CAA NZ AME Subject 2: Aircraft Engineering Knowledge cheat sheet

Semi-monocoque construction uses skin to carry shear and tension, stringers and frames to stabilize the skin and carry axial loads, and spar caps to resist bending.

Stress = load / cross-sectional area; strain = change in length / original length; in the elastic range stress is proportional to strain (Hooke's law).

Primary structure carries flight, ground, and pressurization loads and must be inspected for fatigue; secondary structure includes fairings and non-load-bearing access panels.

Fail-safe design allows a cracked element to be detected before residual strength falls below limit load; safe-life parts are removed before calculated fatigue life expires.

Wing bending is carried mainly by spar caps in tension and compression; shear webs carry vertical shear, and ribs maintain aerofoil shape and transfer loads.

Thin compression panels can buckle below ultimate load; stringers, frames, and ribs raise the buckling critical stress.

Damage tolerance requires that principal structural elements be inspectable for cracks; inspection intervals are set from crack growth analysis.

Honeycomb sandwich: face sheets carry bending stress and the core carries shear; disbonds are detected by tap test, ultrasonic, or radiographic methods.

Lift L = C_L × ½ρV²S; for steady level flight L = W, so stall speed rises as the square root of load factor (V_s ∝ √n).

Induced drag = C_L²/(πeAR) × ½ρV²S; it decreases as speed increases and increases with load factor and lower aspect ratio.

Critical angle of attack is typically 15–18°; the wing stalls at that angle regardless of airspeed, weight, or attitude.

Positive static longitudinal stability requires the CG forward of the neutral point; the horizontal tail provides a nose-down restoring moment.

Dihedral produces a sideslip-induced rolling moment that opposes the sideslip, giving positive lateral stability; excessive dihedral can contribute to Dutch roll.

Primary flight controls are ailerons for roll, elevator for pitch, and rudder for yaw; flaps, trim tabs, and spoilers are secondary or auxiliary controls.

Fly-by-wire systems use computers to shape control laws, provide artificial feel, and limit the flight envelope; hydraulic actuators move the surfaces.

Vortex generators re-energize the boundary layer and delay separation; they must be inspected for correct height, spacing, and condition.

Load factor n = L/W; manoeuvring speed V_A is the speed at which full deflection of one control does not overstress the structure.

Typical transport hydraulic system pressure is 3000 psi; phosphate-ester fluid is fire-resistant and requires compatible seals and paint.

A hydraulic accumulator stores pressure energy, damps pump pulses, and supplies temporary flow during peak demand; precharge is set with nitrogen.

A pressure relief valve protects the system from overpressure; a pressure regulator controls pump output; filters remove particulate contamination.

Pneumatic bleed air is taken from the engine HP compressor, cooled in a precooler, and used for cabin air conditioning, anti-ice, and engine starting.

Cabin pressurization is controlled by the outflow valve; maximum differential pressure is limited by relief valves, and cabin altitude is scheduled with aircraft altitude.

Fuel systems use boost pumps, vent lines, and crossfeed valves; fuel quantity is often measured by capacitance probes compensated for density.

Thermal anti-ice uses hot bleed air on wing leading edges and engine inlets; electrothermal de-ice uses electrical heating elements and is cyclic.

Windshield rain removal uses wipers, hydrophobic coatings, or high-pressure air; windshield heating prevents fogging and ice formation.

Hydraulic fluid contamination is classified by particle size; water contamination is detected by sampling and removed by vacuum dehydration or filters.

A reciprocating engine operates on the four-stroke Otto cycle: intake, compression, power, exhaust; the mixture is ignited by dual magnetos for redundancy.

Detonation is uncontrolled explosive combustion causing high cylinder pressure and temperature; pre-ignition is ignition before the spark, often from a hot spot.

A gas turbine follows the Brayton cycle: compression, constant-pressure combustion, expansion through the turbine, and exhaust; thrust = ṁ(V_j − V_0).

Turbine engine N1 is fan or low-pressure spool speed and N2 is high-pressure spool speed; EGT indicates turbine temperature and is limited by the EEC or FADEC.

Compressor surge is a reversal of flow caused by excessive angle of attack on the blades; variable inlet guide vanes and bleed valves improve stall margin.

Turboprop engines use a free turbine or fixed turbine through a reduction gearbox to drive the propeller at optimum RPM.

Engine starters may be electric, air-turbine, or combustion; ignition exciters supply high-energy sparks during start and in some icing conditions.

Reciprocating engine compression ratio is cylinder volume at bottom dead centre divided by volume at top dead centre; higher ratio increases thermal efficiency.

Turbine engine bleed air for airframe systems reduces engine thrust; bleed valves are modulated to maintain pressure and prevent compressor instability.

Propeller thrust is produced by accelerating a mass of air rearward; thrust = ṁ(V_out − V_in), and power required rises with the cube of RPM.

Blade angle is the angle between the blade chord and the plane of rotation; angle of attack is blade angle minus helix angle.

A constant-speed propeller uses a governor to vary blade angle and maintain selected RPM as load or airspeed changes.

