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Bahrain CAA ATPL Theory study materials
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Bahrain CAA ATPL Theory practice questions

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Question 1Air Law and ATC Procedures

Under the ICAO Convention on International Civil Aviation (Chicago Convention), which body is responsible for adopting and amending the International Standards and Recommended Practices in the Annexes?

  1. The ICAO Council Correct answer.
  2. The International Air Transport Association
  3. The Air Navigation Commission of the United Nations
  4. The Assembly of all Contracting States

Explanation

The Chicago Convention assigns the adoption and amendment of the Annexes to the ICAO Council, a permanent body of 36 Contracting States elected by the Assembly. The Council acts on proposals developed by the Air Navigation Commission and other technical panels. The Assembly meets periodically to set broad policy but does not itself adopt Annex amendments.

Question 2Air Law and ATC Procedures

What is the legal status of an ICAO Standard when a Contracting State finds it impracticable to comply with it?

  1. The State may ignore the Standard provided it informs IATA
  2. The State is automatically released from the Standard and no notification is needed
  3. The State must notify ICAO of the difference and the Standard remains binding internationally Correct answer.
  4. The State must withdraw from the Chicago Convention

Explanation

Under Article 38 of the Chicago Convention, a State that cannot comply with a Standard must notify ICAO immediately of the differences between its own practice and the Standard. This notification is published so other States are aware. The obligation to file a difference preserves transparency rather than automatically excusing non-compliance.

Question 3Air Law and ATC Procedures

Which document contains the Standards and Recommended Practices relating to Rules of the Air?

  1. Annex 11
  2. Annex 2 Correct answer.
  3. Annex 1
  4. Annex 14

Explanation

Annex 2 to the Chicago Convention is titled Rules of the Air and contains the general operating rules such as right of way, cruising levels and lights to be displayed. Annex 1 covers personnel licensing, Annex 11 covers air traffic services and Annex 14 covers aerodromes. Knowing the Annex numbering is fundamental for air law examinations.

Question 4Air Law and ATC Procedures

In which class of airspace is IFR flight permitted but VFR flight prohibited, with all aircraft subject to ATC clearance?

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

Explanation

Class A airspace permits only IFR flights, and all aircraft require an ATC clearance with continuous two-way radio contact. VFR is not permitted in Class A at all. Classes C, D and E all allow VFR under specified conditions, so only Class A matches the description.

Question 5Air Law and ATC Procedures

An aircraft operating under IFR in controlled airspace loses two-way radio communication. Which action is consistent with the standard ICAO contingency procedure?

  1. Squawk 7600 and continue VFR to the nearest aerodrome
  2. Immediately descend to the lowest safe altitude and hold there
  3. Turn back to the departure aerodrome and land
  4. Continue on the last acknowledged route and level, or the route and level filed, and commence descent at the expected approach time Correct answer.

Explanation

The standard procedure requires the aircraft to maintain the last acknowledged route and level, or the filed route and level if no clearance was received, and to begin descent at the expected approach time or at the point where the pilot expects to commence approach. The transponder should be set to 7600 to alert ATC. Deviating randomly from the clearance would create conflict risk.

Question 6Air Law and ATC Procedures

What is the minimum visibility required for a special VFR flight to operate within a control zone at an aerodrome where no lower minimum has been published?

  1. 5 km
  2. 800 m
  3. 10 km
  4. 1500 m Correct answer.

Explanation

The ICAO standard for special VFR within a control zone requires flight visibility of at least 1500 m and clear of cloud with the surface in sight. Individual States may prescribe different minima in their national regulations. The 1500 m figure is the baseline standard used when no lower national minimum applies.

Question 7Air Law and ATC Procedures

For the purpose of the Rules of the Air, at what point does an aircraft begin its take-off run for the application of the right-of-way rules?

  1. When it reaches rotation speed
  2. When it receives take-off clearance
  3. When it aligns with the runway centreline
  4. When it starts to move under its own power for the purpose of taking off Correct answer.

Explanation

The Rules of the Air define take-off run as beginning when the aircraft starts to move under its own power for the purpose of taking off. This definition matters because right-of-way rules give landing aircraft priority, and aircraft on the ground must give way to aircraft landing or in the final stages of approach. Clearance and alignment are operational steps but not the legal start of the run.

