JCAA PPL Theory key terms

A mandatory instruction issued by a state authority requiring inspection, modification, or limitation of an aircraft or component, usually to correct an unsafe condition. Compliance is compulsory and often must be recorded in the aircraft logbooks.

A document confirming that an individual aircraft conforms to its approved type design and is considered safe for flight under specified conditions. It remains valid only while maintenance, equipment, and operating limitations are met.

The document that records the state of registry, the aircraft's nationality and registration marks, and the identity of the owner or operator. It must be carried on board or otherwise available as required by the state of registry.

A set of operating and navigation rules under which the pilot is responsible for seeing and avoiding other traffic and must remain clear of cloud in specified weather minima. It includes minimum visibility and distance-from-cloud requirements.

Weather conditions equal to or better than the prescribed visibility and cloud-clearance minima that allow flight under visual flight rules. When conditions fall below these minima, the flight becomes instrument meteorological conditions.

Weather conditions below the prescribed visual minima, in which flight under visual flight rules is not permitted. Flight in IMC requires an instrument rating, an instrument-equipped aircraft, and an instrument flight plan where applicable.

Airspace of defined dimensions within which air traffic control service is provided and within which some or all aircraft may be subject to control clearance requirements. It is classified into categories with different rules and equipment requirements.

An authorization issued by an air traffic control unit for an aircraft to proceed under specified conditions. It is not a guarantee of separation from terrain, obstacles, or all other traffic unless explicitly stated.

A four-digit octal code selected on the aircraft transponder to identify the aircraft on secondary surveillance radar. A specific code may be assigned by air traffic control or selected according to published procedures.

An authorization that allows a flight under visual flight rules within a control zone when weather is below normal visual minima but certain visibility and cloud-clearance conditions are met. It is granted by air traffic control on request.

Controlled airspace extending upwards from the surface around an aerodrome, established to protect arriving and departing traffic. Entry normally requires a clearance, and specific weather minima apply to visual flights.

The point at which the total weight of the aircraft is considered to act. Its position must remain within a certified forward and aft range for safe control and performance throughout the flight.

The calculation confirming that the aircraft's total mass and the position of its center of gravity remain within approved limits for the planned loading. It accounts for empty weight, fuel, occupants, baggage, and cargo.

The horizontal distance from a reference datum to the point where a weight acts. Multiplying a weight by its moment arm gives a moment, and summing moments locates the center of gravity.

The highest total mass at which the aircraft is certified to begin the takeoff run. It may be limited by structural strength, runway length, climb performance, or obstacle clearance on the day.

The altitude in the standard atmosphere at which the air density equals the actual density at the aircraft's location. High temperature, high elevation, and high humidity raise density altitude and degrade performance.

The altitude indicated on an altimeter set to the standard pressure of 1013.25 hPa. It is used for performance calculations and for flight above the transition altitude.

The angle between the wing chord line and the relative airflow approaching the wing. Increasing it raises lift up to the critical angle, beyond which the airflow separates and the wing stalls.

The angle of attack at which the wing reaches maximum lift coefficient and any further increase causes a stall. It is essentially constant regardless of weight, speed, or bank angle.

Drag created as a by-product of lift, caused by the pressure difference between the upper and lower wing surfaces producing wingtip vortices. It decreases with increasing speed and increases with higher lift coefficients.

A dimensionless number describing how effectively a wing generates lift at a given angle of attack and configuration. It rises with angle of attack until the critical angle, where it reaches its maximum.

The initial tendency of an aircraft, after a disturbance, to return toward, move away from, or remain at its original equilibrium condition. Positive static stability is a prerequisite for positive dynamic stability.

The upward angle of the wings relative to the horizontal. It produces a lateral component of lift during sideslip, creating a rolling moment that tends to level the wings and contributes to lateral stability.

The tendency of an aircraft to yaw away from the direction of a roll, caused by increased induced drag on the down-going wing. It is counteracted with coordinated rudder input.

The minimum airspeed at which an aircraft can maintain level flight before exceeding the critical angle of attack. It increases with weight, load factor, and forward center of gravity position.

