Without doubt the most remarkable aircraft built by the Germans during
the First World War were the "R" (Riesenflugzeug) type giant machines with
four, five or six engines. The eventual degree of reliability that was
attained was a noteworthy achievement when it is considered that
everything connected with these unique aircraft had to be developed and
produced from scratch. There was no previous experience in the design of
aircraft of such gargantuan proportions. As an example of just one of the
many difficulties, which had to be faced, that of engine failure may be
instanced. Many of the first engines fitted in the Giants had been used
with excellent reliability in airships, but in the aircraft they blew up
(often literally) with monotonous regularity. This failure was eventually
discovered to be due to the fact that the engines were called upon to
produce upwards of 1,200 r.p.m. for considerable periods on take-off and
climb, whereas in airship installation they were never-or rarely-called
upon for more than a steady 800 r.p.m.
The Zeppelin Staaken R types had been developed, with varying engine
permutations, from the V.G.O. I, which first flew in April 1915, to the R
VI, in which production version had four high compression engines mounted
in tandem pairs - first four 245 h.p. Maybach and later 260hp Mercedes.
The wings were all basically the same, with a 42.2 metre wingspan and a
332 sq metre area.
VGO-III
-------
The third version, V.G.O.III, was a six-engined machine, with two engines
in the nose, geared to one propeller, and four engines in tandem push-pull
pairs in the wing-nacelles. This model was later re-named R.III, and had
6 x 172 Hp Mercedes D.III engines - a total of 1,032 Hp.
VGO-III: 11600 kg and 1032 Hp = 89% power loading.
This model was still under-powered, but improving. It only took 30 minutes
to reach 2000 metres and was a little faster than its 110 km/h predecessors.
Construction of these monster machines, which spanned almost 140 ft.,
was a complicated and lengthy process, and the total number of man-hours
must have been prodigious.
The fuselage was of wooden construction and basically a fabric-covered,
braced, box-girder. The upper longerons were in a horizontal plane on a
level with the airscrew axis for almost the whole of their length. The
lower longerons were parallel as far back as the gun position, where they
swept up in a straight taper to join the upper longerons in a horizontal
knife-edge. In the nose, behind the engine, was the bomb- release gear.
Aft of this position the two pilots sat side by side with dual wheel
controls, followed by the radio operator's and navigator's compartments.
On a level with the leading edges of the wings, provision was made for a
mechanic, who was mainly responsible for controlling the emptying of the
eight cylindrical fuel tanks so that trim was not upset. The spacious
dorsal cockpit accommodated two gunners, who were also able to fire below
the fuselage through a ventral position in the floor. The section of space
for stowage of eighteen 100 kg. bombs with a through passageway in order
to communicate with the fore part of the fuselage.
Of vast proportions, the wings were otherwise of orthodox construction
and based on two main spars, which were of double box-girder section. The
center panel of both wings extended as far as the engine nacelles and was
without dihedral, as was the whole of the upper wing. The outer panels of
the lower wing had marked dihedral. Taper on the wings was slight and on
the leading edges only. Steel-tube compression members were positioned at
interplane strut locations. The ribs were closely spaced and built-up
lattice-girder structures, with top and bottom spruce flanges held
together by double-lath web strips disposed zig-zag fashion. Ailerons were
of steel-tube framework and, being unbalanced, must have demanded
considerable muscle power-small wonder two pilots were required. All wing
surfaces were fabric covered.
Streamlined engine nacelles of alloy stringers and panels were
supported by twin "A" frames of steel tube located at the spar stations,
to which, in turn, the engine bearers were attached by a complex frame of
sheet steel and wood. The tandem-mounted engines were fitted with
gear-boxes, and the airscrews of the rear engines were driven through
extension shafts. A small cockpit was located between the engines wherein
the flight mechanic endured his lonely vigil. All struts were of
circular-section steel tube faired off with three-ply sheet.
An unusual feature of the Zeppelin VGO-III was the wide use of
aluminum in the construction of the tail. This was a huge biplane
structure, the size of a single-seat fighter, with a swept leading edge to
the tailplanes and inverse taper at the tips of the unbalanced elevators.
The tailplane section was of a reverse camber. The triple rudders were the
only control surfaces to be balanced, and all were fitted with fixed fin
surfaces.
Although no less than eighteen wheels were used in the undercarriage,
all three chassis were relatively simple vee-type structures. The axles of
the main chassis, located immediately under the engine nacelles, were
thicker than those of a railway wagon and supported two pairs of twin
wheels each end, which must have caused considerable drag. Axles were
bound to the steel-tube vees with elastic cord. The tailskid was a
conventional component fabricated from a single piece of ash and shod with
steel.
TECHNICAL DATA VGO-III
----------------------
VGO III, 1915
--------------------------------
Length: 24 m
Height: 7 m
Span: 42.2 m
Wing area: 332 sq m
empty weight: 7520 kg
MTOW: 11600 kg
weight/area ratio 35 Kg/sq m
max speed: 130 Kph
ceiling: 3000 m
Power: 6 x 172 Hp Mercedes D.III
Crew: 5
Payload: 2000 kg
Source: The German Giants by Haddow and Grosz, Putnam Books ISBN 0 85177 812 7
Source: German Aircraft of World War I by Gray & Thetford, Putnam Books, ISBN 0
85177 809 7
