It was while lecturing at Cranfield in the late 1970s and early 80s on the aerodynamic design of aircraft wings that the ideas discussed in this paper began to develop. My work on wing tip sails had led me to look in some detail at the flight of birds and their ability to vary wing camber. I realised that this was an attractive way to overcome the need to compromise between the design requirements associated with the different regimes of flight necessary with fixed geometry.

To be economically attractive, civil aircraft have to be capable of operating over a wide range of flight conditions. For example, an executive jet may be required to fly fast and low at light weight over a short stage length, such as London to Paris, on one day, and fly heavily loaded a much longer stage length the next, when it is desirable for the aircraft to fly high and at an economical speed.