CAAB PPL Theory key terms

The minimum flight visibility and distance from cloud that a pilot must maintain when flying under visual flight rules, varying with airspace class and altitude. Staying within these limits keeps the flight legal and allows see-and-avoid traffic separation.

Airspace of defined dimensions within which air traffic control service is provided to flights in accordance with the airspace classification. Entry usually requires a clearance, and the class determines whether VFR or IFR flight is permitted.

The rule assigning cruising levels by magnetic track: tracks from 000 to 179 degrees use odd thousands, and tracks from 180 to 359 degrees use even thousands, with IFR and VFR separated by 1000 feet in most cases. It reduces head-on collision risk.

The altitude at or below which the aircraft's altimeter is set to local pressure and above which it is set to standard pressure. It marks the change from altitude references to flight levels for vertical separation.

A surface of constant atmospheric pressure referenced to the standard pressure setting of 1013.2 hectopascals and expressed in hundreds of feet. Aircraft above the transition altitude use flight levels so that all aircraft share the same pressure reference.

The altimeter subscale setting that, when entered on the ground, causes the altimeter to indicate the aerodrome elevation above mean sea level. It is the normal setting for takeoff, landing, and flight below the transition altitude.

The four-digit octal squawk that a pilot sets in the aircraft transponder to identify the flight to air traffic control radar. Discrete codes are assigned by ATC, while 7700, 7600, and 7500 signal emergency, radio failure, and unlawful interference.

The pilot's repetition of an ATC clearance or instruction to confirm it was received and understood correctly. Clearances involving runway, altitude, heading, speed, or frequency must always be read back in full.

The acute angle between the wing chord line and the relative airflow approaching it. Lift and drag both increase as this angle grows, until the critical angle is exceeded and the wing stalls.

The angle of attack at which airflow separates from the wing and lift reaches its maximum, after which the wing stalls. It is essentially constant for a given wing regardless of weight, speed, or bank angle.

The lowest indicated airspeed at which an aircraft can maintain level flight in a given configuration. It increases with weight, load factor, and forward centre of gravity position, and decreases with flap extension.

The ratio of the total lift produced by the wings to the aircraft's weight, expressed in g. It rises sharply in level turns and in pull-ups, raising stall speed and the structural stress on the airframe.

The point through which the total weight of the aircraft acts. Its position along the chord affects stability and control; it must remain within the certified forward and aft limits for every phase of flight.

The horizontal distance between a mass and the reference datum from which moments are calculated. Multiplying each mass by its arm produces a moment, and summing moments locates the aircraft's centre of gravity.

The greatest total mass, including fuel, payload, and the aircraft itself, at which takeoff is permitted by the certification or by performance limitations. Exceeding it degrades climb performance and may overstress the structure.

The pressure altitude corrected for non-standard temperature. High density altitude, produced by heat, high elevation, or low pressure, reduces engine power and propeller thrust and lengthens takeoff and landing distances.

The altitude indicated when the altimeter subscale is set to standard pressure of 1013.2 hectopascals. It is the basis for performance charts and for the flight levels used above the transition altitude.

The shortest runway length for which the accelerate-stop distance equals the accelerate-go distance, so that either action is equally safe after an engine failure at the critical speed. It is a key factor in takeoff performance planning.

A change in wind speed or direction over a short distance, vertically or horizontally. Low-level shear near thunderstorms or fronts can cause sudden airspeed loss and is a major hazard on approach and departure.

A localized, intense downdraft from a cumulonimbus cloud that spreads outward on reaching the ground. It produces severe and rapidly changing headwind then tailwind, and is especially dangerous during approach and landing.

A towering convective cloud reaching the tropopause, associated with thunderstorms, hail, severe turbulence, icing, and lightning. Aircraft should avoid it by a wide margin, both laterally and vertically, because hazards extend beyond the visible cloud.

Ice that forms in the carburettor when fuel vaporization and venturi pressure drop cool the air below freezing, even at moderate outside temperatures. It causes gradual power loss and is countered by applying carburettor heat.

The pressure-sensing system that supplies pitot (ram) pressure and static pressure to the airspeed indicator, altimeter, and vertical speed indicator. Blockages of either source produce characteristic and misleading instrument errors.

The angular difference at a given place between true north and magnetic north, shown on charts as east or west. It must be applied to convert between true and magnetic directions, and it changes slowly with time.

The error in a magnetic compass caused by the aircraft's own magnetic fields and electrical currents. It differs by heading and is recorded on a compass correction card, which the pilot uses to obtain magnetic heading.

A magnetic bearing from a VOR station, along which an aircraft can track toward or away from the station. The airborne receiver displays which radial is selected and whether the aircraft is left or right of it.

A satellite-based navigation system that provides position, track, and time by receiving signals from orbiting satellites. Its accuracy depends on satellite geometry and signal integrity, which must be monitored during instrument approaches.

A radio call giving ATC the aircraft's position, time, altitude, and next expected reporting point. Routine reports keep controllers informed when the flight is outside radar coverage or operating under procedural control.

A condition in which body tissues receive insufficient oxygen, causing euphoria, impaired judgement, and eventually unconsciousness. It can occur gradually with altitude exposure and is insidious because the affected pilot often notices nothing.

Rapid or deep breathing that lowers blood carbon dioxide, producing dizziness, tingling, and confusion. Its symptoms resemble hypoxia, and treatment is to slow the breathing rate and reassure the affected person.

Loss of correct awareness of body position relative to the earth, usually from conflicting or absent visual cues. It is countered by relying on flight instruments rather than bodily sensations, especially in cloud or at night.

An approved document listing items of equipment that may be inoperative while the aircraft remains airworthy, subject to specified conditions and procedures. It allows dispatch without every system serviceable, within defined limits.

The systematic walk-around and checks of the aircraft's structure, controls, fuel, oil, and documents before flight. It confirms the aircraft is airworthy and that no obvious defect or hazard has been overlooked.

A discontinued approach in which the pilot applies power and climbs away instead of landing. It is a normal, safe manoeuvre used whenever the approach is unstable, the runway is obstructed, or landing conditions are unsafe.

The drag created as a by-product of generating lift, caused by the wingtip vortices and the rearward tilt of the lift vector. It is greatest at low speed and high angle of attack and decreases as speed increases.

A dimensionless number describing how much lift a wing produces at a given angle of attack and configuration. It rises with angle of attack up to the stall and varies with flap setting and airfoil shape.

The distance an aircraft can fly per unit of fuel consumed, usually expressed in nautical miles per kilogram or gallon. It is greatest at a particular speed and altitude, and planning uses it to compute fuel needs.