NCAA Namibia PPL Theory key terms

A mandatory instruction issued by the state of registry requiring inspection, modification, or limitation of an aircraft or component to correct an unsafe condition. Compliance is legally required and is normally recorded in the aircraft logbooks.

A document issued for an individual aircraft confirming that it conforms to an approved type design and is considered safe to fly within specified operating limitations. It remains valid only while maintenance, inspections, and directives are kept current.

The set of maintenance, inspection, and record-keeping processes that keep an aircraft in a condition that meets its type design and remains safe throughout its service life. It includes scheduled checks, defect rectification, and compliance with mandatory directives.

The pilot ultimately responsible for the operation and safety of the aircraft and for the conduct of the flight. The PIC has final authority over the aircraft and may deviate from rules to the extent necessary in an emergency.

A set of operating rules under which a pilot navigates and maintains separation by visual reference to the ground and horizon, subject to specified visibility and distance-from-cloud minima. VFR flights require an applicable clearance when operating in controlled airspace.

Weather conditions equal to or better than the specified minimum visibility and cloud-separation criteria for the airspace class concerned. When conditions fall below these criteria, the flight cannot continue under VFR and the pilot must act accordingly.

The height above ground level of the lowest cloud layer reported as broken or overcast, or the vertical visibility in an obscured sky. It is a key element in deciding whether VFR flight at a planned altitude is legally possible.

A routine coded report of observed surface weather at an aerodrome, typically issued at half-hourly or hourly intervals. It includes wind, visibility, cloud, temperature, dewpoint, and pressure information used for flight planning and in-flight decisions.

A coded forecast of expected weather at an aerodrome over a stated validity period, usually covering 9 to 30 hours. Pilots use it to anticipate conditions at destination and alternate aerodromes before departure.

The altimeter setting that, when set on the subscale, causes the altimeter to indicate elevation above mean sea level at the aerodrome reference point. It is used for terrain clearance and for flight levels below the transition altitude.

The altimeter setting that causes the altimeter to read zero at the aerodrome reference point, thereby showing height above that point. It is used mainly in the aerodrome traffic circuit and on approach.

The altitude at or below which the altimeter is set to QNH and above which the standard pressure setting is used, so that aircraft are separated by flight level rather than altitude. Its value is published for each aerodrome or area.

A change in wind speed or direction over a short distance, horizontally or vertically, which can cause sudden airspeed changes and loss of lift. It is most hazardous at low level during take-off and approach.

A localized column of descending air that spreads outward on reaching the surface, producing a strong headwind followed by a downdraft and tailwind. Encountered at low altitude it can cause severe loss of airspeed and performance.

The pressure altitude corrected for non-standard temperature, representing the altitude at which the aircraft performance would occur in a standard atmosphere. High density altitude reduces lift, engine power, and propeller efficiency, lengthening take-off and climb.

The altitude indicated when the altimeter subscale is set to the standard pressure setting of 1013.25 hPa. It is the basis for performance calculations and for flight levels above the transition altitude.

The point through which the total weight of the aircraft is considered to act. Its position must remain within the certified forward and aft limits for stability and control to be assured in all phases of flight.

The calculation of total aircraft mass and the position of its centre of gravity, checked against certified limits before flight. Correct loading ensures handling qualities, performance, and structural limits are respected.

The horizontal distance from the datum to the point where a mass acts. Multiplying each mass by its moment arm gives its moment, and summing moments allows the centre of gravity position to be found.

The greatest mass at which the aircraft is certified to begin the take-off run, accounting for structure, performance, and climb requirements. Exceeding it invalidates performance data and may overstress the airframe.

An aerodrome specified in the flight plan to which an aircraft may proceed if landing at the intended destination becomes impossible or inadvisable. It must meet weather, runway, and fuel requirements at the expected time of use.

The quantity of fuel that must remain at landing after the planned flight, intended to cover diversion, holding, and contingency. Planning must show the aircraft will land with at least this amount in the tanks.

The angle between the wing chord line and the relative airflow approaching it. 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 produces its maximum lift coefficient and beyond which it stalls. It is a fixed value for a given wing, independent of mass, speed, and bank angle.

A loss of lift caused by the airflow separating from the wing when the critical angle of attack is exceeded. Recovery requires reducing the angle of attack, typically by lowering the nose, and may involve adding power.

Drag created as a by-product of generating lift, caused by the pressure difference between the upper and lower wing surfaces producing wingtip vortices. It is greatest at low speed and high angle of attack and decreases as speed increases.

The ratio of the lift produced by the aircraft to its weight, expressed in g. It increases in turns and manoeuvres, raising stall speed and structural stress, and must remain within certified limits.

The tendency of an aircraft to yaw away from the direction of a turn when ailerons are applied, caused by increased drag on the down-going aileron. It is countered with coordinated rudder input.

A condition in which body tissues receive insufficient oxygen, causing impaired judgement, euphoria, and eventually unconsciousness. In aviation it arises from high altitude, restricted breathing, or carbon monoxide exposure and can be insidious in onset.

Abnormally rapid or deep breathing that reduces carbon dioxide in the blood, producing dizziness, tingling, and visual disturbance. Its symptoms resemble hypoxia, so treatment begins by ensuring an adequate oxygen supply and controlled breathing.

A mistaken perception of the aircraft's position or motion relative to the earth, arising when visual cues are lost or misleading. It is a major cause of loss of control in poor visibility and is countered by trusting instruments.

False sensations of pitch or bank caused by linear acceleration or deceleration stimulating the inner ear. For example, rapid acceleration on take-off may feel like a nose-up attitude, prompting an incorrect nose-down input.

The period after loss of oxygen supply during which a person can still perform useful, deliberate actions before becoming incapacitated. It shortens rapidly as altitude increases and is relevant to oxygen planning.

An authorization from an air traffic control unit for an aircraft to proceed under specified conditions. It does not relieve the pilot-in-command of responsibility for terrain clearance or compliance with regulations.

The mandatory repetition by the pilot of safety-related clearance elements, such as route, altitude, and frequency, to confirm they were correctly received. It allows the controller to detect and correct any misunderstanding.

The four-digit code entered in the aircraft transponder to identify the flight to air traffic control radar. Assigned codes, together with specific settings such as emergency codes, support identification and separation.

A standard rectangular path flown by aircraft around an aerodrome for landing, comprising upwind, crosswind, downwind, base, and final legs. Direction and altitude are published or advised by the aerodrome authority.

A navigation method in which the aircraft's position is calculated from a known starting point using heading, true airspeed, elapsed time, and wind. It requires regular position updates to correct accumulating error.

A vector diagram combining the aircraft's heading and true airspeed with the wind velocity to find the resulting track and groundspeed. It is the basis for calculating heading and time en route.

The direction in which the aircraft's longitudinal axis points, measured clockwise from a reference direction such as magnetic north. It differs from track, which is the actual path over the ground.