The Avro 504 was a First World War 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,[1] 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.
The Avro 504 was designed by Alliot Verdon Roe and was a British trainer aircraft for World War One - although a few saw service in the Second World War, too. During the First World War, there were more Avro 504s built that another other British air fact and it was the most commonly used aircraft during training for the Royal Flying Corps (RFC).

Roe had entered World War One with a desire to help mould a British aviation industry that designed British aircraft using British designers and created these craft with British engineers. Despite being just a few years since the first manned flight, Roe managed to find financial backing and in 1907 he became the first British pilot to fly an all-British powered aircraft - the Roe II Tri-plane. Unfortunately, his achievement was somewhat overshadowed when Louis Blérot flew across the English Channel just ten days later - in July 1907. However, Blérot’s success did help to boost the interest in the aviation industry, indirectly leading to more interest and financial backing for Roe.

Roe created both bi-planes and tai-planes, and it was his two-seater E500 that eventually landed him an order from the War Office. Between 1912 and 1913, 12 dual-controlled E500 trainers were ordered, and this injection of cast made it possible for Toe to set up A V Roe and Co Ltd.

The 504 was the natural development from the E500 and work began on it in April 1913. Twelve weeks later, a prototype was flying at Brooklands and by September 1914 it reached a speed of 66mph in an aerial race, eventually coming fourth in the Second Aerial Derby.

Below Avro 504 prototype after modification with conventional ailerons

As the war drew closer, the War Office ordered 12 Avro 504s and the Admiralty ordered one, with all 13 delivered in September 1914. The RFC did not immediately take to the new plane but in November 1914 they were used as part of a bombing raid on Zeppelin sheds at Friedrichshafen.

Roe continued to develop the plane, and in early 1915 the 504A was introduced. This became the main version of the plane that was produced for the next two years. While similar to its predecessor, it had shorter but broader ailerons to allow better control and some had no canvas cover over the lower wing to increase visibility.

The 504B reverted to the old style of ailerons but it had a larger rudder, which was thought to make the planes even more responsive. There were 240 504Bs built, the majority of which were used for training but two were fitted with machine guns - including upward firing Lewis machine guns - and were based in Dunkirk.

The Avro 504 continued to be developed and the first mass produced version was the J. This version had a 100 hp Gnome Monosoupape engine and was the first to use the Gosport speaking tube to allow pilots to communicate with the trainer. There were 1,050 504 Js built in total.

Arguably the most famous 504 was the Avro 504K, which had a new form of engine mounting system that allowed the standardisation of the airframe around an open-fronted cowling. As a result, 6,350 were made, with 100 being produced a week. The Americans were so impressed with it that they also ordered 52 for use by the American Expeditionary Force.

By the end of the war, more 504s had been built that any other aircraft in the world, with 8,340 officially being built by Avro or sub-contractors. Due to the vast majority never seeing combat, many survived the war and were sold off in great numbers by the RAF.



A 504K without an engine could cost as little as £868 from the Aircraft Disposal Company while a good engine would cost around £907. This meant it was possible to buy an Avro 504 for around £1,800. As such, many foreign governments including Australia, New Zealand, Estonia, Japan and Canada purchased Avro 504s. The fact that the aircraft was two seater also meant many were used in what became known as ‘flying circuses’ during the 1920s and 1930s, while others were used just for pleasure. Percival Philips - captain in the RFC/RAF during the war and recipients of a DFC award - for example flew 91,000 passengers in his 504K over 15 years.

The RAF continued to use the 504 as a training craft after the war and 512 were ordered between 1927 and 1933. They were even used in World War Two, with the original used as Hotspur glider units and the 504N created to develop towing techniques for the airborne forces.
504: 80 hp (60 kW) Gnome Lambda engine.

Original model

504A:
Modified with smaller ailerons and broader struts. 80 hp (60 kW) Gnome engine.










