Relationship between aviation meteorology and flight safety

Every stage of aircraft take-off, landing and air flight will be affected by meteorological conditions. Wind, temperature and air pressure are all important meteorological factors affecting flight. The wind on the ground will directly affect the operation of the aircraft, and the wind at high altitude will affect the flight speed and fuel consumption of the aircraft on the route. Temperature can change the thrust of the engine, affect the airspeed indicator, take-off and landing distance and so on. When the temperature is higher than the standard atmospheric temperature, it will increase the take-off distance and climb time and reduce the aircraft load. Air pressure will affect the flying height of the plane. Due to the frequent changes of air pressure in various places, the indication error of air pressure altimeter is often caused. In addition, weather phenomena such as thunderstorms, low clouds, low visibility, low-level wind shear, atmospheric turbulence, air jet, bumps and icing directly threaten flight safety.

Thunderstorm is one of the main weather affecting flight in summer. Lightning and strong thunderstorm electric field will seriously interfere with medium and short wave radio communication, and even temporarily interrupt communication. When there is a thunderstorm over the airport, heavy precipitation, poor visibility, sudden change of wind direction and gust have great influence on flight activities and ground equipment. Heavy precipitation, turbulence (including ascending and descending airflow), icing, thunder and lightning, hail and squall caused by thunderstorms have caused great difficulties in flight, which seriously led to the loss of control, damage and horsepower of the aircraft, directly endangering flight safety.

Low cloud is one of the dangerous weather that endangers flight safety, and it will affect the landing of aircraft. When the airport is covered with low clouds, if the altitude of the plane from the ground is very low after the clouds leave and it is not aimed at the runway, it is often too late to correct it, which is easy to cause a go-around. Sometimes due to improper command or operation, it may also cause an accident in which the plane collides with an obstacle on the ground and stalls.

Low visibility has a considerable impact on the take-off and landing of aircraft. Rain, clouds, fog, sandstorm, floating dust, smoke and haze will reduce visibility and affect aviation safety. Poor visibility on the ground will easily lead to yaw and disorientation, which will affect the safe landing when landing, and it will endanger flight safety if it is not handled properly; When the route is foggy, it will affect the navigation of landmarks; When there is fog in the target area, it will have a serious impact on activities such as visual landmark flight, airdrop, photography and inspection.

Low-level wind shear is a serious threat to the take-off and landing of aircraft. Wind shear is a sudden and obvious change of wind direction and wind speed in a short distance. Strong wind shear will make the plane go around prematurely or be forced to go around. Under certain conditions, it will also lead to aircraft stall and uncontrollable danger, and even lead to flight accidents.

Turbulence in the atmosphere and rapids in the air will both cause the plane to bump. Due to the irregular vertical movement of the air, the plane rises and sinks. Severe turbulence will increase the wing load, make the wing deform or even break, or make the plane sink or rise hundreds of meters.

Ice is very dangerous for flying. Due to the accumulation of frost, the weight of the plane has increased. More importantly, it can be imagined that the plane crash is caused by the change of wing streamline, the imbalance of propeller blade weight, or the closure of carburetor intake pipe, the difficulty of retracting landing gear, the failure of radio antenna, the reduction of carburetor intake, the reduction of aircraft horsepower, the freezing of throttle, the cut-off of fuel source, the freezing of cockpit windows and doors, and so on. There are three forms of icing: clear ice, coarse ice and rime. Ming ice and Mao ice are the most dangerous. Because it is firm, hard to eliminate and grows extremely fast, it has become the most dangerous kind of ice accumulation.

When adverse weather conditions occur, in order to ensure the safety of passengers and aircraft, airlines and air traffic control departments will regulate the take-off and landing of flights to varying degrees according to the weather changes, which will inevitably lead to flight delays and passengers stranded in and out of Hong Kong.

Strong convective weather mostly occurs in the cloud system formed by cumulonimbus clouds, and the rainfall range can be large or small. Sometimes it rains in the east and west, and sometimes it goes down from Hedong to Hexi. When strong convective weather (commonly known as thunderstorm) occurs, short-term heavy precipitation is often accompanied by severe weather such as thunderstorm, tornado and hail. It will cause great flight difficulties, which will seriously cause dangerous situations such as loss of control, damage and reduced horsepower. Strong electron current can cause lightning strike and damage radome, antenna, windshield and wing, while light electron current can cause aircraft body ablation. Strong bumps will cause structural deformation of the plane, of course, passengers in the plane are more dangerous; If there is a thunderstorm in flight, the aircraft strays into the cumulonimbus cloud or enters the heavy precipitation area, which will easily induce the engine to stop, make the wing and fuselage surface rough, increase the resistance, reduce the favorable angle of attack, reduce the lift and resistance, increase the stall speed, and seriously reduce the aerodynamic performance of the aircraft; If you enter a thunderstorm area during take-off and landing, you may encounter low-altitude wind shear under the influence of downdraft, and the aircraft will be difficult to control, easily lose its direction, and even stall and fall.

