Martinsyde F.4 Buzzard - Part one

The Martinsyde F.4 Buzzard was a powerful and fast biplane fighter that was developed for the Royal Air Force, but as the World War I ended, its mass production was cancelled. No more than 400 of them were produced and most of them were exported.
After the Great War, Belgium bought at least two of them to equip their Aviation Militaire (Military Aviation). They tested it at the Evere airfield but it was rejected for service.
The airplane was among of the few that founded the Bolivian Cuerpo de Aviación (Bolivian Aviation Corps) as nine of them served there from 1925 until 1929 when they were replaced by more modern types, most probably the Curtiss Hawk IA.
With its native users, only 57 of them were put into service with the Royal Air Force, but they weren't put into operational use. In the inmediate postwar, two of them were used as high speed transports during the Paris Peace Conference in 1919 and some others served in the Central Flying School. As the post-war RAF didn't want the type, it never served as a fighter.
The Finnish Ilmavoimat (Finnish Air Corps) bought a single airplane for testing purposes in April 1923 with 14 more of them being purchased in 1927. They initally served in the Maalentsoskadeer Ut until 1929 and since they served as trainers in the Kauhava School of Aviation until 1939. Nowadays, the Aviation Museum of Central Finland has the only remaining one in exhibition.

Sources:
1. http://www.belgian-wings.be/Webpages/Navigator/Belgian_Aviation_History/BAFAircraft/Bafallaircraft_1919_1945.htm
2. http://www.aeroflight.co.uk/waf/americas/bolivia/Bolivia-af-CMA.htm
3. https://en.wikipedia.org/wiki/Martinsyde_Buzzard
4. https://fi.wikipedia.org/wiki/Martinsyde_F.4_Buzzard (translated)

Avro 584 Avocet

The Avro Avocet was a British single-seat naval fighter that never went beyond the prototype stage.
It was designed by Roy Chadwick, who designed it in order to meet the requirements of the specification 17/25 for a naval fighter (which required an all-metal stressed skin construction with interchangeable wheels and floaters and had to be powered by the Armstrong Withworth Lynx engine) that only had two candidates, this airplane and the Vickers Vireo.
It was an all-metal fighter that was powered by a 230hp Armstrong Siddeley Lynx engine with interchangeable wheels and floats. Even if it hadn't folding wings, it was designed to be easily dismantled so it could be storaged on board a ship.
Two prototypes were built, the first one as a regular wheeled airplane in December 1927, and the second one as a floatplane in April 1928. The Fleet Air Arm evaluated both airplanes at Martlesham Heath but found their performance to be unimpressive due to the low-powered engine so it wasn't ordered into mass production.
The second prototype, however, was used a seaplane trainer for the Schneider Trophy pilots serving with the RAF's High Speed Flight.

Sources:
1. https://en.wikipedia.org/wiki/Avro_Avocet
2. Salamander Books - The Complete Book of FIghters

Avro 566 Avenger

The Avro Avenger was a British prototype biplane fighter of the 1920s.
Designed as a private venture by Roy Chadwick, the same engineer who designed the mythical Avro Lancaster, designed a very aerodynamically clear machine, specially for the 1920s.
It was powered by a Napier Lion VIII delivering 525hp of power. It flew for the first time on 26th June 1926 but it didn't convince the Air Ministry because they didn't favour the Napier Lion as a fighter engine.
A second racing version was made in 1928 with revised struts and ailerons and equi-span wings and powered by a 553hp Napier Lion. It was known as the Avro 567 Avenger II. This second racing airplane, ended it's days as an instructional airframe.

Sources:
1. https://en.wikipedia.org/wiki/Avro_Avenger
2. Salamander Books - The Complete Book of Fighters

Avro 504N - European Users

Th Avro 504N was an improved version of the Avro 504K, with a new engine and some other aerodynamical changes which consisted on a new undercarriage, new wings, a new engine and the removal of the skid. Some internal improvements were also made like the inclusion a direct gravity feed for gas.

