO procedures, what should the intercepted aircraft do?

  1. Continue on the cleared route and ignore the intercepting aircraft
  2. Take evasive action and descend immediately without communication
  3. Squawk 7700 and turn towards the nearest aerodrome regardless of the intercepting aircraft
  4. Immediately attempt to establish radio communication, comply with the intercepting aircraft's instructions, and notify the appropriate ATS unit Correct answer.

Explanation

ICAO interception procedures require the intercepted aircraft to follow the intercepting aircraft's signals, attempt radio contact on the designated frequencies, and inform the relevant ATS unit. The intercepting aircraft's instructions take precedence, and the pilot should not take independent evasive action that could be misconstrued.

Question 22Air Law and ATC Procedures

In reduced vertical separation minimum airspace, which condition must be satisfied before an aircraft may be cleared at an RVSM level?

  1. The aircraft must be equipped with a weather radar
  2. The aircraft must have a minimum of three crew members
  3. The aircraft must be RVSM approved and the crew must be qualified for RVSM operations Correct answer.
  4. The aircraft must be operating under VFR

Explanation

RVSM airspace requires that the aircraft holds RVSM approval confirming the accuracy of its altimetry system and that the flight crew is trained and qualified for RVSM operations. Non-approved aircraft must be separated by the conventional 2000 feet or be excluded from the airspace.

Question 23Air Law and ATC Procedures

What does the abbreviation ATIS stand for and what is its function?

  1. Airborne Traffic Information Service, giving collision warnings in the air
  2. Automatic Terminal Information Service, providing continuous recorded information on weather and aerodrome conditions Correct answer.
  3. Aerodrome Traffic Identification Service, identifying aircraft on approach
  4. Air Traffic Information System, providing radar separation instructions

Explanation

ATIS is the Automatic Terminal Information Service, a continuous broadcast of recorded non-control information such as weather, runway in use and approach aids. It reduces controller workload by giving pilots routine information before contact.

Question 24Air Law and ATC Procedures

Under the Convention, what does a State undertake when it registers an aircraft?

  1. It becomes responsible only for the aircraft while it is in its own territory
  2. It delegates oversight permanently to the State of Manufacture
  3. It assumes jurisdiction and control over the aircraft in matters of airworthiness, personnel licensing and operation Correct answer.
  4. It transfers all regulatory authority to ICAO

Explanation

Article 17 of the Chicago Convention provides that aircraft have the nationality of the State in which they are registered, and Article 12 and related provisions place jurisdiction and control over airworthiness, licensing and operations with the State of Registry. This responsibility continues even when the aircraft operates abroad.

Question 25Aircraft General Knowledge - Airframe, Systems and Powerplant

In a gas turbine engine, which component extracts energy from the exhaust gas to drive the compressor?

  1. The diffuser
  2. The combustion chamber
  3. The turbine Correct answer.
  4. The nozzle guide vanes

Explanation

The turbine converts pressure and kinetic energy of the combustion gases into shaft work, and that shaft drives the compressor (and on a free-turbine engine, the propeller). The diffuser slows air to raise static pressure, while the combustion chamber adds heat energy rather than extracting it.

Question 26Aircraft General Knowledge - Airframe, Systems and Powerplant

Which structural member carries the main bending loads of a semi-monocoque wing?

  1. The spar booms Correct answer.
  2. The skin alone
  3. The ribs
  4. The stringers

Explanation

Spar booms (caps) are the heavy longitudinal members located at the top and bottom of the spar, and they carry the bending loads in tension and compression. The skin and stringers contribute to shear and stiffening, and ribs maintain the aerofoil shape and transfer loads.

Question 27Aircraft General Knowledge - Airframe, Systems and Powerplant

Aircraft hydraulic fluid is specified with a high viscosity index primarily because:

  1. It allows the fluid to remain effective over a wide temperature range Correct answer.
  2. It prevents the formation of air bubbles in the reservoir
  3. It reduces the fire risk in the event of a leak
  4. It increases the compressibility of the fluid

Explanation

A high viscosity index means the fluid's viscosity changes relatively little as temperature varies, so it keeps sealing and lubricating properties from cold soak to high operating temperatures. Fire resistance and anti-foaming are separate properties controlled by fluid type and additives, not by viscosity index.

