Arado Ar 234

In late 1940, the Nazi Ministry of Aviation offered a tender for a jet-powered high-speed reconnaissance aircraft with a range of 2,156 km (1,340 mi). Arado was the only company to respond, offering their E.370 project, led by Professor Walter Blume.[2] This was a high-wing conventional-looking design with a Junkers Jumo 004 engine under each wing.

Arado estimated a maximum speed of 780 km/h (480 mph) at 6,000 m (20,000 ft), an operating altitude of 11,000 m (36,000 ft) and a range of 1,995 km (1,240 mi). The range was short of the Ministry's specification, but two prototypes were ordered as the Ar 234. These were largely complete before the end of 1941, but the Jumo 004 engines were not ready until February 1943.[2] When they did arrive they were considered unreliable by Junkers for in-flight use and were cleared for static and taxi tests only. Flight-qualified engines were finally delivered, and the Ar 234 V1 made its first flight on 30 July 1943 at Rheine airfield.[3]

The second prototype, V2, crashed on 2 October 1943 at Rheine near Münster after suffering a fire in its port wing, failure of both engines, and various instrumentation failures. The aircraft dived into the ground from 1,200 m (3,900 ft), killing the pilot.[4] The eight prototype aircraft were fitted with the trolley-and-skid landing gear intended for the never-produced Ar 234A version.

Differences between the pair of four-engined Ar 234 prototype aircraft

The sixth and eighth in the series were powered by four BMW 003 jet engines instead of two Jumo 004s; the sixth had the four engines in individual nacelles,[5] while the eighth had the engines in "twinned" nacelles underneath each wing. A 1942 engineering drawing of the E 370 showed a 1,430-litre (378 US gal) forward tank, 830 litres (219 US gal) central tank in mid-fuselage, and an aft tank of 1,540 litres (407 US gal) capacity.[6] These were the first four-engined jet aircraft to fly. The twin-Jumo 004 powered Ar 234 V7 prototype made history on 2 August 1944 as the first jet aircraft used for a reconnaissance mission, flown by Erich Sommer.[7]

The projected weight for the aircraft was approximately 8 tonnes (7.9 long tons; 8.8 short tons). To reduce weight and maximize the internal fuel, Arado did not use retractable landing gear. Instead, the aircraft was to take off from a jettisonable tricycle gear-style trolley[8] (known as a nosewheel takeoff-carriage in English, as described in an Ar 234A Typenblatt factory drawing for the V8 prototype) and land on three retractable skids, one under the central section of the fuselage and one under each engine nacelle. The main skid, beneath the fuselage, was originally intended to fully retract, and was originally shown in a 1942-dated engineering drawing, under the E 370 airframe factory development designation, as intended to be made from a three-sided channel-section component, featuring a set of nine triple-beaded wooden rollers within the channel-section main skid.[9] However, this landing gear did not allow aircraft to move after the landing run, which would have left aircraft scattered over an airfield, unable to taxi off the runway. Erich Sommer said that landing the skid-equipped prototypes on a wet grass airstrip "was like greased lightning" and "like [landing on] soap", due to the complete lack of braking capability.[10]

In July, the Ministry of Aviation had asked Arado to supply two prototypes of a fast bomber version as the Ar 234B. The Ar 234A's fuselage design was very slender and filled with fuel tanks, leaving no room for an internal bomb bay, so the bombload had to be carried on external racks. This, too, made the skid landing system impractical.

The nose of the Arado Ar 234 B-2 variant was made up of thirteen individual panels.

The cockpit was at the front of the fuselage, and the pilot had no direct view to the rear, so the rear firing guns were aimed through a periscope, (derived from the type used on tanks) mounted on the cockpit roof. The defensive fixed rear gun system intended for the prototype series was generally considered useless and was omitted in the Ar 234B, which retained the periscope. The B version also had fully retractable tricycle landing gear, which retracted forward into the mid-fuselage; the nosegear retracted rearwards. The ninth aircraft, radio code letters PH+SQ, was the prototype Ar 234B, and first flew on 10 March 1944. It, and production B-series aircraft, were slightly wider at mid-fuselage to house the main landing gear, and the central fuel tank was removed for the same reason, with enlarged forward (1,800-litre/476 US gal) and aft (2,000-litre/528 US gal) fuel tanks to compensate.[11]

Under tests with a maximum bombload of three SC 500 bombs, the V9 could reach 672 km/h (418 mph) at 5,000 m (16,000 ft),[12] faster than any other Luftwaffe bomber at the time. The normal bomb load consisted of two 500 kg (1,100 lb) bombs suspended from the engines or one large 1,000 kg (2,200 lb) bomb semi-recessed in the underside of the fuselage, with maximum bombload being 1,500 kg (3,310 lb). It could also carry the heavier BT 1400 (1,510 kg unpowered bomb-torpedo), although ground clearance was limited. If this was deployed, fuel had to be reduced, and rocket assistance used to aid takeoff.

