Britain's Largest Flying Boat Takes The Air. A remarkable photograph taken from another machine showing Britain's largest flying-boat the short-metal six-engined bi-plane, matching her first, flight over the Medway at Rochester. She weighs 31 tons and has a wing span of 120 feet and her 5,580 h.p. is about the same as the German D.O.X., which is eighteen tons heavier. August 23, 1932. (Photo by Central Press Photograph).