In early 1917, the Peterborough based woodworking company of Frederick Sage & Company designed a two-seat patrol floatplane for the Royal Naval Air Service based on Sage's Type 3 landplane trainer. Like the Type 3, the new design, the Sage Type 4, was a single-engined biplane. Pilot and observer sat in separate tandem cockpits, with the pilot occupying the front cockpit, while the wireless operator/observer sat in the rear cockpit, with both crew members having good visibility. The aircraft was powered by a single 150 hp (112 kW) Hispano-Suiza 8 water-cooled V-8 engine in the nose driving a tractor propeller. Undercarriage consisted of two main floats under the wing the a further tail float.[1] [2]
The prototype Sage Type 4a (serial number N.116[3]) first flew on 3 July 1917.[4] The type demonstrated excellent handing during testing, being capable both of flying aerobatic manoeuvres while still being stable enough to be easily flown "hands-off".[5] Despite this, the type was rejected for service as a patrol aircraft, but it was recommended that it instead be adapted into a float-plane trainer. The aircraft was fitted with dual controls and the engine mounting was modified to allow any one of a variety of 200 hp (149 kW) engines to be fitted. N.116 was converted to the new standard, being fitted with a Sunbeam Arab and flew as the Sage Type 4b on 17 May 1918.[4]
Sage also designed a revised version, the Sage Type 4c with folding wings of increased wingspan (39 ft in (12.07 m) compared with 34 ft 6 in (10.52 m) for the earlier aircraft and powered by a 200 hp Hispano Suiza engine, with a prototype flying on 12 October 1918.[6]
Both the Type 4b and 4c were adopted as standard training floatplanes for the RNAS, but the end of the First World War resulted in production plans being abandoned.[6]