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EASA Part-66 Module11 aeroplane systems foundations study materials
EASA Part-66 Module11 aeroplane systems foundations study resources

EASA Part-66 Module11 aeroplane systems foundations practice questions

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Question 1Aerodynamic principles

On a swept-wing turbine aeroplane, the speed at which airflow over the upper wing surface first reaches Mach 1.0 (M=1.0) locally while the aircraft itself is still subsonic is known as the:

  1. Critical Mach number (Mcrit) Correct answer.
  2. Mach number
  3. Coffin corner speed
  4. Drag divergence Mach number

Explanation

The critical Mach number (Mcrit) is the free-stream Mach number at which the local airflow over the wing first reaches the speed of sound (M=1.0), marking the onset of transonic effects and shock-wave formation.

Question 2Aerodynamic principles

As airflow passes through a normal shock wave on the upper surface of a wing in transonic flight, the static pressure of the air:

  1. Decreases and velocity increases
  2. Increases and velocity decreases to subsonic Correct answer.
  3. Remains constant while temperature falls
  4. Decreases while density falls

Explanation

Across a normal shock wave the flow decelerates from supersonic to subsonic, so static pressure, density and temperature all increase abruptly while velocity drops below M=1.0.

Question 3Aerodynamic principles

A leading-edge slat improves the low-speed lift of a wing primarily by:

  1. Increasing the wing camber only
  2. Reducing the wing area to lower stall speed
  3. Energising the boundary layer and delaying the stall to a higher angle of attack Correct answer.
  4. Increasing the chord line incidence relative to the fuselage

Explanation

A slat opens a slot that ducts high-energy air from below to the upper surface, re-energising the boundary layer so the flow stays attached and the stall is delayed to a higher angle of attack and higher CLmax.

Question 4Aerodynamic principles

On a large transport aeroplane, roll control at high speed is often provided by spoilers in addition to ailerons mainly because:

  1. Spoilers create more lift than ailerons
  2. Ailerons cannot be powered hydraulically
  3. Spoilers reduce the aircraft's stall speed
  4. Outboard ailerons can cause wing twist (aileron reversal) at high dynamic pressure Correct answer.

Explanation

At high dynamic pressure, deflecting an outboard aileron can twist a flexible wing and reverse the rolling moment (aileron reversal); roll spoilers and/or locked-out inboard ailerons avoid this by dumping lift on one wing.

Question 5Aerodynamic principles

The drag-divergence Mach number is significant in transonic aerodynamics because beyond it:

  1. Wave drag rises sharply due to the formation and strengthening of shock waves Correct answer.
  2. Lift drops to zero
  3. The aircraft becomes uncontrollable in roll
  4. Skin friction drag disappears

Explanation

At the drag-divergence Mach number the drag coefficient begins to climb steeply because shock waves form and intensify on the wing, adding wave drag; swept wings and supercritical aerofoils raise this Mach number.

Question 6Aerodynamic principles

A 'supercritical' aerofoil is used on modern transport wings mainly to:

  1. Reduce the wing's structural weight
  2. Delay the formation of strong shock waves, allowing a higher critical Mach number and efficient high-speed cruise Correct answer.
  3. Increase the stalling angle of attack at low speed
  4. Eliminate the need for high-lift devices

Explanation

A supercritical aerofoil, with its flattened upper surface and aft camber, keeps the upper-surface flow weakly supersonic with a weaker shock, raising the drag-divergence Mach number and improving cruise efficiency.

Question 7Aerodynamic principles

A 'Krueger flap' is a high-lift device fitted to the:

  1. Wing trailing edge
  2. Wing tip
  3. Horizontal stabiliser
  4. Wing leading edge, hinging forward and down to increase camber/lift at low speed Correct answer.

Explanation

A Krueger flap is a leading-edge device that hinges forward and down from the lower surface, increasing wing camber and CLmax at low speed, often used on the inboard leading edge.

