Country of origin:

Australia

Description:

Two-seat military trainer

Power Plant:

One 4,600 lbst dry, 6,900 lbst with afterburner, Rolls Royce Turbomeca RB.172-T-260 turbojet

Specifications:

History:

The CAC CA-31 was one of a series of projects designed by the Commonwealth Aircraft Corporation to meet a requirement of the RAAF for a supersonic trainer and light attack aircraft, being designed to facilitate pilots proceeding from the Macchi MB-326H to the GAMD Dassault Mirage IIIO, being expected to be much cheaper to purchase and operate.

In March 1964, when the Mirage was being delivered to the RAAF, CAC presented to the RAAF the design of an advanced supersonic aircraft to meet the needs mentioned, the only other aircraft available at the time able to meet the specification being the Northrop T-38 Talon. The initial design featured a delta-winged tailless aircraft with a max take-off weight of 3,175 kg (7,000 lb) powered by the 4,100 lbst General Electric J85 turbojet. Construction was to be all-metal semi-monocoque.

A full-scale mock-up was built. However, the General Electric J85 was considered to be too thirsty compared to newer technology engines and the decision was made to use the Rolls Royce RB.172 Adour, which was then being used in the BAe Hawk and SEPECAT Jaguar. The design was also enlarged and the weight went up to 5,670 kg (12,500 lb). Martin Baker zero-zero ejector seats, and four wing and two fuselage hard-points, were proposed. Typical ordinance load was to be six 227 kg (500 lb) bombs.

At one stage it was considered that two variants would be built, a single-seater for close support, in which the second seat would be replaced by a fuel tank; and a two-seat advanced trainer model.  It was also proposed a single 20 mm cannon or two 20 mm or one 30 mm cannon be installed. The possibility of a naval version for carrier operations was also looked at, as the new design was similar in size to the Skyhawk but was half the weight.

Critical areas of the aircraft such as the cockpit, fuel tanks and engines were concentrated in the central portion of the fuselage, no fuel or other equipment being carried in the wings, this leading to a simplified, efficient structure. Considerable attention was paid to the maintainability of equipment, airframe and engine. The major electronic and electrical equipment was to be located in the nose. At the time it was said that the new design provided a unique opportunity for the establishment of an aircraft industry to supply an advanced training aircraft to the RAAF, as the air force had need for such an aircraft, and an appraisal of aircraft available from other countries showed that there was room for a new approach in the field.

It was considered the necessity for reheat (afterburning) caused an apparent penalty in maintenance, complexity and weight but it was only required for short periods of take-off and supersonic flight, a total of perhaps 10 minutes on a training mission. Further, the very low drag of the aircraft would have permitted high subsonic speeds at sea level without the additional thrust from reheat. Because the aircraft was designed to fly at speeds of less than Mach 2, it was not expected to encounter special problems in the use of structural and transparent materials. The Company expected to be independent of overseas sources for all materials both in light alloys and steels; and fabrication would not require large forgings, milled skins, or special tools.

In the event, the design was not proceeded with and work on the design had ceased by the end of 1970 when the RAAF obtained the two-seat version of the Mirage. The mock-up of the CA-31 has survived, being presented to the Moorabbin Air Museum in Victoria in mid 1974. In about 1988 it was showing signs of deterioration and was taken to Hawker de Havilland (VIC) at Fishermens Bend for restoration. It remained in storage for many years until taken to the bi-annual Australian International Air Show at Avalon, VIC in February 2001 and placed on display.