Zeppelin-Staaken E-4/20

The Zeppelin-Staaken E-4/20 was a four-engine all-metal passenger monoplane designed in 1917 by Adolf Rohrbach and completed in 1919 at the Zeppelin-Staaken works outside Berlin, and it was the first four-engine, all-metal stressed-skin heavier-than-air airliner built. It had a cantilevered monoplane wing built on a duralumin box girder, an enclosed cockpit and accommodation for 18 passengers plus a crew of five, with a toilet, a galley, radio-telegraph communications and separate baggage and mail storage. Its cruising speed was 211 kilometres an hour and its range about 1,210 kilometres. Test flown from 30 September 1920 until 1922, it was broken up on the orders of the Inter-Allied Commission, which judged it too much of a threat as a potential bomber to allow serial production. Rohrbach went on to found his own aircraft company, Rohrbach Metall-Flugzeugbau.