Wednesday, July 18, 2018
Transport Canada - Aviation Safety Letter Animal Ambush: The Challenge of Managing Wildlife Hazards at General Aviation Airports

Animal Ambush: The Challenge of Managing Wildlife Hazards at General Aviation Airports


Increasing wildlife populations and their adaptation

to the airport environment have become a safety and

economic concern for the aviation industry. The limited

management of wildlife hazards at many GA airports adds

impetus for actions by pilots and aircraft owners to assist

in reducing damaging wildlife strikes. Listed below are

recommendations to mitigate the risk of damaging strikes.

Question 1: At what height (above ground level [AGL])

do most strikes occur?


Bird strikes have been reported up to 32 000 ft.

The majority of damaging strikes occur below 100 ft and

frequently between 501 and 3 500 ft. Pilots should climb

expeditiously in areas and seasons of high bird activity and

avoid high-speed flight below 3 500 ft. Speed contributes

more to the amount of damage than bird mass does.

Question 2:

Do more strikes occur during takeoff or landing?


More bird and deer strikes are reported during

the landing phase of flight compared to takeoff and climb.

In contrast, turbine-powered engines are more likely to

sustain substantial damage with possible hull loss during

takeoff and climb. Pilots should delay takeoff if birds are

observed on the runway.

Question 3: Shouldn’t birds sitting or standing on the

runway notice an approaching aircraft and disperse?


Pilots should not assume that birds will detect

or react in time to avoid a strike with their aircraft. The

majority of birds will attempt to avoid approaching

aircraft, but avoidance reaction may be too late or

inappropriate. Furthermore, birds are apparently less able

to detect modern aircraft with quieter engines compared

to aircraft with noisier engines.

Question 4: What about flying or soaring birds?

Do birds normally dive or climb in response to an

approaching aircraft?


The majority of birds encountered above 500 ft

AGL try to dive, and few birds attempt to climb. In

contrast, below 500 ft AGL only 25 percent of the birds

encountered in the air showed an attempt to dive and

32 percent attempted to climb. If an avoidance manoeuvre

is possible, a pilot should try to fly above birds, although

expect unpredictable manoeuvres close to the ground.

Question 5: Are bird strikes only a problem during the

day? What about deer strikes?


More total bird strikes to civil aircraft occur

during daylight, but the probability of a bird strike is

greater at night, especially above 500 ft AGL. Pilots

should fly above 3 500 ft AGL at night during spring

and fall migration periods to minimize the possibility of

en-route bird strikes. For deer, about 80 percent of the

strikes occur at dusk or night.

Question 6: What about season of year?


In North America, July to November is the worst

period for damaging bird strikes in the airport environment

(below 500 ft AGL) and the highest bird population

levels occur in late summer. Above 500 ft, September

to November, April and May are the most dangerous

months—the peak periods of migration. October and

November are the worst months for deer strikes.

Question 7: Are strikes more likely under certain

weather conditions?


Strikes occur more frequently on rainy days.

This increase might relate to the greater abundance of

invertebrate food at the soil surface, which is appetizing

for birds.

Question 8: Are bird strikes more likely to occur to wingmounted

turbofan engines or fuselage-mounted turbofan



Wing-mounted engines were five times more

likely to have a bird strike compared to fuselage-mounted

engines, based on an analysis of engine strikes per

100 000 movements for commercial air carriers in the

U.S. from 1990 to 1999.

Question 9: Will the deployment of on-board radar

disperse birds from the path of an approaching aircraft?


Many species of birds are sensitive to certain

stimuli such as earth’s magnetic field for navigation.

However, there is no scientific evidence that birds detect

radar deployed on aircraft or even that detection would be

sensed as a threat and cause birds to avoid aircraft.

Question 9 a): Are visual devices effective for alerting

birds of approaching aircraft?


Birds often respond to light beams with abrupt

avoidance manoeuvres, although only limited data suggest

that pulsating landing lights reduce bird strikes. Additional

research is needed to determine optimal strategies.

However, pilots should not rely on radar, aircraft and

spinner markings or lights to prevent bird strikes.

Question 9 b): Will ultrasonic devices keep birds out

of hangars and off the airfield?


Ultrasonic devices are not effective against birds

in hangars or on the airfield, and birds do not hear

in the ultrasonic range any better than humans do.

This article was published by Transport Canada in TP 185E -. Reprinted with permission


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