Question 8Aerodynamic principles

A Fowler flap increases lift more than a plain flap because, as it extends, it:

  1. Moves aft as well as down, increasing both the wing area and the camber Correct answer.
  2. Only deflects downward without moving aft
  3. Reduces the wing chord
  4. Acts as a spoiler

Explanation

A Fowler flap translates rearward on tracks while deflecting down, so it increases the effective wing area as well as the camber, giving a large lift increase with relatively little drag at small settings.

Question 9Aerodynamic principles

Wing sweep is used on high-speed transport aeroplanes primarily to:

  1. Reduce the wingspan for gate clearance
  2. Increase the critical Mach number by reducing the effective velocity component normal to the wing leading edge Correct answer.
  3. Improve low-speed stall characteristics
  4. Reduce the structural weight of the wing

Explanation

Sweeping the wing reduces the component of airflow velocity perpendicular to the leading edge, so compressibility/shock effects are delayed to a higher free-stream Mach number, raising the critical Mach number for efficient high-speed cruise.

Question 10Aerodynamic principles

'Vortex generators' on the upper wing surface of a transport are small vanes fitted to:

  1. Reduce parasite drag in cruise
  2. Generate electrical power from the airflow
  3. Re-energise the boundary layer to delay airflow separation over the control surfaces and at high angles of attack Correct answer.
  4. Increase fuel tank capacity

Explanation

Vortex generators create small vortices that mix high-energy free-stream air into the boundary layer, keeping it attached longer; this delays separation, improving control effectiveness and high-angle-of-attack behaviour.

Question 11Structures, controls and landing gear

In a 'fail-safe' airframe structural design philosophy, structural integrity after a single failure is assured because:

  1. Multiple load paths exist so remaining structure carries the load until the failure is detected Correct answer.
  2. Every component is replaced at a fixed flight-hour life regardless of condition
  3. The component is designed never to crack within the aircraft's life
  4. Inspections are eliminated because the part cannot fail

Explanation

Fail-safe design provides redundant (multiple) load paths so that if one member fails, the load is carried by the remaining structure long enough for the damage to be found and repaired at the next inspection.

Question 12Structures, controls and landing gear

A semi-monocoque fuselage carries flight loads primarily through:

  1. The skin alone, with no internal structure
  2. Pressurisation air pressure acting on the skin
  3. Solid internal trusses with non-structural skin
  4. A combination of skin (stressed), frames, formers, longerons and stringers Correct answer.

Explanation

In semi-monocoque construction the stressed skin carries a large part of the load but is supported by frames/formers (shape) and longerons/stringers (longitudinal bending), distributing stresses and resisting buckling.

Question 13Structures, controls and landing gear

In a fly-by-wire (FBW) flight control system, the pilot's sidestick or control column movement is converted into:

  1. Electrical signals processed by flight control computers that command the surface actuators Correct answer.
  2. A direct mechanical cable pull to the surface
  3. Hydraulic pressure applied directly to the surface jacks
  4. Pneumatic signals to the actuators

Explanation

In FBW the inceptor produces electrical command signals; flight control computers interpret them (applying laws/limits) and drive the hydraulic or electro-hydraulic actuators that move the surfaces, with no direct mechanical link.

Question 14Structures, controls and landing gear

A 'yaw damper' fitted to a swept-wing jet transport is provided primarily to:

  1. Increase maximum rudder authority for crosswind landings
  2. Automatically counter Dutch roll oscillations by applying small rudder inputs Correct answer.
  3. Trim the aircraft in the pitch axis
  4. Lock the rudder on the ground

Explanation

Swept-wing jets are prone to Dutch roll (a coupled yaw/roll oscillation); the yaw damper senses yaw rate and applies small automatic rudder inputs to damp the oscillation and improve directional stability.

