Bird strikes are a major concern for the aviation industry. These collisions between birds and aircraft can cause severe damage, especially to engines. But do bird strikes always destroy jet engines? Let’s take a closer look at the effects of bird strikes on engines.
What happens when birds hit jet engines?
Jet engines operate by sucking in large volumes of air. This airflow is compressed and ignited to generate thrust. So when birds get sucked into engines, the results can be catastrophic. At high speeds, birds become dangerous projectiles. Strikes can bend fan blades, damage compressor blades, and leave dents or holes in critical components.
Engine failure is possible, but not guaranteed. Modern jet engines are designed to withstand and contain some bird strikes. Factors like the bird’s size, speed, and where it hits the engine determine the amount of damage. Small birds like sparrows may cause minimal harm. But large birds like geese can wreak havoc inside engines.
How much damage do bird strikes cause?
According to estimates, bird strikes cause $1.2 billion in damage worldwide each year. Around 5% of strikes result in substantial damage. The most vulnerable parts of engines include:
- Fan blades – spinning blades at the engine inlet ingest birds directly into the engine core.
- Compressor blades – spinning blades further inside the engine compress air. Distorted blades reduce compression efficiency.
- Combustion chamber – bird remains can block fuel nozzles and prevent proper ignition.
- Turbine blades – overheated or warped blades inside the turbine section impair energy extraction.
Even small amounts of damage can require extensive engine repairs or full replacement. Lost thrust from one damaged engine can also compromise the flight.
Are some aircraft more vulnerable than others?
Engine size and design affect vulnerability. The largest engines on widebody jets ingest the most birds per mile traveled. Their fans and internal components also suffer more kinetic damage per strike. Regional jets have smaller engines, so they’re less prone to catastrophic damage from single bird strikes. Turboprop aircraft are even less susceptible due to lower speeds and smaller air intakes.
Many factors influence the risk of bird strike damage:
- Engine diameter – larger fans increase the ingestion area.
- Engine location – underwing engines are more exposed than fuselage mounts.
- Intake design – some improve visibility and allow birds to bypass vital components.
- Number of engines – aircraft with multiple engines have redundancy if one fails.
Modern turbofans with higher bypass ratios are also more resilient. Bypass airflow dilutes ingested bird remains in the core. So engines with higher bypass ratios, like those on the Boeing 787 and Airbus A350, suffer less damage on average.
What are the most damaging bird strike incidents?
While most bird strikes cause little or no damage, some have resulted in catastrophic engine failure:
- US Airways Flight 1549 (2009) – Captain Sully Sullenberger glided the Airbus A320 to a safe landing in the Hudson River after geese took out both engines shortly after takeoff from New York’s LaGuardia Airport.
- Ryanair Flight 4102 (2008) – A flock of starlings during takeoff from Rome destroyed the engines on this Boeing 737. The captain landed the plane safely after declaring an emergency.
- Delta Flight 1889 (1996) – After striking geese over the Caribbean Sea, this Boeing 757 lost power in both engines. The crew performed a deadstick landing in the Azores Islands.
On average, double engine failures occur in only one or two accidents per year. Modern jetliner designs and pilot training help minimize catastrophic damage from even large bird strikes.
What prevents bird strikes from destroying engines?
Aircraft manufacturers implement both design features and operational guidelines to reduce catastrophic bird strike damage:
- Impact-resistant fan blades – Blades made of advanced alloys like titanium can withstand more bird collisions before warping or fracturing.
- Cowl separation lines – These frangible panels blow out to provide an alternate escape path for bird remains.
- Intake geometry – Angled edges make inlet surfaces more visible to birds.
- Disk shields – Metal deflector shields protect internal compressor and turbine disks.
- Engine placement – Underwing mounting puts more space between engines.
- Airport bird control – Habitat management, active hazing, and other methods reduce wildlife collisions near runways.
- Avoidance procedures – Climbing and descending at the greatest possible angle reduces time at lower altitudes where bird strikes are more likely.
Design features concentrate damage in less critical areas and prevent engine failures. Airport wildlife management and flight procedures further reduce the risks. As a result, very few bird strikes result in the complete loss of even a single engine.
How much damage can engines withstand?
The Federal Aviation Administration (FAA) requires engines withstand the following without catching fire or losing thrust:
- 1.15 pounds bird at cruise speed
- 4 pound bird during takeoff
- 8 pound bird when idling
These requirements ensure engines can tolerate most bird strikes without failure. Only about 10% of strikes exceed 4 pounds. The FAA uses chicken cannons to test new engine designs by firing dead chickens into spinning fans and compressor stages.
Manufacturers perform additional internal tests. For example, GE tests its newest GEnx engines by firing 15 pound geese at over 500 mph. This simulates strikes from even the largest birds at higher takeoff speeds. Such rigorous testing demonstrates engine resiliency.
Do bird ingestions always damage engines?
No, not every bird ingestion causes engine damage. Small bird strikes may leave no evidence behind. Engines can fully withstand the impact of many small birds up to 2 pounds. Even low-density birds like seagulls don’t always harm engines if the strike location and quantities are limited.
Here are some examples of inconsequential bird ingestions:
- Single small birds hitting the fan without leaving dents or bent blades
- Songbirds passing fully through engine cores
- Seagulls partially ingested but missing key components
- Medium birds partially deflected by the inlet guide vanes upon ingestion
These minor strikes may not affect engine operation at all. The most problematic strikes involve flocks of large, dense birds head-on into the core. Even then, redundant engines prevent a catastrophe.
Do bird strikes ever cause crashes?
While damaging, modern bird strikes rarely result in crashes. Redundant engines prevent loss of power. Plus, pilots train extensively for emergency landings following bird strikes. However, problems can still arise after major engine damage from bird strikes, including:
- Complete loss of thrust – For twinjets, loss of both engines can leave no engine power.
- Engine fire – Ruptured fuel lines or damaged cases can ignite spilled fuel or oil.
- Structural failure – If debris ruptures a fuel tank, control lines, or flight surfaces.
- Asymmetric thrust – Uneven power from damaged engines makes control difficult.
Crashes directly tied to bird strikes are infrequent today. When they do occur, it often involves inadequate pilot response or multiple system failures after major engine damage.
| Year | Airline | Aircraft | Cause |
|---|---|---|---|
| 1995 | Awair Airlines | BAe ATP | Dual engine failure from goose strike after takeoff |
| 1996 | Himax Airlines | Antonov 24 | Engine fire following swallow strike on takeoff |
| 2012 | DHC-6 Twin Otter | Cessna 208 | Loss of control due to goose strikes on both engines |
Better engines and pilot training now minimize aviation accidents from bird strikes. But they remain an ever-present threat to flight safety.
Conclusion
Bird strikes clearly can destroy jet engines under the right conditions. Direct hits from flocks of large birds have caused engine failures. However, modern turbofans are incredibly resilient. Smart designs and rigorous certification standards enable engines to withstand most bird collisions without failure. Improved airport wildlife management and flight crew training further reduce the risks. So while complete engine destruction from bird strikes is possible, it is now exceedingly rare thanks to continuing safety improvements.
