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Aviation History
1970
1970 - 0375.PDF
RIGHT International, 5 March 1970 The bird hazard in all its aspects was discussed by world authorities at an international conference called by the National Research Council of Canada at the Queen's University, Kingston, Ont, on September 2-5 last year. The full report of papers and discussion is as yet unpublished, but the digests contain a number of new aspects of the prob lem and approaches to its solution. New statistics were also added to older ones. For example, Air Canada experienced 36 bird strikes in 1968, an average of nearly one every ten days. The United States Air Force had 363 strikes causing damage and 829 with no damage. BIRD STRIKE By MARCUS LANGLEY ON DECEMBER 1, 1969, at 1745hr local time, a Boeing 707 was taking off from Sydney with 136 people on board when it ran into a flock of starlings. The power of two engines was lost and the pilot aborted his take-off, using such reverse thrust as was available. He overran the runway by 500ft and finished in a swamp. The nose wheel and port main undercarriage were knocked off and the airframe was damaged substantially. There were no casualties, but two passengers were treated for shock. While the swamp would act as an arrester, it would also attract more birdlife than is usually to be found on most runways. The dangers of bird ingestion into aircraft engines is going to increase as aircraft get larger and faster. In the Boeing 747 the engines are about 8ft in diameter, whereas the Spey engines of the BAC One-Eleven are approximately 3ft in diameter. The bird ingestion area is therefore some seven times as great on the former. A Spey takes in up to 2,500 cu ft of air per second and this may contain a number of birds to impact the compressor blades at a very high speed. However, there is evidence to show that in large bypass engines birds may be flung outwards by the first stage of the compressor and then pass through the cold air annulus. Propeller-engined aircraft are at less risk than those with turbojets since the propeller, though perhaps damaged itself, protects the powerplant. Birds are dangerous in two main zones. There are the flocks of starlings and other small birds which inhabit the lower air at the ends of runways; at height there are the migrating streams of larger birds—swans, geese, ducks and the like. In addition there is the very occasional single bird, such as a vulture which may be hovering at 10,000ft or more in the tropics. There are two main approaches to the problem around airports. The first is to make the area unattractive as a habitat and feeding ground, and the second to scare away such birdlife as persists. It was suggested that grass around runways should be kept cut to a length of 10cm, though one speaker, Elwood A. Seaman, an ecologist with the USAF, thought that the length might be graded since one-height mowing might benefit certain species of birds over others and create greater hazards. He felt that the advice of a local biologist should be sought. Dr V. E. F. Solman of Ottawa, and other Canadian speakers, suggested the replacement of grass by some other cover. He mentioned Potentilla tridentata, which would require no main tenance such as fertilizing and mowing, would attract few invertebrates and would have no flowers or seeds pallatable to birds or to the worms and snails on which they feed. Although the tridentata variety of Potentilla is not native to the United Kingdom, others which were mentioned are widely distributed here. These include Potentilla Anserina (Silverwood, goose grass), Medicago lupulina (Black Medick) and varieties of clover. The idea is an interesting one—but one must leave the final selection to local botanists. C. W. Stortenbeker of Holland said that arable land is more attractive to birds than is grassland, particularly stubbles and soil just after cultivation. Cultivation in the neighbourhood of an airport should be reduced to a minimum, and such crops as sugar beet and potatoes preferred to grain. When crop rotation necessitated grain, a green fertiliser should be sown with it to make a stubble unattractive to gulls and lapwings. Apart from these passive methods of discouraging birds, the previously established and well known acoustic methods such
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