The first aircraft (s/n 1415) was powered by two handed 155 hp (115.58 kW) Sunbeam Nubian engines driving four-bladed propellers, in nacelles sitting on the upper surface of the lower mainplanes.

At the rear of the fuselage a biplane tail-unit with twin fins and rudders provided control and stability in pitch and yaw.

[1] Two bungee-sprung plywood-covered main floats with twelve watertight compartments supported the aircraft through a divided strut structure which left clearance for dropping torpedoes from under the fuselage.

For ground handling ashore the aircraft sat on beaching dollies under the main and tail floats.

Other changes included four ailerons, one on each wing, instead of just the upper mainplanes, engine nacelles raised clear of the lower mainplanes and scalloped trailing edges through the use of steel wire trailing edge members, (a retrograde step as the wire corroded quickly causing damage to the fabric covering).