09/30/2016. Remarks by Johan Visschedijk: "In mid-1917, Arthur John Rowledge at the D. Napier & Son Ltd. at Acton, London, UK, started the design of a water-cooled twelve-cylinder engine with cylinders arranged in three groups of four, which were disposed in the form of a broad arrow (also known as a W-engine). Initially this engine was known as the Napier Triple-Four, and by September 1917 the manufacturers envisaged an output of 300 bhp at 10,000 ft (3,048 m). The engine was renamed Lion and one of the prototypes was experimentally fitted to a D.H.9 (serial C6078) and first flown at Farnborough on February 16, 1918, showing a number of teething problems.
By the summer of 1918 these problems, including the heating of the induction system, had been solved by the manufacturer and in September the first production Lion engine was fitted to the D.H.9 C6078, which had its airframe strengthened and had its retractable radiator increased in size. The aircraft was delivered to Martlesham Heath for service trials on October 20. Although it came too late for active service, the Lion engine proved ideal. Flown by Captain Andrew Lang and Observer Lieutenant Blowes, C6078 established a new altitude record on January 2, 1919, climbing to 30,500 ft (9,296 m) in 66 min 15 sec."
Read the type remarks on page 4943.