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Страна: Великобритания

Год: 1919

Fighter

O.Tapper Armstrong Whitworth Aircraft since 1913 (Putnam)

Ara

   In 1917 a new engine had emerged which promised to give decisive air superiority to future British fighters: this was the A.B.C. Dragonfly radial engine which was supposed to give 320 hp for a weight of only 600 lb. Murphy, like many other designers, was quick to appreciate what might he accomplished with a powerplant of this calibre, and early in April 1918 Armstrong Whitworth asked the Air Ministry for blue prints of the Dragonfly; in reply, the Assistant Controller, Design, suggested that the company should not embark on a new design until the Armadillo had been tested, and that it would be advisable to have discussions with the Assistant Controller about which type of aircraft should next he undertaken. But Armstrong Whitworth had their own ideas on the subject and, in spite of the official advice, Murphy went ahead with the design of a Dragonfly-engined fighter. At some stage in the proceedings the official policy must have changed, for three examples of the new fighter, later to he named the Ara, were ordered. The Ara should logically have borne an F.M. number, presumably F.M.5, but it never seems to have carried this designation.
   This second Armstrong Whitworth single-seat fighter retained the two-bay type of wing structure and the same type of slab-sided fuselage which characterized the Armadillo, but this time the top wing was raised a short distance above the fuselage, although the gap was still somewhat narrow. The wings were of equal span, but the chord of the lower wing was less than that of the top wing. The tailplane was conventional, with the fin and rudder, like those of the Armadillo, rather on the small side. The Dragonfly engine was neatly installed in a cowling that faired smoothly into a pointed spinner on the propeller boss. Comparative figures, if they are to be believed, show that the Ara, like the Armadillo, had an unusually low structure weight; both aircraft were of roughly the same size, but the Dragonfly engine weighed some 150 lb more than the B.R.2 rotary; nevertheless, the Ara was only about 70 lb heavier than the Armadillo and both had approximately the same useful load.
   Like its numerous contemporaries, the Ara had no chance of survival because the Dragonfly engine failed completely to fulfil its initial promise. It had been designed by Granville Bradshaw whose object was to produce a light, high-powered radial which would be easy to build on a large scale. Unfortunately, the authorities were too easily persuaded by Bradshaw's optimism, and the engine was put into production before adequate testing had taken place. In the event, the Dragonfly, on which the nation's biggest production effort was to be concentrated, not only failed to develop the power expected, but suffered, among other troubles, from a species of high-frequency vibration which led to the wrecking of the engine after a few hours' running. At that time there was no known cure for this trouble and the whole engine production programme had eventually to be abandoned. Fortunately the war ended before the full impact of this debacle could have its effect.
   The first Ara, F4971, was completed during the summer of 1918, but no engine was immediately available. By the time the first engine was delivered to Armstrong Whitworth in December, it had already been decided that the Ara would not be put into production; the war was over, and by now the Dragonfly's troubles were beginning to become apparent. Nevertheless, two of the three aircraft ordered were completed, the second aircraft, F4972, having a larger gap with the lower wing running below the fuselage. Work on the third airframe was discontinued at a late stage of construction. Because of engine unreliability, no systematic trials were carried out with the Ara, but such figures as are available indicate that, when the engine worked, the aircraft had a good performance, with a top speed of about 150 mph at sea level, and the ability to climb to 10,000 ft in 4 1/2 min. The ultimate fate of the two aircraft is not known, but doubtless they soon found their way on to the scrap heap. The Ara was the last of the Armstrong Whitworth designs to be built at Gosforth and, as recorded elsewhere, the company's aeroplane department was closed down at the end of 1919.

Ara

   Dimensions: Span 27 ft 5 in (8.36 m); length 20 ft 3 in (6.17 m); height 7 ft 10 in (2.39 m); wing area 257 sq ft (23.88 sq m).

   Ara
   320 hp A.B.C. Dragonfly
Max weight: 1,930 lb (875 kg)
Empty weight: 1,320 Ib (599 kg)
Max speed
   Sea level: 150 mph (241 km/hr)
   10,000 ft (3,048 m): 145 mph (233 km/hr)
Climb
   to 10,000ft (3,048m) 4.5 min
Service ceiling: 28,000 ft (8,534 m)
Endurance: 3 1/2 hr

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Описание:

  • O.Tapper Armstrong Whitworth Aircraft since 1913 (Putnam)
  • P.Lewis The British Fighter since 1912 (Putnam)
  • F.Mason The British Fighter since 1912 (Putnam)
  • W.Green, G.Swanborough The Complete Book of Fighters
  • J.Bruce British Aeroplanes 1914-1918 (Putnam)
  • H.King Armament of British Aircraft (Putnam)
  • Jane's All The World Aircraft 1919
  • Журнал Flight