CASA IREX key terms

Rules governing flight by reference to instruments, requiring specific qualifications, equipment, and clearances. They apply in controlled airspace and during operations where visual references cannot be maintained.

An authorization from air traffic control for an aircraft to proceed under instrument flight rules within controlled airspace. It includes route, altitude, and any restrictions the pilot must follow.

The lowest published altitude between radio fixes that assures acceptable navigational signal coverage and meets obstacle clearance requirements along an airway. It is printed on enroute charts for each segment.

The lowest published altitude between radio fixes that meets obstacle clearance requirements and assures acceptable navigational signal coverage within a specified distance. It may be lower than the minimum enroute altitude.

The lowest altitude, established by air traffic control, at which radar vectors may be issued to aircraft. It provides required terrain and obstruction clearance but may not guarantee navigation signal reception.

A specified altitude on a precision or approach-with-vertical-guidance procedure at which a missed approach must be initiated if the required visual reference is not established. It is referenced to barometric altimetry.

The lowest altitude to which descent is authorized on a non-precision approach until the required visual reference is established. Reaching it without visual contact requires a missed approach.

A published sequence of maneuvers to be followed when an approach cannot be completed to a landing. It protects the aircraft from obstacles while allowing a climb to a safe altitude for another attempt or diversion.

A standardized series of predetermined maneuvers for arriving aircraft under instrument conditions, from the initial approach fix to a point where landing is possible or a missed approach is begun. It is published on approach charts.

The point on an instrument approach where the final approach segment begins, marked by a navigation fix or facility. Descent below the segment altitude typically starts here on non-precision approaches.

A heading or course issued by air traffic control to provide navigational guidance to an aircraft. The controller is responsible for terrain and traffic separation while the aircraft is being vectored.

The pressure value used to calibrate an aircraft's altimeter so it indicates height above a reference datum. It is obtained from a station or air traffic control and must be updated as pressure changes.

A fixed altimeter reference of 29.92 inches of mercury, or 1013.2 hectopascals, used above the transition altitude. Altitudes flown on this setting are called flight levels.

The altitude at or below which an aircraft's altimeter is set to the local pressure setting and above which the standard pressure setting is used. It separates altitude references from flight levels.

The height above ground of the lowest broken or overcast cloud layer, or of an obscuring phenomenon, as reported in aviation weather observations. It determines whether visual flight rules conditions exist.

The greatest horizontal distance at which prominent objects can be seen and identified, reported in weather observations. It is a key criterion for determining flight rules and approach minimums.

Weather conditions below the minimums prescribed for visual flight rules, expressed in terms of visibility and distance from clouds. Flight under these conditions requires an instrument rating and an IFR clearance.

A concise forecast of expected meteorological conditions at an aerodrome and its vicinity over a specified period. It includes wind, visibility, weather, and cloud information for aviation planning.

A routine aviation weather report of observed conditions at an aerodrome, issued at regular intervals. It typically includes wind, visibility, weather phenomena, sky condition, temperature, dew point, and pressure.

A change in wind speed or direction over a short distance, either vertically or horizontally. It can cause sudden airspeed changes and is especially hazardous near the ground during approach and departure.

A localized, intense downdraft that spreads out horizontally upon reaching the surface. It produces severe and rapidly changing wind shear that is dangerous to aircraft at low altitude.

The accumulation of ice on aircraft surfaces caused by supercooled water droplets freezing on impact. It increases weight and drag while reducing lift and can impair control surfaces and engine performance.

The altitude at which the air temperature is zero degrees Celsius. It indicates where icing conditions are likely and is used in flight planning to select safe altitudes.

A ground-based navigation aid that transmits signals allowing aircraft to determine their bearing from the station. It supports navigation along airways and instrument approach procedures.

A radio navigation system that measures the slant range from an aircraft to a ground station. It provides distance information used for position fixing and approach procedures.

A precision approach system providing lateral and vertical guidance to a runway. It consists of a localizer for alignment, a glide path for descent, and marker beacons or distance information.

The component of an instrument landing system that provides horizontal guidance aligned with the runway centerline. It indicates whether the aircraft is left or right of the correct approach course.

The vertical guidance component of an instrument landing system, defining a descent angle to the runway. It provides the correct altitude reference during the final approach segment.

A satellite-based system providing position, navigation, and timing information to aircraft. It supports area navigation, enroute navigation, and approach procedures with appropriate avionics and certification.

A method of navigation that allows aircraft to operate on any desired course within the coverage of navigation aids, rather than being constrained to direct routes between stations. It uses onboard computing and position sensors.

A navigation specification that requires onboard performance monitoring and alerting, along with a defined level of accuracy. It permits operations within specified airspace based on demonstrated capability.

The actual speed of an aircraft through the air mass, corrected for altitude and temperature effects on indicated airspeed. It is used for flight planning and performance calculations.

The speed shown on the airspeed indicator, derived from ram air pressure. It is used for aircraft performance limitations and is affected by installation and position errors.

The speed of an aircraft relative to the ground, equal to true airspeed adjusted for wind. It determines time enroute and fuel consumption over the ground.

A vector diagram relating true airspeed, wind velocity, and ground speed with the resulting drift angle. It is used to calculate headings and groundspeeds for flight planning.

The point at which the aircraft's weight is considered concentrated. Its position must remain within approved limits for safe control and performance throughout the flight.

The process of calculating total aircraft weight and center of gravity position to ensure they fall within approved limits. It affects takeoff, climb, cruise, landing performance, and controllability.

The difference between an aircraft's maximum allowable gross weight and its empty weight. It includes payload, fuel, and crew, and limits how much can be carried on a flight.

The altitude corresponding to a given air density under standard conditions. High temperature, high elevation, and high humidity increase it, reducing aircraft and engine performance.