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The following definitions are presented in the context of this Training Manual only. These definitions are not necessarily intended to apply universally to other documents.


Aircraft Deicing Facility

Means a facility where:

  • Frost, snow or ice are removed (deicing) from an aircraft in order to provide clean surfaces; and/or
  • Critical surfaces of the aircraft receive protection (anti-icing) against the formation of frost or ice, or the accumulation of snow or slush for a limited period of time.
  • Fluid Storage, Equipment Maintenance, Environmental Mitigation, Control Centre.

Aircraft Deicing Pad

A designated area on an aircraft deicing facility intended to be used for parking an aircraft to conduct deicing or anti-icing activities, consisting of an inner area for the parking of an aircraft to receive deicing/anti-icing deicing vehicles (safe zone). The outer area provides the vehicle lane width necessary for deicing vehicles to safely perform during the deicing operation.

Air Operator

The holder of an air operator certificate.

Air operator certificate

A certificate issued under the CARs that authorizes the holder of the certificate to operate a commercial air service.


Anti-icing is a precautionary procedure that provides protection against the formation of frost and/or ice and the accumulation of slush and/or snow on treated surfaces of an aircraft for a period of time during active frost, frozen precipitation, and freezing precipitation.

The application of a freezing point depressant to a surface either following deicing or in anticipation of subsequent winter precipitation is intended to protect the critical surfaces from ice adherence for a limited period of time. The fluid is capable of absorbing freezing or frozen precipitation until the fluid freezing point coincides with the ambient temperature. Once this fluid freezing point has been reached, the fluid is no longer capable of protecting the aircraft from ground icing conditions.


Means that part of an aerodrome, other than the manoeuvering area, intended to accommodate the loading and unloading of passengers and cargo, the refueling, servicing, maintenance and parking of aircraft, and any movement of aircraft, vehicles and pedestrians necessary for such purposes.


Central Deicing Facility (CDF)

A Transport Canada approved facility at an airport for the purpose of conducting deicing and anti-icing operations.

Clean Aircraft Concept

When conditions exist during ground operations that are conducive to aircraft icing, no person shall conduct or attempt to conduct a take-off in an aircraft that has frost, ice or snow adhering to any of its critical surfaces.

Cold Soaking (revisit title)

Ice can form even when the outside air temperature (OAT) is well above 0°C (32°F). An aircraft equipped with wing fuel tanks may have fuel that is at a sufficiently low temperature such that it lowers the wing skin temperature to below the freezing point of water. If an aircraft has been at a high altitude, where cold temperature prevails, for a period of time, the aircrafts' major structural components such as the wing, tail and fuselage will assume the lower temperature, which will often be below the freezing point. This phenomenon is known as cold soaking. While on the ground, the cold soaked aircraft will cause ice to form when liquid water, either as condensation from the atmosphere or as rain, comes in contact with critical surfaces.


Means any frost, ice, slush or snow that adheres to the critical surfaces of an aircraft.

Critical Surfaces

"Critical surfaces" of an aircraft means the wings, control surfaces, rotors, propellers, horizontal stabilizers, vertical stabilizers or any other stabilizing surface on an aircraft and, in the case of an aircraft that has rear-mounted engines, includes the upper surface of its fuselage.

Critical Surface Inspection

A critical surface inspection is a pre-flight external inspection of critical surfaces conducted by a qualified person as specified in CAR Part VI, subsection 602.11(5), to determine if they are contaminated by frost, ice, snow or slush. This inspection is mandatory whenever ground icing conditions exist and, if the aircraft is deiced/anti-iced with fluid, must take place immediately after the final, application of fluid or where an approved alternative method of deicing is used, upon completion of this process. After the inspection, a report completed by a qualified individual must be submitted to the pilot-in-command.

Critical Surface Inspection Report

This report must be made to the pilot-in-command and, if applicable, state the time at which the last full application of deicing or anti-icing fluid began, the type of fluid used, the ratio of the fluid mixture. Should the standard documented method not be used, the sequence in which the critical surfaces were de-iced or anti-iced must be stated. In addition, the report must confirm that all critical surfaces are free of contamination.



The removal of frost from an aircraft's critical surfaces and their subsequent protection.


Deicing is a procedure by which frost, ice, slush or snow is removed from an aircraft to render them free of contamination.

