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Aviation History
1954
1954 - 1998.PDF
PLIGHT, 9 July 1954 41 <mm:M-OC PART I jf "Flight" photograph of ihe originpt 504, showing the square engine cowling and the warping, inverse- tapered, strut-connected ailerons. THE AVRO 504 v Historic Military Aircraft No. 8 ALTHOUGH it performed few resounding feats of arms, the Avro 504 in its great variety of forms is assured of a Lplace of honour in our aircraft history. Whether it is remembered as a delightful trainer of the war period or as a friendly aeroplane popping into and out of improbable fields as a joy-riding machine in the inter-war years, its immortality is secure. Above all, it was the aircraft which helped to lay the foundations of decades of safe and logical flying instruction. Recalling the birth of the Avro 504 Sir Alliott Verdon-Roe writes: — "I still have my original rough pencil sketch on in squared paper which started this aeroplane. There is a considerable amount of minute written matter on the drawing. When 1 designed this aero plane 1 thought that we would be fortunate if we received an order for half-a-dozen. -s^ "I was very particular about the detail design, which was on unit construction lines for easy assembling, rather a new idea then. I kept paper and pencil by my bedside (and still do) to sketch and write ideas before forgetting them. While travelling in trains then most of the time was spent scheming the derail design. It was a job which fascinated me. Every detail was given most careful thought before being entrusted to the draughtsmen. "Reduction of weight, ease of manufacture, simplification of parts, were among, my aims and I felt that the machine would have good flying qualities. The wing section was pure guess work. I produced a much lighter engine plate than the original, and equally strong, but the authorities would not allow its adoption." Construction of the first Avro 504 was begun in April, 1913, and its first tests were carried out at Brooklands in July. The 504 made its debut at Hendon on September 20th of that year as an entrant in the second Aerial Derby. The Avro 504 was more closely related to the Avro Type E of 1912 than to any other preceding Avro type. The Type E was given the Avro type number 500, and was a two-seat two-bay biplane powered by the 50 h.p. Gnome rotary engine: a single- seat version also existed. The type was ordered for the then newly-formed Royal Flying Corps. The Avro 500 had unstaggered wings and a central skid under carriage in which the wheels were mounted at the ends of a trans verse leaf spring. Lateral control was by wing-warping on most machines, but at least one Avro 500 was fitted with ailerons of inverse taper. The rudder also underwent modification. When the prototype Avro 504 first appeared, it had the 80 h.p. Gnome engine installed in a nose-bearing mounting and within a cowling of square cross-section; the cowling had an arched top and bulged sides. The fuselage was a typical wire-braced wooden box-girder with the upper longerons quite straight in side eleva- tton. The fuselage terminated in a vertical stern-post to which By J. M. BRUCE, M., was hinged a comma-shaped-sudder; there was no fin, and the tail- skid was attached directly to the bottom of the rudder. The main undercarriage was an original variation on the wheels-and-skid theme. There was a long central skid, and each main under carriage leg carried its own shock absorber encased in a fairing. Each shock absorber consisted of 8ft 8in of rubber cord in tension. The two-bay wings were of equal span and had a pronounced stagger. Each wing panel had only five fully formed ribs, which also served as compression members. Light spanwise stringers were let into these ribs, and the remaining contour-forming ribs consisted of strips of wood which were fastened to the leading edge, spars, stringers, and trailing edge. Lateral control was obtained by the curious device of warping ailerons. Although separate surfaces, these ailerons were secured at their inboard ends; they were inversely tapered, and their broad outer ends were warped by means of cables. Upper and lower ailerons were connected by a strut. It was at once obvious that, with the possible exception of the warping ailerons, the Avro 504 was a thoroughly workmanlike aeroplane and considerably in advance of most of its contem poraries in design, construction and performance. Much of the early flying of the 504 was done by the late F. P. Raynham. Flown by him, the machine was placed fourth in the second Aerial Derby at an average speed of 66.5 m.p.h. Another contest in which the prototype 504 took part, again flown by Raynham, was the so-called "War of the Roses" contest flown off on October. 2nd, 1913. In this, the Avro firm had accepted a challenge to a cross-country race against Dr. Christie's new Blackburn monoplane, flown by Harold Blackburn. A trophy was provided by the Yorkshire Evening News, and the course was Leeds, York, Doncaster, Sheffield, Barnsley, Leeds, a total distance of 100 miles. Visibility was very bad, and Rayn ham, who was over completely strange territory, had to abandon the race when near Barnsley. The 504 underwent certain modifications early in its career. The engine was given a new nose-bearing support made of bent steel tubing, over which was fitted a new cowling of rather bulbous appearance but better streamline form. Lateral control with the warping ailerons was not particularly effective, so freely-hinged conventional ailerons of constant chord were substituted. On November 24th, 1913, Raynham flew the machine to Farn- borough for it to undergo official tests. Over a measured course the Avro clocked a speed of 80.9 m.p.h. and climbed to 1,000ft in 1 min 45 sees; the stalling speed was 43 m.p.h. The tests were carried out with a passenger and three hours' fuel on board. These performance figures made a deep impression at the time, but their impact was somewhat lessened when, only five days later,
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