Question 8Air Law and ATC Procedures

Two aircraft are on converging headings at approximately the same level. One has the other on its right. Which aircraft has the right of way?

  1. The aircraft that has the other on its right must give way Correct answer.
  2. The aircraft that has the other on its left must give way
  3. The faster aircraft has the right of way
  4. The aircraft with the lower MTOW has the right of way

Explanation

For converging aircraft at approximately the same level, the aircraft that has the other on its right must give way, allowing the other to pass ahead or climb or descend as appropriate. This mirrors the nautical rule and keeps the manoeuvre predictable. Speed and weight are irrelevant to the right-of-way determination.

Question 9Air Law and ATC Procedures

An aircraft is landing and another aircraft is taxiing on the manoeuvring area. Which has the right of way?

  1. The aircraft with the higher category wake turbulence
  2. The taxiing aircraft if it is on a paved surface
  3. The aircraft that has been cleared first
  4. The landing aircraft Correct answer.

Explanation

Aircraft on the ground must give way to aircraft landing, taxiing or being towed, and in particular to aircraft in the final stages of approach. The landing aircraft has priority because it has limited options once committed to land. Surface type, clearance order and wake category do not alter this priority.

Question 10Air Law and ATC Procedures

When must an aircraft display navigation lights under the Rules of the Air?

  1. Between sunset and sunrise, and at any other time when visibility is reduced Correct answer.
  2. Only when flying above 10 000 ft
  3. Only when flying in controlled airspace
  4. Only when an ATC clearance requires it

Explanation

Navigation lights must be displayed at night, defined as the period between sunset and sunrise, and also during daylight when visibility is reduced by meteorological conditions. The purpose is to make the aircraft's position, heading and relative motion visible to other traffic. Airspace class and altitude do not determine the requirement.

Question 11Air Law and ATC Procedures

A pilot observes a red flare fired from the ground. What does this signal indicate?

  1. Request for the pilot to identify itself
  2. Land immediately at the nearest suitable site
  3. Clearance to land on the active runway
  4. Do not land for the time being Correct answer.

Explanation

A red flare fired from the ground is a signal to aircraft to refrain from landing for the time being, typically because of an obstruction or unsafe condition. A green flare, by contrast, may indicate that landing is permitted. The pilot should acknowledge and follow ATC instructions where radio contact exists.

Question 12Air Law and ATC Procedures

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

  1. The aerodrome is unsafe, do not land Correct answer.
  2. Continue approach and await further instructions
  3. Return to the apron
  4. Cleared to land

Explanation

A series of red flashes directed at an aircraft in flight means that the aerodrome is unsafe and the aircraft must not land. A steady green light would mean cleared to land, while a series of green flashes would mean return for landing. Pilots must acknowledge such signals and act immediately.

Question 13Air Law and ATC Procedures

What is the standard wake turbulence separation for a light aircraft landing behind a heavy aircraft on the same runway?

  1. 3 nautical miles
  2. 4 nautical miles
  3. 8 nautical miles
  4. 6 nautical miles Correct answer.

Explanation

Under the ICAO wake turbulence separation scheme, a light aircraft following a heavy aircraft on the same runway requires 6 NM separation. Medium aircraft behind heavy require 5 NM, and heavy behind heavy requires 4 NM. These minima protect against the strong vortices generated by heavier aircraft.

Question 14Air Law and ATC Procedures

Which of the following correctly describes the function of an ATC clearance?

  1. It transfers responsibility for terrain clearance from the pilot to the controller
  2. It authorises an aircraft to proceed under specified traffic conditions and does not relieve the pilot of responsibility for safety Correct answer.
  3. It replaces the need for the pilot to maintain a listening watch
  4. It guarantees that the flight path is free of all other aircraft

Explanation

An ATC clearance authorises a flight to proceed under specified conditions but does not confer any guarantee of safety or relieve the pilot in command of responsibility. The pilot must still avoid collisions, terrain and weather. Controllers provide separation between known traffic but cannot assume the pilot's legal responsibilities.

Question 15Air Law and ATC Procedures

What does the instruction "line up and wait" authorise an aircraft to do?

