Bird strikes are a serious aviation hazard and can cause severe damage to aircraft. This article will examine what happens when a bird collides with an airplane windshield and the potential consequences.
What is a bird strike?
A bird strike occurs when a bird collides with an aircraft. This usually happens during takeoff or landing phases of flight when planes are flying at low altitudes. Aircraft most often collide with birds near airports, over land, or along migratory routes.
The Federal Aviation Administration (FAA) defines a bird strike as:
“A bird strike is strictly defined as a collision between a bird and an aircraft which is in flight or on a take off or landing roll.”
How common are bird strikes?
Bird strikes are quite common. According to statistics from the FAA, there were 13,408 reported civil aviation bird strikes in the United States in 2019. However, the FAA estimates that the actual number is likely 2-3 times higher than what is reported.
Globally, it is estimated that bird strikes cost the aviation industry over $1.2 billion per year and damage over 40 civil aircraft every day. Most bird strikes cause little to no damage, but collisions at higher speeds or with larger bird species can cause severe problems.
What types of birds cause the most strikes?
Not all birds pose equal risk. Larger birds like geese, ducks, gulls, raptors, pelicans, swans, and turkeys are involved in the majority of damaging strikes. Their size, flocking behavior, and populations near airports increase the chance of a collision.
| Bird type | Percentage of reported bird strikes in US |
|---|---|
| Gulls | 27% |
| Sparrows | 9.5% |
| Blackbirds/starlings | 6.1% |
| Geese | 4.3% |
Small birds like sparrows rarely cause damage. However, striking even a small flock can badly damage an aircraft.
Why are waterfowl especially hazardous?
Birds that live near water, like geese and gulls, present a high risk of strikes. Features that make them hazardous include:
– Large size – geese weigh 8-20 pounds on average
– Flocking behavior – groups of birds magnify the impact
– Congregate near airports – open spaces near water attract birds
– Migrate through airport flight zones
– High populations – many species have adapted well to urban areas
What parts of aircraft are most affected by bird strikes?
Most reported bird strikes – 65% – impact the airframe of the aircraft. The engines are the second most commonly struck component at 15% of incidents. Other affected areas include the wings, nose, landing gear, tail, and cockpit windows.
The highest risk areas are the engines, windshield, and sensitive flight control surfaces like the wings and tail. Damage to these areas can potentially lead to loss of control or power.
Can windshields withstand bird impacts?
Modern aircraft windshields are engineered to withstand bird strikes at high speeds. They are composed of multiple layers of reinforced, tempered glass and stretched acrylic. This creates a resilient barrier that can resist the tremendous forces involved.
However, there are limits. Extremely high energy impacts from larger birds or flocks can potentially penetrate the windshield, especially near the edges or if prior damage exists. Cockpit windows represent 5-10% of reported bird strikes. Most of these events result in little to no damage. But serious collisions can heavily damage or shatter the windows.
Windshield testing standards
Aircraft windshields must meet stringent standards to receive certification from aviation regulatory agencies like the FAA. For example, Federal Aviation Regulation (FAR) 25.775 sets strength requirements for windshields. It states:
“The windshield panels in front of the pilots must withstand, without penetration, the impact of a four-pound bird strik- ing at a relative velocity of 100 knots.”
Manufacturers use gas cannons or impact testing machines to fire dead chickens and other medium sized birds at cockpit mockups. This simulates striking a four pound bird at aircraft speeds up to 115 mph as required.
What happens when a bird hits a windshield?
Now let’s look at the effects when a bird collides with an airplane windshield in flight:
Physics of a bird strike
Bird strikes involve tremendous forces. Kinetic energy increases exponentially with velocity. A small 1 lb bird striking at 250 knots impact force equals:
- 250 knot airspeed = 288 mph groundspeed
- Bird relative velocity = 288 mph
- Kinetic energy = 1/2 x Mass x Velocity2
- = 0.5 x 1 lb x (288 mph)2
- = 120,960 ft-lbs force
That is equivalent to the energy required for a Ford F-150 truck weighing over 5 tons! Now imagine the impact of a 10 lb goose colliding at 300 knots. This generates almost 7.2 million ft-lbs of force. The windshield absorbs this energy through elastic deformation and fracture.
