Norway ATPL Theory key terms

The speed by which a failure of the critical engine must be recognised so the take-off can be continued or stopped within the runway. It is chosen before flight and may not be changed once take-off power is applied.

The minimum speed that must be reached by 35 ft above the runway with one engine inoperative, guaranteeing climb performance and directional control. It is maintained until acceleration altitude or obstacle clearance allows flap retraction.

The runway length at which the accelerate-stop distance equals the take-off distance to 35 ft with one engine failed at V1. It represents the shortest field for a given mass and configuration.

The distance needed to accelerate to V1, recognise an engine failure, and bring the aircraft to a full stop using brakes and, if fitted, reverse thrust. It must not exceed the available runway length.

The one-engine-inoperative climb path with a required gradient reduction applied (0.8 percent for two-engine aeroplanes, 0.9 for three, 1.0 for four). It is used to verify obstacle clearance after take-off.

The lowest altitude an aircraft may descend to while following an instrument approach procedure before the required visual reference is established. It applies to non-precision approaches and differs from decision altitude.

The altitude on a precision approach at which a missed approach must be initiated if the required visual reference has not been established. It is referenced to mean sea level, whereas decision height is referenced to the threshold.

The lowest altitude providing at least 1000 ft of obstacle clearance within a sector of 25 nautical miles around a navigation aid or fix. It is published on approach charts for emergency use and initial descent planning.

The altitude above which the altimeter is set to standard pressure 1013.25 hPa and vertical position is expressed in flight levels. It varies by country and is published on aeronautical charts.

The lowest flight level available for use above the transition altitude, ensuring at least 1000 ft separation from the transition altitude. It is determined by the aerodrome pressure and provided by ATC.

A surface of constant atmospheric pressure referenced to 1013.25 hPa, expressed in hundreds of feet, used above the transition altitude. It separates aircraft vertically without reference to local pressure.

The rule assigning flight levels by magnetic track: levels from 000 to 179 degrees use odd levels, and 180 to 359 use even levels. It provides vertical separation between opposing traffic in airspace without radar control.

A flight level allocation rule dividing tracks into four quadrants with level sequences of odd, even, odd, even, separated by 500 ft. It is used in some states instead of the semi-circular rule.

The ratio of true airspeed to the local speed of sound. It governs compressibility effects, buffet margins and the maximum operating speed of high-altitude jet aircraft.

The free-stream Mach number at which airflow somewhere on the airframe first reaches the local speed of sound, creating shock waves and drag rise. It is a design limit rather than an operating limit.

The narrow speed range at high altitude between the low-speed stall buffet and the high-speed Mach buffet. It widens with decreasing altitude and constrains manoeuvring margins.

The angle between the chord line of the wing and the relative airflow. Lift increases with angle of attack until the critical angle is reached, beyond which the wing stalls.

The angle of attack at which the wing produces maximum lift and beyond which airflow separates. It is constant for a given aerofoil regardless of weight, speed or bank angle.

The ratio of total lift to weight, expressed in g. It increases in level turns and pull-ups, raising stall speed by the square root of the load factor.

The rolling moment produced by sideslip when the wings are set at an upward angle. It provides lateral stability by lowering the wing into the relative wind.

The yawing moment opposite to the intended turn direction, caused by increased induced drag on the descending aileron's wing. It is countered with coordinated rudder input.

The initial tendency of an aircraft to return to equilibrium after a disturbance. Positive static stability resists displacement, while negative static stability amplifies it.

The centre of gravity position at which the aircraft has neutral longitudinal static stability. Loading the centre of gravity aft of the neutral point produces instability.

The certified forward and aft limits of centre of gravity for a given mass, within which the aircraft may be operated. Exceeding them affects stability, performance and control authority.

The mass of the aircraft including structure, powerplant, equipment, unusable fuel and trapped fluids, but excluding crew, payload and usable fuel. It is the starting point for mass and balance calculations.

The mass of the aircraft with all payload and crew but without usable fuel. It must not exceed the certified maximum zero fuel mass, which protects the wing structure.

The altitude indicated when the altimeter is set to 1013.25 hPa. It is used in performance charts because engine and aerodynamic performance depend on pressure rather than true height.

Pressure altitude corrected for temperature deviation from ISA. High density altitude reduces engine power, lift and propeller efficiency, lengthening take-off and reducing climb performance.

The difference between actual temperature and the standard atmosphere temperature at the same altitude. It is used to correct performance data and altimeter errors from non-standard conditions.

The altimeter subscale setting that makes the instrument indicate elevation above mean sea level when on the ground. It is the standard setting below the transition altitude.

The altimeter setting that makes the instrument read zero on the aerodrome reference point. It gives height above the aerodrome rather than altitude above mean sea level.

The standard pressure setting of 1013.25 hPa used above the transition altitude, giving flight level indications. It removes local pressure variation so aircraft share a common vertical reference.

The magnetic bearing from a VOR station to the aircraft, expressed in degrees. Tracking a radial requires the course selector to be set to the desired bearing.

The needle or bar that shows lateral deviation from a selected course. Full-scale deflection corresponds to a defined angular or linear width depending on the navigation system.

The vertical guidance beam of an ILS, typically set at 3 degrees, giving a descent path to the runway. It is paired with localiser guidance for a precision approach.

The lateral guidance component of an ILS, transmitting on VHF and aligned with the runway centreline. Its course width narrows with distance to give increasing sensitivity.

Receiver autonomous integrity monitoring, which checks the consistency of satellite signals to detect faults. Without RAIM prediction, non-precision GNSS approaches may not be authorised.

A deficiency of oxygen reaching body tissues, causing impaired judgement, euphoria and loss of consciousness. It may occur without warning above 10000 ft and is countered by supplemental oxygen and descent.

The period after loss of cabin pressurisation during which a person can still perform useful tasks before incapacitation. It shortens rapidly with increasing altitude.

A false perception of position or motion caused by misleading vestibular and visual cues in flight. It is countered by instrument reference and disciplined scanning.

A false sensation of pitch caused by linear acceleration or deceleration, often prompting the pilot to pitch down after take-off acceleration. It is a form of spatial disorientation.

A line of active thunderstorms along or ahead of a cold front, producing severe turbulence, hail and wind shear. It may extend hundreds of nautical miles and is avoided by wide margins.

A localised downdraft spreading out at the surface, producing sudden headwind and tailwind changes. It is a severe hazard on approach and requires immediate go-around if encountered.

A change of wind speed or direction over a short distance, vertically or horizontally. It can cause sudden airspeed and lift changes, especially near the ground.

A narrow band of strong upper-level winds near the tropopause, associated with large temperature gradients. It affects flight planning, fuel consumption and clear-air turbulence.

The boundary between the troposphere and stratosphere, where temperature stops decreasing with height. Its height varies with latitude and season and marks the top of most weather.

Turbulence occurring in cloud-free air, often near jet streams or mountain waves. It is not detectable by weather radar and is avoided using forecasts and pilot reports.

The shortest path between two points on the Earth's surface, formed by a plane through the centre. Courses along it change continuously except on the equator or a meridian.

A line crossing every meridian at the same angle, appearing straight on a Mercator chart. It is not the shortest distance but simplifies constant-heading navigation.

The angle between meridians, equal to the change in longitude multiplied by the sine of the latitude. It is used to convert between true and grid directions.

A cylindrical chart projection on which meridians are parallel and the scale expands with latitude. Rhumb lines plot as straight lines, making it useful for constant-heading navigation.