Arado Ar 232
Encyclopedia
The Arado Ar 232 Tausendfüssler (German
: "Millipede") was the first truly modern 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 October 1941-flown Junkers Ju 252
trimotored transport via its Trapoklappe); a high 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was interested in replacing or supplementing its fleet of outdated Junkers Ju 52/3m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.
ed by the Reichsluftfahrtministerium
(German Air Ministry, RLM) in late 1939 for a replacement for the Ju 52/3m transport. Both Arado and Henschel
were asked for rear-loading designs powered by two 1,193 kW (1,600 hp) BMW 801A/B
radial engine
s, which was just entering prototype production and not currently used on any front-line designs. The Arado design beat out Henschel's after an examination of the plans, and an order for three prototype
s was placed in 1940.
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 would use 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 tail control 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. This 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 rocket assist (RATO
) for take-off, and either parachute
s or reverse RATO for landing.
The most noticeable feature of the Ar 232 was the landing gear
. Normal operations from prepared runway
s used a tricycle gear
, but the strut
s could "break", or kneel, after landing to place the fuselage closer to the ground and thereby reduce the ramp angle. An additional set of ten smaller twinned wheels per side supported the aircraft once the primary gear was "broken", 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 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 into the engine nacelle
s, while the support wheels remained extended and the nose wheel only semi-retracted.
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.
project had been earmarked to use the BMW 801A/B, and was proving to be a capable design. Production of the BMW 801 was insufficient to supply this new demand, and the Ar 232 was forced to use another engine. Eventually, the BMW
Bramo 323
from the Junkers Ju 352
was selected instead, as it was already in production and could meet requirements if the Ar 232 really did replace the Ju 52/3m in service. The prototypes were far enough along that switching engines would have seriously delayed the program, so the first two were to be completed as the Ar 232A, and the third and a newly ordered fourth as the Ar 232B. The third and fourth prototypes (and all production aircraft) used four engines (in place of the two specified in the RLM specification) in order to provide the desired performance.
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 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.
The Ar 232B program ran at the same time. With four 895 kW (1,200 hp) Bramo 323s, power increased from 2,386 kW (3,200 hp) to 3,580 kW (4,800 hp), solving the A model'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 engines also moved the center of gravity
forward, which was offset by extending the cargo area rearward another meter.
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.
Plans were also made to replace the outer wing sections and control surfaces with wooden versions to conserve then-limited supplies of aluminium
. Originally to be known as the Ar 232C, the design dragged on and was later re-named the Ar 432. Plans were finally put into place to start production in October 1945, but the war ended 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) and added another two engines.
Two of the B-0s were captured by British
forces at the end of the war. After test flights by Eric "Winkle" Brown, who gave the design excellent marks, they were used by the Royal Air Force
on flights between England and Germany after the war.
German language
German is a West Germanic language, related to and classified alongside English and Dutch. With an estimated 90 – 98 million native speakers, German is one of the world's major languages and is the most widely-spoken first language in the European Union....
: "Millipede") was the first truly modern cargo aircraft
Cargo aircraft
A cargo aircraft is a fixed-wing aircraft designed or converted for the carriage of goods, rather than passengers. They are usually devoid of passenger amenities, and generally feature one or more large doors for the loading and unloading of cargo...
, designed and built in small numbers by the German
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
firm Arado Flugzeugwerke
Arado Flugzeugwerke
Arado Flugzeugwerke was a German aircraft manufacturer, originally established as the Warnemünde factory of the Flugzeugbau Friedrichshafen firm, that produced military hydroplanes during the First World War.-History:...
during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
. 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
Fuselage
The fuselage is an aircraft's main body section that holds crew and passengers or cargo. In single-engine aircraft it will usually contain an engine, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage which in turn is used as a floating hull...
slung beneath a high wing; a rear loading ramp (that had first appeared on the October 1941-flown Junkers Ju 252
Junkers Ju 252
-References:* Green, William. Warplanes of the Third Reich. New York:Doubleday, 1972. ISBN 0-385-05782-2.-External links:* *...
trimotored transport via its Trapoklappe); a high tail
Empennage
The empennage , also known as the tail or tail assembly, of most aircraft gives stability to the aircraft, in a similar way to the feathers on an arrow...
for easy access to the hold; and various features for operating from rough fields. Although the Luftwaffe
Luftwaffe
Luftwaffe is a generic German term for an air force. It is also the official name for two of the four historic German air forces, the Wehrmacht air arm founded in 1935 and disbanded in 1946; and the current Bundeswehr air arm founded in 1956....
was interested in replacing or supplementing its fleet of outdated Junkers Ju 52/3m
Junkers Ju 52
The Junkers Ju 52 was a German transport aircraft manufactured from 1932 to 1945. It saw both civilian and military service during the 1930s and 1940s. In a civilian role, it flew with over 12 air carriers including Swissair and Deutsche Luft Hansa as an airliner and freight hauler...
transports, it had an abundance of types in production at the time and did not purchase large numbers of the Ar 232.