It was used by many European countries as it became their standard trainer airplane and it was license built in Belgium by SABCA during the late 1920s until mid-1930s, and in Greece by the Kratiko Ergostasio Aeroplanon (State Aircraft Factory) from 1934 until 1935.

It was powered by either a 150hp or 180hp Armstrong Siddeley Lynx IV engine.

• Belgium: It was the backbone of their trainer squadrons during the 1930s decade. Some of them were still in service when Germany invaded Belgium in May 1940.
• Denmark: The 504N was also the main trainer of the Royal Danish Air Corps during the late 1920s until the mid 1930s. It's worth to mention that these airplanes were equipped with a cowling in the back seat in order for the student to learn how to "blind pilotage".
• Greece: The Greeks ordered some 504N in 1925. 
• Sweden: In December 1925 the Swedish Army Aviation Company ordered five 504N which were delivered in April 1926. They served under the denomination of Sk-3 and Sk-3A in the Flying School at Ljungbyhed. Surprinsingly, they served only until 1928 as they couldn't cope wheel with the harsh cold Swedish weather.
• United Kingdom: The 504N replaced the 504K as the main RAF trainer during the 1920s.

Sources:

1. https://en.wikipedia.org/wiki/Avro_504

2. http://www.natureandtech.com/?cat=109

3. http://forum.valka.cz/topic/view/108754

4. http://greek-war-equipment.blogspot.com.es/2010/10/1920-1936-avro-504.html

5. http://www.avrosys.nu/aircraft/Skol/403sk3/403Sk3.htm

6. http://aviadejavu.ru/Site/Crafts/Craft33477.htm (translated)

Austin Greyhound

The Austin Greyhound was a British two-seater biplane built by Austin Motor Company.

The Air Ministry issued the type III specification in order to obtain a replacement for the Bristol F.2b in 1918 which had to be powered by the ABC Dragonfly radial engine. As Austin Motor Company manufactured more than 800 RAF SE.5, submitted a design made by J. Kenworthy, who was a former designer at the Royal Aircraft Factory. That design was named Austin Greyhound and three prototypes were ordered on 18th May 1918.

It was a two-bay biplane made entirely out of wood with the engine covered by a conical cowling with the cylinder heads protruding. The circular shape of the cowling continued down the fuselage and both upper and lower wings were almost of the same size. It was armed with two synchronised Vickers 0.303 machine guns plus a 0.303 Lewis machine gun placed in a scarff ring in the rear cockpit. Most probably it could also carry a small load of bombs, however we didn't find any info about it whatsoever.

The first prototype was quickly built, but the Dragonfly engine proved to be overweight, underpowered and had some unsolvable reliability problems, so the testing was delayed. The second prototype was sent to the Aeroplane and Armament Experimental Establishment located at Martlesham Heath in January 1919, which followed the first and the third prototype in May and February 1920 respectively. Even if the performance wasn't bad, no production order was placed from any of the competitors and the Bristol F2b remained in active service until 1932 and the last Greyhound remained in use as a flying testbed at Martlesham Heath until June 1922.

Sources:
1. https://en.wikipedia.org/wiki/Austin_Greyhound
2. Salamander Books - The Complete Book of Fighters

Armstrong Whitworth Starling

The Armstrong Whitworth Starling was a British single-seat biplane fighter that competed against the Bristol Bulldog for the Air Ministry F.17/28, among others, and lost.

The Starling was developed to meet the requeriments of the Air Ministry's specification 28/24 for a single-seat fighter able of operating under both day and night conditions replacing the Siskin that way. It was a single-bay sesquiplane with staggered unequal span wings. Fuselage consisted on welded steel-tube structure, the wings had steel spars and wooden ribs were fitted with ailerons on the upper wings only. It was armed with two Vickers 0.303 machine guns.

