2. AIRFRAME, SYSTEMS AND POWER PLANT

AIRCRAFT GENERAL KNOWLEDGE — AIRFRAME, SYSTEMS AND POWER PLANT
SYSTEM DESIGN, LOADS, STRESSES, MAINTENANCE
System design
Design concepts
Describe the following structural design philosophy:
— safe life;
— fail-safe (multiple load paths);
— damage-tolerant.
Explain the purpose of redundancy in aircraft design.
Level of certification
Explain why some systems are duplicated or triplicated.
Explain that all aircraft are certified according to specifications determined by the competent authority, and that these certification specifications cover aspects such as design, material quality and build quality.
State that the certification specifications for aeroplanes issued by EASA are:
— CS-23 for Normal, Utility, Aerobatic and Commuter Aeroplanes;
— CS-25 for Large Aeroplanes.
State that the certification specifications for rotorcraft issued by EASA are:
— CS-27 for Small Rotorcraft;
— CS-29 for Large Rotorcraft.
Loads and stresses
Stress, strain and loads
Explain how stress and strain are always present in an aircraft structure both when parked and during manoeuvring.
Remark: Stress is the internal force per unit area inside a structural part as a result of external loads. Strain is the deformation caused by the action of stress on a material.
Describe the following types of loads that an aircraft may be subjected to, when they occur, and how a pilot may affect their magnitude:
— static loads;
— dynamic loads;
— cyclic loads.
Describe the areas typically prone to stress that should be given particular attention during a pre-flight inspection, and highlight the limited visual cues of any deformation that may be evident.
Fatigue and corrosion
Describe and explain fatigue and corrosion
Describe the effects of corrosion and how it can be visually identified by a pilot during the pre-flight inspection.
Describe the operating environments where the risk of corrosion is increased and how to minimise the effects of the environmental factors.
Explain that aircraft have highly corrosive fluids on board as part of their systems and equipment.
Explain fatigue, how it affects the useful life of an aircraft, and the effect of the following factors on the development of fatigue:
— corrosion;
— number of cycles;
— type of flight manoeuvres;
— stress level;
— level and quality of maintenance.
Maintenance
Maintenance methods: hard-time and on-condition monitoring
Explain the following terms:
— hard-time or fixed-time maintenance;
— on-condition maintenance;
— condition monitoring.
AIRFRAME
Attachment methods
Attachment methods and detecting the development of faulty attachments
Describe the following attachment methods used for aircraft parts and components:
— riveting;
— welding;
— bolting;
— pinning;
— adhesives (bonding);
— screwing.
Explain how the development of a faulty attachment between aircraft parts or components can be detected by a pilot during the pre-flight inspection.
Materials
Composite and other materials
Explain the principle of a composite material, and give examples of typical non-metallic materials used on aircraft:
— carbon;
— glass;
— Kevlar aramid;
— resin or filler.
State the advantages and disadvantages of composite materials compared with metal alloys by considering the following:
— strength-to-weight ratio;
— capability to tailor the strength to the direction of the load;
— stiffness;
— electrical conductivity (lightning);
— resistance to fatigue and corrosion;
— resistance to cost;
— discovering damage during a pre-flight inspection.
State that several types of materials are used on aircraft and that they are chosen based on type of structure or component and the required/desired material properties.
Aeroplane: wings, tail surfaces and control surfaces
Design
Describe the following types of design and explain their advantages and disadvantages:
— high-mounted wing;
— low-mounted wing;
— low- or mid-set tailplane;
— T-tail.
Structural components
Describe the function of the following structural components:
— spar and its components (web and girder or cap);
— rib;
— stringer;
— skin;
— torsion box.
Loads, stresses and aeroelastic vibrations (flutter)
Describe the vertical and horizontal loads on the ground and during normal flight.
Describe the vertical and horizontal loads during asymmetric flight following an engine failure for a multi-engine aeroplane, and how a pilot may potentially overstress the structure during the failure scenario.
Explain the principle of flutter and resonance for the wing and control surfaces.
Explain the following countermeasures used to achieve stress relief and reduce resonance:
— chord-wise and span-wise position of masses (e.g. engines, fuel, balance masses for wing and control balance masses);
— torsional stiffness;
— bending flexibility;
— fuel-balancing procedures during flight (automatic or applied by the pilot).
Fuselage, landing gear, doors, floor, windscreen and windows
Construction, functions, loads
Describe the following types of fuselage construction:
— monocoque,
— semi-monocoque.
Describe the construction and the function of the following structural components of a fuselage:
— frames;
— bulkhead;
— pressure bulkhead;
— stiffeners, stringers, longerons;
— skin, doublers;
— floor suspension (crossbeams);
— floor panels;
— firewall.
Describe the loads on the fuselage due to pressurisation.
Describe the following loads on a main landing gear:
— touch-down loads (vertical and horizontal);
— taxi loads on bogie gear (turns).
Describe the structural danger of a nose-wheel landing with respect to:
— fuselage loads;
— nose-wheel strut loads.
Describe the structural danger of a tail strike with respect to:
— fuselage and aft bulkhead damage (pressurisation).
Describe the door and hatch construction for pressurised and unpressurised aeroplanes including:
— door and frame (plug type);
— hinge location;
— locking mechanism.
Explain the advantages and disadvantages of the following fuselage cross sections:
— circular;
— double bubble;
— oval;
— rectangular.
Explain why flight-deck windows are constructed with different layers.
Explain the function of window heating for structural purposes.
Explain the implication of a direct-vision window (see CS 25.773(b)(3)).
Explain the need for an eye-reference position.
Explain the function of floor venting (blow-out panels).
Describe the construction and fitting of sliding doors.
Helicopter: structural aspects of flight controls
Design and construction
List the functions of flight controls.
Explain why vertical and horizontal stabilisers may have different shapes and alignments.
Structural components and materials
Describe the fatigue life and methods of checking for serviceability of the components and materials of flight and control surfaces.
Loads, stresses and aeroelastic vibrations
Describe the dangers and stresses regarding safety and serviceability in flight when the manufacturer’s design envelope is exceeded.
Explain that blade tracking is important both to minimise vibration and to help ensure uniformity of flow through the disc.
Describe the early indications and vibrations which are likely to be experienced when the main-rotor blades and tail rotor are out of balance or tracking, including the possible early indications due to possible fatigue and overload.
Explain how a vibration harmonic can be set up in other components which can lead to their early failure.
State the three planes of vibration measurement, i.e. vertical, lateral, fore and aft.
Structural limitations
Maximum structural masses
Define and explain the following maximum structural masses:
— maximum ramp mass;
— maximum take-off mass;
— maximum zero fuel mass;
— maximum landing mass.
Explain that airframe life is limited by fatigue, created by alternating stress and the number of load cycles.
Explain the maximum structural masses:
— maximum take-off mass.
Explain that airframe life is limited by fatigue, created by load cycles.
HYDRAULICS
Hydromechanics: basic principles
Concepts and basic principles
Explain the concept and basic principles of hydromechanics including:
— hydrostatic pressure;
— Pascal’s law;
— the relationship between pressure, force and area;
— transmission of power: multiplication of force, decrease of displacement.
Hydraulic systems
Hydraulic fluids: types, characteristics, limitations
List and explain the desirable properties of a hydraulic fluid with regard to:
— thermal stability;
— corrosiveness;
— flashpoint and flammability;
— volatility;
— viscosity.
State that hydraulic fluids are irritating to skin and eyes.
List the two different types of hydraulic fluids:
— synthetic;
— mineral.
State that different types of hydraulic fluids cannot be mixed.
State that at the pressures being considered, hydraulic fluid is considered incompressible.
System components: design, operation, degraded modes of operation, indications and warnings
Explain the working principle of a hydraulic system.
Describe the difference in the principle of operation between a constant pressure system and a system pressurised only on specific demand.
State the differences in the principle of operation between a passive hydraulic system (without a pressure pump) and an active hydraulic system (with a pressure pump).
List the main advantages and disadvantages of system actuation by hydraulic or purely mechanical means with respect to:
— weight;
— size;
— force.
List the main uses of hydraulic systems.
State that hydraulic systems can be classified as either high pressure (typically 3000 psi or higher) or low pressure (typically up to 2000 psi).
State that a high-pressure hydraulic system is typically operating at 3000 psi but on some aircraft a hydraulic pressure of 4000 to 5000 psi may also be used.
Explain the working principle of a low-pressure (0–2000 psi) system.
Explain the advantages and disadvantages of a high-pressure system over a low-pressure system.