Design
The Ar 232 design resulted from a tender offerTender offer
Tender offer is a corporate finance term denoting a type of takeover bid. The tender offer is a public, open offer or invitation by a prospective acquirer to all stockholders of a publicly traded corporation to tender their stock for sale at a specified price during a specified time, subject to...
ed by the Reichsluftfahrtministerium
Reich Air Ministry
thumb|300px|The Ministry of Aviation, December 1938The Ministry of Aviation was a government department during the period of Nazi Germany...
(German Air Ministry, RLM) in late 1939 for a replacement for the Ju 52/3m transport. Both Arado and Henschel
Henschel & Son
Henschel & Son was a German company, situated in Kassel, best known during the 20th century as a maker of transportation equipment, including locomotives, trucks, buses and trolleybuses, and armoured fighting vehicles and weapons....
were asked for rear-loading designs powered by two 1,193 kW (1,600 hp) BMW 801A/B
BMW 801
The BMW 801 was a powerful German air-cooled radial aircraft engine built by BMW and used in a number of German military aircraft of World War II. The engine's cylinders were in two rows of seven cylinders each, the bore and stroke were both 156 mm , giving a total capacity of 41.8 litres...
radial engine
Radial engine
The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders point outward from a central crankshaft like the spokes on a wheel...
s, which was just entering prototype production and not currently used on any front-line designs. The Arado design beat out Henschel's after an examination of the plans, and an order for three prototype
Prototype
A prototype is an early sample or model built to test a concept or process or to act as a thing to be replicated or learned from.The word prototype derives from the Greek πρωτότυπον , "primitive form", neutral of πρωτότυπος , "original, primitive", from πρῶτος , "first" and τύπος ,...
s was placed in 1940.
Wilhelm van Nes led the design of the Ar 232. He began at the cargo area, with a bay directly behind the "stepless cockpit
Cockpit
A cockpit or flight deck is the area, usually near the front of an aircraft, from which a pilot controls the aircraft. Most modern cockpits are enclosed, except on some small aircraft, and cockpits on large airliners are also physically separated from the cabin...
" 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 would use a side-mounted door for access, but the Ar 232 used hydraulically powered clamshell-doors on the rear of the bay with a ramp
Inclined plane
The inclined plane is one of the original six simple machines; as the name suggests, it is a flat surface whose endpoints are at different heights. By moving an object up an inclined plane rather than completely vertical, the amount of force required is reduced, at the expense of increasing the...
to allow cargo to be rolled into the hold. The tail control 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. This 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
Flap (aircraft)
Flaps are normally hinged surfaces mounted on the trailing edges of the wings of a fixed-wing aircraft to reduce the speed an aircraft can be safely flown at and to increase the angle of descent for landing without increasing air speed. They shorten takeoff and landing distances as well as...
" 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 rocket assist (RATO
JATO
JATO is an acronym for jet-fuel assisted take off. It is a system for helping overloaded aircraft into the air by providing additional thrust in the form of small rockets....
) for take-off, and either parachute
Parachute
A parachute is a device used to slow the motion of an object through an atmosphere by creating drag, or in the case of ram-air parachutes, aerodynamic lift. Parachutes are usually made out of light, strong cloth, originally silk, now most commonly nylon...
s or reverse RATO for landing.
The most noticeable feature of the Ar 232 was the landing gear
Undercarriage
The undercarriage or landing gear in aviation, is the structure that supports an aircraft on the ground and allows it to taxi, takeoff and land...
. Normal operations from prepared runway
Runway
According to ICAO a runway is a "defined rectangular area on a land aerodrome prepared for the landing and take-off of aircraft." Runways may be a man-made surface or a natural surface .- Orientation and dimensions :Runways are named by a number between 01 and 36, which is generally one tenth...
s used a tricycle gear
Tricycle gear
Tricycle gear describes an aircraft undercarriage, or landing gear, arranged in a tricycle fashion. The tricycle arrangement has one wheel in the front, called the nose wheel, and two or more main wheels slightly aft of the center of gravity...
, but the strut
Strut
A strut is a structural component designed to resist longitudinal compression. Struts provide outwards-facing support in their lengthwise direction, which can be used to keep two other components separate, performing the opposite function of a tie...
s could "break", or kneel, after landing to place the fuselage closer to the ground and thereby reduce the ramp angle. An additional set of ten smaller twinned wheels per side supported the aircraft once the primary gear was "broken", or could be used for additional support when landing on soft or rough airfields. The aircraft was intended to be capable of taxiing
Taxiing
Taxiing refers to the movement of an aircraft on the ground, under its own power, in contrast to towing or push-back where the aircraft is moved by a tug...
at low speeds on its 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 into the engine nacelle
Nacelle
The nacelle is a cover housing that holds engines, fuel, or equipment on an aircraft. In some cases—for instance in the typical "Farman" type "pusher" aircraft, or the World War II-era P-38 Lightning—an aircraft's cockpit may also be housed in a nacelle, which essentially fills the...
s, while the support wheels remained extended and the nose wheel only semi-retracted.
