CAA NZ ATPL Theory - Advanced Aerodynamics, Performance and Systems Knowledge key terms

The free-stream Mach number at which airflow somewhere on the airframe first reaches Mach 1, producing a shock wave and the onset of wave drag.

A nose-down pitching tendency at high subsonic Mach numbers, caused by rearward movement of the centre of pressure and loss of downwash over the tailplane.

Separation of the boundary layer behind a shock wave on the wing, causing buffet, loss of lift and possible control reversal at high Mach numbers.

The narrow band of altitude and speed where low-speed stall margin and high-speed buffet margin converge, leaving little usable airspeed range.

An automatic system that repositions the elevator or trims the stabiliser as Mach number rises, countering the nose-down pitch caused by transonic centre-of-pressure shift.

Rearward angling of the wing leading edge, which reduces the chordwise component of airflow and so raises the critical Mach number and delays shock formation.

Drag arising from the generation of lift, caused by the rearward inclination of lift over a wing with finite span; it increases with angle of attack and decreases with speed.

The total of induced drag and trim drag, the portion of drag that varies with the lift coefficient and therefore with aircraft weight and load factor.

Drag caused by the pressure difference between the front and rear of a body, dependent on its shape and frontal area rather than skin friction.

The sum of form drag and skin-friction drag, rising with the square of true airspeed and independent of the lift produced.

Small fixed vanes that energise the boundary layer with turbulent air, delaying separation and improving control effectiveness or buffet margins at high altitude or high Mach.

The thin layer of air next to a surface in which velocity rises from zero at the skin to the free-stream value, and where skin friction and separation originate.

The tendency of an aircraft, after a disturbance, to develop forces that return it toward its original equilibrium condition; positive static stability is a prerequisite for dynamic stability.

The centre-of-gravity position at which the aircraft has zero static longitudinal stability, because the centre of gravity coincides with the aerodynamic centre of the whole aircraft.

The distance between the centre of gravity and the neutral point, usually expressed as a percentage of mean aerodynamic chord; larger margin means greater pitch stability but more trim drag.

A long-period, lightly damped longitudinal oscillation in which the aircraft alternately trades altitude and airspeed while angle of attack stays roughly constant.

A coupled lateral-directional oscillation in which the aircraft alternately yaws and rolls, typically poorly damped when directional stability is weak relative to dihedral effect.

An automatic system that senses yaw rate and drives the rudder to suppress Dutch roll, allowing flight at higher altitude where natural damping is reduced.

The chord of a hypothetical rectangular wing with the same area and pitching moment as the real wing; centre-of-gravity limits are quoted as percentages of it.

The forward and aft boundaries within which the loaded centre of gravity must lie, set so that both pitch authority and stability requirements are satisfied throughout flight.

The mass of the aircraft with unusable fuel and oil, plus fixed equipment, optional equipment and crew, as defined in the aircraft's mass and balance documentation.

The basic empty mass plus crew, crew baggage, catering and removable passenger service equipment; the starting point for operational mass calculations.

Dry operating mass plus take-off fuel, representing the aircraft mass at brake release with no traffic load on board.

The total mass of passengers, baggage and cargo carried, found by subtracting operating mass from take-off mass.

The mass of the aircraft with all traffic load and usable fuel removed; it must not exceed the maximum zero fuel mass, which protects the wing structure.

The take-off mass permitted after applying performance limitations such as runway length, obstacle clearance, climb gradient and tyre-speed limits, which may be below the structural limit.

The runway length at which the accelerate-stop distance equals the take-off distance to 35 ft with one engine failed, giving the most limiting take-off mass.

The decision speed: the maximum speed at which a rejected take-off can be initiated and the aircraft stopped within the remaining runway, and the minimum speed for continuing after engine failure.

Take-off safety speed, the minimum speed to be attained by 35 ft with one engine inoperative, providing the required climb gradient and directional control.

Certificated airspeed limitations such as VA, VFE, VLE, VMO and VNE that define structural, flap, gear and Mach limits for the aircraft.

The take-off run available plus any clearway, being the length declared for calculating the distance to reach 35 ft above the take-off surface.

The distance flown per unit of fuel consumed, determined by the ratio of true airspeed to fuel flow; maximised in the cruise at the speed for best lift-to-drag ratio.

The time an aircraft can remain airborne on a given quantity of fuel, maximised at the speed for minimum power required rather than minimum drag.

The altitude at which the maximum rate of climb falls to a defined low value, typically 100 ft/min for turbine aircraft, beyond which further climb is impractical.

A descent procedure flown after an engine failure or decompression at high altitude, at a speed and configuration giving the greatest distance or least fuel to a suitable alternate.

The pressure difference between cabin and ambient air that the fuselage structure is designed to withstand, setting the maximum cabin altitude and aircraft operating ceiling.

A valve that modulates the rate at which cabin air escapes to atmosphere, thereby controlling cabin altitude and rate of climb or descent.

Thermal, chemical or pneumatic systems that prevent ice formation on protected surfaces or remove ice already formed, with associated airframe and engine power penalties.

A control system in which pilot inputs are converted to electrical signals processed by computers that command hydraulic actuators, enabling envelope protection and normal-law reversion.