Aircraft Icing Training: Glossary
Above Ground Level (AGL) Altitude Altitude expressed in feet measured aboveground level.
Accretion Thegrowth of ice on aircraft surfaces in flight as a result of the collision withsupercooled liquid water cloud droplets.
Active Frost: Frostthat actively grows in mass and thickness. This phenomenon occurs when aircraftsurfaces are at or below freezing (0ºC) AND at or below dew point.
Aerodynamic Acceptance TestLaboratory test that establish if deicing and anti-icing fluids meet flowoff requirements during takeoff ground acceleration and climb.
Aeronautical Information Manual (AIM) A primary FAA publication whose purpose is toinstruct airmen about operating in the National Airspace System of the
Air mass Awidespread body of air in which its homogeneous properties were establishedwhile that air was over a particularregion of the earth's surface and that undergoes specific modifications whilemoving away from its source region.
Air Operator: Theholder of an air operator certificate.
Air Operator Certificate: A certificate issued under the CARs that authorizes the holder of thecertificate to operate a commercial air service.
Aircraft Deicing FacilityA facility where:
•frost, snow or ice are removed (deicing) from an aircraft in order to provideclean surfaces; and/or
•Critical surfaces of the aircraft receive protection (anti-icing) against theformation of frost or ice, or the accumulation of snow or slush for a limited period of time.
•Fluid Storage, Equipment Maintenance, Environmental Mitigation, Control Centreprograms are in place.
Aircraft Deicing Pad: A designated area on an aircraft deicing facility intended to be used forparking an aircraft to conduct deicing or anti-icing activities, consisting of an inner area for the parkingof an aircraft to receive deicing/antiicing treatment. On a centralized deicing facility, the aircraft deicing pad also includes anouter area for maneuvering deicing vehicles (safe zone). The outer area provides the vehicle lane width necessaryfor deicing vehicles to safely perform during the deicing operation.
AIRMETIn-flightweather advisories issued only to amend the area forecast concerning weatherphenomena that are of operational interest to all aircraft and potentially hazardous to aircrafthaving limited capability because of lack of equipment,instrumentation, or pilot qualifications. AIRMETs concern weather of lessseverity than that covered by SIGMETsor Convective SIGMETs. AIRMETs cover moderate icing, moderate turbulence,sustained winds of 30 knots or more at the surface, widespread areas of ceilings less than 1,000 feet and/orvisibility less than 3 miles, and extensive mountain obscurement.
AirspeedThespeed of an aircraft relative to its surrounding air mass. The unqualified term"airspeed" means one of the following: Indicated Airspeed- The speed shown on the aircraft airspeedindicator. This is the speed used in pilot/controller communications under the general term "airspeed." True Airspeed- The airspeedof an aircraft relative to undisturbedair. Used primarily in flight planning and en route portion of flight. Whenused in pilot/controller communications,it is referred to as "true airspeed" and not shortened to"airspeed."
Altitude Theheight of a level, point, or object measured in feet Above Ground Level (AGL)or from Mean Sea Level(MSL.) AGL Altitude- Altitude expressed in feet measured above ground level. MSLAltitude- Altitude expressed in feet measured from mean sea level. Indicated Altitude- The altitude as shown by an altimeter.On a pressure or barometric altimeterit is altitude as shown uncorrected for instrument error and uncompensated forvariation from standard atmospheric conditions.
Anti-icing Aprecautionary procedure that provides protection against the formation of frostand/or ice and the accumulationof slush and/or snow on treated surfaces of an aircraft for a period of timeduring active frost, frozen precipitation,and freezing precipitation.
Theapplication of a freezing point depressant to a surface either followingdeicing or in anticipation of subsequentwinter precipitation is intended to protect the critical surfaces from iceadherence for a limited period of
time.The fluid is capable of absorbing freezing or frozen precipitation until thefluid freezing point coincides with the
ambienttemperature. Once this fluid freezing point has been reached, the fluid is nolonger capable of protecting the
aircraftfrom ground icing conditions.
