Bird-strike events are relatively common, occur most often on the ground or at low altitude, and are usually benign. However, bird strikes can have significant economic and occasional safety consequences for flight operations. Pilots and operators should be knowledgeable about the hazard, and flight crews should use facts, data, and standard operating procedures to reduce the potential for and consequences of a bird strike.
Flight crews can reduce the possibility and effects of a bird strike
by increased awareness and by following recommended procedures.
Bird strikes are a lesser hazard to aviation than other well-known
hazards such as loss of control in flight, controlled flight into
terrain, and runway excursions, but they can and do present risk that
needs to be addressed. The first bird strike was recorded by the Wright
brothers in 1905, and the aviation wildlife hazard has been a risk to
aviation ever since. The January 15, 2009, ditching of US Airways flight
1549 on the Hudson River in Weehawken, New Jersey, was the dramatic
result of dual engine thrust loss arising from an airborne encounter
with a flock of Canada geese. Although Boeing airplanes meet and exceed
the government regulations for bird strikes, accidents and serious
incidents can occur. Aviation wildlife hazards encompass birds on the
ground and in flight, terrestrial animals (e.g., deer, coyotes, cattle,
camels), and even airborne animals such as fruit bats; however, this
article focuses on bird strikes in particular. Operators and flight
crews should be aware of the risk of bird strikes, prevention
strategies, and actions to take following a bird strike.
This article discusses the characteristics of bird strikes, presents
practical information for flight crews, highlights the importance of
reporting bird strikes, and provides resources for additional
bird-strike information. Characteristics of bird strikes
According to Bird Strike Committee USA, an organization that was
formed in 1991 to facilitate the exchange of information and promote the
collection and analysis of accurate wildlife strike data, bird and
other wildlife strikes cause more than $650 million in damage to U.S.
civil and military aviation annually. In addition, bird strikes put the
lives of crew members and passengers at risk — more than 200 people have
been killed worldwide as a result of wildlife strikes since 1988. The
Bird Strike Committee takes a similar data-driven approach to the bird
strike issue that organizations such as the Commercial Aviation Safety
Team (CAST) takes to reduce commercial aviation fatality risk. (See www.cast-safety.org.)
Experts within the U.S. Federal Aviation Administration (FAA), the
U.S. Department of Agriculture, and the U.S. Navy and U.S. Air Force
expect the risk, frequency, and potential severity of wildlife-aircraft
collisions to grow over the next decade, based on increasing air
traffic, bird populations, and the trend to twin-engine aircraft. (Download PDF.)
While bird strikes usually inflict most damage on the engines, all
areas of an airplane can be damaged (see figs. 1 and 2). Airplane damage
and effect on flight from bird strikes are closely correlated to
kinetic energy, derived from the mass (determined by bird species) and
the square of the speed of the collision. (A 20 percent increase in
speed raises the kinetic energy by 44 percent.)
Figure 1: Example of bird-strike damage
Bird-strike damage can be quite severe and can shut down jet engines.
Figure 2: Locations of bird-strike damage
Three-quarters of bird strikes involve the wing or engines, but they can damage almost any part of an airplane.
Single or multiple large birds, relatively small numbers of
medium-size birds, and large flocks of relatively small birds are all
problematic and have resulted in accidents. In the United States, a list
of birds most hazardous to flight has been identified: large flocking
waterfowl (Canada goose); gulls; pigeons and doves; blackbirds,
starlings, and sparrows; and raptors (hawks and kestrels). Most bird
strikes occur on or near the ground, highlighting the need for wildlife
management on airport grounds and in the vicinity. (Download PDF.)
The aviation bird-strike hazard is a global and industrywide issue
affecting all aviation stakeholders, including pilots, mechanics,
airlines, airport operators, air traffic controllers, wildlife
personnel, aviation safety analysts, airplane and engine manufacturers,
flight training organizations, and the traveling public. Boeing
participates in national and international groups dedicated to exploring
and addressing the problem of bird strikes, and Boeing airplanes meet
and exceed regulatory bird-strike requirements. Boeing has many design
features, including system separation, system redundancy, and structural
attributes, to protect against bird strikes beyond the four-pound
regulatory general bird-strike FAA requirement (eight pounds for
empennage).
Common misconceptions about bird strikes
A number of widespread misconceptions about bird strikes may give
pilots a false sense of security and prevent them from reacting
appropriately to the threat of a bird strike or an actual event. These
misconceptions include:
- Birds don’t fly at night.
