Arado Ar 232

Arado Ar 232
Type:	Transport plane
Design country:	German Empire
Manufacturer:	Arado
First flight:	June 28, 1942
Commissioning:	1942
Production time:	1942 to 1944
Number of pieces:	20th

The Arado Ar 232 , also known as the “millipede” or “Tatzelwurm” , was a military transport aircraft developed and built in the German Reich during the Second World War by the Arado Flugzeugwerke in the Brandenburg an der Havel plant .

Development and testing

The design of the Ar 232 was based on an order placed by the Technical Office (GL / C) of the Reich Aviation Ministry (RLM) in late 1940 for several German companies, in which an "all-terrain transporter for use near the front" was required. The Arado draft was created in competition with the Fieseler project P 29 (later Fi 333 ) and other aircraft drafts that had not yet been determined with certainty. The Technical Office decided on the Ar 232. The Fieseler design did not get beyond the drawing board and dummy stage.

The design work for the later Ar 232, which initially ran under project number E 440, began in December 1940; the construction of parts began on March 30, 1941.

Walter Blume was in charge , while Wilhelm van Nes was responsible for overall design and aerodynamics. Hans Rebeski was involved as the owner of the patent applied to the high-lift wing, which had previously been tested on one of three Arado Ar 198 and one Arado Ar 240 built . From the start, Blume and van Nes tried to use every possibility of increasing lift at low airspeed. The boundary layer extraction system , which was examined in great detail at the Aerodynamic Research Institute (AVA) in Göttingen at the time, was included in the analysis and it was decided to equip one of the first two aircraft with it.

The second important requirement for success was the chassis. The term “unprepared terrain” was defined by the RLM in such a way that it also includes trenches 1.5 m wide and small elevations up to 0.8 m high. In order to meet this very extensive requirement, a caterpillar track with a distance between the axles of 4.2 to 5 m between the foremost and rearmost idler wheel was considered, with four pairs of pendulum suspended support wheels in between, over which a 32 cm wide endless rubber caterpillar belt should roll. However, this solution was quickly abandoned as too difficult and technically hardly manageable and was replaced by the final one with a double row of individually suspended and sprung low-pressure wheels.

According to a weekly report from the Rechlin test center for the period from March 27 to April 2, 1941, the responsible clerks were able to start "with the dummy processing of both projects" that week, meaning the P 29 from Fieseler and the E 440 from Arado. The first mention of the type designation Ar 232 dates back to June 1, 1941. At this time, a pilot series of six A-0 aircraft was planned, which would have been delivered between September and December 1942. At the same time, the procurement of materials for no fewer than 75 series A-1 aircraft was approved. The subsequent plans of October 15th canceled the development of the Ar 232 completely; work on the aircraft program nevertheless continued. In the following plans, the number of the pilot series A-0 should be increased to ten aircraft, plus 20 units with the designation B-0.

A transport aircraft like the Ar 232 had to stand back in the allocation of the planned BMW 801 engines , as the Focke-Wulf Fw 190 fighter aircraft had priority. In addition, other projects such as the Dornier Do 217 , Junkers Ju 88 , Junkers Ju 290 and Blohm & Voss BV 141 were dependent on this engine.

As an alternative solution, the Bramo 323 “Fafnir” engine was used , but four of these were required per aircraft. The necessary construction work, essentially only for a new, correspondingly longer, wing center section began, it seems, immediately. With the appearance of version B, consideration was given to building it with floats as well. However, this intention was soon dropped.

At this time, the further fate of the Ar 232 was in jeopardy: On August 7, 1942, a development meeting took place in the RLM under the direction of the General Air Force Master , Field Marshal Erhard Milch . The head of the Planning Office (GL / A), Major General Carl August von Gablenz, put forward his view that the Ar 232 should be sold as "the worst kind of aluminum eater". He also doubted their war-determining usefulness. With two Ju 52s you can "put something like this down". The general staff engineer Roluf Lucht was also negative. Only the head of the GL / C-E2 Office Group , Aircraft Development in the Technical Office (GL / C), master flight engineer Walter Friebel , was a convinced supporter of the aircraft , who pointed out that the aircraft was developed on a proposal by the Technical Office and for them Areas of application that cannot be served by the Ju 52. It is particularly suitable for winter use, because slightly wide runners can be placed underneath instead of the roller chassis. In addition, she would come out of every seat with the required 100 m take-off roll distance. General Field Marshal Milch was ultimately unable to cancel the development of the Ar 232. In conclusion, the minutes of the meeting stated that he “personally absolutely believed that he would paint the plane if he could”. A little later, on August 17 and 18, Milch stated that “because the Ar 232 requires large development capacities and consumes a lot of light metal, and compared to the Junkers Ju 352 it only offers the advantage of a shorter takeoff and landing , he asked to consider carefully whether this model could not be sold. Instead of one Ar 232, around four Ju 52s could be delivered. ”The project was not subsequently discontinued, but the planned production numbers fluctuated frequently.