Two prototypes were built, the first one was powered by a 385hp Armstrong Siddeley Jaguar VII engine and flew for the first time on 12th May 1927, as it was underpowered, it was re-fitted with a 460hp Jaguar V but the performance was still disappointing since the prototype couldn't exceed the speed of 260km/h and didn't achieve the expected 290km/h. The low speed handling was poor too. It was evaluated again later, for the specification F.9/26 in February 1926 but it was rejected as the specification was won by the Bristol Buldog. Since then, the first prototype was returned to Armstrong Whitworth where it was slightly refitted and given a civilian registration in May 1929 and was shown at Olympia in London from July 1929 until December 1930 when it was cancelled from the registration.

The second prototype was heavily redesigned in order to feature more streamlined fuselage, wings and, in spite of the Clark YH Aerofoil section, had smaller lower wings. It featured a 525hp Armstrong Siddeley Panther II engine and flew for the first time on 5th December 1929. It was evaluated in two categories, as a land-based interceptor and as a naval-based interceptor to meet the requeriments of the N.21/26 specification. Even if the performance improved from the first prototype, it wasn't good enough for the Air Ministry requirements, but it carried out some development for the Armstrong Whitworth AW.16.

Sources:
1. https://en.wikipedia.org/wiki/Armstrong_Whitworth_Starling
2. Salamander Books - The Complete Book of Fighters

Armstrong Whitworth Siskin Mk.IV/Mk.V

The development of the Siskin Mk.V started before the Mk.IIIA and was an improved version of the previous Mk.II. It had the shorter upper-wing span and broader chord lower-wing and parallel struts of the Mk.II together with a redesigned vertical tail surfaces, a forward fuselage with rounded sides and was powered by a 385hp Armstrong-Siddeley Jaguar III engine.
It was armed with two Vickers 0.303 machine-guns placed at the sides of the frontern part of the fuselage.

When it was presented, the Romanian government showed interest on it and ordered 70 examples. The production of those examples started in 1925 but in March of that year one Siskin V used as demonstrator that was piloted by a Romanian pilot, crashed, and the order was cancelled, with at least 10 examples being completed but without deliveries having been made.
It's known that at least two Siskin V were flown with civilian registrations.
The Siskin Mk.IV was an ad-hoc civil racing version made for the 1925 King's cup race and it looked similar to the Mk.V. It won that race.

Sources:
1. https://en.wikipedia.org/wiki/Armstrong_Whitworth_Siskin
2. Salamander Books - The Complete Book of Fighters

Armstrong Whitworth Siskin Mk.III/Mk.IIIA - British Users

In  1922 the 14/22 specification was issued by the Air Ministry for an all-metal single-seat high performance airplane and one Armstrong Siddeley Jaguar powered prototype was ordered from Armstrong Whitworth.

Apart from re-engining the airplane, in order to fit the Jaguar IV engine, Major Green, the original designer of the Siskin, redesigned it with an all-metal fuselage, as the Siskin III.
It was praised by the Air Ministry, which placed a contract for three production aircraft on 13th October 1922, with a further six ordered on  26th January 1923, being one of them a prototype for a two-seat variant.
The Siskin Mk.III flew for the first time on 7th May 1923 and the first deliveries to the RAF took place in January 1924. It was the first all-metal fighter to serve with the Royal Air Force.

The Siskin Mk.III was powered by a 385hp Armstrong Siddeley Jaguar IV radial engine and was armed with two Vickers 0.303 machine-guns placed at the sides of the frontern part of the fuselage.

The main production variant, the Siskin Mk.IIIA, was ordered in 1926 and, initially it was powered by a regular Jaguar IV engine, but it was re-engined with the supercharged version of that same engine, the Jaguar IVA. The supercharged engine concept was a novel idea for the time and had little impact on the performance below the 3050m, but it improved the performance and climb rate above that height.
It was powered by a single Armstrong Siddeley Jaguar IVA engine, delivering also 385hp of power, was armed with two Vickers 0.303 machine guns, this time buried in the frontal part of the fuselage, instead of the sides, like the regular Mk.III had and it could carry up to four 9Kg small bombs under the wings.
As Armstrong Whitworth was busy manufacturing the Armstrong Whitworth Atlas, many of the later production of the Siskin was contracted to other firms like Blackburn, Bristol, Gloster and Vickers.