504B
Version for RNAS with larger fin. 80 hp (60 kW) Gnome or Le Rhône engine.
Below interned in Holland




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

100 hp (75 kW) Gnome Monosoupape engine. Ten built.

504F

75 hp (56 kW) 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 100 hp (75 kW) 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.[16] 130 hp (97 kW) Clerget 9B, 100 hp (75 kW) Gnome Monosoupape or 110 hp (82 kW) Le Rhône 9J engines.




















Below 504K with Renault motor.


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.

504L
Floatplane version. 150 hp (110 kW) Bentley BR1, 130 hp (97 kW) Clerget or 110 hp (82 kW) Le Rhône engines.





504M
Three-seat cabin biplane. Only one was ever built. 100 hp (75 kW) Gnome engine.

504N
Two-seat training aircraft. Redesigned postwar trainer for RAF with 160 hp (120 kW) Armstrong Siddeley Lynx engine. 598 built.








Canadian Vickers-built Avro 504NS




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.

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.

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 90 hp (67 kW) 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 130 hp (97 kW) Mitsubishi-built Armstrong Siddeley Mongoose radial piston engine, 104 built.

Yokosuka K2Y2

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.

U-1 (Uchebnyi – 1) Avrushka

Russian copy of the 504K. Over 700 built.

MU-1 (Morskoy Uchebnyi – 1)

Russian seaplane version.

Orlogsværftet Flyvemaskineværksted LB.I – Danish production at the Royal Naval Dockyard (Orlogsværftet)

Specifications (Avro 504K)
General characteristics

Crew: 2
Length: 29 ft 5 in (8.97 m)
Wingspan: 36 ft 0 in (10.97 m)
Height: 10 ft 5 in (3.18 m)
Wing area: 330 sq ft (31 m2)
Empty weight: 1,231 lb (558 kg)
Gross weight: 1,829 lb (830 kg)
Fuel capacity: 25.5 imp gal (31 US gal; 116 L) fuel ; 6 imp gal (7 US gal; 27 L) castor oil
Powerplant: 1 × Le Rhône 9J 9-cylinder air-cooled rotary piston engine, 110 hp (82 kW)
Propellers: 2-bladed Avro fixed-pitch wooden propeller, 9 ft 0 in (2.74 m) diameter 8 ft 8 in (2.6 m) pitch
Performance
Maximum speed: 95 mph (153 km/h, 83 kn) at sea level

87 mph (76 kn; 140 km/h) at 8,000 ft (2,400 m)
85 mph (74 kn; 137 km/h) at 10,000 ft (3,000 m)

Cruise speed: 74 mph (119 km/h, 64 kn) at 75% power at 8,000 ft (2,400 m)

71 mph (62 kn; 114 km/h) at 75% power at 10,000 ft (3,000 m)

Stall speed: 40 mph (64 km/h, 35 kn)
Range: 250 mi (400 km, 220 nmi)
Endurance:

2 hours at sea level at maximum speed
2 hours 8 minutes at 8,000 ft (2,400 m) at maximum speed
3 hours at 10,000 ft (3,000 m) at maximum speed
3 hours 42 minutes at 8,000 ft (2,400 m) at cruise speed
4 hours 15 minutes at 10,000 ft (3,000 m) at cruise speed

Service ceiling: 16,000 ft (4,900 m)
Rate of climb: 700 ft/min (3.6 m/s)
Time to altitude:

3,500 ft (1,100 m) in 5 minutes
8,000 ft (2,400 m) in 10 minutes
10,000 ft (3,000 m) in 16 minutes

Wing loading: 5.54 lb/sq ft (27.0 kg/m2)
Power/mass: 0.06 hp/lb (0.099 kW/kg)
Armament
1 fixed .303 Lewis atop upper wing (single-seat night fighter variants)
(Text from here -- https://historylearning.com/world-war-one/aerial-warfare-world-war-one/avro-504/)