Factory and E site testing

Ar 232 A

An Ar 232A-0, 1945

The first flight of a prototype, the Ar 232 V1, took place on June 28, 1942 at the Brandenburg-Neuendorf works airfield with master flight engineer Walter Kröger at the controls. Two more flights followed on June 30th and July 1st. This was followed by a break until August 11 to repair minor damage that the aircraft had sustained during its third flight while taxiing over a track system. On August 27th, Captain Heinz Braun from the Rechlin test site was the first non-factory pilot to fly the aircraft.

The second aircraft, the A-01, was already part of the pre-series production (pilot series) of ten machines. The A-01 had its maiden flight on November 20, 1942 and remained in flight operations until it crashed on February 6, 1943 while transferring from Rechlin to Stalingrad . The A-02 (first entry in the flight log February 1, 1943), the A-03 (first entry April 3 in Rechlin), the A-04 (April 12), and A-06 (April 5) followed at shorter intervals ), A-07 (April 7th), the A-05 (April 22nd), the A-08 (June 1st), the A-09 (July 8th) and the A-10, Wnr. 0100012, TC + EG (July 17th).

V2

Which aircraft was given the designation V2 is controversial. Only one of the aircraft that was completed between February 1 and July 17, 1943 is eligible. With the exception of the A-05, all of these went straight into action.

The first test flights made with the A-05 in Brandenburg were take-off and landing measurements, which took place on April 29, 1943. Shortly before, from April 13th to 17th, the same measurements had been made with the A-02. Representatives of the Rechlin test center were present at both test series, and they recorded the results in a partial report that is no longer available and communicated them to the RLM. The weekly report also contains the statement that on June 30th even the already mentioned head of the GL / C-E2 office group, Friebel himself, accompanied by the commander of the E-offices, Colonel Edgar Petersen , and other high-ranking representatives of the Rechlin testing station had come to Brandenburg to fly the plane.

In a broader context, the results and achievements achieved with the Ar 232 are contained in the report on a lecture that van Nes himself gave at AGARD in Brussels in August 1956, eleven years after the war . It was also the A-05 on which all the set-up kits developed for the model were tested and which therefore remained with the company until the end of the war. The first Luftwaffe pilots received their briefing on it.

More flights

The three aircraft A-06, A-07 and A-09 that were in Rechlin at the time were used for test flights up to z. B. used to Kirovograd , where freight was always transported. On July 23, 1943, an engine failed on the A-07 near Hildesheim , which led to the crash landing. At 70% damage, the aircraft was not rebuilt. The A-04 also broke 80% during a transport mission in Rechlin.

The usability of the Ar 232 for towing gliders was examined in Rechlin in October 1943 with the A-06 and the B-02 after the company had developed a corresponding kit that could be attached to the end of the tail boom. Both cargo gliders DFS 230 and Go 242 were towed. The result did not meet expectations. It turned out that the tow plane and trailer together could not carry more payload than the Arado alone and that much more slowly.

The B series

The four-engine Ar 232 B took off on its maiden flight on August 3, 1943. The second flight, carried out on the same day, ended with an emergency landing near Golow . An engine fire resulted in a total damage of 70 percent and the aircraft was then probably cannibalized.

The other nine B-0s followed at short intervals, with the February 1944 deadline for the delivery of the last aircraft likely being met. On June 12 and 13, 1944, a demonstration took place in Rechlin in front of high-ranking spectators. As early as June 14th, the plane crashed immediately after take-off in Lärz , killing six of the seven Arado employees on board.

Until the start of series production of the Ar 432 version, which was already planned at that time, according to the plan, further machines of this version as B-1 should be built in series after the ten pre-series B-0 aircraft. Both the flight logs and several documents clearly show that there were only ten Ar 232 B-0s plus one straggler.

