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The Commonwealth Boomerang (also known as the Commonwealth Aircraft Corporation - or "CAC" - Boomerang) was of completely Australian indigenous design. Based on the CAC Wirraway, which in turn was spawned from the American NA-16 trainer aircraft produced by North American, the Boomerang was developed in direct response to the impending Japanese invasion of the Australian homeland. As with other facets of Australian war-production, aviation design was hardly given much attention prior to the war. However, with the consistent advancements made by Imperial Japan throughout Asia and in the Pacific, Australian soil was now ripe for the taking. It would seem that this British Commonwealth territory might be no more.

n late 1941, Lawrence Wackett, Manager and Chief Designer of CAC, began examining the possibility of designing and building a new domestically-designed fighter aircraft. The main challenge to this ambition was the fact that fighter aircraft had never been manufactured before in Australia; according to aviation author Rene J. Francillon, many experts considered that the licensed manufacture of a complete fighter aircraft would be beyond the capabilities of Australia's industry at that time. Wackett quickly made the decision to use elements of aircraft which were already being produced in Australia. Only two military aircraft were in production at the time: the CAC Wirraway, based on the North American NA-16, and the Bristol Beaufort bomber.

Overseas, the NA-16 had already become the basis of the North American NA-50 fighter (also known as the P-64), which had been used by the Peruvian Air Force in the 1941 Ecuadorian-Peruvian War. Crucially, CAC's licence to manufacture the Wirraway already contained a clause allowing the design to be modified.[4] Accordingly, Wackett decided to use the airframe of the Wirraway as a starting point for the design of the new domestic fighter; this choice had the advantage of requiring little additional tooling; it also had the effect of reducing the timescales that would be involved in the design phase and to establish the manufacturing of the new aircraft.

Although British designers had reworked the twin-engined Beaufort into a successful attack aircraft - the Beaufighter - this was not a suitable basis for the sought-after single-engine interceptor aircraft. However, Australian-made Beauforts used 1,200 horsepower (890 kW) Pratt & Whitney R-1830 Twin Wasp engines, which were made under license at the CAC plant in Lidcombe, Sydney. Another factor in favour of the engine was that it was already in use to power the Grumman F4F Wildcat fighters of the United States Navy, which helped make the Twin Wasp a logical choice to power the domestic fighter design.

Wackett promptly recruited designer Fred David, an Austrian Jew who had recently arrived in Australia as a refugee and, as David was technically an enemy alien, he had been interned by Australian immigration officials. David was well-suited to the CAC project, since he had previously worked for Heinkel in pre-Nazi Germany, as well as Mitsubishi and Aichi in Japan. As a result of this past, David possessed an excellent understanding of advanced fighter designs, including the Mitsubishi A6M ("Zero") (used by the Imperial Japanese Naval Air Service) and the Heinkel He 112 (a contemporary of the Messerschmitt Bf 109 and used in small numbers by Axis air forces in Europe).

In December 1941, the management of CAC issued its authorisation to proceed with the detailed design of the new fighter aircraft. The aircraft, which had received the internal designation of CA-12, used the wing, tail assembly, undercarriage, and center section of the Wirraway in combination with a new forward fuselage, which housed the larger Twin Wasp engine. It had a new single seat cockpit complete with a sliding hood, and carried an armament of two 20 mm Hispano-Suiza HS.404 cannons along with four .303 machine guns. The proposal was presented to the Australian Government, which promptly gave its approval; the government viewed the CA-12 as an appropriate insurance against the delay or cancellation of its order for US-built P-40 fighters, as well as a desire to maintain work at CAC; the ready availability of usable Wirraway components for the CA-12, the latter of which would greatly speed up any manufacturing program, was also viewed favourably.

Accordingly, on 18 February 1942, the Australian War Cabinet authorised an order for 105 CA-12 aircraft; shortly thereafter, the name Boomerang was selected for the aircraft. The ordering of production aircraft had been made in advance of any prototype being produced or maiden flight performed, thus the Boomerang had been effectively ordered 'off the drawing board'.

The Boomerang was of a utilitarian and highly conventional design, appearing much in line with those early stout fuselage monoplanes featured in the latter half of the 1930's. Wings - which were taken directly from the Wirraway design - were forward and low-mounted on the fuselage which, in turn, was of an all-new design. Additionally, the empennage and the retractable landing gear system were also of the preceding design's creation which essentially made the Boomerang something of a conversion model to her origins. The pilot sat behind the powerplant compartment and was situated under a glazed canopy. Armament was excellent and consisted of 2 x 20mm cannons in the wings and an array of 4 x 7.7mm machine guns in the wings.

With aircraft development hitting full stride in England and the United States, the Pratt & Whitney brand Twin Wasp series engine was deemed too underpowered for their new design. As such, a surplus of this engine type was made available for use in Australia and was promptly set into the Boomerang fuselage. The mating of such power and design produced an aircraft capable of just over 300 miles per hour with a ceiling of 34,000 feet and a range of 1,600 miles. The Pratt & Whitney radial was listed with an output of 1,200 horsepower. From design to flying prototype, the CAC team created the Boomerang in a short three month span of development.

At first glance, the statistics could appear quite pedestrian considering the type would be fighting against the powerful Nakajima, Aichi and Mitsubishi Japanese designs of the Pacific but the Boomerang surprisingly faired quite well in the theater - for the short time it was given to operate. Factors leading to its success were directly tied to the systems ability to withstand punishment, deliver formidable firepower onto its target through its combination machine gun and cannon armament and turn right alongside the best Japanese fighters.

As quickly as the Boomerang arrived into frontline service, it just as quickly gave way to the more capable American designs coming off the assembly lines at a record pace. Once surplus resources had been built up in the United States, both Canada and Australia (as well as Britain) were quickly fielding the now available American designs en mass. Nevertheless, the symbol that was the Boomerang would long remain the symbol of the nation that put forth a proud effort in the design and production of a wartime fighter when it needed one most.

Only some 250 examples were ever produced, making it one of the rarest production fighters of the war.