Bird Strike
Doesn't Mean No Baseball in Baltimore

Air Line Pilot, February 2000, page 29
By Jan W. Steenblik, Technical Editor

ALPA and the NTSB want more action to reverse the growing safety threat of wildlife collisions with airplanes.

Birds' bones and the quills of their feathers are hollow. Some birds weigh mere ounces. So how can they pose a lethal threat to aviation?

Perhaps you've had this experience: You're sitting at home or in an office when suddenly a dull thump rattles a window or glass door. You look up and see a sparrow--a mottled brown fluffball--lying on the ground outside. No damage to the window, but wasn't that an impressive thump for a few ounces of songbird?

Now recall your introductory physics course: Kinetic energy equals one-half times mass times velocity squared. In other words, kinetic energy is directly proportional to the mass involved, and directly proportional to the square of the velocity. Double the mass of the object, you double the kinetic energy; double the velocity, you quadruple the kinetic energy.

Colliding at 130 knots, a 4-pound bird (for example, an adult great black-backed gull) hits an aircraft with more than 2 tons of force, concentrated in a small area. At 260 knots, the same bird delivers a 9-ton punch.

Just ask Capt. Bruce Harris, First Officer Bryant Hebner, Second Officer Mark Jansky, and Line Check Second Officer Paul Gruver, the flight crew of Delta Air Lines Flight 1783, which departed Houston Intercontinental Airport (IAH) on Jan. 9, 1998. Climbing at 280 KIAS to comply with an air traffic controller's request to participate in the "no airspeed restriction" test the FAA has been conducting at IAH, the Boeing 727-200 struck a flock of snow geese--birds that can weigh 7 pounds apiece--at 6,000 feet.

The flight crew instantly found themselves in an airplane that was vibrating intensely and had lost all power in one of its three engines. F/O Hebner's cockpit instruments had failed, and the noise in the cockpit was deafening. The crew worked as a team to return the crippled airplane to IAH without injuries to themselves or their passengers. Their outstanding performance earned them the ALPA Superior Airmanship Award (see "ALPA Annual Air Safety Awards Banquet," September 1999).

Post-flight inspection confirmed that the bird strikes had extensively damaged the B-727; the radome was destroyed, the left and center engines had to be replaced, and the right wing and other parts of the airplane were badly damaged.

The pilots were highly skilled, and they and their passengers were lucky.

Fatal risk

Several fatal strikes between aircraft and wildlife have killed at least 68 people in the United States and Europe since 1995. Approximately 2,300 non-fatal wildlife strikes involving civil aircraft are reported annually in the United States; experts in the field estimate that 80 percent of strikes are not reported.

FAA Administrator Jane Garvey has said wildlife strikes cost the U.S. civil aviation industry more than US$327 million and more than 500,000 hours of downtime each year. Canadian authorities estimate the total annual cost (direct and indirect) of bird strike damage to the U.S. and Canadian aviation industry, including military and general aviation, to exceed US$500 million. Northwest Airlines alone suffered US$24 million in engine damage at one airport (Detroit) during a 4-month period in late 1999.

Bird strikes have caused hull losses of airplanes as large as a DC-10 (Overseas National Airways, New York, 1975) and a U.S. Air Force AWACS E-3, a military version of the B-707 (Elmendorf Air Force Base, Alaska, 1995). Multiple Canada goose strikes almost brought down a USAF C-5A Galaxy, one of the largest airplanes in the world, shortly after takeoff from Dover (Del.) AFB in 1983.

Aviation safety consultant Dr. Todd Curtis, limiting his analysis to large jet transports, concludes that the chance of another fatal air carrier accident caused by bird strikes during the period 1998–2008 to be 26 percent.

Exploding populations

One of the reasons for the increase in wildlife collisions with aircraft is that many wildlife species, a century after falling to record lows (in some cases, near extinction) from market hunting and other factors, have rebounded spectacularly.

The U.S. Department of Agriculture notes significant growth in bird populations during the last 10–20 years, including the following examples:

* The resident Canada goose population has tripled in the last decade. More than 5 million of these large birds now live in the United States.

* The Great Lakes cormorant, a 4-pound bird, multiplied by a factor of 900 between 1970 and 1997 because of improvements that were made in the specie's environment.

