Glossary

Radio magnetic indicator (RMI). An electronic navigation Reduced vertical separation minimum (RVSM). Reduces instrument that combines a magnetic compass with an ADF or the vertical separation between flight levels (FL) 290 and 410 VOR. The card of the RMI acts as a gyro-stabilized magnetic from 2,000 feet to 1,000 feet, and makes six additional FLs compass, and shows the magnetic heading the aircraft is flying. available for operation. Also see DRVSM. Reference circle (also, distance circle). The circle depicted Radiosonde. A weather instrument that observes and reports in the plan view of an IAP chart that typically has a 10 NM meteorological conditions from the upper atmosphere. This radius, within which chart the elements are drawn to scale. instrument is typically carried into the atmosphere by some form of weather balloon. Regions of command. The “regions of normal and reversed command” refers to the relationship between speed and the Radio wave. An electromagnetic (EM) wave with frequency power required to maintain or change that speed in flight. characteristics useful for radio transmission. Region of reverse command. Flight regime in which flight RAIM. See receiver autonomous integrity monitoring. at a higher airspeed requires a lower power setting and a lower airspeed requires a higher power setting in order to RAM recovery. The increase in thrust as a result of ram air maintain altitude. pressures and density on the front of the engine caused by air velocity. REIL. See runway end identifier lights. Random RNAV routes. Direct routes, based on area Relative bearing (RB). The angular difference between the navigation capability, between waypoints defined in terms aircraft heading and the direction to the station, measured of latitude/longitude coordinates, degree-distance fixes, or clockwise from the nose of the aircraft. offsets from established routes/airways at a specified distance and direction. Relative bearing indicator (RBI). Also known as the fixed- card ADF, zero is always indicated at the top of the instrument Ranging signals. Transmitted from the GPS satellite, signals and the needle indicates the relative bearing to the station. allowing the aircraft’s receiver to determine range (distance) from each satellite. Relative humidity. The ratio of the existing amount of water vapor in the air at a given temperature to the maximum Rapid decompression. The almost instantaneous loss of amount that could exist at that temperature; usually expressed cabin pressure in aircraft with a pressurized cockpit or cabin. in percent. RB. See relative bearing. Relative wind. Direction of the airflow produced by an object moving through the air. The relative wind for an airplane in RBI. See relative bearing indicator. flight flows in a direction parallel with and opposite to the direction of flight; therefore, the actual flight path of the RCO. See remote communications outlet. airplane determines the direction of the relative wind. Receiver autonomous integrity monitoring (RAIM). A Remote communications outlet (RCO). An unmanned system used to verify the usability of the received GPS signals communications facility that is remotely controlled by air and warns the pilot of any malfunction in the navigation traffic personnel. system. This system is required for IFR-certified GPS units. Required navigation performance (RNP). A specified level Recommended altitude. An altitude depicted on an instrument of accuracy defined by a lateral area of confined airspace in approach chart with the altitude value neither underscored nor which an RNP-certified aircraft operates. overscored. The depicted value is an advisory value. Restricted area. Airspace designated under 14 CFR part Receiver-transmitter (RT). A system that receives and 73 within which the flight of aircraft, while not wholly transmits a signal and an indicator. prohibited, is subject to restriction. Reverse sensing. The VOR needle appearing to indicate the reverse of normal operation. G-25