G-23
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.
Plan view. The overhead view of an approach procedure on
an instrument approach chart. The plan view depicts the routes
that guide the pilot from the en route segments to the IAF.
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.
Point-in-space approach. A type of helicopter instrument
approach procedure to a missed approach point more than
2,600 feet from an associated helicopter landing area.
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. A standard instrument approach
procedure in which both vertical and horizontal guidance
is provided.
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.
Precision approach radar (PAR). A type of radar used
at an airport to guide an aircraft through the final stages of
landing, providing horizontal and vertical guidance. The
radar operator directs the pilot to change heading or adjust
the descent rate to keep the aircraft on a path that allows it
to touch down at the correct spot on the runway.
Precision runway monitor (PRM). System allows
simultaneous, independent instrument flight rules (IFR)
approaches at airports with closely spaced parallel runways.
Preferred IFR routes. Routes established in the major
terminal and en route environments to increase system
efficiency and capacity. IFR clearances are issued based
on these routes, listed in the Chart Supplement U.S. except
when severe weather avoidance procedures or other factors
dictate otherwise.
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.
G-24
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 and supporting. A method of attitude instrument
flying using the instrument that provides the most direct
indication of attitude and performance.
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.
PRM. See precision runway monitor.
Procedure turn. A maneuver prescribed when it is necessary
to reverse direction to establish an aircraft on the intermediate
approach segment or final approach course.
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. 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.
R
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.
G-25
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.
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.
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 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.
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.
G-26
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.
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.
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.
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.
RVR. See runway visual range.
RVV. See runway visibility value.
S
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.
G-27
SDF. See simplified directional facility.
Selective availability (SA). A satellite technology permitting
the Department of Defense (DOD) to create, in the interest
of national security, a significant clock and ephemeris error
in the satellites, resulting in a navigation error.
Semicircular canal. An inner ear organ that detects angular
acceleration of the body.
Semimonocoque. A fuselage design that includes a
substructure of bulkheads and/or formers, along with stringers,
to support flight loads and stresses imposed on the fuselage.
Sensitive altimeter. A form of multipointer pneumatic
altimeter with an adjustable barometric scale that allows the
reference pressure to be set to any desired level.
Service ceiling. The maximum density altitude where the best
rate-of-climb airspeed will produce a 100-feet-per-minute
climb at maximum weight while in a clean configuration
with maximum continuous power.
Servo. A motor or other form of actuator which receives a
small signal from the control device and exerts a large force
to accomplish the desired work.
Servo tab. An auxiliary control mounted on a primary control
surface, which automatically moves in the direction opposite
the primary control to provide an aerodynamic assist in the
movement of the control.
SIDS. See standard instrument departure procedures.
SIGMET. The acronym for Significant Meteorological
information. A weather advisory in abbreviated plain
language concerning the occurrence or expected occurrence
of potentially hazardous en route weather phenomena that may
affect the safety of aircraft operations. SIGMET is warning
information, hence it is of highest priority among other types
of meteorological information provided to the aviation users.
Signal-to-noise ratio. An indication of signal strength
received compared to background noise, which is a measure
of the adequacy of the received signal.
Significant weather prognostic. Presents four panels
showing forecast significant weather.
Simplex. Transmission and reception on the same frequency.
Simplified directional facility (SDF). A NAVAID used
for nonprecision instrument approaches. The final approach
course is similar to that of an ILS localizer; however, the
SDF course may be offset from the runway, generally not
more than 3°, and the course may be wider than the localizer,
resulting in a lower degree of accuracy.
Single-pilot resource management (SRM). The ability
for a pilot to manage all resources effectively to ensure the
outcome of the flight is successful.
Situational awareness. Pilot knowledge of where the aircraft
is in regard to location, air traffic control, weather, regulations,
aircraft status, and other factors that may affect flight.
Skidding turn. An uncoordinated turn in which the rate of
turn is too great for the angle of bank, pulling the aircraft to
the outside of the turn.
Skills and procedures. The procedural, psychomotor, and
perceptual skills used to control a specific aircraft or its
systems. They are the airmanship abilities that are gained
through conventional training, are perfected, and become
almost automatic through experience.
Skin friction drag. Drag generated between air molecules
and the solid surface of the aircraft.
Slant range. The horizontal distance from the aircraft antenna
to the ground station, due to line-of-sight transmission of the
DME signal.
Slaved compass. A system whereby the heading gyro is
“slaved to,” or continuously corrected to bring its direction
readings into agreement with a remotely located magnetic
direction sensing device (usually a flux valve or flux gate
compass).
Slipping turn. An uncoordinated turn in which the aircraft
is banked too much for the rate of turn, so the horizontal lift
component is greater than the centrifugal force, pulling the
aircraft toward the inside of the turn.
Small airplane. An airplane of 12,500 pounds or less
maximum certificated takeoff weight.
Somatogravic illusion. The misperception of being
in a nose-up or nose-down attitude, caused by a rapid
acceleration or deceleration while in flight situations that
lack visual reference.
G-28
Spatial disorientation. The state of confusion due to
misleading information being sent to the brain from various
sensory organs, resulting in a lack of awareness of the aircraft
position in relation to a specific reference point.
Special flight permit. A flight permit issued to an aircraft
that does not meet airworthiness requirements but is capable
of safe flight. A special flight permit can be issued to move
an aircraft for the purposes of maintenance or repair, buyer
delivery, manufacturer flight tests, evacuation from danger,
or customer demonstration. Also referred to as a ferry permit.
Special use airspace. Airspace in which flight activities are
subject to restrictions that can create limitations on the mixed
use of airspace. Consists of prohibited, restricted, warning,
military operations, and alert areas.
Special fuel consumption. The amount of fuel in pounds
per hour consumed or required by an engine per brake
horsepower or per pound of thrust.
Speed. The distance traveled in a given time.
Spin. An aggravated stall that results in an airplane
descending in a helical, or corkscrew path.
Spiral instability. A condition that exists when the static
directional stability of the airplane is very strong as compared
to the effect of its dihedral in maintaining lateral equilibrium.
Spiraling slipstream. The slipstream of a propeller-driven
airplane rotates around the airplane. This slipstream strikes
the left side of the vertical fin, causing the aircraft to yaw
slightly. Rudder offset is sometimes used by aircraft designers
to counteract this tendency.
Spoilers. High-drag devices that can be raised into the air
flowing over an airfoil, reducing lift and increasing drag.
Spoilers are used for roll control on some aircraft. Deploying
spoilers on both wings at the same time allows the aircraft
to descend without gaining speed. Spoilers are also used to
shorten the ground roll after landing.
SRM. See single-pilot resource management.
SSR. See secondary surveillance radar.
SSV. See standard service volume.
Stabilator. A single-piece horizontal tail surface on an
airplane that pivots around a central hinge point. A stabilator
serves the purposes of both the horizontal stabilizer and the
elevators.
Stability. The inherent quality of an airplane to correct for
conditions that may disturb its equilibrium, and to return
or to continue on the original flight path. It is primarily an
airplane design characteristic.
Stagnant hypoxia. A type of hypoxia that results when the
oxygen-rich blood in the lungs is not moving to the tissues
that need it.
Stall. A rapid decrease in lift caused by the separation of
airflow from the wing’s surface, brought on by exceeding
the critical angle of attack. A stall can occur at any pitch
attitude or airspeed.
Standard atmosphere. At sea level, the standard atmosphere
consists of a barometric pressure of 29.92 inches of mercury
("Hg) or 1013.2 millibars, and a temperature of 15 °C (59
°F). Pressure and temperature normally decrease as altitude
increases. The standard lapse rate in the lower atmosphere for
each 1,000 feet of altitude is approximately 1 "Hg and 2 °C
(3.5 °F). For example, the standard pressure and temperature
at 3,000 feet mean sea level (MSL) are 26.92 "Hg (29.92
"Hg – 3 "Hg) and 9 °C (15 °C – 6 °C).
Standard empty weight (GAMA). This weight consists of
the airframe, engines, and all items of operating equipment
that have fixed locations and are permanently installed in the
airplane including fixed ballast, hydraulic fluid, unusable
fuel, and full engine oil.