* The white pelican, a 25-pound bird, has reached a population of almost 1 million, which grows by 3.1 percent every year.

* The snow goose population is so large that it is destroying its Canadian nesting habitat.

* Gulls in the Great Lakes region are now so numerous that they have run out of nesting areas and are forced to take over rooftops as nesting sites.

Similarly, game biologists believe that white-tailed deer--very adaptable to living around humans--now equal or exceed their number in North America before European settlers first set foot on these shores. Population estimates run upward of 25 million deer.

Different approaches

Two basic approaches have been taken to reduce wildlife hazards to aviation--(1) trying to make aircraft more resistant to bird strikes by setting appropriate certification standards for windshields and jet engines, and (2) reducing the frequency of wildlife collisions by controlling wildlife on and near airports.

Regarding the latter approach, says Capt. Paul Eschenfelder (Northwest), ALPA's Wildlife Hazards Project Team Leader, "wildlife strikes have been reduced significantly at certain locations. For example, at John F. Kennedy International Airport in New York, gull strikes have been reduced by more than 75 percent. At Chicago O'Hare, bird and deer strikes have been reduced by 70 and 100 percent, respectively."

However, he warns, "many airports have ongoing wildlife problems that have not been addressed in such a proactive manner."

A good sampling of the efforts that are being made to understand and control wildlife hazards was available at a 5-day conference held in May 1999 near Vancouver International Airport (YVR) in Canada. More than 300 delegates and guests from 23 countries attended the conference, which was the first joint meeting of Bird Strike Committee USA and Bird Strike Committee Canada.

Capt. Eschenfelder, Capt. Jack Wilkes (Alaska), director of ALPA's Airport Liaison Representative program, and Capt. Bob Perkins (Air Ontario), ALPA's Canada Board Air Safety Chairman, attended the conference. Capt. Perkins represented ALPA on the International Bird Strike Committee, which also met during the Vancouver conference.

BirdStrikePic1.jpg (147353 bytes)
Capt. Jack Wilkes (standing) and Capt. Paul Eschenfelder (seated, wearing cap) talk with a representative of BirdAvert, a modified maritime radar that detects birds on an airport and triggers stationary electronic "falcons" to flap and scream to scare the birds.

Capt. Perkins serves on Bird Strike Committee Canada, and Capt. Eschenfelder, on Bird Strike Committee USA.

The conference covered reports on basically two areas--(1) basic research on wildlife behavior and populations, and (2) efforts to manage specific wildlife populations on (and near) specific airports.

For example, Dr. Tom Kelly of University College, Cork (Ireland), described his preliminary study of evasive maneuvers that birds flew while trying to cross an air carrier runway at Dublin. Intriguing stuff, but so far, nothing concrete a flight crew--or airport personnel--could use to prevent a strike.

Similarly, studies of soaring birds in locations as diverse as Israel and Utah suggest that not only intensive tracking of birds by human spotters and radar but also atmospheric models may serve useful in keeping track of birds' locations.

A field trip took conference attendees to a wildlife refuge on the north side of YVR that made possible the building of a second east-west runway on the north side of the airport by reducing birds' interest in the airport. On the airport, vendors showed off the latest in high- and low-tech airport bird control technology--among them, trained border collies, wind-powered electronic distress calls, shotgun cracker shells, falconry, and floating nets to cover airport ponds.

A "nasty little secret"

Capt. Eschenfelder presented ALPA's perspective on wildlife hazards to aviation, with particular emphasis on what he calls "the nasty little secret" of this important safety issue--i.e., the inadequacy of the FAA's current bird-ingestion test requirements for jet engines.

In 1998, the FAA published a notice of proposed rulemaking (NPRM) that, if made a final rule, would modify the standards to which jet engines are certified with respect to their ability to withstand impacts from birds or similar wildlife hazards. ALPA responded in March 1999 that the Association could lend only qualified support to the NPRM.

"We feel the proposed standard is a step in the right direction," ALPA said, "but cannot under any circumstances be considered attainment of a goal."

The existing--and proposed--certification requirements for bird ingestion include tests for ingesting specified numbers of small, medium, and large birds.

"The NPRM does not address, nor does it make provision for, bird population growth or an increase in aviation operations," ALPA pointed out. "The certification standard should include a formula for increasing engine strength as bird populations and aircraft operations (and therefore risk of ingestion) increase."

