Arado Ar 234


The Arado Ar 234 Blitz was the world's first operational jet-powered bomber, built by the German Arado company in the closing stages of World War II.
Produced in limited numbers it was used almost entirely in the reconnaissance role. In its few uses as a bomber it proved to be nearly impossible to intercept. It was the last Luftwaffe aircraft to fly over the UK during the war, in April 1945.

Design and development

Background

In late 1940, the Reich Air Ministry offered a tender for a jet-powered high-speed reconnaissance aircraft with a range of. Arado was the only company to respond, offering their E.370 project, led by Professor Walter Blume. This was a high-wing conventional-looking design with a Junkers Jumo 004 engine under each wing.
Arado estimated a maximum speed of at, an operating altitude of and a range of. The range was short of the RLM request, but they liked the design and ordered two prototypes as the Ar 234. These were largely complete before the end of 1941, but the Jumo 004 engines were not ready, and would not be ready until February 1943. 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.
By September, four prototypes were flying. The second prototype, Arado Ar 234 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, killing pilot Flugkapitän Selle. The eight prototype aircraft were fitted with the original arrangement of trolley-and-skid landing gear, intended for the planned operational, but never-produced Ar 234A version.

The sixth and eighth of the series were powered with four BMW 003 jet engines instead of two Jumo 004s, the sixth having four engines housed in individual nacelles, and the eighth flown with two pairs of BMW 003s installed within "twinned" nacelles underneath each wing. These were the first four-engine jet aircraft to fly. The twin-Jumo 004 powered Ar 234 V7 prototype made history on 2 August 1944 as the first jet aircraft ever to fly a reconnaissance mission, flown by Erich Sommer.

Landing gear design challenges

The projected weight for the aircraft was approximately. To reduce the weight of the aircraft and maximize the internal fuel, Arado did not use the typical retractable landing gear. Instead, the aircraft was to take off from a jettisonable three-wheeled, tricycle gear-style trolley known as a Bugradstartwagen and land on three retractable skids, one under the central section of the fuselage, and one under each engine nacelle. This central main skid beneath the fuselage was originally intended to fully retract into the fuselage with skid-bay doors enclosing it, and was originally shown in a 1942-dated Arado engineering drawing, under its overall 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 mainskid, for ground contact purposes. However, as with the operational Messerschmitt Me 163B rocket fighter which used a landing skid, it was discovered that such a skid-format landing gear for the Ar 234A design's prototypes did not allow mobility after the end of the landing run, which would have left aircraft scattered widely over an airfield's acreage, unable to taxi off the runway without remounting every aircraft on a trolley for towing off the landing area. Erich Sommer himself once noted for late 20th-century television that the landing skid-equipped prototypes, when touching down on a wet-turf airstrip, had a landing run characteristic that "was like greased lightning" and "like soap", from the complete lack of braking capability of the landing skid system.