Deicing is a general term for the removal of ice, snow, slush or frost from an aircraft's critical surfaces, by mechanical means, by the use of heat, or by the use of a heated fluid or a combination thereof. When frost, snow or ice is adhering to a surface, the surface must be heated and fluid pressure used to remove the contaminant.

Deicing Operator

The organization providing de/anti-icing related services to air operators at a given location. The Deicing Operator may be a qualified third party, another airline, or the Air Operator. The Deicing Operator must provide a service in accordance with the air operator's approved ground icing program, where such a program exists.


Fluid Deicing/Anti-icing Methods

These are methods of using acceptable fluids for the removal of frozen contamination from an aircraft's critical surfaces and then for preventing the formation and/or accumulation of contamination on an aircraft for a limited period of time. The details are contained in The Society of Automotive Engineers (SAE) document ARP4737, entitled: "Aircraft deicing/anti-icing Methods".

Fluid Dryout

Fluid residue that may remain in aerodynamically quiet areas throughout a flight.

Fluid Endurance Time

Endurance times of anti-icing fluids are measured in laboratory and field tests under specific contamination and temperature conditions using flat test plates in accordance with the SAE documents AMS 1424 &AMS 1428. These tests are considered to replicate the failure of fluid during aircraft operations.

Fluid Failure

Typically, in the case of snow, a layer of snow eventually accumulates on the surface of the fluid and is no longer being absorbed by the fluid. The appearance of a build up becomes evident. There is a distinct loss of shine or gloss on the surface of the fluid.

Forced Air Deicing Method

This is a method of deicing using a concentrated flow of air under pressure to remove contamination from an aircraft, which may be used in conjunction with deicing fluids.

Freezing Point Depressant (FPD) Fluids

The generic term applied to all types of deicing fluids.


Ground Ice Detection System (GIDS)

A ground ice detection system is designed to detect frozen contaminants on an aircraft. These systems can be either ground based or aircraft based systems. GIDS may be either a spot sensor or an area sensor system. If approved by Transport Canada, such a system may be used as an alternative to other inspection methods.

Ground Icing Conditions

With due regard to aircraft skin temperature and weather conditions, ground icing conditions exist when frost, ice, or snow is adhering or may adhere to the critical surfaces of an aircraft.

Ground Icing Conditions also exist when active frost, frozen or freezing precipitation is reported or observed.

Ground Icing Operations Program

A Ground Icing Operations Program consists of a set of procedures, guidelines, and processes, documented in manuals, which ensure that an Air Operator's aircraft does not depart with frost, ice, snow or slush adhering to critical surfaces. This program is mandatory for CAR 705 operations and must be approved by Transport Canada.



Hail is precipitation consisting of small balls or pieces of ice with a diameter ranging from 5 mm to greater than 50 mm falling either separately or agglomerated.


A uniform, thin white deposit of fine crystalline texture that forms on exposed surfaces during calm, cloudless nights when the temperature falls below freezing and the humidity of the air at the surface is close to the saturation point. It is not associated with precipitation. The deposit is thin enough that the underlying surface features, such as paint lines, markings or lettering can be distinguished.

Holdover Time (HOT)

Holdover time is the estimated time that an application of anti-icing fluid is effective in preventing frost, ice, slush or snow from adhering to treated surfaces. Holdover time is calculated as the beginning of the final application of the anti-icing fluid, and as expiring when the fluid is no longer effective. The fluid is no longer effective when its ability to absorb more precipitation has been exceeded. This can produce a visible surface build-up of contamination. (as measured in endurance time tests and published in "Holdover Time Guidelines").

Holdover time is the estimated time that the fluid prevents reformation of contamination on critical surfaces. Holdover time commences at the beginning of the final fluid application.

Holdover Time Guidelines

Holdover Time Tables are referred to as Holdover Time Guidelines because this term more appropriately represents their function in providing guidance to flight crew and the need for the flight crew to use judgment in their interpretation.

Fluid holdover times, as published by, Commercial and Business Aviation, Transport Canada are found published in "Holdover Time Guidelines" as tables and may be used either as guidelines or decision-making criteria in assessing whether it is safe to take off. When holdover times are used as decision-making criteria, only the lowest time value in a cell shall be used. The procedures to be followed after the holdover time has expired must be clearly documented. The use of holdover time guidelines is mandatory if they are part of the Air Operator's approved ground icing program.