  1. Commence the take-off roll immediately
  2. Cross the runway and continue taxiing
  3. Hold short of the runway until further clearance
  4. Enter the runway and occupy it in preparation for take-off but not commence the take-off roll Correct answer.

Explanation

Line up and wait authorises the aircraft to enter the runway and position itself for departure, but the take-off roll must not begin until a take-off clearance is issued. The phrase replaced earlier terminology to remove ambiguity. Crossing a runway or holding short are covered by different instructions.

Question 16Air Law and ATC Procedures

In the ICAO position reporting format, what does the element "next position and ETA" require the pilot to state?

  1. The destination aerodrome and the fuel endurance
  2. The present heading and altitude
  3. The alternate aerodrome and the time of arrival
  4. The next reporting point and the estimated time over it Correct answer.

Explanation

A position report includes the aircraft identification, position, time, flight level, next position and estimated time over it, and the ensuing significant point. The next position and ETA allow ATC to anticipate the flight's progress. Fuel endurance and alternate information are not part of the routine position report.

Question 17Air Law and ATC Procedures

An aircraft is intercepted by a military aircraft and receives the signal of a series of red flashes from the intercepting aircraft. What should the pilot of the intercepted aircraft do?

  1. Descend immediately and land at the nearest aerodrome
  2. Squawk 7700 and continue on the current route
  3. Turn 180 degrees and return to the departure point
  4. Follow the intercepting aircraft and acknowledge by rocking the wings Correct answer.

Explanation

During an interception, a series of red flashes from the intercepting aircraft means follow me, and the intercepted pilot should comply and acknowledge by rocking the wings. This is part of the standard interception signals in Annex 2. Deviating independently could be interpreted as non-compliance and escalate the situation.

Question 18Air Law and ATC Procedures

Under the Convention on Offences and Certain Other Acts Committed on Board Aircraft (Tokyo Convention), which State is normally competent to exercise jurisdiction over an offence committed on board an aircraft in flight?

  1. The State of intended landing
  2. The State of departure of the flight
  3. The State of registration of the aircraft Correct answer.
  4. The State whose airspace the aircraft is overflying

Explanation

The Tokyo Convention establishes the State of registration as the primary State competent to exercise jurisdiction over offences committed on board an aircraft in flight. Other States may exercise jurisdiction in specified circumstances, for example where the offence affects their territory or the safety of their nationals. Departure, destination and overflown States are not automatically the primary competent authority.

Question 19Air Law and ATC Procedures

Which document must be carried on board an aircraft engaged in international navigation under Article 29 of the Chicago Convention?

  1. The certificate of registration Correct answer.
  2. The crew duty roster
  3. The aircraft maintenance schedule
  4. The operations manual of the operator

Explanation

Article 29 lists the documents that must be carried on board, including the certificate of registration, certificate of airworthiness, crew licences, journey log book, radio station licence and, where applicable, the general declaration and cargo manifest. The maintenance schedule, operations manual and duty roster are not among the documents required by Article 29.

Question 20Air Law and ATC Procedures

A pilot in command of an aircraft carrying passengers must have a valid medical assessment. Under the ICAO framework, which class of medical assessment is generally required for a commercial pilot licence holder?

  1. Class 1 Correct answer.
  2. Class 2
  3. No medical assessment is required
  4. Class 3

Explanation

A Class 1 medical assessment is required for the issue and maintenance of a commercial pilot licence or airline transport pilot licence, while a Class 2 is the standard for a private pilot licence. The higher standard reflects the operational demands and passenger safety considerations of commercial flying. Class 3 is used for air traffic controllers in some national systems.

Question 21Aircraft General Knowledge: Airframe, Systems and Powerplant

In a gas turbine engine, what is the primary function of the diffuser section of the compressor outlet?

  1. To increase air velocity before combustion
  2. To cool the air prior to entering the turbine
  3. To remove foreign objects from the airflow
  4. To convert kinetic energy into static pressure rise Correct answer.

Explanation

The diffuser slows the airflow leaving the compressor so that kinetic energy is converted into static pressure, improving combustion efficiency. This pressure rise occurs with little change in total pressure but a marked drop in velocity.

Question 22Aircraft General Knowledge: Airframe, Systems and Powerplant

Which statement best describes the purpose of a fan in a high-bypass turbofan engine?