Ar 234B

The RLM had already seen the promise of the design and in July had asked Arado to supply two prototypes of a Schnellbomber version as the Ar 234B. Since the original skid-equipped Ar 234A's fuselage design was very slender and filled with fuel tanks, there was no room for an internal bomb bay and the bombload had to be carried on external racks.
Since the cockpit was directly in front of the fuselage, the pilot had no direct view to the rear, so the guns were aimed through a periscope, derived from the type used on German World War II tanks, mounted on the cockpit roof. The defensive fixed rear gun system intended for the Ar 234A's prototype series was generally considered useless – much like similar rearward-firing, fuselage mount guns placed on the fuselage of the first five prototypes of the Heinkel He 219 night fighter – and such fixed, rearwards-mount machine guns were omitted in production examples of the Ar 234B, while still retaining the periscope for rearwards vision. The external bombload, and the aforementioned presence of inactive aircraft littering the landing field after their missions were completed made the skid-landing system impractical, so the B version was modified to have fully retractable tricycle landing gear, with the mid-fuselage very slightly widened to accommodate the forward-retracting main gear units, the nosegear retracting rearwards. The ninth prototype, marked with Stammkennzeichen PH+SQ, was the prototype Ar 234B, and flew on 10 March 1944.
Production B-series aircraft were slightly wider at mid-fuselage to house the main landing gear, with a central fuel tank present in the mid-fuselage location on the eight earlier trolley/skid equipped prototype aircraft having to be deleted for the retracted main gear's accommodation. The 1942-executed engineering drawing of the trio of fuel tanks in the fuselage, when using a skid/trolley undercarriage design, showed a 1,430-litre forward tank, the aforementioned central tank of some 830 litres capacity, and an aft tank of 1,540 litres capacity. - the V9 and later examples had enlarged forward and aft fuel tanks to compensate for the omitted 830-litre central fuel tank. Under tests with maximum bombload consisting of three SC 500 bomb, the Ar 234 V9 aircraft could reach at. This was still better than any bomber the Luftwaffe had at the time, and made it the only bomber with any hope of surviving the massive Allied air forces. The normal bombload consisted of two 500 kg bombs suspended from the engines or one large 1,000 kg bomb semi-recessed in the underside of the fuselage with maximum bombload being 1,500 kg. If the war had continued it is possible that the aircraft would have been converted to use examples of the FuG 203 Kehl MCLOS radio guidance transmitter system to deploy and control one Henschel Hs 293 air-to-surface missile, itself weighing some 1,045 kg. The Hs 293 would have needed to be lengthened by 300 mm and be suspended at an angle in order to provide sufficient ground clearance. It could also carry the heavier BT 1400, although ground clearance would be very limited. In case the BT 1400 ordnance was to be deployed on an Ar 234B for an operational sortie, fuel had to be reduced, and the jettisonable Starthilfe Walter liquid-fueled rocket booster pods needed to be used for 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, 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. Meanwhile, several of the Ar 234 prototypes - including a few of the surviving six twin-engined Jumo 004-powered "trolley-and-skids" Ar 234A-series prototypes - were sent forward in the reconnaissance role. In most cases, it appears they were never even detected, cruising at about at over, with the seventh prototype achieving the first-ever wartime reconnaissance mission over the United Kingdom by a Luftwaffe-used jet aircraft.
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 search for a solution led to improved training as well as the use of twin HWK-built, jettisonable liquid fueled monopropellant Starthilfe pioneering RATO units, one mounted under each outer wing. The Jumo 004 engines were always the real problem; they suffered 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. 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 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, as was already happening to Messerschmitt Me 262 jet fighters. Most simply sat on the airfields awaiting fuel that never arrived.
Overall from mid-1944 until the end of the war a total of 210 aircraft were built. In February 1945, production was switched to the C variant. It was hoped that by November 1945 production would reach 500 per month.
In addition, it was intended to modify upwards of 30 Ar 234B-2 airframes for the night-fighting role, from a proposal dated 12 September 1944 between Arado director Walter Blume and Goering's top aviation technologist, Siegfried Knemeyer. Designated Ar 234B-2/N and code named Nachtigall, these aircraft 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 MG 151/20 autocannon within a Magirusbombe conformal gun pod on the ventral fuselage hardpoint. A second crew member, who operated the radar systems, was accommodated in a very cramped compartment in the rear fuselage. Two of these jury-rigged night fighters served with Kommando Bonow, an experimental test unit attached to Luftflotte Reich. Operations commenced with the pair of 234Bs in March 1945, but Bonow's team soon found the aircraft to be unsuited for night fighting and no kills were recorded during the unit's very brief life.

Ar 234C

The Ar 234C was equipped with four lighter-weight BMW 003A engines, mounted in a pair of twin-engine nacelles based on those from the eighth Ar 234 prototype. The primary reason for this switch was to free up the 720 kg weight Junkers Jumo 004s for use by the Me 262, but the change improved overall thrust to nearly 3.2 tonnes 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, also used a much-simplified window design with far fewer glazing panels, than the total of 13 separate glazing panels of the Ar 234B cockpit – itself taken almost unmodified in form from the eight A-series "trolley-skid" prototypes – for ease of production. The quartet of BMW jet engines gave the C-series Ar 234s an airspeed that was found to be about 20% higher than the twin-Jumo 004 equipped B series airframes, and the faster climb to altitude meant more efficient flight and increased range.
Although Hauptmann Diether Lukesch was preparing to form an operational test squadron, only 14 C-series airframes had been completed by the war's end, and of that number fewer than half had been fitted with engines, with a few of them found at the end of the war sitting out in the open, otherwise complete but with empty engine nacelles – only about 500 examples of the BMW 003 jet engine were ever built, with priority for their production going to the Heinkel He 162A Spatz emergency fighter's own production program. 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 Heinkel HeS 011 jets for flight, while others were intended to feature swept or "crescent"-type wings.

