Aeronautical Terms beginning with H
HAA
Height Above Airport.
Hail
A form of precipitation composed of balls or irregular lumps of ice, always produced by convective clouds which are nearly always cumulonimbus.
HAL
Height Above Landing.
Halo
A prismatically colored or whitish circle or arcs of a circle with the sun or moon at its center; coloration, if not white, is from red inside to blue outside (opposite that of a corona); fixed in size with an angular diameter of 22° (common) or 46° (rare); characteristic of clouds composed of ice crystals; valuable in differentiating between cirriform and forms of lower clouds.
Hand Propping
Starting an engine by rotating the propeller by hand.
Handoff
An action taken to transfer the radar identification of an aircraft from one controller to another if the aircraft will enter the receiving controller’s airspace and radio communications with the aircraft will be transferred.
HAT
Height Above Touchdown Elevation.
Have Numbers
Used by pilots to inform ATC that they have received runway, wind, and altimeter information only.
Hazardous attitudes
Five aeronautical decision-making attitudes that may contribute to poor pilot judgment: antiauthority, impulsivity, invulnerability, machismo, and resignation.
Hazardous attitudes
Five aeronautical decision-making attitudes that may contribute to poor pilot judgment: anti-authority, impulsivity, invulnerability, machismo, and resignation.
Hazardous Inflight Weather Advisory Service
Continuous recorded hazardous inflight weather forecasts broadcasted to airborne pilots over selected VOR outlets defined as an HIWAS Broadcast Area. Discontinued on January 8, 2020.
Hazardous Inflight Weather Advisory Service (HIWAS)
Service providing recorded weather forecasts broadcast to airborne pilots over selected VORs. Discontinued on January 8, 2020.
Hazardous Inflight Weather Advisory Service (HIWAS).
Service providing recorded weather forecasts broadcast to airborne pilots over selected VORs. Discontinued on January 8, 2020.
Hazardous Weather Information
Summary of significant meteorological information (SIGMET/WS), convective significant meteorological information (convective SIGMET/WST), urgent pilot weather reports (urgent PIREP/UUA), center weather advisories (CWA), airmen’s meteorological information (AIRMET/WA) and any other weather such as isolated thunderstorms that are rapidly developing and increasing in intensity, or low ceilings and visibilities that are becoming widespread which is considered significant and are not included in a current hazardous weather advisory.
Hazardous Weather Information
Summary of SIGMETs, Convective SIGMETs, urgent Pilot Weather Reports (PIREP), CWAs, AIRMETs, and any other significant weather provided to pilots that might not be routinely provided in a standard format or report.
Haze
A type of lithometeor composed of fine dust or salt particles dispersed through a portion of the atmosphere; particles are so small they cannot be felt or individually seen with the naked eye (as compared with the larger particles of dust), but diminish the visibility; distinguished from fog by its bluish or yellowish tinge.
HDTA
High Density Traffic Airports
Head-Up Display (HUD)
See Head-Up Guidance System (HGS)
Head-up display (HUD)
A special type of flight viewing screen that allows the pilot to watch the flight instruments and other data while looking through the windshield of the aircraft for other traffic, the approach lights, or the runway.
Head-Up Guidance System (HGS)
A system which projects critical flight data on a display positioned between the pilot and the windscreen. In addition to showing primary flight information, the HUD computes an extremely accurate instrument approach and landing guidance solution, and displays the result as a guidance cue for head-up viewing by the pilot.
Heading
The direction in which the nose of the aircraft is pointing during flight.
Heading
The direction in which the nose of the aircraft is pointing during flight.
Heading Bug
A marker on the heading indicator that can be rotated to a specific heading for reference purposes, or to command an autopilot to fly that heading.
Heading Indicator
An instrument which senses airplane movement and displays heading based on a 360º azimuth, with the final zero omitted. The heading indicator, also called a directional gyro, is fundamentally a mechanical instrument designed to facilitate the use of the magnetic compass. The heading indicator is not affected by the forces that make the magnetic compass difficult to interpret.
