| Ar 232 | |
|---|---|
 Arado Ar 232B-0 | |
| General information | |
| Type | Transport |
| National origin | Germany |
| Manufacturer | Arado Flugzeugwerke |
| Primary user | Luftwaffe |
| Number built | ~20 |
| History | |
| Introduction date | 1943 |
| First flight | June 1941 |
| Retired | 1945 |
TheArado Ar 232Tausendfüßler (German: "Millipede"), sometimes also calledTatzelwurm, was acargo aircraft that was designed and produced in small numbers by the German aircraft manufacturerArado Flugzeugwerke. It was designed during the first half of theSecond World War in response to a request by theReichsluftfahrtministerium (German Air Ministry, RLM) for a successor or supplemental transport aircraft to theLuftwaffe's obsolescentJunkers Ju 52/3m. The Ar 232 introduced, or brought together, almost all of the features now considered to be standard in modern cargo transport aircraft designs, including a box-likefuselage slung beneath ahigh wing; a rear loading ramp (that had first appeared on the December 1939-flownJunkers Ju 90 V5 fifth prototype four-engined transport via itsTrapoklappe), a high-mountedtwin tail for easy access to the hold and features for operating from rough fields. It was initially requested to be powered by a pair ofBMW 801A/Bradial engines, but instead fourBMWBramo 323 engines were used due to a lack of capacity.
The first twin-engine prototype performing itsmaiden flight in June 1941, while the first four-engine prototype followed roughly one year later. The type demonstrated clear performance advantages over the Ju 52/3m and limited pre-production orders were placed, leading to roughly 20 aircraft being constructed. The envisioned mass production of the Ar 232 was never attained, primarily due to Germany having an abundance of transport aircraft in production and thus it did not purchase large numbers of Ar 232s. Several aircraft did see operational use, to aid wartime production efforts and on the front line. Arado's design team continued to work on refinements, including economy measures and the enlarged six-engined Ar 632 variant. At one point, German officials expected quantity production of the type to be attained in October 1945 but the war ended instead. Two Ar 232s were captured by the British and operated for a time between England and Germany following the conflict.
As with many German aircraft, the availability of suitable engines seriously impacted development and production.
What would become the Ar 232 originated from atender offered by theReichsluftfahrtministerium (RLM/German Aviation Ministry) issued during late 1939 which sought a replacement for the ubiquitous Ju 52/3m transport. Both Arado andHenschel were requested to design a rear-loading aircraft that was to be powered by a pair of 1,193 kW (1,600 hp)BMW 801A/Bradial engines,[1] which was just entering prototype production and not currently used on any front-line designs. Arado's design team was headed by the aeronautical engineer Wilhelm van Nes. The basic configuration selected was that of acantilever mid-wing smooth-skinnedmonocoque design with a spacious cargo area that was as low to the ground as feasibly possible. Furthermore, the aircraft was to be relatively robust and capable of operating from austere airstrips and rough terrain, possessshort takeoff and landing (STOL) capabilities, and permit rapid loading and unloading times.[2]
Following a review of the competing aircraft, Arado's design was selected over Henschel's, leading to the company receiving an initial order for threeprototypes in 1940. However, the desired power plant for the Ar 232 was challenged by theFocke-Wulf Fw 190 project, which also used the same BMW 801A/B engine. Production of the BMW 801 was insufficient to fulfil all of the prospective demands, thus Arado was compelled to adopt an alternative engine for the Ar 232. Eventually, theBMWBramo 323Fafnir nine-cylinder radial engine, weighing roughly 550 kg (1,210 lbs) each, from Focke-Wulf'sFw 200 land-basedmaritime patrol aircraft was selected as the alternate powerplant. The Bramo 323 was in mass production and could meet requirements if the Ar 232 entered quantity service. The prototypes were far enough along that switching engines would have delayed the program, thus the first two aircraft were to be completed as theAr 232A with the original BMW 801, while the third and a newly ordered fourth prototype were designated as theAr 232B. The third and fourth prototypes, and subsequent production aircraft, used four Bramo 323 engines in order to provide the desired performance.
