The Arado Ar 232 Tausendfüßler (German: "Millipede"), sometimes also called Tatzelwurm, was a cargo aircraft, designed and built in small numbers by the German firm Arado Flugzeugwerke during World War II. The design introduced, or brought together, almost all of the features now considered to be standard in modern cargo transport aircraft designs, including a box-like fuselage slung beneath a high wing; a rear loading ramp (that had first appeared on the December 1939-flown Junkers Ju 90 V5 fifth prototype four-engined transport via its Trapoklappe); a high-mounted twin tail for easy access to the hold; and various features for operating from rough fields. Although the Luftwaffe was interested in replacing or supplementing its fleet of outdated Junkers Ju 52/3m transports, it had an abundance of types in production at the time, and did not purchase large numbers of the Ar 232. The first two prototypes, bearing the Stammkennzeichen alphabetic codes GH+GN and VD+YA respectively, started trials in early 1941. The first flight resulted in the collapse of the nose gear, but the twenty-two "millipede wheels" saved the aircraft from damage. A further ten pre-production machines were built, and were used operationally as the Ar 232A-0 while awaiting production versions. In general, the Ar 232 completely outperformed the Ju 52/3m. 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. Two four-engined prototypes were ordered, the V3 and V4, and V3 first flew in May 1942. A further 10 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 very low priority. Many of those produced were used by Arado to transport aircraft parts between its factories, and did not see front-line service. Wilhelm van Nes led the design of the Ar 232. He began at the cargo area, with a bay directly behind the "stepless cockpit" that 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. Typical designs of the era used a side-mounted door for access, but the Ar 232 used hydraulically powered clamshell-doors on the rear of the bay with a ramp to allow cargo to be rolled into the hold. The twin 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 American Fairchild C-82 Packet of a differing twin 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. For short-field performance, the Ar 232 incorporated Arado's own "travelling flap" design for the entire rear surface of the wing. Even loaded to 16,000 kg (35,270 lb), it could take-off in 200 m (656 ft). This distance could be further reduced by using Starthilfe liquid fuelled monopropellant rocket assist (RATO) jettisonable propulsion units for take-off. Normally operated by a crew of four, the pilot was the only member without two roles. The navigator operated a 13 mm (.51 in) MG 131 machine gun in the nose, the radio operator a 20 mm MG 151 cannon in a rotating turret on the roof, and the loadmaster a 13 mm (.51 in) MG 131 machine gun firing rearward from the extreme rear of the cargo bay above the cargo doors. Landing gear design innovations The most noticeable feature of the Ar 232 was the landing gear. Normal operations from prepared runways used a tricycle gear — a then-novel feature for German military aircraft—but the sideways-retracting main gear's lever-action lower oleo-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. The aircraft was intended to be capable of taxiing 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.
