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.

RMI.

See radio magnetic indicator.

RNAV.

See area navigation.

RNP.

See required navigation performance.

RT.

See receiver-transmitter.

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.

SA.

See selective availability.

St. Elmo’s Fire.

A corona discharge which lights up the aircraft surface areas where maximum static discharge occurs.

Satellite ephemeris data.

Data broadcast by the GPS satellite containing very accurate orbital data for that satellite, atmospheric propagation data, and satellite clock error data.

Sea breeze.

A coastal breeze blowing from sea to land caused by the temperature difference when the land surface is warmer than the sea surface. The sea breeze usually occurs during the day and alternates with the land breeze that blows in the opposite direction at night.

Sea level engine.

A reciprocating aircraft engine having a rated takeoff power that is producible only at sea level.

Scan.

The first fundamental skill of instrument flight, also known as “cross-check;” the continuous and logical observation of instruments for attitude and performance information.

Sectional aeronautical charts.

Designed for visual navigation of slow- or medium-speed aircraft. Topographic information on these charts features the portrayal of relief, and a judicious selection of visual check points for VFR flight. Aeronautical information includes visual and radio aids to navigation, airports, controlled airspace, restricted areas, obstructions and related data.

SDF.

See simplified directional facility.

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.

Receiver-transmitter (RT).

A system that receives and transmits a signal and an indicator.

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.

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.

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.

RF.

Radio frequency.

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.

Propeller.

A device for propelling an aircraft that, when rotated, produces by its action on the air, a thrust approximately perpendicular to its plane of rotation. It includes the control components normally supplied by its manufacturer.

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 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.

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, 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.

RB.

See relative bearing.

RBI.

See relative bearing indicator.

Planform.

The shape or form of a wing as viewed from above. It may be long and tapered, short and rectangular, or various other shapes.

Pneumatic.

Operation by the use of compressed air.

POH/AFM

See Pilot’s Operating Handbook/Airplane Flight Manual.

Poor judgment chain.

A series of mistakes that may lead to an accident or incident. Two basic principles generally associated with the creation of a poor judgment chain are: (1) one bad decision often leads to another; and (2) as a string of bad decisions grows, it reduces the number of subsequent alternatives for continued safe flight. ADM is intended to break the poor judgment chain before it can cause an accident or incident.

Position error.

Error in the indication of the altimeter, ASI, and VSI caused by the air at the static system entrance not being absolutely still.

Position report.

A report over a known location as transmitted by an aircraft to ATC.

Positive static stability.

The initial tendency to return to a state of equilibrium when disturbed from that state.

Power.

Implies work rate or units of work per unit of time, and as such, it is a function of the speed at which the force is developed. The term “power required” is generally associated with reciprocating engines.

Powerplant.

A complete engine and propeller combination with accessories.

Precession.

The characteristic of a gyroscope that causes an applied force to be felt, not at the point of application, but 90° from that point in the direction of rotation.

Precipitation.

Any or all forms of water particles (rain, sleet, hail, or snow) that fall from the atmosphere and reach the surface.

Precipitation static (P-static).

A form of radio interference caused by rain, snow, or dust particles hitting the antenna and inducing a small radio-frequency voltage into it.

Precision approach path indicator (PAPI).

A system of lights similar to the VASI, but consisting of one row of lights in two- or four-light systems. A pilot on the correct glideslope will see two white lights and two red lights. See VASI.

Preignition.

Ignition occurring in the cylinder before the time of normal ignition. Preignition is often caused by a local hot spot in the combustion chamber igniting the fuel-air mixture.

Pressure altitude.

Altitude above the standard 29.92 “Hg plane.

Pressure demand oxygen system.

A demand oxygen system that supplies 100 percent oxygen at sufficient pressure above the altitude where normal breathing is adequate. Also referred to as a pressure breathing system.

Prevailing visibility.

The greatest horizontal visibility equaled or exceeded throughout at least half the horizon circle (which is not necessarily continuous).

Preventive maintenance.

Simple or minor preservative operations and the replacement of small standard parts not involving complex assembly operation as listed in 14 CFR part 43, appendix A. Certificated pilots may perform preventive maintenance on any aircraft that is owned or operated by them provided that the aircraft is not used in air carrier service.

Primary flight display (PFD).

A display that provides increased situational awareness to the pilot by replacing the traditional six instruments used for instrument flight with an easy-to-scan display that provides the horizon, airspeed, altitude, vertical speed, trend, trim, and rate of turn among other key relevant indications.

Prohibited area.

Designated airspace within which flight of aircraft is prohibited.

Overcontrolling.

Using more movement in the control column than is necessary to achieve the desired pitch-and-bank condition.

Overboost.

A condition in which a reciprocating engine has exceeded the maximum manifold pressure allowed by the manufacturer. Can cause damage to engine components.

Overpower.

To use more power than required for the purpose of achieving a faster rate of airspeed change.

P-static.

See precipitation static.

PAPI.

See precision approach path indicator.

Parallels.

Lines of latitude.

Parasite drag.

Drag caused by the friction of air moving over the aircraft structure; its amount varies directly with the airspeed.

Payload (GAMA)

The weight of occupants, cargo, and baggage.

Personality.

The embodiment of personal traits and characteristics of an individual that are set at a very early age and extremely resistant to change.

P-factor.

A tendency for an aircraft to yaw to the left due to the descending propeller blade on the right producing more thrust than the ascending blade on the left. This occurs when the aircraft’s longitudinal axis is in a climbing attitude in relation to the relative wind. The P-factor would be to the right if the aircraft had a counterclockwise rotating propeller.

PFD.

See primary flight display.

Phugoid oscillations.

Long-period oscillations of an aircraft around its lateral axis. It is a slow change in pitch accompanied by equally slow changes in airspeed. Angle of attack remains constant, and the pilot often corrects for phugoid oscillations without even being aware of them.

PIC.

See pilot in command.

Pilotage.

Navigation by visual reference to landmarks.

Pilot in command (PIC).

The pilot responsible for the operation and safety of an aircraft.

Pilot report (PIREP).

Report of meteorological phenomena encountered by aircraft.

Pilot’s Operating Handbook/Airplane Flight Manual (POH/AFM).

FAA-approved documents published by the airframe manufacturer that list the operating conditions for a particular model of aircraft.

PIREP.

See pilot report.

Pitot pressure.

Ram air pressure used to measure airspeed.

Pitot-static head.

A combination pickup used to sample pitot pressure and static air pressure.