Question 15Structures, controls and landing gear

On many large transports, longitudinal (pitch) trim is achieved by moving the:

  1. Ailerons symmetrically
  2. Leading-edge slats
  3. Trimmable Horizontal Stabiliser (THS), whose incidence is varied Correct answer.
  4. Rudder trim tab

Explanation

Large transports trim in pitch by varying the incidence of the trimmable horizontal stabiliser (THS), which offloads the elevator and sets the trimmed condition far more effectively than a small tab.

Question 16Structures, controls and landing gear

Ground spoilers (lift dumpers) deploying automatically after touchdown improve braking mainly by:

  1. Increasing lift to keep the nose light
  2. Powering the anti-skid system
  3. Reducing drag for a faster roll-out
  4. Dumping wing lift so more aircraft weight is transferred onto the wheels, improving brake and tyre grip Correct answer.

Explanation

Deploying lift dumpers spoils the remaining wing lift, putting the aircraft's weight onto the main wheels; this increases the normal force at the tyres so wheel braking is far more effective, and also adds aerodynamic drag.

Question 17Structures, controls and landing gear

On a retractable landing gear, the 'air/ground' (squat or weight-on-wheels) sensing switch is used to:

  1. Provide a signal indicating whether the aircraft is on the ground, used to enable/inhibit systems such as ground spoilers, thrust reversers and gear retraction Correct answer.
  2. Inflate the tyres on landing
  3. Apply the parking brake automatically
  4. Measure the landing weight of the aircraft

Explanation

The weight-on-wheels (squat) switch, sensing oleo compression, tells aircraft systems whether the aircraft is on the ground; this enables ground spoilers/reversers and inhibits gear retraction and certain warnings as appropriate.

Question 18Structures, controls and landing gear

An anti-skid (anti-lock) braking system improves stopping performance and protects the tyres by:

  1. Increasing brake pressure until the wheels stop turning
  2. Detecting an impending wheel skid and momentarily reducing brake pressure to keep the wheel rolling near maximum friction Correct answer.
  3. Releasing the brakes completely when the aircraft slows below 80 knots
  4. Applying the brakes only on the nose wheel

Explanation

Anti-skid monitors wheel-speed deceleration; if a wheel is about to lock (skid), it briefly reduces brake pressure to that wheel so it keeps rolling near the peak friction point, maximising braking and preventing tyre blowout/flat-spotting.

Question 19Structures, controls and landing gear

The shock absorber on most transport-aircraft landing gear is an oleo-pneumatic strut, which absorbs landing loads by:

  1. Compressing a steel coil spring only
  2. Crushing a honeycomb cartridge
  3. Forcing hydraulic fluid through an orifice while compressing a gas (air/nitrogen) charge Correct answer.
  4. Bending the gear leg elastically

Explanation

An oleo-pneumatic strut absorbs energy as the load forces oil through a metering orifice (damping) while compressing the trapped gas charge (spring); the gas stores energy and the oil dissipates it as heat.

Question 20Structures, controls and landing gear

Cabin windows on a pressurised transport are typically constructed with multiple panes where the:

  1. Inner pane carries the full pressure load and the outer is decorative
  2. Both panes are non-structural
  3. Outer (and middle) pane is structural and carries the pressure differential, with the inner pane acting as a scratch/secondary pane Correct answer.
  4. Window only needs a single thick acrylic pane

Explanation

Pressurised cabin windows use multiple panes; the outer (and a structural middle) pane is designed to carry the cabin pressure differential, while the inner 'scratch' pane protects it and the small bleed hole equalises pressure between panes.

Question 21Structures, controls and landing gear

A 'plug-type' passenger door is designed so that cabin pressure:

  1. Pulls the door outward, requiring strong latches to hold it
  2. Must be released before the door can be sealed
  3. Has no effect on the door because it is hinged externally
  4. Forces the slightly oversized door against its frame from inside, helping to seal and secure it Correct answer.

Explanation

A plug door is larger than its opening and opens inward/then outward; cabin pressure pushes the door against the surrounding frame, improving the seal and making it impossible to open against pressure in flight.