Question 28Aircraft General Knowledge - Airframe, Systems and Powerplant

In a typical aircraft electrical system, the purpose of the busbar is to:

  1. Convert alternating current to direct current
  2. Provide a common distribution point for electrical power Correct answer.
  3. Limit the current drawn by each consumer
  4. Store electrical energy for emergency use

Explanation

A busbar is a common conductor to which generators, batteries and consumers are connected so that power can be distributed to many circuits. Conversion, current limiting and energy storage are functions of rectifiers, circuit breakers and batteries respectively.

Question 29Aircraft General Knowledge - Airframe, Systems and Powerplant

During a normal pressurisation cycle, the cabin pressure controller regulates the outflow valve in order to:

  1. Control the flow of bleed air entering the cabin
  2. Control the temperature of the cabin supply air
  3. Control the rate at which cabin air escapes to atmosphere Correct answer.
  4. Control the speed of the air-conditioning pack compressor

Explanation

The outflow valve sets the rate at which air leaves the cabin, and therefore governs both cabin differential pressure and the rate of change of cabin altitude. Inflow is set by the bleed and pack system, while temperature is controlled separately by the pack and trim air.

Question 30Aircraft General Knowledge - Airframe, Systems and Powerplant

Which type of flap increases wing area as well as camber when extended?

  1. Fowler flap Correct answer.
  2. Split flap
  3. Slotted flap
  4. Plain flap

Explanation

A Fowler flap translates aft before hinging down, so it increases both wing chord area and camber, giving a large lift increase. Plain, split and simple slotted flaps change camber only and do not significantly increase wing area.

Question 31Aircraft General Knowledge - Airframe, Systems and Powerplant

In a four-stroke piston engine, the camshaft of a typical horizontally opposed engine rotates at:

  1. One quarter of the crankshaft speed
  2. Half the crankshaft speed Correct answer.
  3. The same speed as the crankshaft
  4. Twice the crankshaft speed

Explanation

Each valve must open once every two crankshaft revolutions in a four-stroke cycle, so the camshaft is driven through a 2:1 reduction and turns at half crankshaft speed. This relationship holds regardless of cylinder arrangement.

Question 32Aircraft General Knowledge - Airframe, Systems and Powerplant

A propeller blade is twisted along its span so that:

  1. The blade is structurally stronger at the hub
  2. Each section operates at a similar angle of attack along the blade Correct answer.
  3. The propeller can be feathered without vibration
  4. Centrifugal loads are balanced along the blade

Explanation

Because the rotational speed of a blade section increases with radius, the blade angle must be reduced towards the tip so that each section meets the relative airflow at a similar angle of attack. This keeps lift distribution and efficiency reasonably uniform along the span.

Question 33Aircraft General Knowledge - Airframe, Systems and Powerplant

The primary function of the firewall in an engine compartment is to:

  1. Contain a fire in the engine compartment and protect the rest of the aircraft Correct answer.
  2. Reduce engine noise transmitted to the cabin
  3. Support the engine mounts
  4. Provide cooling air ducting to the engine

Explanation

A fireproof firewall separates the engine compartment from the cockpit and cabin so that a fire is contained and hazardous fumes and flames are kept away from occupants. It must resist flames and heat for a defined period, and all passages through it must be sealed.

Question 34Aircraft General Knowledge - Airframe, Systems and Powerplant

In a closed-centre hydraulic system with the engine running and no services selected, the pump output is:

  1. Full flow returned to the reservoir through the relief valve
  2. Full flow directed to the actuators
  3. Reduced to a small flow to make up internal leakage Correct answer.
  4. Zero, because the pump is de-clutched

Explanation

A closed-centre pump is of variable-displacement type and its swashplate is held at near-neutral when system pressure is satisfied, so it delivers only enough flow to replace internal leakage. This keeps power consumption and fluid heating low when no service is demanded.

Question 35Aircraft General Knowledge - Airframe, Systems and Powerplant

Which material property is most important for the turbine blades of a gas turbine engine?

  1. High electrical conductivity
  2. High thermal expansion coefficient
  3. Low density at room temperature
  4. High creep resistance at elevated temperature Correct answer.

Explanation

Turbine blades operate in the hottest part of the engine under high centrifugal stress, so resistance to creep and thermal fatigue at high temperature is the governing requirement. Nickel-based superalloys and cooling passages are used to achieve this.

