Avro 504 The Avro 504 was a World War I biplane aircraft 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 World War I , in any military capacity , during that conflict . Over 10 , 000 were built from 1913 to the time 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 . Operational history . Small numbers of early aircraft were purchased both by the Royal Flying Corps ( RFC ) and the Royal Naval Air Service ( RNAS ) prior to the start of World War I , 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 front - line 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 . 2c s , 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 World War I . 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 and banner towing , civil 504s continued flying in large numbers until well into the 1930s . The embryonic air service of the Soviet Union formed just after World War I used both original Avro 504s and their own " Avrushka " copy of it for primary training as the U - 1 in the early 1920s , usually powered with 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 . a 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 , Thailand and South Africa , with licensed production taking place in Denmark , Belgium , Canada 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 aeroplane to strafe troops on the ground as well as the first to make a bombing raid over Germany . It was also the first Allied aeroplane to be downed by enemy anti - aircraft fire and was Billy Bishop ' s first army aircraft . The 504 is easily recognisable because of the single skid between the wheels , referred to as the " tooth pick " in the RAF . Survivors and flyable reproductions . A small number of static display , and airworthy examples of the Avro 504 exist , more than a century after the first one flew , one of the airworthy examples being the Shuttleworth Collection ' s example - another flyable example exists in a Canadian aviation museum . An Avro 504K can also be found on static display in the Making of the Modern World Gallery at the London Science Museum . The Old Rhinebeck Aerodrome has had a flyable Avro 504 reproduction aircraft , powered by an original Le Rhône 9J rotary engine , flying since 1971 , and a newly founded company ( Blue Swallow Aircraft ) in Virginia is starting to produce reproduction Avro 504 examples . Manufacturers . The following companies are recorded as manufacturing the Avro 504 under licence .