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Blohm und Voss BV 155

The Blohm + Voss BV 155 was a high-altitude interceptor aircraft intended to be used by the Luftwaffe against raids by USAAF B-29's. Work started on the design in 1942, but the design went through a protracted development period for no obvious reason and was still under construction when World War II ended.


Remarks

When the performance estimates of the B-29 Superfortress first started reaching German ears in early 1942, widespread panic broke out. The plane had a maximum speed around 350 mph (563 km/h), and would attack in a cruise at about 225 mph (362 km/h) at 27,000 to 32,000 ft (8,000 to 10,000 m), an altitude that no German plane could operate at effectively. If there was any hope of countering attacks by this bomber, the Luftwaffe would need new fighters and destroyers as soon as possible.

A meeting was called in May at the Messerschmitt factory in Augsburg, and several plans for such Special High Altitude Fighters were hammered out. The fighter solution would be provided by modified high-altitude versions of the Focke-Wulf Fw 190 powered by various versions of the Junkers Jumo 213 engine, allocating three new numbers to Focke-Wulf, 152, 153 and 154. Messerschmitt offered a version of their Bf 109ST powered by the Daimler-Benz DB 628, which was given the name Me 155.

The Bf 109ST was a development of navalized 109T, including more wing and inwardly-retracting wide-set landing gear. With these changes it was hoped that the basic 109, difficult enough to land successfully on a runway, would be able to cope with landing on the Graf Zeppelin aircraft carrier. The longer wing made it a natural to be adapted into high-altitude use, the basic version with naval equipment became the Me 155A, and the additional changes for high-altitude use would be limited to providing a pressurized cockpit and the new DB 628 engine, becoming the Me 155B.

Me 155B
Work on the Me 155B started off well. For the high-altitude requirement, Messerschmitt planned on giving the 155 the Daimler-Benz DB 628 engine, a modification of the current 605 with a new two-stage supercharger and intercooler. A converted Bf 109G with this engine had already flown by the end of May 1942 and reached 50,850 feet, although the heavier 155 would be capable of "only" 46,00 feet.

However the Technische Amt decided that a more promising engine should be used, the 603U with a turbocharger. This engine was longer and would also require extra space in the fuselage to mount the turbocharger and its plumbing, so the 155 required considerably more modification. The turbocharger was mounted behind the cockpit, fed air from a new scoop under the fuselage. Compressed air was then fed forward to the engine in two tubes running on the outside of the plane. The wingspan was elongated by taking the standard wings from the 109G and adding a new "plug" in the middle.

In the summer the 155 project was transferred to Paris, in order to relieve the overworked Augsburg design teams. Due to various problems work progressed very slowly throughout the remainder of 1942. By early 1943 Focke-Wulf had made significant progress on their designs, while the 155 was no further along. Back at Augsburg the designers started to get the feeling it would never be completed, and started work on an even higher performance version, Projeckt 1091, which extended the wings of the 155 by inserting a "plug" in the middle. Other teams also started working on a high-altitude version of the Me 209, and soon there was fighting over which version to put forward as the "real" Me 155B. By the middle of 1943 the T-Amt had finally had enough, and transferred the new P.1091 to Blohm + Voss, who were otherwise underworked.

BV 155A
Blohm und Voss found, somewhat to their surprise, that P.1091 was essentially a research project only, and little actual engineering had been started. After examining the work they decided that practically everything about the design needed to be changed. Fighting between the Messerschmitt designers and the B&V factory engineers soon broke out, and progress slowed further.

In September 1943 an order for five prototypes was placed. Blohm und Voss decided that the design problems still needed fixing, but by late 1943 they still hadn't been addressed. A meeting was called to finally address these problems, but the Messerschmitt people didn't bother to show up. As late as November 1943 changes were still being made, and Blohm und Voss decided to remove the complex underwing radiators favoured by Messerschmitt for two large scoop-type units mounted above the wings. B&V built a mock-up and had it tested in the LFA wind tunnel, but Messerschmitt refused to help. Late in 1943 Blohm & Voss formally advised the RLM of their problems with Messerschmitt and implored them to intervene. By this point the T-Amt was just as fed up, and removed Messerschmitt from the project entirely.

