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][3]
The prototype Sage Type 4a (serial numberN.116[4]) first flew on 3 July 1917.[5] 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".[6] 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.[5]
Sage also designed a revised version, the Sage Type 4c with folding wings of increased wingspan (39 ft 7+1⁄4 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.[7]
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.[7][nb 1]
Variants
Type 4a
Two-seat patrol seaplane, powered by 150 hp (110 kW) Hispano-Suiza 8A engine. One prototype built. Converted to Type 4b.[1]
Type 4b
Two seat floatplane trainer, powered by 200 hp (150 kW) Sunbeam Arab engine. Converted from Type 4a.[5]
Type 4c
Revised floatplane trainer with folding wings. Powered by 200 hp (150 kW) Hispano-Suiza 8B engine. One example built.[7]