Aeronautical Terms beginning with G

G/S

Glide Slope

GA

General Aviation

GA CDR

General Aviation Coded Departure Routes (GA CDR) - The CDR program provides a rapid means to reroute aircraft when the filed route is constrained by either weather or congestion. Historically, abbreviated CDR clearances have only been issued to airline customers who have signed a Memorandum of Agreement (MOA) with the facilities that issue abbreviated CDR clearances. Recently, general aviation customers have requested the use of this reroute capability. This change permits general aviation customers to communicate to Air Traffic Control (ATC) facilities their ability and willingness to accept CDRs and their capability to accept abbreviated clearances associated with CDRs. Please see the GA CDR Advisory circular for more details.

GAMA

General Aviation Manufacturers Association

Gas Generator

The basic power producing portion of a gas turbine engine and excluding such sections as the inlet duct, the fan section, free power turbines, and tailpipe. Each manufacturer designates what is included as the gas generator, but generally consists of the compressor, diffuser, combustor, and turbine.

Gas Turbine Engine

A form of heat engine in which burning fuel adds energy to compressed air and accelerates the air through the remainder of the engine. Some of the energy is extracted to turn the air compressor, and the remainder accelerates the air to produce thrust. Some of this energy can be converted into torque to drive a propeller or a system of rotors for a helicopter.

Gate Hold Procedures

Procedures at selected airports to hold aircraft at the gate or other ground location whenever departure delays exceed or are anticipated to exceed 15 minutes. The sequence for departure will be maintained in accordance with initial call-up unless modified by flow control restrictions. Pilots should monitor the ground control/clearance delivery frequency for engine start/taxi advisories or new proposed start/taxi time if the delay changes.

Gateway Fix

A navigational aid or fix where an aircraft transitions between the domestic route structure and the oceanic route airspace.

GBAS

Ground Based Augmentation System

GBT

Ground-Based Transmitter

GCA

Ground Controlled Approach

GCO

Ground Communication Outlet

GDP

Ground Delay Programs

GDPE

Ground Delay Program Enhancements

General Aviation

That portion of civil aviation which encompasses all facets of aviation except air carriers holding a certificate of public convenience and necessity from the Civil Aeronautics Board and large aircraft commercial operators.

General Aviation [ICAO]

All civil aviation operations other than scheduled air services and nonscheduled air transport operations for remuneration or hire.

GEO

Geostationary Satellite

Geo Map

The digitized map markings associated with the ASR-9 Radar System.

Geodetic Datum

The reference plane from which geodetic calculations are made. Or, according to ICAO Annex 15, the numerical or geometrical quantity or set of such quantities (mathematical model) that serves as a reference for computing other quantities in a specific geographic region such as the latitude and longitude of a point.

Geographic Position Markings

Geographic Position Markings are located at points along low visibility taxi routes designated in the airport's Surface Movement Guidance Control System (SMGCS) plan. They are used to identify the location of taxiing aircraft during low visibility operations. Low visibility operations are those that occur when the runway visible range (RVR) is below 1200 feet(360m). They are positioned to the left of the taxiway centreline in the direction of taxiing.

Gimbal ring

A type of support that allows an object, such as a gyroscope, to remain in an upright condition when its base is tilted.

Glaze

A coating of ice, generally clear and smooth, formed by freezing of super.cooled water on a surface.

Glide Ratio

The ratio between distance traveled and altitude lost during non-powered flight.

Glide slope (GS)

Part of the ILS that projects a radio beam upward at an angle of approximately 3° from the approach end of an instrument runway. The glide slope provides vertical guidance to aircraft on the final approach course for the aircraft to follow when making an ILS approach along the localizer path.

Glide slope intercept altitude

The minimum altitude of an intermediate approach segment prescribed for a precision approach that ensures obstacle clearance.

Glidepath

The path of an aircraft relative to the ground while approaching a landing.

Glidepath Angle (GPA)

The angular displacement of the vertical guidance path from a horizontal plane that passes through the reference datum point (RDP). This angle is published on approach charts (e.g., 3.00, 3.20, etc.). GPA is sometimes referred to as vertical path angle (VPA).

Glidepath Intercept Altitude

Glideslope Intercept Altitude.

Glidepath [ICAO]

A descent profile determined for vertical guidance during a final approach.

Glider

A heavier-than-air aircraft, that is supported in flight by the dynamic reaction of the air against its lifting surfaces and whose free flight does not depend principally on an engine.