The solid form of water. Clear Ice is often difficult to detect visually on an aircraft's critical surfaces. It can be present in a transparent form, which may make the aircraft's critical surfaces appear to be wet.

Ice Pellets

These are a type of precipitation consisting of transparent or translucent pellets of ice, 5 mm or less in diameter. They may be spherical, irregular, or (rarely) conical in shape. Ice pellets usually bounce when hitting hard ground, and make a sound upon impact. Now internationally recognized, ice pellets include two fundamentally different types of precipitation, which are known in the United States as (a) sleet, and (b) small hail. Thus a two-part definition is given:

  • Sleet or grains of ice:  Generally transparent, globular, solid grains of ice which have formed from the freezing of raindrops or the refreezing of largely melted snowflakes when falling through a below-freezing layer of air near the earth's surface. Note that the term "sleet" in British terminology and in some parts of the U.S. refers to a mixture of rain and snow and therefore should not be used.
  • Small hail:  Generally translucent particles, consisting of snow pellets encased in a thin layer of ice. The ice layer may form either by the accretion of droplets upon the snow pellet, or by the melting and refreezing of the surface of the snow pellet. It is believed that the ice pellets are capable of penetrating the de/anti-icing fluid and have enough momentum to contact the aircraft's surface beneath the fluid. Additionally, the ice pellets are of significant mass and therefore local dilution of the fluid by the ice pellet would result in the very rapid failure of the fluid.

Infrared Heat Deicing Method

This is a method of deicing using infrared (IR) thermal energy.


Lowest Operational Use Temperature (LOUT)

For a given fluid is the higher of The lowest temperature at which the fluid meets the aerodynamic acceptance test for a given aircraft type, or the actual freezing point of the fluid plus a freezing point buffer of 7°C for type I or 10°C for type II III &IV.


Manoeuvring Area

Means that part of an aerodrome to be used for the take-off, landing and taxiing of aircraft, excluding aprons.



The pilot responsible for the operation and safety of an aircraft during flight time. (Flight time being: the time from the moment an aircraft first moves under its own power for the purpose of flight until the moment it comes to rest at the next point of landing).

Precipitation rate

The rate at which precipitation is either measure or judge to be falling. Winter precipitation is a key factor in estimating the Holdover Time for an anti-icing fluid. It is the indication of moisture content.

Pre-Take-off Contamination Inspection

A pre-take-off contamination inspection is an inspection conducted by a qualified person, immediately prior to take-off, to determine if an aircraft's critical surfaces are contaminated by frost, ice, slush or snow. This inspection is mandatory under some circumstances.

Pre-Take-off Contamination Inspection Report

This report must be made to the pilot-in-command and, when a documented inspection method has not been used, must describe how the inspection was conducted. The report must also confirm that all critical surfaces are free of contamination.


Representative Surface

Aircraft representative surfaces are those surfaces which can be readily and clearly observed by flight crew during day and night operations, and which are suitable for judging whether or not critical surfaces are contaminated. Examination of one or more representative aircraft surfaces may be used for the Pre-Take-off Contamination Inspection, if a tactile examination is not required. Transport Canada must approve the use of these aircraft specific surfaces.



A mixture of frozen and liquid water, which may include chemicals.

Snow Grains

These are a precipitation that comprises very small white and opaque grains of ice. These grains are fairly flat or elongated; their diameter is less than 1 mm. When they hit hard ground, they do not bounce or shatter.

Snow pellets

These are a kind of precipitation, which consists of white and opaque grains of ice. These grains are spherical or sometimes conical; their diameter is about 2-5 mm. Grains are brittle, easily crushed. They do bounce and break on hard ground.



Means a defined path on a land aerodrome established for the taxiing of aircraft and intended to provide a link between one part of the aerodrome and another.

Tactile Inspection

A tactile inspection requires that a person physically contact specific aircraft surfaces. Tactile inspections, under certain circumstances, may be the only way of confirming that the critical surfaces of an aircraft are not contaminated. For some aircraft, tactile inspections are mandatory, as part of the deicing/anti-icing inspection process, to ensure that the critical surfaces are free of frozen contaminants.