Heading indicator
An instrument which senses airplane movement and displays heading based on a 360° azimuth, with the final zero omitted. The heading indicator, also called a directional gyro (DG), is fundamentally a mechanical instrument designed to facilitate the use of the magnetic compass. The heading indicator is not affected by the forces that make the magnetic compass difficult to interpret.
Headwind Component
The component of atmospheric winds that acts opposite to the aircraft’s flightpath.
Headwork
Required to accomplish a conscious, rational thought process when making decisions. Good decision-making involves risk identification and assessment, information processing, and problem solving.
Heavy
An Aircraft Class Wake Turbulence Separation Minima. Aircraft capable of takeoff weights of 300,000 pounds or more whether or not they are operating at this weight during a particular phase of flight.
Height Above Airport
The height of the Minimum Descent Altitude above the published airport elevation. This is published in conjunction with circling minimums.
Height Above Landing
The height above a designated helicopter landing area used for helicopter instrument approach procedures.
Height Above Touchdown
The height of the Decision Height or Minimum Descent Altitude above the highest runway elevation in the touchdown zone (first 3,000 feet of the runway). HAT is published on instrument approach charts in conjunction with all straight-in minimums.
Height above touchdown elevation (HAT)
The DA/DH or MDA above the highest runway elevation in the touchdown zone (first 3,000 feet of the runway).
Helicopter
A rotorcraft that, for its horizontal motion, depends principally on its engine-driven rotors.
Helipad
A small, designated area, usually with a prepared surface, on a heliport, airport, landing/takeoff area, apron/ramp, or movement area used for takeoff, landing, or parking of helicopters.
Heliport
An area of land, water, or structure used or intended to be used for the landing and takeoff of helicopters.
Heliport
An area of land, water, or structure used or intended to be used for the landing and takeoff of helicopters and includes its buildings and facilities if any.
Heliport Reference Point (HRP)
The geographic center of a heliport.
HEMS
Helicopter Emergency Medical Service
HEMS
Helicopter Emergency Medical Services
Hertz
The standard radio equivalent of frequency in cycles per second of an electromagnetic wave. Kilohertz (kHz) is a frequency of one thousand cycles per second. Megahertz (MHz) is a frequency of one million cycles per second.
HF
High Frequency.
HF
High Frequency.
HF Communications
High Frequency Communications.
HFDL
High Frequency Data Link
Hg
Abbreviation for mercury, from the Latin hydrargyrum.
Hg
Abbreviation for mercury, from the Latin hydrargyrum.
Hierarchy of human needs
A listing by Abraham Maslow of needs, from the most basic to the most fulfilling: physiological, security, belonging, esteem, cognitive and aesthetic, and self-actualization.
High
An area of high barometric pressure, with its attendant system of winds; an anticyclone. Also high pressure system.
High Frequency
The frequency band between 3 and 30 MHz.
High Frequency Communications
High radio frequencies (HF) between 3 and 30 MHz used for air-to-ground voice communication in overseas operations.
High Performance Aircraft
An aircraft with an engine of more than 200 horsepower.
High performance aircraft
An aircraft with an engine of more than 200 horsepower.
High Speed Exit
High Speed Taxiway.
High Speed Taxiway
A long radius taxiway designed and provided with lighting or marking to define the path of aircraft, traveling at high speed (up to 60 knots), from the runway center to a point on the center of a taxiway. Also referred to as long radius exit or turn-off taxiway. The high speed taxiway is designed to expedite aircraft turning off the runway after landing, thus reducing runway occupancy time.
High Speed Turnoff
High Speed Taxiway.
Highway in the Sky (HITS)
A graphically intuitive pilot interface system that provides an aircraft operator with all of the attitude and guidance inputs required to safely fly an aircraft in close conformance to air traffic procedures.
