Bird strikes are a major concern for the aviation industry. When birds collide with aircraft, they can cause severe damage and even lead to crashes. This poses a huge safety risk for passengers and crew on commercial airliners as well as military aircraft. Finding ways to prevent bird strikes is therefore a top priority.
What is a bird strike?
A bird strike occurs when a bird collides with an aircraft while it is in flight. The bird is usually killed instantly on impact. The force of the collision can damage the exterior of the aircraft by denting or piercing through the fuselage. More seriously, bird strikes can break engine turbine blades, cause engine failure, or break through the windshield into the flight deck.
Bird strikes happen most often during takeoff and landing since these phases involve low altitude flying. However, collisions can occur at any altitude. Large birds like geese and raptors pose the greatest danger because of their size and weight.
How often do bird strikes happen?
Bird strikes are surprisingly common. In the United States, over 16,000 bird strikes were reported to the Federal Aviation Administration (FAA) in 2019 alone. However, the actual number is likely 2-3 times higher since minor strikes often go unreported.
Globally, it is estimated that bird strikes cost the aviation industry over $1.2 billion per year in direct damage repair and associated costs. Over 250 people have been killed worldwide due to bird strike accidents.
| Year | Reported Bird Strikes in US |
|---|---|
| 2019 | 16,228 |
| 2018 | 14,661 |
| 2017 | 13,734 |
What factors influence bird strike risk?
Several factors can contribute to a higher risk of bird strikes:
- Altitude – Most strikes happen below 3000 feet during takeoff and landing.
- Location – Airports near wetlands, garbage dumps, or other bird attractions are at higher risk.
- Season – Bird activity increases during spring and fall migration seasons.
- Time of day – Bird strike risk is higher at dawn and dusk when birds are active.
- Aircraft lights – Some birds are attracted to the lights on aircraft.
- Weather – Poor weather like fog increases risk since birds cannot see aircraft as well.
In addition to external factors, the design and operation of aircraft can influence the likelihood of bird strikes. Slower aircraft with multiple engines like the Airbus 380 are better able to withstand bird impacts compared to smaller fast moving jets.
Do window designs affect bird strike risk?
The windows on an aircraft help determine how visible it is to birds. Windows account for over 40% of the exterior surface on most planes. The size, shape, number, and exterior coating of windows all influence how detectable and attractive an aircraft appears to birds.
Research conducted by the United States Air Force shows that the more windows an airplane has, the more likely it is to suffer bird strikes. Jets with many windows like the Boeing 737 and the Airbus 320 family have higher rates of bird collisions compared to planes with fewer windows like military transport aircraft.
The exterior color and markings on airplane windows also affect the risk of bird strikes. Contrasting bands or patterns on windows help birds distinguish the aircraft and avoid colliding with it. This is why most airliners have dark paint around their passenger windows.
Bird strike rates by aircraft type
| Aircraft | Bird Strikes per 10,000 flights |
|---|---|
| Boeing 737 | 3.99 |
| Airbus 320 | 3.64 |
| Boeing 747 | 1.75 |
| Boeing 757 | 1.64 |
| Boeing 777 | 1.09 |
How do dirty windows affect bird strike risk?
Dirty windows can potentially increase the likelihood of bird strikes. Grime, dirt, and other accumulations on the exterior of airplane windows may make them less visible to birds. If the windows blend into the fuselage due to surface contaminants, their ability to help birds distinguish and avoid the aircraft could be diminished.
That said, there is limited research specifically analyzing the effect of dirty airplane windows on bird collision rates. Most aviation studies focus on window size, location, and contrast rather than the cleanliness of window surfaces. Nonetheless, general principles would suggest dirty windows could potentially be more hazardous than clean windows.
What do aviation regulators say about dirty airplane windows?
Aviation regulators emphasize the importance of maintaining clean, clear windows in order to maximize external visibility for pilots. Dirty windows are primarily a safety concern due to reduced cockpit visibility rather than increased bird strike risk per se.
The Federal Aviation Administration (FAA) mandates that operators must clean and polish windows on a regular basis. For air carriers, window cleaning procedures are stipulated in their FAA approved maintenance programs. Aircraft maintenance manuals provide detailed procedures for proper window cleaning and inspection.
While dirty windows are not expressly linked to higher bird strike risk in regulatory guidelines, the FAA nonetheless considers clear, clean windows an important safety practice. From a safety philosophy standpoint, dirty windows on any part of an aircraft should be avoided even in the absence of strict rules.
What do airlines and airports do to prevent bird strikes?
Airlines and airports use a variety of strategies to reduce the risk of bird strikes. These include:
- Aircraft design features – Engines mounted higher on wings, windshield sprayers, wing pulse lights to warn birds, etc.
- Airport habitat management – Eliminating ponds, removing trees, and keeping grass short to dissuade birds.
- Noise and visual deterrents – Cannons, distress calls, fireworks, remote control falcons, lasers, and effigies to scare birds away.
- Radar and bird detection systems – Tracking bird movements in real-time to avoid hotspots.
Keeping aircraft exteriors clean is not specifically mentioned in most bird strike prevention programs. Nonetheless, general safety practices would suggest that windows and other surfaces be kept clean whenever possible as an additional precaution.
Conclusion
Evidence directly linking dirty airplane windows to increased bird strike rates is limited. However, general safety principles suggest keeping windows clean and clear to maximize exterior visibility, for birds and pilots alike. As such, regular window washing as part of standard maintenance procedures is a prudent precaution against bird strikes.
In addition to clean windows, comprehensive airport bird management plans, aircraft design features, radar tracking, and active deterrents can help mitigate the substantial risks and costs associated with bird strikes. Further research quantifying the specific impact of window cleanliness may provide airlines and regulators data to refine maintenance requirements to enhance safety.
