Martin P7M SubMaster

The Martin P7M SubMaster was an unbuilt aircraft designed by the Glenn L. Martin Company in the 1950s to meet a United States Navy requirement for an anti-submarine warfare flying boat. The design used boundary layer control to achieve very slow flight, intended to let the aircraft land on the open ocean in rough seas and deploy a dipping sonar. Martin developed it from a proposed variant of the P5M Marlin, the P5M-3, adding two General Electric J85 gas generators for the boundary layer system, with four Wright R-1820 radial piston engines projected. A mock-up was built, but the P7M and its Convair and Grumman rivals were cancelled when the Navy abandoned its open-ocean seaplane requirement.