HIRL
High-Intensity Runway Light System.
HIRL
High Intensity Runway Lights
Histotoxic hypoxia
The inability of cells to effectively use oxygen. Plenty of oxygen is being transported to the cells that need it, but they are unable to use it.
HITS
Highway In The Sky
HIWAS
Hazardous Inflight Weather Advisory Service. Discontinued on January 8, 2020.
HIWAS
Hazardous Inflight Weather Advisory Service. Discontinued on January 8, 2020.
HIWAS
Hazardous Inflight Weather Advisory Service. Discontinued on January 8, 2020.
Hold For Release
Used by ATC to delay an aircraft for traffic management reasons; i.e., weather, traffic volume, etc. Hold for release instructions (including departure delay information) are used to inform a pilot or a controller (either directly or through an authorized relay) that an IFR departure clearance is not valid until a release time or additional instructions have been received.
Hold In Lieu Of Procedure Turn
A hold in lieu of procedure turn shall be established over a final or intermediate fix when an approach can be made from a properly aligned holding pattern. The hold in lieu of procedure turn permits the pilot to align with the final or intermediate segment of the approach and/or descend in the holding pattern to an altitude that will permit a normal descent to the final approach fix altitude. The hold in lieu of procedure turn is a required maneuver (the same as a procedure turn) unless the aircraft is being radar vectored to the final approach course, when “NoPT” is shown on the approach chart, or when the pilot requests or the controller advises the pilot to make a “straight-in” approach.
Hold Procedure
A predetermined maneuver which keeps aircraft within a specified airspace while awaiting further clearance from air traffic control. Also used during ground operations to keep aircraft within a specified area or at a specified point while awaiting further clearance from air traffic control.
Hold-Short Point
A point on the runway beyond which a landing aircraft with a LAHSO clearance is not authorized to proceed. This point may be located prior to an intersecting runway, taxiway, predetermined point, or approach/departure flight path.
Hold-Short Position Lights
Flashing in-pavement white lights located at specified hold-short points.
Hold-Short Position Marking
The painted runway marking located at the hold-short point on all LAHSO runways.
Hold-Short Position Signs
Red and white holding position signs located alongside the hold-short point.
Holding
A predetermined maneuver that keeps aircraft within a specified airspace while awaiting further clearance from ATC.
Holding Fix
A specified fix identifiable to a pilot by NAVAIDs or visual reference to the ground used as a reference point in establishing and maintaining the position of an aircraft while holding.
Holding pattern
A racetrack pattern, involving two turns and two legs, used to keep an aircraft within a prescribed airspace with respect to a geographic fix. A standard pattern uses right turns; nonstandard patterns use left turns.
Homing
Flying the aircraft on any heading required to keep the needle pointing to the 0 relative bearing position.
Horizon
The line of sight boundary between the earth and the sky.
Horizontal situation indicator (HSI)
A flight navigation instrument that combines the heading indicator with a CDI, in order to provide the pilot with better situational awareness of location with respect to the courseline.
Horizontal situation indicator (HSI)
A flight navigation instrument that combines the heading indicator with a CDI, in order to provide the pilot with better situational awareness of location with respect to the courseline.
Horsepower
The term, originated by inventor James Watt, means the amount of work a horse could do in one second. One horsepower equals 550 foot-pounds per second, or 33,000 foot-pounds per minute.
Hot Start
In gas turbine engines, a start which occurs with normal engine rotation, but exhaust temperature exceeds prescribed limits. This is usually caused by an excessively rich mixture in the combustor. The fuel to the engine must be terminated immediately to prevent engine damage.
Hover Check
Used to describe when a helicopter/VTOL aircraft requires a stabilized hover to conduct a performance/power check prior to hover taxi, air taxi, or takeoff. Altitude of the hover will vary based on the purpose of the check.