Question 36Aircraft General Knowledge - Airframe, Systems and Powerplant

The purpose of the anti-icing system on a piston engine air intake is to:

  1. Increase the density of the intake air
  2. Cool the intake air before it reaches the cylinders
  3. Prevent ice forming in the carburettor or throttle body Correct answer.
  4. Reduce the noise produced by the induction system

Explanation

Ice can form in the carburettor venturi or around the throttle plate due to fuel vaporisation and pressure drop, even at outside air temperatures above freezing. The anti-icing system supplies heated air to that region to prevent or clear this ice.

Question 37Aircraft General Knowledge - Airframe, Systems and Powerplant

A landing gear shock strut uses both compressed gas and hydraulic fluid because:

  1. The fluid supports the weight while the gas provides damping
  2. Both the gas and the fluid are needed to lock the gear down
  3. The gas supports the aircraft weight while the fluid provides damping Correct answer.
  4. The gas provides lubrication while the fluid provides flotation

Explanation

In an oleo strut the compressed nitrogen acts as a spring that absorbs landing loads and supports the aircraft, while oil forced through an orifice damps the oscillation. Separating the two functions prevents the aircraft from bouncing after touchdown.

Question 38Aircraft General Knowledge - Airframe, Systems and Powerplant

Which of the following best describes the function of a vortex generator on an aircraft surface?

  1. It reduces the wing bending moment in turbulence
  2. It energises the boundary layer to delay flow separation Correct answer.
  3. It increases the critical Mach number of the wing
  4. It provides additional lift at low speed like a slat

Explanation

A vortex generator is a small vane that creates a vortex which mixes higher-energy free-stream air into the boundary layer, delaying separation and maintaining control effectiveness. It does not significantly change the wing's critical Mach number or act as a high-lift device.

Question 39Aircraft General Knowledge - Airframe, Systems and Powerplant

In a fuel system, the purpose of the fuel/oil heat exchanger is to:

  1. Increase the fuel pressure before the high-pressure pump
  2. Warm the fuel to improve its flow to the injectors
  3. Remove water from the fuel by boiling it off
  4. Cool the engine oil using the fuel and warm the fuel in the process Correct answer.

Explanation

A fuel/oil heat exchanger transfers heat from the hot engine oil to the comparatively cold fuel, cooling the oil and simultaneously raising fuel temperature to prevent ice blockage in the fuel filter. Pressure raising is the job of the pumps.

Question 40Aircraft General Knowledge - Airframe, Systems and Powerplant

An aircraft battery is connected to the DC bus through a contactor that opens when the battery master switch is off. This arrangement primarily ensures that:

  1. The battery supplies only essential services in flight
  2. The battery cannot be overcharged by the generator
  3. The battery is isolated from the bus when the aircraft is parked Correct answer.
  4. The battery voltage is regulated to a constant value

Explanation

The battery master contactor connects the battery to the DC distribution system only when selected, so that the battery is isolated on the ground and cannot be inadvertently discharged. Overcharge protection and voltage regulation are functions of the generator control unit.

Question 41Aircraft General Knowledge - Airframe, Systems and Powerplant

If the cabin altitude of a pressurised aircraft is held constant while the aircraft climbs, the cabin differential pressure will:

  1. Remain constant
  2. Increase Correct answer.
  3. Become negative
  4. Decrease

Explanation

Differential pressure is cabin pressure minus ambient pressure. If the cabin altitude is constant, cabin pressure is constant, while ambient pressure falls with increasing aircraft altitude, so the difference grows until the maximum differential is reached and the controller then allows cabin altitude to climb.

Question 42Aircraft General Knowledge - Airframe, Systems and Powerplant

The function of the constant-speed drive (CSD) on an engine-driven AC generator is to:

  1. Maintain a constant generator output frequency regardless of engine speed Correct answer.
  2. Maintain constant generator output voltage
  3. Limit the generator output current
  4. Provide a constant oil supply to the generator

Explanation

Generator frequency is proportional to rotational speed and the number of poles, so a constant-speed drive keeps the generator turning at the same speed while engine rpm varies, giving a stable 400 Hz supply. Voltage regulation and current limiting are handled by the generator control unit.

Question 43Aircraft General Knowledge - Airframe, Systems and Powerplant

Compared with a single-spool turbojet, the addition of a bypass (turbofan) arrangement improves propulsive efficiency mainly because:

  1. It increases the exhaust gas temperature
  2. It removes the need for a turbine
  3. It increases the compressor pressure ratio
  4. It accelerates a larger mass of air to a lower velocity Correct answer.