Question 22Structures, controls and landing gear

Under the large-aeroplane airworthiness code (CS-25), the fuselage pressurised structure must be designed to a philosophy that ensures:

  1. Damage tolerance, so that fatigue cracking is detected and the structure retains residual strength between inspections Correct answer.
  2. No inspection is ever required
  3. Unlimited fatigue life with no cracking guaranteed forever
  4. The cabin is never pressurised above ambient

Explanation

CS-25 fatigue and damage-tolerance requirements ensure the pressurised structure can sustain damage (e.g. fatigue cracks) and retain adequate residual strength until that damage is found at scheduled inspections.

Question 23Structures, controls and landing gear

In a hydraulically powered flight control, an 'artificial feel' system is necessary because:

  1. There is no direct aerodynamic load fed back to the pilot, so feel must be simulated to prevent over-controlling Correct answer.
  2. The pilot would otherwise receive too much feedback from the surface
  3. It reduces the hydraulic pressure required
  4. It locks the controls in cruise

Explanation

With fully powered controls the pilot is isolated from the aerodynamic loads on the surfaces; an artificial-feel unit (often q-feel, varying with dynamic pressure) reintroduces resistance so the pilot does not over-control.

Question 24Structures, controls and landing gear

A Mach trim system is fitted to some swept-wing jets to compensate for 'Mach tuck', a tendency at high Mach number for the aircraft to:

  1. Pitch nose-up uncontrollably
  2. Pitch nose-down as the centre of pressure moves aft, which the system counters with automatic pitch correction Correct answer.
  3. Roll to the left
  4. Lose all elevator authority permanently

Explanation

As Mach number increases the wing centre of pressure moves aft, producing a nose-down pitching tendency (Mach tuck); the Mach trim system automatically applies nose-up correction (e.g. via the stabiliser/elevator) to maintain trim.

Question 25Structures, controls and landing gear

Flaperons combine the functions of:

  1. Flaps and spoilers
  2. Elevators and the rudder
  3. Flaps and ailerons (providing both roll control and added camber/lift) Correct answer.
  4. Slats and slots

Explanation

A flaperon is a control surface that acts both as a flap (deflecting down to increase lift/camber) and as an aileron (deflecting differentially for roll control), combining the two functions in one surface.

Question 26Structures, controls and landing gear

A 'balance tab' on a manually operated control surface is designed to move:

  1. In the same direction as the surface to increase control force
  2. To trim the aircraft hands-off
  3. Only on the ground for rigging
  4. In the opposite direction to the surface deflection, reducing the effort needed to move the control Correct answer.

Explanation

A balance tab is mechanically linked to deflect opposite to the main surface; the aerodynamic force on the tab assists the pilot, reducing the control force required to deflect the surface.

Question 27Structures, controls and landing gear

The nose-wheel steering on a large transport is normally powered by:

  1. Direct mechanical linkage from the rudder pedals only
  2. Electric motors in each main-gear wheel
  3. Hydraulic actuators commanded by a tiller and/or rudder pedals, with limited authority on the pedals Correct answer.
  4. Differential braking exclusively

Explanation

Nose-wheel steering uses hydraulic actuators commanded through a steering tiller for large-angle ground manoeuvring and through the rudder pedals for limited-angle steering during take-off/landing roll.

Question 28Structures, controls and landing gear

An autobrake system on a transport aeroplane is selected before landing to:

  1. Disable the wheel brakes for a smoother touchdown
  2. Steer the nose wheel automatically
  3. Increase the landing speed
  4. Automatically apply a pre-selected braking rate (deceleration) once the aircraft is on the ground Correct answer.

Explanation

Autobrake, when armed and triggered (e.g. by ground spoiler deployment/wheel spin-up), automatically applies braking to achieve a selected deceleration level, giving consistent, immediate braking and freeing the crew during the landing roll.