  1. It meters fuel into the combustion chamber
  2. It drives the high-pressure compressor through a reduction gearbox
  3. It supplies cooling air exclusively to the turbine blades
  4. It produces most of the thrust by accelerating a large mass of air Correct answer.

Explanation

In a high-bypass turbofan the fan accelerates a large mass of air at moderate velocity, and this bypass flow produces the majority of thrust. Core flow through the gas generator contributes a smaller share.

Question 23Aircraft General Knowledge: Airframe, Systems and Powerplant

During starting of a turboprop engine, what is the role of the starter-generator before light-up?

  1. It regulates fuel pressure to the burners
  2. It ignites the fuel-air mixture directly
  3. It controls propeller pitch during the start
  4. It rotates the compressor to provide sufficient airflow for combustion Correct answer.

Explanation

Before fuel is introduced the starter-generator motoring the compressor establishes the airflow and compression needed for reliable ignition and acceleration. Once the engine self-sustains, the unit reverts to generating electrical power.

Question 24Aircraft General Knowledge: Airframe, Systems and Powerplant

What is the main reason turbine blades are often hollow and fed with cooling air?

  1. To permit blade pitch changes in flight
  2. To allow operation at gas temperatures above the blade material's melting point Correct answer.
  3. To balance the axial load on the turbine bearings
  4. To reduce the mass of the rotor for faster acceleration

Explanation

Cooling air bled from the compressor keeps the blade skin temperature below the material limit while the surrounding gas temperature exceeds it, improving specific power. This allows higher turbine entry temperatures than uncooled blades could survive.

Question 25Aircraft General Knowledge: Airframe, Systems and Powerplant

In a constant-speed propeller system, what happens when the pilot selects a higher RPM setting?

  1. The propeller blades move to a feathered position
  2. The governor increases oil pressure to the propeller to coarsen the blade angle
  3. The propeller RPM remains unchanged until airspeed changes
  4. The governor reduces oil pressure to the propeller to allow the blades to move to a finer angle Correct answer.

Explanation

Selecting a higher RPM raises the governor's speeder-spring setting, so it spills oil pressure and the blades move toward fine pitch, reducing load and allowing RPM to rise. The governor then stabilises at the new selected speed.

Question 26Aircraft General Knowledge: Airframe, Systems and Powerplant

What is the function of the torque meter in a turboprop installation?

  1. To indicate the fuel flow to the combustion chamber
  2. To measure the rotational speed of the propeller
  3. To sense the turbine exhaust gas temperature
  4. To measure the engine output torque delivered to the propeller Correct answer.

Explanation

A torque meter measures the twisting moment transmitted through the reduction gearshaft, giving a direct indication of engine power output. Torque is often displayed alongside RPM to compute shaft horsepower.

Question 27Aircraft General Knowledge: Airframe, Systems and Powerplant

Which of the following best describes the purpose of the compressor bleed air system on a large turbofan?

  1. To increase thrust by injecting air into the exhaust
  2. To reduce fuel consumption during cruise
  3. To supply air for cabin pressurisation, anti-icing and engine cooling Correct answer.
  4. To provide lubrication to the main bearings

Explanation

Bleed air is tapped from compressor stages because it is already at high pressure and temperature, making it useful for environmental control, wing and engine anti-icing, and internal cooling. Using bleed air does reduce engine efficiency, so it is managed carefully.

Question 28Aircraft General Knowledge: Airframe, Systems and Powerplant

What is the primary purpose of the accessory gearbox on a turbine engine?

  1. To mount and drive engine accessories such as pumps and generators Correct answer.
  2. To control the variable inlet guide vanes
  3. To reduce the high rotational speed of the turbine for the propeller
  4. To provide the structural attachment of the engine to the wing

Explanation

The accessory gearbox takes a drive from the engine shaft and provides mounting pads and correct speeds for accessories such as fuel pumps, oil pumps, generators and hydraulic pumps. It does not itself reduce speed for the propeller.

Question 29Aircraft General Knowledge: Airframe, Systems and Powerplant

An aircraft hydraulic system uses a constant-pressure variable-displacement pump. When system demand falls to zero, what does the pump do?

