Arado Ar 233

Nazi Germany (1942)
Amphibious Multipurpose Transport – 1 Incomplete Mockup Built

The 1:10 model of the Ar 233. [Dan Sharp]

The Arado Ar 233 was an amphibious passenger transport seaplane designed in 1942, a time when it seemed Germany would soon complete its conquest of Europe and conclude the Second World War. Intended for civilian use after the war, the development of the Ar 233 was cancelled due to the deteriorating war situation for Germany in 1944. As the project was deemed low priority, much of the Ar 233’s advanced design work was done in the German Military Administration in France by the Société Industrielle Pour l’Aéronautique (SIPA) aircraft firm located within the Northern German administrative zone. The Ar 233 never materialized, but an incomplete mockup was constructed along with a 1:10 scale model. The incomplete mockup, along with blueprints and notes, were captured by the Free French Forces shortly after the Liberation of France. However, the Ar 233 was not further developed by the French, unlike quite a few of the German aircraft projects undertaken and captured in France. Relatively unknown and often overlooked, the Ar 233 is an interesting obscure project to provide an alternate-history post-war Germany with a suitable transport plane.

History

A cutaway drawing of the Ar 233 in its passenger configuration. [Dan Sharp]

The first couple years of the Second World War appeared to have been going firmly in favor of Germany. Most of Western Europe had been conquered by then, and the Wehrmacht was making steady progress in its advance eastwards to conquer the Soviet Union. Despite recently declaring war on the United States, a distant economic powerhouse, Germany still seemed confident in its path to triumph. This feeling was prominent amongst the Germans throughout the initial years of the war. As such, some aircraft firms began to make preparations for post-war German civil aviation early in 1940, in accordance with a request made by the Reichsluftfahrtministerium (RLM / Ministry of Aviation). A few examples of aircraft designed for future German civil use are the Focke-Wulf Fw 206 and Blohm & Voss BV 144. The Arado firm was not exempt from partaking in civil aircraft design and responded with a two engine float plane design.

Designed as a passenger transport, the project began around August within the Arado firm bearing the designation “E 430”. Two variants were originally envisioned, a Bramo 323 R2 powered seaplane model capable of transporting ten passengers and a smaller Argus Ar 204 powered amphibian floatplane (capable of operating from land and water) able to transport eight passengers. According to the RLM, the project officially began in October 1942, but this was likely when it was submitted or approved to the RLM. Work on the project most certainly began in August due to the amount of preliminary steps required. This is further backed up by interviews with former French aircraft designers. As the German mainland’s industry was mostly reserved for military production, the industry of occupied France (German Military Administration in France) seemed like an acceptable place to offload this low priority project. As such, the Arado firm made arrangements for the German-controlled French Société Industrielle Pour l’Aéronautique (SIPA) aircraft firm to assist in the design and production of the E 430. The SIPA firm was founded by Émile Dewoitine in 1938 after his previous firm Constructions Aéronautiques Émile Dewoitine was nationalized. It would appear that, between October and December of 1942, the E 430 project gained the designation Ar 233.

In addition to the update in nomenclature, the smaller As 204 powered E 430 “Amphibium” was cancelled in favor of the ten passenger seaplane. However, the amphibious characteristic of the former was integrated into the Ar 233. Soon after, the French SIPA firm began work on producing a full-scale mockup. The SIPA factory in Île de la Jatte, Neuilly-Sur-Seine, West of Paris, was responsible for the the mockup while the other office at 27/29 Rue Dupont (also in Neuilly-Sur-Seine) and the Dewoitine Design office in 11 Rue de Pillet-Will in Paris were responsible for other work. By Christmas Eve of 1942, it would appear that a large portion of the mockup was completed as the Arado firm released a brochure advertising the Ar 233 which featured images of the mockup. The brochure made mention of four projected Ar 233 variants which included the original passenger airliner, a flying ambulance, a private luxury touring aircraft, and a cargo transport. The French effort in the design work and mockup construction went unrecognized, as all French involvement in the project were omitted from the brochure. However, close examination of a few photos in the brochure shows some of the equipment labelled in German and French.

A wind tunnel model of the Ar 233. The bulge beneath the wing is a extendable float. [Dan Sharp]

Further on, it would appear that a 1:10 scale model of the Ar 233 was constructed along with a set of propellers. They were tested separately until May 1943 apparently, when they were paired together and sent to the Nationaal Luchtvaart Laboratorium (NLL / National Aviation Laboratory) facility in Amsterdam, Occupied Netherlands. Other than this model, not much more work appeared to have been done on the Ar 233. This was likely due to the disaster at Stalingrad, when the German 6th Army suffered a catastrophic defeat, and Germany’s ensuing effort to focus on their military industry. Nonetheless, the project remained stagnant for the remainder of 1943 and was finally cancelled in 1944 in favor of military aircraft. When the Allied forces and Free French Forces liberated France, it seems that the mockup and quite a lot of notes and design prints were captured. It does not appear that the French furthered the Ar 233 project after the war unlike quite a lot of the other German projects conducted in France, such as the Heinkel He 274 bomber or Blohm & Voss BV 144 airliner.

