Home / Library / Aircraft Systems

Aircraft Systems for pilots

84 articlesEASA & FAAUpdated Nov 2026

How aircraft systems work: engines and their fuel and ignition, hydraulics, electrics, flight controls, landing gear and brakes, pressurization, oxygen and ice protection, from EASA ATPL subject 021.

ATPL · Type rating

A320 and B737 Systems Compared

A system-by-system comparison of the Airbus A320 and Boeing 737: hydraulics, electrics, flight controls, fuel, pneumatics, autoflight and alerting.

AC Electrical Theory

Alternating current principles as used on aircraft, from RMS values and phase to true, reactive and apparent power, power factor and the three-phase 115/200 V 400 Hz supply.

AC Generators, CSD and IDG

How aircraft alternators generate AC power, from brushless construction and exciters to constant speed drives, integrated drive generators and variable-frequency systems.

Air Conditioning Packs

How air conditioning packs cool hot bleed air using heat exchangers and the air cycle machine, remove water, and how pack flow is controlled and pack failures are handled.

ATPL · Type rating

Airbus and Boeing Flight Deck Philosophies

How Airbus and Boeing differ in flight deck design and automation: sidestick versus yoke, protections versus pilot authority, moving thrust levers, alerting and checklists.

PPL · CPL · ATPL

Aircraft Batteries

The lead-acid, nickel-cadmium and lithium-ion batteries used in aircraft, their capacity, charging, switching and monitoring, and hazards such as thermal runaway.

PPL · CPL · ATPL

Aircraft Exterior Lighting

The exterior lights fitted to aircraft (anti-collision beacons, strobes, landing, taxi, turn-off and logo lights) and when each is used.

Aircraft Materials, Fastening and Corrosion

The metals and composites used in airframes, how parts are joined by riveting and bonding, and the forms of corrosion and protective treatments that affect them.

PPL · CPL · ATPL

Aircraft Wheels and Tires

Aircraft wheel types and tire construction, markings and ratings, nitrogen inflation, creep, wear and damage, and the fusible plugs that prevent tire bursts.

CPL · ATPL · Type rating

Aircraft Windows and Windshields

How flight deck windshields and cabin windows are built to carry pressure loads and resist bird strikes, how they are heated, and what crews do about cracks and delamination.

PPL · CPL · ATPL

Airframe Structure and Construction

How aircraft fuselages, wings and tail units are built, from truss and monocoque designs to the semi-monocoque stressed-skin structures and pressure hulls of modern airliners.

Anti-Skid and Autobrake

How anti-skid systems prevent wheel lock and skids, the protections they give at touchdown and against aquaplaning, and how autobrakes deliver a selected deceleration.

Auxiliary Power Unit (APU)

What the APU is and how it supplies electrical and bleed air power, its air intake, starting and shutdown logic, cool-down period and fire protection.

PPL · CPL · ATPL

Aviation Fuel Grades and Properties

The grades of aviation gasoline and jet fuel, their specifications, and key properties such as flash point, freezing point, calorific value, volatility and vapor lock.

Bleed Air and Pneumatic Systems

How compressed air is bled from engine compressors, regulated and distributed through the pneumatic system, and how leaks, duct overheats and contamination are detected.

Cabin Air Distribution and Equipment Cooling

How conditioned air is mixed, recirculated, filtered and distributed to cabin zones, the fresh air requirement, and how avionics bays and cargo compartments are ventilated.

PPL · CPL · ATPL

Cabin Heaters and Engine-Driven Blowers

How light and older aircraft heat and supply cabin air using exhaust heat exchangers, combustion heaters and engine-driven blowers, and the carbon monoxide risk involved.

PPL · CPL · ATPL

Carburetors and Fuel Injection

How float-type carburetors and fuel injection meter fuel for piston engines, and the induction icing, carburetor heat and hot-start problems that affect them.

Cargo and Lavatory Fire Protection

How smoke is detected in cargo holds and lavatories, the cargo compartment classes, and the fixed extinguishing systems that protect these areas.

