A bird strike is a collision between a bird and an aircraft. It occurs when a bird collides with an aircraft during flight operations. Bird strikes are a serious aviation hazard that can cause significant damage to aircraft and in some cases lead to accidents resulting in loss of life. Understanding what bird strikes are, why they occur, and how to prevent them is important for improving aviation safety.
What causes a bird strike?
There are several factors that can cause a bird strike:
Bird behavior
Birds are naturally attracted to airports due to the presence of large open grassy areas adjacent to runways and taxiways which are ideal locations for birds to forage and nest. Airports often provide a haven for birds away from natural predators. Birds also tend to be attracted to the insects that congregate around airport lights.
Aircraft flight paths
The flight paths of aircraft, especially during takeoff and landing, take them through the airspace commonly used by birds for foraging and migration. The aircraft and birds are thus on a collision course during these phases of flight.
Timing of flight operations
Bird activity tends to peak during migration seasons in the spring and fall as well as during the early morning and late afternoon hours. Scheduling aircraft movements to avoid these high bird activity periods can reduce the likelihood of collisions.
Aircraft and engine design
Modern jet aircraft with high bypass turbofan engines are quieter thus making it more difficult for birds to detect and avoid them. The inlet design of jet engines can also draw birds into the path of rotating engine blades.
What are the consequences of a bird strike?
Bird strikes can lead to a number of hazardous outcomes:
Structural and engine damage
Collisions at high speeds with birds that have a substantial weight (large birds like geese or gulls) can damage flight critical structures like the windshield, leading edges of the wings, and components of the empennage. Ingestions into jet engines can destroy multiple compressor blades and cause engine failures.
Emergency landings
Damage or engine failure resulting from a bird strike may require an immediate emergency landing. This typically occurs shortly after takeoff when the aircraft is close to the ground and options are limited.
Crash landings
Total loss of thrust from multiple engine failures caused by large flock ingestions can lead to crash landings. Ditching in water may be the only option available in these situations.
Injuries and fatalities
Bird strikes have directly resulted in over 250 fatalities worldwide. Injuries to aircrew and passengers can occur from the direct impact as well as debris from any resulting onboard fires or aircraft structural breakup.
Financial costs
Repairing bird strike damage to aircraft and engines is very costly, often exceeding $1 million for a large jet airliner. Other costs arise from aircraft downtime during repairs.
How are bird strikes prevented?
A variety of methods are used to reduce the risk of bird strikes:
Habitat modification
Eliminating ponds, removing trees, keeping grass very short, and draining wetlands makes the airport environment less attractive to birds.
Bird dispersal techniques
Birds are frightened away from the airport by pyrotechnics, propane cannons, sirens, flashing lights, using trained raptors (falcons, eagles, hawks), removing nests, and trapping and relocating birds.
Radar surveillance
Mobile bird detection radar systems track bird flocks in real time around the airport so aircraft can be warned and avoid high risk areas.
Aircraft lighting
Using only minimum required exterior lighting at night, eliminating upward pointing floodlights, and installing pulsating lights instead of steady burning lights can reduce attraction of insects and thus birds.
Flight schedule planning
Consulting bird strike risk models and wildlife hazard advisories to schedule takeoffs, landings, and training activities during periods of low bird activity.
Key statistics on bird strikes
Some key numbers summarizing the bird strike issue:
Annual global bird strikes | 40,000 – 80,000 |
---|---|
Annual U.S. bird strikes | Over 6,000 |
Annual U.S. damaging strikes | Over 500 |
Total aviation bird strike costs in U.S. | $650 million |
Largest birds pose hazard | Over 4 pounds |
Most hazardous birds to aviation
The birds that cause the most collisions due to their size, flocking behavior, and population numbers include:
- Geese
- Gulls
- Ducks
- Vultures
- Hawks
- Crows
Hotspots for bird strikes
Certain regions see higher rates of bird strikes because they are located along major bird migration routes. These include:
- U.K. and Northern Europe
- Eastern U.S.
- Alaska and Yukon
- Coastal Peru and Chile
Notable bird strike accidents
Some of the most severe aviation accidents directly attributed to bird strikes include:
US Airways Flight 1549 “Miracle on the Hudson” (2009)
After striking a flock of geese shortly after takeoff from New York LaGuardia Airport, both engines lost power forcing an emergency water landing in the Hudson River. All 155 passengers and crew survived.
Ethiopian Airlines Flight 604 (1988)
After taking off from Bahir Dar Airport, an ingestion of numerous speckled pigeons into both engines caused a dual flameout. The Boeing 737 crashed into a lake killing 35 of 104 people on board.
Eastern Air Lines Flight 375 (1960)
Multiple Canada geese were ingested into all four piston engines after takeoff from Logan Airport in Boston resulting in a ditching in Boston Harbor. Although no fatalities occurred, the aircraft was written off as damaged beyond repair.
Research on reducing bird strike risks
Ongoing research efforts to find better ways to avoid and mitigate bird strikes include:
Improved bird detection technology
Developing bird radars more optimized for tracking individual birds and differentiating bird species. Investigating integration options with onboard aircraft systems.
Enhanced aircraft system resilience
Designing turbine engines that can better withstand bird ingestion events without catastrophic failure. Using redundant aircraft systems to provide backup capability.
Aircraft lighting innovations
Finding novel external aircraft lighting techniques that will repel birds and make aircraft more easily detectable while not blinding pilots.
Avian behavioral analysis
Studying bird vision, hearing, and flight behaviors to predict reactions to aircraft approach and improve dispersal strategies. Focusing on species most hazardous to aviation.
Airport habitat manipulation
Developing novel low-cost approaches to rapidly modify airport vegetation, drainage, and land features to become less attractive to hazardous birds.
Conclusion
Bird strikes pose an ongoing and serious hazard to aviation safety across the globe. They can inflict severe damage to aircraft leading to potential crashes and loss of life. A variety of strategies are employed to deter birds from airports and avoid collisions, but challenges remain. Continued research and data analysis will provide for improved solutions to this complex issue through enhanced technology, infrastructure design, flight planning, and staff training. With diligent risk management efforts, the dangers to aircraft, passengers, and crews posed by bird strikes can be progressively reduced over time.