With the imminent invasion of Australia came a call for an interceptor fighter to defend our shores. It was readily apparent that supplies from either England or America were going to be unreliable, so the decision was taken to build one here. This was not a new idea, for as far back as 1938, even before the first one was produced, the Wirraway was the subject of a study to guage the feasibility of turning it into a fighter. It was was quickly realised however that this particular route was a dead end.
With the urgency of this new call, the decision was taken to build a fighter using as many parts from the Wirraway as possible. This project was dubbed the "Wirraway fighter". A high rate of climb, good pilot protection, good fire power and good manoeuvrability were the desired features. To this end it was decided to arm the Wirraway fighter with 20 mm Hispano cannon, fit armour plating around the cockpit, oxygen bottles and oil tanks, and a powerful motor. The most powerful motor readily available was the Pratt & Whitney R-1830-S3C4-G, a 1200 hp twin wasp radial. The time given to complete the project was a ridiculous three months. Due to this restriction no prototype would be made.
Undaunted, the staff of CAC (Commonwealth Aircraft Corporation) threw themselves into the work, only to immediately strike problems. Due to the expected strain of battle, and the substantially greater roll rate, the outer sections of the wing were to be markedly shorter than those of the Wirraway, as well as being of a different section and length . The undercarriage also needed strengthening which in turn caused a re-design fo the undercarriage fairings. So the original idea of using the centre section of the Wirraway wing including the undercarriage was scrapped. Instead the section was rapidly modified within the original shell so that the Wirraway jigs could still be used.
The next problem was the cannon. A source was not found in the country, and there did not seem to be a firm that was able to manufacture a weapon in time without a sample. Fortunately an RAAF sergeant who had served in the middle east had brought an Hispano cannon home as a souvenir, and offered it as a pattern. Then it was discovered that we had no source of 20 mm ammunition. This was solved by deciding that the first of the new fighters would be armed with rifle calibre machine guns while the production of cannon and ammunition got under way.
The shortened fuselage was of steel tube construction as was the Wirraway, but the rear decking was wooden, and the rudder and fin were redesigned with a trimming tab and additional fin front attachment, changing that Wirraway part as well. The doubling of engine power required the re-stressing of the front section of the fuselage, and the expected stresses of battle the re-stressing of the rest of the airframe.
Sixteen weeks after the first drawing was produced, the first production model rolled out. Despite superficial similarities, it was obviously not just a modified Wirraway, and the name Boomerang was chosen.
Test flights filled the next two months, with no major flaws showing up, but a number of small annoying faults such as brake fade, and an excessively heavy rudder. These and other niggling things were seen to and the RAAF proceeded to fly the Boomerang against the Kittyhawk, Airacobra and Spitfire. In competition with both the P40 and the P39 the Boomerang held its own in all aspects except speed. The Spitfire however was superior in all aspects except range. In summation by no. 2 OTU the Boomerang was found to be wanting, and suggested that it would be totally outclassed by the Zero. It recommended that the new machine be used as a training plane, or in a home defence situation where it would not come into contact with Japanese fighters. If it ws sent to a forward area, night use only was advised.
This notwithstanding, the RAAF ordered in all, 250 Boomerangs, many of which served in New Guinea. A turbocharged version was designed and flown, but it never reached production. The more obvious shortcomings of the design led to a totally new fighter being designed, called the CA-15.
Eighty three & eighty five squadrons received their new fighter, and spent the war in home defence duties. Eighty four squadron went to New Guinea with theirs and operated them in their designed role as fighter interceptors without much success. After eight months they swapped them for P40s.
Four and five squadrons had the most notable success with the type. Its excellent manoeuvrability and rate of climb, combined with its unequalled pilot protection made it the perfect machine for army co-operation. With dazzling ability at low level, four and five squadron "Boomer boys" and their Wirraway counterparts became the bane of Japanese patrols. In radio contact with ground forces it was possible for a Boomerang with its engine throttled back to sneak up on the enemy, strafe them and disappear without the enemy having time to take a bead on them.
If the opposing forces were very close, not uncommon in New Guinea, the pilots would get close enough to identify uniforms before opening fire. If a ground force radio was out, a wire with a message attached to it would be strung between two trees, and the Boomer pilot would retrieve it with a hook. In one instance a detachment was under heavy fire from a tree top sniper nest. A Boomerang was seen nearby, and one digger put his slouch hat onto the end of his Owen gun and waved it over his head. The pilot noticed this, appraised the situation and obligingly cut the top of the tree off with his cannon.
Another role in which these nimble aircraft excelled was artillery spotting. After a recce they would inform the local artillery battery of the target and then fly around it as the bombardment came in, and direct the fire until the target was destroyed. If the target was out of range of the artillery, an RNZAF Corsair squadron would be led to the spot, and the Boomerang pilot would mark the target for them with a smoke bomb. In this way, to the Kiwis the Boomer boys became known as "Smokey Joes". Indeed 20 Sqn. RNZAF attributed the most effective strikes of their tour to Smokey Joes leading them to targets. Even the local American fighter squadrons liked the Boomerang, though for different reasons. The artillery missions were so annoying to the Japanese that they would always send fighters to intercept them, giving the P38 jockeys plenty of trade!
With the end of the war and the production of more versatile types such as the Mustang, production of the Boomerang ended and they were phased out of service. Ironically, shortly before the end of the war, Wirraway production was restarted and that machine was kept on the RAAF register longer than its replacement, the Boomerang.
Copyright © Felix Noble 1997
