Blohm und Voss BV 138
A three-engined German maritime patrol flying boat of the Second World War, designed by Richard Vogt for Hamburger Flugzeugbau, the aircraft subsidiary of the Blohm und Voss shipbuilding firm. Nicknamed the "Flying Clog" for its short, flat-sided hull, it first flew in 1937 as the Ha 138, was completely redesigned after its prototypes proved unstable, and entered Luftwaffe service in 1940. The definitive C-1 flew long-range reconnaissance from French and Norwegian bases in support of the U-boat campaign, and others swept mines or carried troops. No complete example survives; a wreck raised from the Øresund is displayed at the Danish Technical Museum in Helsingør.
Why It Mattered
The BV 138 was the first flying boat produced by Blohm und Voss, and it became the most numerous aircraft the Hamburg firm built. Wikipedia calls it the Luftwaffe's primary seaborne patrol and naval reconnaissance aircraft of the Second World War. Its crews flew from the coasts of France and Norway in support of the U-boat campaign. The type also proved adaptable, taking on radar-equipped anti-shipping patrols, austere troop transport and minesweeping alongside its reconnaissance work. Its diesel engines even allowed it to refuel at sea from U-boats, which used diesel engines themselves.
Design Notes
The BV 138 was designed by Richard Vogt at Hamburger Flugzeugbau, the aircraft subsidiary founded by the Blohm und Voss shipbuilding firm on 4 July 1933. The prototypes were designated Ha 138 after the subsidiary; when the firm's designations changed to Bv in 1937, production aircraft became the Bv 138. Vogt's original design had twin engines, but problems with the intended 1,000 hp engines forced a redesign around three 650 hp Junkers Jumo 205C diesels, the third above the centre of the wing; the hull was short, with twin tail booms. Its compact hull, with hydrodynamic step and flat sides, earned the aircraft the nickname Fliegender Holzschuh, the flying clog. The first two prototypes proved unstable in the air and on the water; a complete redesign began in 1938, with a longer hull, larger tail surfaces and stronger booms. On the C-1 the centre engine drove a four-bladed propeller, the outer engines three-bladed ones with broader blades, curing a vibration problem of the older aircraft. The C-1 carried two 20 mm cannon and a 13 mm MG 131 machine gun behind the central engine. The crew numbered six, and up to ten passengers could be carried.
Operational History
Ha 138V1, the first prototype, flew for the first time on 15 July 1937; the V2 was completed in August, and tests began that November. The unstable prototypes forced the 1938 redesign, and the first production A-1 did not fly until April 1940. Two of the first production aircraft took part in the invasion of Norway; real service entry, though, waited until October-November 1940. It was then flown by the Luftwaffe's long-range reconnaissance units, operating mainly from the French and Norwegian coasts in support of the U-boat campaign. Neither the A-1 nor the strengthened B-1, of which nineteen were built, was a great success in service; the still stronger C-1 finally solved the structural problem. The C-1 entered service in March 1941 and, on History of War's accounting, made up 227 of a total production run of 279 aircraft. Some aircraft carried FuG 200 Hohentwiel radar sets, which enabled the type to be used on anti-shipping missions. In 1943, the U-boat U-255 refuelled a BV 138 four times for reconnaissance flights over the Kara Sea; no shipping was found that would justify a cruiser mission, and the operation was cancelled. Some BV 138s flew with the special-operations unit KG 200, carrying up to ten fully armed infantry troops in place of a bomb load. Other aircraft, converted from B-0s, became BV 138MS minesweepers, with all guns removed and a circular dural hoop installed around the fuselage, used to detonate magnetic mines.
Afterlife
No complete BV 138 remains in existence. A wreck raised from the seabed of the Øresund in 2000 is on display at the Danish Technical Museum in Helsingør. Wikipedia reports that this aircraft had sunk after the war during a British air show, but flags that detail as needing a citation. In 2012 two divers found another wreck in Romania's Lake Siutghiol; Romanian Navy divers recovered it, and it is now kept by the National Museum of the Romanian Navy at Constanța. Other wrecks remain on the seabed: one was filmed in 2013 at a depth of 35 metres in Norway's Porsangerfjorden, and another was identified near Svalbard in 2022.