Avro Tutor, RCAF, s/n 185, circa 1934. (SDASM Archives) The Avro Type 621 Tutor is a two-seat British radial-engined biplane from the interwar period. It was a simple but rugged basic trainer that was used by the Royal Air Force as well as many other air arms worldwide. Design and Development The Avro Model 621 was designed by Roy Chadwick as an Avro private venture metal replacement for the Avro 504. Conceived as a light initial pilot trainer, the biplane design featured heavily staggered equal-span, single-bay wings; the construction was based on steel tubing (with some wooden components in the wing ribs) with doped linen covering. A conventional, fixed divided main undercarriage with tailskid was used in all but the latest aircraft, which had a tailwheel. The Model 621 was powered either by a 155 hp (116 kW) Armstrong Siddeley Mongoose or Armstrong Siddeley Lynx IV (180 hp/130 kW) or IVC (240 hp/179 kW) engine; later Lynx-powered models had the engine enclosed in a Townend r...