CAA NZ CPL Theory - Principles of Flight & Aircraft Performance key terms

The angle between the wing's chord line and the relative airflow. Increasing AoA raises lift up to the critical angle, beyond which the wing stalls.

The specific angle of attack at which airflow separates from the wing and lift drops sharply. It is fixed for a given aerofoil and is reached at any speed if AoA is excessive.

A condition where the wing exceeds its critical angle of attack, causing airflow separation and a sudden loss of lift. It can occur at any speed, attitude or weight.

The minimum indicated airspeed at which the aircraft can maintain level flight before exceeding the critical angle of attack. It increases with weight, load factor and forward centre of gravity.

The ratio of total lift to the aircraft's weight, expressed in g. Higher load factors increase stall speed and structural stress during manoeuvres or turbulence.

The maximum speed at which full control deflection will not overstress the airframe. Above VA, abrupt control inputs risk structural damage; below VA, the wing stalls before structural limits are reached.

The maximum speed the aircraft may be operated at in any condition. Exceeding VNE risks structural failure or flutter and is prohibited.

A dangerous high-speed vibration caused by aerodynamic forces coupling with structural flexibility. It can rapidly damage or destroy control surfaces and is avoided by respecting VNE.

The direction of the air flowing past the aircraft, opposite to the flight path. Angle of attack is measured between the chord line and this airflow.

A straight line drawn from the leading edge to the trailing edge of an aerofoil. It is the reference for measuring angle of attack and incidence.

The fixed angle between the wing chord line and the aircraft's longitudinal axis. It is set by the manufacturer and differs from angle of attack.

Drag caused by the generation of lift, strongest at high angles of attack and low speeds. It decreases as speed increases.

Drag from skin friction and form drag, increasing with the square of airspeed. It is highest at high speed and reduced by streamlining.

The ratio of lift to drag at a given angle of attack. The best ratio gives the maximum glide distance and occurs at a specific speed for each weight.

The horizontal distance an aircraft travels per unit of altitude lost in a glide. It is numerically equal to the lift/drag ratio and is affected by weight, wind and configuration.

The speed that gives the greatest glide distance in a power-off descent. It varies with weight and should be adjusted for headwind or tailwind.

The point where the aircraft's total weight is considered to act. Its position affects stability, stall speed and control effectiveness, and must remain within approved limits.

The forward and aft boundaries within which the CG must remain for safe flight. Exceeding them can cause loss of control or excessive stability.

The process of calculating the aircraft's total weight and CG position to ensure they fall within approved limits before flight.

The maximum weight at which the aircraft is certified to begin take-off. It is a structural and performance limit that must not be exceeded.

The maximum weight at which the aircraft may land. Exceeding it may require a fuel dump or holding to reduce weight before landing.

The difference between maximum take-off weight and empty weight. It includes crew, passengers, baggage, fuel and removable equipment.

The weight of passengers, cargo and baggage that generates revenue. It is part of useful load but excludes fuel and crew.

Pressure altitude corrected for non-standard temperature. High density altitude reduces engine power, propeller thrust and lift, increasing take-off and landing distances.

The altitude indicated when the altimeter subscale is set to 1013.2 hPa. It is used for flight levels and performance calculations.

The altimeter setting that makes the altimeter read elevation above mean sea level when on the ground. It is used for take-off and landing performance.

The distance required from brake release to reaching a specified height, typically 50 feet. It increases with weight, altitude, temperature and tailwind.

The distance required from crossing a specified height, usually 50 feet, to a full stop. It increases with weight, altitude, temperature and tailwind.

The component of wind blowing directly along the runway opposite to the aircraft's take-off or landing direction. It reduces ground speed and shortens take-off and landing distances.

The component of wind blowing in the same direction as the aircraft's take-off or landing run. It increases ground speed and lengthens take-off and landing distances.

The component of wind blowing across the runway. It must not exceed the aircraft's demonstrated crosswind limit and affects directional control during take-off and landing.

The minimum fuel required beyond trip fuel for contingencies, alternate, holding and final reserve. They ensure safe completion if conditions change.

The fuel required from take-off to landing at the destination, including taxi, climb, cruise and descent. It is the basis for calculating total fuel.

Fuel carried in addition to trip fuel to cover unforeseen factors such as weather, routing changes or increased consumption. It is typically a percentage of trip fuel.

The minimum fuel that must remain at the end of a flight, usually sufficient for 30 minutes of holding at 1,500 feet. It is not planned for use.

The fuel burned per unit of power or thrust per unit time. It is used to calculate fuel flow and trip fuel for a given power setting.

The weight of the aircraft and its contents excluding usable fuel. It is a structural limit that must not be exceeded before fuel is added.

The maximum weight of the aircraft and payload without usable fuel. It protects the wing structure from excessive bending moments.

The horizontal distance from the datum to a weight's centre of gravity. It is used with weight to calculate moments for CG determination.

The product of a weight and its arm, representing its turning effect about the datum. Summing moments and dividing by total weight gives the CG position.