Although snowfall and the resulting natural phenomena can nowadays be predicted with the help of technology, the rapid development of these events requires constant vigilance in terms of flight safety. Pilots should anticipate the possible effects of snowfall during take-off, landing and in-flight and be extremely careful about snow-induced optical illusions. The degree of precautions that can be taken against the problems that snowfall may cause in terms of flight safety can vary from pre-determining alternative airports where landing can be made in advance to rescheduling the flight day to a different date.

What is SNOWTAM?

SNOWTAM, a special type of NOTAM, is a notification, the content of which is defined by the International Civil Aviation Organization (ICAO), stating that the conditions that may occur due to snow, sleet or icing over the area where the flight will be operated and that may endanger flight safety have occurred or that these conditions have disappeared. SNOWTAM is issued by the airport authority with a maximum validity of 24 hours. If there is a significant change in weather conditions during this period, a new SNOWTAM can be released.

Impact of Snowfall on Pat Fields at Airports and Aircraft on the Ground

Snowfall and the strong winds that accompany it can adversely affect the safety of aircraft both on the ground and in the air. Reduced visibility due to snowfall and accompanying fog may cause flight delays and cancelations. The intensification of snowfall requires runways to be closed and regularly cleared, if the runway cannot be cleared fast enough, all operations at the airport may be temporarily suspended. At international airports, pat areas, runways and taxiways are cleaned regularly. If it is not such an airport, the runway taxiways and runways are cleaned before the flight, and if there is no possibility of cleaning, the flight is postponed. If snow falls on the aircraft during standby; if the aircraft is a small single-engine aircraft, the snow that has fallen on it is cleaned so that the thinnest layer of snow does not remain. It is wiped with a dry cloth and then anti-icing is applied. If the aircraft is a large twin-engine aircraft, de-icing is performed first, followed by anti-icing.

Cleaning Snow Accumulated on Aircraft

Snow, which can distort the shape of the wings when it accumulates on them, and ice, which also poses a danger to flight safety, must be removed before flight. This is done with special equipment and brushes used for this purpose. Again, it is important to thoroughly clean the snow that has accumulated around and inside the engines. If the aircraft is in an open area during snowfall and a strong wind is blowing, special attention is paid to areas such as the pitot tube, fuel ventilation hatches, heater and carburetor inlets, landing and tail landing gear slots.

Eye Errors During Flight

Surfaces such as clouds, snow or white sand reflect most of the light that falls on them, resulting in the optical illusion called “white vision”. During long flights over snow-covered areas, the perception of the horizon line can be difficult or even lost due to the blending of the white surface and the horizon covered with white clouds. Losing the eye’s reference to the horizon can cause white all around and thus disorientation.

If it snows after takeoff in Visual Flight (VFR) conditions?

In case of unforeseen snowfall, landing at the nearest airport is the only option. During landing, if the airplane is carbureted, the carburetor needs to be heated (carburetor heat on) to prevent or clean the carburetor from icing. This is not the case for airplanes with injection or other engines.