Anti-icing Fluid 1. type I fluid;
2.mixture of water and type I fluid;
3.type II fluid or type IV fluid;
4.mixture of water and type II or type IV fluid.
NOTE:Anti-icing fluid is normally applied unheated on clean aircraft surfaces, butmay be applied heated.
Approach ClearanceAuthorization by ATC for a pilot to conduct an instrument approach. Thetype of instrument
approachfor which a clearance and other pertinent information is provided in theapproach clearance when required.
Approach Speed Therecommended speed contained in aircraft manuals used by pilots when making anapproach to
landing.This speed will vary for different segments of an approach as well as foraircraft weight and configuration.
ApronThatpart of an aerodrome, other than the maneuvering area, intended to accommodatethe loading and
unloadingof passengers and cargo, the refueling, servicing, maintenance and parking ofaircraft, and any movement
ofaircraft, vehicles and pedestrians necessary for such purposes.
Automated Surface Observation System (ASOS) / Automated WeatherObservation System (AWOS)A suite of
sensorswhich measure, collect, and disseminate weather data to help meteorologists,pilots, and flight dispatchers
prepareand monitor weather forecasts, plan flight routes, and provide necessary informationfor correct takeoffs and
landings.The basic difference between these two automated weather systems is that theASOS is comprised of a
standardsuite of weather sensors and is a product of a National Weather Service (NWS),Department of Defense
(DoD),and Federal Aviation Administration (FAA) joint venture. The AWOS is a suite ofweather sensors of many
differentconfigurations that are procured by the FAA or purchased by individuals,groups, airports, etc.
Automatic Terminal Information Service (ATIS)The continuous broadcast of recorded noncontrolinformation in
selectedterminal areas. Its purpose is to improve controller effectiveness and torelieve frequency congestion by
automatingthe repetitive transmission of essential but routine information; e.g., "Los Angeles informationAlfa. One
threezero zero Coordinated Universal Time. Weather, measured ceiling two thousandovercast, visibility three, haze,
smoke,temperature seven one, dew point five seven, wind two five zero at five,altimeter two niner niner six. I-L-S
RunwayTwo Five Left approach in use, Runway Two Five Right closed, advise you haveAlfa."
Aviation Weather Service Program Aviation weather service provided by theNational Weather Service (NWS) and
theFederal Aviation Administration (FAA) that collects and disseminates pertinentweather information for pilots,
aircraftoperators, and ATC. Available aviation weather reports and forecasts aredisplayed at NWS offices and FAA
FlightService Stations (FSS).
Below Minimums Weatherconditions below the minimums prescribed by regulation for the particularaction involved
(e.g.,landing minimums, takeoff minimums).
Braking Action Areport of conditions on the airport movement area providing a pilot with adegree/quality of braking
thatmight be expected. Braking action is reported in terms of good, fair, poor, ornil.
Braking Action Advisories When tower controllers have received runway braking action reports whichinclude the
terms"poor" or "nil," or whenever weather conditions areconducive to deteriorating or rapidly changing runway
brakingconditions, the tower will include on the ATIS broadcast the statement,"BRAKING ACTION ADVISORIES ARE
INEFFECT." During the time Braking Action Advisories are in effect, ATC willissue the latest braking action report for
therunway in use to each arriving and departing aircraft. Pilots should beprepared for deteriorating braking conditions
andshould request current runway condition information if not volunteered bycontrollers. Pilots should also be
preparedto provide a descriptive runway condition report to controllers after landing.
Carburetor Ice Iceformed in the carburetor due to the effects of lowered temperature by decreasedair pressure and
fuelvaporization in the presence of significant water vapor (high humidity). Notethat carburetor ice rarely occurs in a
lowhumidity environment, e.g., winter months in the northern part of the country.
Ceiling Theheights above the earth's surface of the lowest layer of clouds or obscuringphenomena that is reported as
"broken,""overcast," or "obscuration," and not classified as"thin" or "partial."
