The ‘Down Under’ fighter

In December 1941, Japanese forces swept across vast areas of the Pacific and Southeast Asia and began to threaten Australia, which was almost defenseless because it had sent a large portion of its military to fight with the British against the Germans.

After devastating air raids on Darwin, Australia, on Feb. 19, 1942, the need for fighters was seen to be critical, but the Japanese conquest cut Australia’s supply line to the west along which British manufacturers had provided the Royal Australian Air Force with its fighters. Now British fighters would be shipped very long distances with consequent delays and losses, and even then the British aircraft industry was hard-pressed to meet the needs of the Royal Air Force. American fighter production was initially only for U.S. squadrons. To solve this problem the RAAF turned to the Commonwealth Aircraft Company and asked it to develop an “emergency fighter.” The CAC was producing two military aircraft already: the British Bristol Beaufort twin-engine bomber under license and the CAC Wirraway, a single-engine armed trainer similar to the American T-6. But the CAC had never built a fighter aircraft.

Fortunately, the American 1,200 horsepower Pratt & Whitney Twin Wasp engine for the Beaufort was built under license in Australia, so Twin Wasp was selected to power the Australian fighter design, dubbed the CA-12 “Boomerang.”

The Wirraway provided a starting point for the Boomerang’s airframe and the Boomerang used many Wirraway components. When complete, the Boomerang was a small, stubby fighter with short, thick wings (36-foot wingspan) and a 25-foot-long wood-covered, aluminum-framed fuselage. It carried the standard RAF armament of two Hispano-Suiza 20 millimeter cannons and four .303 machine guns mounted in the wings.

The cannons were a problem since the entire production of the British-made Hispano-Suiza 20 millimeter was dedicated to the RAF and no such weapons were manufactured in Australia. But an Australian airman had taken a  Hispano-Suiza as a souvenir while fighting in the Middle East and the CAC was able to reverse engineer the weapon for the Boomerang.

The Boomerang had an astonishingly short development phase — the prototype took to the air on May 29, 1942 — and test flights found that the CA-12 handled well and was exceptionally maneuverable. However, its general performance — especially its maximum speed of 265 knots — was mediocre because of its thick wings and generally unstreamlined design.

The Boomerangs were quickly sent to three operational squadrons to be used for home defense, but its low top speed and poor high altitude performance meant they rarely got close to Japanese aircraft. The one time a Boomerang did get in range of a Japanese bomber, the Boomerang’s guns jammed.

Fortunately, American Curtiss P-40s arrived from the U.S., and they were soon supplemented in early 1943 by the return from Europe of No. 1 (Fighter) Wing RAAF, flying Spitfires.

Relieved of its air-to-air mission, the Boomerang found its niche as a close support aircraft. The ground war in the Southwest Pacific was quite different from the island hopping invasions of the Central Pacific. The Southwest Pacific campaign was mainly a series of close quarter, small unit actions with few clear front lines.

The RAAF found the Boomerang’s maneuverability allowed it to keep close to the ground forces, and its cannon and machine gun armament were very effective against ground troops.

Additionally, it had unusually extensive armor plating for the pilot, and the aircraft’s simple wood and aluminum airframe could absorb considerable battle damage and was easily repaired.

Boomerangs in the New Guinea, the Solomon Islands and Borneo campaigns were not only used in the close support role but also as forward air controllers. The maneuverable Boomerangs, operating in pairs, would get in close to confirm the identity of a target and mark it with a 20-pound smoke bomb for the larger, more heavily armed strike aircraft.

For a time, the CAC worked to improve the Boomerang’s deficiencies in speed, climb and ceiling by adding a turbo-supercharger to the Twin Wasp. But by the time the new engine was ready, the Boomerang was a second line fighter and production Boomerangs were never fitted with superchargers. A total of 250 aircraft Boomerangs were built and quickly retired after the war.

(For questions or comments, contact Dr. Michel at  marshall.michel@spangdahlem.af.mil.)