De-icing and Anti-icing

Types of Fluids

• Type I
• minimum 80% glycol
• relatively low viscosity
• very limited anti-icing protection against re-freezing but does not protect against further accumulation
• Type II
• minimum 50% glycol
• high viscosity
• effective anti-icing
• for aircraft with Vr > 100 kts; shears off on take-off
• potential to lose effectiveness if improperly applied
• Type III
• properties between Type I and Type II
• for aircraft with Vr < 100 kts
• Type IV
• same fluid specifications as Type II, but longer holdover times
• dyed green to aid consistent application

Holdover Time

• the estimated time that the application of de-icing/anti-icing fluid will prevent the formation of frost, ice, or the accumulation of snow on treated surfaces of an aircraft
• begins when the final application of de-icing/anti-icing fluid commences, and expires when the fluid loses its effectiveness

Frozen Contaminants

Reference AIM AIR 2.12 Flight Operations in Winter

Factors affecting contamination and hold-over time:

• ambient temperature
• aircraft surface temperature
• de-icing / anti-icing fluid type, temperature and concentration
• relative humidity
• wind speed and direction

Cold-Soaking Phenomenon

• fuel temperature affects wing surface temperature
• cold-soaking at altitude means fuel in tanks may be much colder than ambient temperature after landing
• clear ice or frost may form on some aircraft on wing areas above fuel tanks, especially in conditions of high relative humidity

Clean Aircraft Concept

Reference AIM AIR 2.12 Flight Operations in Winter

Wing contamination is serious business.  Ice with the thickness and texture of sandpaper on the surfaces of an aircraft could decrease lift by 30% and increase drag by 40%.  As ice accumulates on a wing, the stalling speed increases and the angle at which the wing will stall decreases.

Clean Aircraft Concept:

• refers to take-off being prohibited when frost, snow or ice is adhering to any critical surface of the aircraft

Critical Surfaces refers to:

• wings
• control surfaces
• propellers
• horizontal stabilizers
• vertical stabilizers
• upper surface of fuselage in the case of aircraft with rear-mounted engines

CAR 602.11 Aircraft Icing

• no person shall attempt to conduct a take-off in an aircraft that has frost, ice, or snow adhering to any of its critical surfaces
• exception: frost on underside of wing caused by cold-soaked fuel (refer to manufacturer's instructions)
• take-off in icing conditions
• Part 705: PIC (or person designated by operator) must inspect immediately prior to take-off (or operator has established aircraft inspection program)
• Part VII other than subpart 5: operator has established aircraft inspection program  
• report observed ice to PIC (or designated person) so they can inspect
• PIC must inform other crew members of intention to de-ice/anti-ice