Celsius Atemperature scale where 0 is the freezing point of water and 100 is the boilingpoint of water. To convert
Celsiusto Fahrenheit: F = (9/5)*C + 32.
Center Weather Advisory (CWA) An unscheduled weather advisory issued byCenter Weather Service Unit
meteorologistsfor ATC use to alert pilots of existing or anticipated adverse weather conditionswithin the next 2 hours.
ACWA may modify or redefine a SIGMET.
Central Deicing Facility (CDF)A Transport Canada approved facility at anairport for the purpose of conducting
deicingand anti-icing operations.
ChartsAmap used in air navigation containing all or part of the following: topographicfeatures, hazards and
obstructions,navigation aids, navigation routes, designated airspace, and airports. Forspecifics on some commonly
usedaeronautical charts see: Sectional Aeronautical Charts, VFR Terminal AreaCharts, World Aeronautical Charts,
EnRoute Low Altitude Charts, En Route High Altitude Charts, Instrument ApproachProcedures, Instrument Departure
Procedures,and Standard Terminal Arrival Charts.
Check Anexamination of an item against a relevant standard by a trained and qualifiedperson.
Clean Aircraft Concept When conditions exist during ground operations that are conducive toaircraft icing, no person
shallconduct or attempt to conduct a take-off in an aircraft that has frost, ice orsnow adhering to any of its critical
surfaces.
Clear (or Glaze) IceClear ice is also called glaze ice. This ice type appears lumpy andtranslucent or clear and
smooth.It results from supercooled liquid water droplets striking the surface but notfreezing immediately upon contact.
Clearice tends to form horns or other complex shapes which can significantly disruptthe airflow.
Climbout Thatportion of flight operation between takeoff and the initial cruising altitude.
CloudAcloud is a visible accumulation of minute water droplets and/or ice particlesin the atmosphere above the
Earth'ssurface. Cloud differs from ground fog, fog, or ice fog only in that the latterare, by definition, in contact with the
Earth'ssurface.
Collision-CoalescenceThe theory of large cloud droplet formation in which smaller dropletscontinue to collide and
jointogether until a significantly larger droplet is formed.
Cold-soak Effect: The wings of aircraft are said to be “cold-soaked” when they contain verycold fuel as a result of
havingjust landed after a flight at high altitude or from having been re-fuelled withvery cold fuel. Whenever
precipitationfalls on a cold-soaked aircraft when on the ground, clear icing may occur. Evenin ambient temperatures
between-2°C and +15°C, ice or frost can form in the presence of visible moisture orhigh humidity if the aircraft
structureremains at 0°C or below. Clear ice is very difficult to be detected visuallyand may break loose during or after
takeoff.The following factors contribute to cold-soaking: temperature and quantity offuel in fuel cells, type and location
offuel cells, length of time at high altitude flights, temperature of re-fuelledfuel and time since re-fuelling.
Cold Soaking Icecan form even when the outside air temperature (OAT) is well above 0°C (32°F).An aircraft
equippedwith wing fuel tanks may have fuel that is at a sufficiently low temperaturesuch that it lowers the wing skin
temperatureto below the freezing point of water. If an aircraft has been at a highaltitude, where cold temperature
prevails,for a period of time, the aircrafts’ major structural components such as thewing, tail and fuselage will assume
thelower temperature, which will often be below the freezing point. Thisphenomenon is known as cold soaking. While
onthe ground, the cold soaked aircraft will cause ice to form when liquid water,either as condensation from the
atmosphereor as rain, comes in contact with critical surfaces.
Contaminated Runway A runway is considered contaminated whenever standing water, ice, snow,slush, frost in any
form,heavy rubber, or other substances are present. A runway is contaminated withrespect to rubber deposits or other
friction-degradingsubstances when the average friction value for any 500-foot segment of therunway within the ALD
failsbelow the recommended minimum friction level and the average friction value inthe adjacent 500-foot segments
fallsbelow the maintenance planning friction level.
Contamination Anyfrost, ice, slush or snow that adheres to the critical surfaces of an aircraft.
