The Blohm & Voss BV 138 Seedrache (Sea Dragon), but nicknamed Der Fliegende Holzschuh ("flying clog", from the side-view shape of its fuselage, as well as a play on the title of the Wagner opera 'Der fliegende Holländer' or 'The Flying Dutchman') was a World War II German trimotor flying boat that served as the Luftwaffe's main seaborne long-range maritime patrol and naval reconnaissance aircraft. A total of 297 BV 138s were built between 1938 and 1943. Originally developed under the company name of Hamburger Flugzeugbau, the type was initially designated the Ha 138. Its appearance was unique in its combination of unusual design features with its twin boom tail unit, short fuselage and trimotor engine configuration. The short hull, with its hydrodynamic step beneath and flat sides, earned it the nickname, "Fliegender Holzschuh" (the flying clog). The booms of the twin tail unit, much like the smaller Focke-Wulf Fw 189 twin-engined reconnaissance monoplane, extended horizontally from the rear of the outer engine nacelles. For hydrodynamic reasons, the hull featured a distinct "turn-down", or "beak" at the stern. The first prototype featured a gull wing, but during the first flight it was discovered that this wing could not generate enough lift, so the concept was abandoned on the second prototype. The airplanes had also a hardpoint for catapult launches from seaplane tenders. Three piston engines were used. The central engine was mounted above the wing, while the wing engines were lower. The pre-production prototypes and the BV 138 A-01 to BV 138 A-06, were powered by various makes of engines ranging from 485 to 746 kW (650–1,000 hp). The first standardized version, BV 138 B-1, was powered by three 880 PS (868 hp, 647 kW) Junkers Jumo 205D two-stroke, opposed-piston aircraft diesel engines. The engine cowlings also had an atypical appearance, due to the unique nature of the vertical orientation of the six-cylinder opposed-piston Jumo 205 diesel engines, and resembled the cowlings of 4 or 6-cylinder inverted inline engines found on smaller civil and utility aircraft from the Jumo 205's propshaft placement, emerging forward at the uppermost front end of the powerplant. The choice for diesel engines made it possible to refuel at sea from U-boats, who also use diesel engines. When refuelling at sea, the airplane had to be fitted with a fuel filter as diesel fuel from ships contains some condensation. Originally developed under the company name of Hamburger Flugzeugbau, the type was initially designated the Ha 138. Its appearance was unique in its combination of unusual design features with its twin boom tail unit, short fuselage and trimotor engine configuration. The short hull, with its hydrodynamic step beneath and flat sides, earned it the nickname, "Fliegender Holzschuh" (the flying clog). The booms of the twin tail unit, much like the smaller Focke-Wulf Fw 189 twin-engined reconnaissance monoplane, extended horizontally from the rear of the outer engine nacelles. For hydrodynamic reasons, the hull featured a distinct "turn-down", or "beak" at the stern. The first prototype featured a gull wing, but during the first flight it was discovered that this wing could not generate enough lift, so the concept was abandoned on the second prototype. The airplanes had also a hardpoint for catapult launches from seaplane tenders. BV 138 being prepared for catapult launch on the aircraft tender Friesenland. Three piston engines were used. The central engine was mounted above the wing, while the wing engines were lower. The pre-production prototypes and the BV 138 A-01 to BV 138 A-06, were powered by various makes of engines ranging from 485 to 746 kW (650–1,000 hp). The first standardized version, BV 138 B-1, was powered by three 880 PS (868 hp, 647 kW) Junkers Jumo 205D two-stroke, opposed-piston aircraft diesel engines. The engine cowlings also had an atypical appearance, due to the unique nature of the vertical orientation of the six-cylinder opposed-piston Jumo 205 diesel engines, and resembled the cowlings of 4 or 6-cylinder inverted inline engines found on smaller civil and utility aircraft from the Jumo 205's propshaft placement, emerging forward at the uppermost front end of the powerplant. The choice for diesel engines made it possible to refuel at sea from U-boats, who also use diesel engines. When refuelling at sea, the airplane had to be fitted with a fuel filter as diesel fuel from ships contains some condensation. There were three gun positions on the aircraft: there was one on the bow with an enclosed, powered gun turret with a single MG 151/20 autocannon. On the stern the fields of fire were obstructed by the tail with the horizontal stabilizer, so there was one gun position lower on the fuselage and a second one higher just behind the central top engine. The gun position behind the central engine, which could see over the horizontal stabilizer, was a fully open Scarff ring-like emplacement which could mount a 7.92 mm MG 15 machine gun, but most aircraft mounted a 13 mm MG 131 heavy machine gun. The lower gun position at the rear fuselage sighted below the horizontal stabilizer. It too was left open and equipped with a machine gun on early aircraft, however later most aircraft mounted an enclosed powered turret similar to the one on the bow. For operational history and variants, click here.