A rear view of the Ar 233 mockup which shows the port side entrance hatch. [Dan Sharp]

In the end, the ill-fated Ar 233 did not progress beyond the mockup and wind tunnel testing stage, although the project was meant to be a capable amphibious seaplane which could operate in all weathers including the extremes in the North Pole and the Tropical regions. The aircraft also had the luxury of being operable from both land and sea. This also would allow the aircraft to operate in underdeveloped regions which did not have adequate airfields. It also would have made emergency landings safer as calm water surfaces would allow for less dangerous landings compared to rough land terrain.

Design

The incomplete Ar 233 mockup in the workshop of the French firm SIPA, near the outskirts of Paris. [Dan Sharp]

The Ar 233 was an amphibious seaplane intended to be powered by two 9-cylinder air-cooled Bramo 323 MA radial engines producing 968 hp each. Each engine would be driven by a three blade propeller which would be started electrically via an onboard generator. The generator would also power the onboard radio systems (FuG X P, FuG 101 and FuBl II F) and a fan to provide ventilation. The Ar 233’s crew consisted of a pilot and a radio operator, though a co-pilot could join the crew. The Ar 233 had four variants which would have the passenger capacity vary. For ease of transport, the Ar 233 was designed so that it could be taken apart and transported via the railroad system.

A rear view of the Ar 233 mockup’s cockpit which shows the pilot and copilot’s seat. Note the hatch in the middle which gives access to the forward passenger luggage compartment. [Dan Sharp]

The pilot’s compartment consisted of three seats for a pilot, a co-pilot or passenger and a radio operator. An extra set of controls could be installed for a co-pilot in longer range flights or to train pilots. The cockpit could be accessed via a ladder that folded to the underside of the wing. The side windows in the cockpit could be opened by sliding them forward, while the forward windows could be dropped forward to the bow section. An emergency manual pump was located next to the co-pilot’s seat that could be used to remove water. Visibility from the cockpit appears to be inadequate due to the lack of downwards visibility. Rear visibility also seems to be lacking.

The fuselage of the Ar 233 was a ship-hull shaped in order to allow floating on water surfaces. The fuselage was divided into several sections which, in order from front to end, were the nose wheel compartment, forward baggage compartment, pilot’s cockpit, landing gear hatch, passenger compartment, rear baggage compartment and a washroom fitted with a toilet. Lighting in the passenger compartment was provided by ceiling lights which were powered by a generator. Two air ventilation fans were also provided, with one above the entrance and the other in the land gear shaft. The left side of the fuselage had a door which allowed passengers to enter. The entrance door opened both upwards and downwards, with the latter being able to act as a platform. An emergency exit was provided on both sides, as the middle window in the fuselage could open. The tail of the Ar 233 was designed so that it curved upwards in order to protect the control surfaces by preventing unnecessary contact with the water.

A three-view drawing of the Ar 233 along with it’s basic dimensions. [Dan Sharp]

In the passenger airliner configuration, the aircraft could carry eight passengers and two crew members. The seats provided in the passenger compartment were fitted with armrests, side tables, seatbelts, lamps and small luggage nets. The luxury touring configuration only allowed four seats (including the pilot). It would also have had two extra 400 L fuel tanks near the wing edge to extend the range. The cargo transport configuration would carry no passengers and had all seats in the passenger compartment removed for cargo. Any cargo would be loaded through hatches on the fuselage side and would have equipment to secure cargo in flight. In the ambulance configuration, beds could be fitted in the passenger compartment for the wounded.

There would be two wheeled landing gears which would be extendable from the side of the hull for land-based operations. Each one of these wheel measured at 39.96 x 14.96 in / 1,015 x 380 mm. These landing gears, when retracted, remained above the waterline and were hydraulically operated. The nose wheel (width measured at 33.74 x 12.79 in / 875 x 325 mm) sat at the front of the aircraft and could retract into a watertight compartment that could expel excess water with compressed air. If needed, a crewmember could climb above the nose compartment and lift the lid on top to perform maintenance. It was also provided with a locking mechanism. Additionally, the nose wheel’s suspension strength allowed it to perform takeoff and landings at altitudes up to 4,900 ft / 1,500 m.