The NPRM assumes "that current standards for airport certification will be maintained, that the historical environment will not worsen, and that airport operators and pilots will maintain at least their current awareness of the bird-ingestion threat." ALPA said, "We feel none of these assumptions can be considered completely valid."

In fact, ALPA told the FAA, "the data used in developing the NPRM have been superceded by more accurate values for bird weight, flock size, and risk of encounter. These more accurate data, and the reality of ever-increasing bird populations, must be part of a program to continuously reevaluate and adjust airworthiness standards.

"Airport programs are decreasing, and formal pilot training in wildlife hazards is nonexistent. Such deficiencies must be corrected," ALPA said.

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Capt. Bob Perkins (second from left) represents ALPA during a meeting of the International Bird Strike Committee held in May 1999 in Vancouver, B.C., in conjunction with the first joint meeting of Bird Strike Committee USA and Bird Strike Committee Canada.

Expanding on the issue of bird strike data, ALPA said, "Recent birdstrike incidents (e.g., an American MD-80 that left 430 dead starlings on the runway and a US Airways B-737 that left more than 200 dead gulls on the runway) suggest the presumed flock sizes used to develop the NPRM may be unrealistically low." The Association added that 1998 radar analysis conducted in England "clearly shows that, for a 100-inch engine, expected bird-ingestion numbers are for starlings, 9; for rock doves [pigeons], 11; for gulls, 4; for Canada geese, 3."

Speaking of Canada geese, the NPRM talks about flocking bird threats up to approximately 8-pound birds. However, based on current USDA data, the average resident (non-migratory) Canada goose today weighs 12 pounds, with the giant subspecies routinely weighing 15 pounds. Because bird weight is critical in testing engine resistance to bird impacts, these larger birds must be considered.

Another issue for ALPA in the NPRM involves the FAA's presumption about aircraft speeds. "To accommodate commuter and small business jets," ALPA said, "the [medium bird] test criteria were modified to reflect the fact that 250 KIAS was above the normal climb speeds for this class of aircraft. This is no longer true.

"The fastest growing segment of the airline industry is the regional jet," ALPA continued, pointing out that a number of regional jet types routinely operate at 240–250 KIAS below 10,000 feet. "Those speeds," ALPA declared, "are not performance-based, but are imposed either by ATC restriction or by windshield limitations for birdstrikes."

And, as discussed earlier, the same FAA has been conducting an operational evaluation of waiving the 250 KIAS speed limit below 10,000 feet at IAH. Controllers there encourage climb speeds between 320 and 340 KIAS.

"In spite of such incidents [as the Delta Flight 1783 multiple bird strike at IAH]," ALPA warned, "the [evaluation] program is slated to expand to Atlanta and Memphis and is being promoted as a capacity enhancement tool and an integral part of the [FAA's] Free Flight initiative."

Once again, the FAA continues to push a capacity initiative at the expense of safety.

As 2000 begins, both the IAH "no airspeed limit" program and the NPRM on tougher engine certification standards for bird ingestion remain open safety issues for ALPA.

The NTSB has recently published a list of recommendations aimed at reducing these risks to aviation (see "Pilot Report," page 37).

Flight crews now, however, are left with little else than to take seriously the "birds in vicinity of airport" statement on the ATIS--no matter how many times they've heard it--and to read and heed ALPA's recommendations for flight crew guidance (see page 30).

As a Transport Canada poster puts it, "an in-air collision between a goose and a jet can exert over 1.5 million foot-pounds of energy. An impact so strong, it is equivalent to a full-grown African elephant stampeding over a parked car."

That's one feathered Dumbo you don't want to hit.


Advice to Flight Crews Concerning Wildlife Hazards to Aircraft

By ALPA's Airport/Ground Environment Group

Before takeoff

* If you see wildlife on or near the runway, do not land or take off on that runway until the birds or animals are safely dispersed (delaying your landing or takeoff may delay you as much as if a thunderstorm were in your flight path). In the United States, the airport manager is responsible under FAR Part 139 for reducing wildlife hazards on the airport. Many other nations have similar regulations or requirements of airport management. The airport manager should have a plan of action with operations people who are trained to use proper techniques for dispersing wildlife and who are available to do so.

