Linke-Hofmann R.I

The Linke-Hofmann R.I (Riesenflugzeug – giant aircraft) was a bomber aircraft designed and built in  Germany from 1916.

Development
Using encouraging data from test at the Göttingen laboratory Linke-Hofmann designed the Fuselage of the R.I to completely fill the interplane gap of the widely separated biplane wings, unfortunately the anticipated performance advantage was not realised. The capacious fuselage housed the crew compartments as well as the four engines and their clutches and combining gearboxes. Construction of the R.I was largely of wood covered by transparent Cellon in the first prototype, R I (8/15), and lozenge camouflage fabric in the second aircraft, RI (40/16).

Cellon was used with the intention of making the aircraft partially transparent and so less visible; however, the Cellon reflected sunlight, making the aircraft more visible, before quickly yellowing due to the effect of ultra violet radiation. It also shrank and stretched due to in-flight temperature changes, with detrimental effect on trim.

The forward section of the fuselage was divided into three levels. The top deck housed the pilots and wireless station, the middle the engine compartment and the lower the bombardiers, fuel tanks and payload. It has to be noted that this configuration would have made the aircraft top heavy when, after expending its fuel and weapon payload, it eventually landed.

The Linke-Hofmann R.I was powered by four in-board Mercedes D.IVa engines, rated at 260 hp (194 kW), coupled to a gear-box assembly which transferred power through shafts to two tractor propellers mounted between the wings, giving the plane a maximum speed of 140 km/h.

History
Flight testing of R.I (8/15) commenced in the spring of 1917 but was not satisfactory with the  flight characteristics leaving much to be desired, and the aircraft was difficult to land due to the pilot's inability to judge the ground elevation, because of the flight cabin configuration. In addition the flight controls felt mushy due to the warping and flexing of the light wings. One pilot who looked back on flying it called it "not an aircraft but a sickness". R.I (8/15) met with an accident at low altitude when the wings collapsed, all but one of the crew escaping. R.I (40/16) also succumbed to an accident when it nosed over on landing, not being repaired.

The remaining two aircraft ordered, R.I 41/16 and R.I 42/16 were both completed but no details of their flying history are known.