The Blohm & Voss BV 138, 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, ‘The flying clog’.
Three piston engines were used.
The central engine was mounted above the wing, driving a four blade propeller, while the wing engines were lower, with three blade propellers.
The pre-production prototypes and the BV 138 A-01 to BV 138 A-06, were powered by various makes of engines ranging from 485–746 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 prop shaft placement, emerging forward at the uppermost front end of the powerplant.
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 “beak” at the stern.
Two enclosed, powered gun turrets, each mounting a single MG 151/20 autocannon, were located prominently at the bow and stern.
A third, fully open Scarff ring-like emplacement, behind the central engine and both above and forward of the rear turret, mounted a 13 mm MG 131 heavy machine gun which covered fields of fire obstructed from the other turrets by the horizontal stabilizer.