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What are the basic energy-conversion stages of a gas-turbine engine? empezar lección
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Intake → compression → combustion → turbine expansion → exhaust/nozzle; the turbine extracts enough energy to drive the compressor/fan, while the remaining energy produces thrust.
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Why does a turbofan produce most of its thrust efficiently through bypass flow? empezar lección
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It accelerates a large mass of air by a relatively small velocity increase, which is more propulsively efficient at subsonic transport speeds than accelerating a smaller mass much more.
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empezar lección
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The ratio of mass airflow bypassing the engine core to mass airflow passing through the core.
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What is the purpose of multiple compressor/turbine spools? empezar lección
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They allow different compressor sections to rotate at their most efficient speeds and improve starting, stability and overall engine performance.
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What do N1 and N2 broadly represent on a two-spool turbofan? empezar lección
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N1 represents low-pressure spool/fan speed; N2 represents high-pressure spool speed.
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empezar lección
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The ratio of engine exhaust pressure to inlet pressure, used on some engines as an indication of thrust.
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Why does a compressor increase both pressure and temperature? empezar lección
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Mechanical work is added to the airflow, increasing its total pressure and total temperature.
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What powers the compressor in steady engine operation? empezar lección
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The turbine extracts energy from the hot combustion gases and transmits it mechanically through the engine shaft.
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Why is only part of the oxygen entering a turbine engine used for combustion? empezar lección
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A large amount of air is needed for cooling, dilution and turbine-temperature control in addition to combustion.
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What is FADEC responsible for? empezar lección
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Automatic engine control including fuel scheduling, thrust management, start sequencing and protection/limit functions according to the engine design.
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What is the main operational benefit of FADEC? empezar lección
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It reduces pilot workload and prevents many engine parameters from being exceeded through inappropriate manual fuel control.
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What is the difference between a compressor stall and compressor surge? empezar lección
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A stall is local airflow separation on compressor blades; surge is a major breakdown of compressor flow that may involve violent pressure oscillation or temporary flow reversal through the engine.
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What can promote compressor stall or surge? empezar lección
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Disturbed inlet airflow, rapid power changes, foreign-object damage, icing or compressor/control-system malfunction.
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What indications may accompany a severe compressor stall/surge? empezar lección
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Bang or rumble, engine vibration, fluctuating parameters, loss of thrust and possibly increased EGT.
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empezar lección
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An engine start in which turbine temperature exceeds the permitted start limit.
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empezar lección
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The engine stabilises below normal self-sustaining idle speed instead of accelerating normally.
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empezar lección
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Fuel enters the engine during start but does not ignite, leaving unburned fuel in the combustion section/exhaust.
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Why must turbine temperature be closely monitored during engine start? empezar lección
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Airflow is initially low, so excessive fuel or insufficient compressor acceleration can quickly overheat turbine components.
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What is the main purpose of an APU on a transport aircraft? empezar lección
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To provide electrical power and/or pneumatic air independently of the main engines, particularly on the ground and as applicable in flight.
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Why may APU capability become more restricted with altitude? empezar lección
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Lower air density reduces compressor mass flow and therefore pneumatic and power capability.
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What is bleed air commonly used for on conventional transport aircraft? empezar lección
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Air conditioning, pressurisation, engine starting and thermal anti-icing, depending on aircraft design.
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Where is engine bleed air normally taken from? empezar lección
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From compressor stages, with the selected source varying with engine operating conditions.
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Why is high-stage bleed not used continuously when low-stage bleed is sufficient? empezar lección
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Higher-pressure bleed extracts more useful energy from the engine and carries a greater performance penalty.
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What is the basic function of an air-conditioning PACK? empezar lección
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To cool, condition and regulate compressed air before it enters the aircraft cabin.
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What primarily controls cabin pressure in a conventional pressurisation system? empezar lección
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The amount of air leaving the pressure vessel through the outflow valve.
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Why is the outflow valve normally more important for pressure control than changing PACK inflow? empezar lección
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Cabin inflow is relatively continuous; controlled restriction of outflow allows precise regulation of cabin pressure.
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What is differential pressure? empezar lección
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The difference between cabin pressure and ambient outside pressure.
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Why is maximum differential pressure structurally limited? empezar lección
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The fuselage pressure vessel must not be subjected to loads beyond its certified structural limit.
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What prevents excessive positive or negative cabin differential pressure if normal control fails? empezar lección
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Why does cabin altitude rise during a depressurisation at high altitude? empezar lección
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Cabin pressure falls toward the much lower ambient pressure, so the equivalent pressure altitude inside the cabin increases.
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What is the basic architecture principle of transport-aircraft electrical systems? empezar lección
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Multiple independent sources and buses are arranged so essential equipment can remain powered after individual failures.
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What are the usual primary electrical sources in flight? empezar lección
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Engine-driven generators, with the APU generator, batteries and emergency sources available depending on aircraft design.
