A passing winter storm has blanketed Zurich Airport in heavy snow, resulting in a temporary closure. Following the diligent work of the snow removal team, it is now time to resume flights. Before this Airbus A220 can take to the skies again, the residual snow on its wings and fuselage must be removed. It is patiently waiting for its turn at the de-icing pad, a bit like a beauty makeover.
Why is De-Icing necessary? Well, Flight Safety First!
The necessity of de-icing becomes apparent when considering that ice, frost, or snow on the aircraft not only reduce lift but also simultaneously increases drag and the overall weight. Neglecting to de-ice the aircraft could, in extreme cases, lead to a critical flight condition.
Once all passengers are on board, and the doors and cargo doors are closed, de-icing can commence. Depending on local regulations, this may occur either directly at the gate or at a designated de-icing pad. Pilots use checklists to configure and then the procedure can begin. Typically, a vehicle approaches each side of the aircraft, and the ground crew promptly begins spraying the aircraft.
Behind the general term "De-Icing," there are, in fact, two subcategories. While they may appear similar at first glance, they differ with a small but significant distinction. Depending on weather conditions, we determine whether the aircraft needs only de-icing or requires an additional protective layer. This second step, known as "Anti-Icing," becomes necessary only in the presence of precipitation and prevents the reformation of ice on the critical flight surfaces. To facilitate identification, they are also distinguished by color: Regardless of the type of de-icing fluid, the de-icing step is always marked in orange, while the anti-icing step is colored green.
Back to our flight
After a short wait, we taxied to the assigned de-icing pad, completed the checklist, and coordinated the procedure with the ground crew via radio. The method chosen primarily depends on the weather conditions. In our case, since it's still snowing, both steps are required. In the first step, the thick layer of snow is removed, and then, in the second step, a protective layer is applied. In both steps, a mixture of water, glycol, and other additives is used. This mixture is non-toxic and biodegradable. The ground crew calculates the optimal ratio that provides the necessary protection while being cost-effective. Based on this ratio and the current weather conditions, we can calculate the "Hold Over Time" in the cockpit. This timeframe determines how long the protective layer will last, shielding the critical flight surfaces from the reformation of ice and snow. It can range from a few minutes in very cold temperatures or heavy precipitation to around an hour in milder conditions.
From the cockpit, we watch the ground crew treating our aircraft with utmost care ensuring that we can take off safely shortly. This duration, by the way, varies between 10 and 30 minutes, depending on the size of the aircraft, the de-icing method applied, and the current weather conditions. Typically, during the de-icing of an aircraft at Zurich Airport, at least five members of the ground crew are involved. On one side, the two operators of the de-icing vehicles who skillfully maneuver their equipment high above on the articulated arm to delicately spray the aircraft. They are supported by various positions, including the De-Icing Coordinator, overseeing the entire process, the Pad Coordinator (bottom right), communicating with the pilots via radio, and a De-Icing Pad Coordinator (bottom left), monitoring the actual de-icing process.
Especially impressive shots are captured during twilight and at night when using a slightly longer exposure time, creating a distinctive visual effect.
“SWISS Three-Alpha-Zulu, from De-Icing”
Enjoy this collection of timelapse sequences of the winter ops at ZRH.
About the Image
About "Behind the Image"
In my photo calendar "Up in the Sky" I get to share my favorite aviation pictures with you. This blog series will complement the product and will tell the story about the moment the picture was taken. It will also share comprehensive information about what happend on the flight deck and how the picture was created.