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Aviation History
1940
1940 - 2284.PDF
AUGUST 15, 1940 applied to the opposite wheel, and the divergence is over-corrected. The obvious answer is a steerable nose-wheel, but the stresses on the control and on the pilot's legs would be greater as the size of the machine increased. Some indirect control with an irreversible effect is needed, and even then it is doubtful if such a system would work successfully. Perhaps the trouble could be cured by the use of other steerable wheels while retaining the castoring nose-wheel. Some special system is obviously necessary, particularly as one of the minor advantages of the tricycle is that the take-off run can be started in some other direction than that finally taken. In other words, it may be useful to obtain initial speed before reaching the actual take-off point—though this often seems to me to be an advantage of little practical value. Nevertheless, precise and easy ground control is abso- lutely essential on any large machine. Real Acceleration Only with a level-landing gear does one really know acceleration and realise the enormous drag imposed on a machine during the early part of the take-off by the wings at a high incidence, and by the elevators, which are being used to their fullest extent to lift the tail. Good acceleration, however, automatically pre-supposes poor deceleration. The tricycle type is not only being landed at a somewhat higher speed, but there is abso- lutely nothing to stop it once it is on the ground. It is in flying attitude, with the drag at an absolute mini- mum. Flaps must therefore be designed not only to have their normal lift-increasing and drag-increasing charac- teristics while in the air, but must also have a further position for use immediately after the touch-down, when an enormous increase in drag is required without any change in the ground trim. In other words, the flaps must not tend to lower the tail, give any excess pressure to the nose-wheel or reduce the directional stability. Rather they must help to retain the machine on its original course and offer more adhesion to the braking wheels. Flaps at the best of times are queer things. If you design them to provide a vast excess of lift for the take- off then it is ten to one that the airflow effects are such that they cannot be used during this part of the flight. Either the down-wash lifts the tail too startlingly, or there are other and still more unpleasant effects imme- diately after the take-off. Here is one big advantage of the tricycle ; such down-wash effects will be unim- portant, and high-lift devices can be used to their best advantage while leaving the ground. Undercarriage hoads In a big machine, too, one begins to appreciate the tremendous stresses taken by the undercarriage, but it seems to me that the average load is likely to be less with the three-wheeled gear in the ordinary course of events. Whereas every landing will probably be heavier than that normal in the case of a standard type, the stresses are taken once and for all, and the machine is never subjected to the series of hammer blows which are offered when a normal type is put down carelessly. That is a matter for the technicians to work on, but apart from a plain fly-in (which the tricycle is designed to take) the loading will be natural and even, whereas with the standard type all manner of strange stresses can be applied, from tail-firsters with the consequent series of pitchings to the heavy wheeler with unpro- pheciable developments. The whole structure of a tricycle is bound to be heavier and the retracting gear both heavier and more complicated, but the advan- tages are there. Weight and expense will be amply justified if only in the saving of unnecessary minor and major tragedies at the end of bombing raids. Tired and sometimes wounded pilots are often expected to find their aero- drome in frightful weather conditions and then to pull off a peach of a landing down a flare-path or in day- light with early morning fog to add to the troubles. Perhaps the knowledge that some kind of fair landing must still be made prevents the pilot in such conditions from giving in altogether. I don't know. But the saving in nervous strain, machines, and even in the lives of a valuable crew may be worth consideration. INDICATOR. U.S. COAST GUARD AIRCRAFT An American Service Celebrates Its 150th Birthday HPHE U.S. Coast Guard has a fleet of over sixty aircraft -*• and even has seven of its ships fitted up to carry them, so effective are these winged guardians of the sea- board of America considered. The Intava World for July gives a brief history of this organisation, which probably has an all-round usefulness on humanitarian tasks greater than any other authority making use of the air.' In war- time the Coast Guard takes its place in national defence, but its peacetime duties include, as well as law enforce- ment, the warning of off-shore fishing craft against storms, searching for lost vessels, medical aid for ships at sea (which may require the transport of patients from ship to shore), and the maintenance of an iceberg patrol. It has duties on land also. Rescue of persons from isolated localities, survey work in connection with floods and hurricanes, fast transport of medical supplies such as serum to prevent outbreaks of disease—all these are part of its duties. In addition, a patrol of docks and anchor- ages is flown to observe any water pollution caused by ships illegally discharging oil. The U.S. Coast Guard is the oldest Government maritime service and celebrates its 150th birthday this month. It started its history as the ten vessels of the United States Revenue Marine, but in 1915 was merged with the Life Saving Service to become the Coast Guard. It has had its own training establishment since 1876, but with many changes. Now its modern academy, completed in 1932, provides the personnel, whose qualifications have to be as high as those for the Army or Navy. The aircraft fleet includes the Grumman G-21 and the Hall-Aluminum PH-3. The Grumman is a 3 or 4 seat amphibian specifically designed for coastal patrol, and is an all-metal monoplane powered with two Pratt and Whit- ney Wasp Juniors (400 h.p. at 5,000ft.). Its gross weight is 8,2oolb. and a maximum speed of 184 m.p.h. is claimed. The amphibian undercarriage and tailwheel are both re- tractable manually, the former into the fuselage. The Hall-Aluminum is larger. It is a twin-engined biplane flying boat intended for patrol and rescue, and has room for a crew of four and three or four stretcher cases. Gross weight is 16,1521b. Its two Wright Cyclones (750 h.p. at 3,200ft.) give it a maximum speed at sea level of 153 m.p.h. The hull and wing structure are of aluminium alloy, the wing and tail group being fabric-covered.
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