The Zeppelin-Staaken R.VI was a four-engined German biplane strategic bomber of World War I, and the only Riesenflugzeug (giant aircraft) design built in any quantity. The R.VI was the most numerous of the R-Bombers built by Germany, and also among the earliest closed-cockpit military aircraft (the first being the Russian Sikorsky Ilya Muromets). The bomber was reputedly the largest wooden aircraft to be produced in any quantity during World War I, with only the Siemens-Schuckert R.VIII prototype bomber of 1916–1919 being larger, and with the Staaken R.VI's wingspan of 42.2 m (138 ft) nearly equaling that of the World War II Boeing B-29 Superfortress, although significantly less than the 48 m (157 ft) span of the Siemens-Schuckert R.VIII.
Design and development By the autumn of 1916, Staaken was completing its R.V, the R.VI prototype, 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 Riesenflugzeug designs, primarily those of Siemens-Schuckertwerke AG. With four direct-drive engines in a tandem push-pull arrangement, and an enclosed cockpit, the R.VI design required none of the complex gearboxes of other R-types. Each R.VI bomber required the support of a 50-man ground crew. The R.VI required a complex 18-wheel undercarriage consisting of twin nose wheels and a quartet of four-wheeled groupings for its main gear to support the weight. It 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 1,000 kg (2,200 lb) PuW bomb. Although designed by Versuchsbau, because of the scope of the project, the production R.VI's were manufactured by other firms: seven 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 Flugzeugwerke. 13 of the production models were commissioned into service before the armistice and saw action. One R.VI was as a float-equipped seaplane for the Marine-Fliegerabteilung (Imperial German Naval Air Service), with the designation Type L and s/n 1432, using Maybach engines. After the first flight on 5 September 1917 the Type "L" crashed during testing on 3 June 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.
The special "R.30/16" test aircraft R.VI serial number R.30/16 was the earliest known supercharged aircraft to fly, with a fifth engine - a Mercedes D.II - installed in the central fuselage, driving a Brown-Boveri four-stage supercharger, about 6,000 rpm. This enabled the R.30/16 to climb to an altitude of 19,100 feet (5,800 m). The idea of supercharging an aircraft's propeller-driving piston engines with an extra engine used solely to power a supercharger was not attempted again by Germany until later in World War II, when both the Dornier Do 217P and Henschel Hs 130E experimental bomber designs each revived the idea as the Höhen-Zentrale-Anlage system. The R.30/16 aircraft was later fitted with four examples of one of the first forms of variable-pitch propellers, believed to have been ground-adjustable only.
Operational service The R.VI equipped two Luftstreitkräfte (Imperial German Army Air Service) units, Riesenflugzeug-Abteilung (Rfa) 500 and Rfa 501, with the first delivered June 28, 1917. 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 770 kg (1,698 lb) bomb loads, operating between 6,500 and 7,800 feet (2,000 and 2,400 m) altitude. Missions were of three to five hours' duration. Rfa 501 transferred to Ghent, Belgium, to attack France and Great Britain, arriving September 22, 1917, at 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 Britain between September 28, 1917, and May 20, 1918, dropping 27,190 kg (27 long tons; 30 short 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 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 SPAD S.XIII; 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 identification after visiting one of the few partial specimens (the distinctive engine nacelles) in a Kraków 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 Royal Air Force airfield at Saint-Omer, France. The R.VI was shot down, apparently by anti-aircraft fire of the Second Army, while trying to cross the front line, killing all seven crew members.
Variants
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