Feathering rotates blades to a high-pitch, low-drag position to reduce drag after engine failure; reverse pitch produces negative thrust on the ground.

P-factor is the yawing moment caused by the descending blade taking a larger angle of attack at high aircraft angle of attack.

Propeller tracking checks blade tip path in one plane; blade balance is corrected by adding or removing weights or by adjusting blade pitch.

Propeller ice protection may use electrothermal boots on the blades; ice accretion reduces thrust and causes vibration.

Propeller tip clearance and spinner condition affect performance; composite blades require inspection for delamination and erosion.

Beta range allows direct control of blade angle for ground reverse and taxi; a beta lockout prevents inadvertent in-flight selection.

Typical aircraft DC systems are 28 V; AC systems are 115 V at 400 Hz; a transformer-rectifier unit converts AC to DC.

A generator or alternator is driven by the engine or APU; a starter-generator combines starting and generating functions on some turbine engines.

Circuit breakers protect wiring; they are thermal or magnetic and must be reset only after the fault is cleared, following the approved manual.

Lead-acid batteries require electrolyte level checks and venting; nickel-cadmium batteries have higher energy density but can suffer thermal runaway.

Electrical bonding provides a low-resistance path for fault current and static discharge; shielded cables reduce electromagnetic interference.

A constant-speed drive or integrated drive generator maintains 400 Hz AC frequency; variable-frequency systems eliminate the constant-speed drive.

An electrical load analysis ensures generator capacity covers continuous and intermittent loads; bus ties allow power transfer between buses.

A static inverter converts DC to AC for emergency or standby equipment; emergency power may be supplied by a battery or ram-air turbine.

The pitot-static system supplies total pressure to the airspeed indicator and static pressure to the altimeter, VSI, and airspeed indicator; blockage causes erroneous indications.

A blocked pitot tube with an open static drain causes the airspeed indicator to act like an altimeter; a blocked static port affects altimeter, VSI, and airspeed indicator.

Gyroscopic instruments use rigidity in space for attitude and heading gyros and precession for rate gyros; vacuum or electric power may drive them.

An air data computer computes airspeed, altitude, vertical speed, and temperature from pitot-static and temperature inputs for display and flight control.

An attitude and heading reference system uses solid-state gyros and accelerometers; an inertial reference system uses ring-laser gyros for position.

VOR provides bearing to a station; DME provides slant-range distance; ILS provides localizer and glide-slope guidance for approach.

A transponder replies to secondary radar with identity and altitude; TCAS interrogates nearby transponders and issues traffic alerts.

EFIS displays attitude, heading, and navigation data; EICAS or ECAM displays engine and system parameters and alerts.

A radio altimeter measures height above terrain using frequency-modulated continuous wave or pulse radar for low-altitude approaches.

Aluminium alloy 2024 has good fatigue resistance and is used for skins; 7075 has higher strength but lower corrosion resistance and is used for spars and fittings.

Titanium alloys have high strength-to-weight ratio and corrosion resistance; they are used in hot engine sections and high-load airframe parts.

Heat treatment of aluminium involves solution treatment, quenching, and artificial aging (T6) or natural aging (T4) to increase strength.

Carbon-fibre composites have high specific strength and stiffness; they are anisotropic and can suffer delamination, matrix cracking, and galvanic corrosion with metals.

Material properties include yield strength, ultimate tensile strength, elongation, and Young's modulus; design uses limit load and ultimate load factors.

Fatigue cracks initiate at stress concentrations such as holes, fillets, and corrosion pits; surface finish and shot peening improve fatigue life.

Dye penetrant detects surface-breaking defects in non-porous materials; magnetic particle inspection applies only to ferromagnetic materials.

Eddy current inspection detects surface and near-surface cracks in conductive materials; ultrasonic inspection detects internal defects and thickness loss.

Galvanic corrosion occurs when dissimilar metals are joined in the presence of an electrolyte; the more anodic metal corrodes.

AN bolts are identified by head markings and are used in airframe structures; grip length must match the thickness of the parts so the thread does not bear on the hole.

Torque values are specified in the maintenance manual; use a calibrated torque wrench and account for friction, lubrication, and adapter length.

Lockwire prevents fasteners from loosening; it must be installed in the tightening direction with correct twist and pigtail.

Self-locking nuts use a nylon insert or deformed thread; they are not reused if the locking feature is degraded, following the manual.

Cotter pins and castle nuts secure bolts in shear applications; the cotter pin must fit the hole and be spread correctly.

Solid rivets are driven with a rivet gun and bucking bar; blind rivets are used where access is limited; edge distance is typically at least twice the diameter.

Turnbuckles adjust cable tension and are safetied with lockwire or check nuts; cable tension is set by a tensiometer.

Bearings and bushings support rotating or oscillating loads; inspect for wear, corrosion, and freedom of movement.

Washers distribute load and protect surfaces; flat washers are used under bolts, and tab washers lock bolts in place.

Unified threads and metric threads are not interchangeable; identify thread pitch and diameter before fitting a replacement fastener.

