Aviation Safety Letter 4/2004

The Sky is Ours to Share: Bird Strikes Can be Hazardous

Bird Strikes Can be Hazardous

Close calls between aircraft and birds of all species occur on a regular basis. The number of reported collisions with birds during the last five years totals 1 975; a little more than one per day. Of course, it is likely that many more were not reported by the aircraft owner or pilot. It is usually deadly for the bird, and very dangerous for the safety of flight. Think of what a small pebble (½ oz. or 14 g) does to your car's tempered glass windshield when it collides with it at 100 km/hr, and you will realize that a small duck or a seagull can inflict damages that may immediately render your airplane unairworthy and endanger your life.

In 1983, an aircraft owner was flying at about 500 ft when he encountered a flock of Canada geese as he executed a turn to return home. The impact, directly on the propeller, tore the engine from its mount, and as it was bolted to the main spar, it failed. This small twin-engine ultralight aircraft fortunately had been equipped with an emergency parachute that successfully lowered both the pilot and the aircraft to the ground. The pilot later became the editor of the Canadian E-magazine, Ultralight News. More recently, on May 20, 2004, a Fairchild SA-227AC Metro was climbing through 9 500 ft after departure from La Ronge, Sask., when the aircraft struck two Canada geese. The aircraft sustained minor damage to its horizontal stabilizer, continued on to destination, and landed without incident. The incident could have spelled disaster if the birds would have hit the windshield, as the geese's weight far exceeds that of the bird used to establish the norm of windshield-impact resistance.

Bird numbers in Canada are astounding, and the danger that they represent to aircraft should not be ignored. Birds survive in areas that offer a safe shelter, good breeding and feeding grounds, and afford them a play area for raising their young. Waterfowl live along rivers and lakes; pelicans and gulls, for example, have a liking for cities, towns and villages situated near large waterways, lakes and seas, where they can forage for easy pickings along the shoreline, or feed on discarded leftovers from city-dwellers at the garbage dump. They enjoy the nearby peaceful airport areas where they will nest and rest, unprovoked by predators. Spring and fall migration do present specific hazardous conditions for pilots, and learning of the specific migratory routes before a flight will minimize the risks at that specific time of the year. Birds can be encountered at any airspace level, even up to 20 000 ft.

An encounter with a flock of ducks or seagulls shortly after takeoff, at low altitude and during climb-out, can represent one of the worst scenarios for a pilot, as there is low forward speed, a high angle of attack, and a risk of engine failure or flight control failure at a time when pilot concentration is at its highest level and there is little margin for error. A bird strike is understood to be any contact between a moving aircraft and a bird. Subsection 6(1) of the Transportation Safety Board Regulations requires that a collision with an obstacle be reported as quickly as possible to authorities in order that the information be compiled, analyzed and that programs may be developed to assist in diminishing the risk that it represents to air safety. Statistics about collisions with birds in Canada tend to show that most bird strikes occur almost equally during the take-off and landing phases of flight; 39% and 41%, respectively. Birds of prey have been observed attacking aircraft, but most birds are alarmed by an incoming aircraft and will try to flee the scene to avoid collision. Flocks of geese have even been seen following low-flying ultralight aircraft during the migratory season, so one must always keep in mind the presence of these creatures during takeoff and approach to landing, whenever flying at low altitude and during the migratory periods of the year. Be alert, and remember, the sky is not ours alone.

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