The CAC CA-15 was an Australian piston-engined fighter that was considered as the successor to the Boomerang. Its development was ultimately hampered by the delays caused by wartime logistical problems, accidents, and the postwar arrival of state-of-the-art jet technology.
Projected to be more powerful and faster than even the Spitfire, in an alternative universe where the jet engine had not made such a timely appearance, the CA-15 would have been the fastest piston engined fighter ever made and perhaps Australia, rather than the USA, would now be world leaders in aviation.
Contents
Origins
The CA-15 was first proposed in mid-1942 at the Commonwealth Aircraft Corporation (CAC) by its general manager, Lawrence Wackett, as an updated version of the Boomerang fighter and was to use the Pratt & Whitney R-2800 Twin Row Wasp engine.
Interestingly, the chief designer was Friedrich David, an Austrian Jew who had escaped Germany before the outbreak of the World War Two, and who had been involved in the development of several German war planes as an employee of the Heinkel company.
David had next moved to Japan to work for the Tokyo Denki company, where he had contributed to the Aichi HED3A torpedo bomber responsible for the assault on Pearl Harbor that had caused the Americans to enter World War Two.
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Having fled to Australia, David was now entrusted with making another fighter that would inevitably face-off against many of the enemy planes he had helped create.
Development of the CA-15
By February 1943 a wooden mock-up had been assembled around the same time that the project was officially christened CA-15. In June 1943, following approval by the Royal Australian Air Force (RAAF), the design was registered as specification 2/43 issue 1 and development commenced.
In a revealing report from August 1943, Wackett made clear that the purpose of the endeavor was not even to create an end product, but to instead provide intellectual stimulation to the more junior members of the company:
“After considering all aspects of the matter, and having regard to the commitments in hand and others ahead in the form of establishment of CA-17 (Mustang) production, it is considered advisable to regard the CA-15 as an exercise to keep alive the spirit of design, rather than a war weapon for urgent development. Accordingly, it is proposed to employ some of the most promising younger design engineers on this job and to give it a low order of priority for the next six months, and avoid the job becoming an embarrassment to an already overloaded production department”.
Wackett did indeed get the challenge he wished for, but not in the way he intended, for the engineering team were soon forced to redesign the entire plane due to supply issues with the R-2800 engine. This initial setback would prove a harbinger of what was to come, for by October 1944 the enterprise was halted by the War Cabinet.
Optimistic that with the right argument the project could be resumed, Wackett kept development going under the radar, and was rewarded for his perseverance in February 1945 when development was once again given the green light after the British Air Ministry expressed interest in the design.
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The propulsion system of the CA-15 was rethought, and the R2800 replaced with a Rolls Royce Griffon 125 V12 engine. The envisioned power plants however also turned out to be unavailable, but with the British eager to get the ball rolling two Griffon 61 engines were loaned instead.
In October 1945 the Department of Aircraft Production issued order No. CS1502 for one CA-15 fighter, expected to be constructed with a budget of 150,000 dollars and flightworthy within 3 months. No longer a mere academic exercise Wackett, reassigning many of his workers to the job, now wanted something concrete.
Before the first prototype was assembled, a 1/6 scale model of the CA-15 was aerodynamically evaluated at the Aeronautical Research Laboratories of the Council for Scientific and Industrial Research (CSIRO), where it produced respectable lift-to-drag ratios.
Design
The CAC CA-15 was a piston fighter with a length of 11.03 meters, a height of 4.34 meters, and a loaded weight of 4,882 kilograms. Propelled by a Griffon 61 V12 engine with 2,035 horsepower, its predicted top speed was 495 miles per hour, while it was anticipated to have an altitude ceiling of 28,000 feet that it could climb to at 5570 feet per minute.
Its wings, which had a span of 10.97 meters, were the first of any Australian craft to utilize NACA 6000 laminar flow aerofoil sections, which markedly improved performance by reducing wing drag, and were much better than older configurations such as the British and American NACA 4 figure segments, which suffered from transitional flow over the upper wing surface.
The rest of the CA-15 was more conventional, and featured a semi-monocoque fuselage with stressed skin, a cockpit with a bubble perspex canopy protected by an armored glass windscreen, and a tailplane that had a span of 4.22 meters.
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Although never installed, the CA-15 was anticipated to carry either six 0.5 inch Browning machine guns each with an ammo capacity of 250 rounds, four 20 mm cannons loaded with 120 rounds each, or two of each armament, with mounting stations pre-built into the wing structure. Provision was also made for an undercarriage that could be equipped with one bomb of any type weighing up to 500 pounds.
Flight Trials
Evidently, the end of the war only a month previously in September of 1945 had done nothing to dampen enthusiasm for the CA-15, which began to take form in the earliest stages of the postwar era.
Following a gauntlet of structural evaluations at the CAC factory including wing torsional tests, fuselage torsional and bending tests, and fuselage stress distribution tests, the CA-15 was ready to make its flight debut.
Operated by CAC test pilot James Schofield, on March 4th 1946 the single CA-15, given the RAAF serial number A62-1001, took to the skies for the first time and flew for a total of 15 minutes. This was followed up by 24 more test flights lasting until mid-June 1946 investigating performance and handling characteristics, during which the controls, control surfaces, brakes, and engine were variously modified to achieve optimum results.
After 16.5 hours of flight time, on July 2nd 1946 the CA-15 was transferred to Laverton RAAF Base in south-west Melbourne for a slew of final assessments. It was here that the CA-15 got its nickname ‘Kangaroo’, after over-pressurized landing struts caused it to bounce up and down in the style of Australia’s national animal during a routine taxi run.
The CA-15 though would experience more misfortune when trials were paused until March 1948 after an incident on December 10th 1946, in which pilot Flight Lieutenant Lee Archer was forced to make a wheels-up landing after a major hydraulics failure.
What the CA-15 Could Have Been
The service span of the CA-15, a piston driven fighter which was surprisingly never fully tested, was ultimately cut short by the emergence of superior jet powered craft which largely replaced the older generation from the late 1940s.
The tragedy of the CA-15’s demise is even more pertinent considering that it was set to be the fastest piston-aircraft ever made.
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With a forecasted top speed of 495 miles per hour and climb rate of 5570 feet per minute, the CA-15 was going to be considerably quicker than the Tempest (402 mph / 4700 ft/min), Thunderbolt (402 mph), Mustang (434 mph / 3475 ft/min), and even the iconic Spitfire (443 mph / 5000 ft/min).
In one of the few recorded measurements to its name, it had already shown promising signs it would live up to expectations after making headlines in Australia on May 25th 1948 after clocking a speed of 502 miles per hour in a dive performed by Archer in Melbourne, but unfortunately the rapid pace of technological advancement was to stop it in its tracks.
Aftermath
Partially disassembled at RAAF Laverton, in 1953 the CA-15 was briefly considered as a possible entrant in the New Zealand Air Race, but this suggestion was quashed by RAAF High Command who had no further use for a plane that was now becoming increasingly outdated.
From here on out the CA-15 disappeared from the record for several decades, only to remerge in 1986 when an American aircraft enthusiast keen to build a replica asked the CAC for the blueprints.
Duly obliging, CAC packed them up in a box set for delivery, but in a twist of fate a rubbish collector accidentally picked it up and threw it into a local tip where the only known CA-15 schematics were incinerated before staff could catch up to them.
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Nowadays only a couple of sketches of some of the minor components and the general layout still exist, but without a detailed plan, the fastest piston-engined plane ever conceived will now certainly never see the light of day.