Causes affecting normal flight

Weather reason

At present, the weather is the main reason for flight delay. It is generally believed that the bad weather is obvious and passengers can understand the flight delay, but it is not.

At present, the explanation of civil aviation for the delay caused by bad weather is that the weather can not meet the flight standards and can not take off on time. General civil aviation service personnel often don't know exactly the impact of bad weather on flights like passengers. From the passenger's point of view: bad weather means strong wind, heavy rain and fog, planes may not be able to take off and land, and flights may be delayed. However, this understanding is one-sided and will lead to many misunderstandings. Think that civil aviation is deceptive, especially some flights can go and some can't.

The simple word "weather reason" actually contains many situations: the weather conditions at the departure airport are not suitable for take-off; The weather conditions at the destination airport are not suitable for landing; The meteorological conditions of flight routes are not suitable for flying over and so on.

In order to ensure flight safety, there are many meteorological standards for flight, take-off and landing. Here, first introduce where the weather conditions affect a flight, which will help you understand:

-Weather conditions at the departure airport (visibility, low-level clouds, thunderstorm area, strong crosswind)

-Weather conditions at the destination airport (visibility, low-level clouds, thunderstorm area, strong crosswind)

-Meteorological conditions on the flight route (high-altitude thunderstorm area)

-Unit status (technical level of the unit, analyzing and mastering the current weather and trends to make professional decisions)

-the condition of the aircraft (the aircraft's safety standards for meteorological conditions and the failure of some airborne equipment on the premise of safety make the aircraft unsuitable for flying in such weather conditions)

-Subsequent situations caused by bad weather (mostly damage to airport navigation facilities and substandard runways, such as serious icing and water accumulation)

Common situations to dispel doubts:

Question 1: The city where the destination airport is located has good weather conditions and good visibility. Why is it still delayed because of the weather?

A: The weather in the destination city is good. There is no heavy rain or strong wind. The passengers are puzzled, and it is still delayed. Just because the weather in the city where the destination airport is located is good does not mean that the airport is suitable for plane landing. Low clouds and thunderstorms cover the airport take-off and landing passages, which is a common factor leading to this delay.

Knowledge points: In order to ensure flight safety, even if the plane is in the automatic landing state, the pilot must be able to see the runway and the ground completely at a certain height (generally 60 meters) before landing. If you can't see the runway at this time, you are not allowed to land.

Question 2: The city where the destination airport is located has good weather conditions and good visibility, and the airport is also taking off and landing normally. Why is it still delayed because of the weather?

A: This situation is often because the meteorological conditions of flight routes are not suitable for flying over, such as thunderstorm areas. In this case, the plane often has to wait on the ground.

Knowledge points: once there is a thunderstorm area on a narrow route, in some cases, it can bypass the thunderstorm area. However, due to flight safety and national defense needs, civil aviation routes are strictly restricted, and there is little room for flight and maneuver. When the thunderstorm area is large, this method will not work.

Question 3: Why are some flights to a certain place available, while others are told that they can't because of the weather?

A: There are many possibilities for this situation. First of all, it must be clear that the standard of aircraft take-off and landing is related to the model. The specific safety standards set by the same aircraft in different airlines may also be different, and the captain will make different decisions according to the current weather and trends. It depends on the captain's decision after judging the state of the plane, airport, weather, etc. The Civil Aviation Law stipulates that "if the civil aircraft, airport and meteorological conditions are found not to meet the requirements and flight safety cannot be guaranteed, the pilot-in-command has the right to refuse to fly".

Question 4: Why didn't you tell me that I couldn't land at the destination airport because of the weather, and I had to alternate to other airports or return, and some planes could land normally?

A: Although the meteorological department of civil aviation relies on advanced equipment to continuously issue more accurate weather trend forecasts to facilitate flight operation and scheduling, the weather conditions are constantly changing and it is difficult to accurately judge. This will lead to a sudden deterioration of weather conditions when landing, resulting in the inability of the plane to land. For safety reasons or fuel shortage, the plane will have to alternate to other airports.

The weather is constantly changing, and it may be bad weather for a short time. Five minutes ago, the weather allowed the plane to land, five minutes later, and your plane just caught up with the bad weather conditions and could not land. This is a very common phenomenon. At the same time, as mentioned above, when the weather is on the edge of the standard, it is up to the captain to decide whether to land. The captain thinks that the weather is not suitable for landing at other airports or returning to other airports, and should absolutely support it.

When the flight is delayed due to weather, passengers should pay attention to the following points:

The weather reason not only refers to the weather conditions in the city where the destination airport is located. Aircraft take-off and landing are not afraid of strong winds and heavy rain. The key meteorological factors are visibility, low clouds near the airport take-off and landing passages, and strong crosswinds. It is normal for your flight to be delayed due to the weather.

Responder: Bird-watching pig on the tower-manager level 5.