Explanation

Propulsive efficiency improves when a given thrust is produced by accelerating a larger mass of air to a lower velocity. A bypass fan does exactly this, and the cooler, slower bypass stream also reduces jet noise.

Question 44Aircraft General Knowledge - Airframe, Systems and Powerplant

In a stressed-skin (semi-monocoque) fuselage, the primary role of the frames is to:

  1. Maintain the cross-sectional shape and support the skin Correct answer.
  2. Carry the longitudinal bending loads
  3. Provide attachment points for the wings only
  4. Carry the torsional loads of the fuselage

Explanation

Frames are transverse members that hold the fuselage cross-section to shape, support the stringers and skin, and limit skin buckling. Longitudinal bending is carried mainly by the skin and stringers, and torsion is carried by the skin in a closed shell.

Question 45Aircraft General Knowledge - Airframe, Systems and Powerplant

A hydraulic system is fitted with a pressure relief valve in addition to a variable-displacement pump. The relief valve is primarily provided to:

  1. Regulate the rate of flow to the actuators
  2. Allow manual operation of the system in an emergency
  3. Protect the system against excessive pressure if the pump control fails Correct answer.
  4. Maintain system pressure during normal operation

Explanation

The variable-displacement pump normally controls pressure itself, so the relief valve is a backup device that opens only if the pump control malfunctions or pressure transients occur. It therefore protects lines and components from overpressure.

Question 46Aircraft General Knowledge - Airframe, Systems and Powerplant

The main advantage of a dual ignition system in a piston engine is that it:

  1. Eliminates the need for magneto timing adjustments
  2. Improves combustion and provides redundancy in case of one system failing Correct answer.
  3. Allows the engine to run on two different fuel grades
  4. Reduces the compression ratio of the engine

Explanation

Two spark plugs per cylinder give faster, more complete combustion with a shorter flame path, improving power and efficiency, and they provide a second independent ignition source so the engine keeps running if one system fails.

Question 47Aircraft General Knowledge - Airframe, Systems and Powerplant

During an automatic pressurisation failure in which the outflow valve sticks fully open at high altitude, the crew expects:

  1. A rapid cabin climb and a requirement for oxygen and emergency descent Correct answer.
  2. A rapid cabin descent with no crew action required
  3. Cabin altitude to remain constant while the packs are on
  4. Cabin differential pressure to rise above the maximum limit

Explanation

With the outflow valve open, cabin air escapes as fast as it enters, so cabin altitude rises toward aircraft altitude and the crew must use oxygen and descend to a breathable level. Differential pressure cannot exceed the limit because the valve is open.

Question 48Aircraft General Knowledge - Airframe, Systems and Powerplant

Which of the following describes the purpose of the compressor bleed air used in a modern transport aircraft?

  1. To supply air conditioning, pressurisation and engine anti-icing Correct answer.
  2. To cool the combustion chamber walls only
  3. To drive the engine's own turbine
  4. To increase the fuel pressure at the injectors

Explanation

Bleed air tapped from the compressor is used for cabin air conditioning and pressurisation, engine and wing anti-icing, and sometimes for starting and hydraulic reservoir pressurisation. It is not used to drive the turbine, which is driven by combustion gas.

Question 49Flight Performance and Planning

In aircraft mass and balance, what is meant by the datum point?

  1. The point where the nose wheel contacts the ground
  2. The point at which fuel is loaded into the tanks
  3. The reference point from which all longitudinal arms are measured Correct answer.
  4. The point through which the aircraft's weight acts

Explanation

The datum is an arbitrary reference point defined by the manufacturer, usually located at or near the nose, from which all longitudinal distances (arms) are measured. It has no physical significance for the aircraft's balance; it simply provides a fixed origin so that every arm is measured consistently.

Question 50Flight Performance and Planning

An aircraft has a mass of 2,000 kg and its centre of gravity is 2.5 m aft of the datum. What is the total moment about the datum?

  1. 800 kg·m
  2. 4,500 kg·m
  3. 2,000 kg·m
  4. 5,000 kg·m Correct answer.

Explanation

Moment is the product of mass and arm, so 2,000 kg multiplied by 2.5 m gives 5,000 kg·m. The moment is used when combining items to find the overall centre of gravity by dividing total moment by total mass.