Tests with the Arado Ar 234 prototypes dem- onstrated that straight wings retained their good aerodynamic characteristics only at speeds below 800 kph. Near-supersonic flights demanded a completely new approach to wing geometry. On 9th December 1942 two Arado company engineers, Rüdiger Kosin and Walter Lehmann, patented a crescent shaped wing, which had its sweep and chord decreasing from root to tip. In mid-1944 Kosin decided to use his wing design on the Arado 234.
Five variants of the wing were built, designated Versuchsflügel I through V, each differing in its sweep. Nevertheless, none of them was used in practice. The most advanced work on this project was carried out at Dedelsdorf airbase, where the Ar 234 V16 was being re-built as part of this research. The aircraft was destroyed in mid-April 1945 by advancing British troops as they captured the airfield.
Another role to be fulfilled by the Ar 234 was that of high-altitude interceptor. A design was prepared accordingly based on the four-engined Ar 234C-3 equipped with a pressurized cockpit. Its technical description was finalised on 21st March 1944 and delivered to the RLM on 20th May 1944. The aircraft was to be armed with two forward-facing 20 mm MG 151/20 cannons and two additional cannons of the same type mounted on either side of the front lower part of the cockpit. Its primary role would have been to engage Allied escort fighters with height advantage to force them to jettison their auxiliary fuel tanks and lead them away from their charges. This would allow the conventional fighters, Bf 109s and Fw 190s, supported by jet powered Me 262s, to take on the four-engined bombers. Another role for the Ar 234C high-altitude interceptors was to hunt down Mosquito bomber and reconaissance machines, which hitherto had been flying their solo missions with a fair degree of impunity. However, at this late stage of the war the project remained on the drawing boards only. The same fate was shared by the ‘destroyer’ variant, which was to be powered by two Heinkel HeS 11 A-1 with a thrust rating of 1300 kg (12,84 kN) at sea level. The Heinkel powerplants, however, were under-developed and highly unreliable.
In the summer of 1944, the RLM had become interested in converting the Ar 234 into a jet night fighter. In September 1944, Obstlt. Siegfried Knemeyer, in cooperation with Arado engineer Walter Blume, set to work. The new variant was to feature the Ar 234B-2 airframe. The rear fuselage, which in the reconnaissance variant housed the photographic cameras, was rebuilt to make room for a second crewmember who would operate the FuG 218 Neptun airborne radar. The armament comprised two 20 mm MG 151/20 cannons mounted in a ventral pod called a Magirusbombe. The night fighter version was christened ‘Nachtigall’ (“Nightingale”).
The prototype, a rebuilt series-production Ar 234B-2 (WNr. 140 145, SM+FE), was first flown in November 1944. After a few flights the aircraft was damaged during landing and it was not repaired until early December 1944. On 10th December 1944 the machine performed a 25-minute flight in order to check out the radar equipment. Shortly afterwards another Ar 234B-2 (WNr. 140 146) was converted into a night fighter. However, on the night of 17th December 1944, a series-production Ar 234B-2 (WNr. 140 150, SM+FJ) was flown by Oblt. Kurt Welter. At that time he was the CO of 10./NJG 11, a night fighter unit equipped with Messerschmitt 262 jets. Welter’s opinion of the Ar 234 as a night fighter was unfavourable. The extensively glazed cockpit refracted light, occasionally blinding the pilot. The lack of frontal armor endangered the pilot’s life, both in the case of return fire from a bomber and when a pilot had to fly through after-explosion debris. Despite Welter’s criticism, tests of the night fighter version continued. On the night of 13th February 1945, the first prototype (WNr. 140 145) crashed and both members of the crew, Hptm. Josef Bisping (pilot) and Hptm. Albert Vogl (radio operator), were killed. On 1st March 1945 another ace from the Luftwaffe’s night fighter arm, Oblt. Kurt Bonow, arrived at Oranienburg. He flew a dozen or so sorties in WNr. 140 146, attempting to intercept the elusive British Mosquitos. At the same time, Kommando Bonow was formed with three aircraft of the Ar 234B-2/N variant on strength. Nevertheless, by the end of the war the unit had failed to score a single victory.
During operations it became apparent that the FuG 218 antennas produced considerable drag, which decreased the aircraft’s speed. Furthermore, the resultant increased fuel consumption limited the combat worthiness of the Ar 234B-2/N.
In addition to the improvised night fighter adaptations of the Ar 234B-2, there were plans to produce a dedicated night fighter based on the four-engined Ar 234C-3. Two prototypes, the V23 and V27 were to be converted to represent Ar 234C-3/Ns fitted with a radar operator station and a ventral pod with twin 30 mm Mk 108 cannons. However, neither of the two prototypes was completed.