Why do I need to deice my airplane and what could happen if I skip deicing?
Airplane deicing is an important procedure that must be done during winter weather conditions to safeguard your aircraft’s performance. A buildup of ice, snow, frost, or other contaminants, especially on critical areas like the wings and horizontal and vertical stabilizers is dangerous.
If allowed to accumulate, these contaminants have detrimental impacts on all four forces of flight – drag, lift, thrust, and weight. The aircraft experiences increased drag, decreased lift, reduced available thrust and increased weight.
As critical airflow over the wings, horizontal stabilizers, and vertical stabilizers becomes disrupted by build-up, turbulence increases and your stall angle of attack decreases. If you skip deicing and attempt to take off with the contaminants still attached, the decreased stall angle of attack could result in a crash – see Air Florida Flight 90.
Another concern is that Ice buildup on control surfaces like ailerons, rudder and elevators can restrict their movement leading to a reduced or even complete loss of control.
A worst-case scenario possibility is that ice could build up and break off during flight, then get pulled into the engine(s) resulting in a surge, vibration, and loss of thrust.
When do I need to deice my airplane?
Although it may be tempting to think that deicing is only necessary during weather that is producing sleet, snow or ice, even seemingly benign frost may also be a cause for concern. Although frost does not change the wings’ aerodynamic shape in the same way as ice or snow, it does create a rough surface on the normally smooth wing. As air passes over the frost, it slows and separates earlier than normal causing decreased lift.
The FAA’s ground deicing program calls for every plane that takes off to be a clean aircraft with no contaminants coating it. If your aircraft does not meet the clean aircraft concept criteria, it is time to deice.
What parts of my airplane does the FAA recommend deicing?
The FAA takes deicing seriously and has put in place a very specific and detailed guide to international de/anti-icing procedures. The regulations standardize the handling and application of deicing compounds as well as the timeline and documentation that must be followed for each application.
The areas of the aircraft that the FAA recommends inspecting and deicing as appropriate include:
- Antennas and sensors
- Control surfaces and gaps
- Engine inlets and fan blades (front and back side of blades)
- Landing gear and landing gear door
- Pitot heads and static ports
- Vertical and horizontal tail surfaces (upper and lower horizontal surfaces)
- Wings (upper and lower)
- All other aerodynamic surfaces
What is used to deice airplanes?
When it comes time to deice your plane, most of the contamination – including ice, snow and frost – is removed using a deicing compound comprised of glycol and water. The glycol lowers the freezing point of the water. The exact formulation and ratio of glycol to water can be selected based on the weather conditions and desired duration of effectiveness.
Deicing fluid comes in multiple types with Type I – a less viscous, orange dyed fluid rated for use at temperatures down to 22°F – being the most common. Each fluid has a specified holdover time – the length of time the fluid will remain on the aircraft surfaces and prevent the formation or accumulation of frozen deposits on treated surfaces.
Some areas of your aircraft like the pitot heads, static ports, engine inlets, and fan blades must be de-iced, but cannot be subjected to the deicing fluid. In this case, you will need to resort to manual cleaning using a brush or hot air.
How do I deice my airplane?
To deice a commercial airplane, the deicer blend will be heated to approximately 130-180°F and sprayed onto your aircraft through a high-pressure hose. As the pilot, you will work with the ground crew to make a joint determination on which aircraft surfaces require deicing, which type of fluid to use, and whether manual deicing is required for select areas. It is important for the pilot and crew to know the no-spray areas of their aircraft and plan deicing accordingly. Consult your aircraft maintenance manual (AMM) for aircraft-specific details and guidance.
Commercial jets may be deiced either at the gate or – more frequently – at a designated deice pad. During the deicing procedure, two to four deicing vehicles will start at the front of the fuselage and work their way aft spraying on the deicing fluid. The rule of thumb is high to low and front to back for the most even, thorough, and effective application. It is important that the fluid be applied symmetrically so that both the left and right sides of the aircraft receive the same treatment. This helps to prevent uneven ice buildup which would even more adversely impact the aerodynamic stability of the plane.
That takes care of commercial aircraft, but what about general aviation pilots? A GA pilot does not have the luxury of a dedicated ground crew that the airline pilot enjoys, but the small GA aircraft is no less susceptible to the dangers of icing.
The best option to ensure a clean plane is to store it in a hangar if at all possible. If you need to brush your aircraft off, use a special soft-bristle brush that will not damage your plane. Hot water is also an option if you wipe it back off before it freezes. De-icing fluid can be costly, but effective, and small aircraft can use the same Type I fluid as commercial aircraft. If you do not have access to a deicing crew, Type I fluid may be self-applied using a hand-held sprayer, although this does decrease the holding time.
What is the difference between a deicing agent and an anti-icing agent?
The deicing process removes already existing ice buildup, but naturally the best solution is for ice to not form in the first place. If you will be taking off in freezing rain, snow, or sleet, precipitation could start building up on your aircraft before you ever leave the ground.
This is where anti-icing agents come in. While a deicer removes contamination which has already built up on the aircraft, an anti-icing agent aims to prevent that accumulation before it ever starts. Anti-icing agents have a glycol and water composition similar to deicers, and they are applied to the same areas of the aircraft, however the color and composition ratio are different. Anti-icing fluids have a much higher concentration of glycol, and they also include a thickening agent to help the solution stick to the plane during takeoff. The most common choice – Type IV anti-icing fluid – is a thick, green substance which, unlike Type I deicer, is not heated prior to application and is capable of withstanding lower temperatures down to -20°F. Type II, III and IV anti-icing fluids are comprised of at least 50% and up to 100% glycol.
According to the FAA, the timing of the application is critical. Anti-icing agents must be sprayed on within three minutes of deicing, and if the deicer has frozen to the plane or frost has reformed, the aircraft must be deiced again prior to applying the anti-icing fluid.
In some cases, such as with a thin layer of frost, an aircraft may be able skip the two-step process and instead opt for a one-step deicing and anti-icing procedure using a Type I deicer. In other cases, such as when an aircraft is being prepared for an overnight stop, the two-step process will be necessary and a stronger, less diluted anti-icing fluid can be used.
During cold, inclement weather, deicing is a vital step to safeguard your aircraft. Skipping or skimping on deicing is dangerous and can cause a crash due to the negative aerodynamic impact of accumulated frost, ice and snow. Stay safe by following recommended deicing and anti-icing procedures so you have a clean aircraft before you take off.
Want to learn more? ASA Aircraft Systems for Pilots by Dale De Remer does a great job of covering advanced aircraft systems, including pneumatic and deicing systems.