Damage severity
Actual damage depends on:
- Bird size and density – kinetic energy increases with mass
- Speed – energy is proportional airspeed squared
- Angle of impact – perpendicular is worst case
- Windshield thickness – newer designs are more resistant
- Prior defects – cracks or flaws concentrate stress
Minor strikes lead to small cracks or surface erosion. But major impacts can cause extensive splintering, spiderwebs of fissures, holes, and even full penetration or shattering of the windshield.
Windshield failure modes
There are a few typical failure patterns when the impact energy exceeds windshield strength:
Outer ply fracture
The initial impact usually breaks the outer glass layer first. This dissipates some energy and helps prevent penetration.
Partial penetration
If the bird or debris punches into the outer glass, but does not fully penetrate, this creates a partial hole or recess. Fractures may radiate out from the impact point.
Full penetration
With enough force, the object can completely puncture through the full windshield. This creates an open hole allowing air pressure into the cockpit.
Shattering
In severe cases, the entire windshield can instantly shatter into tiny fragments. This usually results from a very powerful direct impact.
What are the risks from a damaged windshield?
A damaged windshield significantly degrades safety for the flight crew and aircraft, especially if penetration occurs. Major hazards include:
1. Structural failure
Holes or cracks can compromise the integrity of the surrounding window frame. In the worst case, catastrophic windshield failure leads to explosive decompression.
2. Loss of visibility
Cracks obstruct and distort vision, especially if filled with blood. This impairs the crew’s ability to see instruments, avoid terrain, and land safely.
3. Incapacitation of pilots
Penetration can seriously injure crew in the cockpit. Damage to controls and avionics can also hinder aircraft operability.
4. Cabin depressurization
If an opening exceeds a certain size, the cockpit can partially lose pressurization leading to hypoxia.
5. Aerodynamic disturbance
Large holes disturb airflow over the fuselage potentially causing control difficulties.
Historical examples of serious bird strike incidents
There are many examples of catastrophic bird strikes to underscore this hazard:
US Airways Flight 1549 “Miracle on the Hudson”
On January 15, 2009, US Airways Flight 1549 struck a flock of geese shortly after takeoff from New York’s LaGuardia Airport. The multiple impacts took out both engines. With no power, Captain Chesley Sullenberger famously ditched the plane into the Hudson River. All 155 passengers and crew survived the emergency landing.
Analysis found evidence of geese remains embedded in the windscreens and dents along the right copilot window. But the multi-layer glass contained the strikes and protected the occupants.
Ryanair Flight 4102
In June 2011, a Ryanair Boeing 737-800 was climbing through 2,000 feet after departing Rome Ciampino Airport when a seagull smashed into the left cockpit window.
The inner glass layer held, but the outer pane completely shattered exposing the flight deck. The crew could feel wind blasting into the cockpit. They diverted to a lower altitude and returned safely to Rome with no injuries.
DAP Airlines Flight 2351
In March 2022, a DAP Airlines DHC-8-100taking off from Mbuji-Mayi, Congo flew through a flock of swallows at rotation. Several birds penetrated the copilot’s windshield and seriously injured the first officer. Due to the loss of visibility from bird remains, the captain had to land relying on instruments alone while also attending to his copilot. There were no other injuries.
How can windshield bird strikes be prevented?
Because bird strikes remain an unavoidable hazard in aviation, the best strategy is reducing risk through multiple methods:
Aircraft design
– Windshields optimized for birdstrike resistance using advanced materials
– Redundant engine designs less prone to dual failure
– Protected position of critical flight systems
Airport precautions
– Perimeter fences to deter wildlife
– Active bird deterrents like propane cannons, predator decoys, pyrotechnics
– Vegetation management and drainage to reduce bird habitats
– Radar tracking of flocks near runways
Flight crew procedures
– Briefings emphasizing bird strike risks
– Climb rate guidance when birds observed
– Caution when flying through migration corridors
– Immediate declaration of emergency if strike occurs
– Simulation training for engine out emergencies
Conclusion
Bird strikes pose a serious threat, especially to critical aircraft structures like windshields. Collisions at high speeds can transfer enormous forces onto the windows. While modern windshields are engineered to withstand strikes, extremely high energy impacts or prior damage may lead to catastrophic failure. To mitigate risks, aviation agencies, airports, and airlines have implemented standards, habitat modification, aircraft improvements, avoidance procedures, and crew training. However, eliminating all bird strikes remains impossible. This hazard will continue to require effective risk management and crashworthiness design to ensure flight safety.