Production lines were already being set up, and 20 B-0 pre-production aircraft were delivered by the end of June. Later production was slow, as the Arado plants were given the simultaneous tasks of producing aircraft from other bombed-out factories hit during the USAAF's "Big Week",(20-25 February 1944) against the German aircraft industry and the ongoing license-building and nascent phasing-out of Heinkel's heavy He 177A bomber, even as the Arado firm was intended to be the sole subcontractor for the He 177B-series strategic bomber, meant to start construction at Arado as early as October 1944.[13] Meanwhile, several of the Ar 234 prototypes - including a few of the surviving six Ar 234A-series prototypes - were sent forward in the reconnaissance role. In most cases, it appears they were never even detected, cruising at about 740 km/h (460 mph) at over 9,100 m (29,900 ft), with the seventh prototype achieving the first reconnaissance mission over the United Kingdom by a Luftwaffe jet.

The few 234Bs entered service in autumn and impressed their pilots. They were fairly fast and completely aerobatic. The long takeoff runs led to several accidents. A quest for a solution led to improved training as well as the use of twin jettisonable liquid fuel Starthilfe rocket assisted takeoff units, one under each outer wing. The Jumo 004 engines had constant flameouts and required overhaul or replacement after about 10 hours of operation.

The most notable use of the Ar 234 in the bomber role was the attempt to destroy the Ludendorff Bridge at Remagen.[14] Between 7 March, when it was captured by the Allies, and 17 March, when it finally collapsed, the bridge was continually attacked by Ar 234s of III/KG 76 carrying 1,000 kg (2,200 lb) bombs. The aircraft continued to fight in a scattered fashion until Germany surrendered on 8 May 1945. Some were shot down in air combat, destroyed by flak, or "bounced" by Allied fighters during takeoff or on the landing approach[lower-alpha 1]. Most simply sat on the airfields awaiting fuel that never arrived.

From mid-1944 until the end of the war a total of 210 aircraft were built.[2] In February 1945, production was switched to the C variant. It was hoped that by November 1945 production would reach 500 per month.

Ar 234B-2/N night fighter adaptation

In addition, some Ar 234 B-2 airframes were modified to serve as night fighters.[15] Designated Ar 234B-2/N and code named Nachtigall (Nightingale), these were fitted with FuG 218 "Neptun" VHF-band radar, with the appropriately reduced-dipole length version of the standard Hirschgeweih eight-dipole element, VHF-band transceiving AI radar antenna system, and carried a pair of forward-firing 20mm MG 151/20 autocannon within a Magirusbombe conformal gun pod on the rear fuselage hardpoint. A second crew member, who operated the radar systems, was accommodated in a cramped compartment in the rear. Two of these jury-rigged night fighters served with Kommando Bonow, an experimental test unit attached to Luftflotte Reich. Operations commenced in March 1945, but the unit found the aircraft unsuitable for night fighting and no kills were recorded.

Two-view silhouette of basic Ar 234C design

The Ar 234C was equipped with four lighter weight (at 625 kg/1,380 lb apiece) BMW 003A engines mounted in a pair of twin-engine nacelles based on those from the eighth prototype. The primary reason for this switch was to free up the Junkers Jumo 004s for use by the Me 262, but the change improved overall thrust to nearly 3.2 tonnes (7,040 lbf) with all four BMW jets at full takeoff power, especially useful for takeoff and climb-to-altitude performance. An improved cockpit design, with a slightly bulged outline for the upper contour integrating a swept-back fairing for the periscope, used a simplified window design with fewer glazed panels[lower-alpha 2] for ease of production. The four BMW jet engines gave about 20% greater airspeed than the B series airframes, and the faster climb to altitude meant more efficient flight and increased range.

Although an operational test squadron was being prepared, only 14 C-series airframes had been completed by the end of the war, of which fewer than half had engines. Some were found at the end of the war sitting in the open, complete but for empty engine nacelles.[lower-alpha 3] Comprehensive flight testing of the new sub-type had yet to begin when Germany surrendered. Three basic variants of the C-series were planned for initial construction, with several more laid out as detailed proposals. Some of these would have had a pair of the higher thrust, but heavier[lower-alpha 4] Heinkel HeS 011 jet engines, while others were intended to feature swept or "crescent"-type wings.

The D model was intended to be a two-seat aircraft based on the B-series fuselage, but with an enlarged cockpit using fewer glazing panels than the C version, powered by a pair of more powerful Heinkel HeS 011 turbojet engines. The HeS 011 powerplant never reached quantity production, with only 19 examples of the new powerplants ever created. No 234D was produced, only a few wooden engineering mockups.

The P model was intended to be a two-seat night fighter version with a variant of the D-series cockpit, differing in powerplant options and several options of radar. Several were in the planning stage, but none made it into production.

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