Although Gull variants were powered by five different engines, those were all inverted inline air-cooled types driving two-bladed propellers, making for a neatly faired installation.
The final variant was the D.3 "Gull Six", similar to the D.2 "Gull Four Mk III" with the revised canopy and undercarriage, but with the much more powerful 200 hp (149 kW) de Havilland Gipsy Six 6-cylinder engine.