The most ardent proponent of the aircraft, Walter Friebel , had an accident on November 20, 1943 with a Heinkel He 111 . With his death, the pressure behind the development of the Ar 232 and especially the Ar 432 eased significantly. Nevertheless, it is noteworthy that the aircraft - in contrast to the Ju 352, which was also largely made of steel tubing and wood - did not fall victim to the great deletion at Reichsmarschall Göring's conference on July 1, 1944. In any case, work was carried out until October 1944 with the proviso that as much wood as possible was used. To what extent this was implemented can no longer be determined.

Aircraft description

For the first time, the design had many features that are now considered the standard for military transport aircraft, such as the low-lying box-shaped fuselage with the lowerable loading ramp at the rear end and the high-lying stern, which allowed easy access to the loading area. In addition, the unusual undercarriage allowed it to be used on unprepared terrain. In addition, the aircraft should meet the requirement for the lowest possible take-off and landing speeds and thus short taxi routes.

Although the Luftwaffe still had a large number of Junkers Ju 52 / 3m in spite of the considerable losses that had already occurred , replacements had to be found for these outdated machines. Even if the advantages of the new design were recognizable, it was above all the high consumption of light metal that only resulted in the ordering of a small number of 22 aircraft. Work on the further development with the aim of largely replacing the light metal with "non-strategic" materials such as wood, however, continued until October 1944. Overall, the history of the Ar 232 is an example of the lack of an overall concept in the RLM.

General

Both versions of the Ar 232 represented a clear structure with a simple structure, consisting of large assemblies screwed together. It was a cantilevered shoulder wing, made entirely of metal, which was one of the first German aircraft to be equipped with a partially retractable nose-wheel landing gear. The large, spacious fuselage with an approximately square cross-section, rounded in a semicircle at the top, contained the driver's compartment with two seats at the front, of which the driver's seat on the left could also be armored as an armor set. For both seats there were complete controls with a steering column and pedals, of which the right-hand side could be connected and disconnected, but had no braking option.

Hold

Behind the cockpit was a cargo hold 6.6 m long, 2.3 m wide and 2.0 m high. For loading, a two-part, hydraulically operated loading flap was installed at the stern, which when closed was part of the outer wall. When opening, the upper part hinged at the rear folded upwards, while the lower part hinged at the front swiveled downwards and served as a ramp for introducing the load. The entire rear section could be unscrewed for bulky goods that did not fit through the loading hatch. The high mounted tubular tail boom with a double vertical tail also allowed vehicles to be approached directly. To handle and distribute the load correctly, there was a running track with a pulley block on the ceiling of the hold - offset a little from the center to the left - that could lift loads of up to 1500 kg. In the left front fuselage wall there was an entry door for the crew with a fold-out ladder, and eight round portholes on each side provided sufficient lighting for the interior.

Tail unit

The tail boom formed part of the fuselage contour at the front and was placed on the rear fuselage section, adjoining the rear spar of the wing center section, and screwed to both. At the rear end of the tail unit support tube with a circular cross-section, the horizontal tail unit was placed, which carried the two rudder units , which were basically rectangular at the top and bottom, as end disks . All rudders were single-spar with a torsionally rigid, sheet-metal-clad nose box and fabric-covered light metal frames behind. Both the rudder units and the two elevator halves could be interchanged. All oars were fully balanced and trimmable. It was operated via bumpers. At the rear end bulkhead of the support tube, a trestle could be attached to the existing eyes with three bolts as a kit, which had a releasable coupling at the end for towing cargo gliders or for attaching the brake parachute cables. When not in use, the whole thing could be covered by a hood that was pushed over and fastened with screws.

Structure

The structure consisted of a rectangular middle section 14.1 (A) or 15.5 (B) m long and 5 m deep. The trapezoidal outer wings with rounded end caps, identical for both versions, were attached to them. The entire structure was designed with two spars, with the outer wings each connected to the middle section with four expansion bolts. Between its two spars were the downwardly open cutouts for the main landing gear units pivoting inwards and, from the engines to the outside, a fuel tank with a capacity of 1350 liters. The lubricant reservoirs, each with a capacity of 110 l (in version A), were located directly behind the fire walls of the engines.

