KCAA PPL Exam key terms

A document confirming that an aircraft meets the airworthiness requirements of its state of registry and is safe to fly. In Kenya it is issued and renewed under the Kenya Civil Aviation Regulations, and its validity depends on maintenance being carried out as prescribed.

The document that records the aircraft's nationality and registration marks and identifies its registered owner. It must be carried on board and its markings must match those painted on the aircraft, since the aircraft's nationality determines which state's regulations apply.

The letters and figures painted on an aircraft showing its state of registry and unique identity. Kenyan-registered aircraft carry the prefix 5Y followed by a hyphen and three letters. Correct size, position and legibility are required, and marks must be renewed if they become unclear.

Rules allowing flight by visual reference to the ground, subject to minimum flight visibility and distance from cloud. The pilot must remain clear of cloud and able to see and avoid other traffic, and must not enter controlled airspace without the required clearance.

An authorisation allowing a flight within a control zone in weather below normal VFR minima, granted by air traffic control on pilot request. The pilot must remain clear of cloud and in sight of the surface, and the clearance is subject to traffic and controller workload.

Controlled airspace extending upwards from the surface around an aerodrome, normally to a specified upper limit. Aircraft need an air traffic control clearance to enter it, and it protects the arrival and departure paths of aircraft using that aerodrome.

An authorisation from air traffic control for an aircraft to proceed under specified conditions. It is not a guarantee of separation from terrain or from unknown traffic, and the pilot in command remains responsible for the safety of the flight.

A certification, made after maintenance, that the work has been completed and the aircraft is fit for return to service. It is signed by authorised personnel and forms part of the aircraft's records, supporting the continued validity of the Certificate of Airworthiness.

A mandatory instruction issued by an airworthiness authority requiring inspection, modification or limitation on an aircraft or component. Compliance is compulsory within the stated time, and failure to comply renders the aircraft unairworthy and may invalidate the Certificate of Airworthiness.

The point at which the aircraft's weight is considered to act. It must remain within a forward and aft limit for every phase of flight, because its position affects stability, control and performance; exceeding the limits can make the aircraft unsafe or uncontrollable.

The mass of the aircraft with unusable fuel, full operating fluids and all equipment required for flight, but without usable fuel, payload or crew. It is the starting figure for mass and balance calculations and is taken from the current weighing report.

The highest mass at which the aircraft is certified to begin the take-off run. It is a structural and performance limit, and exceeding it invalidates the take-off performance figures and may overload tyres, brakes and structure.

The horizontal distance from a reference datum to a mass, used to calculate its turning effect about that datum. Multiplying each mass by its arm gives a moment, and dividing total moment by total mass locates the centre of gravity.

The altitude in the standard atmosphere at which the air density equals the actual density at the aerodrome. It increases with high temperature, high elevation and low pressure, and higher values reduce engine power, propeller thrust and lift, lengthening take-off and landing distances.

The altitude indicated on an altimeter set to the standard pressure of 1013.25 hPa. It is used for flight levels above the transition altitude and for performance calculations, and differs from true altitude whenever the actual pressure differs from standard.

The altitude above which a pilot sets the altimeter to standard pressure and reports the aircraft's height as a flight level. Below it, the local altimeter setting is used, and the changeover is made at a published altitude to keep aircraft on a common pressure reference.

The pressure value set on the altimeter subscale so that the instrument indicates height above a chosen reference. Setting the aerodrome pressure on the ground gives roughly zero on landing, while setting standard pressure gives flight levels for cruising.

The angle between the chord line of the wing and the relative airflow. Increasing it raises lift up to the critical angle, beyond which the airflow separates and the wing stalls; it is controlled by pitch attitude and is independent of airspeed alone.

The angle of attack at which the wing produces its maximum lift, immediately before the airflow separates. Any further increase causes a stall regardless of airspeed, bank angle or weight, which is why the stall is described as an angle-of-attack phenomenon.

A condition in which the airflow over the wing separates, causing a sudden loss of lift and an increase in drag. It occurs when the critical angle of attack is exceeded and is recovered by reducing the angle of attack, typically by lowering the nose.

The ratio of the lift produced by an aircraft to its weight, expressed in g. It increases in turns and manoeuvres, raising the stall speed and the structural loads, and the aircraft has a certificated maximum that must not be exceeded.

Drag created as a by-product of lift, caused by the spanwise flow and wingtip vortices. It is greatest at high angles of attack and low airspeed, and decreases as speed increases, which is why the total drag curve has a minimum at a particular speed.

The tendency of an aircraft to yaw away from the direction of a turn when ailerons are applied. The descending aileron produces more induced drag on the outer wing, and the effect is countered with coordinated rudder input.

The behaviour of a spinning mass whereby a force applied to its axis produces a resultant movement at right angles to that force, some 90 degrees later in the direction of rotation. It explains the behaviour of attitude and heading indicators and of propeller and engine gyroscopic effects.

The system supplying ram air pressure from the pitot tube and static pressure from the static ports to the airspeed indicator, altimeter and vertical speed indicator. Blockages cause characteristic instrument errors, so the system must be checked and the covers removed before flight.

A gyroscopic instrument displaying pitch and bank relative to the horizon, driven by an artificial horizon gyro. It is the primary reference for attitude in instrument flight and must be checked and caged or erected before take-off.

A direction gyro instrument showing the aircraft's heading, which must be aligned periodically with the magnetic compass because it drifts through precession and apparent wander. It gives a steadier reading than the compass during turns and turbulence.

The angular difference between true north and magnetic north at a given place, which changes slowly with time. It is shown on charts and is applied when converting between true and magnetic directions, with east variation subtracted from true to give magnetic.

The error of a magnetic compass caused by magnetic fields within the aircraft, such as electrical circuits and engine components. It varies with heading and is recorded on a compass correction card, which the pilot consults when steering by compass.

Weather conditions in which flight under visual flight rules is permitted, defined by minimum visibility and distance from cloud. The minima vary with airspace class, altitude and whether the flight is controlled, and must be met before and during the flight.

Weather conditions below the visual minima, in which flight must be conducted under instrument flight rules by a suitably qualified and equipped pilot. Entering IMC inadvertently in a VFR flight is a serious hazard requiring an immediate turn away or a declared emergency.

The altimeter subscale setting that makes the instrument read aerodrome elevation when the aircraft is on the ground. It is the setting used for take-off and landing and below the transition altitude, and is reported in hectopascals in Kenya.

The altimeter subscale setting that makes the instrument read zero when the aircraft is on the ground at the reference point. It is used in some aerodrome circuits and approach procedures, giving height above the aerodrome rather than altitude above mean sea level.

A line on a weather chart joining places of equal mean sea level pressure. The spacing of isobars indicates pressure gradient and hence wind strength, while their pattern reveals highs, lows, ridges and troughs that shape the expected weather.

The procedure in which a pilot repeats back safety-related instructions from air traffic control, such as clearances, runway assignments and altimeter settings, to confirm correct receipt. It is required for many clearances and reduces the risk of misunderstanding.

The instruction to select a specific four-digit code on the aircraft transponder, as assigned by air traffic control. Codes support radar identification and special purposes such as emergency or radio failure, and the assigned code must be retained unless changed.

The spoken distress signal, repeated three times, used when an aircraft is threatened by grave and imminent danger and requires immediate assistance. It takes priority over all other transmissions and is followed by the aircraft's identification, position, nature of distress and intentions.

The spoken urgency signal, repeated three times, used when an aircraft is in a condition concerning safety but not requiring immediate assistance, such as an uncertain position or a non-critical technical problem. It has priority over routine traffic but below distress.