POWER PLANT: One Hirth HM 502 six-cylinder inverted inline engine, rated at 160 hp
PERFORMANCE: 106 mph
COMMENT: Designed from the outset for use on U-boat “cruisers”, like the Type XI B, the Ar 231 was a light parasol-wing aircraft. The aircraft was powered by an inline engine, weighed around 2,200 lb, and had a 33ft wingspan. The design led to a simple and compact aircraft that could be fitted into a storage cylinder only 6.7 ft in diameter. For ease of storage, the Ar 231’s wings featured detachable sections that two operators could remove in less than six minutes. One unusual feature was an offset wing design, with the right wing root attaching to the wing’s tilted center section (elevated above the fuselage, as on all parasol-wing designs) and lower than the left wing root, to allow the wings to be quickly folded up. Testing soon revealed the Ar 231s to be fragile, underpowered, and difficult to fly even during calm weather, and as a result, development ended in favour of the Focke-Achgelis Fa 330 gyro glider. Some of the testing was done on the auxiliary cruiser “Stier”. Only six prototypes were built (Ref.: 24).
TYPE: Long-range Transport, Maritime Patrol and Bomber Flying Boat
ACCOMMODATION: Crew of 12
POWER PLANT: Six Daimler-Benz DB 603G, rated at 1,900 hp
PERFORMANCE: 264 mph at 19,685 ft
COMMENTS: First prototype flew in April 1944, but was sunk early 1945 by strafing Mustangs. At the end of WWII the second prototype was virtually complete and construction of the third was in an advanced stage
POWER PLANT: One BMW VI 7,3 Z liquid-cooled engine, rated at 750 hp
PERFORMANCE: 205 mph
COMMENT: The Heinkel He 51 was a single-seat biplane which was produced in a number of different versions. It was initially developed as a fighter, it was also developed as a ground-attack aircraft and a floatplane.
In 1931, Heinkel Aircraft Company developed the Heinkel He 49, officially an advanced trainer in fact it was a fighter. The first prototype flew in November 1932, and was followed by two further prototypes with a longer fuselage, and a revised engine. The type was ordered into production for the still secret Luftwaffe as Heinkel He 51, the first pre-production aircraft flying in May 1933. Deliveries started in July of the next year.
The He 51 was a conventional single-bay biplane, with all-metal construction and fabric covering. It was powered by a BMW VI engine, with an armament of two machine guns mounted above the engine. The He 51 was intended to replace the earlier Arado Ar 65, but served side-by-side with the slightly later Arado Ar 68. The He 51 was outdated the day it entered service, and after an initial run of 150 production fighters, the design was switched into the modified He 51B, with approximately 450 built, including about 46 He 51B-2 floatplanes. With begin of WW II the Heinkel He 51B-2 was only used in a role as trainer (Ref.: 24).
POWER PLANT: Two Junkers Jumo 205C-4 liquid-cooled diesel engines, rated at 605 hp each
PERFORMANCE: 155 mph at sea level
COMMENT: In 1934, the Dornier Flugzeugwerke started development of a new twin-engined flying boat to replace the Dornier Do J “Wal“ (Whale) in both military (Do 16) and civil (Do JI and Do J II) roles. The resultant design, Do 18 retained the layout of the “Wal”, with a metal hull fitted with distinctive stabilizing sponsons, and powered by two engines above the wing in a push-pull layout, but was aerodynamically and hydrodynamically more efficient. It was planned to be powered by two of the new Junkers Jumo 205 diesel engines. Although heavy, these promised to give much lower fuel consumption than conventional petrol engines of similar power.
The Do 18G, 62 units built, was an improved version, powered by two 880 hp Jumo 205D engines, armed with a 13 mm MG machine gun in the bow, and a 20 mm MG 151 cannon in a power-operated dorsal turret.
