The Avro 504 is a single-engine biplane bomber made by the Avro aircraft company and under licence by others. Production began during World War I—with 8,970 built during the conflict—and continued globally for almost 20 years, making it the most-produced aircraft of any kind that served in any military capacity during the First World War. More than 10,000 were built from 1913 until production ended in 1932.
Design and development
First flown from Brooklands by Fred "Freddie" Raynham on 18 September 1913,Jackson 1990, p.52. powered by an Gnome Lambda seven-cylinder rotary engine, the Avro 504 was an evolution of the earlier Avro 500, designed for training and private flying. It was a two-bay all-wooden biplane with a square-section fuselage.
Manufacturers The following companies are recorded as manufacturing the Avro 504 under licence.Flight 1954 p87
A. V. Roe and Co Ltd., Park Works, Newton Heath, Manchester; and at Hamble Aerodrome, near Southampton, Hants Australian Aircraft and Engineering, Sydney, NSW, Australia Bleriot and SPAD Aircraft Works, Addlestone The Brush Electrical Engineering Co Ltd, Loughborough Canadian Aeroplanes Ltd, Toronto, Ontario, Canada The Eastbourne Aviation Co Ltd, Eastbourne Aero Historic, Parana, Argentina Fabrica Militar de Aviones, Cordoba, Argentina Frederick Sage and Co Ltd, Peterborough and London The Grahame-White Aviation Co Ltd, Hendon Aerodrome, London Harland and Wolff Ltd, Belfast The Henderson Scottish Aviation Factory, Aberdeen Hewlett and Blondeau Ltd, Luton Humber Limited, Coventry Morgan and Co, Leighton Buzzard Nakajima Hikoki Seisaku Sho, Ohta-Machi, Tokyo, Japan Parnall & Sons, Bristol Regent Carriage, Fulham S. E. Saunders Ltd, East Cowes, Isle of Wight Savages Ltd, King's Lynn, SABCA, Brussels, Belgium The Sunbeam Motor Car Co Ltd, Wolverhampton TNCA, Balbuena field in Mexico City Yokosuka Naval Arsenal, Japan KEA, Greece(open access eBook)
Operational history
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)"Casualty Details:Vincent Waterfall". Commonwealth War Graves Commission. Retrieved 10 January 2010.Jackson 1990, p.56. The RNAS used four 504s to form a special flight 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 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.Mason 1994, p.21.
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 to cope with engine shortages. 8,340 Avro 504s had been produced by the end of 1918.Bruce 16 July 1954, p.87.
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 Gnome or 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.Mason 1992, p.127.
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; the type remained in Soviet service till the late 1920s, and much later elsewhere.
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, Japan and Greece.
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 groundBruce 9 July 1954, p.43. 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 "toothpick" in the RAF.
Variants
504: Gnome Lambda engine. Original model 504A: Modified with smaller ailerons and broader struts. Gnome engine. 504B Version for RNAS with larger fin. Gnome or Le Rhône engine. 504C Single-seat anti-zeppelin aircraft for the RNAS. The 504C was fitted with an extra fuel tank, in place of the observer. 504D Single-seat anti-zeppelin aircraft for the Royal Flying Corps. Six built. 504E Gnome Monosoupape engine. Ten built. 504F Rolls-Royce Hawk engine. One built. 504G Two-seat weapons training variant of the Type 504B for the RNAS. The Avro 504G was intended as a bombing/gunnery trainer, with provision for a Scarff ring mounted on the upper longerons, though the final ten delivered had no provision for a gun. Fitted with one 80 hp Gnome powerplant. 50 built and delivered between June 1917 and January 1918. 30 built by Avro and 20 constructed by The Regent Carriage Company. 504H 504C modified for catapult trials. 80 hp (60 kW) Gnome engine. 504J 504A modified to mount a Gnome engine.
