According to the statistics of the Federal Aviation Administration (FAA) of the United States, the country suffers from over USD600 million of loss and damages due to bird strike every year. Although aircrafts at the present time already adopted a number of preventive measures, more than 200 of personnel died in the bird strike accident within 20 years since 1988. Helicopter is the main rescue aircraft model for NASC at the moment. The average flight altitude of helicopter is up to 2000 feet, which overlaps with that of birds. It is therefore important to pay attention to the bird strike issue. Major bird strike issues are summarized below:
- In 1912, a sea gull strikes the aviator Cal Rogers during his flight. The aircraft crashed to the ground and the pilot died. It was the first recorded bird strike that has caused an aircraft crash.
- On October 4 of 1960, Eastern Air Lines Flight 375 (L-188 Electra aircraft) crashed on takeoff from Logan International Airport in Boston. The aircraft lost all of the four engines and 62 passengers on board were killed in this accident. It is the bird strike accident that caused most deaths ever in the history.
- On September 22 of 1995, the U.S. Air Force E-3 Sentry No. 77-0354 above the Elmendorf Air Force Base in Arkansas. The aircraft lost two engines on the left wing and the aircraft crashed to the forest and lost all 24 people on board.
- On January 15 of 2009, the US Airways Flight 1549 (Airbus A320) struck a flock of Canada geese in the climb-out (about 1,000 feet) after takeoff from New York City's LaGuardia Airport. The aircraft lost all engine power. The aircraft glided to a ditching in the Hudson River. All 150 passengers and 5 crew members were rescued.
Most air crashes or major casualties caused by bird strike occur when a bird (or birds) collides with the engine and is then sucked into the aircraft engine. Although bird is not a hard object, a huge impulsive force can be created when two objects collide with each other when flying at a high-speed. According to the estimation, if a 5 kg flying birds flying at a relative speed of 275 km, it can create an impulsive force that equals to that of a 100 kg hard object falling from 15 m. When the aircraft jet engine suffers from bird strike, the blades that rotate in the high speed will be firstly impacted. Then the bird, which will be cut into pieces, will be drawn into other blades and cause chain damage. If the condition is bad, it can cause engine failure.
As birds mostly fly in airspace below 500 meters, the statistics of the US Bird/wildlife Aircraft Strike Hazard Team (BASH) indicate that 89% of bird strike accidents occur below 500 meters and one third of bird strike accidents occur below 30 meters above the level ground. This height also happens to be the height when fighter aircrafts carry out low-altitude tactical training and, in this moment, the fighter aircrafts can be easily made to stall.
As bird strike can cause such serious damage to flight vehicles and personnel and such accident mostly occurs in areas nearby the airport, prevention of bird strike therefore becomes one of the most important lessons for the aviation safety department of all airports. To proactively decrease the happening of bird strike incident, it is a must to understand the causes of bird strike accident in each airport or airspace in order to prevent or handle it effectively.
Threatening is the simplest and most direct way to drive the birds away and it is often done using gas cannon, scare-eye, sonic bird repellent and hunting.
- Most of the airports are equipped with gas cannon, which is an explosive device ignited with gas. The ground personnel of the airport ignite the gas cannon on a regular basis to produce loud banging noises to frighten birds and drive them away. However, using it over a long period of time will make the birds resistant to its noises and reduce the repellent effect.
- Scare-eye is a huge balloon with predator eyes on the front. As birds are relatively sensitive to eye images, the scare eye that moves together with the wind gives good repellent effect. However, using it over a long period of time can also reduce the repellent effect.
- Used together with a vehicle equipped with high-pitched speakers, sonic bird repellent can drive birds nearby the airport away by recording and broadcasting sonic bird distress calls and predator cries. However, this method is geographically restricted as only the sound recording of local birds produces better repellent effect.
- Hunting is the most primitive way of driving the birds away and is very effective. Hunting birds for a long period of time can effectively control the quantity of birds. However, many people are against it for ethnic considerations and ecological protection.
- Fostering birds of prey is a solution of driving the birds away using birds. That is, taming and feeding some birds of prey and allow them to fly around the site for a period of time. This can create a high density of birds of prey, which can threaten wild birds and push them leave the airport. Fostering large-size birds of prey cannot only drive birds away, but also kill mammals living in the airport as reducing the food supply can also drive birds away. At some of the airports in Europe, North America and Russia, fostering birds of prey is a very effective and successful method.
Besides, using bird bombs, damaging bird habitat and banning pigeon feeding in airport surrounding areas can effectively reduce the happening of bird strike. Where the birds cannot be driven away from the flight path in any of the said methods, the pilots can only do their best to collide with the birds. That is, to detect the birds in order to avoid collide with them. Radar observation of birds has been widely applied in capturing bird migration for decades with undoubted effectiveness. Although it is not possible to accurately identify the bird species, the size, quantity, flight altitude and movement of the birds can be determined. The establishment of the real-time bird strike alert system, which is formed by ground radar and observers, can notify the pilots of the real-time airport and flight path conditions. This system is very important particularly when the weather is poor and when the birds cannot be driven away at night. In other words, if the birds cannot be driven away, the only thing that we can do is to track them in order to prevent bird strike.
- Establish a nationwide bird activity area pattern based on the geographic information system (GIS) by collecting bird investigation results and recording bird strike events over a period of time in order to create a four-dimensional spatial distribution pattern of birds. This pattern can be provided to pilots and help them to avoid bird-strike high-risk areas when drawing up a flight plan. This type of information system has been adopted by the US and Israeli air force and showed an extraordinary performance.
- By taking Taoyuan International Airport as an example, it has installed the lightweight counter-mortar radar, which is currently used by the US army, to prevent bird strikes. This counter-mortar radar has adopted the most advanced electronic 3D full-color monitoring system. Apart from the Dallas Airport in the United States, Taoyuan International Airport is the first international airport that has adopted this radar in Asia.
Conclusions
Although the airport’s aviation safety personnel are doing their best to reduce the happening of bird strikes, the currently used methods are not diversified enough and can be applied only within the airport and in airspace below 60 meters. Therefore, it is not possible to handle or react to all kinds of bird strike accidents. Besides, even if the current preventive measures are 100% successful, only one third of bird strikes can be eliminated according to the statistics of the US army. The entire flight path and areas inside and outside the airport are still very attractive to birds. Furthermore, how to reduce bird strikes that occur in the airspace between 60 meters to 500 meters is still a big challenge from the perspective of aviation safety.
To avoid bird strikes, the competent authority shall, when building an airport, go back to the fundamental and think about if the airport site is in the “hotspot” for birds. For airports that are unimportant in the aspects of military, transportation and economy, it is a must to to evaluate the necessity of keeping the airport. Hengchun Airport is a good example: the south end of its flight path is Lungluan Lake, where waterfowls often gather. When the northeast monsoon strikes in the winter, aircrafts have to approach the airport from the south end. In other words, aircrafts will definitely enter the hotspot for birds – not mentioning this airport has no military, transportation or economic necessity. Another example is Taipei Songshan Airport. As this airport is four sides surrounded by mountains, aircrafts can only enter and leave the airport from Tamshui Valley. As Guandu Plain is a hotspot for birds and the Airport is nearby Taoyuan, its importance in transportation can somehow be replaced by Taoyuan International Airport. Although no serious accident ever occurred in these two airports fortunately, the competent authority shall be precautious and pay great attention to it.
As there are many airports like Hengchun Airport and Songshan Airport in the country, it is a serious question to which all circles shall pay great attention.
Source: FTTW Classroom – The Big Enemy of Aircrafts in the Air: Bird Strikes