Ar 234D

The D model was a two-seat aircraft based on the B-series fuselage, but with a new, enlarged two-seat cockpit possessing fewer glazing panels than the C version, intended to be 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 for test purposes, and no 234D was produced, beyond a few wooden engineering mockups.

Ar 234P

The P model was 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.

Variants

Data from: Aircraft of the Third Reich Vol.1
;Arado E 370:Draft proposal submitted to the Reichsluftfahrtministerium for a fast jet reconnaissance bomber.
;Ar 234 V1 to V5: Initial prototypes of the Ar 234A with skid landing gear, take-off tricycle gear trolley with trio of retractable landing skids, and 2 x Jumo 004 engines.
;Ar 234 V6 & V8:Prototypes for four-engined designs for the Ar 234, meant to use the alternative choice of the lower-thrust BMW 003 turbojet engines while retaining the A model skid/trolley undercarriage. The V6 was fitted with the quartet of BMW 003s in individual nacelles, unlike the V8 prototype which had the BMW jet engines in a pair of "twinned" nacelles, and essentially "prototyped" what would become the four-engined Ar 234C's engine installation.
;Ar 234 V7:Development aircraft for the Ar 234B production aircraft, retaining the A-series' intended skid undercarriage, and saw active service.
;Ar 234 V9 to V11:Representative prototypes of the Ar 234B production aircraft, with the V9 being the first retractable tricycle-geared airframe.
;Ar 234 V13 & V20:A pair of B-series prototypes fitted with quartets of the BMW 109-003 engines for the C-series aircraft, using the V8 prototype's "twinned" nacelle design, without the V8 example's retractable wing-skids.
;Ar 234 V15: A single B-series airframe fitted with 2 x BMW 003 engines for engine development testing, and rumored to have been considered for new wing planform tests.
;Ar 234 V21 to V30:C-series development aircraft. V26 and V30 had experimental thick section wooden and thin section metal laminar flow wings.
;Ar 234 V16:Intended to be fitted with an experimental crescent wing with sweep back lessening towards the tips, evolved by Rüdiger Kosin and Walther Lehmann. The wing was constructed but was destroyed before it could be fitted.
;Ar 234 A:The first proposed production reconnaissance bomber fitted with skid undercarriage and take-off tricycle gear trolley, built only as the series of eight trolley-and-skid undercarriage V1 through V8 prototypes.
;Ar 234 B-0: 20 pre-production aircraft.
;Ar 234 B-1: Reconnaissance version, equipped with two Rb 50/30 or Rb 75/30 cameras. No serial production, all reconnaissance variants were converted from B-2 aircraft with Rüstsatz b.
;Ar 234 B-2: Bomber version, with a maximum bombload of 1,500 kg.
;Ar 234 B-2/N: Night fighter version, two aircraft converted from B-2.
;Ar 234 C-1: Four-engined aircraft - all C-series Ar 234s powered with a quartet of BMW 003 jet engines - as installed on the Ar 234 V8 prototype, otherwise similar to the Ar 234 B-1.
;Ar 234 C-2: Four-engined aircraft similar to the Ar 234 B-2.
;Ar 234 C-3: Multi-purpose version, armed with two 20 mm MG 151/20 cannons beneath the nose.
;Ar 234 C-3/N: Proposed two-seat night fighter version, armed with two forward-firing 20 mm MG 151/20 and two 30 mm MK 108 cannons, fitted with a mid-VHF band FuG 218 Neptun V radar.
;Ar 234 C-4: Armed reconnaissance version, fitted with two cameras, armed with four 20 mm MG 151/20 cannon.
;Ar 234 C-5: Proposed version with side-by-side seating for the crew. The 31st prototype was converted into this variant.
;Ar 234 C-6: Proposed two-seat reconnaissance aircraft. The 32th prototype was converted into this variant.
;Ar 234 C-7: Night fighter version, with side-by-side seating for the crew, fitted with an enhanced FuG 245 Bremen O cavity magnetron-based centimetric radar.
;Ar 234 C-8: Proposed single-seat bomber version, powered by two 1,080 kg Jumo 004D turbojet engines.
;Ar 234 D-1: Proposed reconnaissance version. Not built.
;Ar 234 D-2: Proposed bomber version. Not built.
;Ar 234 P-1 : Two-seater with four BMW 003A-1 engines; one 20 mm MG 151/20 and one 30 mm MK 108.
;Ar 234 P-2 : Also a two-seater, with redesigned cockpit protected by a 13 mm armour plate.
;Ar 234 P-3: HeS 011A powered P-2, but with two cannon.
;Ar 234P-4: as P-3 but with Jumo 004D engines.
;Ar 234P-5: Three-seat version with HeS 011A engines, one 20 mm MG 151/20 and four 30 mm MK 108 cannon.
;Ar 234 R: Rocket-powered short range high-altitude reconnaissance version It had a rocket engine in its tail, while the turbojets had been discarded. It would be towed by a He 177 to 8 km altitude after which it would propel itself to 17 km altitude over the target after which it would glide back unpowered. Project only.
;Ar 234 Berlin N: Two-engined aircraft, this was a wind tunnel test aircraft based on Ar 234 B-2 with Berlin N radar installed on top.

