Volume 16 No 1 Feb 1965.pdf - Lakes Gliding Club

HOW THE ALBATR'OSS SOARSALETTER from an AustraliafJ, Mr. Kennet" Campbell, on the flight of birds- in general and the albatross in particular, senJ to the Duke of Edinburgh andpassed by him to Peter SCOIt, has been forwarded to us.· It is toO long for reproductio'nwith detailed comment, but it shows the writer to be unaware that the firstobservations of the albatross by an experienced soaring pilot were published inTHE SAILPLANE AND GLJDER fQr February, 1935. As this notable contribution to theelucidation of the "mystery" of the albatross is now out of print, the 30th anniversaryof its appearance would seem a suitable occasion for its repr.oduction. Mr. 8amiltonwas an early member of the Londol.r Gliding Club and left for Auslfa/ia in 1933,making these observations on the way. The shearwater is ,a smaller relation of thealbatross.Sir,T might be of some interest if I describeone or two of my ,own personalIobservations of the flight of ocean birds.Firstly, the shearivater, which, inmaking use of a combination of winddeflection soaring and dynamic soaring,is enabled to travel in a general directiona~ainst the wind, not with it, asin the case of pure dynamic soaring.While travelling west across theAustralian Bight against a storm froma direction approximately W.S.W. Iwatched a shearwater for fifteen minutes,and during that tim~, without flapping,it kept level with the ship, flying in abig zig-zag course alternately close to,and then far from, the side of the ship.It would rise almost vertically over thecrest of a big wave, due both to thedeflected current and to the fac.t thatthe wind speed increased with height,until it had reached its maximum possiblealtitude, then it would retract itswings and go into an almost verticaldive into the trough of the wave in frontand flatten out a few inches above thesurface. It would then continue at greatspeed in the "dead" air to leeward ofthe advancing wave and parallel to it,either working towards or away fromthe ship. The rollers not being in trulyparallel lines but mostly criss-crossed,the bird would always pick a rollerwhose crest was not quite at .right ang,leswith the wind direction, and thus foundit possible not only to fly agai~st thewind but to be able to keep up with theship, giving an air speed. in the ship'sdirection of something hke 40 m.p.h.While remembering the erratic coursetaken by the bird, an actual' air speed50of consjderably more than this figuremust have been attained.From my own observations I am ledto believe that the albatross and othersea-birds are unable to soar by makJinguse of the fact that friction alone overthe water slows down th,e air at the surface,as described by CapL Needhamin his article, possibly because thefriction is not great enough. In suggestingthis I am quite aware that theplover and, I think, the ibis perform inthis way over land, where the frictienmight be expected to be greater. I contendthat ther,e must be fairly largewaves which allow a bird to soar simultaneollslyby wind deflection anddynamically, making use ,of the wdead"air in the troughs of the waves. I havethree reasons for believing this:-firstly, I have never seen an albatrossnor any other bird soaring dynamicallyover land-locked water, where waves areof small size even in a strong wind. Ihave seen quite a number but alwaysin flapping flight or soaring over ano,bstruction.Secondly, in watching ocean birdssoaring other than in the up-eurrent Overa ship, they always fly down into theho'lIow and up over the crest of a wave,and thirdly, the following iQcident. Whilerunning with rather a big following seabetween the Cape and Australia I waswatching about 200 sea-birds of all descriptionssoaring behind the ship, travellingwith the wind in this case, and allsoaring in the same manner, down intothe hollow and up over the crest. Asudden squall came up from a directionat rigbt angles to ours and approximatelyparallel to the wave crest lines. As soon