Avro 504K
Single-engine two-seat World War I fighter-bomber-Trainer biplane

Archive Photos

[Avro 504K (E.3349) on display at the Militärhistorisches Museum Flugplatz Berlin-Gatow, Germany on 10/21/2008 (John Shupek photos copyright © 2008 Skytamer Images)]

[Avro 504K (E449) on display at c.1994 at the Royal Air Force Museum, RAF Hendon, London (John Shupek photo copyright © 1994)]

[Avro 504K (E449) on display on 9/7/2002 at the Royal Air Force Museum, RAF Hendon, London (John Shupek photos copyright © 2002 Skytamer Images)]

[Avro 504K (G-CYFG) on display (9/17/2003) at the Canada Aviation Museum, Ottawa, Ontario, Canada (John Shupek photos copyright © 2003 Skytamer Images)]

[Avro 504K (M-MABE, A-28) on display (10/6/20003) at the Museo de Aeronáutica y Astronáutica, Madrid, España (John Shupek photos copyright © 2000 Skytamer Images)]

[Avro 504K (N4929) on display 1998 at the Old Rhinebeck Aerodrome, Rhinebeck, New York, USA (John Shupek photos copyright © 1998)]

[Avro 504K (N4929) on display 9/18/2003 at the Old Rhinebeck Aerodrome, Rhinebeck, New York, USA (John Shupek photo copyright © 2003 Skytamer Images)]

[Avro 504K (E3404), Airplane card: 1977 “The Golden Age of Flying”, Doncella Cigars, UK (The Skytamer Archive)]

Overview of Avro 504 Series ^[2]

Avro 504

• Role: Trainer, Fighter, Bomber
• Manufacturer: Avro
• First flight: 18 September 1913
• Retired: 1934
• Primary users: Royal Flying Corps; Oil Naval Air Service.
• Produced: 1913-1932
• Number built: 8,970

The Avro 504 was a World War I biplane series of aircraft made by the A.V. Roe and Company Ltd. and under license by others. Production during the War totalled 8,970 aircraft and continued for almost twenty 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 aircraft were built from 1913 to the time production ended in 1932.

Design and Development ^[2]

First flown in July 1913, powered by a 80-hp Gnôme Lambda seven-cylinder rotary engine, engine, the Avro 504 was a development of the earlier Avro 500, designed for training and private flying. it was a two-bay all-wood and biplane with the square-section fuselage.

Operational History ^[2]

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 Avro 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.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 100-hp (75 kW) Gnôme or 110-hp (80 kW) Le Rhône engines. 274 converted Avro 504Js and 504Ks 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 Avro 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 Avro 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 (“Little Avro”) copy of it for primary training as the U-1 in the early 1920s, usually powered with Russian-made copies of the Gnôme Monosoupape rotary engine. This Russian version of the Avro 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.

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 Avro 504Ns were finally replaced in 1933 by the Avro 621 “Tutor”, with small numbers continuing in civilian use until 1940, when seven were impressed into RAF service, where they were used for target-towing and glider-towing.

The Avro 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 Avro 504 is easily recognizable because of the single skid between the wheels, referred to as the “tooth pick” in the RAF.

Variants ^[2]