Over the entire span, the aircraft had landing wings consisting of two flaps on each side , which could be extended to the rear on two outriggers called slide rails in Fowler style and deflected downwards in the process. The ailerons extended with the outer landing wings, but retained their function. This was done using the Rebeski patent. The landing wing has increased the load-bearing area by around 25%. The extension and retraction was done electrically, but could also be done manually in an emergency using a crank behind the right seat. Thanks to these buoyancy aids, the fully loaded aircraft with a take-off weight of 16 t was able to take off within less than 200 m.

Braking parachute

The landing distance could be shortened by using a braking parachute which was attached in a box outside on the underside of the loading ramp. The shield line could be attached to the underside of the tail girder in clamps provided for this purpose, and then hooked into the releasable coupling at the stern.

landing gear

The most noticeable feature of the Ar 232 was the landing gear . A normal nose wheel chassis was available for use on airfields. The length of the spring struts of the two main landing gear halves, which could be retracted into the wings during flight, could be adjusted in order to lower the fuselage so far that the eleven (later reduced to ten) pairs of individually sprung small wheels with low-pressure tires under the fuselage came to the ground . To do this, the towed nose wheel, which was particularly large to absorb the bumps when rolling against smaller obstacles, was retracted halfway towards the rear. It was then level with the double row of small wheels behind it. As required by the tender, it was even possible to overcome trenches up to 1.5 m wide. The lowered position also made loading easier. The struts were also shortened when retracting. The many wheels also earned the aircraft its nickname mentioned at the beginning.

Crew and armament

The normal crew consisted of two to four men, of whom the pilot was the only one who had no additional task. The observer (radio operator, gunner or on-board attendant) also operated an MG 81 Z or an MG 131 in the tip of the fuselage (A stand), the on-board attendant (loadmaster, gunner) also operated a 2 cm MG 151 , which was also supported by an MG 81 Z could be replaced, in a hydraulic rotating mount HDL 151/2 covered with a plexiglass hood on the top of the fuselage behind the driver's cab (B-stand). One or two other MG 131 or MG 81 Z in armored lens mounts were also to be operated by the loadmaster or another rifleman at the end of the fuselage below the tail unit (C-stand). In addition, further defensive weapons could be used in window mounts in the side windows of the hold.

Conversion kits

There were a total of 23 kits for the aircraft, including the radio equipment, course control and armament. The list also includes folding seats that can be installed for transporting soldiers, devices for transporting the wounded on stretchers, an oil fire heater , even armored accommodation for a rubber dinghy and, last but not least, an emergency supply for hydraulics and on-board voltage known as a Gefinal unit . A snow skid split in length with a roller seat was included in the list of conversion kits with the letter “y”, but was not listed as attached to any aircraft. In the absence of own rated values, captured Russian designs were used to design the snow skid. However, there is no evidence that these runners were ever used. The only aircraft that was used in regions close to the polar was the A-10 on the Westa 5 . There it was only used for a short time in the summer and their trips to Spitsbergen and Bear Island were always carried out with a wheeled chassis, as all available pictures show. In the descriptions of the individual set-up kits in the machine manual, the letter “y” is also missing.

Technical specifications

Parameter	Data Ar 232 A-0	Data Ar 232 B-0
crew	2-4
length	23.5 m
span	32.0 m	33.5 m
height	6.6 m
Wing area
Wing extension
payload
Empty mass	11,135 kg	12,810 kg
Max. Takeoff mass	16,100 kg	17,600 kg
Max. Starting mass (overload)	18,600 kg	20,000 kg
Cruising speed
Top speed at the destination	283 km / h	295 km / h
Service ceiling	7600 m	8000 m
Range	1500 km	1400 km
Engines	2 × double radial engine BMW 801 , each 1600 PS (1180 kW) or 4 × Bramo 323 R, each 1000 PS (740 kW)
Armament	A stand (bow): MG 81 Z or MG 131 B-Stand (back): MG 81Z or MG 151/20 C-Stand (rear): MG 81Z or 1–2 MG 131

commitment

The first use of the Ar 232 took place on February 6, 1943; the German troops trapped near Stalingrad were to be supplied. The operation was unsuccessful and the machine was lost. Another machine was used in Northern Norway in the Weather Reconnaissance Squadron  5; she reached, among others, Spitzbergen and Bear Island . On August 26, 1943, she crashed into a slope near Oldereidet in Lakselv / Northern Norway, killing all of the inmates.

