CPL AGK / Systems cheat sheet

Primary structure uses fail-safe design: multiple load paths, crack stoppers and redundant members so a single crack cannot cause catastrophic failure before detection.

Semi-monocoque fuselage: skin and stringers carry tension and shear; frames and bulkheads stabilise the skin and carry concentrated loads (wing attach, landing gear, pressure bulkheads).

Wing spar caps take bending, webs take shear, skin takes torsion in a torsion-box layout; ribs maintain aerofoil shape and transfer loads to spars.

Control surfaces: ailerons for roll, elevators for pitch, rudder for yaw; tabs (trim, balance, servo) reduce hinge moment or provide trim authority.

Actuation is manual (cable/push-pull rod), power-assisted or fully powered; irreversible powered controls need artificial feel because aerodynamic hinge moment does not reach the cockpit.

Cable systems need correct tension and fairlead/pulley alignment; excessive slack causes lost motion and flutter risk, excessive tension causes friction and wear.

Flaps increase lift and drag; types include plain, split, slotted and Fowler (translating, increasing area and camber); asymmetric extension produces a strong roll and is prevented by asymmetry or skew detection.

Mass balance of control surfaces (horn or leading-edge weights) keeps the surface centre of gravity ahead of the hinge to prevent flutter; missing balance weights are a no-go item.

Pascal's law: pressure is transmitted undiminished; force = pressure x area, so a large actuator piston produces greater force than a small pump piston at the same pressure.

Reservoirs are pressurised (bleed air or nitrogen) to prevent pump cavitation at altitude and to feed the pump positively; level sensors trigger low-level warnings.

Pumps: engine-driven (constant delivery, need a pressure regulator and relief valve) or variable-displacement (compensator adjusts stroke to hold system pressure); electric pumps provide ground/standby operation.

Accumulators store energy in a gas-charged chamber for peak demand, emergency operation (e.g. brake or gear extension) and to damp pressure pulsations; precharge is checked with the system depressurised.

Pressure relief valves protect the system from overpressure; sequence valves ensure gear doors open before gear extends; priority valves shed heavy loads when pressure falls.

Selector valves direct flow to actuators; check valves prevent reverse flow; thermal relief valves vent fluid expanded by heat.

Filters and return-line filters trap contamination; bypass indicators show a clogged element, and fluid sampling detects particulate and water contamination.

Monitoring: pressure gauges/transducers, low-pressure caution lights, reservoir level and temperature indications, and pump running lights; system pressure is typically 3000 psi on transport aircraft.

Bleed air sources: engine compressor stages (low and high pressure, with a pressure-regulating/shut-off valve), APU load compressor, and ground cart connection.

Bleed air is used for engine and wing anti-ice, pressurisation air-conditioning packs, hydraulic reservoir pressurisation, water tank pressurisation and engine starting.

Cabin pressurisation: outflow valve modulates to control cabin altitude; max differential pressure is protected by positive-pressure relief valves and negative-pressure relief valves.

Cabin altitude warning triggers if cabin altitude exceeds about 10,000 ft; passenger oxygen masks deploy automatically at about 14,000 ft cabin altitude.

Air-conditioning packs use bleed air through heat exchangers (primary and secondary) and an air cycle machine (compressor-turbine) to produce cold air; water separation removes moisture.

Temperature control valves modulate hot bleed air into the pack outlet to hold selected cabin temperature; zone trim air allows different temperatures in cabin zones.

Pressurisation controllers have automatic modes (climb, cruise, descent) and a manual mode; the aircraft is not pressurised until the doors are closed and the outflow valve is controlling.

Leak detection: bleed-air duct overheat/leak sensors close the affected valves; pack overheat and duct overheat warnings require isolation of the affected system.

DC generation: engine-driven or APU-driven DC generators or transformer-rectifier units (TRUs) convert AC to 28 V DC; batteries supply essential DC during generator loss and for starting.

AC generation: 115 V 400 Hz from integrated drive generators (IDG) with a constant-speed drive, or variable-frequency generators on modern aircraft.

Generator paralleling requires matching voltage, frequency and phase; a generator control unit (GCU) regulates voltage, protects the generator and controls contactor connection.