  1. It reduces its displacement to near zero while maintaining pressure Correct answer.
  2. It stops rotating to save energy
  3. It bypasses all fluid back to the reservoir through the filter
  4. It continues to deliver full flow through the relief valve

Explanation

A variable-displacement pump senses system pressure and destrokes, reducing output flow almost to zero while holding the set pressure. This avoids wasting energy and overheating the fluid compared with a fixed-displacement pump.

Question 30Aircraft General Knowledge: Airframe, Systems and Powerplant

In a typical aircraft hydraulic system, what is the function of the accumulator?

  1. To cool the hydraulic fluid returning to the reservoir
  2. To automatically select the standby pump
  3. To filter contaminants from the hydraulic fluid
  4. To store pressurised fluid to damp pressure surges and supply temporary flow Correct answer.

Explanation

The accumulator contains a gas-charged chamber separated from the hydraulic fluid, allowing it to absorb pressure pulses and provide a limited reserve of flow during peak demand. It also helps maintain pressure when pumps are briefly unloaded.

Question 31Aircraft General Knowledge: Airframe, Systems and Powerplant

Why is a hydraulic fuse fitted in some aircraft hydraulic systems?

  1. To melt and release pressure in the event of an overheat
  2. To blend two hydraulic fluids of different viscosity
  3. To isolate a leaking downstream line by stopping flow above a set value Correct answer.
  4. To prevent excessive pressure from damaging the pump

Explanation

A hydraulic fuse senses an abnormal flow rate, as would occur with a ruptured line, and closes to confine fluid loss to the affected branch. This preserves the remaining system pressure for other users.

Question 32Aircraft General Knowledge: Airframe, Systems and Powerplant

Which characteristic distinguishes Skydrol-type hydraulic fluid from mineral-based fluid?

  1. It is petroleum based and compatible with natural rubber seals
  2. It is water based and freezes at high altitude
  3. It is phosphate-ester based and resistant to fire but attacks many paints and seals Correct answer.
  4. It is vegetable-oil based and used only in low-pressure systems

Explanation

Skydrol is a phosphate-ester fluid chosen for its fire resistance in high-pressure systems, but it is aggressive to many paints and to natural rubber, requiring compatible seals and careful handling. Mineral fluid is petroleum based and less fire resistant.

Question 33Aircraft General Knowledge: Airframe, Systems and Powerplant

What is the purpose of a shuttle valve in a dual hydraulic system?

  1. To alternate the operating pump at fixed intervals
  2. To allow either of two supply sources to pressurise a common user automatically Correct answer.
  3. To measure the flow rate to each user
  4. To shut off both supplies if pressure drops

Explanation

A shuttle valve has two inlets and one outlet; the higher-pressure source seats the shuttle and supplies the user, so either system can operate the component. This provides redundancy without manual selection.

Question 34Aircraft General Knowledge: Airframe, Systems and Powerplant

In a pneumatic (bleed-air) system, what is the function of a pressure-reducing and shut-off valve?

  1. To increase bleed pressure to the maximum available
  2. To cool the bleed air before it reaches the cabin
  3. To convert bleed air into hydraulic pressure
  4. To regulate bleed pressure to the system and stop the supply when required Correct answer.

Explanation

The pressure-reducing and shut-off valve regulates high engine bleed pressure down to a usable level and can close to isolate the system, for example during an overheat or engine failure. It is a key control element in the pneumatic distribution system.

Question 35Aircraft General Knowledge: Airframe, Systems and Powerplant

What is the primary function of the air conditioning pack in a transport aircraft?

  1. To compress cabin air for pressurisation
  2. To remove smoke from the cargo hold
  3. To condition bleed air to the correct temperature and pressure for the cabin Correct answer.
  4. To generate oxygen for the passenger cabin

Explanation

An air conditioning pack cools, and where necessary reheats, bleed air so that it enters the cabin at the correct temperature and pressure for comfort and pressurisation. It typically includes heat exchangers, a compressor, and a turbine.

Question 36Aircraft General Knowledge: Airframe, Systems and Powerplant

In a cabin pressurisation system, what does the outflow valve control?

  1. The oxygen partial pressure supplied to the masks
  2. The temperature of air entering the cabin
  3. The amount of bleed air taken from the engine
  4. The rate at which air leaves the cabin, thereby controlling cabin pressure Correct answer.

