On the evening of October 25, a flight of Sichuan Airlines was revealed to have returned due to a sudden bird strike during the flight. Why is "bird strike" classified as a Class A aviation disaster? How to avoid the phenomenon of "bird strikes" in aviation?
What is a "bird strike"? What's the harm?
Bird strike, also known as bird strike, refers to the incident of local damage caused by a head-on bird impact when an aircraft is flying at low altitude and approaching landing, and later extended to the event of damage to objects and bird injuries caused by collisions between birds and high-speed trains, automobiles, artificial buildings and other facilities.
Affected by bird migration and its living habits, bird strikes have the characteristics of suddenness and seasonality, and spring and autumn are also one of the high incidence periods of bird strikes. In the field of aviation, bird strikes may cause flight delays, returns, interruption of take-offs, etc., and in severe cases, damage to aircraft and accidents.
An airplane that was hit by a bird. Network Infographic
The incident of a bird hitting an airplane and killing people has been around since 1912. In 1912, Cal Rodgers, known as the "pioneer of aviation" in the United States, accidentally collided with a seagull while flying an airplane, and the plane crashed and died.
One of the most famous bird strikes was the crash of US Airways Flight 1549 in Hudson's Bay, New York, in January 2009. Shortly after the flight took off from New York, the flight was struck by geese and both engines lost power, but fortunately the pilot managed to force the lost airliner to land on the Hudson River, and all the passengers were rescued. The event became known as the "Hudson River Miracle" and was later adapted into the film Captain Sully.
US Airways Flight 1549 crash-landed on the river. Network Infographic
The most serious bird strike in aviation history was the Comet airliner bird strike accident over Boston in the United States in 1960. A flock of up to 20,000 starlings flew onto the plane's course, and a large number of starlings were sucked into the engine, and 3 of the 4 engines lost power, causing the plane to crash quickly and killing 62 of the 72 people on board.
According to media reports, between 2012 and 2016, there were more than 8,000 confirmed bird collisions in British airspace, while the United States has more than 13,000 bird strikes every year, and the economic losses caused by bird strikes are about 650 million yuan per year. Globally, more than $10 billion is spent annually in related accidents for aircraft damage or flight delays.
According to statistics, there were 17,135 bird strike incidents and 1,125 bird strike accidents in the 10 years from 2006 to 2015. In 2015, there were 185 accidents caused by bird strikes by civil aviation transport aircraft in China, accounting for 49.47% of the total number of accidents of all types in the year, making it the largest type of accident syndrome.
Statistics of China's civil aviation bird strikes from 2006 to 2015. Source: Civil Aviation Network of China
To this day, the "bird strike" incident is still a major hidden danger to aircraft flight safety, and it is also a worldwide problem in the aviation industry, and the International Aviation Federation has classified bird strikes as a Class A aviation disaster.
Why are "bird strikes" so powerful?
According to the International Civil Aviation Organization (ICAO), the most likely part of an aircraft to collide with birds is the engine, followed by the wings, windshield, radome, fuselage, and landing gear.
Bird strike and aircraft impact probability chart. Network Infographic
When the aircraft reaches speeds of more than 120 km/h, almost all flying birds cannot avoid it. There are two main threats to aircraft caused by bird strikes, one is that the engine is sucked into the engine and causes the engine to work abnormally or even lose power. When birds collide with the engine and are sucked into the air intake, the fan blades of the turbine engine will be deformed, or the engine will be stuck, causing the engine to stop or even catch fire; Second, due to the direct damage to the structure of the aircraft due to the high-speed impact, if a large bird hits the windshield, it may cause the windshield to break or be missing, and the pilot will fly the aircraft under the influence of strong winds, which becomes quite difficult. If the shield of the navigation equipment is breached, the aircraft will lose the guidance of the navigation system.
Intuitively, birds weigh only a few hundred grams to a few thousand grams, while airplanes weigh tens or even hundreds of tons. According to some data, according to the momentum theorem, a bird weighing 500 grams collides with an aircraft with a speed of 370 kilometers per hour, which will produce an impact force of 3 tons, while a 7-kilogram bird crashes into an aircraft with a speed of 960 kilometers per hour, and the impact force will reach 144 tons, which is equivalent to being attacked by a shell.
