The de Havilland Gipsy engine is a 4-cylinder, air-cooled, inline engine that was used in the popular series of Moth aircraft designed by Geoffrey de Havilland in the 1920s. The original Moth was powered by a Cirrus engine, but de Havilland was not satisfied with the engine, itself developed from WW1 engines. In 1927 de Havilland had Major Halford design a replacement for the Cirrus. The resulting engine was tested in a unique manner. De Havilland built a little low-wing racer called the Tiger Moth and powered it with a 135-hp prototype of its new engine. After demonstrating its ability to withstand the rigors of racing, the engine was given smaller valves and lower compression to derate it to 100 hp, dubbed the Gipsy, and put into production. The engine proved to be reliable and was one of the first aircraft engines to go 500 hours between overhauls.
For all of this the new engine still had one drawback – its cylinders were still built on top of the crankshaft and therefore were sticking out of the top of the fuselage, right in the pilot’s field of vision. Lowering the engine was impossible as the crankshaft was directly connected to the propeller and the propeller could not be placed too low or it would touch the ground on bumpy fields. The solution was to invert the engine with the cylinders below the crankcase.
1,445 Gypsy engines were built and followed in 1930 by the Gipsy II (309 built) and Gipsy III (611 built) – the Gipsy III being the first inverted version. The later engines had enclosed valve gear and with the stroke increased to 5.5 inches (140 mm) the engine produced 120 hp. They came complete with baffles on the cylinders to assure good flow and proper distribution of the cooling air.
The Gipsy-powered DH 60 Moth was used for many record flights. Sir Francis Chichester flew his Gipsy Moth from England to Australia, continuing on to New Zealand and then across the Pacific to Japan. London secretary, Amy Johnson became the first woman to fly solo from Britain to Australia. She flew her Gipsy Moth (G-AAAH “Jason”), leaving Croydon, south of London, on 5 May, 1930 and landed in Darwin, Australia on 24 May after flying 11,000 miles (18,000 km). In May 1934, Jean Batten successfully flew solo from England to Australia in a Gipsy Moth. Her trip of 14 days and 22 hours beat the existing England-to-Australia record of Amy Johnson by over four days.
The Gipsy engine was used in many light aircraft of the time, including the Avro Avian, Blackburn Bluebird IV, de Havilland DH.60G Gipsy Moth, de Havilland D.H.71 Tiger Moth racer, Simmonds Spartan, Southern Martlet, Spartan Arrow and the Westland Widgeon.
Technical Details (Gipsy I):
Number of cylinders: 4
Power: 98 hp at 2100 RPM
Weight: 285 lb (129 kg)
Cylinder bore: 4 ½ inches (114 mm), stroke 5 1/16 inches (128mm)
Displacement: 319 cubic inches (5.2 litres)