Explanation

The outflow valve modulates the escape of air from the pressurised cabin, and by doing so it sets the cabin altitude and rate of climb or descent. It is commanded by the cabin pressure controller.

Question 37Aircraft General Knowledge: Airframe, Systems and Powerplant

What is the purpose of the negative pressure relief valve in a pressurised aircraft?

  1. To prevent cabin pressure from exceeding the maximum differential
  2. To supply fresh air when packs fail
  3. To prevent cabin pressure from dropping excessively below ambient Correct answer.
  4. To dump cabin pressure rapidly in an emergency

Explanation

If ambient pressure rises above cabin pressure, for example during a rapid descent, the negative pressure relief valve opens inward to prevent the fuselage being loaded in reverse. Positive overpressure is handled by separate relief valves.

Question 38Aircraft General Knowledge: Airframe, Systems and Powerplant

Which of the following describes the purpose of the anti-ice system on a turbofan engine inlet?

  1. To increase airflow into the engine at low speed
  2. To reduce noise from the fan
  3. To cool the inlet air before compression
  4. To prevent ice formation on the inlet lip and guide vanes Correct answer.

Explanation

Hot bleed air is directed to the inlet lip and, on some engines, to the front frame struts to keep surface temperatures above freezing. This prevents ice build-up that could break away and damage the engine.

Question 39Aircraft General Knowledge: Airframe, Systems and Powerplant

What is the function of a fuel-oil heat exchanger in a turbine engine?

  1. To increase the octane rating of the fuel
  2. To separate water from the fuel before combustion
  3. To warm the fuel and cool the engine oil simultaneously Correct answer.
  4. To pressurise the fuel for the burners

Explanation

The fuel-oil heat exchanger transfers heat from the hot engine oil to the colder fuel, warming the fuel to prevent ice blockage and cooling the oil for better lubrication. It performs both functions in a single unit.

Question 40Aircraft General Knowledge: Airframe, Systems and Powerplant

What does the term 'specific fuel consumption' (SFC) mean for a jet engine?

  1. The ratio of fuel mass to air mass in the combustion chamber
  2. The total fuel carried divided by the aircraft weight
  3. The fuel flow required per unit of thrust produced Correct answer.
  4. The maximum fuel flow the engine can accept

Explanation

For a jet engine, SFC is the fuel mass flow divided by the thrust produced, typically expressed in units such as kg per hour per kN. A lower value indicates better fuel efficiency.

Question 41Aircraft General Knowledge: Airframe, Systems and Powerplant

A turbofan engine's exhaust gas temperature (EGT) is highest at which of the following conditions?

  1. Windmilling during an in-flight shutdown
  2. Take-off at maximum thrust Correct answer.
  3. Cruise at reduced thrust
  4. Idle on the ground

Explanation

EGT rises with fuel flow and turbine entry temperature, which peak at maximum take-off thrust. It is therefore used as a limit parameter during take-off and climb.

Question 42Aircraft General Knowledge: Airframe, Systems and Powerplant

What is the purpose of the thrust reverser on a turbofan engine?

  1. To provide reverse rotation of the engine during starting
  2. To increase forward thrust during take-off
  3. To redirect fan or core exhaust forward and produce a decelerating force on the ground Correct answer.
  4. To reduce engine noise during approach

Explanation

A thrust reverser redirects the exhaust flow forward, producing a rearward-acting force that assists braking on landing or during an aborted take-off. It is used only on the ground and is normally interlocked with weight-on-wheels and thrust lever position.

Question 43Aircraft General Knowledge: Airframe, Systems and Powerplant

On a multi-engine aircraft, what is the purpose of the fire detection loop in the engine nacelle?

  1. To shut down the engine automatically on detection
  2. To vent smoke overboard from the nacelle
  3. To sense a fire or overheat condition and provide warning to the crew Correct answer.
  4. To extinguish an engine fire automatically

Explanation

Fire detection loops sense temperature rise or flame and trigger a warning in the cockpit so the crew can act. Extinguishing is a separate function performed by the fire bottles when the crew discharges them.

Question 44Aircraft General Knowledge: Airframe, Systems and Powerplant

What is the function of a fire bottle discharge squib in an engine fire suppression system?

