06/30/2012. Design work on a successor to the Avro 500, begun at Brownsfield Mills, Manchester in November 1912, was completed at the new Clifton Street works early the following year, Messrs. Chadwick and Taylor being responsible for the fuselage and undercarriage and H. E. Broadsmith the wings. Designated Avro 504, it was very lightly constructed with a rectangular section, wire braced, box-girder fuselage built from four ash longerons channeled for lightness and strengthened by flanges. Cross struts were of spruce.
For maximum view the pilot sat in the rear, the passenger occupying the front cockpit, from the corners of which four ash struts supported the centre section. Equal span, two bay wings were rigged with stagger and braced by streamline section, hollow spruce interplane struts pin-jointed to the spars. Each wing panel consisted of five main ribs with spanwise stringers supporting a number of contour-forming strips of wood anchored to leading and trailing edges. Lateral control was by inversely tapered ailerons rigidly fixed at the inner end, the widened outer ends of which were warped by means of cables.
Although similar to that of the Avro 500, the undercarriage was a much improved and simplified unit. An ash skid was anchored to the fuselage by steel V-struts as before, but the axle was no longer bolted to it and was no longer a laminated spring. Instead, a simple steel tube axle was used in conjunction with two main undercarriage legs having built-in rubber shock absorbers (bungee cord wound round the two halves of the leg) in streamlined cases. The tail skid was attached to the bottom of a comma-type rudder.
In design, construction and performance the Avro 504 was considerably in advance of other 1913 types and benefited from the use of an improved wing section. Power was supplied by one of the new 80 hp Gnome rotaries (the actual power output of which is said to have been nearer 62 hp) installed in a square section cowling bulged on top and sides.
To give it the widest possible publicity the Avro 504 was entered for the 1913 Aerial Derby and consequently was built in considerable secrecy. Its arrival at Hendon on September 20, 1913, morning of the race, was therefore something of a sensation as it was obviously very fast and the impression of speed was heightened by its staggered mainplanes. When F.P. Raynham crossed the finishing line in fourth place at an average speed of 66,5 mph (107 kmh), few realized that the Avro 504 was virtually untried, having been delivered at Brooklands only three days before (September 17), and flown for the first time on the following day.
After the Aerial Derby the Blackburn Aeroplane and Motor Co. Ltd. issued a challenge to its Lancashire rivals and on September 29 Raynham flew the Avro 504 from Brooklands to Leeds for a race against a new Blackburn monoplane flown by Harold Blackburn. The 100 mls (161 km) race was held on October 2 over a course starting and finishing at Leeds and passing over York, Doncaster, Sheffield and Barnsley. With H.V. Roe as passenger, Raynham flew neck and neck with Blackburn until bad visibility forced him to land near Barnsley.
Although basically a sound aeroplane the 504 needed modification and went back to the Manchester works where the engine mounting was changed for an improved version carrying more streamlined cowlings. Aileron control was also lightened by replacing the warping arrangement with constant chord hinged ailerons with wires to complete the circuit in place of the original rods. The wing structure was strengthened by replacing the hollow pin-jointed interplane struts by solid ones fitted in metal sockets.
Redelivered at Brooklands at the end of October, the 504 was flown a great deal by Raynham during the following month. He made a forced landing at Horley with a broken carburetor control during the Hendon-Brighton-Hendon race on November 8; flew from Brooklands to Farnborough and back on November 15; gained second place in the Shell Trophy Race at Hendon the same afternoon and broke the lap record at 73 mph 117.5 kmh); spent a week on day and night flying at Shoreham and flew to Farnborough for official tests on November 24. With a passenger and fuel for three hours the Avro 504 clocked 80.9 mph (130.2 kmh) over the measured mile (1.609 km) and climbed to 1,000 ft (305 m) in 1 min. 45 sec.
An outstanding performance put up by Raynham on February 4 was a climb to 15,000 ft (4,572 m) over Brooklands. This exceeded the existing British altitude record by almost 2,000 ft (610 m) but was not an officially observed record. During the descent Raynham shut off his engine, put the machine into a glide, and 25 minutes later was at 5,000 ft (1,524 m) over Hendon some 20 mls (32 km) away. He then spiraled down to a landing, still without using his engine. Carrying R.J. MacGeagh Hurst in the front seat Raynham made an officially observed climb to a record height of 14,420 ft (4,395 m) over Brooklands on February 10, 1914.
Later in the season the machine was purchased by the Daily Mail and, as pictured above, toured the country giving passenger flights piloted by F.P. Raynham and G. Lusted. The A.V. Roe and Co. Ltd. (trading as Avro) built an interchangeable twin float undercarriage so that the machine could be flown off the sea at coast resorts. At the same time the original 80 hp Gnome was replaced by an 80 hp Gnome Monosoupape which was supposed to give more power but which in fact gave only trouble.
First flights as a seaplane took place at Paignton in April 1914, after which it visited Falmouth, Southport and Ireland but when war was declared on August 4, the machine was at Shoreham where it was immediately commandeered. Two days later the career of this historic aeroplane ended when the engine failed as Raynham took off to deliver it to the RN Air Service. With no height in hand there was no alternative to putting the machine down on land where it was damaged beyond repair.