The R.VI was the most numerous of the R-bombers built by Germany, and also one of the first closed-cockpit military aircraft (but the first was Russian aircraft Sikorsky Ilya Muromets). The bomber was reputedly the largest wooden aircraft ever built until the advent of the Hughes H-4 Hercules built by Howard Hughes, its wingspan of 138 feet 5.5 inches (42.2 m) nearly equaling that of the World War II B-29 Superfortress.
Design history and production
In September 1914, at the start of World War I, Ferdinand von Zeppelin visualised the concept of a R (Riesenflugzeug) bomber, to be larger than the Gotha G. Using engineers from the Robert Bosch GmbH, he created the Versuchsbau Gotha-Ost (VGO) consortium in a rented hangar at the Gotha factory. Alexander Baumann became his chief engineer, although later the team included other noted engineers including Zeppelin's associate Claudius Dornier, Hugo Junkers and Baumann's protogé Adolph Rohrbach. All of these Zeppelin-Staaken Riesenflugzeug designs used some variation of push-pull configuration in the setup, orientation and placement of their powerplants.
The first Riesenflugzeug built was the VGO.I in April 1915, using three Maybach airship engines. Baumann was an early expert in light-weight construction techniques and placed the four engines in nacelles mounted between the upper and lower wing decks to distribute the loads to save weight in the wing spars. The follow-on VGO.III prototype, a 3-engine open cockpit bomber, produced greater power and validated the soundness of the basic design.
In 1916 VGO moved to the Berlin suburb of Staaken, to take advantage of the vast Zeppelin sheds there. The successor to the VGO III became the Staaken R.IV prototype, the only "one-off" Zeppelin-Staaken R-type to survive World War I, powered by six Mercedes D.III and Benz Bz.IV engines that powered three propellers, a Tractor configuration system in the nose, and two pusher-mount on the wings. By the autumn of 1916, Staaken was completing its R.V, R.VI, and R.VII versions of the same design, and Idflieg selected the R.VI for series production over the 6-engined R.IV and other R-plane designs, primarily those of Siemens-Schuckertwerke AG.
With four engines in a tandem push-pull arrangement, it required none of the complex gearboxes of other R-types. Each bomber cost 557,000 marks and required the support of a 50-man ground crew. The R.VI required a complex 18-wheel undercarriage to support its weight, and carried two mechanics in flight, seated between the engines in open niches cut in the center of each nacelle. The bombs were carried in an internal bomb bay located under the central fuel tanks, with three racks each capable of holding seven bombs. The R.VI was capable of carrying the 1000 kg PuW bomb.
Although designed by Versuchsbau, because of the scope of the project, the production R.VI's were manufactured by three firms: nine by Schütte-Lanz using sheds at Flugzeugwerft GmbH Staaken, Berlin; six by Automobil und Aviatik A.G. (Aviatik) (the original order was for three); and three by Albatros. 13 of the production models were commissioned into service before the armistice and saw action.
One R.VI was converted on September 5, 1917, into a float-equipped seaplane for the German Naval Air Service, with the designation Type L and s/n 1432, having Maybach engines. The Type L crashed during testing on June 3, 1918. The Type 8301, of which four were ordered and three delivered, was developed from the R.VI by elevating the fuselage above the lower wing for greater water clearance, eliminating the bomb bays, and enclosing the open gun position on the nose.
R.VI serial number R.30/16 was the first supercharged aircraft, modified with a fifth engine, in this case a Mercedes D.II, installed in the central fuselage, solely to power a Brown-Boveri supercharger, enabling it to climb to 19,100 feet (5,800 m) in altitude. This same aircraft was later fitted with four examples of one of the first forms of variable-pitch propellers, believed to have been ground-adjustable only.
The units first served on the Eastern Front, based at Alt-Auz and Vilua in Kurland until August 1917. Almost all missions were flown at night with 1,700 pound (770 kg) bomb loads, operating between 6,500 and 7,800 feet (1,980 and 2,380 meters) altitude. Missions were of three to five hours' duration.
Rfa 501 was transferred to Ghent, Belgium, for operations against both France and Great Britain, arriving September 22, 1917, at St. Denis-Westrem (Sint-Denijs-Westrem) airdrome. Rfa 501 later moved its base to Scheldewindeke airdrome south of group headquarters at Gontrode, while Rfa 500 was based at Castinne, France, with its primary targets French airfields and ports.
Rfa 501, with an average of five R.VI's available for missions, conducted 11 raids on Great Britain between September 28, 1917, and May 20, 1918, dropping 27,190 kg (30 tons) of bombs in 30 sorties. Aircraft flew individually to their targets on moonlit nights, requesting directional bearings by radio after takeoff, then using the River Thames as a navigational landmark. Missions on the 340-mile (550 km) round trip lasted seven hours. None were lost in combat over Great Britain (compared to 28 Gotha G bombers shot down over England), but two crashed returning to base in the dark.
Four R.VI's were shot down in combat (one-third of the operational inventory), with six others destroyed in crashes, of the 13 commissioned during the war. Six of the 18 eventually built survived the war or were completed after the armistice.
Discovered crash site
Very little remains of these giant bombers, although nearly a century after the end of World War I amateur historians of the "Poelcapelle 1917 Association vzw" working in Poelkapelle, northeast of Ypres, identified a wreck that was found in 1981 by Daniel Parrein, a local farmer who was plowing his land. For a while it was thought that the wreck was that of French ace Georges Guynemer's plane; however that was discounted when repair tools were found at the site, and further research pointed that the engine was a Mercedes D.IVa, possibly of a Gotha G bomber. A comparison of recovered parts was inconclusive, since the parts were common to a number of aircraft other than the Gotha G.
In 2007 the researchers, Piet Steen with some help of Johan Vanbeselaere, finally made a conclusive ID after visiting one of the very few partial specimens (the distinctive engine nacelles) in a Krakow air museum. With the help of the Polish aviation historians, parts were identified as those of Zeppelin-Staaken R.VI R.34/16, which crashed on 21 April 1918 after a mission against the British Royal Flying Corps field at St. Omer, France. The R.VI was shot down, apparently by anti-aircraft fire of the British 2nd Army, while trying to cross the front line, killing all seven crew members.
Specifications Zeppelin-Staaken R.VI
Published - July 2009
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