Aeronautical Terms beginning with R
Record
See Database Record
Reduced Vertical Separation Minimums (RVSM)
RVSM airspace is where air traffic control separates aircraft by a minimum of 1,000 feet vertically between flight level (FL) 290 and FL 410 inclusive. RVSM airspace is special qualification airspace; the operator and the aircraft used by the operator must be approved by the Administrator. Air traffic control notifies operators of RVSM by providing route planing information.
Reference Landing Speed (Vref)
The speed of the airplane, in a specified landing configuration, at the point where it descends through the 50-foot height in the determination of the landing distance.
Remote Communications Outlet (RCO)
An unmanned communications facility remotely controlled by air traffic personnel. RCOs serve FSSs and may be UHF or VHF. RCOs extend the communication range of the air traffic facility. RCOs were established to provide ground-to-ground communications between air traffic control specialists and pilots located at a satellite airport for delivering en route clearances, issuing departure authorizations, and acknowledging IFR cancellations or departure/landing times.
Reporting Point
A geographical location in relation to which the position of an aircraft is reported. (See Compulsory Reporting Points)
Required Navigation Performance (RNP)
RNP is a statement of the navigation performance necessary for operation within a defined airspace. On-board monitoring and alerting is required.
Roll-out RVR
The RVR readout values obtained from sensors located nearest the rollout end of the runway.
Runway Heading
The magnetic direction that corresponds with the runway centerline extended, not the painted runway numbers on the runway. Pilots cleared to “fly or maintain runway heading” are expected to fly or maintain the published heading that corresponds with the extended centerline of the departure runway (until otherwise instructed by ATC), and are not to apply drift correction; e.g., RWY 4, actual magnetic heading of the runway centerline 044.22°, fly 044°.
Runway Hotspots
Locations on a particular airport that historically have hazardous intersections. Hot spots alert pilots to the fact that there may be a lack of visibility at certain points or the tower may be unable to see that particular intersection. Whatever the reason, pilots need to be aware that these hazardous intersections exist and they should be increasingly vigilant when approaching and taxiing through these intersections. Pilots are typically notified of these areas by a Letter to Airmen or by accessing the FAA Office of Runway Safety.
Runway Incursion
An occurrence at an airport involving an aircraft, vehicle, person, or object on the ground that creates a collision hazard or results in a loss of separation with an aircraft that is taking off, intending to take off, landing, or intending to land.
Runway Safety Program (RSP)
Designed to create and execute a plan of action that reduces the number of runway incursions at the nations airports.
Runway Visual Range (RVR)
An estimate of the maximum distance at which the runway, or the specified lights or markers delineating it, can be seen from a position above a specific point on the runway centerline. RVR is normally determined by visibility sensors or transmissometers located alongside and higher than the centerline of the runway. RVR is reported in hundreds of feet.
Runway Visibility Value (RVV)
The visibility determined for a particular runway by a transmissometer. A meter provides a continuous indication of the visibility (reported in miles or fractions of miles) for the runway. RVV is used in lieu of prevailing visibility in determining minimums for a particular runway.
Ramp Weight
The total weight of the aircraft while on the ramp. It differs from takeoff weight by the weight of the fuel that will be consumed in taxiing to the point of takeoff.
Rate Of Turn
The rate in degrees/second of a turn.
Reciprocating Engine
An engine that converts the heat energy from burning fuel into the reciprocating movement of the pistons. This movement is converted into a rotary motion by the connecting rods and crankshaft.
Reduction Gear
The gear arrangement in an aircraft engine that allows the engine to turn at a faster speed than the propeller.
Region Of Reverse Command
Flight regime in which flight at a higher airspeed requires a lower power setting and a lower airspeed requires a higher power setting in order to maintain altitude.
Registration Certificate
A State and Federal certificate that documents aircraft ownership.
Relative Wind
The direction of the airflow with respect to the wing. If a wing moves forward horizontally, the relative wind moves backward horizontally. Relative wind is parallel to and opposite the flightpath of the airplane.
Reverse Thrust
A condition where jet thrust is directed forward during landing to increase the rate of deceleration.