• 504: 80-hp Gnôme Lambda engine. (Original model)
• 504A: Modified with smaller ailerons and broader struts. 80-hp Gnôme engine.
• 504B: Version for RNAS with larger fin. 80-hp Gnôme 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: 100-hp Gnôme engine. Ten built.
• 504F: 75 hp Rolls Royce Hawk engine. One built.
• 504G: 80-hp Gnôme engine.
• 504H: Used for catapult trials. 80-hp Gnôme engine.
• 504J: Used as a trainer. 100-hp Gnôme or 80-hp Le Rhône engine.
• 504K: Two-seat training aircraft. The 504K had a universal mount to take different engines. Single seat fighter conversion used for anti-zeppelin work. Several were assembled in Australia by Australian Aircraft & Engineering. 130-hp Clerget, 100-hp Gnôme Monosoupape or 110-hp 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 license in Mexico as Avro “Anahuac”.
• 504L: Floatplane version. 150-hp Bentley BR1, 130-hp Clerget or 110-hp Le Rhône engines.
• 504M: Three-seat cabin biplane. Only one was ever built. 100-hp Gnôme engine.
• 504N: Two-seat training aircraft. Redesigned postwar trainer for RAF with 160-hp Armstrong Siddeley “Lynx” engine. 598 built.
• 504O: Floatplane version of the 504N. First aircraft to fly above the Arctic Circle in 1923 in the 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 two 1927 with various engines 100-hp Gnôme Monosoupape, 100-hp Avro Alpha, 140-hp Armstrong Siddeley Genet Major and 150-hp Armstrong Siddeley Mongoose, with the Mongoose chosen for production aircraft. Ten were sold to Argentina, with 100 more built by FMA under license in Argentina. At least six were exported to Estonia, remaining in service until 1940, and an unknown number to Peru.
• 504S: Two-seat training aircraft. Built under license in Japan by Nakajima.
• Yokosuka K2Y1: Japanese version of the Avro 504N, given the long designation Yokosuka Navy Type III 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 (119-kW) Gasuden Jimpu 2 radial piston engine. 360 built (K2Y1 and K2Y2). Watanabe build 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.

Survivors and Flyable Reproductions ^[2]

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 a flyable Avro 504K reproduction aircraft, powered by an original 110-hp (82 kW) 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.

The Military Aviation Museum of Pungo, Virginia, USA also has a flyable reconstruction aircraft in its collection. The Avro (A. V. Roe) 504K “H5991” is presented in Royal Flying Corps colors.

Avro 504 Series Operators ^[2]

• Argentina: Argentine Army Aviation Service
• Australia: Australian Flying Corps; Royal Australian Air Force; Western Australian Airways
• Belgium: Belgian Air Force
• Bolivia: Bolivian Air Force
• Brazil: Brazilian Air Force; Brazilian Naval Aviation
• Canada: Royal Canadian Air Force
• Chile: Chilean Air Force; Chilean Navy
• China
• Denmark: Royal Danish Air Force; Royal Danish Navy
• Estonia: Estonian Air Force
• Finland: Finish Air Force
• Greece: Hellenic Air Force; Hellenic Navy
• Guatemala: Guatemalan Air Force
• British India
• Iran: Imperial Iranian Air Force
• Ireland: I Wish Air Service; Irish Air Corps
• Japan
• Latvia: Lesbian Air Force; Aizsargi
• Federated Malay States
• Mexico: Mexican Air Force
• Netherlands: Dutch Army Aviation Group; Royal Netherlands East Indies Army Air Force
• New Zealand: New Zealand Permanent Air Force
• Norway: Norwegian Army Air Service
• Peru: Peruvian Air Force
• Poland
• Portugal: Portuguese Air Force; Portuguese Navy
• Russian Empire: Imperial Russian Air Service
• South Africa: South African Air Force
• Soviet Union: Soviet Air Force
• Kingdom of Spain: Spanish Navy; Spanish Republican Navy
• Sweden: Swedish Air Force; Swedish Navy
• Switzerland
• Siam (Thailand): Royal Thai Air Force; Royal Thai Navy
• Turkey: Turkish Air Force
• United Kingdom: Royal Flying Corps; Royal Air Force; Oil Naval Air Service
• United States: American Expeditionary Force; United States Army Air Service
• Uruguay: Uruguayan Air Force

The Avro Standard Training Biplane ^[3]

By a process of detailed improvement, which has led to increased strength and greater simplicity, and by the adoption of standardized methods of manufacture, the 80-hp machine of 1913 has evolved into the Type 504K, a machine admirably adapted for the methods of quantity production.

General Remarks

This machine is especially suitable for the purpose of training pilots, and has been adopted as the Standard Training Machine by the Royal Air Force.

In the 504K Type the nose of the machine has been altered and engine mounted overhung from the bearers. The machine will now take any of the existing rotary engines up to 150-hp. This has been accomplished by suitably designing the engine mounting and fitting adapters to take the different engines. It will be seen that this is a great advantage from the engine supply point of view.