Hover Taxi
Used to describe a helicopter/VTOL aircraft movement conducted above the surface and in ground effect at airspeeds less than approximately 20 knots. The actual height may vary, and some helicopters may require hover taxi above 25 feet AGL to reduce ground effect turbulence or provide clearance for cargo slingloads.
How Do You Hear Me?
A question relating to the quality of the transmission or to determine how well the transmission is being received.
HRR
Helicopter Rapid Refueling Procedures
HSAC
Helicopter Safety Advisory Council
HSI
Horizontal Situation Indicator.
HSI
Horizontal Situation Indicator.
HUD
Head-Up Display.
HUD
Head-Up Display.
Human factors
A multidisciplinary field encompassing the behavioral and social sciences, engineering, and physiology, to consider the variables that influence individual and crew performance for the purpose of optimizing human performance and reducing errors.
Human factors
A multidisciplinary field devoted to optimizing human performance and reducing human error. It incorporates the methods and principles of the behavioral and social sciences, engineering, and physiology. It may be described as the applied science which studies people working together in concert with machines. Human factors involve variables that influence individual performance, as well as team or crew performance.
Human factors
A multidisciplinary field encompassing the behavioral and social sciences, engineering, and physiology, to consider the variables that influence individual and crew performance for the purpose of optimizing human performance and reducing errors.
Human nature
The general psychological characteristics, feelings, and behavioral traits shared by all humans.
Humidity
Water vapor content of the air; may be expressed as specific humidity, relative humidity, or mixing ratio.
Hung Start
In gas turbine engines, a condition of normal light off but with r.p.m. remaining at some low value rather than increasing to the normal idle r.p.m. This is often the result of insufficient power to the engine from the starter. In the event of a hung start, the engine should be shut down.
Hurricane
A tropical cyclone in the Western Hemisphere with winds in excess of 65 knots or 120 km/h.
Hydraulics
The branch of science that deals with the transmission of power by incompressible fluids under pressure.
Hydrometeor
A general term for particles of liquid water or ice such as rain, fog, frost, etc., formed by modification of water vapor in the atmosphere; also water or ice particles lifted from the earth by the wind such as sea spray or blowing snow.
Hydroplaning
A condition that exists when landing on a surface with standing water deeper than the tread depth of the tires. When the brakes are applied, there is a possibility that the brake will lock up and the tire will ride on the surface of the water, much like a water ski. When the tires are hydroplaning, directional control and braking action are virtually impossible. An effective anti-skid system can minimize the effects of hydroplaning.
Hydroplaning
A condition that exists when landing on a surface with standing water deeper than the tread depth of the tires. When the brakes are applied, there is a possibility that the brake will lock up and the tire will ride on the surface of the water, much like a water ski. When the tires are hydroplaning, directional control and braking action are virtually impossible. An effective anti-skid system can minimize the effects of hydroplaning.
Hygrograph
The record produced by a continuous-recording hygrometer.
Hygrometer
An instrument for measuring the water vapor content of the air.
Hypemic hypoxia
A type of hypoxia that is a result of oxygen deficiency in the blood, rather than a lack of inhaled oxygen. It can be caused by a variety of factors. Hypemic means “not enough blood.”.
Hyperventilation
Occurs when an individual is experiencing emotional stress, fright, or pain, and the breathing rate and depth increase, although the carbon dioxide level in the blood is already at a reduced level. The result is an excessive loss of carbon dioxide from the body, which can lead to unconsciousness due to the respiratory system’s overriding mechanism to regain control of breathing.
Hypoxia
A lack of sufficient oxygen reaching the body tissues.
Hypoxia
A state of oxygen deficiency in the body sufficient to impair functions of the brain and other organs.
Hypoxic hypoxia
This type of hypoxia is a result of insufficient oxygen available to the lungs. A decrease of oxygen molecules at sufficient pressure can lead to hypoxic hypoxia.
Hz
Hertz
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