Sources:
1. https://en.wikipedia.org/wiki/Armstrong_Whitworth_Siskin
2. Salamander Books - The Complete Book of Fighters

Armstrong Whitworth Siskin - Prototype and Mk.II

The Armstrong Whitworth Siskin was a British single-seat bipane fighter of the 1920s and was one of the first airplanes to enter service with the Royal Air Force after the end of the World War I.

The first prototype, was built by Siddeley-Deasy, company that was soon incorporated into Armstrong Whitworth, and was designed by Major F.M. Green who was the former chief engineer of the Royal Aircraft Factory. Initally it was Siddeley-Deasy's candidate for the Type1 fighter for a single-seat fighter powered by the ABC Dragonfly radial engine.
The S.R.2 Siskin was a single-bay biplane made out of wood and fabric. Wings were of unequal span and it was fitted with a distinctive fixed landing gear equipped with long oleo strut shock absorbers carrying the axle which was connected to the Radius Rods by a pair of V-struts. The engine was fitted inside a streamlined cowling to reduce drag with each cylinder coming out through special holes designed for them. It was armed with a pair of 0,303 Vickers machine-guns placed at the sides of the frontern part of the airplane.

It flew first in May 1919 and the Dragonfly engine delivered 270hp of power, instead of the theorical 320hp and, in spite of all the expectations put on the Dragonfly engine, it proved to be a disaster as it was underpowered and it was very unreliable being very prone to overheating and causing an untolerable amount of vibration. Even if those were serious issues, the Siskin proved to handle better than it's Dragonfly powered competitors.

The second version, the Mk.II, derived directly from the Siddeley-Deasy S.R.2 which was adquired by Armstrong Whitworth after Siddeley-Deasy closed down their aviation department. It reatined the basic features of it's predecessor but, on the other hand, it was radically redesigned structurally. It embodied fuselage and wing spars of high-tensile steel tubing and strip. The engine was switched from the ABC Dragonfly to the newly built Armstrong-Siddeley Jaguar 14-cylinder two-row that could deliver 325hp of power. It was armed, as the Siddeley-Deasy Siskin, with a pair of 0,303 Vickers machine-guns.
It appeared in August 1922 and the second one was completed in October 1923 but it failed to attract production order so it was sold to the Swedish Aircraft Company of the Signal Corps (the forerunner of the Swedish air force) where it was fitted with skis to make it able to land under winter conditions.

Sources:
1. https://en.wikipedia.org/wiki/Armstrong_Whitworth_Siskin
2. Salamander Books - The Complete Book of FIghters

Armstrong Whitworth Ara

The Armstron Whitworth Ara was a British biplane Fighter designed in the closing stages of the World War I.

In early 1918 the British Air Ministry issued an specification for a fighter capable of replacing the Sopwith Snipe and it had to be powered by the 320hp ABC Dragonfly radial engine which was very promising before even any field testing was carried out. In order to meet this specification, Fred Murphy, the head designer of Armstrong Whitworth designed this fighter, with three prototypes being ordered.

It was a two-bay biplane with an square fuselage and the engine covered in a pointed cowling but with the cylinder heads exposed. Upper wing was placed low on purpose in order to give the pilot a better upwards field of view.

Just like the other candidates to replace the Snipe, the Dragonfly engine prooved to be very disappointing when the first prototype was tested in early 1919. However a second prototype was completed and flown before late 1919. It was abandoned towards the end of the year and Armstrong Whitworth's aircraft department closed down.

It was going to be armed with a pair of Vickers 0.303 (7.7mm) Machine guns.

Sources:
1. https://en.wikipedia.org/wiki/Armstrong_Whitworth_Ara
2. Salamander Books - The Complete Book of Fighters