Reversing Propeller
A propeller system with a pitch change mechanism that includes full reversing capability. When the pilot moves the throttle controls to reverse, the blade angle changes to a pitch angle and produces a reverse thrust, which slows the airplane down during a landing.
Roll
The motion of the aircraft about the longitudinal axis. It is controlled by the ailerons.
Roundout (Flare)
A pitch-up during landing approach to reduce rate of descent and forward speed prior to touchdown.
Rudder
The movable primary control surface mounted on the trailing edge of the vertical fin of an airplane. Movement of the rudder rotates the airplane about its vertical axis.
Ruddervator
A pair of control surfaces on the tail of an aircraft arranged in the form of a V. These surfaces, when moved together by the control wheel, serve as elevators, and when moved differentially by the rudder pedals, serve as a rudder.
Runway Centerline Lights
Runway centerline lights are installed on some precision approach runways to facilitate landing under adverse visibility conditions. They are located along the runway centerline and are spaced at 50-foot intervals. When viewed from the landing threshold, the runway centerline lights are white until the last 3,000 feet of the runway. The white lights begin to alternate with red for the next 2,000 feet, and for the last 1,000 feet of the runway, all centerline lights are red.
Runway Centerline Markings
The runway centerline identifies the center of the runway and provides alignment guidance during takeoff and landings. The centerline consists of a line of uniformly spaced stripes and gaps.
Runway Edge Lights
Runway edge lights are used to outline the edges of runways during periods of darkness or restricted visibility conditions. These light systems are classified according to the intensity or brightness they are capable of producing: they are the High Intensity Runway Lights (HIRL), Medium Intensity Runway Lights (MIRL), and the Low Intensity Runway Lights (LIRL). The HIRL and MIRL systems have variable intensity controls, whereas the LIRLs normally have one intensity setting.
Runway End Identifier Lights (REIL)
One component of the runway lighting system. These lights are installed at many airfields to provide rapid and positive identification of the approach end of a particular runway.
Runway Incursion
Any occurrence at an airport involving an aircraft, vehicle, person, or object on the ground that creates a collision hazard or results in loss of separation with an aircraft taking off, intending to takeoff, landing, or intending to land.
Runway Threshold Markings
Runway threshold markings come in two configurations. They either consist of eight longitudinal stripes of uniform dimensions disposed symmetrically about the runway centerline, or the number of stripes is related to the runway width. A threshold marking helps identify the beginning of the runway that is available for landing. In some instances, the landing threshold may be displaced.
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 with an ADF or VOR. The card of the RMI acts as a gyro-stabilized magnetic compass, and shows the magnetic heading the aircraft is flying.
Radio wave
An electromagnetic wave (EM wave) with frequency characteristics useful for radio transmission.
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 aircrafts receiver to determine range (distance) from each satellite.
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 receives and transmits a signal and an indicator.
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
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. (also, distance circle)
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.
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.
Relative wind
Direction of the airflow produced by an object moving through the air. The relative wind for an airplane in flight flows in a direction parallel with and opposite to the direction of flight; therefore, the actual flight path of the airplane determines the direction of the relative wind.
Remote communications outlet (RCO)
An unmanned communications facility that is remotely controlled by air traffic personnel.
Required navigation performance (RNP)
A specified level of accuracy defined by a lateral area of confined airspace in which an RNP-certified aircraft operates.
Restricted area
Airspace designated under 14 CFR part 73 within which the flight of aircraft, while not wholly prohibited, is subject to restriction.
Reverse sensing
The VOR needle appearing to indicate the reverse of normal operation.
Rhodopsin
The photosensitive pigments that initiate the visual response in the rods of the eye.
Rigidity
The characteristic of a gyroscope that prevents its axis of rotation tilting as the Earth rotates.
Rime ice
Rough, milky, opaque ice formed by the instantaneous freezing of small supercooled water droplets.
Risk
The future impact of a hazard that is not eliminated or controlled.
Runway end identifier lights (REIL)
A pair of synchronized flashing lights, located laterally on each side of the runway threshold, providing rapid and positive identification of the approach end of a runway.
Runway visibility value (RVV)
The visibility determined for a particular runway by a transmissometer.