Question 29Structures, controls and landing gear

In aircraft structures, a 'stringer' is a longitudinal member whose main purpose is to:

  1. Maintain the cross-sectional shape of the fuselage
  2. Transmit engine thrust to the wing
  3. Carry the cabin pressure loads alone
  4. Stiffen the skin and carry longitudinal (bending) loads, preventing skin buckling Correct answer.

Explanation

Stringers (and longerons) run lengthwise, attaching to the skin to carry axial bending loads and to stiffen the skin against buckling; frames/formers maintain the cross-section shape.

Question 30Structures, controls and landing gear

A bonded honeycomb sandwich panel (e.g. in flight-control surfaces and floors) is used because it provides:

  1. A high stiffness-to-weight ratio, with the core separating and stabilising the face skins Correct answer.
  2. High weight with low strength
  3. Electrical conductivity for bonding
  4. Resistance to all corrosion without inspection

Explanation

A honeycomb sandwich bonds thin, strong face skins to a lightweight core; this gives a very high stiffness- and strength-to-weight ratio because the core holds the skins apart to resist bending, much like an I-beam.

Question 31Structures, controls and landing gear

The wing 'torsion box' (between the front and rear spars) on a transport aeroplane primarily:

  1. Houses the passenger cabin
  2. Carries wing bending and torsion loads and commonly forms the integral fuel tank Correct answer.
  3. Provides the leading-edge high-lift devices
  4. Is a non-structural fairing

Explanation

The wing torsion box, bounded by the front and rear spars and the upper/lower skins, carries the wing's bending and torsional loads and is usually sealed to act as the integral ('wet') fuel tank.

Question 32Structures, controls and landing gear

The horizontal stabiliser and elevator together provide:

  1. Roll control and roll stability
  2. Lateral lift augmentation
  3. Directional (yaw) stability and yaw control
  4. Longitudinal (pitch) stability and pitch control Correct answer.

Explanation

The horizontal stabiliser provides longitudinal (pitch) static stability, and the elevator (or all-moving stabilator) provides pitch control about the lateral axis.

Question 33Structures, controls and landing gear

A wheel 'fusible plug' (thermal plug) fitted in a transport main wheel is designed to:

  1. Melt at a set temperature to deflate the tyre safely if the wheel/brake overheats, preventing a tyre burst Correct answer.
  2. Indicate tyre pressure electronically
  3. Lock the brake automatically
  4. Balance the wheel assembly

Explanation

Fusible (thermal) plugs in the wheel melt at a predetermined temperature after heavy braking, releasing tyre pressure in a controlled way to prevent an explosive tyre/wheel failure from heat.

Question 34Structures, controls and landing gear

Carbon (carbon-carbon) brakes are widely used on transport aeroplanes instead of steel brakes because they:

  1. Are heavier but cheaper
  2. Offer a high heat capacity and significant weight saving, maintaining performance at high temperatures Correct answer.
  3. Cannot fade under heavy use but rust easily
  4. Require no inspection of wear

Explanation

Carbon brakes have a high heat-sink capacity and are much lighter than equivalent steel brakes, saving weight while sustaining repeated high-energy stops; wear is still monitored via wear indicators.

Question 35Fluid power, cabin environment and water systems

The cabin pressurisation outflow valve principally controls cabin pressure by:

  1. Modulating the rate at which air is allowed to leave the fuselage Correct answer.
  2. Regulating the volume of bleed air entering the cabin
  3. Opening only as an emergency dump valve
  4. Sensing engine N1 and adjusting bleed pressure

Explanation

Inflow from the packs is roughly constant, so cabin pressure is governed by controlling the rate of outflow; the outflow valve modulates how much air escapes the cabin, setting cabin altitude and rate of change.

Question 36Fluid power, cabin environment and water systems

In an air-cycle air-conditioning pack, the cold air leaving the system is produced mainly by:

  1. A refrigerant compressor and evaporator
  2. Expansion of the air across the cold-air unit (ACM) turbine, which extracts energy Correct answer.
  3. Mixing with liquid nitrogen
  4. Passing the air over the battery heat exchanger

Explanation

In an air-cycle machine, hot bleed air is partially cooled in heat exchangers, then expanded across the expansion turbine; the work the air does driving the turbine removes energy, dropping its temperature sharply.