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What is the function of a transformer rectifier unit (TRU)? empezar lección
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It converts AC electrical power to DC.
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What is the purpose of an aircraft battery beyond engine/APU starting? empezar lección
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It provides stored DC energy for essential equipment when normal generation is unavailable and supports electrical transients.
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What is a static inverter used for? empezar lección
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To convert DC electrical power into AC for selected essential loads when normal AC generation is unavailable.
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What is electrical load shedding? empezar lección
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Automatic or procedural removal of non-essential electrical loads to preserve power for essential systems after generation loss.
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Why are electrical buses separated during normal operation but capable of being interconnected? empezar lección
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Separation limits propagation of faults; interconnection allows a remaining source to power additional buses after a failure.
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What is the purpose of a RAT on aircraft equipped with one? empezar lección
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To provide limited emergency hydraulic and/or electrical power after major loss of normal energy sources.
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Why are hydraulic systems widely used on transport aircraft? empezar lección
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They can transmit very large forces with compact actuators and precise control.
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What is the difference between hydraulic pressure and hydraulic flow? empezar lección
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Pressure provides the potential force; flow is required to move an actuator and determines how quickly hydraulic work can be performed.
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Why can a hydraulic system show normal pressure but still fail to operate an actuator properly? empezar lección
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A restriction, low fluid quantity or failed pump may prevent sufficient flow despite pressure being indicated.
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What is the purpose of a hydraulic accumulator? empezar lección
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To store hydraulic energy, damp pressure fluctuations and provide a limited reserve for specific functions.
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What is the purpose of a PTU? empezar lección
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To transfer hydraulic power between systems without transferring hydraulic fluid between them.
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Why are transport-aircraft hydraulic systems normally separated and redundant? empezar lección
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A leak or component failure in one system should not disable all flight-control or landing functions.
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Why may hydraulic reservoirs be pressurised? empezar lección
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To ensure positive fluid supply to pumps and reduce cavitation, particularly at altitude.
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What is the basic purpose of fuel crossfeed? empezar lección
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To allow an engine or fuel system to be supplied from another tank/feed path when required.
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Why is fuel crossfeed different from fuel transfer? empezar lección
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Crossfeed changes the source feeding an engine; transfer physically moves fuel from one tank to another.
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Why is fuel imbalance undesirable? empezar lección
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It creates lateral mass imbalance and may increase structural loads, drag or control requirements.
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Why are boost pumps used in aircraft fuel systems? empezar lección
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They provide positive fuel pressure to the engine feed system and reduce the risk of vapour formation or interruption of supply.
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Why must fuel temperature sometimes be monitored in flight? empezar lección
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Very low fuel temperature can approach the fuel freezing limit and restrict safe operation.
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What is the fundamental difference between mechanical flight controls and fly-by-wire? empezar lección
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Mechanical systems transmit pilot input through physical linkages; fly-by-wire converts pilot commands into electrical signals processed by computers before commanding actuators.
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Does fly-by-wire mean the control surfaces are electrically powered? empezar lección
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Not necessarily. Commands are electrical, while the actuators may be hydraulic, electro-hydraulic or electric.
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Why does fly-by-wire require extensive redundancy? empezar lección
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A single electrical, computing or sensor failure must not cause loss of essential flight-control capability.
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What is the basic purpose of anti-skid braking? empezar lección
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To regulate brake pressure near optimum tyre slip and prevent wheel lock, improving directional control and braking effectiveness.
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Why can a locked wheel provide less useful braking on a wet runway? empezar lección
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It loses optimal tyre-road friction and becomes much more susceptible to skidding or hydroplaning.
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What is the basic principle of an autobrake system? empezar lección
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It automatically modulates braking to achieve a selected deceleration target rather than simply applying a fixed brake pressure.
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Why can brake temperature become operationally significant after a high-energy stop? empezar lección
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Excessive brake energy can damage brakes/tyres and may create a fire risk or require cooling before further operation.
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How do thermal and pneumatic ice-protection systems differ? empezar lección
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Thermal systems prevent/remove ice using heat; pneumatic boots remove accumulated ice by cyclically deforming the protected surface.
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Why are pitot probes and similar air-data sensors heated? empezar lección
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To prevent ice from blocking or corrupting pressure measurements used for airspeed and other flight data.
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What is the purpose of fire-detection loops in engines/APUs? empezar lección
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To detect excessive heat or fire while providing redundancy and reducing false warnings.
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What is the general effect of activating an engine fire-isolation control? empezar lección
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It isolates major fuel, pneumatic, hydraulic and/or electrical connections as designed and arms or enables extinguishing capability; exact actions are aircraft-specific.
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Why are engine fire bottles not simply discharged immediately for every fire warning? empezar lección
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Initial isolation and shutdown remove fuel/energy sources; extinguishing agent is then used according to the aircraft procedure if required.
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