Runway visual range (RVR)
The instrumentally derived horizontal distance a pilot should be able to see down the runway from the approach end, based on either the sighting of high-intensity runway lights, or the visual contrast of other objects.
Readiness
A principle of learning where the eagerness and single-mindedness of a person toward learning affect the outcome of the learning experience.
Receiver
In communication, the listener, reader, or student who takes in a message containing information from a source, processes it, reacts with understanding, and changes behavior in accordance with the message.
Recency
Principle of learning stating that things learned recently are remembered better than things learned some time ago. As time passes, less is remembered. Instructors use this principle when summarizing the important points at the end of a lecture in order for students to better remember them.
Relay question
Used in response to a student’s question, the student question is redirected to another student.
Reliability
The degree to which test results are consistent with repeated measurements.
Repression
Theory of forgetting proposing that a person is more likely to forget information which is unpleasant or produces anxiety.
Response
Possible answer to a multiple-choice test item. The correct response is often called the keyed response, and incorrect responses are called distractors.
Reverse question
Used in response to a student’s question. Rather than give a direct answer to the student’s query, the instructor returns the question to the same student to provide the answer.
Review and evaluation
The fourth and last step in the teaching process, which consists of a review of all material and an evaluation of the students. In the telling and doing technique of flight instruction, this step consists of the instructor evaluating the student’s performance while the student performs the required procedure.
Rhetorical question
Generally, a question asked for a purpose other than to obtain the information the question asks. For this handbook’s purpose, a question asked to stimulate group thought. Normally answered by the instructor, it is more commonly used in lecturing rather than in guided discussions.
Risk elements in ADM
Take into consideration the four fundamental risk elements: the pilot, the aircraft, the environment, and external pressures.
Risk management
The part of the decision-making process which relies on situational awareness, problem recognition, and good judgment to reduce risks associated with each flight.
Rote learning
A basic level of learning in which the student has the ability to repeat back something learned, with no understanding or ability to apply what was learned.
Rated 30-second OEI Power
With respect to rotorcraft turbine engines, the approved brake horsepower developed under static conditions at specified altitudes and temperatures within the operating limitations established for the engine under part 33 of this chapter, for continuation of one flight operation after the failure or shutdown of one engine in multiengine rotorcraft, for up to three periods of use no longer than 30 seconds each in any one flight, and followed by mandatory inspection and prescribed maintenance action.
Rated 2-minute OEI Power
With respect to rotorcraft turbine engines, the approved brake horsepower developed under static conditions at specified altitudes and temperatures within the operating limitations established for the engine under part 33 of this chapter, for continuation of one flight operation after the failure or shutdown of one engine in multiengine rotorcraft, for up to three periods of use no longer than 2 minutes each in any one flight, and followed by mandatory inspection and prescribed maintenance action.
Rated continuous OEI power
With respect to rotorcraft turbine engines, the approved brake horsepower developed under static conditions at specified altitudes and temperatures within the operating limitations established for the engine under part 33 of this chapter, and limited in use to the time required to complete the flight after the failure or shutdown of one engine of a multiengine rotorcraft.
Rated maximum continuous augmented thrust
With respect to turbojet engine type certification, the approved jet thrust that is developed statically or in flight, in standard atmosphere at a specified altitude, with fluid injection or with the burning of fuel in a separate combustion chamber, within the engine operating limitations established under Part 33 of this chapter, and approved for unrestricted periods of use.
Rated maximum continuous power
With respect to reciprocating, turbopropeller, and turboshaft engines, the approved brake horsepower that is developed statically or in flight, in standard atmosphere at a specified altitude, within the engine operating limitations established under Part 33, and approved for unrestricted periods of use.
Rated maximum continuous thrust
With respect to turbojet engine type certification, the approved jet thrust that is developed statically or in flight, in standard atmosphere at a specified altitude, without fluid injection and without the burning of fuel in a separate combustion chamber, within the engine operating limitations established under Part 33 of this chapter, and approved for unrestricted periods of use.