In German Luftwaffe service, the Dornier Do 18G was obsolete by the outbreak of World War II, but – as the only military flying boat – 62 (58 serviceable) aircraft in five squadrons were in use mainly on North Sea reconnaissance missions. In 1940 some squadrons changed their base to Norway. The vulnerable and underpowered flying boat was soon relegated to training and the air/sea rescue role. In the middle of 1941, only one squadron was still operational on Do 18. The Blohm & Voss Bv 138 had superseded the Dornier Do 18G.
A Dornier Do 18G was the first German aircraft to be shot down by British aircraft during the war, when one of a formation of three was caught over the North Sea by nine Fleet Air Arm Blackburn “Skua” fighter bombers of 803 Naval Air Squadron flying from HMS “Ark Royal” on 26 September 1939 (Ref.: 24).
TYPE: Reconnaissance, transport and training flying boat
ACCOMMODATION: Crew of two to four plus 8-10 passengers or equivalent freight
POWER PLANT: Two BMW VI liquid-cooled engines, rated at 700 hp each
PERFORMANCE: 143 mph
COMMENT: The Dornier Do J “Wal” (“Whale”) was a twin-engine German flying boat of the 1920s designed by Dornier Flugzeugwerke. The Do J had a high-mounted strut-braced monoplane wing with two piston engines mounted in tandem in a central nacelle above the wing; one engine drove a tractor and the other drove a pusher propeller. The hull made use of Claudius Dornier’s patented sponsons on the hull’s sides.
The Do J made its maiden flight on November, 1922. The flight, as well as most production until 1932, took place in Italy because of the restrictions on aviation in Germany after World War I under the terms of Treaty of Versailles. Dornier began to produce the “Wal” in Germany in 1931; production went on until 1936. The Dornier J I and its variant J II “Wal” were some of the most famous flying boats of the periods between the world wars.
A military version was the Dornier Do J II d and was in service with the German Luftwaffe as Dornier Do 16 “Militärwal” (“Military Whale”) according to the aircraft designation system of 1934 by the ReichsLuftsfahrtMinisterium (Reich Air Ministry, RLM). It was used as a reconnaissance and transport aircraft. A crew of two to four rode in an open cockpit close to the nose of the hull. There was one machine gun position in the bow in front of the cockpit and one or two amidships. Some 30 Dornier Do 16 “Militärwal” being delivered for the Luftwaffe in 1935. Eventually these were replaced by the Dornier Do 18 and the “Militärwal” was relegated to training roles.
Note: In many publications the Dornier J II d “Military Whale” is cited as Dornier Do 15. So done on my website, too, (but now corrected). The proper designation is Dornier Do 16 (Ref. 24).
POWER PLANT: One BMW 132K radial engine, rated at 960 hp
PERFORMANCE: 208 mph
COMMENT: The Heinkel He 114 was a sesquiwing reconnaissance seaplane produced for the German Kriegsmarine (German Navy) in the 1930s for use from warships. It replaced the company’s Heinkel He 60, but did not remain in service long before being replaced in turn by the Arado Ar 196 as standard spotter aircraft.
While the fuselage and flotation gear of the He 114 were completely conventional, its wing arrangement was highly unusual. The upper set of wings was attached to the fuselage with a set of cabane struts, as in a parasol wing monoplane, whereas the lower set was of much lesser span while having approximately the same chord. This general layout is not especially unusual, and is known as a “Sesquiplane”, or a biplane which has a smaller lower wing. Typically, the lower wing is about 3/4 of the span of the upper wing, and has a smaller chord as well. The He 114 has a much shorter lower wing than usual, but has the same chord as the upper wing, which keeps the wing area ratio similar.
The He 114 was never a great success, was not built in large numbers, and served with the Luftwaffe for only a short time. While the Heinkel He 60 had handled very well on the water but been sluggish in the air, the He 114’s handling while afloat was poor and its performance in the air scarcely better than the aircraft it replaced (Ref.: 24).