Avro 504K

The Avro 504K was a development of the Avro 504J that had a universal engine mount capable of taking a wide range of different engines.

The 504J was powered by a 100hp Gnome Monosoupape engine and during 1917 had proved to be a successful training aircraft. However by the end of 1917 the Monosoupape engine was no longer a front line engine so production was slowing. In order to prevent any delays in production of the 504J all spare rotary engines, including 80hp and 110hp Le Rhones and 130hp Clergets were gathered. The 80hp Gnome could easily fit on the standard 504J but the larger engines needed changes to the front fuselage. At the end of 1917 a 130hp Clerget was installed in one aircraft successfully at Gosport. After that A.V.Roe were asked to produce adaptors and a universal engine mounting.

Avro 504K serial E4342

The new mounting was designed by H.E. Broadsmith. It was made up of two bearer plates which could take any engine combined with a suitable open fronted cowling. A large number of 504As and 504Js were completed with this new engine mounting, and designated as the Avro 504K. The 130hp Clerget engine could be fitted directly to the new mount. Other engines needed a circular adaptor that was added to the main engine plate to create the correct size hole for the engine.

Other changes on the 504K included more spacers to strengthen the fuselage and stronger longerons. The angle of the tailplane could be adjusted on the ground to suit the type of engine. New interchangeable upper and lower wing ailerons were used.

The first aircraft to carry the 130hp Clerget on the new mount was completed at Gosport in the autumn of 1917.

With the engine problem solved Avro were ordered to prepare for construction of 100 aircraft per week, plus 20 sets of parts per week to be assembled at the Eastern Aircraft Factory at Aboukir, Egypt. The Avro was to become the sole purely training aircraft in use, replacing thirteen other types.  This was a significant increase in production, but by November 1918 Avro had reached a level of 80 Avro 504Ks per week and the twenty sets of components for Aboukir. Production of the 504K was split between a very large number of companies (see table below). Production didn’t end until 17 January 1927 when the last ten Avro built 504Ks were delivered.

During the war most 504Ks were powered by the 130hp Clerget or 110hp Le Rhone engine. After the war the 100hp Monosoupape became the standard engine as it was easier to control.

In the winter of 1917-18 an Avro 504J was shipped to the US and demonstrated at Washington. As a result the Americans ordered 52 Le Rhone engined 504Ks in July 1918 for use by the A.E.F. in France. They were used by No.3 Instruction Centre at Issoudun. After the war the surviving aircraft were shipped back to the US.

Although the majority of 504Ks were used as trainers, some were modified for use as high altitude home defence aircraft. Work on this began early in 1918 when two Avro 504Js were each given the same set of short span wings. In May the second of these aircraft flew as a single seater armed with a Lewis gun. This led to the conversion of a number of 110hp Le Rhone powered single seat 504Ks into high altitude fighters. The gravity fuel tank on the upper wing was moved to the port to make space for a Lewis gun that was carried on the upper wing. The front cockpit was faired in. This aircraft could reach an altitude of 18,000ft. It was used by a number of Home Defence Squadrons in the north of England.

On 31 October 1918 the RAF had 2,999 Avro 504Js and 504Ks on charge. OF those 2,267 were serving with flying schools, 226 on Home Defence and 111 in Egypt and Palestine.

The Avro 504K remained in use for some time after the end of the war. The Royal Aircraft Establishment used them for a number of experiments. One important set of experiments saw them fitted with wings used metal spars or ribs, designed by Boulton & Paul, Humbers, Vickers and the Steel Wing Company. They were also used in experiments in slow speed flight, parachute tests, airscrew tests, short wave radio and night flying trials and radio controlled flight, amongst many other things.

The 504K remained in service into the late 1920s. It was used by the C.F.S., Nos.1, 2, 3, 4 and 5 Flying Training Schools, No.24 (Communications Squadron) and Nos.600,601, 602 and 603 Squadrons of the Auxiliary Air Force and the Fleet Air Arm training units at Netheravon and Leuchars.

Some were converted into the Avro 540, which was a gunnery trainer with a modified rear cockpit. 

Engine: Wide range
Power: 90-220hp
Crew:
Span: 36ft 0in
Length: 29ft 5in (28ft 11in with Dyak engine)
Height: 10ft 5in

100hp Gnome Monosoupape
Tare weight: 1,100lb
All-up weight: 1,800lb
Max speed: 82mph
Climb Rate:
Service ceiling: 13,000ft
Endurance: 3 hours

110hp Le Rhone
Tare weight: 1,231lb
All-up weight: 1,829lb
Max speed: 90mph
Climb Rate: 6.5min to 8,000ft
Service ceiling: 16,000ft
Endurance: 3 hours
Range: 250 miles

100hp Dyak
Tare weight: 1,320lb
All-up weight: 1,857lb
Max speed: 70mph
Climb Rate:
Service ceiling:
Endurance: 2.75 hours

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