Describe the working principle and functions of pressure pumps including:
— constant pressure pump (swash plate or cam plate);
— pressure pump whose output is dependent on pump revolutions per minute (rpm) (gear type).
Explain the following different sources of hydraulic pressure, their typical application and potential operational limitations:
— manual;
— engine gearbox;
— electrical;
— air (pneumatic and ram-air turbine);
— hydraulic (power transfer unit) or reversible motor pumps;
— accessory.
Explain the following different sources of hydraulic pressure, their typical application and potential operational limitations:
— manual;
— engine;
— gearbox;
— electrical.
Describe the working principle and functions of the following hydraulic system components:
— reservoir (pressurised and unpressurised);
— accumulators;
— case drain lines and fluid cooler return lines;
— piston actuators (single- and double-acting);
— hydraulic motors;
— filters;
— non-return (check) valves;
— relief valves;
— restrictor valves;
— elector valves (linear and basic rotary selectors, two and four ports);
— bypass valves;
— shuttle valves;
— fire shut‑off valves;
— priority valves;
— fuse valves;
— pressure and return pipes.
Explain the function of the demand pump installed on many transport aeroplanes.
Explain how redundancy is obtained by giving examples.
Interpret a typical hydraulic system schematic to the level of detail as found in an aircraft flight crew operating manual (FCOM).
Explain the implication of a high system demand.
List and describe the instruments and alerts for monitoring a hydraulic system.
State the indications and explain the implications of the following malfunctions:
— system leak or low level;
— low pressure;
— high temperature.
LANDING GEAR, WHEELS, TYRES, BRAKES
Landing gear
Types
Name, for an aeroplane, the following different landing-gear configurations:
— nose wheel;
— tail wheel.
Name, for a helicopter, the following different landing‑gear configurations:
— nose wheel;
— tail wheel;
— skids.
System components, design, operation, indications and warnings, on-ground/in-flight protections, emergency extension systems
Explain the function of the following components of a landing gear:
— oleo leg/shock strut;
— axles;
— bogies and bogie beam;
— drag struts;
— side stays/struts;
— torsion links;
— locks (over centre);
— gear doors.
Explain the function of the following components of a landing gear:
— oleo leg/shock strut;
— axles;
— drag struts;
— side stays/struts;
— torsion links;
— locks (over centre);
— gear doors.
Name the different components of a landing gear, using a diagram.
Describe the sequence of events during normal operation of the landing gear.
State how landing-gear position indication and alerting is implemented.
Describe the various protection devices to avoid inadvertent gear retraction on the ground and explain the implications of taking off with one or more protection devices in place:
— ground lock (pins);
— protection devices in the gear retraction mechanism.
Explain the speed limitations for gear operation (VLO (maximum landing gear operating speed) and VLE (maximum landing gear extended speed)).
Describe the sequence for emergency gear extension:
— unlocking;
— operating;
— down-locking.
Describe some methods for emergency gear extension including:
— gravity/free fall;
— air or nitrogen pressure;
— manually/mechanically.
Nose-wheel steering
Design, operation
Explain the operating principle of nose‑wheel steering.
Explain, for a helicopter, the functioning of differential braking with free-castoring nose wheel.
Describe, for an aeroplane, the functioning of the following systems:
— differential braking with free-castoring nose wheel;
— tiller or hand wheel steering;
— rudder pedal nose-wheel steering.
Explain the centring mechanism of the nose wheel.
Define the term ‘shimmy’ and the possible consequences of shimmy for the nose- and the main‑wheel system and explain the purpose of a shimmy damper to reduce the severity of shimmy.
Explain the purpose of main-wheel (body) steering.
Brakes
Types and materials
Describe the basic operating principle of a disc brake.
State the different materials used in a disc brake (steel, carbon).
Describe the characteristics, advantages and disadvantages of steel and carbon brake discs with regard to:
— weight;
— temperature limits;
— internal-friction coefficient;
— wear.
System components, design, operation, indications and warnings
Explain the limitation of brake energy and describe the operational consequences.
Explain how brakes are actuated:
hydraulically,
electrically.
Explain the purpose of an in-flight wheel brake system.
Describe the function of a brake accumulator.
Describe the function of the parking brake.
Explain the function of brake-wear indicators.
Explain the reason for the brake-temperature indicator.
Anti-skid
Describe the operating principle of anti‑skid where excessive brake pressure applied is automatically reduced for optimum breaking performance.
Explain that the anti-skid computer compares wheel speed to aeroplane reference speed to provide the following:
— slip ratio for maximum braking performance;
— locked-wheel prevention (protection against deep skid on one wheel);
— touchdown protection (protection against brake-pressure application during touchdown);
— hydroplane protection.
Give examples of the impact of an anti-skid system on performance, and explain the implications of anti-skid system failure.
Autobrake
Describe the operating principle of an autobrake system.
Explain why the anti-skid system must be available when using autobrakes.
Explain the difference between the three modes of operation of an autobrake system:
— OFF (system off or reset);
— Armed (the system is ready to operate under certain conditions);
— Activated/Deactivated (application of pressure on brakes).
Describe how an autobrake system setting will either apply maximum braking (RTO or MAX) or result in a given rate of deceleration, where the amount of braking applied may be affected by:
— the use of reverse thrust;
— slippery runway.
Wheels, rims and tyres
Types, structural components and materials, operational limitations, thermal plugs
Describe the different types of tyres such as:
— tubeless;
— diagonal (cross ply);
— radial (circumferential bias).
Define the following terms:
— ply rating;
— tyre tread;
— tyre creep;
— retread (cover).
Explain the function of thermal/fusible plugs.
Explain the implications of and how to identify tread separation and wear or damage with associated increased risk of tyre burst.
Explain why the ground speed of tyres is limited.
Describe the following tyre checks a pilot will perform during the pre-flight inspection and identify probable causes:
— cuts and damages;
— flat spots.
Helicopter equipment
Flotation devices
Explain flotation devices, how they are operated, and their limitations.
Explain why indicated airspeed (IAS) limitations before, during and after flotation-device deployment must be observed.
FLIGHT CONTROLS
Aeroplane: primary flight controls
Definition and control surfaces
Define a ‘primary flight control’.
List the following primary flight control surfaces:
— elevator;
— aileron, roll spoilers, flaperon;
— rudder.
List the various means of control surface actuation including:
— manual;
— fully powered (irreversible);
— partially powered (reversible).
Manual controls
Explain the basic principle of a fully manual control system.
Fully powered controls (irreversible)
Explain the basic principle of a fully powered control system.
Explain the concept of irreversibility in a flight control system.
Explain the need for a ‘feel system’ in a fully powered control system.
Explain the operating principle of a stabiliser trim system in a fully powered control system.
Explain the operating principle of rudder and aileron trim in a fully powered control system.
Partially powered controls (reversible)
Explain the basic principle of a partially powered control system.
Explain why a ‘feel system’ is not necessary in a partially powered control system.
System components, design, operation, indications and warnings, degraded modes of operation, jamming
List and describe the function of the following components of a flight control system:
— actuators;
— control valves;
— cables;
— electrical wiring;
— control surface position sensors.
Explain how redundancy is obtained in primary flight control systems of large transport aeroplanes.
Explain the danger of control jamming and the means of retaining sufficient control capability.
Explain the methods of locking the controls on the ground and describe ‘gust or control lock’ warnings.
Explain the concept of a rudder deflection limitation (rudder limiter) system and the various means of implementation (rudder ratio changer, variable stops, blow-back).
Aeroplane: secondary flight controls
System components, design, operation, degraded modes of operation, indications and warnings
Define a ‘secondary flight control’.
List the following secondary flight control surfaces:
— lift-augmentation devices (flaps and slats);
— speed brakes;
— flight and ground spoilers;
— trimming devices such as trim tabs, trimmable horizontal stabiliser.
Describe secondary flight control actuation methods and sources of actuating power.
Explain the function of a mechanical lock when using hydraulic motors driving a screw jack.
Describe the requirement for limiting flight speeds for the various secondary flight control surfaces.
For lift-augmentation devices, explain the load-limiting (relief) protection devices and the functioning of an auto-retraction system.
Explain how a flap/slat asymmetry protection device functions, and describe the implications of a flap/slat asymmetry situation.
Describe the function of an auto-slat system.
Explain the concept of control surface blow-back (aerodynamic forces overruling hydraulic forces).
Helicopter: flight controls
Droop stops, control systems, trim systems, control stops
Explain the methods of locking the controls on the ground.
Describe main-rotor droop stops and how rotor flapping is restricted.
Explain the principle of phase lag and advance angle.