The 7th squadron of the supplementary transport squadron

Most of the completed machines were sent to the supplementary transport squadron (ETG.) In Schönwalde, which had a training function for transport pilots. Its newly established 7th squadron (7./ETG) should only be equipped with Ar 232. The first plane crashed there on August 15, 1943, killing the designated squadron captain, Oblt. Walter Meltzer , including the commander of the II./ETG, Major Kurt Wendorf . The further formation of the squadron took place in Eger under the command of the knight's cross bearer Major Josef Belz .

From December 17, 1943, the squadron received six machines and was relocated to Warsaw-Okęcie on February 2, 1944 , from where it carried out transports to the Eastern Front until February 9 . Presumably, the squadron's planes got their badge painted on at that time, an elephant with wings and wheels strapped on or under.

Back in Eger, there were four weeks of flight operations with transport tasks to destinations mainly in the Reich.

On March 19, the new order to relocate to Warsaw came , now with subordination to the 5th Transport Squadron . Transports to Odessa , Tiraspol , Jasionka , Galatz and other places in the south of the Eastern Front were flown, whereby the Ar 232 proved itself under all weather conditions and provided considerable transport services, such as the war diary (KTB) of the TG. 5 can be found. On March 29, a plane went missing on the flight from Odessa to Lviv .

Since the Wehrmacht was forced to withdraw further in the southeast, the flight routes from Warsaw were too long. Therefore, on April 13th, another transfer order was issued, this time to Ziliştea in Romania . Above all, Sevastopol was approached, with constant hunting and bombing attacks by the enemy. On the way there, day and night, it was mainly ammunition, food and supplies, while mainly the wounded had to be transported back.

After another hard use of all available transport aircraft, the evacuation of the Crimea was finished on May 12th, as was the 7./ETG. was relocated to Eger after the completion of individual orders. During the month of April, the focus of the action, the remaining four aircraft of the squadron with 405 tons had made about 13.1% of the total output of the TG 5; on the return flights even more than 14%. It should be noted that for this time, in addition to the two groups of the squadron equipped with Messerschmitt Me 323 , the Tr.Fl.St. 5 ( Ju 90 and P.108 ), Tr.Gr. 30 (He 111), towing group 2 (He 111 and Go 242) and the IV./TG. 1 (Ju 52) were subordinate to TG 5.

Company Zeppelin

In July 1944, two Russian agents with the task of assassinating Josef Stalin were to be dropped off with the A-08 as part of the " Operation Zeppelin " near Moscow . The A-08 had to turn back without having achieved anything. When they tried again, the agents were dropped off with the B-05, but shortly afterwards were caught by Soviet security forces. The B-05 was so badly damaged on landing that it could no longer take off on the return flight.

The race course

This term was coined by the crews of the six Ar 232, which belonged to the KG from mid-October 1944 . 200 and had been relocated to Großschiemanen in East Prussia under the command of Captain Behrendt . At night they flew supply flights for the - later only suspected - German combat group Scherhorn still present in the rear of the advancing Soviet troops . The last flights on the racetrack took place on February 15 and 16, 1945.

The last days of the war

The remaining four (possibly five) Ar 232 - all four-engined B except for one A - went back to Tutow , where they were finally taken over by the KG 200 and were given their squadron identification A3 + QB, RB and SB, with only RB clearly the B-07 and SB can be assigned to B-09. It is not clear whether the fourth still got TB. The takeover is probably related to the dissolution of 14./TG 4 , which was ordered for January 30, 1945 and had to be reported as completed by March 1. The last two-engine (Ofw. Emil Uhrig) and one of the four-engine were ordered to the berth of I./KG 200 in Hildesheim and at the beginning of April - like the Boeing B-17 and Consolidated B-24 standing there  - sent on to the Fürstenfeldbruck air base. Since it was not possible to land there after a bomb attack that had taken place shortly before, both of them evaded to Mühldorf am Inn . From there the four-engine with Ofw. Boldt was sent to Manching in order to recover the remaining cargo of a B-17 (Ofw. Johannsen) that had crashed nearby. Both planes received orders on April 23rd to supply an airfield enclosed near Agram by dropping them with supplies. They were then parked camouflaged in Mühldorf. The four-engined aircraft fell victim to a devastating low-flying attack on April 26th, along with many other aircraft, while Ofw. Uhrig set fire to the aircraft that had escaped when the Americans approached.