Protection: overvoltage, undervoltage, overfrequency, underfrequency, overcurrent and differential (feeder) protection trip the generator control breaker and illuminate a fault light.

Bus architecture: main buses, essential/emergency buses fed by battery or static inverter, and ground service buses; bus tie contactors reconfigure supply after a generator failure.

Circuit protection: fuses (one-shot) and circuit breakers (resettable, thermal or magnetic); a popped breaker is not reset more than once without finding the cause.

Batteries: lead-acid or nickel-cadmium; NiCd needs electrolyte level checks and can suffer thermal runaway, so overheat detection and correct charging matter.

External power is connected through a receptacle with interlocks; correct polarity and voltage must be verified before closing the external power contactor.

Fuel is stored in integral wing tanks, with a centre tank on larger aircraft; vents maintain ambient pressure in the tank and prevent overpressure or vacuum during refuelling and feeding.

Feed: boost pumps deliver fuel from the tank to the engine; each engine has its own tank feed so both engines are not fed from one tank in normal operation.

Crossfeed valves allow any tank to feed either or both engines; transfer and scavenge systems move fuel to maintain balance and use the last fuel in the tank.

Fuel quantity gauging uses capacitance probes (dielectric change with fuel level) compensated for fuel density; a drip stick or magnetic level indicator provides a backup check.

Low-pressure warning lights indicate boost pump failure; fuel temperature and fuel used indications support management and detect leaks.

Refuelling is pressure refuelling through a single-point coupling with automatic shutoff; the refuel panel controls tank selection and shows quantity.

Fuel jettison (where fitted) dumps fuel from the outer tanks to reduce landing weight; jettison and transfer valves are interlocked to prevent dumping the fuel meant for the engines.

Contamination: water drains from sump drains before flight; microbial growth and ice crystals can block filters, so fuel heaters or anti-ice additives may be used.

Engine installation: nacelle and pylon carry engine loads, provide firewalls, cooling air and exhaust routing; engine mounts absorb thrust and torque reactions.

Lubrication: dry-sump system with pressure pump, scavenge pumps, oil cooler, filter and chip detector; oil pressure and temperature are monitored with warning limits.

Ignition: high-energy ignition units feed igniter plugs; turbine engines need ignition for starting and often continuous ignition in rain or turbulence.

Starting: air-turbine starter (bleed air) or electric starter drives the compressor to self-sustaining speed; start sequence includes ignition, fuel on, light-off and starter cutout.

Propeller control: constant-speed unit (governor) adjusts blade angle to hold selected rpm; oil pressure or counterweights/springs drive blade angle depending on design.

Propeller feathering sets blades to minimum drag for engine shutdown; reverse pitch gives reverse thrust on the ground; beta range is the ground operating range below flight idle.

Propeller indications: rpm, manifold pressure (piston) or torque (turboprop), and synchrophase for multi-engine aircraft; overspeed governor limits rpm.

Engine indications: N1/N2, EGT/ITT, fuel flow, oil pressure/temperature and vibration; exceedance limits are defined in the flight manual.

Anti-icing prevents ice formation (thermal bleed air to wing leading edges, engine inlets and pitot tubes); de-icing removes ice already formed (boots, electro-thermal cycling).

Pitot and static heaters keep probes clear; a failed heater can give erroneous airspeed and altitude indications, so heater failure is treated as a serious defect.

Windscreen protection: electrical heating for anti-ice/anti-fog and rain removal by wipers or a rain-repellent coating; heated windscreens need controlled power to avoid thermal cracking.

Propeller anti-icing uses electro-thermal boots or fluid; icing reduces thrust and can cause vibration from asymmetric shedding.

Ice detector systems trigger automatic anti-ice operation and advisory messages; holdover time tables give protection time after de-icing fluid application.

Carburettor ice can form at outside air temperatures between about -5 C and +15 C with high humidity; carburettor heat is the remedy.

Air data probes: pitot tubes must be clear of ice and covers; static ports must be unobstructed because blockage causes altimeter and airspeed errors.

Rain and hail: avoid flight through severe hail; radar and storm avoidance protect the airframe, engines and windscreen from damage.

Extension/retraction: hydraulic or electric actuation with uplocks and downlocks; the gear must be locked down before landing, indicated by green lights and a warning horn if not.