Contamination Check Check of aircraft surfaces for contamination to establish the need forde-icing.
Convective SIGMETA weather advisory concerning convective weather significant to the safetyof all aircraft.
ConvectiveSIGMETs are issued for tornadoes, lines of thunderstorms, embeddedthunderstorms of any intensity level,
areasof thunderstorms greater than or equal to VIP level 4 with an area coverage of4/10 (40%) or more, and hail 3/4
inchor greater.
Coordinated Universal Time (UTC)Formerly Greenwich Mean Time, also known as Zor ZULU time, UTC is the
internationaltime standard.
Critical Surfaces The wings, control surfaces, rotors, propellers, horizontal stabilizers,vertical stabilizers or any other
stabilizingsurface on an aircraft and, in the case of an aircraft that has rear-mountedengines, includes the upper
surfaceof its fuselage.
Critical Surface Inspection: A critical surface inspection is a pre-flight external inspection ofcritical surfaces
conductedby a qualified person as specified in CAR Part VI, subsection 602.11(5), todetermine if they are
contaminatedby frost, ice, snow or slush. This inspection is mandatory whenever groundicing conditions exist and, if
theaircraft is deiced / anti-iced with fluid, must take place immediately afterthe final, application of fluid or where an
approvedalternative method of deicing is used, upon completion of this process. Afterthe inspection, a report
completedby a qualified individual must be submitted to the pilot-in-command.
Critical Surface Inspection Report: This report must be made to thepilot-in-command and, if applicable, state the
timeat which the last full application of deicing or anti-icing fluid began, thetype of fluid used, the ratio of the fluid
mixture.Should the standard documented method not be used, the sequence in which thecritical surfaces were deiced
oranti-iced must be stated. In addition, the report must confirm that allcritical surfaces are free of contamination.
Cumuliform or Cumulous CloudsThe theory of large cloud droplet formation in which smaller dropletscontinue to
collideand join together until a significantly larger droplet is formed.
Defrosting Theforms of ice protection that remove existing accreted ice from aircraftsurfaces, such as pneumatic
boots.Compare to anti-icing.
Deicing Deicingis a procedure by which frost, ice, slush or snow is removed from an aircraftto render it free of
contamination.
Deicingis a general term for the removal of ice, snow, slush or frost from an aircraft’scritical surfaces, by
mechanicalmeans, by the use of heat, or by the use of a heated fluid or a combinationthereof. When frost, snow or ice
isadhering to a surface, the surface must be heated and fluid pressure used toremove the contaminant.
Deicing Fluid a)heated water;
b)type I fluid;
c)mixture of water and type I fluid;
d)type II or type IV fluid;
e)mixture of water and type II or type IV fluid.
NOTE:De-icing fluid is normally applied heated in order to assure maximumefficiency.
Deicing Operator The organization providing de/anti-icing related services to air operatorsat a given location. The
DeicingOperator may be a qualified third party, another airline, or the Air Operator.The Deicing Operator must provide
aservice in accordance with the air operator’s approved ground icing program,where such a program exists.
Deposition Aprocess where water vapor turns directly to ice upon contact with a surface,and does not pass through a
liquidstate.
Deviations Adeparture from a current clearance, such as an off course maneuver to avoidweather or turbulence.
Wherespecifically authorized in the FARs and requestedby the pilot, ATC may permit pilots to deviate from certain
regulations.
Dew Point Thetemperature at which water vapor will begin to condense. The relative humidityat the dew point is 100
percent.
Direct User Access Terminal (DUAT) A computer terminal where pilots can directlyaccess meteorologic and
aeronauticalinformation, plus file a flight plan without the assistance of an FSS.
EmergencyAdistress or an urgency condition.
En Route High Altitude ChartsProvide aeronautical information for en route instrument navigation (IFR)in the high
altitudestratum. Information includes the portrayal of jet routes, identification andfrequencies of radio aids, selected
airports,distances, time zones, special use airspace, and related information.
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