Question 37Fluid power, cabin environment and water systems

The primary source of conditioning air for the packs on a typical turbine transport aeroplane in flight is:

  1. Ram air through the NACA inlets
  2. The cabin recirculation fans only
  3. Engine compressor bleed air Correct answer.
  4. The APU at all times in cruise

Explanation

In flight the packs are normally supplied with engine compressor bleed air; the APU bleed and ground carts are used mainly on the ground, and ram air provides cooling airflow for heat exchangers, not the conditioned supply.

Question 38Fluid power, cabin environment and water systems

A water separator is fitted downstream of the cold-air unit in an air-cycle pack to:

  1. Add humidity to very dry cabin air
  2. Filter ozone from the conditioned air
  3. Cool the air a second time
  4. Remove condensed moisture before the air reaches the cabin to prevent fogging and icing Correct answer.

Explanation

Expansion in the ACM turbine cools the air below its dew point, causing water to condense; the water separator (with a coalescer sock) removes this moisture to prevent duct icing and cabin fogging.

Question 39Fluid power, cabin environment and water systems

A hydraulic accumulator in an aircraft hydraulic system primarily serves to:

  1. Filter contaminants from the fluid
  2. Cool the hydraulic fluid
  3. Convert hydraulic pressure to electrical power
  4. Store hydraulic energy, dampen pressure pulsations, and provide emergency/peak-demand flow Correct answer.

Explanation

An accumulator stores fluid under pressure against a gas charge, smoothing pump pressure pulsations, supplying short bursts of peak demand, and providing a reserve of pressurised fluid for emergency use (e.g. parking brake).

Question 40Fluid power, cabin environment and water systems

An Engine-Driven Pump (EDP) in a hydraulic system is usually supplemented by an Electric Motor-Driven Pump (EMDP) so that:

  1. The system runs at a lower pressure
  2. Hydraulic power is available even when the related engine is shut down or its EDP fails Correct answer.
  3. The reservoir does not need pressurising
  4. Fluid does not need filtering

Explanation

An EMDP provides an alternative power source for the hydraulic system, maintaining pressure when the engine (and thus its EDP) is not running or has failed, improving redundancy.

Question 41Fluid power, cabin environment and water systems

Aircraft hydraulic reservoirs are commonly pressurised (e.g. by bleed air) in order to:

  1. Increase the system operating pressure to 3,000 psi
  2. Filter the returning fluid
  3. Provide a positive head of fluid to the pump inlets and prevent cavitation at altitude Correct answer.
  4. Indicate fluid temperature

Explanation

A pressurised reservoir maintains a positive supply pressure at the pump inlet, preventing cavitation (vapour/air formation) as ambient pressure falls at altitude and ensuring a steady feed to the pumps.

Question 42Fluid power, cabin environment and water systems

A pneumatic (bleed-air) system on a turbine aeroplane typically supplies all of the following EXCEPT:

  1. Engine starting (air turbine starter)
  2. Wing thermal anti-ice
  3. Cabin pressurisation/air conditioning packs
  4. Primary flight control surface movement Correct answer.

Explanation

Bleed air feeds the air-turbine starter, wing/cowl thermal anti-ice and the air-conditioning packs; primary flight controls are moved by hydraulic (or electrohydraulic) actuators, not by the pneumatic system.

Question 43Fluid power, cabin environment and water systems

A pneumatic system 'pre-cooler' is fitted to:

  1. Reduce high-stage engine bleed-air temperature (using fan air) before it is distributed to the systems Correct answer.
  2. Warm the bleed air before it enters the cabin
  3. Remove water from the bleed air
  4. Boost the bleed-air pressure for engine start

Explanation

Engine bleed air is hot; the pre-cooler is an air-to-air heat exchanger that uses fan air to lower the bleed temperature to a safe value before it is supplied to the packs, anti-ice and other users.