- Birds don’t fly in poor visibility, such as in clouds, fog, rain, or snow.
- Birds can detect airplane landing lights and weather radar and avoid the airplane.
- Airplane colors and jet engine spinner markings help to repel birds.
- Birds seek to avoid airplanes because of aerodynamic and engine noise.
- Birds dive to avoid an approaching airplane.
In fact, none of these statements is scientifically proven.
Preventive Strategies
Airports are responsible for bird control and should provide adequate
wildlife control measures. If large birds or flocks of birds are
reported or observed near the runway, the flight crew should consider:
- Delaying the takeoff or landing when fuel permits. Advise the tower and wait for airport action before continuing.
- Take off or land on another runway that is free of bird activity, if available.
To prevent or reduce the consequences of a bird strike, the flight crew should:
- Discuss bird strikes during takeoff and approach briefings when operating at airports with known or suspected bird activity.
- Be extremely vigilant if birds are reported on final approach. If birds are expected on final approach, plan additional landing distance to account for the possibility of no thrust reverser use if a bird strike occurs.
Additional Resources
Additional information is available online through a number of
industry groups. Information includes significant strike events, key
issues to reduce strikes, risk assessment, system information, papers
and newsletters, and discussion forums.
- Bird Strike Committee USA.
- International Bird Strike Committee.
- International Civil Aviation Organization (ICAO).
- Embry-Riddle Aeronautical University.
- National Bird Strike Committees or Aviation Wildlife Hazard Groups.
The importance of reporting bird strikes
Flight crews and maintenance and line personnel are encouraged to
report all bird strikes because data are essential to quantify and
manage the hazard. Reporting bird strikes enables aviation authorities
to monitor the risk to aviation and the effectiveness of wildlife hazard
mitigation measures. Bird-strike data, together with knowledge of the
operational environment, are utilized by Boeing as a basis of many
airplane design features beyond regulatory requirements. Bird-strike
data also help researchers understand the nature of strikes and develop a
scientific approach to reduce the cost and safety consequences of bird
strikes.
Aviation stakeholders should report all known or suspected bird
strikes to their national or recognized wildlife strike data repository
(e.g., the FAA National Wildlife Strike Database in the United States)
and share the strike information with the airport operator, the airline
safety department, and the aircraft and engine manufacturers. Each of
these individual reports will be combined into a single composite data
record. Reporters should provide as much information as possible,
including:
- Airplane model and series designation (e.g., 777-300).
- Airplane serial number or registration.
- Phase of flight.
- Speed and altitude of the airplane.
- Geographical location of the airplane.
- Date and time of day.
- Origin and destination airport.
- Number and species of bird observed and struck.
- Impact locations of strikes and damage on airplane.
- Effect on flight (e.g., rejected takeoff, air turnback, diversion).
If bird remains are available, trained personnel should identify the
species involved, or the bird remains should be collected using the
correct procedure (as outlined here)
and bird-strike collection kit and shipped to a qualified laboratory.
It is crucial to determine the species of the bird or birds involved in a
bird strike and the location of the strike, so that wildlife management
can take appropriate actions. Effective wildlife management involves
controlling attractants, often species-specific, including food,
foraging, roosting, and nesting opportunities. Managing the environment
may be necessary, even to the extent of grass type and height, insects,
rodents, and invertebrates, along with water sources and land use, such
as agriculture.
In the event of a bird strike, maintenance personnel should follow
the appropriate maintenance procedures for bird strike inspection in the
Airplane Maintenance Manual. Maintenance personnel must be cognizant of
the possibility that the bird remains can contain infectious material.
The bird strike should be reported by the flight crew in the pilot’s log
or by the maintenance crew in the maintenance log. After a bird strike,
the airplane should be inspected for possible damage to airplane
structure and airplane systems.
In the United States and Canada, bird-strike information can be reported online or via FAA form 5200-7 Bird/Other Wildlife Strike Report.
How airlines can get involved
Airlines and other stakeholders can help address the ongoing problem
of bird strikes by participating in local, regional, national, or
international aviation wildlife hazard activities, such as bird-strike
committees or equivalent groups.
Airlines can also form their own internal aviation wildlife hazard
group and designate a single point of contact for coordinating all
aviation wildlife hazard activity, both internally and externally.
Summary
Bird strikes have always been a part of aviation. While they usually
cause no more than minor damage, they can pose a threat to air safety.
By being aware of the ongoing possibility of bird strikes and by
following recommended procedures, flight crews can reduce the
possibility and effects of a bird strike.