Describe the following four axes of control operation, their operating principle and their associated cockpit controls:
— collective control;
— cyclic fore and aft (pitch axis);
— cyclic lateral (roll axis);
— yaw.
Describe the swash plate or azimuth star control system including the following:
— swash plate inputs;
— the function of the non-rotating swash plate;
— the function of the rotating swash plate;
— how swash plate tilt is achieved;
— swash plate pitch axis;
— swash plate roll axis;
— balancing of pitch/roll/collective inputs to the swash plate to equalise torsional loads on the blades.
Describe the operation of the spider control system.
State the need for artificial feel in a hydraulically actuated flight control system.
Describe and explain the purpose of a trim system using the following terms:
— force-trim switch;
— force gradient;
— parallel trim actuator;
— cyclic 4-way trim switch;
— interaction of trim system with an SAS/SCAS/ASS stability system;
— trim-motor indicators.
Describe the different types of control runs.
Explain the use of control stops.
Aeroplane: fly-by-wire (FBW) control systems
Composition, explanation of operation, modes of operation
Explain that an FBW flight control system is composed of the following:
— pilot’s input command (control column/sidestick/rudder pedals);
— electrical signalling paths, including:
— pilot input to computer;
— computer to flight control surfaces;
— feedback from aircraft response to computer;
— flight control computers;
— actuators;
— flight control surfaces.
State the advantages of an FBW system in comparison with a conventional flight control system including:
— weight;
— pilot workload;
— flight-envelope protection.
Explain why an FBW system is always irreversible.
Explain the different modes of operation:
— normal operation (e.g. normal law or normal mode);
— downgraded operation (e.g. alternate law or secondary mode);
— direct law.
Describe the implications of mode degradation in relation to pilot workload and flight-envelope protection.
For aircraft using sidestick for manual control, describe the implications of:
— dual control input made by the pilot;
— the control takeover facility available to the pilot.
Explain why several types of computers are needed and why they should be dissimilar.
Explain why several control surfaces on every axis are needed on FBW aircraft.
Explain why several sensors are needed on critical parameters.
Helicopter: fly-by-wire (FBW) control systems
To be introduced at a later date.
PNEUMATICS — PRESSURISATION AND AIR‑CONDITIONING SYSTEMS
Pneumatic/bleed-air supply
Piston-engine air supply
Describe the following means of supplying air for the pneumatic systems for piston-engine aircraft:
— compressor;
— vacuum pump.
State that an air supply is required for the following systems:
— instrumentation;
— heating;
— de-icing.
Gas turbine engine: bleed-air supply
State that the possible bleed-air sources for gas turbine engine aircraft are the following:
— engine;
— auxiliary power unit (APU);
— ground supply.
State that for an aeroplane a bleed-air supply can be used for the following systems or components:
— ice protection;
— engine air starter;
— pressurisation of a hydraulic reservoir;
— air-driven hydraulic pumps;
— pressurisation and air conditioning.
State that for a helicopter a bleed-air supply can be used for the following systems or components:
— anti-icing;
— engine air starter;
— pressurisation of a hydraulic reservoir.
State that the bleed-air supply system can comprise the following:
— pneumatic ducts;
— isolation valve;
— pressure-regulating valve;
— engine bleed valve (HP/IP valves);
— fan-air pre-cooler;
— temperature and pressure sensors.
Interpret a basic pneumatic system schematic to the level of detail as found in an FCOM.
Describe the cockpit indications for bleed-air systems.
Explain how the bleed-air supply system is controlled and monitored.
State the following bleed-air malfunctions:
— over-temperature;
— over-pressure;
— low pressure;
— overheat/duct leak;
and describe the potential consequences.
Helicopter: air-conditioning systems
Types, system components, design, operation, degraded modes of operation, indications and warnings
Describe the purpose of an air-conditioning system.
Explain how an air-conditioning system is controlled.
Describe the vapour cycle air-conditioning system including system components, design, operation, degraded modes of operation and system malfunction indications.
Identify the following components from a diagram of an air-conditioning system and describe the operating principle and function:
— air-cycle machine (pack, bootstrap system);
— pack-cooling fan;
— water separator;
— mixing valves;
— flow-control valves;
— isolation valves;
— recirculation fans;
— filters for recirculation;
— temperature sensors.
List and describe the controls, indications and warnings related to an air-conditioning system.
Aeroplane: pressurisation and air-conditioning system
System components, design, operation, degraded modes of operation, indications and warnings
Explain that a pressurisation and an air-conditioning system of an aeroplane controls:
— ventilation;
— temperature;
— pressure.
Explain how humidity is controlled.
Explain that the following components constitute a pressurisation system:
— pneumatic system as the power source;
— outflow valve;
— outflow valve actuator;
— pressure controller;
— excessive differential pressure-relief valve;
— negative differential pressure-relief valve.
Explain that the following components constitute an air‑conditioning system and describe their operating principles and function:
— air-cycle machine (pack, bootstrap system);
— pack-cooling fan;
— water separator;
— mixing valves;
— flow-control valves (outflow valve);
— isolation valves;
— ram-air valve;
— recirculation fans;
— filters for recirculated air;
— temperature sensors.
Remark: The bootstrap system is the only air‑conditioning system considered for Part-FCL aeroplane examinations.
Describe the use of hot trim air.
Define the following terms:
— cabin altitude;
— cabin vertical speed;
— differential pressure;
— ground pressurisation.
Describe the operating principle of a pressurisation system.
Describe the emergency operation by manual setting of the outflow valve position.
Describe the working principle of an electronic cabin‑pressure controller.
State how the maximum operating altitude is determined.
Explain:
— why the maximum allowed value of cabin altitude is limited;
— a typical value of maximum differential pressure for large transport aeroplanes;
— the relation between cabin altitude, the maximum differential pressure and maximum aeroplane operating altitude.
Explain the typical warning on a transport category aircraft when cabin altitude exceeds 10000 ft.
List and interpret typical indications of the pressurisation system.
Describe the main operational differences between a bleed-air-driven air-conditioning system and an electrically driven air-conditioning system as found on aircraft without engine bleed-air system.
ANTI-ICING AND DE-ICING SYSTEMS
Types, operation, indications
Types, design, operation, indications and warnings, operational limitations
Explain the concepts of anti‑icing and de‑icing.
Name the components of an aircraft which can be protected from ice accretion.
State that on some aeroplanes the tail does not have an ice-protection system.
State the different types of anti-icing/de-icing systems and describe their operating principle:
— hot air;
— electrical;
— fluid.
Describe the operating principle of the inflatable boot de-icing system.
Ice warning systems
Types, operation, and indications
Describe the different operating principles of the following ice detectors:
— mechanical systems using air pressure;
— electromechanical systems using resonance frequencies.
Describe the principle of operation of ice warning systems.
Helicopter blade heating systems
Limitations
Explain the limitations on blade heating and the fact that on some helicopters the heating does not heat all the main-rotor blades at the same time.
FUEL SYSTEM
Piston engine
Fuel: types, characteristics, limitations
State the types of fuel used by a piston engine and their associated limitations:
— diesel;
— JET-A1 (for high-compression engines);
— AVGAS;
— MOGAS.
State the main characteristics of these fuels and give typical values regarding their flash points, freezing points and density.
Design, operation, system components, indications
State the tasks of the fuel system.
Name the following main components of a fuel system, and state their location and their function:
— lines;
— boost pump;
— pressure valves;
— filter, strainer;
— tanks (wing, tip, fuselage);
— vent system;
— sump;
— drain;
— fuel-quantity sensor;
— fuel-temperature sensor.
Describe a gravity fuel feed system and a pressure feed fuel system.
Describe the construction of the different types of fuel tanks and state their advantages and disadvantages:
— drum tank;
— bladder tank;
— integral tank.
Explain the function of cross-feed.
Define the term ‘unusable fuel’.
List the following parameters that are monitored for the fuel system:
— fuel quantity (low-level warning);
— fuel temperature.
Turbine engine
Fuel: types, characteristics, limitations
State the types of fuel used by a gas turbine engine:
— JET-A;
— JET-A1;
— JET-B.
State the main characteristics of these fuels and give typical values regarding their flash points, freezing points and density.
State the existence of additives for freezing.
Design, operation, system components, indications
Explain the function of the fuel system:
— lines;
— centrifugal boost pump;
— pressure valves;
— fuel shut-off valve;
— filter, strainer;
— tanks (wing, tip, fuselage, tail);
— bafflers/baffles;
— sump;
— vent system;
— drain;
— fuel-quantity sensor;
— fuel-temperature sensor;
— refuelling/defueling system;
— fuel dump/jettison system.
