The CA-15 Story

A modified experimental Boomerang, designated CA-14, had earlier flown in 1942, fitted with a General Electric 82 turbosupercharger, and CA-15 Turbo calculations were verified against performance figures from the CA-14. It then became apparent that the R. 2800-57W radial might not be available in sufficient numbers for the proposed CA-15 production, and in September 1944, after talks between CAC and the RAAF, an in-line engine CA-15 was proposed.

The engine chosen was the Rolls Royce Griffon 125, a new advanced engine based on the famous Merlin. Performance calculations with the Griffon 125 estimated a cruising speed of 290 m. p. h. At 25,000 feet, and a maximum speed of 495 m. p. h! It was decided to use a Spitfire auxiliary gearbox, and the Griffon was to drive a four-bladed Dowty Rotol 12 ft. 6 in. diameter dural propeller. However, in 1945 it was decided to fit the prototype aircraft with an earlier Griffon, the Mk. 61, until an advanced Griffon with a three-speed supercharger became available. The Griffon 61 was eventually to drive a four-bladed compressed wood propeller, and was to rotate anti-clockwise instead of the normal clockwise movement. Two Griffon 61s were acquired from England under a lend-lease agreement.

Construction

The CA-15, which was once unofficially known as the CAC Kangaroo, was an &II-metal monoplane incorporating the latest aerodynamic and structural refinements of its time. It featured a flush-rivetted, stressed skin and semi-monocoque fuselage, 36 ft. 3 in. in length. The 36 ft. span wing was a two piece structure with a low drag NACA 66 laminar flow aerofoil section. The aircraft stood 14 ft. 3 in. high. A teardrop canopy slid rearwards over the single cockpit. The twelve-cylinder Griffon 61 engine, with a two-stage two-speed blower, was rated at 2,035 h. p. , and drove a Dowty compressed wood 12 ft. 6 in. diameter propeller. Fuel tanks were installed in the wings and fuselage, totalling 220hp. Gals. 1000 and 30 Imp. Gals. (137 I) respectively. Provision was made for the carriage of either two 100-gallon or two 40-gallon drop tanks. A hand-operated primer was located in the cockpit.

A dowty engine-driven pump supplied hydraulic power to operate the landing gear and flaps, the: pressure fluid being fed into actuating jacks and operated by image contribute from the cockpit. The control system was conventional, consisting of all persons, elevators and rudder. The ailerons were fitted with electrically operated trim tabs, adjusted through the toggle switch on the Left side of the cockpit. The elevator and rudder had mechanically operated trim tabs, adjusted by trim wheels also located on the left side of the cockpit. Single-slotted flaps were fitted, with a take-off setting of 20° and landing of 50°. The landing gear was the Conventional hydraulically operated type, retracting inboard into the wing structure. An unusually wide track of 14 feet gives the CA-15 exceptional stability when taxying. Oleopneumat1c shock struts were incorporated. The tail wheel was also retractable, and was a Dowty-levered suspension unit, folding forward into the fuselage.

The instrument panel was of standard British layout and was Well equipped. The three-piece windscreen was made of 1½ in Bulletproof glass. 229 lbs of armour plating was fitted throughout the aircraft and provided good protection for the pilot. When Evaluated against the Mustang it was considered:

“The P-51D Mustang does not provide any protection from fire from 20mm calibre. The CA-15 provides 12½0 protection for the body with two 6 mm plates spaced 6 in. apart, and 9° with 20 mm plates for both head and shoulders.”

Downward vision over the nose, when compared with the Mustang was significantly better, with a vision angle of 8° compared with the Mustang’s 5¾. Due to the usual height of the CA-15, the pilot entered the cockpit by first climbing up the undercarriage leg onto the wing.

The CA-15 was armed with six 0. 5 in. Browning machine guns each with 250 rounds of ammunition stored inboard the guns: Two 500 lb. or two 1000 lbs bombs could be carried on Underwing hardpoints outboard of the undercarnage. Ten rocket projectiles could alternatively be earned, or six rockets with drop tanks installed.

