Chapter
1
General
1.1 HISTORY
1.1.1 Birds have been a potential hazard to aircraft since the beginning
of air travel. Bird strikes were a minor risk in the early days as there were
few aircraft in the sky traveling at relatively low speeds. Damage to aircraft
was, therefore, limited to shattered windshields, dented leading edges, and
some damage to the fuselage. The cost of repairs was small and aircraft
operators and airport authorities accepted bird strikes as a normal hazard of
flying.
1.1.2 In time, the speed of aircraft increased and engine noise levels
dropped with the development of newer
generation turbine engines. Aircraft simply became too quick and too quiet for
birds to sense and avoid. Birds inadvertently became a serious threat to aircraft
safety as strikes became more frequent and more serious.
1.1.3 In one incident, for example, a Boeing-747 on take-off developed a
violent vibration in the number two engine. The compressor stalled and the
engine shut down. The aircraft, with 270 passengers aboard, made a smooth
landing at a nearby airport. The carcass of a Glaucous winged gull (Larus glaucescens) was found on the runway at the latter airport. Also found were
several pieces of metal. Upon inspection of the departure airport, guIl-type
remains were found along with an extensively damaged engine and wing parts.
Damage was estimated at U.S.$1.4 million. The examination of the bird remains,
through the use of electrophoresis identification, confirmed that it was a
Glaucous-winged gull.
1.1.4 Damage to aircraft inflicted by a bird strike is usually minor;
however, some strikes can cause aborted take-offs and precautionary landings
and can result in a crash. For instance, in one case a Herring gull (Larus argentatus) was ingested by an engine on a Boeing-737. The affected
engine lost power at which point the pilot decided to abort the take-off. The
pilot applied the brakes at the last minute and tried to stop the aircraft. As
a result, the aircraft skidded off the runway and sank to a halt in a swampy
area. Fifty-eight passengers were evacuated. The costs of lifting the aircraft
out of the mud and getting it back into service were estimated at over U.S.$1.5
million.
1.1.5 The costs of down-time for inspection and repair of aircraft following
bird damage, or suspected bird damage, aborted flights, rescheduling of
aircraft passengers and air cargo, transfer of passengers to alternative means
of transport, overnight accommodation at the expense of the aircraft operator
and the deleterious effects on schedules of connecting flights can often be
very significant and damaging to airline operating budgets and public goodwill.
1.1.6 The ICAO Bird Strike Information System (IBIS) provides analyses of
bird strike reports received from States. An analysis of over 35 000 bird
strikes contained in IBIS reveals the following:
- the total number of significant bird strikes (occurrence resulting in
substantial damage to aircraft, precautionary landing or aborted take-off,
etc.) reported was 1 924 (or 5 per cent of the strikes);
- 69 per cent of the strikes occur during daylight hours; while 15 per
cent occur during night time with the remainder occurring at dawn and dusk;
- 65 percent of the strikes involve a turbo fan (over
- 29 percent of the strikes occur during approach while a further 25 per
cent occur during the take-off run phase;
- 51 percent of strikes occur below
- In 92 percent of the strikes the pilots were not warned of bird activity.
1.1.7 The analysis of bird strike data can reveal trends which will help airport authorities recognize areas of concern which should be addressed through a well managed bird control programme. The bird strike statistics can also be analyzed to determine those times of year or day when bird control is needed the most.