The two (or three) planes still standing in the north flew a few supply flights for the already enclosed capital Berlin , now obviously assigned to the large-capacity transport squadron under the command of Major Günther Mauss. On the night of April 25th, Ofw. Limbrecht was supposed to bring supplies for the 9th Army fighting in the south of Berlin to the Friedersdorf airfield together with several Ju 352s . Since there was no longer any sign of the Ju 352 that had flown ahead at the destination, he turned back without landing. On the way back, however, he had the misfortune of being detected by an English radar station north of Stendal, a Mosquito XIII (KP-P) launched from Rheine with a Canadian crew (W / C. Frank Hatton and F / L. Russ Rivers ) started on him. This took the Arado for a Ju 290, which should bring high-ranking people out of Berlin. The Ar 232 was hit, killing the on-board mechanic and severely damaging the aircraft. At that time, however, it was already too low for the crew to jump, so an emergency landing on a river bank was carried out. The rest of the crew then managed to leave the aircraft wreck before the cargo exploded. Four days later Ofw.Limbrecht was again at the wheel of another 232, the A3 + SB, with which he brought about 40 refugees, mostly women and children, from Tutow to Grossenbrode on two flights each time .

The second Ar 232 B was already there, apparently the A3 + QB, with which Sergeant Ernst Funk had come. It could only have been these two aircraft that the Frenchman Pierre Clostermann, flying with the Royal Air Force , attacked on May 3, 1945, as he writes in his book "The Great Arena". However, he claims "to have shot at a number of Ar 232, two of which would have gone up in flames". But only these two aircraft were there and one of them, the B-07, A3 + RB, could later be made afloat again by the on-board mechanics at the request of the occupying forces, which was not so easy at all. The winning winners demanded that the aircraft be rendered unfit to fly by removing the propellers and ailerons . The 1st guard of the B-09, Uffz. Willy Dorn, remembered that out of anger they had thrown the bearing bolts far away and then had to laboriously look for them again. Since Limbrecht had to leave because of a flight assignment with a Siebel Si 204 and did not return, it was now Funk who received the assignment to familiarize an English crew with the aircraft. This briefing was only carried out in Germany.

The new crew flew several times to Germany by plane to transport important booty to England . There the machine was flown by, among others, the test pilot of the Royal Aircraft Establishment , Captain Eric Brown, and found to be very good. The machine could be seen in 1945 with many other German aircraft at the big booty show in Farnborough , then remained parked until November 1947 and - although intended as a permanent exhibit - was scrapped.

literature

• Aviation archive Hafner: Arado Ar 232 A, technical compendium with 1,220 pages. Airplane manual, operating instructions, engine, weapon and radio equipment manuals. ISBN 978-3-939847-20-5 .
• Airplane manual Ar 232 A-0. Air force documents and flight logs, documents of the KTB Transportgeschwader 5 and special staff milk, records and statements from those involved.
• Van Nes: Report on the Cargo Aircraft Arado Ar 232.
• Article in Jet & Prop 1, 2 and 3/96.
• Fritz Morzik : The German transport aircraft in World War II. Frankfurt a. M. 1966.
• David Myhra: Arado Ar 232: The Luftwaffe's Combat Zone Transport Aircraft in World War II.
• Jörg Armin Kranzhoff: Arado aircraft. Volume 31 of the series Die deutsche Luftfahrt , Bernard & Graefe 2001, ISBN 3-7637-6122-5 .
• Herbert Ringlstetter: The Ar 232 . In: Flugzeug Classic . No. 9 , 2007, ISSN  1617-0725 .

Web links

Commons : Arado Ar 232  - collection of images, videos and audio files

Notes and individual references

1. ↑ C-official program for scheduling 19/2, June 1 1941st
2. ^ Delivery schedule 20, October 15, 1941.
3. ↑ Aircraft program for delivery schedule 21, March 15, 1942.
4. ^ Aircraft type sheet Ar 232 B, RLM, January 1, 1942, "Ar 232 A and B also as a float plane under investigation". A corresponding report by the DVL Institute for Sea Aviation shows that the investigation of the necessary float system on a model was already completed in December 1941 .
5. ↑ Rechlin weekly report, July 3, 1943.