Let It Snow
It’s that time of year again, you step outside into the frigid air to find your car covered in frost. Well the same thing happens to our airplanes. Your solution is to pull out the scraper and make a couple passes until you have just enough space to see out the front windshield. Unfortunately it’s not that easy with airplanes.
Frost, snow, and ice on the wings can reduce the amount of lift created. These contaminates can also reduce aircraft controllability and handling. There are a few different methods to deice the aircraft. Mechanical, via scraping, heated air and chemical. A combination can be used as well. In the airline industry, the most commonly used method is a chemical deicing fluid.
After everyone is onboard, the airplane is pushed back from the gate and taxis over to the designated deicing area. Deicing can occur just off the gate as well. Trucks filled with the deicing fluid, glycol diluted with water, stand by until the flight crew configures the airplane for deicing. Once the pilot notifies the ground crew that the plane is configured, the deicing procedure begins. The trucks use high pressure hoses to spray the heated fluid, known as Type I fluid, on the aircraft to remove icy contaminates. The fluid is orange to help distinguish it from other types of deicing fluid. After the plane has been sprayed down, ground personnel inspect the aircraft to make sure all ice has been removed. The trucks move out of the way and the plane taxis out for departure.
If icy precipitation is actively falling, more steps must be taken to ensure that snow or ice does not adhere to the plane prior to takeoff. Once in the air, the plane has deicing methods such as heated wings and engines to remove ice in flight. But this protection isn’t as effective on the ground. So another type of fluid is applied known as anti-ice fluid to deter ice formation prior to departure. This green colored fluid, known as Type IV, is applied after any snow or ice is removed with Type I. Type IV has a thicker viscosity and absorbs falling precipitation by reducing the temperature at which water freezes.
But Type IV won’t protect from ice accretion for an indefinite amount of time. Many factors determine how long the fluid will protect the plane such as the mixture of the fluid, outside air temperature and the amount and type of precipitation falling. We use tables with this information to determine the “holdover time” that the anti-ice fluid will be effective. The plane needs to takeoff within this holdover time otherwise the aircraft needs to be inspected for ice accretion and possibly start the de-ice/anti-ice process all over again.
This process can be frustrating for passengers because it can sometimes cause delays on the ground. But we need to remember that frost and ice on the wings is dangerous and must be removed before we leave. Thankfully, this winter season you can pass the time while we deice, by reading a book or playing a couple more games on your recently approved electronic device.