Name the main components of the fuel system and state their location and their function:
— trim fuel tanks;
— bafflers;
— refuelling/defueling system;
— fuel dump/jettison system.
Interpret a typical fuel system schematic to the level of detail as found in an aircraft FCOM.
Explain the limitations in the event of loss of booster pump fuel pressure.
Describe the use and purpose of drip sticks (manual magnetic indicators) (may also be known as dip stick or drop stick).
Explain the considerations for fitting a fuel dump/jettison system and, if fitted, its function.
ELECTRICS
Remark: For any reference to the direction of current flow, the conventional current flow shall be used, i.e. from positive to negative.
General, definitions, basic applications: circuit breakers, logic circuits
Static electricity
Explain static electricity and describe the flying conditions where aircraft are most susceptible to build-up of static electricity.
Describe a static discharger and explain the following:
— its purpose;
— typical locations;
— pilot’s role of observing it during pre-flight inspection.
Explain why an aircraft must first be grounded before refuelling/defueling.
Explain the reason for electrical bonding.
Direct current (DC)
Explain the term ‘direct current’ (DC), and state that current can only flow in a closed circuit.
Explain the basic principles of conductivity and give examples of conductors, semiconductors and insulators.
Describe the difference in use of the following mechanical switches and explain the difference in observing their state (e.g. ON/OFF), and why some switches are guarded:
— toggle switch;
— rocker switch;
— pushbutton switch;
— rotary switch.
Explain the difference in observing their state (e.g. ON/OFF) and why some switches are guarded.
Define voltage and current, and state their unit of measurement.
Explain Ohm’s law in qualitative terms.
Explain the effect on total resistance when resistors are connected in series or in parallel.
State that resistances can have a positive or a negative temperature coefficient (PTC/NTC) and state their use.
Define electrical power and state the unit of measurement.
Alternating current (AC)
Explain the term ‘alternating current’ (AC), and compare its use to DC with regard to complexity.
Define the term ‘phase’, and explain the basic principle of single-phase and three-phase AC.
State that aircraft can use single-phase or three-phase AC.
Define frequency and state the unit of measurement.
Define ‘phase shift’ in qualitative terms.
Electromagnetism
State that an electrical current produces a magnetic field.
Describe how the strength of the magnetic field changes with the magnitude of the current.
Explain the purpose and the working principle of a solenoid.
Explain the purpose and the working principle of a relay.
Explain the principle of electromagnetic induction and how two electrical components or systems may affect each other through this principle.
Circuit protection
Explain the working principle of a fuse and a circuit breaker.
Explain how a fuse is rated.
Describe the principal difference between the following types of circuit breakers:
— thermal circuit breaker sensing magnitude of current;
— magnetic circuit breaker sensing direction of current.
Describe how circuit breakers may be used to reset aircraft systems/computers in the event of system failure (when part of a described procedure).
Explain a short circuit in practical terms using Ohm’s Law, power and energy expressions highlighting the risk of fire due to power transfer and extreme energy dissipation.
Explain the risk of fire resulting from excessive heat in a circuit subjected to overcurrent.
Explain that overcurrent situations may be transient.
Explain the hazards of multiple resets of a circuit breaker or the use of incorrect fuse rating when replacing blown fuses.
Semiconductors and logic circuits
Describe the effect of temperature on semiconductors with regard to function and longevity of the component.
Describe the following five basic logic functions, as used in aircraft FCOM documentation, and recognise their schematic symbols according to the ANSI/MIL standard:
— AND;
— OR;
— NOT;
— NOR;
— NAND.
Interpret a typical logic circuit schematic to the level of detail as found in an aircraft FCOM.
Batteries
Types, characteristics and limitations
State the function of an aircraft battery.
Name the types of rechargeable batteries used in aircraft:
— lead-acid;
— nickel-cadmium;
— lithium-ion;
— lithium-polymer.
Compare the different battery types with respect to:
— load behaviour;
— charging characteristics;
— risk of thermal runaway.
Explain the term ‘cell voltage’ and describe how a battery may consist of several cells that combined provide the desirable voltage and capacity.
Explain the difference between battery voltage and charging voltage.
Define the term ‘capacity of batteries’ and state the unit of measurement used.
State the effect of temperature on battery capacity and performance.
State that in the case of loss of all generated power (battery power only) the remaining electrical power is time-limited.
Explain how lithium-type batteries pose a threat to aircraft safety and what affects this risk:
— numbers of batteries on board an aircraft including those brought on board by passengers;
— temperature, of both battery and environment;
— physical condition of the battery;
— battery charging.
Describe how to contain a battery thermal runaway highlighting the following:
— how one cell can affect the neighbouring cells;
— challenges if it happens in an aircraft during flight.
Generation
Remark: For standardisation purposes, the following standard expressions are used:
— DC generator: produces DC output;
— DC alternator: produces AC, rectified by integrated rectifying unit, the output is DC;
— DC alternator: producing a DC output by using a rectifier;
— AC generator: produces AC output;
— starter generator: integrated combination of a generator and a starter motor;
— permanent magnet alternator/ generator: self-exciting AC generator.
DC generation
Describe the basic working principle of a simple DC generator or DC alternator.
Explain the principle of voltage control and why it is required.
Explain the purpose of reverse current protection from the battery/busbar to the alternator.
Describe the basic operating principle of a starter generator and state its purpose.
AC generation
Describe the working principle of a brushless three‑phase AC generator.
State that the generator field current is used to control voltage.
State the relationship between output frequency and the rpm of a three-phase AC generator.
Explain the term ‘frequency wild generator’.
List the following different power sources that can be used for an aeroplane to drive an AC generator:
— engine;
— APU;
— RAT;
— hydraulic.
List the following different power sources that can be used for a helicopter to drive an AC generator:
— engine;
— APU;
— gearbox.
Constant speed drive (CSD) and integrated drive generator (IDG) systems
Describe the function of a CSD.
Explain the parameters of a CSD that are monitored.
Describe the function of an IDG.
Explain the consequences of a mechanical disconnection during flight for a CSD and an IDG.
Explain that a CSD/IDG has its own, independent oil system and how a leak from this may appear as an engine oil leak.
Transformers, transformer rectifier units (TRUs), static inverters
State the function of a transformer.
State the function of a TRU and its purpose, including type of output.
State the function of a static inverter and its purpose, including type of output.
Distribution
General
Explain the function of a busbar.
Describe the function of the following buses:
— AC bus;
— DC bus;
— emergency AC or DC bus;
— essential AC or DC bus;
— battery bus;
— hot bus, ground servicing or maintenance bus.
State that the aircraft structure can be used as a part of the electrical circuit (common earth) and explain the implications for electrical bonding.
Explain the function of external power.
State that a priority sequence exists between the different sources of electrical power on ground and in flight.
Explain the term ‘load sharing’.
Explain the term ‘load shedding’.
Describe typical systems that can be shed in the event of a supply failure, such as passenger entertainment system and galley power.
Interpret a typical electrical system schematic to the level of detail as found in an aircraft FCOM.
Explain the difference between a supply (e.g. generator) failure and a bus failure, and the operating consequences of either.
DC distribution
Describe a simple DC electrical system of a single-engine aircraft.
Describe a DC electrical system of a multi-engine aircraft (CS-23/CS-27) including the distribution consequences of loss of generator(s) or bus failure.
Describe the DC part of an electrical system of a transport aircraft (CS-25/CS-29) including the distribution consequences of loss of DC supply or bus failure.
Give examples of DC consumers.
AC distribution
Explain the difference in the principle of operation for a split AC electrical system and a parallel AC electrical system.
Describe the following distribution consequences:
— power transfer between different power supplies;
— power transfer in the event of a supply failure;
— loss of all normal AC supplies.
Give examples of AC consumers.
Explain the conditions to be met for paralleling AC generators.
State that volt-ampere (VA) is the unit for total power consumed in an AC system.
Electrical load management and monitoring systems: automatic generators and bus switching during normal and failure operation, indications and warnings
Give examples of system control, monitoring and annunciators using the following terms:
— generator control unit (GCU) for monitoring generator output and providing network protection;
— exciter contactor/breaker/relay for control of generator exciter field;
— generator contactor/breaker/relay for connecting the generator to the network;
— bus-tie contactor/breaker/relay for connecting busbars together;
— generator switch on the flight deck for manual control of exciter contactor;
— IDG/CSD disconnect switch on the flight deck for mechanical disconnection of the generator;
— bus-tie switch on the flight deck with AUTO and OFF positions only.