Circuit Protection and Switching Devices

Fuses, circuit breakers and current limiters that protect aircraft wiring, and the relays, contactors, solenoids and sensing switches that control circuits.

Combustion Chambers and Turbines

How gas turbine combustors burn fuel stably and how turbines extract energy, including turbine materials, blade cooling, creep, clearance control and turbine entry temperature.

Crew Oxygen Systems

The gaseous oxygen systems that supply flight crew, including diluter-demand and pressure-demand regulators, quick-donning masks, smoke goggles and system indicators.

PPL · CPL · ATPL

DC Generators, Motors and Starter-Generators

How DC generators and motors work, how their output is indicated and protected, and how starter-generators combine both roles.

PPL · CPL · ATPL

De-Icing Boots and Fluid Ice Protection

How pneumatic de-icing boots and TKS weeping-wing fluid systems remove or prevent airframe ice, including cyclic operation and ice bridging.

Doors, Emergency Exits and Escape Slides

How aircraft doors and emergency exits are designed and armed, and how escape slides, slide rafts and escape ropes are used for evacuation.

Electrical Bonding, Static and Interference

How bonding, static dischargers and cable screening protect aircraft from static build-up, lightning and electromagnetic or radio frequency interference.

PPL · CPL · ATPL

Electrical Fundamentals and DC Circuits

The basic electrical quantities and laws, series and parallel circuits, capacitors and inductors, and common circuit faults as they apply to aircraft systems.

PPL · CPL · ATPL

Electrical Power Distribution

How electrical power is distributed through busbars, bus ties and contactors, the split and paralleled system layouts, essential buses, external power and load shedding.

PPL · CPL · ATPL

Electromagnetism and Induction

Magnetic fields around conductors, electromagnetic induction and the hand rules that predict how generators and motors behave.

Engine Fire Protection

How engine fires are contained and extinguished, from designated fire zones and firewalls to fire handles, extinguisher bottles and discharge indicators.

Engine Indications and Condition Monitoring

The primary gas turbine engine indications (N1, N2, EPR, fuel flow and EGT) and their limits, plus vibration monitoring, trend monitoring and borescope inspection.

PPL · CPL · ATPL

Engine Lubrication Systems

How piston and gas turbine engines are lubricated, including oil types, pressure and scavenge systems, filters, coolers and the accessory gearbox.

FADEC and Engine Fuel Control

How gas turbine fuel flow is scheduled, from hydromechanical fuel control units to full authority digital engine control, including overspeed and engine limit protection.

Fire and Overheat Detection

How aircraft detect engine, APU and wheel-well fires and overheats, from continuous fire wires and gas-filled detectors to flame detectors and fire warnings.

PPL · CPL · ATPL

Fire Extinguishing Agents and Hand Extinguishers

The fire triangle, the extinguishing agents used on aircraft such as halon, CO2, dry powder, foam and water-glycol, and the hand-held extinguishers carried in the cabin.

How trailing-edge flaps are driven and controlled, and the protections against flap asymmetry, skew and excessive air loads.

Flight Deck Layout and Master Warnings

How the flight deck is arranged for the crew, including the eye reference position, overhead panel and guarded switches, and how master warning and caution lights alert them.

Flight Deck, Cabin and Emergency Lighting

Flight deck and cabin lighting such as integral, flood and dome lights, and the emergency lighting and floor path marking that guide an evacuation.

Fly-by-Wire and Flight Envelope Protection

How fly-by-wire replaces mechanical linkages with computers and electrical signals, the redundancy that makes it safe, the Airbus control laws and the flight envelope protection they provide.

PPL · CPL · ATPL

Fuel Additives and Contamination

Fuel additives such as icing inhibitors, anti-static and lubricity agents, and how water and microbial contamination are prevented, detected and drained.

PPL · CPL · ATPL

Fuel Feed, Boost Pumps and Crossfeed

How fuel is delivered from tanks to engines by gravity or boost pumps, how crossfeed and transfer manage imbalance, and pump problems such as cavitation and unporting.