The Ar 233 was designed so that it could be transported via rail. This blueprint drawing shows the transport configuration. [Dan Sharp]

The “V” shaped gull wings that sat on top of the fuselage provided a suitable platform for the engines and propellers, as it allowed them to be mounted at a safe distance from the water. Just behind the engine cowls were a set of hydraulically extended floats for assistance with landing on water. The fuel tanks for the engines were located in the wing leading edge in three “densely riveted” containers. These fuel tanks would be refilled by climbing on top of the cockpit via an access ladder. In addition, hydraulically operated flaps were provided to aid the Ar 233 in landing. These flaps were designed to yield in rough water conditions to reduce damage.

In terms of excess equipment, the Ar 233 could carry a fog horn, rubber dinghy, boat hook, towing gear, ropes, detachable sun canopy, emergency food and water, emergency tools, both ground and sea anchors and various other materials.

Variants

E 430 (Bramo 323 R2) – Original design concept which saw a dedicated seaplane powered by two Bramo 323 R2 radial engines and capable of transporting ten people. This design was further developed by incorporating the amphibious characteristic of the E 430 “Amphibium”. This design was later improved upon and bore the designation Ar 233.
E 430 Amphibium (Argus Ar 402) – Original design concept developed beside the E 430 which saw a scaled down variant powered by Argus Ar 402 engines and capable of carrying eight passengers. This variant could be operated from land and water due to it’s amphibious characteristics. This variant was cancelled but its amphibious design was carried onto the E 430.
Ar 233 (Commercial Airliner) – Commercial airliner design based on the original E 430 design which would be capable of carrying ten people. A pilot and radio operator were part of the crew which allowed for eight passengers. In addition, a co-pilot could be in the crew at the expense of a passenger. Two baggage compartments (located in the hull in front of the cockpit but behind the nose wheel and behind the passenger compartment) and a toilet compartment (located behind the rear baggage compartment) were provided for the passengers. Powered by two 9-cylinder air-cooled Bramo 323 MA radial engines.
Ar 233 (Luxury Touring Aircraft) – Luxury touring variant intended for sightseeing in remote areas. This variant featured four seats (including the pilot). This variant had the choice of carrying two extra fuel tanks at 400 L each in the outer wings. The envisioned range was 1,120 mi / 1,800 km. This variant also had the choice of implementing an additional set of controls for a co-pilot. It is not known if this variant would retain the two baggage compartments and toilet. Powered by two 9-cylinder air-cooled Bramo 323 MA radial engines.
Ar 233 (Cargo Transport) – Cargo transport variant which saw the removal of the passenger compartment equipment for cargo. The aircraft in this configuration appeared to been capable of carrying up to 2,200 lb / 1,000 kg of cargo. The cargo would be loaded from doors on the side of the fuselage with equipment provided to secure the cargo. The two baggage compartments and toilet were definitely removed for space. Powered by two 9-cylinder air-cooled Bramo 323 MA radial engines.
Ar 233 (Flying Ambulance) – Flying ambulance variant which envisioned the possibility of placing four beds in the passenger compartment either for the wounded or for the passengers. This variant was mentioned as the E 430 Flying Ambulance in the Ar 233 brochure, which shows the variant still maintained the original designation. It is not known if this variant would retain the two baggage compartments and toilet. Powered by two 9-cylinder air-cooled Bramo 323 MA radial engines.

Operators

Nazi Germany – The German Arado design firm was the original designer and intended to develop the Ar 233 for use with Lufthansa, the Luftwaffe and other organizations. The project was cancelled in 1944 after Allied forces liberated France.
German Military Administration in France – The SIPA firm under German control was responsible for partially designing and building the Ar 233. All three of SIPA’s facilities appeared to have been working on the project.
Free France – The Free French Forces captured the intact Ar 233 mockup as well as notes and drawings after the Liberation of France, but they did not continue development of the project and presumably scrapped the mockup.

Arado Ar 233 (Commercial Airliner)
Wingspan	77 ft 9.07 in / 23.70 m
Length	68 ft 5.65 in / 20.87 m
Height	21 ft 5.87 in / 6.55 m
Wing Area	807.29 ft² / 75.00 m²
Engine	2x 9-cylinder air-cooled Bramo 323 MA radial engine (986 hp / 735 kW)
Propeller	2x electrically started three-blade propeller
Propeller Diameter	11 ft 5.79 in / 3.50 m
Wheel Width	34.45 x 12.79 in / 875 x 325 mm – Nose Wheel 39.96 x 14.96 in / 1,015 x 380 mm – Fuselage Wheels
Maximum Weight	20,000 lb / 9,000 kg
Range	750 mi / 1,200 km
Radio Systems	1x FuG 101 1x FuBl II F 1x FuG X P
Crew	1x Pilot 1x Co-Pilot – Optional 1x Radio-Operator
Passenger Load	7x Passengers – With Co-Pilot 8x Passengers – Regular