 Alexander Baumann became his chief engineer, although later the team included other noted engineers including Zeppelin's associate Claudius Dornier, the 1915 pioneer of all-metal aircraft construction in Hugo Junkers and Baumann's protogé Adolph Rohrbach.Almost all of these Zeppelin-Staaken "Riesenflugzeug" designs used some variation of either pusher configuration and/or push-pull configuration in their engine layout, orientation and placement of their powerplants.The first "Riesenflugzeug" built was the VGO.I flying in April 1915, using three engines; two pusher and one tractor, with a span, four-bay interplane strut layout for its slightly swept-back leading edge biplane configuration, maintained throughout the entire Zeppelin-Staaken R-series of aircraft during World War I.