UNCONVENTIONAL LUFTWAFFE AIRCRAFT
Much has been written about the advanced thinking of the German aircraft industry
during World War Two. The German aircraft industry always seemed capable of
starting another project even as the Third Reich was literally crumbling around it.
At the end of the war, the allies found all kinds of design studies for advanced
aircraft such as ram jet propelled fighters (burning coal dust), supersonic bombers,
supersonic fighters, etc. Many of these design studies do bear striking resemblance
to aircraft that appeared in the 1950's such as the Mig 15 and the F-86 Sabre Jet.
Today an entire cottage industry now caters to modelers and history buffs (Luft46)
who have interest in this area. Yours truly always felt a little disdain towards
this cottage industry because the companies provide detailed models of aircraft that
were basically the figment of some German engineers imagination while ignoring some
very significant aircraft that the German aircraft actually did build. (It is the
equivalent of Revell manufacturing kits of the NCC 1701, a Vorlon ship, etc. while
not providing a model kit of the Apollo 11.) Here are some German aircraft projects
that were unconventional, were actually built and flown, but did not "make it".
AN AIRBORNE ODDITY
Perhaps the most unorthodox aircraft ever built and flown was the Blohm Und Voss 141,
being a totally asymmetric aircraft. The BV 141 had a fuselage containing the engine,
the entire cockpit was offset to starboard. See below for a photograph:
The Germans always considered short range tactical reconnaissance, army co-operation
aircraft as one of the more important types for their inventory. After all, the
primary mission of the Luftwaffe was to support army operations. The essential
features of such an airplane is 1) maximum field of view in all directions, especially
downwards, 2) ability to operate from temporary landing fields, 3) ease of handling
and good low speed capabilities to allow the pilot and observer to concentrate on the
task of observation, 4) engine of sufficient power to get the aircraft to and from
the scene of operations relatively quickly. It was considered de rigueur that a single
engined high-wing monoplane was the answer to these requirements.
In 1938, the HS (Henschel) 126 was entering service with the Aufklarungsstaffeln (H).
The HS 126 was a parasol wing aircraft and was thoroughly conventional being exactly
what the Riechsluftfahrtministerium (RLM) expected:
The RLM turned its attention to initiating the development of a successor for the HS 126
(the successor was to carry three crew members rather than two). Prototype contracts
were given to Arado (AR 198), Focke Wulf (FW 189), and Blohm und Voss (BV 141). Rarely in
the history of aviation has three aircraft designed for the same requirement were so
disparate in their conceptualization. The AR 198 was an orthodox design using the
standard high wing single engine formula. Today the AR 198 would look rather strange
to us because its extensive glazing in the ventral portion of the fuselage (lots of glass
below the air crew). This might have been the airplane the RLM would had selected except
the performance of the AR 198 was so lacking that not even a second prototype was built:
Kurt Tank of Focke Wulf ignored the single engined requirement and built a two engine
twin boom aircraft reminiscent of the P 38, the FW 189. The crew area was an extensively
glazed pod placed between the engine booms:
The FW 189 was considered an unorthodox approach to the requirements of a short range
reconnaissance aircraft and was viewed with suspicion by the more conventional personnel
of the Technischen Amt. However, the BV 141 was even more unconventional being considered
a degenerate expression of the designer's art. However the BV 141 proved to be remarkably
trouble free in its early flight testing. The original aircraft used a stepped cockpit
and was considered unacceptable and was replaced with an enclosure similar to the FW 189.
The RLM had to admit that the BV 141 possessed docile handling characteristics and met with
all the requirements of the design specification. Reluctantly a contract was placed for
five pre-production aircraft (BV 141 A-0). In its attempt to find a valid reason to reject
the BV 141, the RLM based its decision on the fact that it was marginally under powered.
Dr. Vogt of Blohm und Voss had foreseen this possibility and had begun the design of an
aircraft using a more powerful engine (BMW 801). The redesigned aircraft (BV 141 B) did
not prove to share the pleasant characteristics of its predecessor. The BV 141 B entered
a protracted development stage to eliminate its problems (structural strengthening, hydraulics).
By 1942, plans for any production of the BV 141 were cancelled when the reliable FW 189
was seen to be fulfilling all the roles required by the specification. In combat the
FW 189 proved to be a extremely effective aircraft becoming one of the more important
aircraft in the Luftwaffe's inventory. The RLM probably soon learned to appreciate the
fact that the FW 189 used two low powered engines (Argus AS 410 rated at 465 hp for
take off) rather than one high powered engine. This did not place any additional strain
on the production of high powered engines which were always in short supply. Also the
twin engined arrangement improved the combat survivability of the FW 189.
The RLM could never accept the strange appearance of the BV 141 and never really supported
the adoption of this airplane. Only thirteen examples of this oddity were ever built.
However, the BV 141 retains its place in aviation history as being probably the oddest
airplane ever built.
A RARAE AVES
By 1934, the coming demise of the biplane fighter was accepted by most of the world's major
air forces. The low or mid wing monoplane was to be the wave of the future for fighters.
However, there were some who speculated that the view provided by a parasol wing would be
worth the few miles shaved of the maximum speed by the drag of the bracing struts. Also a
parasol winged aircraft should be theoretically more maneuverable than a comparable low
wing aircraft (shorter total wing span). While few members of the Luftwaffenfuhrungsstab
(operations staff) had any serious doubts of the future of fighter development, it was
considered prudent to evaluate any possible alternatives. In 1934, development contracts
were awarded to Arado (AR 80), Bayerische Flugzeugwerke (BF 109), Heinkel (HE 112), and
Focke Wulf (FW 159). Of course the BF 109 would later win fame as the famous ME 109.
It was suggested to Kurt Tank that the Focke Wulf submission utilize a parasol wing
arrangement (Focke Wulf had just development a parasol winged trainer, the FW 56 which
was to be extensively used by the Luftwaffe). Kurt Tank was made well aware that the
other competing projects were to be low wing monoplanes; however, he considered it a
challenge that perhaps by careful aerodynamic design an aircraft could be developed
that offered performance comparable to low wing monoplanes. Design precedents were few.
There were only two previous parasol winged fighters with retractable landing gear and
these were US Navy aircraft that started out as biplanes. One of the most novel features
of the FW 159 was the landing gear. The main legs were double-jointed, providing a
form of levered suspension under compression, and each gear had an auxiliary oleo
strut that during retraction compressed the lower main leg joint, the upper joint
breaking, and the entire unit being lifted vertically though fairing doors barely
large enough to pass the wheels. While a model of ingenuity and functioning flawlessly
on test rigs, the landing gear proved to be troublesome during the course of testing.
Several times, flight tests of the FW 159 terminated with landing gear failures.
Every effort was made to achieve aerodynamic cleanliness and the FW 159 was a remarkable
clean airplane. However despite the efforts of the design team, it was so seen that
the FW 159 could not compete with either the HE 112 or the BF 109 in most aspects of
performance. The maximum speed ever clocked with the FW 159 was 252 mph at 14,700 feet.
The BF 109 V1 (prototype) was clocked at 290 mph using an engine of similar horsepower.
It was soon apparent that this type of aircraft was an anachronism lacking the performance
of the monoplane and the maneuverability of the biplane. Three prototypes of the FW 159
were built and flight testing continued until 1938. The FW 159 remains to be the sole
example of an attempt to build a high performance monoplane fighter with retractable
landing gear using a parasol wing. (The other two examples were modified biplanes.)
Perhaps it is a tribute to Kurt Tank's design genius that no one else ever tried this
approach to high speed fighters considering that if Tank could not get design concept to
work then no one else need try.