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It is officially the season where we begin to see many different forms of wintry precipitation. With the first snow not too long ago in the northern Ohio region, I have reflected on my previous airline employment deice training as a cross-trained agent. What do we use to deice, how do we use it, and why? Regardless of whether it's freezing rain, sleet, or snow, frozen contamination can stick to the control surfaces of an aircraft and can seriously degrade performance. A few severe effects of icing on an aircraft could result in: • Improper airflow over the wings resulting in a loss of lift
• Exceedance of design load limits
• Contaminated sensors resulting in faulty instrument readings
To ensure all aircraft are clear of frozen contamination before dispatching, regulations were put in place called the " Clean Aircraft Concept" according to 14 CFR 121.629. It is the Captions ultimate responsibility and final authority to ensure that the aircraft is clean and meets all requirements. Through the efficiency of airline station deice planning, carrier personnel are thoroughly equipped with the skills and technicalities to meet these requirements for annual deice operations.
What is used to deice an aircraft?Deicing fluids remove frost, ice, snow, or slush on aircraft surfaces. Anti-icing prevents the adherence of frozen contamination by lowering the freezing point of precipitation collecting on an aircraft. Most deicing and anti-icing fluids are chemical products, typically ethylene or propylene glycol, containing a freeze-point depressant. The two types of deice/anti-ice fluids primarily used during my regional training were type I and type IV. RELATED: Types of deice systems on aircraftType I deice fluidsType I is used primarily as a deicing fluid and is orange, reddish-orange, or pink color. The mixing ratio listed for type I is 55/45 concentration containing 55% type I and 45% water. This mixture is applied first to rid the aircraft's surface of any contaminates— ice, snow, frost, sleet, etc. It is heated to a nozzle head temperature of 140 degrees before application. Due to the mixture's concentration with water, its viscosity is low resulting in a low holdover time.
Type IV deice fluids Type IV is used only as an undiluted (no water content) anti-icing fluid and is green in color. This fluid is also unheated when applied. Before anti-ice can be applied the aircraft must be completely cleaned off from all contamination with Type I. For the deicing personnel, if it's snowing hard outside, this could be a continuous process of deicing/anti-ice treatment. Under no circumstances can Type IV anti-icing treatment be applied on a contaminated surface.
How to use aircraft deicing fluidsOnce the deice personnel gets the go-ahead from the captain, they begin the deicing application process. For the wings and horizontal tail surfaces, it is recommended to spray from the tip of the wing or horizontal stabilizer towards the root from the leading edge towards the trailing edge and from the highest point to the lowest. The deice personnel must pay extra attention not to spray Wi-Fi antennas, near engines, APU, pitot-static mass/tubes, air inlets, sensors, and landing gear and wheel well areas unless the brakes are cooled off.
Lastly, before applying type IV fluid, if necessary, for the Embraer EMB-145 aircraft only, a tactile test must be performed. That test is simply performed by physically touching the wings leading edge and the surface to ensure the area is free of ice, frost, and snow. You should physically be able to feel the seams and the rivets of the surface.
Why deicing an aircraft is important There are a ton more things that go into the deicing process such as fluid testing, documentation, proper communication with the flight crew, even the direction of the movement of the deice truck. All of these topics of discussion accumulate into pretty lengthy training classes. Nevertheless, the essence of what truly matters for all dedicated ground personnel is the safe arrival and departure of several aircraft and persons on board.