Standard holding pattern. A holding pattern in which all
turns are made to the right.
Standard instrument departure procedures (SIDS).
Published procedures to expedite clearance delivery and to
facilitate transition between takeoff and en route operations.
Standard rate turn. A turn in which an aircraft changes its
direction at a rate of 3° per second (360° in 2 minutes) for
low- or medium-speed aircraft. For high-speed aircraft, the
standard rate turn is 1½° per second (360° in 4 minutes).
Standard service volume (SSV). Defines the limits of the
volume of airspace which the VOR serves.
Standard terminal arrival route (STAR). A preplanned
IFR ATC arrival procedure published for pilot use in graphic
and/or textual form.
Standard weights. Weights established for numerous items
involved in weight and balance computations. These weights
should not be used if actual weights are available.
G-29
STAR. See standard terminal arrival route.
Static longitudinal stability. The aerodynamic pitching
moments required to return the aircraft to the equilibrium
angle of attack.
Static pressure. Pressure of air that is still or not moving,
measured perpendicular to the surface of the aircraft.
Static stability. The initial tendency an aircraft displays
when disturbed from a state of equilibrium.
Station. A location in the airplane that is identified by a
number designating its distance in inches from the datum.
The datum is, therefore, identified as station zero. An item
located at station +50 would have an arm of 50 inches.
Stationary front. A front that is moving at a speed of less
than 5 knots.
Steep turns. In instrument flight, any turn greater than standard
rate; in visual flight, anything greater than a 45° bank.
Stepdown fix. The point after which additional descent is
permitted within a segment of an IAP.
Strapdown system. An INS in which the accelerometers
and gyros are permanently “strapped down” or aligned with
the three axes of the aircraft.
Stratoshere. A layer of the atmosphere above the tropopause
extending to a height of approximately 160,000 feet.
Stress. The body’s response to demands placed upon it.
Stress management. The personal analysis of the kinds of
stress experienced while flying, the application of appropriate
stress assessment tools, and other coping mechanisms.
Structural icing. The accumulation of ice on the exterior
of the aircraft.
Sublimation. Process by which a solid is changed to a gas
without going through the liquid state.
Suction relief valve. A relief valve in an instrument vacuum
system required to maintain the correct low pressure inside
the instrument case for the proper operation of the gyros.
Supercharger. An engine- or exhaust-driven air compressor
used to provide additional pressure to the induction air so the
engine can produce additional power.
Supercooled water droplets. Water droplets that have been
cooled below the freezing point, but are still in a liquid state.
Surface analysis chart. A report that depicts an analysis of
the current surface weather. Shows the areas of high and low
pressure, fronts, temperatures, dewpoints, wind directions
and speeds, local weather, and visual obstructions.
Synchro. A device used to transmit indications of angular
movement or position from one location to another.
Synthetic vision. A realistic display depiction of the aircraft
in relation to terrain and flight path.
T
TAA. See terminal arrival area.
TACAN. See tactical air navigation.
Tactical air navigation (TACAN). An electronic navigation
system used by military aircraft, providing both distance and
direction information.
Takeoff decision speed (V 1). Per 14 CFR section 23.51:
“the calibrated airspeed on the ground at which, as a result
of engine failure or other reasons, the pilot assumed to have
made a decision to continue or discontinue the takeoff.”
Takeoff distance. The distance required to complete an
all-engines operative takeoff to the 35-foot height. It must
be at least 15 percent less than the distance required for a
one-engine inoperative engine takeoff. This distance is not
normally a limiting factor as it is usually less than the one-
engine inoperative takeoff distance.
Takeoff safety speed (V2). Per 14 CFR part 1: “A referenced
airspeed obtained after lift-off at which the required one-
engine-inoperative climb performance can be achieved.”
TAWS. See terrain awareness and warning system.
Taxiway lights. Omnidirectional lights that outline the edges
of the taxiway and are blue in color.
Taxiway turnoff lights. Lights that are flush with the runway
which emit a steady green color.
TCAS. See traffic alert collision avoidance system.
TCH. See threshold crossing height.
TDZE. See touchdown zone elevation.