Alliot Verdon Roe designed the Avro 504, a British trainer aircraft from World War One while a few saw service in World War Two. More Avro 504’s were built than any other British aircraft during World War One and it became the most widely used aircraft to train men for the Royal Flying Corps (RFC).
Pre-World War One, Roe’s main desire was to see a British aviation industry with British aircraft designed by British designers and made by British engineers/craftsmen. With manned flight in its infancy, he found few financial backers. However, ten days before Louis Blériot flew across the English Channel in July 1907, Roe became the first British pilot to fly an all-British powered aircraft – the Roe II Tri-plane. Blériot’s achievement took the shine away from what Roe had done but ironically Blériot had done Roe some good by making investment in flying a more attractive – if still somewhat hazardous – proposition.
Roe experimented with both tri-planes and bi-planes. It was his two-seater E500 that caught the eye of the War Office and between 1912 and 1913 twelve dual-controlled E500 trainers were ordered. This injection of much needed cash allowed Roe to set up A V Roe and Co Ltd.
A natural development of the E500 was the 504. Work on this aircraft started in April 1913 and was finished just twelve weeks later when the first prototype flew at Brooklands in July 1913. In an aerial race in September 1913 the 504 reached a speed of 66 mph when it came fourth in the Second Aerial Derby. The 504 was a bi-plane with both wings being of equal span. The fuselage was a wire-braced wooden box girder design. The original 504’s were fitted with an 80-hp engine.
In the months just before the start of World War One, the War Office ordered twelve Avro 504’s while the Admiralty Office ordered one. All thirteen were delivered by September 1914.
The RFC did not take to the 504 immediately. The first RFC aircraft to be shot down during World War One was an Avro 504 flown by Lieutenant V Waterfall on August 22nd.
However, the 504 did become an accepted part of the RFC and on November 21st 1914, 504’s took part in a bombing raid on Zeppelin sheds at Friedrichshafen in an attack led by Squadron Commander E F Briggs. 504’s also took part in direct attack on Zeppelins by dropping bombs on them while they were in flight.
In early 1915, the 504A was introduced. This became the main version produced by Avro between 1915 and 1916. Its ailerons were shorter but broader and gave better control and response while some 504A’s had no canvas cover over the lower wing so that the pilot had better downward vision. The 504B reverted to the original size ailerons but had a larger rudder. It was thought that this combination gave the pilot better control and made the 504 even more responsive. 240 504B’s were built. While the 504 was primarily a trainer, two were fitted with machine guns and an upward firing Lewis machine gun and were based at Dunkirk.
The first mass produced Avro 504 was version J, though some of these started their ‘life’ as an A version but by the time they were finished were J variants. There seems to be little doubt that Roe used the previous variants as experiments – such as which size ailerons were best; what engine size was best considering that too big an engine would slow the aircraft down. The 504J used a 100 hp Gnome Monosoupape engine and 1,050 were built in total. While the 504J was a reliable aircraft to fly, it depended on good servicing on the ground. It also was the first 504 to use the Gosport speaking tube that allowed the flying instructor to communicate with the trainer. This system was used right through the RAF’s bi plane era, including being used in the famous Tiger Moth.
The most famous 504 was the 504K. This aircraft introduced a new form of engine mounting that allowed the standardisation of the airframe around an open-fronted cowling. For this reason of standardisation, very many 504K’s were made – 6,350 in total. Avro aimed to produce 100 504K’s a week. The Americans were so impressed with it that they ordered 52 504K’s for the American Expeditionary Force.
By the time World War One ended, more 504’s had been built in Britain than any other aircraft. Officially 8,340 were built by Avro or sub-contractor firms such as Sunbeam. The bulk of 504’s were used in training units and did not see combat. Therefore a great number survived the war and were sold off when the RAF was run down post-1918. A 504K without an engine could cost as little as £868 from the Aircraft Disposal Company based in Croydon while a serviceable engine cost £907. Therefore, a post-war Avro 504K could be purchased for less than £1800 – a considerable sum of money for many in post-war Britain but affordable for some. Many foreign governments bought them – Australia, New Zealand, Estonia, Japan and Canada for example. Unlicensed copies were even made in the USSR. Being two-seater, many 504’s were used in what became known as ‘flying circuses’ during the 1920’s and 1930’s. Percival Philips, a captain in the RFC/RAF during World War One and awarded the DFC, flew 91,000 passengers in his 504K in a period of 15 years. The RAF continued to use the 504 as a trainer and ordered 512 aircraft between 1927 and 1933. 504’s were even used in World War Two when they were used with Hotspur glider units and the 504N was used to develop towing techniques for the airborne forces.