* Before departure, look for wildlife while scanning the runway for other hazards and respond to sightings or warnings of wildlife as you would to other aviation hazards. Remember that U.S. pilots are responsible under FAR Part 91 to "see what can be seen and separate [their] aircraft from obstructions and hazards, including birds" [Safeco Insurance v. City of Watertown; U.S. District Court, District of South Dakota, 1981].

* When you see wildlife hazards on the airport or in flight, promptly notify air traffic controllers, using the word "PIREP" in your report to ensure that controllers are aware that they should alert other pilots of the hazard, even though paragraph 2-1-22 of FAA Order 7110.65, the Air Traffic Controller's Handbook, requires controllers to issue advisories on reported bird activity, including type of birds, location, and direction of flight.

* Do not expect birds to respond to your efforts to hasten their departure. When loafing on the ground, birds face into the wind and, therefore, will probably not see your aircraft or its lights as the airplane enters the runway. Airborne weather radar has no demonstrated effect on birds because they do not hear in the X-band frequency. While birds have acute hearing, no evidence exists that they associate noise, such as a jet engine spooling up, with any threat. Do not expect, therefore, that engines spooling up will cause birds to take flight.

* When taking off in a string of departures, as is common at hub airports, be particularly cautious when birds and other wildlife are in the vicinity. The lead or second aircraft may frighten feeding or loafing birds into becoming airborne over the runway or departure area, making them a collision risk for following aircraft. This scenario was one of the causal factors in the crash of an E-3 (B-707) in Alaska in 1995. Birds may try to return to the spot on the airport from which they were frightened by going into a "holding pattern" over the airport to wait. Therefore, if the lead aircraft scares flocks of birds into flying, wait until the flock has cleared the area before taking off.

In flight

* More than 90 percent of all bird strikes happen below 2,300 feet AGL. If taking off in an area of high bird activity, climb as expeditiously as possible. If enroute and suddenly confronted with birds, pull up rapidly, consistent with good piloting technique. Birds, when facing a collision risk, tend to tuck their wings and dive away from the intruder. However, when birds are close to the ground, expect them to turn in random directions to avoid a collision but do not expect them to descend.

* Consider slowing down if confronted with bird activity. If a collision occurs, a slower speed may minimize the damage as the damaging force is directly proportional to mass times velocity squared. Slower closing speeds will give birds more time to react and avoid a collision.

* If wildlife is reported on or near the active runway, request another runway. Avoid flying over areas known to attract wildlife. Birds like bodies of water, such as airport retention ponds, lakes, and seashores. Consider requesting a different route if your assigned route carries you over or near bird activity.

Aircraft certification

* Although designed to be very strong in many ways, modern aircraft cannot protect pilots from all wildlife hazards. Birds have penetrated the fuselages of all modern airliner types, but the B-737 and B-727 appear most susceptible to bird penetrations, especially around the nose area. In 1997, three flight crew members were injured in three separate events when birds struck their cockpit windows. Although the windows were not penetrated, per se, the pilots were injured when the inner pane shattered and showered them with glass shards.

* The seriousness of an encounter with large birds, such as geese, swans, eagles, and vultures, cannot be overstated. Geese and swans are social animals and move in flocks. No jet engine is certified to ingest even one large bird and continue operating. However, smaller flocking birds, such as starlings, which have high body density and often flock by the hundreds or thousands, may have the same effect on aircraft engines. Engines are certified as a type, not as a system with a particular aircraft. If an aircraft encounters enough birds, they can damage engines to the point that the engines must either be shut down or continue operating but with less thrust available than is necessary to sustain flight.

Bird migration

* In North America, more than 300 million birds migrate every spring and fall. The four main migratory flyways--the Atlantic, Pacific, Mississippi, and Central--follow both coastlines, the Mississippi River, and the central plains east of the Rockies. Weather is the key to the start of migration--Nexrad radar can display thousands of flocks of birds headed south in the fall and paralleling strong cold fronts as they move across the country. Migrating birds often will wait on the ground for days for favorable winds aloft. During migration, waterfowl will fly both day and night, depending on weather and winds, and typically as high as 10,000 feet. This semi-annual migration creates additional hazards to aviation because migrating birds join resident airport birds and increase the likelihood of conflict with aircraft.

