Porte had taken the
Curtiss H-12, an original design by the American
Glenn Curtiss, and developed it into a practical series of flying boats at the Felixstowe station. They then took their
F.5 model and further redesigned it with better streamlining, a stronger hull using veneer instead of doped linen and U.S.-built 330 hp (later 400 hp)
Liberty 12A engines. The prototype was built and tested in England and the design then taken over by the Naval Aircraft Factory,
Philadelphia, where further modifications were made to suit their production methods under wartime conditions. The American-built version was also known as the
Curtiss F5L and (in civilian operation) as the Aeromarine 75. The F5L was built by the
Naval Aircraft Factory (137),
Curtiss (60) and
Canadian Aeroplanes Limited (30). Some were converted for civilian use by the
Aeromarine Plane and Motor Company in 1919. ==Operational history==