504K Two-seat training aircraft. The 504K had a universal mount to take different engines. Single-seat fighter (Comic) conversion used for anti-zeppelin work. Several were assembled in Australia by Australian Aircraft & Engineering. Clerget 9B, Gnome Monosoupape or Le Rhône 9J engines.
504K Mk.II Hybrid trainer based on 504K fuselage with 504N undercarriage and wings and powered by rotary engine. Built under licence in Mexico as Avro Anahuac.Jackson 1990, p.105. 504L Floatplane version. Bentley BR1, Clerget or Le Rhône engines.
504M Three-seat cabin biplane. Only one was ever built. Gnome engine. 504N Two-seat training aircraft. Redesigned postwar trainer for RAF with Armstrong Siddeley Lynx engine. 598 built.
504O Floatplane version of 504N. First aircraft to fly above the Arctic Circle in 1923 Oxford Expedition. 504P Unbuilt version of the 504N with side-by-side seating.Jackson 1990, p.127. 504Q 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. 504R Gosport 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.Jackson 1990, p. 129-133.
504S Two-seat training aircraft. Built under licence in Japan by Nakajima. 540 Observer training version of 504K for Japan. 582 Experimental version of 504N, with new wings of RAF 30 aerofoil section, Frise ailerons on the bottom mainplanes, wing struts reduced to a "K" arrangement and a simplified undercarriage. Converted back to 504N standard in 1928 for Bristol Titan engine test bed. 585 504R modified with 504N undercarriage and Avro Alpha engine. 598 Warregull Two-seat trainer based on 504N for Australia, not built. 599 Warregull II Redesigned version of Type 598, not built. Yokosuka K2Y1 Japanese version of the Avro 504N, given the long designation Yokosuka Navy Type 3 Primary Trainer, powered by a Mitsubishi-built Armstrong Siddeley Mongoose radial piston engine, 104 built.
Yokosuka K2Y2 Improved version of the K2Y1, powered by a Gasuden Jimpu 2 radial piston engine. 360 built (K2Y1 and K2Y2).Mikesh and Abe 1990, p. 276. Watanabe built aircraft were given the long designation Watanabe Navy Type 3-2 Land-based Primary Trainer. U-1 (Uchebnyi – 1) Avrushka Russian copy of the 504K. Over 700 built.Jackson 1990, p. 104. MU-1 (Morskoy Uchebnyi – 1) Russian seaplane version. Orlogsværftet Flyvemaskineværksted LB.I – Danish production at the Royal Naval Dockyard (Orlogsværftet) I1A Brazilian Navy designation of the 504K. I2A Brazilian Navy designation of the 504N and 504O. B.F.4 () Royal Siamese Air Force designation for the 504N.
Operators
Afghan Air Force
Argentine Army Aviation Service – purchased 10 directly from Avro, with a further 34 license-built by FMA from 1928 to 1937. In service until 1938.Magnusson 2007, p. 155The 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.
Australian Flying Corps No. 5 (Training) Squadron in the United Kingdom No. 6 (Training) Squadron in the United Kingdom No. 7 (Training) Squadron in the United Kingdom No. 8 (Training) Squadron in the United Kingdom Central Flying School AFC at Point Cook, Victoria Royal Australian Air Force No. 1 Flying Training School RAAF at Point Cook Western Australian Airways Qantas (Queensland And Northern Territory Aerial Service)
Belgian Air Force purchased 50 British-built 504Ks from 1920 to 1922, with a further 27 being built under license by SABCAJackson 1990, p.88. These were replaced by the 504N, 17 being built by Avro in 1929–31,Jackson 1990, p.123. and 31 being built under license.Jackson 1990, p.124.
Bolivian Air Force 11 Avro 504R Gosport
Brazilian Air Force Brazilian Naval Aviation
Royal Canadian Air Force
Chilean Air Force Chilean Navy Republic of China Chinese Nationalist Air Force China-Puppet Military Aviation of the Peacebuilding Army operated at least one in the trainer role.
Royal Danish Air Force Royal Danish Navy
Estonian Air Force
Finnish Air Force
Hellenic Air Force