The machine retains its characteristics of simplicity, strength and controllability, and one of its chief advantages is the ease of which it can be repaired at School Workshops where interchangeable spares can be obtained readily.

Avro 504K Specifications ^[3]

The following tables give the main features of the Avro 504K machine.

General Characteristics

• Type of Aeroplane: 2-Seater Biplane (Training Machine)
• Aeroplane specification: “Avro” Type 504
• Engine: 100-hp Mono Gnôme, 110-hp Clerget, 100-hp Le Rhône, or 130-hp Clerget
• Revolutions of engine for stated b.h.p.: 1,250 r.p.m.

Estimated speed with full load and with all fittings in position.

Maximum speed for the above hp and revolutions:

• At ground level: 95 mph
• At 8,000 ft: 87 mph
• At 10,000 ft: 85 mph

Duration at this speed:

• At ground level: 2 hours
• At 8,000 ft: 2.14 hours
• At 10,000 ft: 3 hours
• Minimum speed with full load near ground: 40 mph
• Estimated speed at 75% power at 8,000 ft: 74 mph
• Estimated speed at 75% power at 10,000 ft: 71 mph
• Estimated duration at 75% power at 8,000 ft: 3.7 hours
• Estimated duration at 75% power at 10,000 ft: 4.25 hours

Estimated climb with full load and with all fittings in position.

• To 3,500 ft: 5 min
• To 8,000 ft: 10 min
• To 10,000 ft: 16 min

Seating Accommodation.

• Pilot, position: Level with trailing edge of lower wing
• Passenger's position: In front of pilot

Airscrew

• Type: 2 bladed “Avro”
• Pitch (110 Le Rhône): 8 ft 8 in
• Diameter: 9 ft 0 in

Overall Dimensions.

• Span of upper wings: 36 ft 0 in
• Span of lower wings: 36 ft 0 in
• Span of tail plane: 10 ft 0 in
• Height overall: 10 ft 5 in
• Length overall: 29 ft 5 in
• Chord top wing: 4 ft 9 in
• Chord second wing: 4 ft 9 in
• Chord tail plane: 2 ft 8⅜ in
• Chord elevator: 2 ft 4 in

Details of Weights and Loadings

Tail Unit

• Tail plane with supports: 21½ lbs
• Elevators: 12 lbs
• Rudder: 8½ lbs
• Total: 42 lbs

Main Lift Structure

• Wings with flaps with center section: 260½ lbs
• Interplane struts: 41 lbs
• Interplane wires: 24½ lbs
• Total: 326 lbs

Alighting Gear

• Undercarriage with axle and skid: 65 lbs
• Main wheels 100 × 700: 40 lbs
• Wing skids: 2 lbs
• Tail skids: 6 lbs
• Total: 113 lbs

Hull

• Body and engine housing: 270 lbs
• Aeroplane control gear and wires: 30 lbs
• Other details, flying instruments, lighting set, etc.: 25 lbs
• Total:
  325 lbs

Power Plant

• Engine with magnetos 110 Le Rhône: 330 lbs
• Airscrews, boss and bolts: 41 lbs
• Oil tanks, cooler and piping: 15 lbs
• Petrol tanks, piping and air pressure system: 39 lbs
• Total: 425 lbs

• Total weight of machine bear with water in radiators: 1,231 lbs

Military Load

• Crew of two at 180 lbs each: 360 lbs

Weight of Machine in Flying Trim

• Weight of machine bare with water in radiators: 1,231 lbs
• Military load: 360 lbs
• Petrol 25½ gallons: 184 lbs
• Oil 6 gallons: 54 lbs
• Total: 1,829 lbs

