NZ CAA PPL Aircraft Technical cheat sheet

Four-stroke cycle order: induction, compression, combustion (power), exhaust; one power stroke per two crankshaft revolutions per cylinder.

Mixture ratio is fuel to air by mass; chemically correct (stoichiometric) is about 1:15, best power is slightly rich of that, best economy slightly lean.

Detonation is uncontrolled explosive ignition after normal spark; pre-ignition is ignition before the spark. Both raise CHT; detonation is countered by richer mixture, lower power, cooler induction air.

Carburettor icing is most likely at outside air temperatures roughly -7 °C to +21 °C with high relative humidity; it can occur in clear air and is indicated by falling RPM or manifold pressure with no mixture or throttle change.

Carburettor heat bypasses the air filter and warms intake air, so applying it causes an initial RPM rise then a fall; use full heat for descent and approach to guard against ice.

Magneto check: with the engine warm and at run-up RPM, select each magneto in turn; maximum permissible drop and the maximum difference between them are stated in the aircraft flight manual (commonly about 150 RPM drop, 50 RPM difference).

Oil pressure and oil temperature together indicate lubrication health: low pressure with high temperature suggests pump or level problems; low pressure with low temperature suggests a stuck relief valve or gauge fault.

Pitot-static instruments are the airspeed indicator, altimeter and vertical speed indicator; the gyroscopic instruments (attitude indicator, heading indicator, turn coordinator) are usually vacuum- or electrically driven.

Static port blockage traps pressure: the altimeter freezes, the VSI reads zero, and the ASI behaves like an altimeter, reading higher in a climb and lower in a descent.

Pressure altitude = indicated altitude corrected for barometric setting; density altitude = pressure altitude corrected for non-standard temperature, and it is what the aircraft actually performs at.

Density altitude rises with high elevation, low pressure, high temperature and high humidity; all four reduce engine power, propeller thrust and wing lift.

Take-off and landing distances vary roughly with the square of the change in true airspeed for a given weight, so small weight or density-altitude errors produce large distance errors.

Headwind reduces ground roll and landing distance; tailwind increases them. A 10 % increase in take-off weight typically increases take-off distance by about 20 % or more.

Best rate of climb (VY) gives most height per unit time; best angle of climb (VX) gives most height per unit horizontal distance and is used to clear obstacles.

Glide performance is essentially independent of weight in still air for best glide speed, but heavier aircraft glide faster and descend at a higher rate; best glide speed rises with weight.

Stall speed increases with the square root of load factor: at 60° bank the load factor is 2 g and stall speed is about 1.41 times the 1 g stall speed.

Climb performance falls with altitude because excess thrust falls; service ceiling is where the maximum climb rate is 100 ft/min, absolute ceiling where it is zero.

Performance charts are based on an aircraft in good condition with specified flap and power settings; add margins for runway slope, surface, contamination and pilot technique.

Maximum take-off weight (MTOW), maximum landing weight and maximum zero-fuel weight are separate limits; the most restrictive limit governs the load carried.

Empty weight includes unusable fuel, full oil, fixed ballast and trapped fluids; it excludes usable fuel, payload and crew where the manual defines it that way.

Moment = weight × arm; total moment divided by total weight gives the centre of gravity position in the same units as the arms.

C of G limits are expressed as a range of arms (or % MAC); the forward limit protects elevator authority and landing flare, the aft limit protects stability and stall recovery.

Adding weight ahead of the current C of G moves it forward; adding weight behind moves it aft; adding weight at the C of G leaves it unchanged.

Zero-fuel weight is the weight of the aircraft and its contents excluding usable fuel; it is checked to protect wing bending and structural limits.

Load sheet arithmetic: convert all arms to a common datum and units, sum weights and moments separately, then divide; a C of G error is usually an arithmetic or datum error.

Fuel burn shifts C of G: burning fuel from a tank ahead of the C of G moves it aft and vice versa; check the C of G at take-off and landing.

A current airworthiness certificate, registration, and (for New Zealand) the applicable maintenance documentation must be carried or available for the flight to be lawful.

The aircraft flight manual or pilot operating handbook is the approved source for limitations, normal and emergency procedures, and performance data.

Airworthiness directives are mandatory; an AD that is due before the next inspection grounds the aircraft regardless of other maintenance status.

Pre-flight inspection is the pilot's responsibility: check control surfaces, fuel and oil quantity and grade, tyre and brake condition, and any obvious damage or leaks.

Maintenance release or certification confirms the aircraft is serviceable after maintenance; the pilot must check it covers the work done and any deferred defects.

Defects found in flight are recorded in the technical log; the aircraft may only be flown again if the defect is cleared or the manual permits flight under a specified limitation.

Weight and balance data, equipment list and compass deviation card must reflect the aircraft's current configuration; modifications require updated documentation.

Special flight permits or ferry approvals are needed for flight with an unresolved airworthiness issue outside normal limits; they carry specific operating restrictions.

Pilot-performed preventive maintenance is limited to the tasks the regulator permits; anything else requires a licensed engineer and a maintenance release.

Electrical system: the battery supplies starting and emergency power; the alternator or generator carries normal load; an ammeter shows charge or discharge, and a discharge in flight means shedding load.

Fuel system: check quantity, grade and contamination before flight; sump drains remove water, and fuel-selector position must be confirmed and monitored in flight.

Vacuum system drives gyroscopic instruments; a vacuum failure is shown by the suction gauge and by the attitude and heading indicators becoming unreliable while the turn coordinator, if electric, remains valid.

The turn coordinator shows rate of turn and, by the ball, coordination; it does not show bank angle directly.

The altimeter setting must be updated to the local QNH; flying from high to low pressure or high to low temperature without resetting reads higher than actual.

Engine monitoring: exhaust gas temperature peaks near best-power mixture; leaning to peak EGT gives best economy, rich of peak gives best power and cooler cylinder heads.

Landing gear and flap systems have speed limits (VLE, VFE); exceeding them can damage structure or actuators even without immediate symptoms.

Anti-ice and de-ice systems consume engine power or electrical load; when activated, expect reduced performance and check the relevant system is actually working.

A pre-take-off instrument check includes ASI at zero, altimeter set to QNH, heading indicator aligned to the compass, and suction and fuel gauges in the normal range.