Blohm & Voss Ha 137

Infobox Aircraft
name = Ha 137
type = Dive bomber
manufacturer = Blohm & Voss


caption =
designer =
first flight = April 1935
introduced =
retired =
status =
primary user =
more users =
produced = 1935-1937
number built = 6
unit cost =
variants with their own articles = The Ha 137 was a German ground-attack aircraft of the 1930s. It was Blohm & Voss's entry into the contest to equip the re-forming Luftwaffe with their first purpose-built dive bomber. Although the contest would eventually be won by the Junkers Ju 87, the Ha 137 demonstrated that B&V's Hamburger Flugzeugbau, not even two years old at this point, had a truly capable design team of their own.

Design and development

Hamburger had already designed a biplane training aircraft of no particular distinction, the Ha 135 under their first designer, Reinhold Mewes. Mewes then left to join another small company, Fieseler. In his place Hamburger hired Richard Vogt, who had been working for a decade with Kawasaki Aircraft and was looking to return to Germany. Before leaving Japan, Vogt had been working on a new design for building wing spars, using a single chromaloy steel tube (often square or rectangular) that formed both the middle portion of the wing, and also served as a primary fuel tank.

When tenders were offered for the dive bomber program in 1934, Hamburger was not even invited to submit an entry. Nevertheless, Vogt was convinced that his new construction method would deliver a plane of the required strength with better performance than traditional designs, so he started work on Projekt 6 and submitted it anyway. He also started work on a more conventional biplane design as Projekt 7.

Projekt 6 was essentially a scaled-up version of Vogt's last design at Kawasaki, the Kawasaki Ki-5|Ki-5. Built entirely of metal and using a semi-monocoque fuselage, the design looked more like a fighter - specifically like the Heinkel He 112 - than a dive bomber. The wing used the tubular spar system, the inner portion of which was sealed as a fuel tank holding 270 litres. The design used fixed gear, so in order to reduce their length, and thus the drag, the wings featured a sharp reverse-gull bend at about quarter span. The wheels were mounted on two shock absorbers each, so the fairing around the gear was large enough to allow the mounting of a 7.92mm MG 17 machine gun for testing, and a 20mm MG FF if required. Two additional MG 17 guns were mounted in the fuselage decking above the engine.

Engines proved to be more of a problem. Vogt originally submitted the design mounting the new BMW XV. The future of this engine was in doubt, however, and the Reich Air Ministry (RLM) asked for the design to be re-submitted with the 650 hp Pratt & Whitney Hornet radial engine, then starting licensed production in Germany as the BMW 132. Vogt's team then modified the design to use the Hornet as Projekt 6a, or alternately the Rolls-Royce Kestrel as Projekt 6b. The RLM found the resulting design interesting enough to fund construction of three prototypes.

The Hornet-powered Ha 137 V1 first flew in April 1935, followed the next month by V2, and both were shipped to Travemünde that summer. It quickly became apparent that the Hornet engine was so large that the visibility during diving was greatly affected, and the RLM then suggested that the third prototype be completed as a 6b with the Kestrel, delaying it slightly to change the engine mounts and add a somewhat odd-looking radiator under the nose. By this point the definitive requirements for the dive bomber program had been drawn up, taken directly from Junkers' description of their own entry which had already been selected to win, calling for a two-seater arrangement. The Ha 137 was thus excluded, although realistically no other design had a chance to win anyway.

The RLM was nevertheless interested enough in the design to order another three prototypes with the new Junkers Jumo 210 engine. The radial-powered versions retroactively became known as the Ha 137A, while the inline powered versions became the Ha 137B. Further testing continued during 1936, and the prototypes also took part in the "doomed" dive bomber contest in June 1936, but the design was still being considered for the close support role instead of dive bomber. However, when Ernst Udet took over the T-Amt later that year he considered the close support role unnecessary, and informed Hamburger that they should stop work on the design.

The three Jumo-powered prototypes were built anyway during 1936 and 1937, eventually being used as testbed aircraft at Blohm & Voss. V1 was destroyed in testing during 1935 when the ammunition for its guns exploded, and V6 crashed in 1937, but the remaining four were used for years until a lack of spare parts for their engines eventually grounded them.

Vogt had also done some work on a navalized version of the design as Projekt 11, however the additional weight of the landing equipment, or floats as in the 11b, dramatically reduced range and made the design uninteresting.

pecifications (Ha 137 V4)

aircraft specifications
plane or copter=plane
jet or prop=prop
ref=
crew=1
capacity=
payload main=
payload alt=
length main= 9.5m
length alt= 31 ft 2 in
span main= 11.1 m
span alt= 36 ft 5 in
height main= 2.8m
height alt= 9 ft 2 in
area main= 22.7m2
area alt= 244.3 ft2
airfoil=
empty weight main= 2,437 kg
empty weight alt= 5,373 lb
loaded weight main= 3,800 kg
loaded weight alt= 8,377 lb
useful load main=
useful load alt=
max takeoff weight main=
max takeoff weight alt=
more general=
engine (prop)= Junkers Jumo 210A
type of prop=
number of props=1
power main= 455 kw
power alt= 610 hp
power original=
max speed main= 297 km/h
max speed alt= 185 mph
cruise speed main=
cruise speed alt=
stall speed main=
stall speed alt=
never exceed speed main=
never exceed speed alt=
range main= 575 km
range alt= 357 miles
ceiling main= 7,000 m
ceiling alt= 22,966 ft
climb rate main= 500 m/min
climb rate alt= 1,640 ft/min
loading main=
loading alt=
thrust/weight=
power/mass main=
power/mass alt=
more performance=
armament=
* 2 x MG 17 machine guns on faring
* Additional 1 x MG 17 machine gun or 1 x 20mm MG FF cannon
* 4 x 50kg (110 lb) bombs
avionics=

ee also

aircontent
related=

similar aircraft=

sequence=
Bü 134 -
Ha 135 -
Ha 136 -Ha 137 -
BV 138 -
Ha 139 -
Ha 140

lists=
List of military aircraft of Germany

see also=

References

Notes

Bibliography

* Green, William. "Warplanes of the Third Reich". London: Macdonald and Jane's Publishers Ltd., 4th impression 1979, p. 70-71. ISBN 0-356-02382-6.
* Wood, Tony and Gunston, Bill. "Hitler's Luftwaffe: A pictorial history and technical encyclopedia of Hitler's air power in World War II". London: Salamander Books Ltd., 1977, p. 133. ISBN 0-86101-005-1.