Part One—Design Philosophy and Systems: Choice of the Three Rear‐Mounted Engine Configuration, and Description of the Basic Systems Available to Purchase

THE dc Havilland DH 121 Trident is a 600 m.p.h. airliner designed for economical short‐haul operation. It is intended to replace Viscount and Convairliners on regional networks with stages up to about 1,200 statute miles, and will be able to operate stopping services without intermediate refuelling over short‐range networks. The Trident can use runways of less than 6,000 ft. while carrying a full load and the cost per scat mile has been estimated to be 104 cents (or 09d.) while operating over stage lengths of 800 miles with a passenger complement of 101 economy class scats.