IDAC Private Pilot Airplane (PPA) key terms

The minimum flight visibility and distance from cloud that a VFR flight must maintain in a given airspace class, set by the state; breach can invalidate the flight and expose the pilot to enforcement action.

Airspace of defined dimensions within which air traffic control service is provided to IFR flights and, where prescribed, to VFR flights; classes A to E in the ICAO system, with entry normally requiring a clearance.

An authorisation from air traffic control for a flight to proceed under specified conditions; it is not an instruction to the pilot to accept an unsafe situation, and the pilot remains responsible for separation from terrain and traffic see-and-avoid.

A clearance allowing a VFR flight to operate inside a control zone when weather is below normal VFR minima, subject to stated visibility, cloud and ground-visibility conditions and usually at the pilot's request.

Controlled airspace extending upwards from the surface to a specified upper limit around an aerodrome, protecting approach and departure paths; VFR entry normally requires a clearance and compliance with local minima.

The pilot's repetition of safety-related ATC instructions and clearances, such as route, level, heading and frequency, to confirm correct reception; failure to read back correctly is a recognised cause of altitude and route deviations.

A radio transmission giving the aircraft's identification, position, time, altitude and next position or estimate, used where surveillance coverage is absent; accuracy depends on correct map reading and timing.

The point through which the total weight of the aircraft acts; its position along the chord must stay within the certified forward and aft limits for control authority, stability and performance to remain acceptable.

The horizontal distance from a reference datum to a mass item; multiplying each mass by its arm gives its moment, and dividing total moment by total mass yields the loaded centre of gravity position.

The mass of the aircraft as delivered plus optional equipment, unusable fuel and full operating fluids including engine oil; the starting figure from which payload, fuel and baggage are added in a load sheet.

The highest mass at which the aircraft is certified to begin the take-off run; exceeding it degrades climb gradient, increases take-off distance and may overstress structure, so it is checked before every departure.

Pressure altitude corrected for non-standard temperature; high density altitude reduces air density, so engine power, propeller thrust and wing lift all fall while true airspeed and take-off distance increase.

Indicated altitude when the altimeter subscale is set to the standard pressure 1013.25 hPa; used for flight levels above the transition altitude and as the input for performance charts.

The altitude above which a pilot sets the standard pressure reference and reports flight levels instead of altitudes; it varies by state and aerodrome and is published on approach and en-route charts.

A surface of constant pressure shown as a three-digit number, being pressure altitude in hundreds of feet with the standard pressure set; levels are separated by a semi-circular rule based on magnetic track.

Navigation by calculating the heading and time needed to follow a planned track, using forecast wind and true airspeed, then correcting for observed drift; the foundation for all other navigation methods.

The vector relationship between true airspeed and heading, wind velocity, and resulting ground speed and track; solving it gives the heading to steer and the time to the next waypoint.

The angle between true north and magnetic north at a given place, east or west of true; it is applied when converting between true and magnetic directions and changes slowly with position and time.

The error of a magnetic compass caused by the aircraft's own magnetic fields and electrical equipment; it is unique to each installation and read from a calibration card to convert magnetic heading to compass heading.

A magnetic bearing from a VOR station, selected on the omni-bearing selector; the course deviation indicator shows whether the aircraft is left or right of that radial and the TO/FROM flag resolves ambiguity.

Distance measuring equipment that times the round trip of interrogations to a paired ground station and displays slant range in nautical miles; error grows with altitude and proximity to the station.

Global navigation satellite systems providing position, track and ground speed to certified airborne receivers; used for en-route and approach navigation, with integrity monitoring and database currency being pilot responsibilities.

A reference model with sea-level pressure 1013.25 hPa, temperature 15 degrees Celsius and a lapse rate of about 2 degrees Celsius per 1000 feet, used to standardise altimeter and performance calculations.

The altimeter subscale setting that makes the instrument read aerodrome elevation when on the ground; with QNH set, the altimeter indicates height above mean sea level.

The altimeter subscale setting that makes the instrument read zero on the aerodrome reference point; with QFE set, the altimeter indicates height above that point, useful for circuit and threshold heights.

Accretion of ice on airframe or engine components in supercooled cloud or freezing rain; airframe ice adds weight and destroys lift, while carburettor ice can strangle a piston engine at above-freezing temperatures.

Ice forming in the carburettor venturi as fuel vaporisation and pressure drop cool the mixture, most likely at high humidity and temperatures between roughly minus 10 and plus 20 degrees Celsius; prevented by carburettor heat.

The altitude at which the air temperature reaches zero degrees Celsius; above it, visible moisture occurs as supercooled droplets, so it marks the lower boundary of serious airframe icing risk.

The three stages of cumulonimbus development: cumulus with updraughts, mature with both updraughts and downdraughts plus rain and lightning, and dissipating with downdraughts; the mature stage is most hazardous.

A change of wind speed or direction over a short distance or time, especially hazardous as a microburst or frontal shear at low level; it can cause sudden airspeed loss and a stall close to the ground.

The angle between the wing chord line and the relative airflow; lift rises with it until the critical angle, beyond which the airflow separates and the wing stalls regardless of airspeed or attitude.

Loss of lift caused by exceeding the critical angle of attack; the nose may drop, controls feel light and buffet may occur, and recovery requires reducing angle of attack, typically by easing forward pressure.

The ratio of total lift to weight, expressed in g; it increases in turns and pull-ups, raising the speed at which the wing reaches its critical angle of attack and therefore the stall speed.

Drag caused by the generation of lift, produced mainly by wingtip vortices; it is greatest at high angle of attack and low speed, so it decreases as speed increases, opposite to parasite drag.

The speed giving the greatest distance per unit of height lost in a power-off glide, found where total drag is minimum; it increases with mass and is used to plan the forced-landing field.

Insufficient oxygen reaching body tissues, causing impaired judgement, euphoria and loss of colour vision before unconsciousness; in aviation it arises from altitude, often without the pilot noticing symptoms.

Overbreathing that lowers blood carbon dioxide, producing dizziness, tingling and cramps that mimic hypoxia; treatment is conscious control of breathing rate, and the two conditions must be told apart in flight.

The period after loss of oxygen supply during which a person can still take effective corrective action; it shortens rapidly with altitude and is a planning factor for unpressurised high-altitude flight.

A false perception of the aircraft's attitude or motion caused by misleading vestibular and visual cues in the absence of a clear horizon; the remedy is to believe the instruments and fly by reference to them.

A somatogravic illusion in which a sustained acceleration or deceleration is felt as a climb or descent, tempting the pilot to pitch the wrong way; it is common on take-off and go-around and is countered by instrument reference.

A gyroscopic instrument showing pitch and bank relative to the horizon; it is the primary reference for attitude in instrument conditions, provided its gyro has spun up and is not tumbled or failed.

An instrument showing rate of turn and slip or skid via a ball in a curved tube; in a balanced turn the ball stays centred, and the instrument supports partial-panel flying and coordination practice.

The cockpit control that sets fuel-to-air ratio; it is leaned as altitude increases to restore power and economy, and enriched for take-off, climb and high power settings to control cylinder temperature.

The systematic walk-around and cockpit checks before flight, covering control surfaces, fuel quantity and contamination, oil, tyres, documents and required equipment, with defects resolved or deferred per the minimum equipment list.

Calculating usable fuel for trip, taxi, contingency, alternate and final reserve, then comparing it with capacity; it also verifies that take-off and landing masses stay within limits for the planned fuel load.

The pre-flight computation confirming that take-off and landing masses lie within limits and the centre of gravity falls inside the certified envelope for the actual fuel, occupants and baggage loaded.