The firm produced a range of
water-cooled, mostly
inline engines up to about 1915. Green engines powered many pioneering British aircraft, including those of
A. V. Roe,
Samuel Cody, and
Short Brothers. They had several advanced features in common; cast steel single-piece cylinders and cylinder heads, two valves per cylinder driven by an overhead camshaft, white metal crankshaft bearings and copper and rubber-sealed water jackets. Manufacture was at the
Aster Engineering Company of
Wembley. When the
Great War broke out, the company was known for its
motorcycle engines and particularly associated with a "
pannier honeycomb" radiator design. It was already involved in aero-engine design. In 1909, the
C.4 had been the only motor to complete the tests for the
Patrick Alexander Competition but was not awarded the £1,000 prize, because the rules called for a engine while the C.4 only averaged . The competition was re-run the following year for more powerful engines: this time, Green gained the prize with the
D.4. Up to 1912 Green was the only source of all-British aircraft engines capable of producing and so the only choice when prizes were offered for all-British aircraft. The best known case is
John Moore-Brabazon's winning the £1,000
Daily Mail prize for a circular flight by a British pilot in an all-British aeroplane in his D.4-powered
Short Biplane No. 2 in 1910. for their water-cooled
six-cylinder "Engine No. 1", which was judged to possess the highest number of attributes desirable in an aeroplane engine. It was designed to deliver maximum power at low speed and weighed . Green continued to design motorcycle engines too, using cylinders similar to, though smaller than, those on their prize-winning aero-engine, having similar rubber-sealed copper jackets and removable overhead valve mechanisms designed to protect the cylinders from damage by broken valves, and forced lubrication throughout. ==Aircraft engines==