[7] In seaplane configuration, the undercarriage consisted of a single broad pontoon mounted beneath the fuselage,[5][7] with airbags on short struts under each wing.
[2] The S.45 flew for the first time on 24 May 1912 as a landplane with Lt Spencer Grey at the controls, and was accepted for Navy service with the serial number T.5[2] ("T" signifying "tractor"[5]).
[8] Although evaluated by Capt John Salmond as underpowered,[8] it flew regularly until damaged beyond repair in a landing accident on 3 December when it stalled on approach.
[8] Meanwhile, the S.45 underwent considerable modification, including a new engine cowling, a built-up coaming around the cockpits, revised ailerons, and upper wings of greater span.
[8] In Royal Naval Air Service hands, the aircraft were re-engined with 100-hp (75-kW) Clerget rotary engines and assigned serial numbers 1268 and 1279.