* Although spring and fall migrations create two peaks of extra risk, late summer brings another period of increased hazard as inexperienced fledglings begin flying and adult birds molt (shed their flight feathers), reducing their maneuverability.

Reporting wildlife hazards

* If you encounter wildlife hazards or strike birds or other wildlife in the United States, submit the appropriate company safety report and an FAA Form 5200-7 Bird Strike Report, in addition to a NASA ASRS report. A Canadian pilot should submit a wildlife strike report on the Transport Canada Bird/Wildlife Strike Report form, 51-0272 (6-97) or file a report on the website: www.; the toll-free number is 1-888-282-BIRD.

* You should submit these reports even if your airplane is not damaged because ALPA, NASA, the FAA, and other interested parties use the reports as the basis for documenting problems and for requesting action from appropriate authorities to mitigate wildlife hazards. Without the reports, ALPA and the other parties face a difficult or impossible task in trying to substantiate the need for improvements. n

ALPA Recommendations

ALPA has recommended that Congress, the FAA, and other U.S. agencies take the following actions to reduce wildlife hazards to aviation:

1. Congress authorize at least $450,000 per year for several years to reduce wildlife hazards to aviation and manage the FAA's wildlife strike database.

2. Congress authorize at least $600,000 per year for several years for the federal government to conduct wildlife surveys at airports.

3. Educate all pertinent members of the aviation industry and the U.S. government on this problem. Flight crew members should receive formal education on wildlife hazards during their annual recurrent training, along with guidance on how to reduce these hazards (see the sidebar, "Advice to Flight Crews," page 30). This training should be similar to FAA-mandated training on windshear, bomb threats, deicing, and other aviation hazards. Airport certification inspectors should receive formal training on plans for reducing the amount of wildlife so that airport inspections require evidence of an effective plan. Air traffic controllers should review, in their periodic training, FAA Order 7110.65, paragraph 2-1-22.

4. Immediately require reporting of wildlife strikes or hazards, such as is mandatory in most western European countries. Any party--pilot, mechanic, airport operations personnel, or air traffic controller--having evidence of wildlife hazards should report it. An FAA wildlife strike database and a reporting system already exist and can handle a greater rate of reporting. Although every air carrier has a safety department, which collects similar data, only two of them are reporting their strikes to the FAA.

5. All airport managements should immediately survey their airports to identify wildlife attractants on the airport. Federal funds should be made available to help minimize these attractants.

6. The FAA should issue an advisory circular on reducing wildlife hazards on airports, similar to the documents developed by Transport Canada.

7. Congress should appropriate funds for wildlife hazards research. This research and its funding should be administered by the U.S. Department of Agriculture.

8. The FAA Technical Center should spend the $800,000 Congress authorized, instead of the $200,000 the FAA has elected to spend, for wildlife hazard research and mitigation.

9. The FAA, the USDA, the Environmental Protection Agency, the U.S. Army Corps of Engineers, and the Fish and Wildlife Service should immediately enter into an intra-government agreement to expeditiously resolve public safety matters when federal rules or laws conflict, such as those governing airport wetlands, which serve as wildlife attractants. The agreement should also designate airports and the areas around those airports as "wildlife incompatible" for the protection of both the traveling public and animals.

10. Engine certification standards should reflect the current and foreseeable threat. Some methods of increasing engine robustness in the future, as aviation and wildlife populations grow, should be included in the NPRM on engine certification for bird ingestion that the FAA currently is considering.

11. The FAA should abandon its operational evaluation that permits and encourages airspeeds greater than 250 KIAS below 10,000 feet in areas of known bird activity. The severe damage to the Delta B-727 that departed Houston under this program points out the dangers of high-speed bird strikes. Until aircraft and engines are strengthened or other mitigation actions are taken (see Item 12), high-speed flight at low altitude should be avoided.

12. The FAA should use all technology currently available--for example, Nexrad radar and approach control radars--to warn pilots of imminent hazards. Air traffic controllers should be educated about this threat to public safety and should be required to comply with FAA Order 7110.65 paragraph 2-1-22 and issue timely warnings to pilots, just as they issue windshear alerts, braking action reports, and other safety advisories.