The AS.45 was designed in response to Air Ministry Specification T.4/39[1][a] for a single-engined advanced trainer to guard against potential shortages of current types, such as the Miles Master and North American Harvard.
[2][3] Airspeed's design, given the provisional service name Cambridge, was a low-wing monoplane of composite construction with a single piston engine and a tailwheel-type, retractable undercarriage.
[2] The Cambridge's fuselage had a steel tube structure, while the wings and tail were wooden, with plywood skinning.
[2][4] Pilot and instructor sat in tandem in an enclosed cockpit, with each crew position having doors on each side, one for normal use and one an emergency exit.
Data from The Hamlyn Concise Guide to British Aircraft of World War II[2]General characteristics Performance