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). 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.

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

A Bv 138 flying boat shot down by a Bristol Beaufighter of No. 404 Squadron RCAF near the northern coast of Scotland, 1943.

During the invasion of Norway in April 1940, some of the pre-production aircraft were pressed into service as troop transports.

The main variant, BV 138 C-1, began service in March 1941.

Ha 138 V1 (D-ARAK)

First prototype, developed under Hamburger Flugzeugbau designation. First flight on 15 July 1937.

Ha 138 V2 (D-AMOR)

Second prototype, developed under Hamburger Flugzeugbau designation. First flight in August 1937.

Ha 138 V3

Third prototype, developed under Hamburger Flugzeugbau designation. Construction abandoned due to redesign.

BV 138 A-01 to 06

Pre-production operational test beds ; six built.

BV 138 A-1

First serial production, 25 built. Standard engine is the 605 PS Junkers Jumo 205 C.

BV 138 B-0

Pre-production operational test beds, in service by October 1940 ; 10 built.

BV 138 B-1

Entered service in November 1940 ; 21 built. Engines are upgraded to 880 PS (868 hp, 647 kW) Junkers Jumo 205D two-stroke, opposed-piston aircraft diesel engines.

BV 138 C-1

From this version on, the central motor was fitted with a four-blade propeller, while the wing engines kept a three-blade propeller, but the blades were reinforced and wider ; 227 built.

BV 138 MS

Minensuch (mine-search) minesweeping version ; all MS variants were converted from existing aircraft and had their armament removed ; the turrets and gun positions were covered.

Many German aircraft had Umbau sets available for modifications in the field. For the BV 138 there was an Umbau set for adding a bomb rack under the port wing. With such an Umbau the bomb payload could be doubled.[5] As per German nomenclature, such aircraft held a suffix '/U'. A BV 138 C-1 aircraft with the Umbau modification would become BV 138 C-1/U1.

The wreck of NJ+HE 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 WWII German seaplane harbour in Indre Billefjord.[6]

Another wreckage of a BV 138 was identified by the Norwegian Mapping and Cadastre Authority on the seabed near Svalbard in 2022.[7]

Data from Aircraft of the Third Reich : Volume One [8]

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, 647 kW (868 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 (31,000 lb) at sea level
• Cruise speed: 235 km/h (146 mph, 127 kn) at 1,000 m (3,300 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 (32,000 lb)

2,800 m (9,200 ft) at 17,650 kg (38,910 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 3 × 50 kg (110.2 lb) bombs or 2 × 150 kg (330.7 lb) depth charges under starboard wing root, and with the Umbau set, the same payload could be attached to the port wing as well.

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