1913 multi-role military aircraft family
The Avro 504 is a single-engine biplane bomber made by the Avro aircraft company and under licence by others. Production during World War I totalled 8,970 and continued 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, powered by an 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.
Manufacturers.
The following companies are recorded as manufacturing the Avro 504 under licence.
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) 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.
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.
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.
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 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 "toothpick" in the RAF.
Original model
Modified with smaller ailerons and broader struts. Gnome engine.
Version for RNAS with larger fin. Gnome or Le Rhône engine.
Single-seat anti-zeppelin aircraft for the RNAS. The 504C was fitted with an extra fuel tank, in place of the observer.
Single-seat anti-zeppelin aircraft for the Royal Flying Corps. Six built.
 Gnome Monosoupape engine. Ten built.
 Rolls-Royce Hawk engine. One built.
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.
504C modified for catapult trials. 80 hp (60 kW) Gnome engine.
504A modified to mount a Gnome engine.
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 &amp; Engineering. Clerget 9B, Gnome Monosoupape or Le Rhône 9J engines.
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. Bentley BR1, Clerget or Le Rhône engines.
Three-seat cabin biplane. Only one was ever built. Gnome engine.
Two-seat training aircraft. Redesigned postwar trainer for RAF with 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.
Observer training version of 504K for Japan.
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.
504R modified with 504N undercarriage and Avro Alpha engine.
Two-seat trainer based on 504N for Australia, not built.
Redesigned version of Type 598, not built.
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.
Improved version of the K2Y1, powered by a 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.
Russian copy of the 504K. Over 700 built.
Russian seaplane version.
Specifications (Avro 504K).
"Data from" "The Encyclopedia of World Aircraft", " and Jane's Fighting Aircraft of World War I"General characteristics* Crew: 2* Aspect ratio: * Airfoil: * Fuel capacity: fuel; castor oil* Propellers: 2-bladed Avro fixed-pitch wooden propeller
Performance* Endurance: 
*2 hours at sea level at maximum speed
*2 hours 8 minutes at at maximum speed
*3 hours at at maximum speed
*3 hours 42 minutes at at cruise speed
*4 hours 15 minutes at at cruise speed* Time to altitude: 
* in 5 minutes
* in 10 minutes
* in 16 minutes
Armament
1 fixed .303 Lewis atop upper wing (single-seat night fighter variants)
See also.
Related development
Aircraft of comparable role, configuration, and era
Related lists
Footnotes.
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Notes.
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External links.
[[Category:1910s British bomber aircraft]]
[[Category:1910s British military reconnaissance aircraft]]
[[Category:1910s British military trainer aircraft]]
[[Category:Avro aircraft|504]]
[[Category:Biplanes]]
[[Category:Single-engined tractor aircraft]]
[[Category:Aircraft first flown in 1913]]
[[Category:Rotary-engined aircraft]]