Rated takeoff augmented thrust
With respect to turbojet engine type certification, the approved jet thrust that is developed statically under standard sea level conditions, with fluid injection or with the burning of fuel in a separate combustion chamber, within the engine operating limitations established under Part 33 of this chapter, and limited in use to periods of not over 5 minutes for takeoff operation.
Rated takeoff power
With respect to reciprocating, turbopropeller, and turboshaft engine type certification, the approved brake horsepower that is developed statically under standard sea level conditions, within the engine operating limitations established under Part 33, and limited in use to periods of not over 5 minutes for takeoff operation.
Rated takeoff thrust
With respect to turbojet engine type certification, the approved jet thrust that is developed statically under standard sea level conditions, without fluid injection and without the burning of fuel in a separate combustion chamber, within the engine operating limitations established under Part 33 of this chapter, and limited in use to periods of not over 5 minutes for takeoff operation.
Rated 30-minute OEI power
With respect to rotorcraft turbine engines, the approved brake horsepower developed under static conditions at specified altitudes and temperatures within the operating limitations established for the engine under part 33 of this chapter, and limited in use to one period of use no longer than 30 minutes after the failure or shutdown of one engine of a multiengine rotorcraft.
Rated 21/2-minute OEI power
With respect to rotorcraft turbine engines, the approved brake horsepower developed under static conditions at specified altitudes and temperatures within the operating limitations established for the engine under part 33 of this chapter for periods of use no longer than 21/2minutes each after the failure or shutdown of one engine of a multiengine rotorcraft.
Rating
A statement that, as a part of a certificate, sets forth special conditions, privileges, or limitations.
Reference landing speed
The speed of the airplane, in a specified landing configuration, at the point where it descends through the 50 foot height in the determination of the landing distance.
Reporting point
A geographical location in relation to which the position of an aircraft is reported.
Restricted area
A restricted area is airspace designated under Part 73 within which the flight of aircraft, while not wholly prohibited, is subject to restriction.
Rocket
An aircraft propelled by ejected expanding gases generated in the engine from self-contained propellants and not dependent on the intake of outside substances. It includes any part which becomes separated during the operation.
Rotorcraft
A heavier-than-air aircraft that depends principally for its support in flight on the lift generated by one or more rotors.
Rotorcraft-load combination
The combination of a rotorcraft and an external-load, including the external-load attaching means. Rotorcraft-load combinations are designated as Class A, Class B, Class C, and Class D, as follows:
(1) Class A rotorcraft-load combination means one in which the external load cannot move freely, cannot be jettisoned, and does not extend below the landing gear.
(2) Class B rotorcraft-load combination means one in which the external load is jettisonable and is lifted free of land or water during the rotorcraft operation.
(3) Class C rotorcraft-load combination means one in which the external load is jettisonable and remains in contact with land or water during the rotorcraft operation.
(4) Class D rotorcraft-load combination means one in which the external-load is other than a Class A, B, or C and has been specifically approved by the Administrator for that operation.
Route segment
A portion of a route bounded on each end by a fix or navigation aid (NAVAID).
Ramp Weight
The zero fuel weight plus all of the usable fuel on board.
Reference Datum
(GAMA) An imaginary vertical plane from which all horizontal distances are measured for balance purpose.
Reduction Factor
A number, usually 100 or 1,000 by which a moment is divided to produce a smaller number that is less likely to cause mathematical errors when computing the center of gravity.
Residual Fuel
Fuel that remains trapped in the system after draining the fuel from the aircraft with the aircraft in level flight attitude. The weight of this residual fuel is counted as part of the empty weight of the aircraft.
Radar altitude
The altitude of an aircraft determined by radar-type radio altimeter; thus the actual distance from the nearest terrain or water feature encompassed by the downward directed radar beam. For all practical purposes, it is the“actual” distance above a ground or inland water surface or the true altitude above an ocean surface.
Range attenuation
Reduction of radar power density because of distance from the antenna. It occurs in the outgoing beam at a rate proportional to 1/(range²) The return signal is also attenuated at the same rate.
RADAR (contraction for radio detection and ranging)
An electronic instrument used for the detection and ranging of distant objects of such composition that they scatter or reflect radio energy. Since hydrometeors can scatter radio energy, weather radars, operating on certain frequency bands, can detect the presence of precipitation, clouds, or both.
