CAA NZ CPL Theory - Principles of Flight & Aircraft Performance flashcards

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

Induced drag relationship

Induced drag equals ½ρV²S times CL squared divided by πAe. At constant weight it varies inversely with the square of speed, so it dominates at low speed and high angle of attack.

Minimum drag speed

Occurs where parasite drag equals induced drag, at CL equal to the square root of CD0 times πAe. Minimum power speed is about 0.76 of this speed.

Load factor in level turn

Load factor equals one divided by cosine of the bank angle. At 60 degrees bank the load factor is 2, so stall speed rises by the square root of 2, about 41 percent.

Critical angle of attack

The angle at which the wing stalls regardless of weight, speed, bank or density altitude. Recovery requires reducing the angle of attack, not adding power alone.

Adverse yaw

Yaw away from the turn caused by higher induced drag on the rising, slower-moving wing. Coordinated rudder or aileron differential counters it and prevents slipping.

Mach crit

Free-stream Mach number at which local airflow over some part of the wing first reaches Mach one. Sweep, thin sections and high altitude all reduce the margin before shock stall.

Static margin

Distance between the CG and the aerodynamic centre, expressed as a fraction of mean chord. A larger positive margin gives stronger pitch stability but heavier stick forces.

Density altitude formula

Density altitude equals pressure altitude plus 120 times the difference between outside air temperature and ISA temperature at that pressure altitude, in degrees Celsius.

V1 decision speed

Speed by which a rejected take-off must be initiated. It must be at least VMCG and no greater than VR so that rotation remains possible after engine failure.

Balanced field length

Field length achieved when V1 is selected so accelerate-stop distance equals accelerate-go distance. It minimises the runway needed for a given weight.

Climb gradient calculation

Gradient percent equals rate of climb in feet per minute multiplied by 60, divided by groundspeed in knots times 6076, then multiplied by 100.

Service ceiling

Altitude at which maximum rate of climb falls to 100 feet per minute. The absolute ceiling is where rate of climb reaches zero.

Crosswind component

Wind speed multiplied by the sine of the angle between wind direction and runway heading. The headwind component uses the cosine of the same angle.

Screen height

Height above the runway threshold, normally 50 feet, from which landing distance is measured to a full stop under AFM reference conditions.

Take-off distance factors

Distance increases roughly 10 percent per 1000 feet of density altitude and about 10 percent for each 10 percent weight increase above the AFM reference weight.

Moment calculation

Moment equals weight multiplied by arm measured from the datum. Total moment divided by total weight gives the centre of gravity arm.

Weight shift formula

Change in CG equals weight moved multiplied by distance moved, divided by total aircraft weight. Moving weight aft moves the CG aft proportionally.

Adding weight effect

New CG equals old total moment plus added moment, divided by old total weight plus added weight. Adding weight aft of the CG moves it aft.

Maximum zero fuel weight

Structural limit on weight excluding usable fuel. Payload must be reduced when fuel plus basic weight would otherwise exceed this limit before take-off.

Forward CG effects

Increases longitudinal stability and elevator authority demand, lengthens take-off run, raises stall speed slightly and can limit flare authority on landing.

Percentage MAC

CG position expressed as a percentage of mean aerodynamic chord: CG arm minus leading edge MAC arm, divided by MAC length, multiplied by 100.

Aft CG hazard

Reduces static stability and stick force per g, can cause pitch-up or deep stall, and shortens the recoverable margin in turbulence or spin.

CG envelope shape

Forward and aft limits vary with weight. The forward limit is often set by elevator authority and the aft limit by stability, so both must be checked at each loading.

Fuel plan components

Trip fuel, taxi fuel, contingency, alternate fuel, final reserve and any additional fuel. The sum must not exceed usable capacity after allowing for taxi burn.

Final reserve fuel

Thirty minutes at holding speed for VFR, or thirty minutes at 1500 feet above the alternate for IFR. It is not planned for use in normal operations.

Specific range

TAS in nautical miles per hour divided by fuel flow in kilograms per hour. Maximum specific range occurs at the tangent from the origin to the power-required curve.

Endurance and range

Endurance equals usable fuel divided by fuel flow. Range equals TAS multiplied by endurance, then corrected for headwind or tailwind component.

Avgas mass conversion

One imperial gallon of avgas weighs about 6.7 pounds or 3.04 kilograms. One kilogram equals 2.2046 pounds, so conversions must be consistent throughout the plan.

Groundspeed calculation

True airspeed plus tailwind component or minus headwind component. Time en route equals distance divided by groundspeed, expressed in the same units.

Normal category limits

Limit load factors of plus 3.8 and minus 1.52 g up to design cruising speed, reducing to plus 2.5 g at never-exceed speed.

Manoeuvring speed VA

Speed above which full deflection of a single control can overstress the structure. It decreases with the square root of weight, so it is lower at lighter weights.

Turbulence penetration speed

Normally VB or below VA. It gives margin against gust loads while retaining enough speed to avoid stall in the gust encounter.

Operational weight limits

Maximum take-off, landing, zero fuel and ramp weights each apply to a different phase. The lowest applicable limit governs the planned loading.