The Avro 504 was a First World War biplaneaircraft made by the Avro aircraft company and under licence by others. Production during the war totalled 8,970 and continued for almost 20 years, making it the most-produced aircraft of any kind that served in the First World War, in any military capacity, during that conflict. More than 10,000 were built from 1913 until production ended in 1932.
Design and development
First flown on 18 September 1913, powered by an 80 hp (60 kW) Gnome Lambda seven-cylinder rotary engine, the Avro 504 was a development of the earlier Avro 500, designed for training and private flying. It was a two-bay all-wooden biplane with a square-section fuselage.
The Shuttleworth Avro 504K
Small numbers of early aircraft were purchased by the Royal Flying Corps (RFC) and the Royal Naval Air Service (RNAS) prior to the start of the First World War, and were taken to France when the war started. One of the RFC aircraft was the first British aircraft to be shot down by the Germans, on 22 August 1914. The pilot was 2nd Lt. Vincent Waterfall and his navigator Lt Charles George Gordon Bayly (both of 5 Sqn RFC) The RNAS used four 504s to form a special flight in order to bomb the Zeppelin works at Friedrichshafen on the shores of Lake Constance. Three set out from Belfort in north-eastern France on 21 November 1914, carrying four 20 lb (9 kg) bombs each. While one aircraft was shot down, the raid was successful, with several direct hits on the airship sheds and the destruction of the hydrogen generating plant.
Soon obsolete as a frontline aircraft, it came into its own as a trainer, with thousands being built during the war, with the major production types being the 504J and the mass production 504K, designed with modified engine bearers to accommodate a range of engines in order to cope with engine shortages. 8,340 Avro 504s had been produced by the end of 1918.
In the winter of 1917-18 it was decided to use converted 504Js and 504Ks to equip Home Defence squadrons of the RFC, replacing ageing B.E.2cs, which had poor altitude performance. These aircraft were modified as single-seaters, armed with a Lewis gun above the wing on a Foster mounting, and powered by 100 hp (75 kW) Gnome or 110 hp (80 kW) Le Rhône engines. 274 converted Avro 504Js and Ks were issued to eight home defence squadrons in 1918, with 226 still being used as fighters at the end of the First World War.
Following the end of the war, while the type continued in service as the standard trainer of the RAF, large numbers of surplus aircraft were available for sale, both for civil and military use. More than 300 504Ks were placed on the civil register in Britain. Used for training, pleasure flying, banner towing and even barnstorming exhibitions (as was ongoing in North America following World War I with the similar-role, surplus Curtiss JN-4s and Standard J-1s); civil 504s continued flying in large numbers until well into the 1930s.
The embryonic air service of the Soviet Union, formed just after the First World War, used both original Avro 504s and their own Avrushka (" Little Avro") copy of it for primary training as the U-1 in the early 1920s, usually powered by Russian-made copies of the Gnome Monosoupape rotary engine. This Russian version of the 504 was replaced by what would become the most produced biplane in all of aviation history, the Polikarpov Po-2, first known as the U-2 in Soviet service in the late 1920s.
Although Avro 504s sold to China were training versions, they participated in battles among warlords by acting as bombers with the pilot dropping hand grenades and modified mortar shells.
The improved, redesigned and radial-engined 504N with a new undercarriage was produced by Avro in 1925. After evaluation of two prototypes, one powered by the Bristol Lucifer and the other by the Armstrong-Siddeley Lynx, the Lynx-powered aircraft was selected by the RAF to replace the 504K. 592 were built between 1925 and 1932, equipping the RAF's five flying training schools, while also being used as communication aircraft. The 504N was also exported to the armed forces of Belgium, Brazil, Chile, Denmark, Greece, Siam and South Africa, with licensed production taking place in Denmark, Belgium, Canada, Siam and Japan.
The RAF's 504Ns were finally replaced in 1933 by the Avro Tutor, with small numbers continuing in civilian use until 1940, when seven were impressed into RAF service, where they were used for target- and glider-towing.
The 504 was the first British aeroplane to strafe troops on the ground as well as the first British aircraft to make a bombing raid over Germany. It was also the first Allied aeroplane to be downed by enemy anti-aircraft fire and was the first aircraft flown by many future aces, including Billy Bishop.
The 504 is easily recognisable because of the single skid between the wheels, referred to as the "tooth pick" in the RAF.
Hybrid trainer based on 504K fuselage with 504N undercarriage and wings and powered by rotary engine. Built under licence in Mexico as Avro Anahuac.
Floatplane version. 150 hp (110 kW) Bentley BR1, 130 hp (97 kW) Clerget or 110 hp (82 kW) Le Rhône engines.
Three-seat cabin biplane. Only one was ever built. 100 hp (75 kW) Gnome engine.
Two-seat training aircraft. Redesigned postwar trainer for RAF with 160 hp (120 kW) Armstrong Siddeley Lynx engine. 598 built.
Floatplane version of 504N. First aircraft to fly above the Arctic Circle in 1923 Oxford Expedition.
Unbuilt version of the 504N with side-by-side seating.
Three-seat cabin biplane. The 504Q was built for the Oxford University Arctic Expedition. Only one was ever built, powered by an Armstrong Siddeley Lynx engine.
Reworked trainer with revised, lightweight structure. Five prototypes flown 1926 to 1927 with various engines (100 hp/75 kW Gnome Monosoupape, 100 hp/75 kW) Avro Alpha, 140 hp/104 kW Armstrong Siddeley Genet Major and 150 hp/110 kW) Armstrong Siddeley Mongoose), with the Mongoose chosen for production aircraft. Ten were sold to Argentina, with 100 more built by FMA under licence in Argentina. Twelve were exported to Estonia, remaining in service until 1940, and an unknown number to Peru.
Two-seat training aircraft. Built under licence in Japan by Nakajima.
Japanese version of the Avro 504N, given the long designation Yokosuka Navy Type 3 Primary Trainer, powered by a 130 hp (97 kW) Mitsubishi-built Armstrong Siddeley Mongoose radial piston engine, 104 built.
Improved version of the K2Y1, powered by a 160 hp (120 kW) Gasuden Jimpu 2 radial piston engine. 360 built (K2Y1 and K2Y2). Watanabe built aircraft were given the long designation Watanabe Navy Type 3-2 Land-based Primary Trainer.
Belgian Air Force purchased 50 British-built 504Ks from 1920 to 1922, with a further 27 being built under license by SABCA These were replaced by the 504N, 17 being built by Avro in 1929-31, and 31 being built under license.
ZK-ACU - 504K purchased by the New Zealand Permanent Air Force in 1925, allocated serial A202, and subsequently operated as a civilian aircraft. The restored aircraft is airworthy and owned by The Vintage Aviator.
Unknown - 504K on static display at the Norwegian Aviation Museum in Bodø, Nordland. It was in service from July 1921 to 1928 and has been on display at the museum since 1995. It is painted with the registration number 103, which belonged to 504A that crashed in 1919.
BK892 - 504K airworthy at the Shuttleworth Collection in Old Warden, Bedfordshire. It was originally given the serial number H5199, but was converted to a 504N and sold into civilian ownership. However, it was later impressed into RAF service during World War II as a glider tug, at which point it was given a new serial number. Again returned to civilian use after the war, it was used in the filming of Reach For The Sky.
^The 504 is listed in several sources as having been used by the Argentine Air Force. This is because its predecessor, the Army Aviation Service, was established in 1912 and dissolved in 1945 when the Air Force was created.
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