Radar beam
The focused energy radiated by radar similar to a flashlight or searchlight beam.
Radarsonde observation
A rawinsonde observation in which winds are determined by radar tracking a balloon-borne target.
Radiation
The emission of energy by a medium and transferred, either through free space or another medium, in the form of electromagnetic waves.
Radiation fog
Fog characteristically resulting when radiational cooling of the earth’s surface lowers the air temperature near the ground to or below its initial dew point on calm, clear nights.
Radiosonde
A balloon-borne instrument for measuring pressure, temperature, and humidity aloft.
Radiosonde observation
A sounding made by the instrument.
Rain
A form of precipitation; drops are larger than drizzle and fall in relatively straight, although not necessarily vertical, paths as compared to drizzle which falls in irregular paths.
Rain shower
Precipitation from a cumuliform cloud; characterized by the suddenness of beginning and ending, by the rapid change of intensity, and usually by rapid change in the appearance of the sky; showery precipitation in the form of rain.
Range-height indicator (RHI) scope
A radar indicator scope displaying a vertical cross section of targets along a selected azimuth.
RAOB
A radiosonde observation.
Rawin
A rawinsonde observation.
Rawinsonde observation
A combined winds aloft and radiosonde observation. Winds are determined by tracking the radiosonde by radio direction finder or radar.
Refraction
In radar, bending of the radar beam by variations in atmospheric density, water vapor content, and temperature.
Relative humidity
The ratio of the existing amount of water vapor in the air at a given temperature to the maximum amount that could exist at that temperature; usually expressed in percent.
Remote scope
In radar meteorology a “slave” scope remoted from weather radar.
Resolution
Pertaining to radar, the ability of radar to show discrete targets separately, i.e., the better the resolution, the closer two targets can be to each other, and still be detected as separate targets.
Range resolution
The ability of radar to distinguish between targets on the same azimuth but at different ranges.
Ridge (also called ridge line)
In meteorology, an elongated area of relatively high atmospheric pressure; usually associated with and most clearly identified as an area of maximum anticyclonic curvature of the wind flow (isobars, contours, or streamlines).
Rime icing (or rime ice)
The formation of a white or milky and opaque granular deposit of ice formed by the rapid freezing of supercooled water droplets as they impinge upon an exposed aircraft.
Rocketsonde
A type of radiosonde launched by a rocket and making its measurements during a parachute descent; capable of obtaining soundings to a much greater height than possible by balloon or aircraft.
Roll cloud
A dense and horizontal roll-shaped accessory cloud located on the lower leading edge of a cumulonimbus or less often, a rapidly developing cumulus; indicative of turbulence. Sometimes improperly called rotor cloud.
Rotor cloud
A turbulent cloud formation found in the lee of some large mountain barriers, the air in the cloud rotates around an axis parallel to the range; indicative of possible violent turbulence. Sometimes improperly called roll cloud.
Runway temperature
The temperature of the air just above a runway, ideally at engine and/or wing height, used in the determination of density altitude; useful at airports when critical values of density altitude prevail.
Runway visibility
The meteorological visibility along an identified runway determined from a specified point on the runway; may be determined by a transmissometer or by an observer.
Runway visual range
An instrumentally derived horizontal distance a pilot should see down the runway from the approach end; based on either the sighting of high intensity runway lights or on the visual contrast of other objects, whichever yields the greatest visual range.
Relative vorticity
Vorticity of the air relative to the Earth, disregarding the component of vorticity resulting from Earth’s rotation.
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 toward the runway.
Radar
A system that uses electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, weather formations, and terrain. The term RADAR was coined in 1941 as an acronym for Radio Detection and Ranging. The term has since entered the English language as a standard word, radar, losing the capitalization in the process.
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.
Radar services
Radar is a method whereby radio waves are transmitted into the air and are then received when they have been reflected by an object in the path of the beam. Range is determined by measuring the time it takes (at the speed of light) for the radio wave to go out to the object and then return to the receiving antenna. The direction of a detected object from a radar site is determined by the position of the rotating antenna when the reflected portion of the radio wave is received.