The first two prototypes, bearing theStammkennzeichen alphabetic codes GH+GN and VD+YB[3] respectively, were completed in early 1941 and commenced trials shortly after. The first flight suffered a partiallanding gear failure during landing; while the nose gear collapsed, the twenty-two "millipede wheels" saved the aircraft from damage. The cause was determined to be a stuckoleo strut, which was too short when fully extended, and was rectified via the insertion of a ring.[4]
The general performance of the Ar 232 exceeded the Ju 52/3m in multiple respects; it carried roughly double the load over longer distances, operated from shorter runways and rougher fields if need be, and cruised about 70 km/h (44 mph) faster.[5] A further ten pre-production aircraft were constructed; these saw operational used as theAr 232A-0 while awaiting production versions.
The Ar 232B program proceeded in parallel to this effort. With the quartet of 895 kW (1,200 hp) Bramo 323s replacing the twin BMW 801s, each Bramo 323 with its aforementioned 550 kg dry weight apiece; power increased from 2,386 kW (3,200 hp) to 3,580 kW (4,800 hp), solving the Ar 232A's problem of having little excess power in case of engine failure. This change also required the wing to be extended slightly, the span increasing just over 3 m (9 ft 10 in) in total.[6] The extra weight of the Bramo 323 engines also moved thecenter of gravity forward, which was offset by stretching the cargo area rearward another meter, expanding the cargo capacity it could carry internally.
During May 1942, the first of the two four-engined prototypes, V3, performed its maiden flight. A further 10 aircraft were then ordered as theAr 232B-0, and were used widely in an operational role. However, this was the only order for the design, as theLuftwaffe gave transport aircraft production a relatively low priority. Many of those aircraft produced were used by Arado to transport aircraft parts between its factories, and did not see front-line service.
Various improvements to the Ar 232 were planned, such as the replacement of the outer wing sections and control surfaces with wooden versions to conservealuminium.[7] Originally to be known as theAr 232C, the design effort was protracted and was later redesignated theAr 432. During June 1944, plans were finally put into place to start production in October 1945, but the conflict came to an end without even a prototype being produced.[8] Two even larger planned versions, theAr 532 and theAr 632, would have almost doubled the wingspan to 60 m (196 ft 10 in), as large as Germany's six-enginedBV 238 flying boat design, and added another two engines. Anamphibian transport, theAr 430, was also projected for use in theMediterranean.[9]
The Ar 232 was a multi-engined transport aircraft. It was normally operated by a crew of four, of which thepilot was the only member without two roles. Thenavigator also operated a 13 mm (.51 in)MG 131 machine gun in the nose, while theradio operator could also use a 20 mmMG 151 cannon in a rotating turret on the roof, and theloadmaster was provisioned with a 13 mm (.51 in)MG 131 machine gun that fired rearward from the extreme rear of the cargo bay above the cargo doors.[4]The aircraft could be outfitted with various auxiliary kits to suit certain operational circumstances, such as winter/tropical kits, a radio set, a rubberliferaft, an oil-burning heater, and an emergency power unit.[4]
The cargo bay of the Ar 232, which was directly behind the aircraft's "steplesscockpit", was 6.6 m (21 ft 7¾ in) long, 2.3 m (7 ft 6½ in) wide and 2.0 m (6 ft 6¾ in) high. Unlike typical designs of the era that used a side-mounted door for access, the Ar 232 was furnished withhydraulically powered clamshell-doors on the rear of the bay with aramp, which permitted cargo to be rolled into the hold. Thetwin tail configuration tail surfaces were mounted on the end of a long boom to keep the area behind the doors clear so trucks could drive right up to the ramp, much like the 1944-era AmericanFairchild C-82 Packet of a differingtwin boom fuselage configuration. The high-set tail on its "pod-and-boom" configuration fuselage allowed the Ar 232 to be loaded and unloaded faster than other designs. An overhead crane was installed within the cargo bay to assist this process.[4]
