As an introduction to this paper, it would be worth defining a QSTOL aircraft, although it is not important that this be a rigid definition. The letters QSTOL stand for “Quiet Short Take-Off and Landing”, and may sometimes be abbreviated to STOL. A true STOL aircraft is capable of taking off and landing on a 2000 ft runway, this distance including the safety requirement to clear a 35 ft obstacle.

From the point of view of quietness, which is a subjective matter, dependent upon many factors, a quiet aircraft (according to one method of measurement) would produce a noise intensity no higher than 90 perceived noise decibels over an area of about 0·9 sq miles, of length 4 m, compared with an area of 16 sq m, length 14 m for such relatively quiet aircraft as TriStar and the DC-10, already in service (Fig. 1).

For the purposes of this paper, I shall call aircraft STOL if they can get in and out of runways up to 4000 ft long with a full payload, and any aircraft needing a longer distance will be conventional or CTOL aircraft.