Describe, for normal and degraded modes of operation, the following functions of an electrical load management system on ground and in flight using the terms:
— distribution;
— monitoring;
— protection in the event of incorrect voltage;
— protection in the event of incorrect frequency;
— protection in the event of a differential fault.
Describe the requirement for monitoring the aircraft batteries.
Explain the importance of monitoring the temperature of nickel-cadmium and lithium-type batteries.
Interpret various different ammeter indications of an ammeter which monitors the charge current of the battery.
Electrical motors
General
State that the purpose of an electrical motor is to convert electrical energy into mechanical energy.
State that because of the similarity in design, a generator and an electrical motor may be combined into a starter generator.
Explain that the size of the engine determines how much energy is required for starting, and state the following:
— small turbine engines may be able to use the battery for a very limited number of start attempts;
— large turbine engines require one or more power sources, either external or on-board.
Operating principle
Describe how the torque of an electrical motor is determined by the supplied voltage and current, and the resulting magnetic fields within the motor.
State that electrical motors can be either AC or DC.
Explain the consequences of the following:
— rotor seizure;
— rotor runaway.
Components
Name the following components of an electrical motor:
— rotor (rotating part of an electrical motor);
— stator (stationary part of an electrical motor).
PISTON ENGINES
Remark: This topic includes diesel and petrol engines.
General
Types of internal-combustion engines: basic principles, definitions
Define the following terms and expressions:
— rpm;
— torque;
— manifold absolute pressure (MAP);
— power output;
— specific fuel consumption;
— compression ratio, clearance volume, swept (displaced) volume, total volume.
Engine: design, operation, components
Describe the basic operating principle of a piston engine:
— crankcase;
— crankshaft;
— connecting rod;
— piston;
— piston pin;
— piston rings;
— cylinder;
— cylinder head;
— valves;
— valve springs;
— push rod;
— camshaft;
— rocker arm;
— camshaft gear;
— bearings.
Name and identify the various types of engine design with regard to cylinder arrangement and their advantages/disadvantages:
— horizontally opposed;
— in line;
— radial; and
— working cycle (four stroke: petrol and diesel).
Describe the differences between petrol and diesel engines with respect to:
— means of ignition;
— maximum compression ratio;
— regulating air or mixture supply to the cylinder;
— pollution from the exhaust.
Fuel
Types, grades, characteristics, limitations
Name the type of fuel used for petrol engines including its colour (AVGAS);
— 100 (green);
— 100LL (blue).
Name the type of fuel normally used for aviation diesel engines (JET-A1).
Define the term ‘octane rating’.
Define the term ‘detonation’ and describe the causes and effects of detonation for both petrol and diesel engines.
Define the term ‘pre-ignition’ and describe the causes and effects of pre-ignition for both petrol and diesel engines.
Identify the conditions and power settings that promote detonation for petrol engines.
Describe how detonation in petrol engines is recognised.
Describe the method and occasions for checking the fuel for water content.
State the typical value of fuel density for aviation gasoline and diesel fuel.
Explain volatility, viscosity and vapour locking for petrol and diesel fuels.
Engine fuel pumps
Engine-driven fuel pump
Explain the need for a separate engine-driven fuel pump.
Carburettor/injection system
Carburettor: design, operation, degraded modes of operation, indications and warnings
State the purpose of a carburettor.
Describe the operating principle of the simple float chamber carburettor.
Describe the methods of obtaining mixture control over the whole operating engine power setting range (compensation jet, diffuser).
Describe the methods of obtaining mixture control over the whole operating altitude range.
Explain the purpose and the operating principle of an accelerator pump.
Explain the purpose of power enrichment.
Describe the function of the carburettor heat system.
Explain the effect of carburettor heat on mixture ratio and power output.
Explain the purpose and the operating principle of a primer pump.
Discuss other methods for priming an engine (acceleration pumps).
Explain the danger of carburettor fire, including corrective measures.
Injection: design, operation, degraded modes of operation, indications and warnings
Explain the advantages and difference in operation of an injection system compared with a carburettor system.
Icing
Describe the causes and effects of carburettor icing and the action to be taken if carburettor icing is suspected.
Name the meteorological conditions under which carburettor icing may occur.
Describe the indications of the presence of carburettor icing for both a fixed pitch and a constant speed propeller.
Describe the indications of the presence of carburettor icing for a helicopter.
Describe the indications that will occur upon selection of carburettor heat depending on whether ice is present or not.
Explain the reason for the use of alternate air on fuel injection systems and describe its operating principle.
State the meteorological conditions under which induction system icing may occur.
Cooling systems
Design, operation, indications and warnings
Specify the reasons for cooling a piston engine.
Describe the design features to enhance cylinder air cooling for aeroplanes.
Describe the design features to enhance cylinder air cooling for helicopters (e.g. engine-driven impeller and scroll assembly, baffles).
Compare the differences between liquid- and air‑cooling systems.
Identify the cylinder head temperature indication to monitor engine cooling.
Describe the function and the operation of cowl flaps.
Lubrication systems
Lubricants: characteristics, limitations
Describe the term ‘viscosity’ including the effect of temperature.
Describe the viscosity grade numbering system used in aviation.
Design, operation, indications and warnings
State the functions of a piston-engine lubrication system.
Describe the working principle of a dry-sump lubrication system and describe the functions of the following components:
— oil tank (reservoir) and its internal components: hot well, de-aerator, vent, expansion space;
— check valve (non-return valve);
— pressure pump and pressure-relief valve;
— scavenge pump;
— filters (suction, pressure and scavenge);
— oil cooler;
— oil cooler bypass valve (anti-surge and thermostatic);
— pressure and temperature sensors;
— lines.
Describe a wet-sump lubrication system.
State the differences between a wet- and a dry-sump lubrication system and their advantages and disadvantages.
List the following factors that influence oil consumption:
— oil grade;
— cylinder and piston wear;
— condition of piston rings.
Describe the interaction between oil pressure, oil temperature and oil quantity.
Ignition circuits
Design, operation
Describe the working principle of a magneto-ignition system and the functions of the following components:
— magneto;
— contact-breaker points;
— capacitor (condenser);
— coils or windings;
— ignition switches;
— distributor;
— spark plug;
— high-tension (HT) cable.
State why piston engines are equipped with two electrically independent ignition systems.
State the function and operating principle of the following methods of spark augmentation:
— starter vibrator (booster coil);
— impulse-start coupling.
State the function and operating principle of the following methods of spark augmentation:
— starter vibrator (booster coil);
— both magnetos live.
Explain the function of the magneto check.
Explain how combustion is initiated in diesel engines.
Mixture
Definition, characteristic mixtures, control instruments, associated control levers, indications
Define the following terms:
— mixture;
— chemically correct ratio (stoichiometric);
— best power ratio;
— lean (weak) mixture (lean or rich side of the exhaust gas temperature (EGT) top);
— rich mixture.
State the typical fuel-to-air ratio values or range of values for the above mixtures.
Describe the advantages and disadvantages of weak and rich mixtures.
Describe the relation between engine-specific fuel consumption and mixture ratio.
Describe the use of the exhaust gas temperature as an aid to mixture-setting.
Explain the relation between mixture ratio, cylinder head temperature, detonation and pre-ignition.
Explain the absence of mixture control in diesel engines.
Aeroplane: propellers
Definitions, general
Remark: Definitions and aerodynamic concepts are detailed in Subject ‘Principles of flight (aeroplane)’, Topic – Propellers, but need to be appreciated for this Subject as well.
Constant-speed propeller: design, operation, system components
Describe the operating principle of a constant-speed propeller system under normal flight operations with the aid of a schematic.
Explain the need for a MAP indicator to control the power setting with a constant-speed propeller.
State the purpose of a torque-meter.
State the purpose and describe the operation of a low‑pitch stop (centrifugal latch).
Describe the operating principle of a single-acting and a double-acting variable pitch propeller for single- and multi-engine aeroplanes.
Describe the function and the basic operating principle of synchronising and synchro-phasing systems.
Explain the purpose and the basic operating principle of an auto-feathering system and unfeathering.
Reduction gearing: design
State the purpose of reduction gearing.
Propeller handling: associated control levers, degraded modes of operation, indications and warnings
Describe the checks to be carried out on a constant‑speed propeller system after engine start.
Describe the operation of a constant-speed propeller system during flight at different true airspeeds (TAS) and rpm including an overspeeding propeller.
Describe the operating principle of a variable pitch propeller when feathering and unfeathering, including the operation of cockpit controls.
Describe the operating principle of a variable pitch propeller when reverse pitch is selected, including the operation of cockpit controls.
Describe the operation of the propeller levers during different phases of flight.
