Iran CAO ATPL Theory key terms

The 1944 international treaty that established ICAO and the basic legal framework for civil aviation, covering sovereignty, aircraft nationality, and standards for international flight operations.

One of the numbered technical volumes attached to the Chicago Convention; each Annex covers a subject such as personnel licensing, rules of the air, or meteorology and contains standards binding on contracting states.

A Standard is a specification whose uniform application is necessary for safety and is binding; a Recommended Practice is desirable but not mandatory, allowing flexibility where local conditions differ.

An authorization from air traffic control for an aircraft to proceed under specified conditions; it does not by itself relieve the pilot in command of responsibility for safety or terrain clearance.

The mandatory repetition by the pilot of safety-critical ATC instructions such as route clearances, runway assignments, and altimeter settings, so the controller can verify correct reception.

A four-digit octal transponder code assigned by ATC that identifies the aircraft on secondary surveillance radar; specific codes such as 7500, 7600 and 7700 signal unlawful interference, radio failure and emergency.

The lettered system (A to G) defining service level, separation requirements, VMC minima and clearance rules within a volume of airspace; controlled classes A to E restrict VFR and typically require an ATC clearance.

The Minimum Equipment List, approved for a specific aircraft type, that permits dispatch with certain inoperative items under stated conditions, limitations and rectification intervals, provided overall safety is maintained.

A mandatory document issued by the state of design and adopted by the state of registry, requiring specific inspections or modifications within a stated compliance time to correct an unsafe condition.

A manufacturer-issued document recommending inspection, modification or maintenance action; it becomes mandatory only when made so by an airworthiness directive or by the operator's approved maintenance programme.

The duplication or triplication of critical systems, such as hydraulic, electrical or flight control channels, so that a single failure does not prevent safe continuation of flight or landing.

Calculation of usable fuel comprising taxi, trip, contingency, alternate, final reserve and, where required, additional fuel, ensuring the aircraft lands with at least the final reserve intact.

Fuel allowance, often a percentage of trip fuel or a fixed time, carried to cover unforeseen deviations such as weather, routing or level changes; its amount depends on the chosen policy.

Carrying more fuel than required at the destination to avoid higher uplift prices elsewhere, weighed against the extra fuel burned due to increased weight and any performance limitations.

The point along a route beyond which it is no longer possible, considering fuel and winds, to return to the departure aerodrome; often called the equal-time point when diversion to another field applies.

The position from which the time to fly to either of two diversion aerodromes is equal, used in long-range planning to decide the most efficient diversion option in an emergency.

The furthest point from which a diversion to a designated alternate is still possible while retaining required reserves, calculated from fuel flow and wind conditions.

A condition in which the tissues receive insufficient oxygen, causing impaired judgement, euphoria and loss of consciousness; at high cabin altitudes it develops rapidly and requires immediate oxygen use.

The period after loss of oxygen supply during which a person can still take effective corrective action; it shortens markedly as altitude increases above 25 000 feet.

A false perception of the aircraft's attitude or motion relative to the earth, often caused by conflicting vestibular and visual cues in poor visibility; trust in instruments is the primary defence.

A false sensation of pitching up or down caused by linear acceleration or deceleration, which can prompt an inappropriate control input, particularly during take-off or go-around in low visibility.

Abnormally rapid or deep breathing that lowers blood carbon dioxide, producing dizziness, tingling and confusion that can mimic hypoxia; slowing the breathing rate usually relieves symptoms.

The altimeter subscale setting that, when applied, makes the altimeter indicate altitude above mean sea level at the aerodrome reference point; used for terrain-relevant altitudes.

The altimeter subscale setting that makes the altimeter read zero on the aerodrome reference point, giving height above that point; used mainly in the traffic pattern and during approach.

The altitude above which the altimeter is set to standard pressure and vertical position is expressed in flight levels; below it, local pressure settings such as QNH are used.

The lowest flight level available for use above the transition altitude, chosen so that adequate separation exists between aircraft using standard pressure and those using local pressure settings.

The difference between actual temperature and the International Standard Atmosphere value at the same altitude; positive deviation reduces air density and degrades performance.

The pressure altitude corrected for temperature deviation from standard; high density altitude reduces engine power, lift and propeller efficiency, lengthening take-off and reducing climb performance.

The shortest path between two points on the surface of a sphere, lying on a plane through the centre; its track direction changes continuously except along the equator or a meridian.

A line crossing every meridian at the same angle, appearing straight on a Mercator chart; it is longer than the great circle except along meridians and the equator.

The angle between meridians, increasing with latitude; on a constant-heading flight it causes the track to change, requiring heading corrections to maintain a great-circle path.

A magnetic bearing from a VOR station, identified by the phase difference between reference and variable signals; an aircraft on a given radial is positioned along that line from the station.

The vertical guidance component of an instrument landing system, typically set near three degrees, providing a descent path to the runway touchdown zone referenced to the threshold.

Distance measuring equipment that computes slant range to a ground transponder by timing signal round trips, displayed in nautical miles and used with VOR or ILS for position fixing.

A specified altitude in a precision or vertically guided approach at which a missed approach must be initiated if the required visual reference has not been established.

The lowest altitude in a non-precision approach, expressed as a barometric altitude, to which descent is permitted before the required visual reference is established.

The decision speed at which, following an engine failure, the take-off can still be continued safely or rejected within the remaining runway; it is chosen before flight.

The take-off safety speed to be attained by 35 feet above the runway with one engine inoperative, ensuring adequate climb gradient and controllability in the take-off configuration.

The runway length at which the accelerate-stop distance equals the accelerate-go distance, giving the shortest field required for a given mass and conditions.

Drag arising from the generation of lift, caused by rearward-tilted lift vector and wingtip vortices; it decreases with increasing speed and increases with higher mass or load factor.

The angle of attack at which the wing stalls regardless of speed, mass or attitude; exceeding it causes airflow separation and loss of lift.

The ratio of total lift to weight, expressed in g; it increases in turns and manoeuvres, raising stall speed and structural loads on the airframe.

A reversion mode of fly-by-wire flight control laws, entered after certain failures, that retains some protections but reduces envelope limits and may alter handling characteristics.

A radar system that interrogates aircraft transponders to obtain identity, pressure altitude and, in modern modes, other data, providing controller displays with coded replies.

A radio report giving the aircraft's identification, position, time, altitude and next position estimate, used in procedural airspace where surveillance coverage is not available.

The point at which the aircraft's weight is considered to act; its position must remain within the certified forward and aft limits for stability, control and performance.

The highest mass approved for the start of take-off, limited by structure, performance and, in some cases, by the runway and obstacle situation on the day.

The declared length of runway plus any clearway, used to determine the maximum mass from which a take-off can be completed within the available distance.

A discrepancy between indicated and true altitude caused by incorrect pressure setting, temperature deviation from standard, or instrument and position error.