Gotha G . IV The Gotha G . IV was a heavy bomber used by the " Luftstreitkräfte " ( Imperial German Air Service ) during World War I . Development . Experience with the earlier G . III showed that the rear gunner could not efficiently operate both the dorsal and ventral positions . Hans Burkhard ' s ultimate solution was the “ Gotha tunnel ” , a trough connecting an aperture in the upper decking with a large opening extending across the bottom of the rear fuselage . The Gotha tunnel allowed the top - side gun to fire through the fuselage at targets below and behind the bomber . A separate ventral 7 . 92 mm ( . 312 in ) machine gun could still be mounted , and there was even a provision for a fourth machine gun on a post between the pilot ' s and bombardier ' s cockpits , although this was rarely carried due to the weight penalty . The G . IV introduced other changes . The fuselage was fully skinned in plywood , eliminating the partial fabric covering of the G . III . Although it was not the reason for this modification , it was noted at the time that the plywood skinning enabled the fuselage to float for some time in the event of a water landing . Furthermore , complaints of poor lateral control , particularly on landing , led to the addition of ailerons on the lower wing . Production . In November 1916 , the " Gothaer Waggonfabrik " received a production order for 35 aircraft ; this was subsequently increased to 50 in February 1917 . A further 80 aircraft were ordered from the " Siemens - Schuckert Werke " ( SSW ) and 100 from " Luft - Verkehrs - Gesellschaft " ( LVG ) . Compared to the " Gothaer " aircraft , these license - built aircraft were slightly heavier and slower because " Idflieg " specified the use of a strengthened airframe . In order to counteract this , SSW built a number of highly - modified examples , including one driven by tractor instead of pusher engines , one with an extra bay added to its wing cellule , two with a new airfoil section for the wings , and one with a supercharger . None of these modifications had been fully evaluated by the end of the war . Late - production SSW G . IVs also usually incorporated the " Stossfahrgestell " auxiliary nosewheels and Flettner servo tab s developed for the G . V . Responding to a different performance issue , LVG overcame the tail heaviness of its machines by increasing the sweepback of the wings . Late production by SSW and LVG became obsolete , hence many aircraft were finished as trainers with lower performance engines ( Argus As . III or NAG C . III ) . The SSW - built trainers relocated the fuel tanks from the engine nacelles to within the fuselage , as on the G . V . Operational history . In March 1917 , the G . IV entered service with " Kagohl " 1 , which was redesignated " Kagohl " 3 upon receipt of the new machines , and the G . IVs were soon to be put to use in Operation " Türkenkreuz " - the strategic bombing of London . This was delayed when practice missions revealed faulty engine bearings that had to be replaced , and that the prevailing winds were stronger than expected , requiring the addition of extra fuel tanks . Additionally , it was discovered that the design of the fuel system prevented the main tanks from being completely utilised , and this problem had to be addressed as well . Around 30 LVG - built G . IVs were fitted with Hiero engines and 8 mm ( . 315 in ) Schwarzlose machine guns for Austro - Hungarian service . Another one was experimentally fitted with a 20 mm Becker cannon for ground attack . Postwar decommission . All surviving Gotha aircraft were destroyed in accordance with the terms of the Treaty of Versailles . The sole known exception was one Gotha G . IV in Polish possession .