Performance and engine handling
Performance
Describe the effect on power output of a petrol and diesel engine taking into consideration the following parameters:
— ambient pressure, exhaust back pressure;
— temperature;
— density altitude;
— humidity.
Explain the term ‘normally aspirated engine’.
Power-augmentation devices: explain the requirement for power augmentation (turbocharging) of a piston engine.
Describe the function and the principle of operation of the following main components of a turbocharger:
— turbine;
— compressor;
— waste gate;
— waste-gate actuator.
Explain the difference between an altitude-boosted turbocharger and a ground-boosted turbocharger.
Explain turbo lag.
Define the term ‘critical altitude’.
Explain the function of an intercooler.
Define the terms ‘full-throttle height’ and ‘rated altitude’.
Explain the purpose of a supercharger and the basic differences from a turbocharger.
Engine handling
State the correct procedures for setting the engine controls when increasing or decreasing power.
Define the following terms:
— take-off power;
— maximum continuous power.
Describe the start problems associated with extreme cold weather.
Describe the principal difference between a full‑authority digital engine control (FADEC) system‑controlled engine and traditional manual engine controls.
Describe the engine controls available on the flight deck for a FADEC-controlled engine.
Explain that the FADEC has full authority of the control of all engine parameters ensuring efficient and correct running of the engine, including protection in the event of failure.
Explain the need for FADEC redundancy with regard to power supply and data input and output.
TURBINE ENGINES
Basic principles
Basic generation of thrust and the thrust formula
Describe how thrust is produced by a basic gas turbine engine.
Describe the simple form of the thrust formula for a basic, straight jet engine and perform simple calculations (including pressure thrust).
State that thrust can be considered to remain approximately constant over the whole aeroplane subsonic speed range.
Design, types and components of turbine engines
List the main components of a basic gas turbine engine:
— inlet;
— compressor;
— combustion chamber;
— turbine;
— outlet.
Describe the variation of static pressure, temperature and axial velocity in a gas turbine engine under normal operating conditions and with the aid of a working cycle diagram.
Describe the differences between absolute, circumferential (tangential) and axial velocity.
List the different types of gas turbine engines:
— straight jet;
— turbofan;
— turboprop.
State that a gas turbine engine can have one or more spools.
Describe how thrust is produced by turbojet and turbofan engines.
Describe how power is produced by turboprop engines.
Describe the term ‘equivalent horsepower’ (= thrust horsepower + shaft horsepower).
Explain the principle of a free turbine or free-power turbine.
Define the term ‘bypass ratio’ and perform simple calculations to determine it.
Define the terms ‘propulsive power’, ‘propulsive efficiency’, ‘thermal efficiency’ and ‘total efficiency’.
Describe the influence of compressor-pressure ratio on thermal efficiency.
Explain the variations of propulsive efficiency with forward speed for turbojet, turbofan and turboprop engines.
Define the term ‘specific fuel consumption’ for turbojets and turboprops.
Coupled turbine engine: design, operation, components and materials
Name the main assembly parts of a coupled turbine engine and explain its operation.
Explain the limitations of the materials used with regard to maximum turbine temperature, engine and drive train torque limits.
Describe the possible effects on engine components when limits are exceeded.
Explain that when engine limits are exceeded, this event must be reported.
Free-turbine engine: design, components and materials
Describe the design methods to keep the engine’s size small for installation in helicopters.
List the main components of a free-turbine engine.
Describe how the power is developed by a turboshaft/free-turbine engine.
Explain how the exhaust gas temperature is used to monitor turbine stress.
Main-engine components
Aeroplane: air intake
State the functions of the engine air inlet/air intake.
Describe the geometry of a subsonic (pitot-type) air inlet.
Explain the gas-parameter changes in a subsonic air inlet at different flight speeds.
Describe the reasons for, and the dangers of, the following operational problems concerning the engine air inlet:
— airflow separation;
— inlet icing;
— inlet damage;
— foreign object damage (FOD);
— heavy in-flight turbulence.
Compressor and diffuser
State the purpose of the compressor.
Describe the working principle of a centrifugal and an axial flow compressor.
Name the following main components of a single stage and describe their function for a centrifugal compressor:
— impeller;
— diffuser.
Name the following main components of a single stage and describe their function for an axial compressor:
— rotor vanes;
— stator vanes.
Describe the gas-parameter changes in a compressor stage.
Define the term ‘pressure ratio’ and state a typical value for one stage of a centrifugal and an axial flow compressor and for the complete compressor.
State the advantages and disadvantages of increasing the number of stages in a centrifugal compressor.
Explain the difference in sensitivity for FOD of a centrifugal compressor compared with an axial flow type.
Explain the convergent air annulus through an axial flow compressor.
Describe the reason for twisting the compressor blades.
State the tasks of inlet guide vanes (IGVs).
State the reason for the clicking noise whilst the compressor slowly rotates on the ground.
State the advantages of increasing the number of spools.
Explain the implications of tip losses and describe the design features to minimise the problem.
Explain the problems of blade bending and flapping and describe the design features to minimise the problem.
Explain the following terms:
— compressor stall;
— engine surge.
State the conditions that are possible causes of stall and surge.
Describe the indications of stall and surge.
Describe the design features used to minimise the occurrence of stall and surge.
Describe a compressor map (surge envelope) with rpm lines, stall limit, steady state line and acceleration line.
Describe the function of the diffuser.
Combustion chamber
Define the purpose of the combustion chamber.
List the requirements for combustion.
Describe the working principle of a combustion chamber.
Explain the reason for reducing the airflow axial velocity at the combustion chamber inlet (snout).
State the function of the swirl vanes (swirler).
State the function of the drain valves.
Define the terms ‘primary airflow’ and ‘secondary airflow’, and explain their purpose.
Explain the following two mixture ratios:
— primary airflow to fuel;
— total airflow (within the combustion chamber) to fuel.
Describe the gas-parameter changes in the combustion chamber.
State a typical maximum value of the outlet temperature of the combustion chamber.
Describe the following types of combustion chambers and state the differences between them:
— can type;
— can-annular, cannular or turbo-annular;
— annular;
— reverse-flow annular.
Turbine
Explain the purpose of a turbine in different types of gas turbine engines.
Describe the principles of operation of impulse, reaction and impulse-reaction axial flow turbines.
Name the main components of a turbine stage and their function.
Describe the working principle of a turbine.
Describe the gas-parameter changes in a turbine stage.
Describe the function and the working principle of active clearance control.
Describe the implications of tip losses and the means to minimise them.
Explain why the available engine thrust is limited by the turbine inlet temperature.
Explain the divergent gas-flow annulus through an axial-flow turbine.
Explain the high mechanical thermal stress in the turbine blades and wheels/discs.
Aeroplane: exhaust
Name the following main components of the exhaust unit and their function:
— jet pipe;
— propelling nozzle;
— exhaust cone.
Describe the working principle of the exhaust unit.
Describe the gas-parameter changes in the exhaust unit.
Define the term ‘choked exhaust nozzle’ (not applicable to turboprops).
Explain how jet exhaust noise can be reduced.
Helicopter: air intake
Name and explain the main task of the engine air intake.
Describe the use of a convergent air-intake ducting on helicopters.
Describe the reasons for and the dangers of the following operational problems concerning engine air intake:
— airflow separations;
— intake icing;
— intake damage;
— FOD;
— heavy in-flight turbulence.
Describe the conditions and circumstances during ground operations when FOD is most likely to occur.
Describe and explain the principles of air intake filter systems that can be fitted to some helicopters for operations in icing and sand conditions.
Describe the function of the heated pads on some helicopter air intakes.
Helicopter: exhaust
Describe the working principle of the exhaust unit.
Describe the gas-parameter changes in the exhaust unit.
Additional components and systems
Engine fuel system
Name the main components of the engine fuel system and state their function:
— filters;
— low-pressure (LP) pump;
— high-pressure (HP) pump;
— fuel manifold;
— fuel nozzles;
— HP fuel cock;
— fuel control; or
— hydromechanical unit.
Name the two types of engine-driven high-pressure pumps, such as:
— gear-type;
— swash plate-type.
State the tasks of the fuel control unit.
List the possible input parameters to a fuel control unit to achieve a given thrust/power setting.
Engine control system
State the tasks of the engine control system.
List the following different types of engine control systems:
— hydromechanical;
— hydromechanical with a limited authority electronic supervisor;
— single-channel FADEC with hydromechanical backup;
— dual-channel FADEC with no backup or any other combination.