PPL · CPL · ATPL

Fuel Quantity and Temperature Indication

How fuel quantity is measured and displayed, from float gauges and dripsticks to capacitance systems, and why fuel temperature and cold soak are monitored.

PPL · CPL · ATPL

Fuel Tanks, Venting and Inerting

Types and layout of aircraft fuel tanks, baffles and collector tanks, the vent system, and nitrogen inerting to reduce fuel tank flammability.

Gas Turbine Engine Fuel System

How fuel travels from the aircraft tanks through the engine's LP and HP pumps, heaters, filters and shut-off valves to the fuel manifold.

Gas Turbine Engine Starting

How gas turbine engines are started with pneumatic starters and ground or APU air, the normal sequence to self-sustaining speed, and abnormal starts such as hot, hung and wet starts.

Gas Turbine Engine Types

The main families of gas turbine engine (turbojet, turbofan, turboprop and turboshaft), spool arrangements, bypass ratio, thrust augmentation and how engines are installed on the airframe.

Gas Turbine Ignition, Flameout and Relight

The high-energy ignition system of a gas turbine, when continuous or automatic ignition is used, and how flameouts occur and engines are relit in flight.

Gas Turbine Intakes and Compressors

How intakes and compressors deliver air to a gas turbine, and how compressor stall and surge occur and are prevented with bleed valves and variable vanes.

Gas Turbine Principles, Thrust and Ratings

The thermodynamics of the gas turbine (Brayton cycle, gas laws, duct flow), how thrust is produced, engine efficiencies, and flat rating and thrust time limits.

Generator Control, Protection and Paralleling

How generator control units regulate voltage, protect alternators against faults and connect them to the buses, including synchronizing and load sharing in paralleled systems.

Hydraulic Pumps and Power Sources

How hydraulic pressure is generated and stored, covering engine-driven, electric, air-driven and hand pumps, accumulators, standby systems and the ram air turbine.

Hydraulic System Principles and Fluids

The physics behind aircraft hydraulics, the fluids used, and the reservoirs, filters, seals and system layouts that keep a hydraulic system working.

Hydraulic Valves and Actuators

The valves that direct, limit and protect hydraulic flow, and the jacks, motors and servo actuators that turn fluid pressure into movement.

PPL · CPL · ATPL

Ice Protection and Ice Detection

The difference between anti-icing and de-icing, what aircraft ice and rain protection systems cover, and how airframe ice is detected visually and automatically.

PPL · CPL · ATPL

Landing Gear Indication and Configuration Warnings

How gear position is shown to the crew and how gear and takeoff configuration warnings alert them to unsafe configurations.

PPL · CPL · ATPL

Landing Gear Layouts and Shock Absorbers

The layouts and structure of aircraft landing gear, from tailwheel and tricycle arrangements to bogies, and how oleo-pneumatic struts absorb landing loads.

Landing Gear Retraction and Extension

How landing gear is retracted, locked up and down, protected against retraction on the ground by air/ground logic, and extended by alternate means.

PPL · CPL · IR

Light Aircraft Electrical Systems

The electrical system of a typical light aircraft: battery, alternator, master and avionics switches, ammeter and loadmeter, circuit breakers and alternator failure.

Light Aircraft Fuel Systems

Fuel systems of light aircraft: gravity and pump feed, tanks and vents, selectors, strainers and sumps, fuel grades and colors, vapor lock and fuel management in flight.

Mechanical Flight Control Systems

How cockpit controls connect to the control surfaces through cables, pulleys, bellcranks and torque tubes, and the stops, locks and jam protection built into them.

PPL · CPL · ATPL

Mixture Control and Abnormal Combustion

How pilots control fuel/air mixture in piston engines, from stoichiometric and best-power settings to leaning, and the abnormal combustion it can cause such as detonation and pre-ignition.

PPL · CPL · ATPL

Nose Wheel Steering

How aircraft are steered on the ground through nose wheel and body gear steering, tillers and rudder pedals, and how shimmy, centering and towing are managed.

