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Aviation History
1947
1947 - 1352.PDF
-172 FLIGHT AUGUST 14TH. 1947 Design and Psychology ber of pilots tried to identify each of 22 knobs mounted on a vertical panel. From the results, 8 basic shapes were selected among which there was no confusion when identified by touch alone. These are illustrated. The last study involved comparison of the accuracy of track- ing and framing a moving target with different types of handgrip controls. From the evidence of the series of investigations men- tioned above, and from the many other examples which will occur to readers, there is little doubt that great im- provements could be made in cockpit layout and design if it were approached from the psychological or human limitation point of view. It is gratifying that there has been a considerable improvement in this connection in recent British aircraft. The application of colour to con trols and dials, a subject which was not mentioned above, would form the basis of another interesting and useful research. Although the grouping of some types of controls is undesirable for fear of confusion, the grouping of such instruments as temperature and pressure gauges is to be advocated. The introduction of compound instruments carrying two or more dials may offer some advantages but generally leads to a more confusing representation. From the point of view of production, servicing, replace- ment and observation, simple like instruments arranged in banks, and with their needles parallel at their correct normal reading, seem to offer the most advantages for the engineer's panel. The important requirement in this case is to notice as soon as possible that a reading is not what it should be, after that the instrument, can be iden-_ tified by its label, and finally the exact reading may taken. • M. A, AIRSCREWS FOR GAS TURRINES (Continued from page 164) stresses, and the avoidance of torsional or flexural aero- dynamic flutter in the blades. It would now appear possible to design turbine airscrews to 0.16 to 0.2 lb per b.h.p., taking the take-off power as the basis. Airscrews for gas-turbine engines range from 500 b.h.p. to 7,000 b.h.p. It is difficult to be definite on the range of power covered by any particular type, as the diameter permitted by the aircraft design largely dictates the number of blades required. However, to give some idea of the types required to meet the engine range, the following table can be taken as a guide: In every case the airscrews will be constant-speed, feathering, and convertible where desired to either dive or landing-brake functions. 6-blade contra-rotating, 3,000-5,000 b.h.p. 8-blade contra-rotating, 5,000-7,000 b.h.p. The application of the contra-rotating airscrew on single- tngined aircraft will be almost wholly applied to naval deck-landing aircraft employing power units of from 3,000 to 4,500 b.h.p. Powers beyond 4,500 b.h.p., if achieved by coupling together two engine units, will drive contra- rotating airscrews. Whether the coupling between the engines and airscrews will be such that both engines drive the complete contra-rotating airscrew, or, alternatively, each engine drives its own half of the airscrew as an in- 3-blade 500-1,000 b.h.p. 4-blade 1,000-2,500 b.h.p. 5-blade 2,000-3,000 b.h.p. dependent unit (known as co-axial) depends largely upon the peculiarities of the type of engine and aircraft under consideration. It is a debatable point as to which system offers the greater attraction. With the first arrangement, in the event of failure of one of the coupled engines, flight will be sustained by the other engine still driving the complete airscrew, but now at a slightly finer pitch than that pre- viously required to accept the total power of both engines. In order to prevent the '' good'' engine having to drive the " dead " engine, instantaneous release clutches will be required so as to isolate the " dead " engine. With a co- axial arrangement of airscrews, the half which was being driven by the '' dead'' engine would be immediately feathered after the engine failure, flight being sustained by the " good " engine driving its own half of the airscrew. Of the two systems the former gives a quicker recovery and greater propulsive thrust after one engine failure, but has the complication of clutches with the difficult design problem to give instant release. If instant release does not occur, the power required to drive the '' dead '' engine may, in a direct-connected type of unit, completely stall the '' good '' engine With the co-axial arrangement a lesser" propulsive thrust is obtained by the '' good '' engine driving only one-half of the airscrew, and a greater period of time occurs before this thrust is available, since the feathering operation has to be completed in the interven- ing period. The co-axial arrangement does, however, avoid the problem of engine clutches. SPORTSMAN'S AMPHIBIAN A NEW three-seater amphibian designated the GA-2 hasbeen developed by the Goodyear Aircraft Corporation in America, and is now undergoing its flight trials. Theamphibian's cockpit has side-by-side seating for pilot and co-pilot, and one passenger seat behind them. The wheelcontrol, mounted from the instrument panel, leaves plenty of leg room for the pilot and a baggage compartment, measur- ing 11 cubic feet, is provided. The wide, conventional landing gear and the tailwheel are fully retractable and are operated electrically, with a hand crank for emergency operation. The wings (span 36ft) are full cantilever of metal construc- tion with fabric coveting. They have wing-tip slots. • Power is supplieclJby a 145 h.p. Franklin horizontally- opposed enguie^jTj^Hrted as a pusher on a pedestal on top of the wing. Cruising speed of the GA-2 is given as no m.p.h. and the top speed at 125 m.p.h. Landing speed is appro mately 50 m.p.h. The take-off run J water is 1,300ft and the range a mately 370 miles. The problem of cooling pusher-type engines has always presented difficulties. On the GA-2 this has been facilitated by an engine-driven fan mounted on the propeller hub. The aircraft is equipped with basic instruments, two-way radio and a push-button electric starter. The Goodyear Aircraft Corporation's GA-2. The aluminium-alloy wing-tip floats are mounted high enough to prevent damage on small obstructions when operating from land bases.
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