The design, now named the BV 155A, was finally completely in the hands of one design team. B&V modified the design with a completely new laminar flow wing in place of the original "extended" one from the Me 155. They also changed details of many other parts of the plane, including new landing gear (from the Ju 87) and a new tail unit. Further wind tunnel testing showed that there was a serious problem with the overwing radiators, at high angles of attack the wing "blanked" them from the airflow and cooling would suffer. The decision was made to abandon the A model completely and move on.

BV 155B
The obvious solution to the problem with the radiator was to move them to the lower part of the wing. This change also moved the center of gravity to the rear, so the B models moved the cockpit forward to compensate. Now that they were modifying the cockpit area, they also decided to change the canopy to a bubble type and cut down the rear decking of the plane. With the decking missing the plane now had too little directional stability, and a larger vertical stabilizer needed to be added. The result was the BV 155B.

By September 1944 the first prototype, V-1, originally to be 155A was well along to completion. It was decided to modify it with the underwing radiators but leave it otherwise unchanged. This would delay its completion until December, but a full B model, the V-2, would quickly follow it in January. V-1 was finally complete just before Christmas, and after vibration tests the first flight was set for mid-January. However a number of additional delays meant that it wasn't turned over to the factory test pilots until February, flying for the first time on the 8th.

Leaking coolant required a ending the first flight early, but the problem was quickly repaired and the V-1 took to the air a second time on the 10th. This flight went well, but the test pilot noted that ground handling was very difficult due to the very wide-set gear. This is perhaps ironic, considering that the original 109 was famous for the same problems due to its narrow-set gear.

Projekt 205
Click to enlargeBy mid 1944 it was proposed to have all 5 Bv155 prototypes completed by mid 1945. Meanwhile Blohm & Voss had been working on the Bv P205, this had a different layout to the Bv 155B originally intended to have the 4,000 hp 24-cylinder, water-cooled, Argus As 413. Due to the expected un-availability of this engine the Bv P205 in its final form it was to be powered by the DB 603U. In P.205, the underwing radiators were replaced by an annular one around the front of the engine, a design feature commonly found on a number of German designs. With the wings now free of clutter, they were considerably simpler and were reduced in span. This also had the side effect of reducing the track, which would later prove to be adequate change. The new design would be simpler, lighter and faster, and plans were made to make it the standard version of the aircraft. During the October reevaluation, it was agreed that V-1 through V-3 would be completed as B models, while a new series of five would be completed to the new standard as the BV 155C.

BV 155C
Click to enlargeWhile work continued on the B models, design work on the C model continued. The design eventually settled on a single large tunnel under the nose of the aircraft, containing both the radiators and the turbocharger air scoop. This gave the plane a somewhat triangular front section, but was otherwise similar to the P.205.

 

On May 3rd, 1945, the city of Hamburg surrendered to the British, who ordered everyone out of the Blohm und Voss plant. V-1 was in a flyable state at this point, and the British brought in a pilot to fly it to England for testing. However he had problems during the flight and crash-landed it. All the parts for the still-incomplete V-2 and V-3 were shipped to Farnborough, and V-2 was put on public display in October. There was some discussion of completing the aircraft using parts of V-3, but there was no money for this and it was later handed over to the US. Today V-3 is in storage at Silver Hill, part of the National Air and Space Museum. There is some confusion over which plane is in the US, V-2 or V-3, and the location of the other (whichever it is) is unknown.


 

Blohm & Voss Bv 155A

Blohm & Voss Bv 155B

Blohm & Voss Bv P205

Blohm & Voss Bv 155C

 

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Specification & Performance

Description
Role Day fighter
Crew one, pilot

Dimensions
Length 11.9 m 39ft 4in
Wingspan 20.3 m 67ft
Height
Wing area 39 m 384 ft

Weights
Empty 4,868 kg 10,734 lb
Maximum take-off 5,500 kg 12,100 lb

Powerplant
Engines 1 turbocharged DB 603
Power 1.2 MW 1,610 hp

Performance
Maximum speed 690 km/h 429 mph
Combat range
Ferry range
Service ceiling 16,950 m 55,610 ft

Armament
Guns 1x 30 mm MK 108 cannon
2x 20mm MG 151/20 cannon
Bombs none


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