As with many German aircraft, the availability of suitable engines seriously impacted development and production.
2-engined Ar 232A What would become the Ar 232 originated from a
tender offered by the
Reichsluftfahrtministerium (RLM/German Aviation Ministry) issued during late 1939 which sought a replacement for the ubiquitous Ju 52/3m transport. Both Arado and
Henschel 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/B radial engines, 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 a
cantilever mid-wing smooth-skinned
monocoque 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, possess
short takeoff and landing (STOL) capabilities, and permit rapid loading and unloading times.
Engine discussion — parallel development Following a review of the competing aircraft, Arado's design was selected over Henschel's, leading to the company receiving an initial order for three
prototypes in 1940. However, the desired power plant for the Ar 232 was challenged by the
Focke-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, the
BMW Bramo 323 Fafnir nine-cylinder radial engine, weighing roughly 550 kg (1,210 lbs) each, from Focke-Wulf's
Fw 200 land-based
maritime 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 the
Ar 232A with the original BMW 801, while the third and a newly ordered fourth prototype were designated as the
Ar 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 the
Stammkennzeichen alphabetic codes GH+GN and VD+YB respectively, were completed in early 1941 and commenced trials shortly after. The first flight suffered a partial
landing 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 stuck
oleo strut, which was too short when fully extended, and was rectified via the insertion of a ring. 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. A further ten pre-production aircraft were constructed; these saw operational used as the
Ar 232A-0 while awaiting production versions.
4-engined Ar 232B 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. The extra weight of the Bramo 323 engines also moved the
center 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 the
Ar 232B-0, and were used widely in an operational role. However, this was the only order for the design, as the
Luftwaffe 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.
Ar 432 Various improvements to the Ar 232 were planned, such as the replacement of the outer wing sections and control surfaces with wooden versions to conserve
aluminium. Originally to be known as the
Ar 232C, the design effort was protracted and was later redesignated the
Ar 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. Two even larger planned versions, the
Ar 532 and the
Ar 632, would have almost doubled the wingspan to 60 m (196 ft 10 in), as large as Germany's six-engined
BV 238 flying boat design, and added another two engines. An
amphibian transport, the
Ar 430, was also projected for use in the
Mediterranean. ==Design==