According to this calculation formula in the article of the Aviation Safety Technology Center of the Civil Aviation Administration of China, the impact force of the collision between the bird and the aircraft depends on the density of the bird and the speed of the collision. However, there are many factors that affect the impact force of a bird, and the accurate calculation of impact force also needs to include the weight of the bird, the impact velocity, the size and shape of the bird, the density of the bird, and the impact angle.
A mathematical equation for calculating the striking force of a bird. Source: Aviation Safety Technology Center, Civil Aviation Administration of China
Airplanes and birds, how to safely share the blue sky?
According to ICAO, at least 80% of bird strikes occur during take-off and landing, and in order to ensure flight safety, two methods are generally used, one is to drive away the birds, and the second is to strengthen and improve the structure and performance of the aircraft itself.
Driving away birds is not an easy task. It is understood that there are 9 migratory bird migration routes in the world, 3 of which pass through China, and most of the country are located on important international migratory bird migration routes. There are many kinds of birds, and it is difficult to predict their appearance, so how to protect the birds while ensuring the safety of aircraft flight is a test of people's experience and wisdom.
The Airport Department of the Civil Aviation Administration of China has issued the "Measures for the Prevention and Management of Bird Strikes and Animal Intrusions at Transport Airports", which requires airports with a high risk of bird strikes to be equipped with professionals with backgrounds in biology, agriculture and environmental science, and designates and improves the prevention methods of bird strikes and animal invasions at airports, and carries out patrols, drives, and recording activities.
Nowadays, most of the airports across the country are equipped with bird repellents who specialize in bird repellent work, strictly guard key parts such as aircraft take-off and landing points, notify bird repellent vehicles to drive away in time when they find bird conditions, and report to the tower in time when they find that there are bird flocks outside the fence that affect flight safety, so as not to cause potential safety hazards to aircraft take-off and landing. At the same time, a variety of physical equipment such as directional acoustic wave bird repellent device, wind terror eye, and bird blocking net are also used on the ground of the airport to repel birds.
Bird-driving windmills at Tianjin Binhai International Airport. Xinhua News Agency
Solar sonic bird repeller at Xining Caojiapu International Airport. Xinhua News Agency
It is also a way to study the living habits of birds and reduce the number of birds near the airport from the ecological chain level, mainly including removing weeds, removing benthic organisms in waterlogged areas, changing bird habitats and foraging ground distribution, etc. In order to prevent birds from the roots, Hangzhou Xiaoshan Airport planted "dogtooth roots", which grow low and have thinner seeds, which are less suitable for insects to inhabit; Sunan Shuofang Airport and Yining Airport chose to plant non-bird-attracting grass species such as peony and lavender respectively; Ordos Airport in Inner Mongolia captures rats by arranging rat cages and rat traps; Ningbo Airport has introduced a simulated natural enemy of birds, a model eagle, to deter birds. The birds have nothing to eat, no place to sleep, and "natural predators" are eyeing them, so they naturally consciously stay away from the airport.
Yining Airport, surrounded by lavender. Source: Civil Aviation Network of China
As early as 1997, Shanghai Pudong International Airport carried out a bird habitat replacement ecological project, which expanded the ecological capacity of the Jiuduansha area to replace the ecosystem service function of the tidal flat wetland around the airport as a bird habitat, and guided high-risk bird species to "move" from the airport area to promote bird protection.
In addition to bird repellent, it is also important to design the aircraft itself to be "anti-bird strike". In the design of anti-bird strike aircraft, two concepts are usually adopted internationally. One is to "hit the hard", by improving the materials of the aircraft to increase the strength to cope with the huge impact of bird strikes. The second is the use of energy-absorbing materials, like a sponge absorbing water, the body material will absorb the impact force to ensure that the aircraft structure is not lost. This practice is currently very common in automobiles, but it is also difficult to develop and popularize applications in aircraft.
Although a huge amount of manpower and material resources have been invested, until now bird strikes are still an international problem in the aviation industry, how can planes and birds safely share a blue sky and achieve harmonious coexistence, we still need to continue to explore and study.
Integration: Xu Le
Editor: He Xin
Sources: Xinhuanet, CCTV News, Guangming Daily, China Science News, China Civil Aviation Network, etc