On December 2, local time, a "Cessna Citation X" aircraft at Munich International Airport in Germany was frozen on the runway due to heavy snow. According to relevant reports, at least 760 flights at Munich International Airport were canceled due to snowfall, leaving thousands of passengers stranded.
Airplanes are an important means of travel for people, and meteorological factors are one of the important factors affecting the safe flight of airplanes. According to statistics, 30% of flight accidents are related to weather, and most of the flight accidents caused by meteorological reasons occur before and after the aircraft lands, accounting for about 57%.
So
First, let’s take stock of the meteorological factors that affect aircraft flight safety in winter:
visibility
When the aircraft is facing snow, fog, or low clouds during the takeoff or landing phase, and the visibility is lower than the safe flight visibility standard, the pilot cannot continue to perform takeoff or landing operations, and should postpone takeoff or return, and then perform flight or landing operations when the visibility improves. Generally speaking, when the runway visibility is lower than 550 meters, the plane cannot land; when the runway visibility is lower than 350 meters, the plane cannot take off.
Low clouds have a big impact on visibility. If the low cloud height is less than 100 meters, the pilot's visual distance is often only 1 kilometer. When the cloud base height of an airport operating in Category II is less than 30 meters, the aircraft cannot land. Low clouds are often associated with heavy fog, which further increases the difficulty of takeoff and landing and threatens the safe flight of aircraft.
△Aircraft in low visibility
low temperature
Low-temperature weather can easily cause ice accumulation, snowfall, frost and other conditions, resulting in the failure of aircraft accessories and facilities and equipment, reduced runway friction coefficient, continued low visibility and other consequences. In severe cases, it can lead to aircraft operation delays, airport closures, aviation crashes, etc.
Aircraft icing refers to a weather phenomenon in which ice and frost condense on the ventilation surface of the aircraft when the aircraft is flying in clouds below 0°C. Aircraft ice accretion usually forms in the range of 0℃ to -20℃, and strong ice accretion mostly occurs in the range of -4℃ to -10℃. Generally, ice accumulation is most likely to occur at altitudes below 5,000 meters, especially around 3,000 meters. Ice accumulation generally occurs in parts with small curvature radii such as aircraft wings, tail fins, and engine air inlets.
The accumulation of frost not only increases the weight of the aircraft, but may also cause changes in the streamlines of the wings and unbalanced propeller blades. It may also reduce the efficiency of the aircraft power unit, affect aircraft instruments and communications, and even cause malfunction or malfunction. If frost occurs in the cockpit, it will also block the driver's view.
△Ice accumulates on the fuselage of the aircraft
Strong wind
When an aircraft performs operations such as climbing, level flight, take-off and landing, and descending, the wind speed and direction will have a great impact on it. Affected by the cold air from Siberia, my country experiences significant cooling in winter, with large changes in wind direction and speed, often accompanied by gusts, which has a certain impact on aircraft flight safety.
△Plane landing under strong crosswind conditions
In windy weather, the most harmful thing to flying is wind shear. According to statistics, about 40% of flight accidents that occur during takeoff and landing are caused by low-altitude wind shear, and the majority of accidents occur during landing, accounting for about 80%. Wind shear refers to sudden changes in wind direction and speed within a short distance. Below 600 meters is called low-altitude wind shear. Due to sudden changes in wind direction and wind speed, the aircraft will produce complex oscillatory changes such as roll, yaw, and sudden speed changes when the aircraft dives. Since wind shear often occurs in a very short moment, the pilot cannot respond immediately and the aircraft may lose control.
△Schematic diagram of an aircraft encountering low-altitude wind shear during landing
Low-altitude wind shear has huge energy. Once strong wind shear or strong downdraft is found, avoidance measures should be taken in time and must not be rushed through.
snowfall
Snowfall can easily cause ice to form on the aircraft fuselage, causing delays in the aircraft's operational response. At the same time, it may also cause the aircraft runway to freeze, which will reduce the friction between the aircraft tires and the ground, causing the aircraft to skid or even run off the runway. In addition, snowfall also seriously reduces visibility and affects the sight of pilots.
When snowfall occurs, the airport must carry out snow removal work on runways, aprons and other areas. At the same time, the aircraft that are about to take off must also carry out ice and snow removal work. If the snowfall lasts for too long, the amount of snowfall is too heavy, and the snow removal cannot guarantee the normal takeoff and landing of the aircraft, the flight will be canceled and the flight plan will be made after the weather improves and the snow removal is completed.
△Staff are removing snow from the aircraft
Let’s take a closer look at what’s so special about aviation weather forecast↓
In the aviation field, there are also aviation weather forecasts specially produced to ensure the safety of aircraft takeoffs, landings and air flights. Aviation weather forecast is an important basis for organizing and implementing flights. Aviation weather forecasts include not only routinely released aviation weather forecasts such as airport forecasts, landing forecasts, regional forecasts, and route forecasts, but also non-routinely released aviation important weather forecasts such as important meteorological information and low-altitude weather information. Aviation weather forecasts for airports mainly include two categories. One is the airport forecast that is valid for 9 hours or 24 hours, and is updated every 3 hours or 6 hours; the other is the landing forecast that is valid for 2 hours and is updated every half hour or one hour. Every flight needs to obtain airport forecasts for the destination airport and alternate airport before departure.
Compared with weather forecasts in daily life, aviation weather forecasts have more detailed and higher requirements in terms of content, time and quantification. The content includes wind direction, wind speed, visibility, runway visibility, air temperature, weather phenomena (fog, snow, sandstorms, thunderstorms, etc.), cloud cover, cloud shape, aircraft turbulence, aircraft ice accumulation, low-altitude wind shear, etc. These meteorological information are important guarantees and basic basis for aviation safety.
Under complex weather conditions in winter
Wish every flight
May everything be safe and smooth!