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In page Fokker S.14 Machtrainer:

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According to aviation author Roland W. Harker, the notion of producing a Dutch jet trainer had originated from a speculative approach by British engine manufacturer Rolls-Royce to Fokker with drawings for a Derwent-powered jet trainer. Allegedly, Rolls-Royce had feared losing out on engine sales upon the large and lucrative market for jet trainers, particularly to the Goblin-powered de Havilland Vampire; the company had previously been rebuffed after attempting to raise interest with British manufacturer Miles Aircraft in producing a Derwent-powered competitor, and thus decided to approach Fokker.[4]