Operators

Only one Ar 234 survives today. The aircraft is an Ar 234 B-2 bomber variant carrying Werknummer 140312, and was one of nine Ar 234s surrendered to British forces at Sola Airfield near Stavanger, Norway. The aircraft had been operating with 8. Staffel III./Kampfgeschwader 76 during the final weeks of the war, having operated previously with the 8th squadron, carrying the full-four-character Geschwaderkennung military code of "F1+GS" on the fuselage sides, with the wing code of "F1" painted on in a much reduced size for sanctioned, late-war "low-visibility" requirements.
This aircraft and three others were collected by "Watson's Whizzers" of the USAAF to be shipped to the United States for flight testing. Two aircraft were given freely but a further two had been traded to Watson by Eric "Winkle" Brown in exchange for an interview with Hermann Göring who was then being held by the Americans.
The aircraft was flown from Sola to Cherbourg on 24 June 1945 where it joined 34 other advanced German aircraft shipped back to the U.S. aboard the British aircraft carrier. Reaper departed from Cherbourg on 20 July, arriving at Newark, New Jersey eight days later. Upon arrival two of the Ar 234s were reassembled and flown by USAAF pilots to Freeman Army Airfield, Indiana for testing and evaluation. 140312 was assigned the foreign equipment number FE-1010. The fate of the second Ar 234 flown to Freeman Field remains a mystery. One of the remaining two was reassembled by the United States Navy at Naval Air Station Patuxent River, Maryland, for testing, but was found to be in unflyable condition and was scrapped.
After receiving new engines, radio and oxygen equipment, 140312 was transferred to Wright Field near Dayton, Ohio and delivered to the Accelerated Service Test Maintenance Squadron of the Flight Test Division in July 1946. Flight testing was completed on 16 October 1946 though the aircraft remained at Wright Field until 1947. It was then transferred to Orchard Place Airport in Park Ridge, Illinois, and remained there until 1 May 1949 when it, and several other aircraft stored at the airport were transferred to the Smithsonian Institution. During the early 1950s, the Ar 234 was moved to the Smithsonian's Paul Garber Restoration Facility at Suitland, Maryland for storage and eventual restoration.
The Smithsonian began restoration of 140312 in 1984 and completed it in February 1989. All paint had been stripped from the aircraft before the Smithsonian received it, so the aircraft was painted with the markings of an aircraft of 8./KG 76, the first operational unit to fly the "Blitz". The restored aircraft was first displayed at the Smithsonian's main museum building in downtown Washington D.C. in 1993 as part of a display titled "Wonder Weapon? The Arado Ar 234". In 2005 it became one of the first aircraft moved to the new Steven F. Udvar-Hazy Center near Dulles International Airport. Today, 140312 is displayed next to the last surviving Dornier Do 335, an aircraft that accompanied it on its voyage across the Atlantic Ocean aboard the Reaper over 60 years earlier.
This aircraft is displayed with a pair of Hellmuth Walter designed, liquid-fueled Starthilfe RATO units mounted under its wings. These World War II-era German liquid fueled RATO units may be the only surviving examples to be mounted on an aircraft design that actually used them during the war.

Specifications (Ar 234B-2)