Arado Ar 68

The Arado Ar 68 was a single-seat biplane fighter designed and produced by the German aircraft manufacturer Arado Flugzeugwerke. It was among the first fighters produced when Germany abandoned the restrictions of the Treaty of Versailles and began rearming.

The Ar 68 was a part of Arado's continuing fighter development programme, being designed during the early 1930s as a biplane of relatively standard construction. Both the Rolls-Royce Kestrel and BMW VI selected to power the type proved to be inferior in terms of high altitude performance to the newer Junkers Jumo 210, however, due to limited availability of that only, only late production Ar 68s were outfitted with this powerplant. In addition to its twin 7.92 mm (0.312 in) MG 17 machine guns, some aircraft were provisioned with a compact bomb bay. While the Ar 68 possessed favourable handling characteristics, some officials were concerned that the unforgiving nature of high-performance aircraft would make the aircraft unsuitable, allegedly nearly causing production to be terminated.

The prototype made its maiden flight in early 1934; Chief of the Technical Office Ernst Udet personally flew the aircraft, during which the competing Heinkel He 51 proved to be outclassed. During 1936, the Ar 68 entered service with the Luftwaffe; two years later, it was used by Condor Legion in active combat during the Spanish Civil War. In response to the Soviet Polikarpov I-16, Arado upgraded the engine of the Ar 68E, which was the Luftwaffe's most widely used fighter during 1937–1938. The type was eclipsed by the Messerschmitt Bf 109, a monoplane fighter, prior to the outbreak of the Second World War; however, it continued to be operated, mainly as a trainer, as late as 1944.

Background
During the early to mid 1920s, the German aircraft manufacturer Arado had, in conformance with the restrictions on Germany's aviation industry enacted by the Treaty of Versailles, largely focused upon the civil aviation market. However, the company quickly recognised the opportunities available from the Reichswehr (German armed forces), particularly during the 1926-1929 rearmament programme. One initiative of this programme was the development of military prototypes that could, in the event of conflict breaking out, be promptly put into mass production. Furthermore, the Reichswehr was quietly re-establishing a secret air force under the guise of setting up 'display squadrons'. Despite these ambitions, government funding for aviation was limited, and several of the larger German aircraft manufacturers saw little value in producing prototype military aircraft with seemingly little chance of a production order following.

Work on what would become the Ar 68 started in 1932 as part of the company's continuing development programme for fighter designs. As favoured by one of Arado's senior design team members, the aeronautical engineer Walter Rethel, it was a biplane of standard construction. The lower wing was larger than the upper wing, which was necessary for the full-span flaps to be effective, although this negatively impacted the effectiveness of the ailerons on the upper wing. While the Rolls-Royce Kestrel selected to initially power the new aircraft, it was less powerful than the BMW VI of the preceding Ar 65 yet the Ar 68 was predicted to be faster due to its lower weight and aerodymanic improvements. Construction of a single prototype commenced in 1933.

There were no major changes in construction between the different Ar 68 models, comprising steel tubing and a metal-plated exterior from the cockpit forwards, while the sides and underside of the fuselage were covered by fabric. While the winds and empennage control surfaces were also clad in fabric, metal plating covered the tailplane and fin. Armament consisted of a pair of 7.92 mm (0.312 in) MG 17 machine guns, although some aircraft were furnished with a compact bomb bay capable of accommodating up to six10 kg SC 10 fragmentation bombs. The minimisation of tension cables and the fuselage shape gave the Ar 68 as relatively elegant appearance.

Into flight
Performing its maiden flight in early 1934, the Ar 68 quickly proved to possess admirable handling characteristics, being fairly maneouverable yet not prone to spinning. Chief of the Technical Office Ernst Udet personally made an early flight in the aircraft, during which he outperformed a Heinkel He 51 in a mock dogfight. Despite this favourable outcome, some officials expressed concerns about the unforgiving nature of such a high-performance aircraft, to the extent that production of Ar 68 was allegedly nearly cancelled entirely.

The Ar 68 competed with the somewhat similar He 51, the first prototypes of each aircraft even adopted the same BMW VI powerplant, albeit with different installation arrangements. While the first and fourth Ar 68 prototypes was powered by the BMW VI, the second, third, and fifth prototypes were powered by the newly-developed Junkers Jumo 210 inverted V12 engine, which provided substantially greater high altitude performance than either the Kestrel or BMW VI. Despite its performance advantages, limited availability of the Jumo 210 led to the Ar 68's early production run making use of the BMW VI instead.

By April 1936, Arado had planned for a total production run of 324 Ar 68s, 302 of which were delivered prior to the year's end. By 31 March 1938, 514 aircraft had been completed, at which point the production line was shuttered. Quantity production had not been entirely without complications; the planned Ar 68G model was cancelled due to the unavailability of a suitable engine.

The Ar 68 entered service with the Luftwaffe in early 1936; one of the first units to receive the type was stationed in East Prussia. One early event that involved two squadrons equipped with the type was the Remilitarization of the Rhineland in March 1936. During 1938, it was decided to dispatch Ar 68s with the Condor Legion to fight in the Spanish Civil War, where it was outclassed by the Soviet Polikarpov I-16. Arado responded by upgrading the engine of the Ar 68E, which soon became the Luftwaffe's most widely used fighter in 1937–1938, before being replaced by the Messerschmitt Bf 109. The last Ar 68s served as night fighters up to the winter of 1939–1940,. Several Ar 68E-1s served with 10. and 11. (Nachtjagd)/JG 72, and a few Ar 68F-1s with 10. (Nachtjagd)/JG 53 after which they served as fighter-trainers until 1944.

Variants
Data from: ''Prototype V suffix style
 * Ar 68V1
 * Prototype, powered by a 492 kW BMW VI engine. First flight in 1934.


 * Ar 68a (D-IKIN)
 * First prototype. 1 x 478 kW BMW VId V-12.


 * Ar 68b (D-IVUS)
 * Second prototype. 1 x 455 kW Jumo 210A inverted V-12.


 * Ar 68c (D-IBAS)
 * Third prototype. 1 x 455 kW Jumo 210A inverted V-12.


 * Ar 68d (D-ITAR)
 * Fourth prototype. 1 x 478 kW BMW VId V-12.


 * Ar 68V4
 * The fourth prototype (Ar 68d), redesignated after the Reichsluftfahrtministerium (RLM/German Aviation Ministry) introduced the standardised Versuchs (research) number system.


 * Ar 68e (D-ITEP)
 * Fifth prototype. 1 x 507 kW Jumo 210Da inverted V-12.


 * Ar 68V5
 * The fifth prototype (Ar 68e), redesignated after the RLM introduced the standardised Versuchs (research) number system.


 * Ar 68E
 * First type to enter Luftwaffe service, powered by a 455 kW Junkers Jumo 210Ea, at sea level for 5 minutes, 500 kW at 3,800 m.


 * Ar 68F
 * Interim production, powered by a BMW VI 7.3Z; 559 kW) at sea level for 1 minute, 410 kW) at 1,000 m, awaiting supply of Jumo 210 engines.


 * Ar 68G
 * Abortive attempt to fit a supercharged 500 kW BMW VI.


 * Ar 68H (D-ISIX)
 * Only a single prototype was built, powered by a 634 kW) BMW 132Da nine-cylinder supercharged air-cooled radial. It had two additional machine guns in the upper wing and had an enclosed cockpit, the first Arado aircraft to be so treated.

Operators

 * undefined
 * Luftwaffe
 * undefined
 * Spanish Air Force