Country of origin:

Australia

Description:

Single-seat fighter bomber

Power Plant:

One CAC-built Pratt & Whitney R-1830-S1C3G fourteen-cylinder two-row air-cooled radial engine

Specifications:

History:

In an attempt to increase the performance of the indigenous CAC Boomerang fighter, consideration was given to increasing the power of the engine installed and, to this end, as the Pratt & Whitney Twin Wasp engine then fitted was not supercharged sufficiently to permit adequate high-altitude operations, it was decided to obtain a turbo-supercharger installation from an American Boeing B-17E Fortress to be fitted to a Boomerang.

A CA-13 airframe was taken off the production line, the aircraft chosen becoming A46-1001. Work commenced in July 1942 and a General Electric B2 exhaust driven supercharger and ancillary equipment were obtained from the USAAF. A Harrison intercooler was fitted into the fuselage behind the cockpit. The supercharger was installed in the fuselage on the starboard side, the engine exhaust being extended to feed the turbine. Test instruments were mounted in the rear fuselage with a camera to record in-flight data.

Also installed was a Curtiss Electric three-blade propeller as fitted to the standard Boomerang. Initial flight testing began on 13 January 1943 with Flt Lt John Holden at the controls. In March test pilot Greg Board took over testing and, because of overheating problems, it was decided to install fan cooling to cure the problem. The aircraft was found to be neutrally stable in the lateral plane but directionally unstable and the fin area was increased and re-designed. Lateral stability was improved by sweeping the wingtips. Attempts were then made to obtain a four-blade propeller to increase climb performance but this did not become available. The aircraft was handed over to the RAAF for evaluation by which time Greg Board had flown it to 12,497 m (41,000 ft).

Further development led to the CA-14A Boomerang, the same aircraft being modified, calculations indicating it would have better all-round performance than the Republic P-47 Thunderbolt and the Supermarine Spitfire VC. This conversion work was carried out in June and July 1943 and was to include the installation of a CAC-built R-2000 Twin Wasp engine, a B9 supercharger [in fact a B13 was fitted], a four-blade propeller, a ten-blade cooling fan mounted behind the propeller driven through reduction gearing, and other changes.

Some of the proposed changes were made to A46-157 to speed up the progress. A further increase to the fin area took place, and various aerodynamic improvements were made to reduce drag, including a more streamlined cowling around the engine, as well as some improvements in the contours of the wing roots. High-speed dive tests up to 644 km/h (400 mph IAS) were carried out on A46-27 and the centre-section leading-edges were straightened and swept forward.

Performance gains were significant and the Secretary of the Department of Aircraft Production was asked in June 1943 to recommend production of the CA-14A, with 200 aircraft to be produced before production commenced on the CA-17 Mustang, the licence-built variant of the North American fighter. At that stage it was considered 75 per cent of the tooling for the standard Boomerang could be used. The recommendation was to note the fact that the USAAF had many superchargers in store which would be available if production proceeded, and the CA-14A would be the best fighter available until the Mustang came into production.

A production batch of 120 Boomerangs with the R-2000 engine was recommended but the Australian War Cabinet only approved 50 under the CA-19 contract, and these were eventually completed with the R-1830 engine with a Hamilton Standard propeller. No four-blade propellers became available. This unit would have been expected to increase the climbing speed at all heights above 4,572 m (15,000 ft), and the aircraft’s maximum speed.

The CA-14A incorporated many experimental features in its design and further Type Trials were conducted. However, turbo-charging was falling out of favour at that time because of the slow response to throttle opening and finally the CA-14A program was cancelled, the aircraft involved, A46-1001, A46-157 and possibly A46-27 being used as test-beds for a CAC-designed and built four-blade propeller.

At about this time US high-altitude fighters were becoming available in the South Pacific and the need for the CA-14A had disappeared. A46-157 made a forced landing on 5 November 1943 and a week later A46-1001 made a forced landing at Geelong, VIC. In June 1944 they were both delivered to the RAAF fitted with cooling fans. A46-1001 was later parked in the surplus aircraft park at Laverton until 1947 when it was scrapped, the mainplanes being used subsequently in a structural fatigue research program.