Normally operated by a crew of four, the pilot
Aviator
An aviator is a person who flies an aircraft. The first recorded use of the term was in 1887, as a variation of 'aviation', from the Latin avis , coined in 1863 by G. de la Landelle in Aviation Ou Navigation Aérienne...
was the only member without two roles. The navigator
Navigator
A navigator is the person on board a ship or aircraft responsible for its navigation. The navigator's primary responsibility is to be aware of ship or aircraft position at all times. Responsibilities include planning the journey, advising the Captain or aircraft Commander of estimated timing to...
operated a 13 mm (.51 in) MG 131 machine gun
MG 131 machine gun
The MG 131 was a German 13 mm caliber machine gun developed in 1938 by Rheinmetall-Borsig and produced from 1940 to 1945...
in the nose, the radio operator
Radioman
Radioman was a rating for United States Navy and United States Coast Guard enlisted personnel, specializing in communications technology.-History of the rating:...
a 20 mm MG 151 cannon
MG 151 cannon
The MG 151 was a 15 mm autocannon produced by Waffenfabrik Mauser starting in 1940. It was in 1941 developed into the 20 mm MG 151/20 cannon which was widely used on many types of German Luftwaffe fighters, fighter bombers, night fighters, ground attack and even bombers as part of or as...
in a rotating turret on the roof, and the loadmaster
Loadmaster
A Loadmaster is an aircrew member on military transport aircraft. Loadmasters serve in the Air Force, Marines, Coast Guard and Navy of many nations...
a 13 mm (.51 in) MG 131 machine gun
MG 131 machine gun
The MG 131 was a German 13 mm caliber machine gun developed in 1938 by Rheinmetall-Borsig and produced from 1940 to 1945...
firing rearward from the extreme rear of the cargo bay above the cargo doors.
Development
Even before the prototypes were complete in 1941, the Focke-Wulf Fw 190Focke-Wulf Fw 190
The Focke-Wulf Fw 190 Würger was a German Second World War single-seat, single-engine fighter aircraft designed by Kurt Tank in the late 1930s. Powered by a radial engine, the 190 had ample power and was able to lift larger loads than its well-known counterpart, the Messerschmitt Bf 109...
project had been earmarked to use the BMW 801A/B, and was proving to be a capable design. Production of the BMW 801 was insufficient to supply this new demand, and the Ar 232 was forced to use another engine. Eventually, the BMW
BMW
Bayerische Motoren Werke AG is a German automobile, motorcycle and engine manufacturing company founded in 1916. It also owns and produces the Mini marque, and is the parent company of Rolls-Royce Motor Cars. BMW produces motorcycles under BMW Motorrad and Husqvarna brands...
Bramo 323
Bramo 323
-References:NotesBibliography* Gunston, Bill. World Encyclopedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9* Jane's Fighting Aircraft of World War II. London. Studio Editions Ltd, 1989. ISBN 0-517-67964-7...
from the Junkers Ju 352
Junkers Ju 352
-References:...
was selected instead, as it was already in production and could meet requirements if the Ar 232 really did replace the Ju 52/3m in service. The prototypes were far enough along that switching engines would have seriously delayed the program, so the first two were to be completed as the Ar 232A, and the third and a newly ordered fourth as the Ar 232B. The third and fourth prototypes (and all production aircraft) used four engines (in place of the two specified in the RLM specification) in order to provide the desired performance.
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 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.
The Ar 232B program ran at the same time. With four 895 kW (1,200 hp) Bramo 323s, power increased from 2,386 kW (3,200 hp) to 3,580 kW (4,800 hp), solving the A model'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 engines also moved the center of gravity
Center of gravity of an aircraft
The center-of-gravity is the point at which an aircraft would balance if it were possible to suspend it at that point. It is the mass center of the aircraft, or the theoretical point at which the entire weight of the aircraft is assumed to be concentrated. Its distance from the reference datum is...
forward, which was offset by extending the cargo area rearward another meter.
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.
Plans were also made to replace the outer wing sections and control surfaces with wooden versions to conserve then-limited supplies of aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
. Originally to be known as the Ar 232C, the design dragged on and was later re-named the Ar 432. Plans were finally put into place to start production in October 1945, but the war ended 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) and added another two engines.
Two of the B-0s were captured by British
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
forces at the end of the war. After test flights by Eric "Winkle" Brown, who gave the design excellent marks, they were used by the Royal Air Force
Royal Air Force
The Royal Air Force is the aerial warfare service branch of the British Armed Forces. Formed on 1 April 1918, it is the oldest independent air force in the world...
on flights between England and Germany after the war.
Variants
- Ar 232 V1 & V2 - Ar 232A prototypes and research aircraft, powered by two BMW801 engines.
- Ar 232 V3 & V4 - Ar 232B prototypes and research aircraft, powered by four Bramo 323 Fafnir engines.
- Ar 232A - Pre-production aircraft used for operational trials, powered by two BMW801 engines.
- Ar 232B - The first production aircraft powered by four Bramo 323 Fafnir engines, only ten built as Ar 232B-0.
- Ar 232C - A redesigned version using wood for outer wing sections and control surfaces.
- Ar 432 - The planned production version of the Ar 232C, re-named.
- Ar 532 - Planned enlarged six-engined version of the Ar 432.
- Ar 632 - Planned enlarged six-engined version of the Ar 432.