Blohm & Voss BV 138

The second prototype Ha 138/BV 138 V2

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).

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 propshaft 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 "turn-down", or "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.

In all, 227 examples of standard service variants of the BV 138 were built. The first such variant, BV 138 C-1, began service in March 1941. While non-standard variants carried a variety of armament, the standard variant featured two 20 mm MG 151/20 cannon, one in a power-operated bow turret and one in a power-operated stern turret, up to three 7.92 mm MG 15 machine guns, and a 13 mm (.51 in) MG 131 machine gun in the aft center engine nacelle. It could carry up to 500 kg (1,100 lb) of bombs or depth charges (under the starboard wing root only) or, in place of these, up to 10 passengers.

Both the B-1/U1 and C-1/U1 variants had racks under both wings to double the offensive load.[2]

Some examples of the BV 138 were adapted to specialized roles. The Bv 138 was tested with the Walter HWK 109-500 Starthilfe RATO jettisonable rocket pod, used in pairs, for shorter takeoff performance.[3] One anti-shipping variant carried FuG 200 Hohentwiel low-UHF band maritime search radar. The BV 138 MS variant was converted for minesweeping,[4] and carried magnetic field-generating degaussing equipment, including a hoop antenna with a diameter equal to the length of the fuselage, which encircled the hull and wings, which was also used on certain models of the Ju 52/3m trimotor transport used for the same duty.

Blohm & Voss BV 138 at anchor on Lake Siutghiol, near Constanta, Romania in 1943.

Prototypes

• developed under Hamburger Flugzeugbau designation
• Ha 138 V1 (D-ARAK) – First flight on 15 July 1937
• Ha 138 V2 (D-AMOR) – First flight in August 1937
• Ha 138 V3 – Construction abandoned due to redesign.

Production

• BV 138 A-01 to 06 – Operational testbeds
• BV 138 A-1 – Flew reconnaissance during invasion of Norway
• BV 138 B-0 – Officially entered service in October 1940
• BV 138 B-1 – Entered service in November 1940
  • BV 138 B-1/U1
• BV 138 C-1, also had minesweeper variant
  • BV 138 C-1/U
• BV 138 MS – Minensuch (mine-search) minesweeping version.

The wreck of a Blohm & Voss BV 138 at display at the National Museum of Science and Technology (Danmarks Tekniske Museum) in Elsinore, Denmark. The wing spar is poised over the aircraft in the same position as it was, when the wreck was discovered in The Sound, off Copenhagen.

No complete BV 138s remain in existence. However, the wreck of one aircraft, sunk after the war in a British air show, was raised from the seabed of the Øresund Sound in 2000, and is on display at the Danish Technical Museum in Helsingør.

In June 2013, a vessel from the Norwegian Geological Survey filmed a Blohm & Voss BV 138 at a depth of 35 m in Porsangerfjorden, Norway, not far from the WW2 German seaplane harbour in Indre Billefjord.[5]

Data from Aircraft of the Third Reich : Volume One[6]

General characteristics

• Crew: 6 (pilot, navigator, radio operator, nose-gunner, rear-gunner, upper-rear gunner)
• Capacity: up to 10 passengers
• Length: 19.85 m (65 ft 1 in)
• Wingspan: 26.94 m (88 ft 5 in)
• Height: 5.9 m (19 ft 4 in)
• Wing area: 112 m² (1,210 sq ft)
• Empty weight: 11,770 kg (25,948 lb)
• Gross weight: 14,500 kg (31,967 lb)
• Max takeoff weight: 17,650 kg (38,912 lb)
• Fuel capacity: 3,750 l (990 US gal; 820 imp gal) maximum internal fuel
• Powerplant: 3 × Junkers Jumo 205D 6-cylinder liqiuid-cooled opposed piston diesel engines, 656 kW (880 hp) each for take-off
• Propellers: 3-bladed constant-speed propellers

Performance

• Maximum speed: 285 km/h (177 mph, 154 kn) at sea level at 14,000 kg (30,865 lb) at sea level
• Cruise speed: 235 km/h (146 mph, 127 kn) at 1,000 m (3,281 ft)
• Range: 1,220 km (760 mi, 660 nmi) at 195 km/h (121 mph; 105 kn)
• Ferry range: 4,300 km (2,700 mi, 2,300 nmi) with max fuel
• Endurance: 6 hours 30 minutes normal; 18 hours maximum
• Service ceiling: 5,000 m (16,000 ft) at 14,500 kg (31,967 lb)

2,800 m (9,186 ft) at 17,650 kg (38,912 lb)

• Rate of climb: 3.67 m/s (722 ft/min)
• Time to altitude: 3,170 m (10,400 ft) in 24 minutes
• Wing loading: 114.2 kg/m² (23.4 lb/sq ft)
• Power/mass: 0.106 kW/kg (0.064 hp/lb)

Armament

• Guns:
  

• 2 × 20 mm (0.787 in) MG 151 cannon, one in a nose turret and one in the rear fuselage covering upper rear area
• 1 × 13 mm (0.512 in) MG 131 machine gun in open position behind the central engine, covering the top rear area
• 1–3 × 7.92 mm (0.312 in) MG 15 machine guns (optional)

• Bombs: :* up to 6 × 50 kg (110.2 lb) bombs or 4 × 150 kg (330.7 lb) depth charges under starboard wing root only (optional)

Aircraft of comparable role, configuration, and era

• CANT Z.506
• Consolidated PBY Catalina
• Dornier Do 18
• Kawanishi H6K
• Short Sunderland

Related lists

• List of aircraft of World War II
• List of military aircraft of Germany

Wikimedia Commons has media related to Blohm & Voss BV 138.

• Article on a BV 138 which sank near Trondheim in Norway
• Website dedicated to the BV 138
• Specs
• German plane wrecks in Norway, WWII