Describe a FADEC as a full-authority dual-channel system including functions such as an electronic engine control unit, wiring, sensors, variable vanes, active clearance control, bleed configuration, electrical signalling of thrust lever angle (TLA) (see also AMC to CS-E-50), and an EGT protection function and engine overspeed.
Explain how redundancy is achieved by using more than one channel in a FADEC system.
State the consequences of a FADEC single input data failure.
State that all input and output data is checked by both channels in a FADEC system.
State that a FADEC system uses its own sensors and that, in some cases, also data from aircraft systems is used.
State that a FADEC must have its own source of electrical power.
Engine lubrication
State the tasks of an engine lubrication system.
Name the following main components of a lubrication system and state their function:
— oil tank and centrifugal breather;
— oil pumps (pressure and scavenge pumps);
— oil filters (including the bypass);
— oil sumps;
— chip detectors;
— coolers.
Explain that each spool is fitted with at least one ball bearing and two or more roller bearings.
Explain the use of compressor air in oil-sealing systems (e.g. labyrinth seals).
Engine auxiliary gearbox
State the tasks of the auxiliary gearbox.
Describe how the gearbox is driven and lubricated.
Engine ignition
State the task of the ignition system.
Name the following main components of the ignition system and state their function:
— power sources;
— igniters.
State why jet turbine engines are equipped with two electrically independent ignition systems.
Explain the different modes of operation of the ignition system.
Engine starter
Name the main components of the starting system and state their function.
Explain the principle of a turbine engine start.
Describe the following two types of starters:
— electric;
— pneumatic.
Describe a typical start sequence (on ground/in flight) for a turbofan.
Define ‘self-sustaining rpm’.
Reverse thrust
Name the following main components of a reverse-thrust system and state their function:
— reverse-thrust select lever;
— power source (pneumatic or hydraulic);
— actuators;
— doors;
— annunciations.
Explain the principle of a reverse-thrust system.
Identify the advantages and disadvantages of using reverse thrust.
Describe and explain the following different types of thrust-reverser systems:
— hot-stream reverser;
— clamshell or bucket-door system;
— cold-stream reverser (only turbofan engines);
— blocker doors;
— cascade vanes.
Explain the implications of reversing the cold stream (fan reverser) only on a high bypass ratio engine.
Describe the protection features against inadvertent thrust-reverse deployment in flight as present on most transport aeroplanes.
Describe the controls and indications provided for the thrust-reverser system.
Helicopter specifics on design, operation and components for additional components and systems such as lubrication system, ignition circuit, starter, accessory gearbox
State the task of the lubrication system.
List and describe the common helicopter lubrication systems.
Name the following main components of a helicopter lubrication system:
— reservoir;
— pump assembly;
— external oil filter;
— magnetic chip detectors, electronic chip detectors;
— thermostatic oil coolers;
— breather.
Identify and name the components of a helicopter lubrication system from a diagram.
Identify the indications used to monitor a lubrication system including warning systems.
Explain the differences and appropriate use of straight oil and compound oil, and describe the oil numbering system for aviation use.
Explain and describe the ignition circuit for engine start and engine relight facility when the selection is set for both automatic and manual functions.
Explain and describe the starter motor and the sequence of events when starting, and that for most helicopters the starter becomes the generator after the starting sequence is over.
Explain and describe why the engine drives the accessory gearbox.
Engine operation and monitoring
General
Explain the following aeroplane engine ratings:
— take-off;
— go-around;
— maximum continuous thrust/power;
— maximum climb thrust/power.
Explain spool-up time.
Explain the reason for the difference between ground and approach flight idle values (rpm).
State the parameters that can be used for setting and monitoring the thrust/power.
Describe the terms ‘alpha range’, ‘beta range’ and ‘reverse thrust’ as applied to a turboprop power lever.
Explain the dangers of inadvertent beta-range selection in flight for a turboprop.
Explain the purpose of engine trending.
Explain how the exhaust gas temperature is used to monitor turbine stress.
Describe the effect of engine acceleration and deceleration on the EGT.
Describe the possible effects on engine components when EGT limits are exceeded.
Explain why engine-limit exceedances must be reported.
Explain the limitations on the use of the thrust-reverser system at low forward speed.
Explain the term ‘engine seizure’.
State the possible causes of engine seizure and explain their preventative measures.
Describe the potential consequences of a leak in the following two designs of fuel and oil heat exchanger:
— oil pressure higher than fuel pressure with oil leaking into the fuel system, potentially affecting the combustion and running of the engine;
— fuel pressure higher than oil pressure with fuel leaking into the oil system, potentially increasing the risk of a fire due to fuel entering warm parts of the engine that should be free from fuel.
Explain oil-filter clogging (blockage) and the implications for the lubrication system.
Give examples of monitoring instruments of an engine.
Describe how to identify and assess engine damage based on instrument indications.
Starting malfunctions
Describe the indications and the possible causes of the following aeroplane starting malfunctions:
— false (dry or wet) start;
— tailpipe fire (torching);
— hot start;
— abortive (hung) start;
— no N1 rotation;
— no FADEC indications.
Describe the indications and the possible causes of the following helicopter starting malfunctions:
— false (dry or wet) start;
— tailpipe fire (torching);
— hot start;
— abortive (hung) start;
— no N1 rotation;
— freewheel failure;
— no FADEC indications.
Relight envelope
Explain the relight envelope.
Performance aspects
Thrust, performance aspects, and limitations
Describe the variation of thrust and specific fuel consumption with altitude at constant TAS.
Describe the variation of thrust and specific fuel consumption with TAS at constant altitude.
Explain the term ‘flat-rated engine’ by describing the change of take-off thrust, turbine inlet temperature and engine rpm with outside air temperature (OAT).
Define the term ‘engine pressure ratio’ (EPR).
Explain the use of reduced (flexible) and derated thrust for take-off, and explain the advantages and disadvantages when compared with a full-rated take‑off.
Describe the effects of use of bleed air on rpm, EGT, thrust, and specific fuel consumption.
Helicopter engine ratings, engine performance and limitations, engine handling: torque, performance aspects and limitations
Describe engine rating torque limits for take-off, transient and maximum continuous.
Describe turbine outlet temperature (TOT) limits for take-off.
Explain why TOT is a limiting factor for helicopter performance.
Describe and explain the relationship between maximum torque available and density altitude, which leads to decreasing torque available with the increase of density altitude.
Explain that hovering downwind, on some helicopters, will noticeably increase the engine TOT.
Explain the reason why the engine performance is less when aircraft accessories (i.e. anti-ice, heating, hoist, filters) are switched on.
Describe the effects of use of bleed air on engine parameters.
Explain that, on some helicopters, exceeding the TOT limit may cause the main rotor to droop (slow down).
Describe overtorquing and explain the consequences.
Auxiliary power unit (APU)
Design, operation, functions, operational limitations
State that an APU is a gas turbine engine and list its tasks.
State the difference between the two types of APU inlets.
Define ‘maximum operating and maximum starting altitude’.
Name the typical APU control and monitoring instruments.
Describe the APU’s automatic shutdown protection.
PROTECTION AND DETECTION SYSTEMS
Smoke detection
Types, design, operation, indications and warnings
Explain the operating principle of the following types of smoke detection sensors:
— optical;
— ionising.
Give an example of warnings, indications and function tests.
Fire-protection systems
Fire extinguishing (engine and cargo compartments)
Explain the operating principle of a built-in fire‑extinguishing system and describe its components.
State that two discharges must be provided for each engine (see CS 25.1195(c) Fire-extinguisher systems).
Fire detection
Explain the following principles of fire detection:
— resistance and capacitance;
— gas pressure.
Explain fire-detection applications such as:
— bimetallic;
— continuous loop;
— gaseous loop (gas-filled detectors).
Explain why generally double-loop systems are used.
Give an example of warnings, indications and function tests of a fire-protection system.
Rain-protection system
Principle and method of operation
Explain the principle and method of operation of the following windshield rain-protection systems for an aeroplane:
— wipers;
— liquids (rain-repellent);
— coating.
Explain the principle and method of operation of wipers for a helicopter.
OXYGEN SYSTEMS
Cockpit, portable and chemical oxygen systems
Operating principles, actuation methods, comparison
Describe the basic operating principle of a cockpit oxygen system and describe the following different modes of operation:
— normal (diluter demand);
— 100 %;
— emergency.
Describe the operating principle and the purposes of the following two portable oxygen systems:
— smoke hood;
— portable bottle.
Describe the following two oxygen systems that can be used to supply oxygen to passengers:
— fixed system (chemical oxygen generator or gaseous system);
— portable.
Describe the actuation methods (automatic and manual) and the functioning of a passenger oxygen mask.