The ratio of the lift acting on the aircraft to its weight, expressed in g units. It increases in turns and manoeuvres and raises the speed at which the wing stalls.

A model atmosphere assuming a sea-level temperature of 15 degrees Celsius, a pressure of 1013.25 hPa, and a lapse rate of about 2 degrees Celsius per 1000 feet up to the tropopause. It provides a common reference for performance and altitude calculations.

The difference between the actual temperature at a given level and the temperature predicted by the standard atmosphere model. It is used to adjust pressure altitude for non-standard conditions when computing density altitude and performance.

The pressure value dialed into an altimeter's reference window so that it indicates altitude above a chosen reference, such as mean sea level or an aerodrome. It is usually expressed in hectopascals or inches of mercury.

The altitude at or below which the aircraft's altitude is controlled by reference to an altimeter set to local pressure. Above it, the standard pressure setting is used and the aircraft flies at flight levels.

The height of the lowest broken or overcast cloud layer above the ground, or the vertical visibility into obscuring phenomena. It is a key criterion for visual flight rules and aerodrome operating minima.

The altimeter setting that, when dialed in on the ground at an aerodrome, causes the altimeter to indicate the aerodrome elevation. It is derived from station pressure reduced to mean sea level.

A change in wind speed or direction over a short distance, horizontally or vertically. It can cause sudden airspeed and lift changes close to the ground, making it a serious hazard during approach and departure.

A localized downdraft producing a strong outflow of wind at the surface over a small area. It can cause a rapid loss of airspeed and lift followed by a sudden increase, especially on approach.

The direction the aircraft's longitudinal axis points, measured clockwise from true north. It differs from magnetic heading by the local variation and from track by the drift caused by wind.

The direction the aircraft's nose points, measured clockwise from magnetic north. It equals true heading plus or minus magnetic variation and is the value shown on a magnetic compass.

The angular difference between true north and magnetic north at a given location, shown on aeronautical charts as east or west. It must be applied to convert between true and magnetic directions.

The angular offset applied between heading and desired track so that wind drift is cancelled. It depends on wind speed and direction relative to the aircraft's speed and intended path.

The actual path of the aircraft over the ground, measured clockwise from a reference north. It results from the combination of heading and wind and may differ from the heading flown.

A condition in which body tissues receive insufficient oxygen, causing impaired judgement, euphoria, and reduced vision. It can develop gradually above certain altitudes and the affected pilot may not notice the symptoms.

The period after exposure to insufficient oxygen during which a person can still take effective corrective action. It shortens rapidly as altitude increases and varies between individuals.

Abnormally rapid or deep breathing that lowers carbon dioxide in the blood, producing dizziness, tingling, and visual disturbance. Its symptoms resemble hypoxia, so the pilot should first check oxygen and breathing rate.

A false perception of the aircraft's position or motion, usually caused when visual references are lost and the pilot relies on misleading inner-ear sensations. Recovery depends on trusting instruments rather than sensations.

The inner-ear organs that sense rotation and acceleration, helping maintain balance. Without visual reference they can produce convincing but false sensations of turning or pitching during flight.

A false interpretation of sensory information, such as a runway appearing wider or a black-hole approach causing a too-low path. Recognizing common illusions helps the pilot avoid inappropriate corrections.

A written sequence of items used to verify that critical actions have been completed before, during, and after flight. It should be read aloud and confirmed rather than used from memory.

A systematic external and internal check of the aircraft before flight to confirm its condition, fuel and oil quantities, control freedom, and absence of damage. It is performed according to the manufacturer's or operator's checklist.

A planned sequence of actions for handling a failure or hazardous situation, such as engine failure or fire. It is normally memorized for immediate items and then confirmed with the checklist.

The airspeed that maximizes the distance travelled per unit of altitude lost with the engine at idle or failed. It is used to extend the glide toward a suitable landing area.

A certification by an authorized person that specified maintenance has been completed and the aircraft is returned to service. It is entered in the aircraft records and confirms airworthiness for the continued operation.