Zeppelin-Staaken VGO.I

Versuchsbau Gotha-Ost (VGO)

Industry	Aircraft manufacturing
Founded	1914
Founder	Count Ferdinand von Zeppelin, Hellmuth Hirth, Gustav Klein
Headquarters	Germany
Products	Zeppelin-Staaken VGO.I heavy bomber prototype

The Zeppelin-Staaken VGO.I, which was redesignated as the Zeppelin-Staaken RML.1 when operated by the navy, was a German heavy bomber constructed in 1915 that saw limited deployment during the First World War. Despite only a single unit being produced, it served as the foundational prototype for subsequent Zeppelin-Staaken Riesenflugzeuge ("giant aircraft"). The "VGO" label originated from its manufacturer, Versuchsbau Gotha-Ost, a subdivision of Gothaer Waggonfabrik. At the time it was built, this aircraft held the distinction of being the largest globally.

Design

The VGO.I featured a four-bay biplane layout with equal wingspans and a slight negative stagger between the wings. While largely conventional in overall design, it stood apart from contemporaries due to its immense size, biplane horizontal stabilisers, dual vertical fins, and its distinctive tricycle landing gear configuration. The cockpit was open and housed two pilots, while the crew also comprised a mechanic assigned to each of its three powerplants and two machine-gunners. One engine was positioned in the nose driving a tractor propeller, whereas the remaining two were installed in nacelles situated within the interplane gap, each driving pusher propellers. These nacelles were spacious enough to accommodate an onboard mechanic who could access them during flight, meeting the requirements set for Riesenflugzeuge. The fuselage incorporated a bomb bay capable of carrying up to 1,000 kilograms (2,200 lb) of ordnance. Defensive armament included two machine guns mounted within the fuselage—one firing upward and another downward—with later modifications adding machine guns at the front of each engine nacelle.

The initial powerplant arrangement proved insufficient, leading to the addition of two more engines—one added to each nacelle. In these configurations, pairs of engines within each nacelle were mechanically coupled to operate a single propeller. The airframe combined wooden elements with welded steel tubing and was covered mainly with fabric. Towards the end of its operational period, portions of this fabric covering were replaced with cellon material to help reduce visual detection.

Development

At the onset of World War I, Count Ferdinand von Zeppelin developed an interest in creating a very large aircraft to address the operational challenges posed by the airships his company was known for. He was informed about a pre-war initiative by Hellmuth Hirth and Gustav Klein aiming to construct a massive biplane capable of transatlantic flight, and enlisted their expertise to design an airplane that could deliver a 1,000-kilogram (2,200 lb) bomb over a distance of 600 kilometres (370 mi). With financial backing from Robert Bosch, Zeppelin supported the Versuchsbau Gotha-Ost enterprise, appointing Professor Alexander Baumann as the project leader. Initially, this initiative was privately funded, yet Zeppelin soon attracted both Army and Navy interest and support. Meanwhile, the War Office remained opposed to the endeavor.

Design efforts commenced in September 1914 and concluded by December of that year. However, construction faced delays in January 1915 due to unavailability of the Maybach HS engines. The aircraft's maiden flight occurred on 11 April 1915, followed by a transfer on 6 June to the Maybach factory in Friedrichshafen for evaluation by the Imperial German Navy. The HS engine represented a novel design but suffered from persistent reliability issues, culminating in an emergency landing near Geroldsgrün on 15 December, after two out of three engines failed mid-flight due to oil supply line malfunctions. The severely damaged aircraft was recovered and returned to Gotha.

The VGO.I underwent extensive rebuilding with numerous changes. These modifications featured redesigned engine nacelles that incorporated gunner stations at their fronts, as well as an enlarged and reconfigured tail assembly to enhance directional stability. Such alterations had already been integrated into the design of the VGO.II. Enhanced cooling systems were also implemented to address ongoing HS engine overheating problems. After these upgrades, the aircraft resumed flight on 16 February 1916 and was accepted into naval service by June.

Operational history

The VGO.I was designated RML.1, standing for Reichs Marine Landflugzeuge (Imperial Navy landplane), and a dedicated unit named Kommando RLM.1 was formed to conduct combat trials on the Eastern Front. Deployment to Auce occurred in June 1916; however, persistent engine and undercarriage malfunctions—described by aviation historian Jack Herris as "a tragicomedy of errors"—delayed its arrival until late July. During mid-August, RML.1 executed several bombing missions. On 15 August, it targeted the railway station at Sloka. The following day saw an attack on the Russian airfield at Läbara, with subsequent strikes on Ruhnu Island air station and a troop camp at Kemeri on 17 August. A planned second assault on Kemeri scheduled for 24 August was aborted due to engine overheating.

On 1 September, during a nocturnal mission outbound, two engines failed in rapid succession. The crew managed a forced landing within a pine forest. The fuselage was recovered and transported back to Staaken, but Kommando RML.1 was subsequently disbanded and its members reassigned. The aircraft itself underwent another reconstruction featuring new wings and engines. This iteration employed five Maybach Mb.IVa engines, each delivering power comparable to the original HS units. One engine remained nose-mounted as before, while four others were paired within two nacelles, each duo geared together to drive a single propeller. During this rebuild, portions of the fuselage covering were replaced with cellon, as part of an Unsichtbare Flugzeug (invisible aircraft) experiment aimed at reducing large aircraft visibility. A completely new tail structure was constructed, positioned higher on the fuselage, and this too received cellon covering.

The revamped VGO.I took flight again on 10 March 1917 but experienced an engine explosion leading to failure in the port nacelle engine. While returning to base, pilots applied strong rudder input to counteract asymmetric thrust, yet a previously identified issue with rudder pedals jamming at extreme deflections—noticed during ground testing—remained unresolved. Consequently, upon landing with jammed rudders, the aircraft became uncontrollable on the ground and collided with a hangar wall, resulting in one pilot's immediate death and another succumbing hours later. The VGO.I was not reconstructed following this accident.

Operators

Imperial German Navy

Kommando RML.1