Emergency extension: gravity free-fall or a separate accumulator/nitrogen bottle; the handle releases uplocks and allows the gear to fall and lock.

Brakes: independent left and right brake systems with pedals; hydraulic brakes use master cylinders or power brake valves; parking brake holds pressure via a valve.

Antiskid: wheel speed sensors detect a locked wheel and modulate brake pressure to maintain optimum slip; a failed antiskid may require reduced braking and longer landing distance.

Autobrake selects a deceleration rate for landing or a takeoff setting; it disarms if the system detects a fault or the pilot applies pedal braking.

Tyres: ply rating and pressure determine load capacity; underinflation causes sidewall flexing and heat, overinflation reduces footprint and increases wear.

Wheel assemblies include fusible plugs that melt to release pressure on overheating, preventing tyre burst from brake heat.

Gear indications and warnings: gear-down lights, unsafe warnings, and aural warnings tied to gear position and flap setting; squat switches prevent gear retraction on the ground.

Pitot-static: airspeed indicator uses total minus static pressure; altimeter uses static pressure against a set subscale; vertical speed indicator uses a calibrated leak to show rate of change.

Blocked pitot gives airspeed increasing with altitude (or frozen at climb); blocked static gives airspeed over-reading in climb and under-reading in descent, with altimeter errors.

Gyroscopic instruments: attitude indicator and heading indicator rely on rigidity in space; turn coordinator uses rate gyro precession to show rate of turn and slip.

Attitude and heading reference systems (AHRS) and air data computers replace mechanical gyros and provide digital outputs to displays.

Engine indications: tachometer, EGT/CHT, oil pressure and temperature, fuel flow and manifold pressure; limits are marked with green, amber and red arcs.

Warning systems: master caution and warning, aural alerts (horn, siren, voice), stall warning (stick shaker or horn) and GPWS/EGPWS alerts.

EFIS displays present attitude, airspeed, altitude and navigation data; a failed display causes reversion to a standby instrument or combined display mode.

Standby instruments (airspeed, attitude, altimeter) are independent of main electrical power and are checked during preflight.

Crew oxygen: high-pressure cylinders with pressure regulator, demand masks and a supply indication; preflight checks include cylinder pressure and mask function.

Passenger oxygen: chemical generators or a manifold from the crew supply; masks drop automatically at a cabin altitude of about 14,000 ft.

Fire detection: engine fire loops (continuous sensing element) respond to overheat/fire and trigger warning; cargo and lavatory smoke detectors use photoelectric or ionisation sensors.

Fire extinguishing: engine bottles discharge agent into the affected zone; a two-shot system allows a second discharge; the bottle pressure gauge shows readiness.

Fire warning requires immediate action: identify the affected engine, close the fuel and bleed valves, discharge the agent and land as soon as possible.

Portable extinguishers (Halon or equivalent) are carried in the cockpit and cabin and must be checked for pressure and seal.

Emergency equipment: life jackets, slides/rafts, first aid kits, flashlights and ELT; the ELT transmits on 121.5/406 MHz after activation.

Smoke and fumes in the cockpit require oxygen masks, smoke goggles and smoke removal procedures; the source must be identified.

Autopilot: a flight control computer drives servos to hold attitude, heading, altitude or a navigation track; the autopilot disengages on pilot input, system fault or loss of required data.

Autopilot modes: lateral (heading, NAV, approach) and vertical (altitude hold, vertical speed, IAS/Mach, glideslope); armed modes engage when capture criteria are met.

Autothrottle controls thrust to hold speed or to meet a flight profile; it disengages on fault or when the pilot overrides it.

Flight director provides guidance cues on the attitude display; the autopilot follows the same computed commands.

Avionics architecture: line-replaceable units on ARINC 429 or 664 (AFDX) data buses; a failed unit is isolated and its function may be taken by another unit.

Communication: VHF com radios, intercom and audio panel; emergency frequency 121.5 MHz; SELCAL for ground contact on long-range flights.

Navigation: VOR, DME, ILS, GPS/GNSS, ADF and inertial reference systems; FMS integrates position and flight plan and provides guidance to the autopilot.

Transponder and TCAS: Mode S transponder with altitude reporting; TCAS gives traffic advisories and resolution advisories, and the autopilot may be commanded by the TCAS.