Question 44Fluid power, cabin environment and water systems

The maximum cabin differential pressure on a typical transport aeroplane is limited by a relief valve so that:

  1. The cabin altitude can never exceed 8,000 ft
  2. Structural over-pressurisation of the fuselage is prevented if the normal controller fails Correct answer.
  3. The packs always deliver maximum flow
  4. The outflow valve stays fully closed

Explanation

Positive-pressure-relief (safety) valves cap the maximum cabin-to-ambient differential, protecting the fuselage from structural overpressure should the normal pressurisation controller or outflow valve fail.

Question 45Fluid power, cabin environment and water systems

The 'cabin altitude' indicated on the pressurisation panel represents:

  1. The actual altitude of the aircraft above sea level
  2. The maximum altitude the aircraft may climb to
  3. The pressure altitude inside the cabin, i.e. the equivalent altitude for the cabin's internal pressure Correct answer.
  4. The difference between inside and outside pressure

Explanation

Cabin altitude is the equivalent pressure altitude corresponding to the cabin's internal pressure; on a transport it is typically held to a maximum of about 8,000 ft even when the aircraft cruises much higher.

Question 46Fluid power, cabin environment and water systems

An ozone converter is installed in the air-conditioning system of high-altitude aircraft to:

  1. Remove carbon dioxide from the cabin
  2. Cool the bleed air
  3. Add ozone to disinfect the cabin
  4. Catalytically break down ozone in the bleed air to safe concentrations before it reaches the cabin Correct answer.

Explanation

At high cruise altitudes the ambient air contains harmful ozone; a catalytic ozone converter decomposes ozone (to oxygen) in the conditioning air so cabin concentrations stay within limits.

Question 47Fluid power, cabin environment and water systems

A 'mixing chamber' (manifold) in a multi-zone air-conditioning system is used to:

  1. Blend conditioned (cold) pack air with warm air and recirculated cabin air before distributing it to the cabin zones Correct answer.
  2. Separate the bleed air from the engines
  3. Store oxygen for emergency use
  4. Pressurise the hydraulic reservoir

Explanation

The mixing chamber blends cold pack-discharge air with trim (hot) air and recirculated cabin air, providing a balanced supply that is then distributed and trimmed for each cabin/cockpit zone.

Question 48Fluid power, cabin environment and water systems

A Ram Air Turbine (RAT) is deployed to provide emergency power when:

  1. Extra thrust is required for take-off
  2. The aircraft is on the ground for servicing
  3. Normal generation is lost (e.g. all engines/generators failed), driving an emergency generator and/or hydraulic pump Correct answer.
  4. The cabin needs additional cooling

Explanation

The RAT extends into the airstream after a major loss of electrical and/or hydraulic power; the airflow drives it to power an emergency generator and/or hydraulic pump, providing essential services until landing.

Question 49Fluid power, cabin environment and water systems

A hydraulic system 'priority valve' is used to:

  1. Direct all fluid to the reservoir first
  2. Increase pump output beyond rated pressure
  3. Ensure essential services (e.g. flight controls) keep adequate pressure by shutting off lower-priority users when system pressure falls Correct answer.
  4. Bypass the system filter

Explanation

A priority valve isolates non-essential (heavy-demand) services if hydraulic pressure drops, reserving the available fluid/pressure for critical users such as primary flight controls.

Question 50Fluid power, cabin environment and water systems

A Power Transfer Unit (PTU) in a transport hydraulic architecture is used to:

  1. Convert hydraulic power to electrical power
  2. Cool the hydraulic fluid in cruise
  3. Pump fluid between reservoirs
  4. Transfer power hydraulically from one system to another without transferring fluid (mechanically coupled motor-pump) Correct answer.

Explanation

A PTU couples a hydraulic motor in one system to a pump in another; it transfers power (pressure/flow) between the two systems while keeping the fluids separate, providing backup if one system's pumps fail.