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Aviation History
1936
1936 - 1618.PDF
J0N£ 18, I936. FLIGHT. (•63 might have similar results. To avoid this, the front wheels are placed about one foot farther forward than in the standard machine. It is rather surprising, when one looks into the matter a little closely, how many desirable things become possible when the rear wheel is fitted. One of them is this forward placing of the front wheels. Without the rear wheel this would probably not be feasible, as it might be impossible to get the tail up during the early stages of the take-off; at any rate, the run to take-off would be greatly increased. With the rear wheel holding the tail up, there is no objec tion to placing the front wheels farther forward ; or, rather, the only objection is that the machine may have a slight tendency to swing, due to the wheels being so far ahead of the centre of gravity. Another advantage of the rear wheel is that if all wheels are made retractable, as they probably would be when an aeroplane was designed origin ally to take this type of undercarriage, it becomes possible to provide a very long stroke, so that the undercarriage is capable of absorbing a very considerable shock. This should result in making glide landings and stall landings equally possible on fast and heavily loaded aeroplanes. Brake Accommodation Oh the Avro Avian used for the experimental test work the main undercarriage has been redesigned in order to make it possible to use Palmer wheels with Palmer brakes. In the main, the changes consist in adding an extra strut to the radius rod. The rear wheel is a Dunlop tail wheel carried on a fork which is, in turn, supported on a long- stroke telescopic strut. This strut has its upper end anchored to the fuselage members, and its lower end is positioned by two radius rods arranged in a vee. The shock-absorbing front struts are of usual type, with compressed air for taking the weight of the machine and an oil damper with a leak-hole for checking bouncing. The rear strut is damped in both directions, leak-holes ensuring that the piston can travel slowly without much resistance, but opposing a sudden application of load. When flying the experimental machine, some little mental courage is necessary to leave it in a firm glide right into the ground, but, after the initial attempt, this method of landing loses all its terrors. The undercarriage certainly does everything that is claimed for it, and the only limit to the speed at which the machine may be forced into the ground is that very naturally provided by undercarriage travel and structural strength. After a touch-down at 65 m.p.h. the effect is similar to that in a particularly well-" sprung " machine in which a phenomenally expert instructor is preventing the result ant balloon by holding the tail up. In fact, it is possible to obtain a very mild bounce by the simple expedient of pulling the control hard back at the moment of touching, and so forcing down the tail to a minor degree. The effect then is little worse than that after performing a three- pointer on an unseen ridge. The least effective landing, curiously enough, is the traditionally "good" landing, when the pilot leg touches first and causes the nose to fall immediately afterwards. During the take-off the tail is initially lifted in the ordi nary way, and the machine is then allowed to fly itself off at an indicated speed of 60 m.p.h. If the run appears to be prolonging itself, a gentle backward movement will hoist the machine into the air, and it is possible, of course, to depress the tail at an earlier stage if a quick take-off is required. For the novice the pilot leg will normally pre vent a departure from the ground until there is more than ample control in all axes. When using the brakes as it is possible to use them, im mediately after making contact, the most unusually short landings can be made over high obstacles. During our test the machine was being brought over the Hanwort'i houses at a safe height, yet the run had terminated in something like two hundred yards from the boundary which accommodates these houses. In an "Outlook " paragraph on page 641 and in the private flying comments on page 654 some of the more important possibilities of this de velopment are outlined. A syndicate has been formed under the title, British Landing Gears, Ltd., to develop the undercarriage and place it on the market. The address is 19, Coleman Street, London, E.C. CONVOY : A flight of Vickers Valentia bomber-transports (Pegasus) conveying urgent supplies of machins guns ammunition and stores during the Palestine troubles. By train the 300-mile journey takes fourteen hours. The Valentias do it in three.
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