Passenger and Portable Oxygen

How passengers receive emergency oxygen from continuous-flow masks and chemical generators, and the portable oxygen sets and smoke hoods carried for crew and first aid.

PPL · CPL · ATPL

Piston Engine Ignition Systems

How magnetos and spark plugs ignite the mixture in piston engines, including dual ignition, impulse couplings, ignition timing, magneto checks and plug fouling.

PPL · CPL · ATPL

Piston Engine Principles

How the four-stroke reciprocating engine works, its valve timing and the main measures of power and efficiency, plus engine cooling and cylinder head temperature.

Potable Water and Drain Systems

How the potable water system supplies galleys and lavatories, and how drain masts and engine drains discharge fluids overboard, including drain mast heating.

Powered Flying Controls and Artificial Feel

How hydraulic power control units move control surfaces, the difference between power-assisted and fully powered controls, and how artificial feel restores control forces.

Pressurization Principles and Control

Why aircraft are pressurized, how cabin altitude and differential pressure are controlled through the outflow valve, and the pressurization schedule, modes and rate control.

Pressurization Safety Valves and Warnings

The safety, negative-pressure and dump valves that protect the pressure hull, blow-out panels, and the cabin altitude warnings that signal a pressurization failure.

PPL · CPL · ATPL

Probe Heat, Window Heat and Rain Protection

How pitot and other probes and flight deck windows are heated, and how wipers, rain repellent and hydrophobic coatings keep windshields clear.

PPL · CPL · ATPL

Propeller Ice Protection

How propellers are protected against ice by electrothermal overshoes and fluid slinger rings, and how cyclic de-icing is applied to the blades.

PPL · CPL · ATPL

Propellers and Propeller Control

Propeller pitch and types from fixed-pitch to constant-speed, how the governor controls blade angle, and feathering, reverse pitch, overspeed protection and synchronization.

PPL · CPL · ATPL

Refueling Systems and Fuel Jettison

How aircraft are refueled by gravity or single-point pressure refueling, how defueling works, and how fuel jettison systems dump fuel in flight.

Semiconductors and Logic Gates

Semiconductor basics, diodes and transistors, integrated circuits, and the digital logic gates and truth tables used in aircraft systems.

Spoilers and Speed Brakes

How flight and ground spoilers and speed brakes are used for roll control, drag and lift dumping, and how they are mixed and deployed automatically.

Structural Loads, Stress and Fatigue

The loads an airframe carries (tension, compression, shear, bending and torsion), how materials respond through stress and strain, and why fatigue and stress concentrations limit structural life.

Supercharging and Turbocharging

How superchargers and turbochargers boost piston engine power at altitude, including wastegates, intercoolers, critical altitude, full throttle height and overboost.

Thermal Anti-Icing

How hot bleed air and electrical heating keep wings, engine intakes and nacelles free of ice, and how wing and engine anti-ice are used in operation.

Thrust Levers, Idle Modes and Engine Handling

How thrust levers command engine power, the different idle settings and why spool-up time matters, plus engine warm-up, cooldown and heat soak-back.

Thrust Reversers and Reverse Thrust

How clamshell, target and cascade thrust reversers redirect engine thrust, how they are locked and controlled, and the hazards of re-ingestion and uncommanded deployment.

Transformers, Converters and AC Motors

The devices that change voltage or convert between AC and DC on aircraft (transformers, rectifiers and inverters) and the induction and synchronous motors that run on AC.

How aircraft are trimmed in pitch and yaw, including the trimmable horizontal stabilizer, its screwjack drive, the takeoff green band and rudder trim.

PPL · CPL · ATPL

How aircraft wheel brakes are built and operated, from multi-disc carbon brakes to normal, alternate and parking brake systems, and the hazards of brake fade and hot brakes.

Yaw Dampers and Rudder Limiting

How yaw dampers and stability augmentation counter Dutch roll, and how rudder ratio changers and travel limiters restrict rudder authority at high speed.

Test yourself on Aircraft Systems

The v1prep banks cover this topic in Aircraft General Knowledge (021), with a worked explanation for every answer.

Start practicing →