Total weight of machine in flying trim: 1,829 lbs

Areas: Wings and Ailerons

• Top: 173 ft²
• Second: 157 ft²
• Total: 330 ft²

Wing Flaps

• Top: 22.7 ft.²
• Second: 22.7 ft.²
• Total:
  45.4 ft²

Control Surfaces

• Tail Plane: 26 ft²
• Elevators: 18 ft²
• Rudder: 9 ft²
• Total: 53 ft²

Dihedral

• Top wing: 2.5°
• Second wing: 2.5°

Loadings

• Loading on wing surface: 5.57 lbs per ft²
• Weight fully loaded per hp (normal): 16.7 lbs per hp
• Weight carried on tail in-flight: nil
• Movement of CG with total variation in load during flight: 4.2 in

Controls

• Type: Control pillars and foot bars.
• Positions from which aeroplane may be controlled: Complete dual control.
• What control provided for crew other than pilot: Complete dual control.
• Position of engine controls: On left-hand side of body.
• No adjustment of rotor bar is provided
• Tail skid: Can be controlled if desired.
• Load on tail skid when loaded ready for flight: 100 lbs
• Tail plane adjustable on the ground but not in the air from pilot's seat.

Bracing

• Wings, internal: H.T. steel wire.
• Wings, external: Cable or streamline wires.
• Body: H.T. steel wire.
• Undercarriage: Cable.
• Other parts: Wire and cable.

Undercarriage

• Type: Special “Avro”
• Size of standard wheels fitted: 100 × 700 mm

Materials

• Wing spars: Spruce.
• Wing struts: Spruce.
• Body struts: Spruce and ash.
• Undercarriage struts: Steel tubes.
• Longerons in body: Ash.
• Shock absorber: Rubber cord

Tanks

• 21 gallon tinned steel pressure petrol tank behind engine, weight empty 27 lbs.
• 4½ gallon tinned steel petrol gravity tank in center section, weight empty 10 lbs.
• 6 gallon tinned steel gravity oil tank behind engine, weight empty 12 lbs.

Factor of Safety

• Machine had a factor of safety of 7 on sand test.

Center of Pressure

• The range of movement of center of pressure is 0.3 to 0.5 chord.

Armament

• 1 fixed .303 Lewis atop upper wing (single-seat night fighter variants)

Avro 504K Production: Wartime Deliveries

• D1976 to D2125: Sage
• D5851 to D5950: Henderson Scottish
• D7051 to D7200: Hewlett & Blondeau
• D8251 to D8300: Humber
• D8781 to D9080: Grahame-White
• D9281 to D9380: Parnall
• E301 to E600: Harland & Wolff
• E2901 to E3050: Morgan
• E3051 to E3150: Savage
• E3254 to E3403: Parnall
• E3404 to E3905: A. V. Roe
• E4704 to E4303: Humber
• E4324 to E4373: Eastbourne
• E6737 to E6786: Morgan
• E9207 to F9506: Grahame-White
• F2233 to F2332: Brush
• F2533 to F2632: Sunbeam
• F8696 to F5945: Sage

Avro 504K Production: Post War Deliveries

• F9697 to F9922: Hewlett & Blondeau
• H202 to H350: Henderson Scottish
• H1896 to H2145: Sunbeam
• H2146 to H2645: A. V. Roe
• H2946 to H3195: Brush
• H5140 to H5239: A. V. Roe
• H5240 to H5289: Eastbourne
• H6543 to H6842: Humber
• H7413 to H7562: Hewlett & Blondeau
• H9513 to H9812: Grahame-White
• H9813 to H9912: Sage
• J731 to Jl230: A. V. Roe
• J6896: R.A.F. Halton
• J8331 to J8380: A. V. Roe

References

1. Shupek, John. Avro 504K photos via The Skytamer Archive, Copyright © 1994, 1998, 2000, 2002, 2003, 2008 Skytamer Images. All Rights Reserved
2. Wikipedia. Avro 504
3. Grey, C.G. “Avro, Aeroplanes: The Avro Standard Training Plane.” Jane's All the World's Aircraft 1919 (reprint). Arco Publishing Company, New York, 1969, Library of Congress 69-14964, 1931. pp. 65a - 69a
4. Jackson, A.J. “Avro 504J and Avro 504K” Avro Aircraft since 1908. Putnam Aeronautical Books, London, second edition 1990, ISBN 0-85177-797-X, 1990. pp. 63-73