  1. To automatically reset the fire warning after discharge
  2. To rupture the seal and release extinguishing agent when activated Correct answer.
  3. To indicate the pressure of the fire bottle in the cockpit
  4. To detect the presence of fire in the nacelle

Explanation

The squib is a small pyrotechnic charge that, when electrically fired by the crew, opens the bottle and releases the extinguishing agent. It is a one-shot device and must be replaced after use.

Question 45Aircraft General Knowledge: Instrumentation

In a conventional pitot-static system, which pressure source is connected to the case of the vertical speed indicator?

  1. Static pressure Correct answer.
  2. Pitot pressure
  3. Differential pressure from the pitot tube
  4. Total pressure

Explanation

The vertical speed indicator is a differential-pressure instrument that compares the static pressure at the moment with a calibrated internal reference pressure. Its case is fed from the static source, and the rate of change of static pressure is displayed as a climb or descent rate. Pitot pressure is used only by the airspeed indicator.

Question 46Aircraft General Knowledge: Instrumentation

An aircraft climbs at constant true airspeed. In an aircraft with a simple (non-compensated) airspeed indicator, what happens to the indicated airspeed?

  1. It decreases as altitude increases Correct answer.
  2. It shows zero until the aircraft levels off
  3. It increases in proportion to true airspeed
  4. It remains constant at the true airspeed

Explanation

The dynamic pressure sensed by the pitot head depends on density as well as speed, and density falls as altitude increases. For a constant true airspeed the dynamic pressure, and therefore the indicated airspeed, becomes progressively lower. This is why indicated airspeed is always lower than true airspeed at altitude.

Question 47Aircraft General Knowledge: Instrumentation

What is the purpose of the bimetallic compensator fitted inside a pressure altimeter capsule assembly?

  1. To correct for the elastic modulus change of the capsule material with temperature Correct answer.
  2. To compensate for position error of the static source
  3. To damp out short-term turbulence-induced pressure fluctuations
  4. To convert static pressure into a rate of climb signal

Explanation

The elasticity of the evacuated capsule material changes with temperature, which would cause an error in the indicated altitude. A bimetallic compensator changes the mechanical linkage length to offset this effect. The result is that the altimeter reads correctly over a wide temperature range.

Question 48Aircraft General Knowledge: Instrumentation

An aircraft is flying from a region of high pressure to a region of lower pressure while the altimeter subscale is left set at the original QNH. If the aircraft maintains a constant indicated altitude, what is its true altitude doing?

  1. Remaining equal to the indicated altitude
  2. Decreasing below the indicated altitude Correct answer.
  3. Increasing above the indicated altitude
  4. Fluctuating around the indicated altitude

Explanation

The altimeter is calibrated to the standard pressure lapse and interprets a given static pressure as an altitude above the pressure datum set in the subscale. Flying into lower pressure at constant indicated altitude means the aircraft is physically descending. The rule is high to low, watch out below; true altitude becomes less than indicated altitude.

Question 49Aircraft General Knowledge: Instrumentation

In a turn indicator incorporating a rate gyroscope, about which axis is the gyro spin axis aligned?

  1. At 45 degrees to the longitudinal axis
  2. Parallel to the aircraft longitudinal axis
  3. Parallel to the aircraft lateral axis Correct answer.
  4. Parallel to the aircraft vertical axis

Explanation

A rate gyro used for turn indication has its spin axis aligned laterally, parallel to the aircraft pitch axis. When the aircraft yaws, the gyro precesses about its input axis and the resulting deflection is proportional to rate of turn. The instrument therefore indicates rate of turn rather than attitude.

Question 50Aircraft General Knowledge: Instrumentation

What does the slip indicator (the ball in a turn and slip indicator) actually measure?

  1. The pitch attitude relative to the horizon
  2. The bank angle relative to the horizon
  3. The lateral component of the resultant of gravity and centrifugal force Correct answer.
  4. The rate of turn about the yaw axis

Explanation

The ball moves in a curved glass tube and settles where the resultant of gravity and centrifugal acceleration acts. In a coordinated turn this resultant lies along the aircraft vertical and the ball stays centred. The ball therefore indicates lateral acceleration, not turn rate or attitude.