Profile view.  Side view of an IAP chart illustrating the vertical  approach path altitudes, headings, distances, and fixes. Prohibited area.  Designated airspace within which flight of  aircraft is prohibited. Propeller/rotor modulation error.  Certain propeller RPM  settings or helicopter rotor speeds can cause the VOR course  deviation indicator (CDI) to fluctuate as much as ±6°. Slight  changes to the RPM setting will normally smooth out this  roughness. Rabbit, the.  High-intensity flasher system installed at many  large airports. The flashers consist of a series of brilliant  blue-white bursts of light flashing in sequence along the  approach lights, giving the effect of a ball of light traveling  towards the runway. Radar.  Radio Detection And Ranging. Radar approach. The controller provides vectors while  monitoring the progress of the flight with radar, guiding  the pilot through the descent to the airport/heliport or to a  specific runway. Radials.  The courses oriented from a station. Radio or radar altimeter. An electronic altimeter that  determines the height of an aircraft above the terrain by  measuring the time needed for a pulse of radio-frequency  energy to travel from the aircraft to the ground and return. Radio frequency (RF).  A term that refers to alternating  current (AC) having characteristics such that, if the current is  input to antenna, an electromagnetic (EM) field is generated  suitable for wireless broadcasting and/or communications. Radio magnetic indicator (RMI).  An electronic navigation  instrument that combines a magnetic compass card with two  bearing pointers (typically). Generally, one pointer is for the  ADF while the other is for an RNAV or VOR navigation  system. The pointers are typically different colors and of  different widths for ease of identification. Sometimes a  function switch is provided to allow the #2 pointer to be  slaved to either a VOR or RNAV system. The card of the  RMI acts as a gyro-stabilized magnetic compass (usually  corrected for north via a flux valve) and shows the magnetic  heading the aircraft is flying. Radio wave. An electromagnetic wave (EM wave) with  frequency characteristics useful for radio transmission. RAIM.  See receiver autonomous integrity monitoring. Random RNAV routes. Direct routes, based on area  navigation capability, between waypoints defined in terms  of latitude/longitude coordinates, degree-distance fixes, or  offsets from established routes/airways at a specified distance  and direction. Ranging signals.  Transmitted from the GPS satellite, these  allow the aircraft’s receiver to determine range (distance)  from each satellite. RB.  See relative bearing. RBI.  See relative bearing indicator. RCO.  See remote communications outlet. Receiver autonomous integrity monitoring (RAIM). A system used to verify the usability of the received GPS  signals and warns the pilot of any malfunction in the  navigation system. This system is required for IFR-certified  GPS units.  Recommended altitude.  An altitude depicted on an  instrument approach chart with the altitude value neither  underscored nor overscored. The depicted value is an  advisory value. Receiver-transmitter (RT).  A system that permits selection  of a unique channel or frequency whereupon a signal (typically  communication) can be transmitted and received. Reduced vertical separation minimum (RVSM).  Reduces  the vertical separation between flight level (FL) 290–410  from 2,000 feet to 1,000 feet and makes six additional FLs  available for operation. Also see DRVSM. Reference circle (also, distance circle).  The circle depicted  in the plan view of an IAP chart that typically has a 10 NM  radius, within which chart the elements are drawn to scale. Regions of command.  The “regions of normal and reversed  command” refers to the relationship between speed and the  power required to maintain or change that speed in flight. REIL.  See runway end identifier lights. Relative bearing (RB).  The angular difference between the  aircraft heading and the direction to the station, measured  clockwise from the nose of the aircraft. Relative bearing indicator (RBI).  Also known as the fixed- card ADF, zero is always indicated at the top of the instrument  and the needle indicates the relative bearing to the station. G-15