De Icing and Anti Icing of Aircraft on the Ground Operations

De-icing is an essential part in ground operations for a flight in specific seasons and countries. iJET team is 24/7 to assist in your ground handling, ground operations and flight plan in any weather condition.

During many years of aviation operations, the aviation industry has developed the practice of de-icing/anti-icing an airplane before takeoff. It was also possible to de-ice and anti-ice airplanes on the ground using various techniques. The most common technique involves the use of FPD (freezing point depressant) fluids to aid in the ground de-icing/anti-icing process and to prevent frost, snow, or ice from forming on the aircraft. All aircraft operators, aviation engineers and de-icing aircraft service providers should incorporate the Anti Icing Code Procedure into their operational procedures, as described in the AEA (Association of European Airlines) Guidelines.

The purpose of aircraft de-icing and anti-icing procedures is threefold:

• To remove any frozen or semifrozen moisture from critical external surfaces of an aircraft before flight
• To protect those surfaces from the effects of such contaminants between treatment and airborne transmission
• To prevent subsequent contamination of external surfaces, any frozen or semi-frozen moisture should be removed from engine intakes and fan blades before takeoff

The Factors That Affect De/Anti-Icing

An aeroplane’s surface roughness can be caused by a multitude of variables, such as ice accumulation and snow accumulation. Some of these variables are:

• Temperature of the environment
• Airplane skin temperature
• Water content and precipitation rate
• Temperature of deicing/antiicing fluids
• Fluid/water ratio of the de-icing/anti-icing fluid
• Humidity relative
• The speed and direction of the wind

In addition, they can affect the anti-icing and de-icing capabilities of anti-icing fluids. This means that it is impossible to determine a well-defined period of time during which an anti-icing fluid provides protection.

De-Icing/Anti-Icing Fluids for Aeroplanes

There are four types of deicing/anti-icing fluids: Type I, Type II, Type III, and Type IV. A fluid of type I has a relatively low viscosity, which varies primarily with temperature. A fluid with type II, III or IV contains a thickener system and, therefore, has a higher viscosity subject to herar force, fluid/water ratio, and temperature changes. The anti-icing properties of Type II, III, and IV fluids are better than those of Type I fluids. Operators, fluid manufacturers, and airplane manufacturers must all establish use criteria for de-icing/anti-icing fluids, and they must also meet ISO (International Standards Organization) specifications.

Icing Types in Aviation

The three major types of ice accretion are as follows, in order of their hazard to flying:

1. Clear Ice

A clear sheet of ice forms when a drop that is still liquid after initial impact flows out over the plane’s surface and gradually freezes. It occurs when drops are large, as in rain or cumuliform clouds. Clear ice is heavy, hard, and durable. It is especially difficult to remove it using deicing equipment.

2. Rime Ice

The formation of rime ice occurs when drops are small, such as those found in stratified clouds or light drizzle. Before the drop has a chance to spread over the aircraft surface, the liquid portion remaining after initial impact freezes rapidly. Because of its irregular shape and rough surface, it reduces the aerodynamic efficiency of airfoils, resulting in less lift and more drag. It is easier to remove rime ice than clear ice because it is brittle.

3. Mixed Icing

A mixed ice form when ice particles or liquid drops are mixed together or when the size of the drops vary. In some cases, it can form very quickly. On leading edges, ice particles become encrusted in clear ice, forming a mushroom-shaped accumulation.

What are the Differences Between De-Icing and Anti-Icing Fluids?

It is essential for Type I to be effective as an aircraft deicing fluid. Type I fluids are often further diluted for application due to aerodynamic performance and/or freezing points.

Type II and IV fluids should be used undiluted for maximum anti-icing protection. Fluids of types II and IV can also be used in diluted conditions when temperatures are high and precipitation is low for de-icing/anti-icing applications. Fluids classified as Type III can be diluted fluids classified as Type II or IV, as long as they meet aerodynamic performance requirements.

As a result of their high viscosity, Type II, III, and IV fluids coat the wings much thicker than Type I fluids. Airflow during take-off exposes these fluids to a shear force that causes them to lose viscosity, allowing them to flow off the critical portions before rotation.

Aviation Risk Management

Prior to flight planning when weather conditions are conducive to ice accretion or are likely to be so, the following precautions should be taken:

• All airframe critical surfaces should be examined thoroughly to determine if any contamination exists; the surface temperature of the skin is just as important as the outside air temperature (OAT).
• De-Icing Fluids and/or Anti-Icing Fluids should be applied correctly, along with the De/Anti-Icing Code, in order to avoid any miscommunication.
• Holdover Time (HOT) should be identified and monitored by the flight crew so that takeoff cannot be attempted if the time is not met. The applicable Holdover Time may change if prevailing conditions change.

Recommendations for De-Icing or Anti-Icing

• Including the latest Holdover Time (HOT) Tables should be included in every AOM or POH (Pilot’s Operating Handbook) for flight crews.
• Providers of ground deicing/anti-icing should follow effective Quality Control procedures to ensure proper procedures are followed and that their procedures are followed. Moreover, aircraft operators should ensure that ground de/anti-icing procedures are included in their Quality Assurance procedures.
• De/Anti-Icing Codes should be used at all times for communicating and documenting the details of aircraft treatment. These codes are important to avoid any miscommunications.
• A recommendation in EASA SIN 2008-29 is to follow the instructions for de/anti-icing engine intakes.

Check Procedures for De-Icing and Anti-Icing

1. Checklist Before De-Icing/Anti-Icing Fluids are Applied

Ground crews or flight crews usually perform the pre-flight walk-around or pre-flight check as the first step. In accordance with an approved operator plan, critical surfaces, fuselage, and landing gear must be checked for ice, snow, slush, or frost. De-Icing and Anti-Icing operation must be performed on an airplane if it is discovered to be iced, snowed, slushy or frosty.

2. Checks After De-Icing and Anti-Icing Fluids are Applied

According to the approved operator plan and procedures, a qualified person checks compliance with the Clean Aircraft Concept immediately following the application of de-icing/anti-icing fluids.

Pre-takeoff checks are performed by the pilot-in-command to ensure that the aeroplane’s critical surfaces are clear of slush, snow, ice, or frost just before takeoff. Visually checking the wings or other surfaces of the aeroplane should be carried out as close to take-off as possible.

3. Checklists for Special Situations

In rainy or high-humidity conditions and for certain types of aircraft, a check for clear ice may be required. Clear ice is often caused by cold-soaked fuel in the wing tanks. When the wings are wet or in poor lighting conditions, this type of ice is very difficult to detect. To detect this type of icing, special check procedures must be included in the approved operator program.

iJET Ground Operation Service for De-Icing and Anti-Icing

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