Glideslope

Provides vertical guidance for aircraft during approach and landing. The glideslope/glidepath is based on the following: a. Electronic components emitting signals which provide vertical guidance by reference to airborne instruments during instrument approaches such as ILS/MLS, or b. Visual ground aids, such as VASI, which provide vertical guidance for a VFR approach or for the visual portion of an instrument approach and landing. c. PAR. Used by ATC to inform an aircraft making a PAR approach of its vertical position (elevation) relative to the descent profile.

Glideslope (GS)

Part of the ILS that projects a radio beam upward at an angle of approximately 3° from the approach end of an instrument runway. The glideslope provides vertical guidance to aircraft on the final approach course for the aircraft to follow when making an ILS approach along the localizer path.

Glideslope intercept altitude

The minimum altitude of an intermediate approach segment prescribed for a precision approach that ensures obstacle clearance.

Global landing system (GLS)

An instrument approach with lateral and vertical guidance with integrity limits (similar to barometric vertical navigation (BRO VNAV).

Global Navigation Satellite System (GNSS)

An umbrella term adopted by the International Civil Aviation Organization (ICAO) to encompass any independent satellite navigation system used by a pilot to perform onboard position determinations from the satellite data.

Global navigation satellite systems (GNSS)

Satellite navigation systems that provide autonomous geo-spatial positioning with global coverage. It allows small electronic receivers to determine their location (longitude, latitude, and altitude) to within a few meters using time signals transmitted along a line of sight by radio from satellites.

Global Position System (GPS)

A satellite-based radio positioning, navigation, and time-transfer system.

Global positioning system (GPS)

Navigation system that uses satellite rather than ground-based transmitters for location information.

GLS

Global Navigation Satellite System Landing System

GNE

Gross Navigation Error

GNSS

Global Navigation Satellite Systems.

GNSSP

Global Navigation Satellite System Panel

Go Ahead

Proceed with your message. Not to be used for any other purpose.

Go Around

Instructions for a pilot to abandon his/her approach to landing. Additional instructions may follow. Unless otherwise advised by ATC, a VFR aircraft or an aircraft conducting visual approach should overfly the runway while climbing to traffic pattern altitude and enter the traffic pattern via the crosswind leg. A pilot on an IFR flight plan making an instrument approach should execute the published missed approach procedure or proceed as instructed by ATC; e.g., “Go around” (additional instructions if required).

Go-Around

Terminating a landing approach.

Go-around power or thrust setting

The maximum allowable in-flight power or thrust setting identified in the performance data.

Goals and values

A perception factor that describes how a person’s perception of an event depends on beliefs. Motivation toward learning is affected by how much value a person puts on education. Instructors who have some idea of the goals and values of their students will be more successful in teaching them.

Goniometer

As used in radio frequency (RF) antenna systems, a direction-sensing device consisting of two fixed loops of wire oriented 90 from each other, which separately sense received signal strength and send those signals to two rotors (also oriented 90) in the sealed direction-indicating instrument. The rotors are attached to the direction-indicating needle of the instrument and rotated by a small motor until minimum magnetic field is sensed near the rotors.

Governing Range

The range of pitch a propeller governor can control during flight.

Governor

A control which limits the maximum rotational speed of a device.

GPD

Graphic Plan Display

GPS

Global Positioning System.

GPS Approach Overlay Program

An authorization for pilots to use GPS avionics under IFR for flying designated existing nonprecision instrument approach procedures, with the exception of LOC, LDA, and SDF procedures.

GPWS

Ground Proximity Warning System

Gradient

In meteorology, a horizontal decrease in value per unit distance of a parameter in the direction of maximum decrease; most commonly used with pressure, temperature, and moisture.

Graphic Plan Display (GPD)

A view available with URET that provides a graphic display of aircraft, traffic, and notification of predicted conflicts. Graphic routes for Current Plans and Trial Plans are displayed upon controller request.

Graveyard spiral

The illusion of the cessation of a turn while still in a prolonged, coordinated, constant rate turn, which can lead a disoriented pilot to a loss of control of the aircraft.

Great circle route

The shortest distance across the surface of a sphere (the Earth) between two points on the surface.

GRI

Group Repetition Interval

Gross Navigation Error (GNE)

In the North Atlantic area of operations, a gross navigation error is a lateral separation of more than 25 NM from the centerline of an aircrafts cleared route, which generates an Oceanic Navigation Error Report. This report is also generated by a vertical separation if you are more than 300 feet off your assigned flight level.

Gross Weight

The total weight of a fully loaded aircraft including the fuel, oil, crew, passengers, and cargo.

Ground Adjustable Trim Tab

A metal trim tab on a control surface that is not adjustable in flight. Bent in one direction or another while on the ground to apply trim forces to the control surface.

Ground clutter

Pertaining to radar, a cluster of echoes, generally at short range, reflected from ground targets.