Hi-Lok and Hi-Ti fasteners are installed with a collar that breaks off at a predetermined torque; they are used in high-strength structural joints.

Lockbolts form a permanent joint with a swaged collar; they are inspected for proper collar formation and stem break.

Rivet pitch is the distance between rivet centres; minimum edge distance is usually twice the diameter and minimum pitch three times the diameter, following the structural repair manual.

Fastener holes must be deburred and protected with primer or sealant; interference-fit fasteners improve fatigue life in critical joints.

Screws are classified by head type such as Phillips, slotted, or Torx and are used for access panels and non-structural attachments.

Fastener torque creates preload; under-torque allows movement and fatigue, while over-torque can yield the bolt or damage the hole.

Corrosion protection for fasteners includes cadmium plating, anodizing, and dry-film lubricants; dissimilar fasteners require isolation.

Fastener failure modes are tension, shear, and combined tension-shear; inspect for stretched bolts, elongated holes, and loose rivets.

Galvanic corrosion occurs between dissimilar metals in an electrolyte; the anodic metal corrodes, and the rate depends on potential difference and area ratio.

Pitting corrosion is localized breakdown of the passive film, often on aluminium and stainless steel in chloride environments.

Intergranular corrosion attacks grain boundaries, often in improperly heat-treated aluminium alloys; exfoliation is a layered form that lifts the surface.

Stress corrosion cracking requires a susceptible alloy, tensile stress, and a corrosive environment; it produces brittle cracks with little deformation.

Prevention includes protective coatings, primers, sealants, anodizing, and avoiding dissimilar metal contact with isolation tapes or washers.

Inspect for corrosion in bilges, wheel wells, battery compartments, and under galleys and lavatories; clean and treat immediately.

Corrosion removal must stay within blend-out limits in the structural repair manual; reprotect the area after blending.

Zinc-rich primers and sacrificial anodes protect steel and aluminium structures; cadmium plating protects steel fasteners.

Humidity, salt spray, and pollution accelerate corrosion; wash aircraft regularly and maintain drain paths.

The aircraft maintenance manual gives procedures; the illustrated parts catalogue gives part numbers; the structural repair manual gives approved repairs.

An airworthiness directive is mandatory; a service bulletin is recommended unless made mandatory by an airworthiness directive or the operator's program.

A maintenance release certifies that maintenance has been completed and the aircraft is airworthy; it must be signed by an authorised person.

Torque wrenches must be calibrated at specified intervals; check the calibration sticker before use and set the wrench to the specified value.

Tool control and foreign object debris prevention require inventory, shadow boards, and inspection of the work area before closing panels.

Lockout and tagout isolate energy sources during maintenance; verify that hydraulic, electrical, and pneumatic systems are de-energized.

Scheduled maintenance includes pre-flight, transit, daily, and periodic checks; unscheduled maintenance rectifies defects found in service.

Maintenance errors are reduced by using checklists, independent inspection, and human factors training using the SHEL model.

Ground support equipment includes jacks, stands, tugs, and power carts; inspect before use and use only approved equipment.

Jacking an aircraft requires approved jack points, a level surface, and safety stands; never jack under an unsupported structure.

Towing uses a tow bar and a tug; ensure steering bypass is engaged and wing walkers are positioned to monitor clearance.

Mooring uses tie-down rings and approved ropes or chains; control surfaces are locked and pitot covers installed.

Fueling requires bonding the aircraft to the fuel truck and grounding both to earth; no smoking or open flame is permitted within the safety zone.

Ground power units supply 28 V DC or 115 V AC; check voltage and frequency before connecting to the aircraft.

De-icing removes ice with heated fluid; anti-icing applies a protective fluid with a holdover time; both must be approved for the aircraft.

Weight and balance calculations ensure the centre of gravity is within limits; use actual weights and moments and check the load sheet.

Engine ground runs require chocks, a cleared area, a fire extinguisher, and communication with the flight deck; observe intake and exhaust danger zones.

Marshalling signals guide aircraft on the ground; the marshaller must wear high-visibility clothing and stand in the pilot's line of sight.

In New Zealand, Part 43 covers aircraft maintenance, Part 66 covers maintenance personnel licensing, Part 21 covers certification, and Part 145 covers maintenance organisations.

A certificate of airworthiness is issued when the aircraft meets the type design and is maintained in accordance with the rules; it must remain valid for flight.

An airworthiness directive is a mandatory requirement issued by the state of design and adopted by the CAA; compliance must be recorded.

A maintenance release is required before flight after maintenance; it states the maintenance performed and certifies airworthiness.

The minimum equipment list allows dispatch with certain equipment inoperative, subject to conditions and placards.

Defects must be recorded and reported; serious incidents and accidents are reported to the CAA and the Transport Accident Investigation Commission.

Continuing airworthiness includes scheduled maintenance, airworthiness directive compliance, modifications, and repair; records must be kept and traceable.

A service bulletin is not mandatory unless the CAA mandates it or the operator's maintenance program adopts it.

Weight and balance, performance, and equipment lists are part of airworthiness; changes require approval.