Avro Type 610

Flight, March 1928

A NEW AVRO COMMERCIAL MONOPLANE
The Type 610 4-Passenger Machine With Radial Engine

   LINDBERGH'S lone flight across the Atlantic last year first drew attention to a type of small commercial machine which has been becoming very popular in America of recent years for "feeder line" work, i.e., for operating on lines branching off the main commercial air routes, and having but a relatively limited amount of traffic to cater for. Built on the cheapest possible lines, such machines have proved very economical both in first cost and in operation, and there can be no doubt that the type will soon make its appearance in this country also. In fact, more than one firm is known to be designing machines of this general type. The first firm publicly to announce the production of a small commercial monoplane is A. V. Roe & Co., whose machine, the type 610, forms the subject of the sketches accompanying these notes.
   As the sketches show, the 610 strongly resembles the American monoplanes of similar type. The resemblance is not confined to the external lines, but will be found in the detail construction also, as the fuselage will be a welded steel tube structure and the wing a normal timber construction braced by steel struts faired with balsa wood. The machine is of the conduite interleave type in that the pilot sits in the forward portion of the cabin, behind large windscreens, while the passengers' seats are arranged in two sets of two, side by side. The cabin will be entered by doors at the rear end, one on each side. The cabin dimensions will be 5 ft. 6 in. by 3 ft. 4 in. by 4 ft. 9 in.
   At the moment it is not quite certain which engine will be fitted, but we gather that the machine is designed to use either the Armstrong-Siddeley "Lynx," the Wright "Whirlwind," or the Bristol "Titan." At any rate, the design is based upon a normal full power of 200 b.h.p. at 1,700 r.p.m.
   The calculated tare weight of the Avro 610 is 1,800 lb., and the pay load to be carried will be 680 lb., corresponding to 4 passengers and their luggage. The non-paying load will consist, normally, of pilot, 40 gallons of petrol and 2 1/2 gallons of oil, in all 495 lb., bringing the gross weight with normal load up to 2,975 lb. The petrol tanks will have a capacity of 60 gallons and the oil tanks 4 gallons, but normally only the quantities given above will be carried, when the duration will be in the neighbourhood of 4 hours at a cruising speed of 110 m.p.h. With full tanks and four passengers, which will bring the gross weight up to 3,140 lb., the range is increased to 675 miles and the duration to 6 hours.
   The general dimensions of the Avro 610 will be: Length, o.a., 27 ft. 6 in.; wing span, 43 ft. 6 in.; wing chord, 7 ft.; wing area, 266 sq. ft. Wing loading, 11-18 lb./sq. ft. Power loading, 14-88 lb./h.p. "Wing Power," 0-75 h.p./sq. ft. (8-1 h.p./sq. m.).
   Following are the estimated performances: Maximum speed, near ground, 123 m.p.h.; at 5,000 ft., 119 m.p.h. at 10,000 ft., 113 m.p.h.; at 15,000 ft., 86 m.p.h. Minimum speed near ground, 55 m.p h.; cruising speed at 2,000 ft., 110 m.p.h.; duration at 110 m.p.h. at 2,000 ft., 4 hours. It is estimated that the ground level rate of climb will be 700 ft./min., and the times of climb are estimated as follows: To 1,000 ft., 1-4 mins.; to 5,000 ft., 8-7 mins.; to 10,000 ft., 23 mins.; to 14,000 ft., 51-4 mins. Service ceiling {i.e., rate of climb = 100 ft./min.), 13,300 ft.; absolute ceiling, 15,500 ft.
   A total structure weight of 1,150 lb. has been estimated, while the remaining 650 lb. of the tare weight is composed of engine, exhaust pipes, airscrew, tanks and piping, and starting gear and accessories.
   The estimated ground level top speed at normal weight and normal power of 200 b.h.p. corresponds to an Everling "Highspeed Figure" of 17-5, which indicates average efficiency; i.e., assuming a propeller efficiency of 75 per cent., the drag coefficient of whole machine at incidence corresponding to top speed is 0-0214 in British "absolute" units. A similar value should be obtained with a biplane.