Radar summary chart
A weather product derived from the national radar network that graphically displays a summary of radar weather reports.
Radar weather report (SD)
A report issued by radar stations at 35 minutes after the hour, and special reports as needed. Provides information on the type, intensity, and location of the echo tops of the precipitation.
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 with an ADF or VOR. The card of the RMI acts as a gyro-stabilized magnetic compass, and shows the magnetic heading the aircraft is flying.
Radiosonde
A weather instrument that observes and reports meteorological conditions from the upper atmosphere. This instrument is typically carried into the atmosphere by some form of weather balloon.
Radio wave
An electromagnetic (EM ) wave with frequency characteristics useful for radio transmission.
RAM recovery
The increase in thrust as a result of ram air pressures and density on the front of the engine caused by air velocity.
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, signals allowing the aircraft’s receiver to determine range (distance) from each satellite.
Rapid decompression
The almost instantaneous loss of cabin pressure in aircraft with a pressurized cockpit or cabin.
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 receives and transmits a signal and an indicator.
Reduced vertical separation minimum (RVSM)
Reduces the vertical separation between flight levels (FL) 290 and 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.
Region of reverse command
Flight regime in which flight at a higher airspeed requires a lower power setting and a lower airspeed requires a higher power setting in order to maintain altitude.
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.
Relative humidity
The ratio of the existing amount of water vapor in the air at a given temperature to the maximum amount that could exist at that temperature; usually expressed in percent.
Relative wind
Direction of the airflow produced by an object moving through the air. The relative wind for an airplane in flight flows in a direction parallel with and opposite to the direction of flight; therefore, the actual flight path of the airplane determines the direction of the relative wind.
Remote communications outlet (RCO)
An unmanned communications facility that is remotely controlled by air traffic personnel.
Required navigation performance (RNP)
A specified level of accuracy defined by a lateral area of confined airspace in which an RNP-certified aircraft operates.
Restricted area
Airspace designated under 14 CFR part 73 within which the flight of aircraft, while not wholly prohibited, is subject to restriction.
Reverse sensing
The VOR needle appearing to indicate the reverse of normal operation.
Rhodopsin
The photosensitive pigments that initiate the visual response in the rods of the eye.
Rigging
The final adjustment and alignment of an aircraft and its flight control system that provides the proper aerodynamic characteristics.
Rigidity
The characteristic of a gyroscope that prevents its axis of rotation tilting as the Earth rotates.
Rigidity in space
The principle that a wheel with a heavily weighted rim spinning rapidly will remain in a fixed position in the plane in which it is spinning.
Rime ice
Rough, milky, opaque ice formed by the instantaneous freezing of small supercooled water droplets.
Risk
The future impact of a hazard that is not eliminated or controlled.
Risk elements
There are four fundamental risk elements in aviation: the pilot, the aircraft, the environment, and the type of operation that comprise any given aviation situation.
Risk management
The part of the decision-making process which relies on situational awareness, problem recognition, and good judgment to reduce risks associated with each flight.
Rudder
The movable primary control surface mounted on the trailing edge of the vertical fin of an airplane. Movement of the rudder rotates the airplane about its vertical axis.
Ruddervator
A pair of control surfaces on the tail of an aircraft arranged in the form of a V. These surfaces, when moved together by the control wheel, serve as elevators, and when moved differentially by the rudder pedals, serve as a rudder.
Runway centerline lights
Runway lighting which consists of flush centerline lights spaced at 50-foot intervals beginning 75 feet from the landing threshold.
Runway edge lights
A component of the runway lighting system that is used to outline the edges of runways at night or during low visibility conditions. These lights are classified according to the intensity they are capable of producing.
Runway end identifier lights (REIL)
A pair of synchronized flashing lights, located laterally on each side of the runway threshold, providing rapid and positive identification of the approach end of a runway.
Runway visibility value (RVV)
The visibility determined for a particular runway by a transmissometer.
Runway visual range (RVR)
The instrumentally derived horizontal distance a pilot should be able to see down the runway from the approach end, based on either the sighting of high-intensity runway lights, or the visual contrast of other objects.
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