All About Aircraft De/Anti-Icing
Find out why aircraft de/anti-icing is so fundamental, all about the equipment, processes and procedures involved, and the services Miles Aviation Consulting Ltd’s team of de/anti-icing and ground operations specialists can provide for your business.
What is aircraft de/anti-icing?
Let’s start with the basics
Aircraft deicing and anti-icing are the processes in which frost, snow, slush, or ice (all known as ‘frozen contamination’) are removed from an aircraft to ensure components and surfaces are kept clear. These forms of frozen contamination can be particularly common during winter operations, and they pose a real risk to flight safety.
For example, on a “clean” wing, airflow flows freely over the smooth surface and produces lift. A “contaminated” wing interrupts airflow, reducing and inhibiting aircraft lift capability. Frost or ice with a thickness of just 3 to 5 mm can reduce lift by 30%, especially in the initial take-off phase of flight. With this in mind, failure to remove frozen contaminant prior to flight creates a significant safety risk which, if ignored, could result in fatal consequences.
As such, procedures to prevent frozen contamination are heavily regulated and important to maintaining safety in aviation. Airlines and operators are required to follow strict industry operational standards for aircraft deicing and anti-icing treatments are determined by SAE International in documents AS6285 and AS6286.
Generally, this is why de/anti-icing is considered one of the more skilled ramp-handling activities due to its particular safety-critical nature.
Who is responsible for aircraft deicing?
Aircraft de/anti-icing is considered a ramp-handling activity and as such is generally undertaken by Ground Handling Service Providers (GHSPs), Fixed-Base Operators (FBOs), self-handling airlines, or airport operators. Any organisation offering the service is known as a ‘Deicing Service Provider (DISP).’
Annual training and refresher courses are required to undertake de/anti-icing and to remain compliant to industry standards. These should include management, instructors, and of course front-line spraying staff.
What does a typical de/anti-icing process look like?
Generally, deicing and anti-icing treatments take place on aircraft parking stands, however, many airfields also have specifically-designed remote deicing pads. The most common method of removing frozen contamination is to apply heated and unheated de/anti-icing fluids, sprayed on by a deicing vehicle or ‘rig’. Mechanical methods, such as using soft brushes or warm air, are also acceptable although not commonplace.
Deicing fluid is used to remove contamination, whilst anti-icing fluid is applied to prevent surfaces from freezing or re-freezing. The process can be done either in one step, whereby a single coat of heated anti-icing fluid is used to both remove contamination and prevent refreezing or in two steps. This requires contamination to be removed via the application of heated deicing fluid, followed by a repeat application of a (normally) cold anti-icing fluid as well as post de/anti-icing checks to ensure aircraft are, in fact, free from frozen contamination.
When should de/anti-icing take place?
In most cases, contamination is removed prior to flight. In the de/anti-icing world, ‘holdover time’ (HOT) is used to ensure aircraft surfaces remain free from contamination at all times prior to departure. Holdover time is the amount of time in which anti-icing fluid is active and providing sufficient protection. Prior to departure, an ‘anti-icing code’ must be passed to flight crew to allow them to calculate the HOT, and this confirms to crew that the aircraft has been adequately anti-iced.
Upon expiry of HOT prior to departure, de/anti-icing must be repeated. These procedures safeguard aircraft in winter operations and ensure the presence of ice is eradicated and cannot affect aircraft operations. This is another benefit to remote deicing stands which are typically located closer to runways, allowing the anti-icing process to occur closer to departure times and, thus, reducing the likelihood of HOT expiry.
Deep Dive: De/Anti-Icing Fluids
What are the different types of de/anti-icing fluid?
There are four main types of deicing and anti-icing fluid: Type I through to Type IV. They each have different viscosities and properties which make them best suited for different circumstances, or for aircraft with different operating capabilities. They are also, typically, dyed different colours to allow for differentiation.
TYPE I
This is a Newtonian fluid (meaning its viscosity remains constant), and is generally used only for aircraft deicing, to remove initial contamination from aircraft surfaces. It is not effective as an anti-icing fluid as it has a negligible holdover time (HOT), meaning frozen contaminants start to re-form too quickly after treatment thus making it operationally unviable for prevention purposes.
TYPES II, III & IV
These are non-Newtonian (meaning its viscosity can alter) viscous fluids used for anti-icing purposes. They have a longer HOT making them viable for ice prevention and anti-icing needs. These types differ mostly based on the operational capabilities of the aircraft they are being applied to - Type II for example is suited to aircraft with rotation speeds exceeding 100 knots, and Type III for those aircraft which rotate below this speed. Type IV has similar aircraft capability to Type II, however, it is differentiated by its longer HOT - making it more suitable for busier aerodromes or those with limited remote de/anti-icing facilities.
Required for use in winter aircraft operations, de/anti-icing fluids have a freeze point as low as, or below, -37 degrees Celsius. Deicing fluid is most effective when applied hot, whereas anti-icing fluids are more effective when applied cold. Types II and IV are the most commonly used types in the industry.
Fluid testing and industry standards relating to de/anti-icing fluid
These fluids must be tested regularly, both at delivery, as well as whilst in-service, for their viscosity, refractive index (concentration), pH levels, and for any visible contamination. Deicing and anti-icing processes play vital roles in the safety of any aircraft, therefore checks and measures must be in place. Fluids falling below manufacturer limits may not perform as expected; HOT must be correctly calculated.
This is a highly controlled part of the industry with strict training requirements and industry standards for de/anti-icing procedures, as well as fluids, set out by SAE International. Industry standards for the manufacturing of de/anti-icing fluids are determined by SAE International in documents AMS1424/1428.
Conclusion
Deicing and anti-icing are fundamental to safe winter operations
To summarise, aircraft de/anti-icing treatments are crucial to ensuring safe winter operations. Past accidents and incidents have shown the dangers of ice, snow, slush, and frozen contamination as a whole - and, as such, these procedures and processes are heavily regulated. The use of deicing and anti-icing fluids to both remove and prevent frozen contamination, as well as safeguards to confirm aircraft are always free from contamination, ensure that colder weather is not a factor which affects safe and efficient aircraft operations.
SAE International set the standards for deicing and anti-icing, which are adopted by National Aviation Authority (NAAs) who, in turn, regulate Deicing Service Providers (DISPs) and ensure regular training is undertaken whilst operators remain compliant. Deicing and anti-icing are skilled processes performed by qualified ramp personnel, and as stated, are fundamental to safe winter operations.
Would you like more information about aircraft de/anti-icing, and the services we at Miles Aviation Consulting can provide?
We are specialists in de/anti-icing, ground operations and ground handling - and can provide your organisation with high-quality training courses, documentation and ground operations manuals, audit services, and consulting/project support. If you have a bespoke requirement and think we can help, don’t hesitate to get in touch with our team.
Did you know…
We provide high quality training courses in de/anti-icing processes, including management training, instructor training, and front-line operator training. See our course pages below to find out more about our specialist de/anti-icing training offering:
