NZ CAA PPL Aircraft Technical key terms

An official NZ CAA document confirming an aircraft meets its approved type design and is safe to fly. It must be carried on board and remains valid only while maintenance and conditions are maintained.

A document recording the aircraft's registered owner and nationality marks. It identifies the aircraft legally but says nothing about its mechanical condition or fitness to fly.

A mandatory instruction issued by the state of design and adopted by NZ CAA requiring inspection, modification or limitation on a type. Compliance is compulsory and normally within a stated time or before further flight.

Technical advice from the manufacturer recommending inspection or modification. It is not automatically mandatory, but may become so if adopted by an airworthiness directive or the operator's maintenance programme.

A certification by an authorised person that specified maintenance has been completed and the aircraft is fit for flight within any stated limitations. It records what was done and by whom.

A scheduled comprehensive inspection of the aircraft, engine and systems carried out at least every twelve months by an appropriately rated engineer. It checks condition, security, wear and compliance with directives.

A requirement that certain critical maintenance tasks, such as control system assembly or flight control rigging, be independently checked and signed by a second qualified person to reduce the risk of undetected error.

The approved document for a specific aircraft containing limitations, operating procedures and performance data. It is legally binding, and the aircraft must not be operated outside its stated limits.

The boundaries within which an aircraft is certified to operate, covering speeds, weights, altitudes, load factors and systems use. They appear in the flight manual and marking placards and are legally binding.

A known fault that has been assessed and formally allowed to remain unrepaired for a defined period under approved procedures, with any operational restrictions noted. It must be recorded and tracked.

An approved document listing items of equipment that may be inoperative while the aircraft is still dispatched, subject to stated conditions and procedures. It applies to aircraft operated under the relevant rules.

The nationality and registration letters painted on the aircraft, such as ZK-xxx for New Zealand. They must be displayed in the prescribed size and positions so the aircraft can be identified.

The weight of the aircraft including structure, powerplant, fixed equipment, unusable fuel and full oil, but excluding usable fuel, crew, passengers and baggage. It is the starting point for loading calculations.

The greatest weight at which the aircraft is certified to begin the take-off run. Exceeding it degrades climb performance and may overstress the structure.

The difference between maximum take-off weight and empty weight. It represents the total allowance for fuel, oil beyond the fixed amount, crew, passengers and baggage.

The point at which the aircraft's total weight is considered to act. It must lie within the certified forward and aft limits for safe control and stability in all phases of flight.

The forward and aft positions within which the centre of gravity must remain for the aircraft to be controllable and stable. Operating outside them can make rotation, stall recovery or landing unsafe.

The horizontal distance from the reference datum to a point where a weight acts. Multiplying a weight by its moment arm gives its moment, which is used to locate the centre of gravity.

A fixed reference point or plane from which all moment arms are measured for weight and balance purposes. It is defined in the flight manual and may lie ahead of the aircraft nose.

Pressure altitude corrected for non-standard temperature. High density altitude reduces engine power, propeller thrust and lift, lengthening take-off runs and reducing climb rates.

The altitude indicated when the altimeter subscale is set to the standard datum of 1013.25 hPa. It is the basis for performance charts and for flight levels above the transition altitude.

The ratio of total lift to the aircraft's weight, expressed in g. It increases in turns and gusts, and the structure is certified to withstand stated positive and negative limits.

The maximum load the structure is designed to withstand without permanent deformation. Ultimate load is typically 1.5 times limit load, beyond which structural failure is possible.

The speed marked by the red radial line on the airspeed indicator, which must not be exceeded in any circumstances. Exceeding it risks structural damage or control reversal from flutter.

The maximum speed at which full deflection of a single primary control may be applied without exceeding the design load factor. Marked by the amber radial line and only valid at maximum weight.

The lowest speed at which the aircraft can maintain level flight in a given configuration before the wing exceeds its critical angle of attack. It increases with weight, load factor and forward centre of gravity.

The angle of attack at which the wing produces maximum lift and beyond which airflow separates and the wing stalls. It is a fixed value independent of weight, speed and density altitude.

The total ground and air distance needed to reach a defined height above the runway surface, allowing for pilot technique and conditions. It must be compared with the available distances before departure.

The primary structure of the aircraft excluding the powerplant, comprising fuselage, wings, empennage and landing gear. It carries and transmits all flight and ground loads.

The main longitudinal structural member of a wing that carries bending and shear loads from lift. It usually runs from root to tip and is the strongest part of the wing structure.

A chordwise structural member that gives the wing its aerofoil shape and supports the skin between spars. Ribs also transfer loads from the skin to the spars.

A transverse structural member within the fuselage that maintains shape and carries concentrated loads, such as engine mounts or landing gear attachments, into the surrounding skin.

A longitudinal fuselage member that, together with the skin and frames, carries bending loads along the length of the body. It differs from a spar, which is a wing member.

The operating sequence of a reciprocating engine: induction, compression, power and exhaust, completed in two crankshaft revolutions. Each cylinder fires once per cycle.

A self-contained engine-driven ignition unit that generates high-voltage pulses for the spark plugs without relying on the aircraft battery. Two magnetos provide independent ignition redundancy.

Ice formation in the carburettor venturi caused by fuel vaporisation and pressure drop cooling. It can occur at outside air temperatures well above freezing and causes progressive power loss.

A propeller whose blade angle is automatically varied by a governor to maintain a selected engine speed. It improves efficiency across the flight envelope compared with a fixed-pitch propeller.

The absolute pressure in the engine induction system, shown on a gauge in inches of mercury. It indicates the power being developed by a constant-speed propeller engine at a given rpm.

The pressure system supplying the airspeed indicator, altimeter and vertical speed indicator. The pitot tube senses ram air pressure, while the static port supplies ambient pressure.

An instrument comparing pitot ram pressure with static pressure to display indicated airspeed. Its coloured markings show stall, flap, manoeuvring and never-exceed speed ranges.

A pressure instrument displaying altitude by measuring static pressure against a selected subscale setting. Correct subscale setting is essential for terrain clearance and accurate level information.

A blockage that traps static pressure in the instrument lines. The altimeter then freezes, the vertical speed indicator stops responding and the airspeed indicator reads incorrectly, often like a climb.

Flight instruments relying on a spinning rotor, including the attitude indicator, heading indicator and turn coordinator. They provide attitude, heading and rate-of-turn information independent of outside visibility.

A gyroscopic instrument showing pitch and roll relative to the horizon. It is the primary reference for aircraft attitude in instrument flight and must be checked and caged where applicable before flight.

A gyroscopic instrument displaying aircraft heading, typically driven by a gyro rather than a magnetic sensor. It must be aligned with the magnetic compass periodically because it drifts in flight.

A simple magnetic instrument indicating the aircraft's heading relative to the earth's magnetic field. It is subject to turning and acceleration errors and is used to check the heading indicator.