Compare chemical oxygen generators to gaseous systems with respect to:
— capacity;
— flow regulation.
State the dangers of grease or oil related to the use of oxygen systems.
HELICOPTER: MISCELLANEOUS SYSTEMS
Variable rotor speed, active vibration suppression, night-vision goggles (NVG)
Variable rotor speed
Explain the system for ‘beeping’ the NR to its upper limit.
Active vibration suppression
Explain and describe how the active vibration suppression system works through high-speed actuators and accelerometer inputs.
NVG
To be introduced at a later date.
HELICOPTER: ROTOR HEADS
Main rotor
Types
Describe the following rotor-head systems:
— teetering (semi-articulated);
— articulated;
— hingeless (rigid);
— bearingless (semi-articulated).
Describe in basic terms the following configuration of rotor systems and their advantages and disadvantages:
— tandem;
— coaxial;
— side by side.
Explain how flapping, dragging and feathering is achieved in each rotor-head system.
Structural components and materials, stresses, structural limitations
Identify from a diagram the main structural components of the main types of rotor-head systems.
List and describe the methods used to detect damage and cracks.
Explain and describe the structural limitations to respective rotor systems, including the dangers of negative G inputs to certain rotor-head systems.
Describe the various rotor-head lubrication methods.
Design and construction
Describe the material technology used in rotor-head design, including construction, using the following materials or mixture of materials:
— composites;
— fibreglass;
— alloys;
— elastomers.
Adjustment
Describe and explain the methods of adjustment which are possible on various helicopter rotor-head assemblies.
Tail rotor
Types
Describe the following tail-rotor systems:
— delta-3 hinge effect;
— multi-bladed delta-3 effect;
— Fenestron or ducted fan tail rotor;
— no tail rotor (NOTAR) low-velocity air jet flows from tangential slots (the Coandă effect);
— NOTAR high-velocity air jet flows from adjustable nozzles (the Coandă effect).
Identify from a diagram the main structural components of the four main types of tail-rotor systems.
Explain and describe the methods to detect damage and cracks on the tail rotor and assembly.
Explain and describe the structural limitations to the respective tail-rotor systems and possible limitations regarding the turning rate of the helicopter.
Explain and describe the following methods that helicopter designers use to minimise tail-rotor drift and roll:
— reducing the couple arm (tail rotor on a pylon);
— offsetting the rotor mast;
— use of ‘bias’ in cyclic control mechanism.
Explain pitch-input mechanisms.
Explain the relationship between tail-rotor thrust and engine power.
Describe how the vertical fin on some types reduces the power demand of the tail rotor.
Design and construction
List and describe the various tail-rotor designs and construction methods used on helicopters currently in service.
HELICOPTER: TRANSMISSION
Main gearbox
Different types, design, operation, limitations
Describe the following main principles of helicopter transmission systems for single- and twin-engine helicopters:
— drive for the main and tail rotor;
— accessory drive for the generator(s), alternator(s), hydraulic and oil pumps, oil cooler(s) and tachometers.
Describe the reason for limitations on multi-engine helicopter transmissions in various engine-out situations.
Describe how the passive vibration control works with gearbox mountings.
Rotor brake
Types, operational considerations
Describe the main function of the disc type of rotor brake.
Describe both hydraulic- and cable-operated rotor‑brake systems.
Describe the different options for the location of the rotor brake.
List the following operational considerations for the use of rotor brakes:
— rotor speed at engagement of rotor brake;
— risk of blade sailing in windy conditions;
— risk of rotor-brake overheating and possible fire when brake is applied above the maximum limit, particularly when spilled hydraulic fluid is present;
— avoid stopping blades over jet-pipe exhaust with engine running;
— cockpit annunciation of rotor-brake operation.
Auxiliary systems
Powering the air-conditioning system
Explain how power for the air-conditioning system is taken from the auxiliary gearbox.
Driveshaft and associated installation
Power, construction, materials, speed and torque
Describe how power is transmitted from the engine to the main-rotor gearbox.
Describe the material and construction of the driveshaft.
Explain the need for alignment between the engine and the main- rotor gearbox.
Identify how temporary misalignment occurs between driving and driven components.
Explain the relationship between driveshaft speed and torque.
Describe the methods with which power is delivered to the tail rotor.
Describe and identify the construction and materials of tail-rotor/Fenestron driveshafts.
Intermediate and tail gearbox
Lubrication, gearing
Explain and describe the various arrangements when the drive changes direction and the need for an intermediate or tail gearbox.
Explain the lubrication requirements for intermediate and tail-rotor gearboxes and methods of checking levels.
Explain how on most helicopters the tail-rotor gearbox contains gearing, etc., for the tail-rotor pitch-change mechanism.
Clutches
Purpose, operation, components, serviceability
Explain the purpose of a clutch.
Describe and explain the operation of a:
— centrifugal clutch;
— actuated clutch.
List the typical components of the various clutches.
Identify the following methods by which clutch serviceability can be ascertained:
— brake-shoe dust;
— vibration;
— main-rotor run-down time;
— engine speed at time of main-rotor engagement;
— belt tensioning;
— start protection in a belt-drive clutch system.
Freewheels
Purpose, operation, components, location
Explain the purpose of a freewheel.
Describe and explain the operation of a:
— cam- and roller-type freewheel;
— sprag-clutch-type freewheel.
List the typical components of the various freewheels.
Identify the various locations of freewheels in power plant and transmission systems.
Explain the implications regarding the engagement and disengagement of the freewheel.
HELICOPTER: BLADES
Main-rotor design and blade design
Design, construction
Describe the different types of blade construction and the need for torsional stiffness.
Describe the principles of heating systems/pads on some blades for anti-icing/de-icing.
Describe the fully articulated rotor with hinges and feathering hinges.
Structural components and materials
List the materials used in the construction of main‑rotor blades.
List the main structural components of a main-rotor blade and their function.
Describe the drag hinge of the fully articulated rotor and the lag flexure in the hingeless rotor.
Explain the necessity for drag dampers.
Forces and stresses
Describe main-rotor blade-loading on the ground and in flight.
Describe where the most common stress areas are on rotor blades.
Show how the centrifugal forces depend on rotor rpm and blade mass and how they pull on the blade’s attachment to the hub. Justify the upper limit of the rotor rpm.
Assume a rigid attachment and show how thrust may cause huge oscillating bending moments which stress the attachment.
Explain why flapping hinges do not transfer such moments. Show the small flapping hinge offset on fully articulated rotors and zero offset in the case of teetering rotors.
Describe the working principle of the flexible element in the hingeless rotor and describe the equivalent flapping hinge offset compared to that of the articulated rotor.
Structural limitations
Explain the structural limitations in terms of bending and rotor rpm.
Adjustment
Explain the use of trim tabs.
Tip shape
Describe the various blade-tip shapes used by different manufacturers and compare their advantages and disadvantages.
Origins of the vertical vibrations
Explain the lift (thrust) variations per revolution of a blade and the resulting vertical total rotor thrust (TRT) variation in the case of perfectly identical blades.
Show the resulting frequencies and amplitudes as a function of the number of blades.
Explain the thrust variation in the case of an out-of-track blade, causes, and frequencies (one-per-revolution).
Lateral vibrations
Explain blade imbalances, causes, and effects.
Tail-rotor design and blade design
Design, construction
Describe the most common design of tail-rotor blade construction, consisting of stainless steel shell reinforced by a honeycomb filler and stainless steel leading abrasive strip.
Explain that ballast weights are located at the inboard trailing edge and tip of blades, and that the weights used are determined when the blades are manufactured.
Describe how, for some helicopters, anti-icing/de-icing systems are designed into the blade construction.
Describe the two-bladed rotor with a teetering hinge, and rotors with more than two blades.
Describe the dangers to ground personnel and to the rotor blades, and how to minimise these dangers.
Stresses, vibrations and balancing
Describe the tail-rotor blade-loading on the ground and in flight.
Explain the sources of vibration of the tail rotor and the resulting high frequencies.
Explain balancing and tracking of the tail rotor.
Structural limitations
Describe the structural limitations of the tail-rotor blades.
Describe the method of checking the strike indicators placed on the tip of some tail-rotor blades.
Adjustment
Describe the adjustment of yaw pedals in the cockpit to obtain full-control authority of the tail rotor.
The Fenestron
Describe the technical layout of a Fenestron tail rotor.
Explain the advantages and disadvantages of a Fenestron tail rotor.
No tail rotor (NOTAR)
Describe the technical layout of a NOTAR design.
Explain the control concepts of a NOTAR.
Explain the advantages and disadvantages of a NOTAR design.

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