NZ CAA PPL Aircraft Technical flashcards

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

Stoichiometric mixture ratio

The chemically correct fuel-to-air mass ratio, about 1:15 for aviation gasoline, at which all fuel and oxygen are consumed. Best power needs a slightly richer mixture.

Detonation versus pre-ignition

Detonation is explosive uncontrolled combustion after normal ignition; pre-ignition is ignition before the spark. Both raise cylinder head temperature and can damage the engine.

Carburettor icing conditions

Most likely with outside air temperature between about -7 °C and +21 °C and high humidity, including clear air. Indicated by unexplained RPM or manifold pressure loss.

Magnetometer versus magneto

A magneto is an engine-driven ignition source independent of the electrical system; a magnetometer is a sensor that measures magnetic heading for a remote compass system.

Static port blockage effects

The altimeter freezes, the vertical speed indicator reads zero, and the airspeed indicator behaves like an altimeter, over-reading in a climb and under-reading in a descent.

Gyroscopic instrument drive

Attitude and heading indicators are usually vacuum-driven; the turn coordinator is usually electric. Loss of suction makes the vacuum instruments unreliable while the turn coordinator remains valid.

Density altitude definition

Pressure altitude corrected for non-standard temperature. It is the altitude the aircraft performs at, and high values reduce power, thrust and lift.

Best angle of climb VX

The speed giving the greatest height gain per unit horizontal distance. Used to clear obstacles after take-off; it is lower than best rate of climb speed.

Best rate of climb VY

The speed giving the greatest height gain per unit time. Used for the fastest climb to altitude; it decreases with altitude until it equals VX at the absolute ceiling.

Load factor and stall speed

Stall speed rises with the square root of load factor. At 60 degrees bank the load factor is 2 g, so stall speed is about 1.41 times the 1 g value.

Service ceiling

The altitude at which the maximum climb rate falls to 100 feet per minute. The absolute ceiling is where the maximum climb rate is zero.

Headwind and take-off distance

A headwind reduces ground roll and landing distance; a tailwind increases both. Use the chart's wind component and add a margin for gusts and technique.

Weight effect on take-off

Higher weight increases take-off and landing distance, reduces climb rate and raises stall speed. A 10 percent weight increase typically adds about 20 percent to take-off distance.

Best glide speed and weight

Best glide speed increases with weight, and a heavier aircraft descends at a higher rate. Glide angle in still air is essentially unchanged by weight.

Moment calculation

Moment equals weight multiplied by arm, measured from the datum. Summing moments and dividing by total weight gives the centre of gravity position.

Centre of gravity forward limit

The most forward permitted C of G. It protects elevator authority for rotation, flare and stall recovery; exceeding it can make the aircraft hard to flare.

Centre of gravity aft limit

The most aft permitted C of G. It protects static and dynamic stability and stall recovery; exceeding it makes the aircraft unstable and spin-prone.

Maximum zero-fuel weight

The maximum weight of the aircraft and contents excluding usable fuel. It protects wing bending and structural limits and is checked separately from take-off weight.

Empty weight contents

Empty weight includes the airframe, unusable fuel, full oil, fixed ballast and trapped fluids. It excludes usable fuel, payload and, depending on definition, crew.

Fuel burn and C of G shift

Burning fuel from a tank ahead of the C of G moves the C of G aft; burning from a tank behind moves it forward. Check the C of G at take-off and landing.

Datum and arm

The datum is the fixed reference point from which arms are measured, usually in inches or millimetres. The arm is the horizontal distance from datum to a weight.

Airworthiness directive

A mandatory instruction issued to correct an unsafe condition. An AD due before the next inspection grounds the aircraft regardless of other maintenance status.

Maintenance release

Certification that specified maintenance has been completed and the aircraft is serviceable. The pilot should confirm it covers the work and any deferred defects.

Aircraft flight manual role

The approved source of limitations, normal and emergency procedures and performance data. Operating outside its limitations is not permitted.

Technical log defect entry

A record of defects found in flight or on the ground. The aircraft may fly again only if the defect is cleared or the manual permits flight under a stated limitation.

Pre-flight inspection scope

The pilot's check of control surfaces, fuel and oil quantity and grade, tyres, brakes, leaks and obvious damage. It is required before every flight.

Compass deviation card

A card showing residual compass errors on given headings. It must reflect the aircraft's current configuration and be used when aligning the heading indicator.

Pilot preventive maintenance limits

Only tasks the regulator permits may be done by the pilot. Anything else requires a licensed engineer and a maintenance release before flight.

Ammeter discharge in flight

A sustained discharge shows the alternator or generator is not supplying load. Shed electrical equipment and plan to land before the battery is exhausted.

Exhaust gas temperature leaning

EGT peaks near best-power mixture. Leaning to peak EGT gives best economy; operating rich of peak gives best power and cooler cylinder heads.

Turn coordinator indication

It shows rate of turn and, through the ball, coordination. It does not directly show bank angle, unlike the attitude indicator.

Altimeter setting drift

Flying from high to low pressure or high to low temperature without resetting makes the altimeter read higher than actual altitude, reducing terrain clearance.

VFE and VLE

VFE is the maximum flap extended speed; VLE is the maximum landing gear extended speed. Exceeding either can damage structure or actuators without immediate symptoms.