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

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Induced drag formula

CDi = CL²/(π·A·e). Induced drag falls as speed rises because CL falls, and it dominates total drag at low speed and high load factor.

Minimum drag speed

The speed where parasite drag equals induced drag; it is the best glide speed in still air and the speed for maximum endurance.

Load factor in a turn

n = 1/cos φ for a level turn. Stall speed rises by √n, so a 60° bank increases stall speed by about 41%.

Critical Mach number

The free-stream Mach number at which airflow somewhere on the aircraft first reaches Mach 1, causing local shock waves and the onset of wave drag.

Drag divergence Mach number

The Mach number above Mcrit at which drag coefficient rises steeply with increasing Mach, producing Mach buffet and control changes.

Boundary layer separation

Detachment of the retarded boundary layer from the surface, causing loss of lift and stall; it occurs when the adverse pressure gradient is too strong.

Best range speed

The speed giving maximum distance per unit fuel; for a piston aircraft roughly 1.3 times Vmd, and for a jet near maximum L/D speed.

Aspect ratio effect

Higher aspect ratio reduces induced drag for a given lift coefficient, improving climb and range but increasing structural bending loads and wing weight.

Density altitude

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

Balanced field length

The runway length for which accelerate-stop distance equals accelerate-go distance to 35 ft, defining the V1 that maximises allowable take-off weight.

Climb gradient formula

Gradient percent = (rate of climb ÷ ground speed) × 100, with both in the same units; for example 500 ft/min at 100 kt gives about 4.9%.

V1 definition

The take-off decision speed at which a failure leaves enough runway to stop or enough performance to continue safely; it is chosen before take-off.

Landing distance factors

Landing distance increases with weight, tailwind, downslope, high temperature and contaminated runway, and is measured from 50 ft to a full stop.

Specific range

Air nautical miles flown per unit of fuel consumed; maximised at the best range speed, which shifts with wind and altitude.

Endurance versus range

Endurance is maximum time aloft near Vmd; range is maximum distance at a higher speed. They are different optima and must not be confused.

Wind effect on range

A headwind increases the still-air speed for best range, while a tailwind reduces it, because wind changes ground speed per unit fuel.

Runway slope effect

An upslope increases take-off ground roll and reduces landing distance; roughly 1% upslope adds about 10% to the take-off run.

Constant-speed propeller

The governor adjusts blade pitch to absorb engine power at a selected RPM; rising airspeed tends to reduce blade angle of attack until pitch coarsens.

Turbocharger critical altitude

The altitude above which the turbocharger can no longer maintain rated manifold pressure, so engine power begins to decrease with further climb.

Detonation versus pre-ignition

Detonation is explosive uncontrolled combustion after the spark; pre-ignition is ignition before the spark. Both cause high cylinder pressures and temperatures.

Carburettor icing range

Most likely at ambient temperatures between about −10 °C and +10 °C with high humidity; venturi cooling allows ice to form above freezing.

Vacuum pump failure

Loss of the vacuum pump disables the attitude indicator and heading indicator; the turn coordinator and pitot-static instruments remain usable.

Blocked pitot effects

A blocked pitot with open static makes the airspeed indicator behave like an altimeter, reading higher in the climb and lower in the descent.

Blocked static effects

A blocked static source makes the altimeter freeze, the VSI read zero and the airspeed indicator over-read in the climb and under-read in the descent.

Hydraulic accumulator

A pressure vessel that damps pressure surges, stores hydraulic energy and supplies emergency pressure if the pump fails.

Unusable fuel

Fuel that cannot be safely supplied to the engine in all flight attitudes; it is excluded from the usable fuel figure used in flight planning.

CG calculation

Total moment is the sum of each weight times its arm; CG position equals total moment divided by total weight, measured from the datum.

Percent MAC formula

%MAC = (CG distance from leading edge − LEMAC) ÷ MAC × 100, used to check the CG against the certified fore and aft limits.

CG shift formula

A mass moved a distance shifts the CG by (mass × shift) ÷ total mass; the same formula applies to ballast, cargo or passenger relocation.

Zero fuel mass

Operating empty mass plus traffic load, excluding fuel; it must not exceed MZFM, which limits wing bending with fuel in the wings.

Forward CG effects

A forward CG increases stability but raises stall speed, elevator forces and take-off run, and may reduce range.

Basic empty mass

The aircraft mass including unusable fuel, full oil and standard equipment but excluding crew, payload and usable fuel; the basis for all mass calculations.