The Avro 631 Cadet was developed in 1931 as a smaller, more economical, derivative of the Tutor military trainer, for flying club or personal use, and the Irish Air Corps purchased six from the drawing board, the first three delivered on 21 March 1932. The first prototype, G-ABRS flew in October 1931. It was publicly unveiled at the opening of Skegness airfield in May 1932. A total of 35 were built.
The Avro 631 also saw service with the military when six (C1-C6) were delivered to the Irish Air Corps in March 1932. One aircraft (C3) was written off in a crash in August 1932 so a replacement was ordered from Avro. This arrived in December 1934 as C7, and it was the only one not destroyed or written off during their service with the IAC. It was subsequently sol in 1945, going through several private owners and at least one crash landing before ending up in New Zealand. There, it was restored to airworthy condition, one of only two Avro 631s left in the world.
The Avro 631 Cadet was replaced in production in September 1934 by the improved Avro 643 Cadet, which had a revised rear fuselage with a raised rear seat, retaining the 135 hp (101 kW) Armstrong Siddeley Genet Major 1 engine of the Avro 631. In turn, this formed the basis for the more powerful Avro 643 Mk II Cadet with a 150-hp Armstrong Siddeley Genet Major 1A engine mounted 6 inches further forward; it was also strengthened and had improved parachute egress. An inverted fuel system was added and minor modifications were made to the wing bracing wires. This model entered service in 1935, and 69 Cadet IIs were built, including 34 fitted with a tail wheel for the Royal Australian Air Force.
The Cadet, while smaller and more economical than the Tutor, was still more expensive to run than competing two-seat light civil aircraft and was harder to hangar because of its lack of folding wings; so was mainly used as a trainer for flying schools or the military. By far, the largest civil user was Air Service Training Ltd, which operated 17 Avro 631s at Hamble, together with a further four operated by its Hong Kong subsidiary, the Far East Aviation Co. Air Service Training also operated 23 Mk II Cadets, with both these and the earlier Cadets remaining in service with Reserve Training Schools run by Air Service Training until they were impressed as ATC instructional airframes in 1941.
The other major operator was the RAAF, which acquired 34 Mk II Cadets, delivered between November 1935 and February 1939. The RAAF ordered an initial 12 Avro Cadets in 1935. Delivered from December 1935 they were joined by 22 more in 1938-39 while a 1938 order for another 20 was cancelled before deliveries began. These remained in service until 1946, when the surviving 16 were sold for civil use. Two of these were re-engined in 1963 with 220 hp (160 kW) Jacobs R-755 engines for use as crop sprayers. In the U.K., only two Cadets survived the war.
Produced from 1932 to 1939, a total of 104 were built.
Variants
Avro 631 Cadet
Initial version, powered by Armstrong Siddeley Genet Major I engine, 35 built.
Avro 643 Cadet
Raised rear seat, 8 built.
Avro 643 Cadet II
Powered by 150 hp (110 kW) Genet Major 1A, 61 built.
Operators:
Civil operators
Air Service Training Ltd
Military operators
Royal Australian Air Force operated 34 Avro 643 MkII Cadet.
Irish Air Corps operated 7 Avro 631 Cadets.
Portuguese Air Force
Chinese Nationalist Air Force – China had 5 Avro 631 deployed at Liuzhou Aviation School during the Second Sino-Japanese War, all of which were lost due to Japanese bombing in 1939.
Spanish Republican Air Force
Avro 631
Engine: 1 x Armstrong Siddeley Genet Major I. 135hp / 100 kW
Wingspan: 9.14 m / 30 ft 0 in
Length: 7.54 m / 24 ft 9 in
Height: 2.67 m / 8 ft 10 in
Wing area: 24.25 sq.m / 261.02 sq ft
Take-off weight: 863 kg / 1903 lb
Empty weight: 536 kg / 1182 lb
Max. speed: 190 km/h / 118 mph
Cruise speed: 161 km/h / 100 mph
Ceiling: 3962 m / 13000 ft
Range: 564 km / 350 miles
Avro 643 Mk II Cadet
Engine: 1 × Armstrong Siddeley Genet Major 1A seven cylinder radial, 150 hp (112 kW)
Length: 24 ft 9 in (7.55 m)
Wingspan: 30 ft 2 in (9.20 m)
Height: 8 ft 10 in (2.69 m)
Wing area: 262 ft² (24.3 m²)
Empty weight: 1,286 lb (585 kg)
Loaded weight: 2,000 lb (907 kg)
Wing loading: 7.63 lb/ft² (37.4 kg/m²)
Power/weight: 0.075 hp/lb (0.12 kW/kg)
Maximum speed: 116 mph (101 kn, 187 km/h)
Cruise speed: 100 mph (87 kn, 161 km/h)
Range: 325 mi (283 nm, 523 km)
Service ceiling: 12,000 ft (3,660 m)
Rate of climb: 700 ft/min (3.6 m/s)
Crew: Two
All Aero 