The Ar 232 was furnished with a three-piece twin-spar wing, comprising all-through rectangular centrepiece that was attached to a pair of trapezoidal outer wings, each accommodatingself-sealing fuel tanks and the mainlanding gear.[4] The entire rear surface of the wing incorporated Arado's own "travelling flap" design to achieve excellent short-field performance; these flaps were electronically actuated and interconnected with theailerons. Further measures to reduce the landing distance included adrogue parachute and rockets.[4] Even when loaded to 16,000 kg (35,270 lb), the Ar 232 could take off in 200 m (656 ft); this was in part achieved via aboundary layer control system. The take-off distance could be further reduced via the use ofStarthilfe liquid fuelled monopropellant rocket assist (RATO) jettisonable propulsion units.[4]
Perhaps the most noticeable feature of the Ar 232 was the landing gear. Normal operations from preparedrunways used atricycle gear — a then-novel feature for German military aircraft—but the sideways-retracting main gear's lever-action loweroleo strut suspended arm – carrying the main gear's wheel/tire unit at the bottoms of the maingears'struts could "break", or kneel, after landing to place the fuselage closer to the ground and thereby reduce the ramp angle. An additional set of eleven smaller, non-retractable twinned wheels per side, mounted along the ventral centreline of the fuselage from just behind the semi-retractable nosewheel aftwards to just forward of the wing's trailing edge, supported the aircraft once the main landing gear's lever-action lower arm had "knelt", or could be used for additional support when landing on soft or rough airfields.[4] The aircraft was intended to be capable oftaxiing at low speeds on its row of small wheels, thus being able to negotiate small obstacles such as ditches up to 1.5 m (5 ft) in width. The appearance of the row of small wheels led to the nickname "millipede". In flight, the main legs fully retracted inwards into the wings, while the fixed support wheels remained exposed and the nose wheel only semi-retracted, with the nosewheel tire's lowest point while retracted never going above the lowest point of the 22 auxiliary centre-line wheels' tires.[10]
German officials intended for the aircraft to be used in a wide variety of circumstances, specific mentions includingNorth Africa and theArctic.[4]
In late 1942, in response to the deteriorating situation of theWehrmacht's6th Army during theBattle of Stalingrad, it was decided to deploy the first two Ar 232 prototypes to theEastern Front for the purpose of delivering critical supplies and airlifting casualties.[11]
The first prototype was promptly lost along with its entire crew after the pilot became disoriented. The second prototype was more successful, completing multiple missions in January 1943, typically flying in and out of Stalingrad unhindered. Its crew occasionally opted to avoid airfields when enemy forces were known to be waiting in ambush, instead landing on rough terrain, a feat that would have been impossible for most transport aircraft of its size at the time.[12]
On 17 July 1943, a twin-engined Ar 232 flew fromBrandenburg, Germany toBanak, Norway, the northernmost airport in Europe; the flight, which delivered automated weather apparatus, necessitated the fitting ofauxiliary fuel tanks. One month later, the aircraft was lost with all onboard due to a single engine failure shortly after take off followed by a collision with terrain.[13]
Outside of conventional military logistics, the Ar 232 found numerous uses; Arado made frequent use of the type to transport high priority aviation components.[6]
At least five Ar 232s are believed to have been operated byKampfgeschwader 200, a secretive special operations unit of the Luftwaffe.[14] Multiple attempts using Ar 232s were made to infiltrate covert agents behindSoviet lines, including a mission under remit of the top secretOperation Zeppelin which intended to assassinateJoseph Stalin in late 1944.[15]
Starting in December 1944, several Ar 232 were directed to fly supplies to a supposed pocket of German military personnel active behind Soviet lines. Despite such flights continuing for months, this effort was entirely fruitless as it was anNKVD deception operation, known asOperation Scherhorn.[15]
Two Ar 232 B-0s were captured by British forces towards the end of the conflict. Multiple test flights of these aircraft were performed byEric "Winkle" Brown, who reportedly gave the aircraft an excellent report. Subsequently, they were operated for a time by theRoyal Air Force on flights between England and Germany as late as 1946.[7]
Data fromDie Deutsche Luftrüstung 1933–1945 Vol.1 – AEG-Dornier[16][17]
General characteristics
Performance
Armament
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