Submarines and their Weapons - Aircraft of World War II

universally jointed drive shaft and a cross-shaft connecting
the two rotor shafts, which were set at an
inclusive angle of 24 degrees, and inclined forward
by 6 degrees. The rotor blades were mounted so that
they were parallel when they were at 45 degrees to
the aircraft's centreline. The fin and rudder were
much larger than in previous Flettner designs, steering
being accomplished by a combination of rudder
movement and differential collective pitch control.
The 'Kolibri' proved to be very satisfactory
indeed, despite a pronounced vibration period as the
engine was run-up, with a maximum speed in level
flight of 150km/h (93mph), a vertical rate of climb of
91.5m/min (300ft/min), a hover ceiling of 300m
(985ft), and a service ceiling of 3290m (10,800ft). Its
range, with just the pilot and maximum fuel aboard,
was 300km (185 miles). Some 50 pilots were trained
to fly it, most of them by Flettner's test pilot, Hans
Fuisting. It was extremely manoeuvrable and very
stable and at forward speeds in excess of 60km/h
(37mph) could be flown hands-off once the controls
were balanced.
SEA TRIALS
From 1942, trials at sea aboard the cruiser Köln
demonstrated that the aircraft was usable even in very
poor weather conditions, and by the following year,
20 were in service with the Kriegsmarine in the
Mediterranean and the Aegean. In 1944, an order for
1000 Fl 282s was placed with BMW, which began
tooling up for production at its Munich and Eisenach
plants, but before manufacture could begin, both they
ROTARY-WING AIRCRAFT
Above: An American airman examines the tiny rotor-tip
jets which Friedrich von Doblhoff proposed to use to
eliminate the effects of engine torque in his WNF 342.
and the Flettner works at Johannisthal were very
badly damaged by Allied bombing. Anton Flettner
went on to design a 20-seat passenger helicopter, the
Fl 339, but never got beyond the development stage.
THEDOBLHOFF/WNF342
Friedrich von Doblhoff is rather less well-known than
the other helicopter pioneers in the Third Reich, but
the machines which he designed, and which were
built by Wiener Neustadter Flugzeugwerke in the
Vienna suburbs, represented yet another innovatory
approach to the solution of the torque problem.
Doblhoff used small rotor-tip jets to drive the blades.
A combustible air/fuel mixture was fed to small combustion
chambers in the rotor tips using a compressor
driven by a conventional piston engine. The mixture
travelled by way of the rotor hub and passages in the
rotors themselves, before being ignited. The piston
engine also drove a small fan which blew air over the
tail surfaces for the purpose of steering. Only four
prototypes were built; the first three had fixed-pitch
blades, and were only ever used in static/tethered
tests, but the fourth had a most ingenious (and very
complex) arrangement which allowed collective pitch
control. The last prototype was behaving well in its
trials and had been flown at speeds of up to 45km/h
(28mph) when the programme was halted by the
arrival of Soviet forces in 1945.