Community Magazine May 2013

The larger the airplane, the longer the runway it needs to land or take-off. Hours of training are required to develop the expertise necessary for the pilot to land the plane safely and approach the ground at the correct angle and appropriate speed. Any sudden contact with the runway would give the passengers a nasty jolt. Bearing this in mind, give a thought to how a bird flies through the air and manages to land – even the first time – with perfect safety, on a telephone line. What technique does a fly use to land upside down on a ceiling? It is interesting to notice that before landing, most insects extend their six legs out as soon as the landing surface comes within a few body-lengths of them. The legs are constructed to function as efficient s h o c k - a b s o r b e r s , since, unlike jet planes, insects and most birds never run forward after touch-down. They arrive at their landing spot from almost any angle without slowing them down at all, alighting with a sharp jolt. Some idea of the efficiency of the landing gear is given by the estimates that some beetles are subjected to a force about 40 times that of gravity when they strike an unyielding surface – a force which would cause the complete disintegration of any aircraft! Weight Restrictions Anyone who has ever flown in an airplane has undoubtedly heard that dreaded word – overweight! Clothes, shoes, books, toys for the cousins, together with all the vital food supplies for friends’children, must all be contained within 50 pounds, or else you’ll have to suffer the consequences. The reason for this cruel imposition is obvious. The heavier the aircraft, the greater the power it needs to get it off the ground – and fuel costs money. For that reason, special metals are chosen which combine minimal weight with maximum strength, and all the interior fittings of the plane must be made from the lightest materials. The consideration of minimizing the weight is an obvious precondition of airplane design. Just look at the design of birds! To reduce weight, the skeleton is remarkably light. Normally, the skeleton is the heaviest part of the body, but many of the bones of birds are honeycombed with air spaces. Should you think that this would weaken the bones, fear not, for additional strength is given by a crisscross of internal bracing struts. Airplanes, naturally, have adopted the same system. Pause for a moment and think. However strong your desire to lose weight, how can you reduce the weight of your bones? Who taught the thousands of species of birds to design bones with air spaces?! How do you develop an air space in a bone?! Equally astounding is a bird called a gannet, which plunge-dives into the sea from heights of up to 100 feet to catch fish. To help them survive the impact of this tremendous crash, they have spongy bone around the head and beak, and air sacs under the skin around the throat. Birds of a feather Although the designers of airplanes try to copy as many features of birds as possible – such as their streamlined shape, and the retractable under-carriage – one characteristic of birds has not yet been adopted, and perhaps can never be. That is the special covering with which birds have been created – feathers. Feathers are fantastic! Without them, the bird would remain grounded, cold, waterlogged and unrecognized. With them, they give the wing a large surface area which helps keep the bird in the air. Feathers keep the bird warm by trapping a layer of air against the skin. Air is a poor conductor of heat, so this layer of air holds heat inside the body. Are you feeling cold? Go on, try to grow some feathers! Feathers keep the water out, because they are oily. Where on earth does a bird find oil? No problem – the oil is produced by a gland on the bird’s back, close to the tail, and the bird rubs its beak in this oil before it preens itself. Because the feathers are oily, water runs off the oily surface without wetting it. This is how a duck can swim in its pond for hours on end without getting cold or even wet! Additionally, feathers enable birds to recognize each other and camouflage themselves. Thus, for example, terns and many other fish-eating sea-birds have white underparts. Unsuspecting fish cannot see them against the bright sky, as they swoop down for their supper. Other feathers help birds follow their leader. Brent Geese migrate in flocks from Siberia to Europe. To make sure they keep together and do not lose sight of one another, the birds have a white rump that is easily seen from behind in flight. The beauty and complexity of the feather can only be fully appreciated when viewed under a microscope. The vaned feather is made up of a central shaft which is hollow up to two-thirds of its length. Beyond this point it becomes solid to increase its strength. Design! Growing out from the central shaft are hundreds of barbs. Each barb in turn carries hundreds of tiny filaments (called barbules) and these are equipped with minute hooks which interlock with the next row. The whole structure works much like a zip fastener. Or rather, the zip fastener works very much like a feather! If the web splits, the bird simply draws the feather through its beak a few times, and perfection is restored. Amazing, amazing design! The next time a jet plane roars overhead, and you instinctively look skywards, do yourself a favor and look for the immensely superior flying marvels all around you. Tuvia Cohen is a scientist, humorist, and an accomplished author. His bestselling books include: ‘Designer World’, ‘Our Amazing World’, and ‘Our Wondrous World.’ The Gannet - The Gannet is the largest seabird in the North Atlantic. 32 Community Magazine