Ground Communication Outlet (GCO)

An unstaffed, remotely controlled ground/ground communications facility. Pilots at uncontrolled airports may contact ATC and AFSS via Very High Frequency (VHF) radio to a telephone connection. This lets pilots obtain an instrument clearance or close a VFR/IFR flight plan.

Ground Controlled Approach

A radar approach system operated from the ground by air traffic control personnel transmitting instructions to the pilot by radio. The approach may be conducted with surveillance radar (ASR) only or with both surveillance and precision approach radar (PAR). Usage of the term “GCA” by pilots is discouraged except when referring to a GCA facility. Pilots should specifically request a “PAR” approach when a precision radar approach is desired or request an “ASR” or “surveillance” approach when a nonprecision radar approach is desired.

Ground Delay Program (GDP)

A traffic management process administered by the ATCSCC; when aircraft are held on the ground. The purpose of the program is to support the TM mission and limit airborne holding. It is a flexible program and may be implemented in various forms depending upon the needs of the AT system. Ground delay programs provide for equitable assignment of delays to all system users.

Ground Effect

A condition of improved performance encountered when an airplane is operating very close to the ground. When an airplane’s wing is under the influence of ground effect, there is a reduction in upwash, downwash, and wingtip vortices. As a result of the reduced wingtip vortices, induced drag is reduced.

Ground fog

In the United States, a fog that conceals less than 0.6 of the sky and is not contiguous with the base of clouds.

Ground Idle

Gas turbine engine speed usually 60-70 percent of the maximum r.p.m. range, used as a minimum thrust setting for ground operations.

Ground Loop

A sharp, uncontrolled change of direction of an airplane on the ground.

Ground Power Unit (GPU)

A type of small gas turbine whose purpose is to provide electrical power, and/or air pressure for starting aircraft engines. A ground unit is connected to the aircraft when needed. Similar to an aircraft-installed auxiliary power unit.

Ground proximity warning system (GPWS)

A system designed to determine an aircrafts clearance above the Earth and provides limited predictability about aircraft position relative to rising terrain.

Ground Speed

The speed of an aircraft relative to the surface of the earth.

Ground Stop (GS)

The GS is a process that requires aircraft that meet a specific criteria to remain on the ground. The criteria may be airport specific, airspace specific, or equipment specific; for example, all departures to San Francisco, or all departures entering Yorktown sector, or all Category I and II aircraft going to Charlotte. GSs normally occur with little or no warning.

Ground Track

The aircraft’s path over the ground when in flight.

Ground visibility

Prevailing horizontal visibility near the earth’s surface as reported by the United States National Weather Service or an accredited observer.

Ground Visibility [ICAO]

The visibility at an aerodrome as reported by an accredited observer.

Ground-Based Transceiver (GBT)

The ground-based transmitter/receiver (transceiver) receives automatic dependent surveillance-broadcast messages, which are forwarded to an air traffic control facility for processing and display with other radar targets on the plan position indicator (radar display).

Groundspeed

Speed over the ground, either closing speed to the station or waypoint, or speed over the ground in whatever direction the aircraft is going at the moment, depending upon the navigation system used.

Groundspeed (GS)

The actual speed of the airplane over the ground. It is true airspeed adjusted for wind. Groundspeed decreases with a headwind, and increases with a tailwind.

Groundspeed Measurement System

A measurement system for determining the groundspeed of an aircraft during final approach and landing, by measuring at the aircraft the Doppler shift of a radio signal, and/or its modulation components, transmitted by a fixed ground station.

GS

Glide Slope.

GSD

Geographical Situation Display

Guided discussion method

An educational presentation typically used in the classroom where the topic to be covered by a group is introduced and the instructor participates only as necessary to keep the group focused on the subject.

GUS

Ground Uplink Station

Gust

A sudden brief increase in wind; according to U.S. weather observing practice, gusts are reported when the variation in wind speed between peaks and lulls is at least 10 knots.

Gust Penetration Speed

The speed that gives the greatest margin between the high and low mach speed buffets.

GWPS

Ground Proximity Warning System.

GWS

Graphical Weather Service

Gyrodyne

A rotorcraft whose rotors are normally engine-driven for takeoff, hovering, and landing, and for forward flight through part of its speed range, and whose means of propulsion, consisting usually of conventional propellers, is independent of the rotor system.

Gyroplane

A rotorcraft whose rotors are not engine-driven, except for initial starting, but are made to rotate by action of the air when the rotorcraft is moving; and whose means of propulsion, consisting usually of conventional propellers, is independent of the rotor system.

Gyroscopic Precession

An inherent quality of rotating bodies, which causes an applied force to be manifested 90º in the direction of rotation from the point where the force is applied.