Finally, the CA-15 prototype was complete. The RAAF allotted the aircraft serial number A62-1001. Taxying trials began on 12th February 1946, and after minor problems with the throtle and tailwheel operation, the aircraft was declared ready for its maiden flight.

First Flight

In the late afternoon of the fourth of March 1946, the CA-15 was rolled out onto CAC’s airfield at the Fishermen’s Bend factory in Melbourne, and test pilot Jim Schofield began his pre-flight checks. The sky was clear, the weather fine, a gentle northerly breeze being indicated by the windsock. At 6:10 pm the CA-15 began its take-off run and roared mightily into the air because the Sun had already set, daylight was rapidly disappearing 1:nd the flight lasted only 15 minutes. The test pilot reported noticeable but controllable torque-induced yaw on take-off, but no serious trouble was experienced in the handling of the aircraft”. Landing was effected without difficulty. Test flying then began in earnest, and problems were initially encountered with control balancing and “feel”, and difficulty of entry into the cockpit was criticised. The visibility from the cockpit was unanimously praised. Overall, the aircraft was looking very promising.

CAC test pilot Jim Schofield completed most of the company test flights, but three RAAF test pilots from the aircraft Performance Unit (APU) took the CA-15 up for a brief evaluation. The pilots were WGCDR J. E. Harper, SQNLDR D. R. Cuming, and SQNLDR G. C. Brunner. In his flight test report, SQNLDR Brunner concluded:

“This is a very pleasant, straightforward aeroplane. At present its handling is marred by the heaviness of the aileron and elevator control. When this is cured a very good aeroplane should result. The aircraft is easy to fly and has no apparent vices. The view in flight is very good, especially over the nose. The engine installation is very good, by far! Be smoothest Griffon installation I have ever flown behind.”

Twenty-three test and demonstration flights were completed by CAC before the aircraft, with 15 hours on the clock, was officially handed over to No. 1 Aircraft Performance Unit, Laverton, on 27th June 1946.

The CA-15 was received enthusiastically by the press. One Melbourne newspaper reported:

“As it is the CA-15 is claimed as it stands now to be the most efficient fighter in the British empire powered by a reciprocal engine.”

Another even speculated that the Griffon may even be replaced later on by a gas turbine engine.

RAAF Service

No. 1 APU commenced calibration and performance testing of the CA-15, and the performance figures obtained were quite staggering. A maximum speed of 448 m. p. h. was attained in “combat power” at 26,400 ft, and 432 m. p. h. At “rated power” was achieved at 32,700 ft. (During a handicapped race against a Cobb and Co. coach from Ballarat to the Melbourne exhibition grounds, the CA-15 was claimed to have averaged 502. 2 m. p. h. However, although this figure is correct, the aircraft had flown the distance in a shallow dive, so this speed was never achieved in level flight. ) The rate of climb was calculated by the RAAF as 4,900 min, and the service ceiling was 39,000 feet. The CA-15’s range of 2,540 miles at 5,000 feet would have made it ideal for long-range escort duties. Lord Hives, then head of the Rolls Royce company, inspected the CA-15 during a visit to Australia and commented that it was the best example of the installation of a Rolls Royce Griffon that he had ever seen, and at that stage, the Griffon was installed in the newest British piston fighter designs.

On the 10th of December, 1946, FLTLT J. A. L. Archer took the CA-15 for a flight from the CAC airfield to Point Cook. Approaching Point Cook, FLTLT Archer selected the undercarriage down, but the gear locked halfway down and the red lights remained on in the cockpit. The emergency hydraulic extension was tried, but this also failed to completely lower the undercarriage. It was later discovered that a ground test gauge in the undercarriage bay had burst, and all the hydraulic fluid had escaped. After vain attempts to shake the undercarriage up or down, and after burning most of his fuel, the pilot elected to put the aircraft down on the grass next to the main runway at Point Cook. The flaps, also being hydraulically operated, would not extend. The tailwheel, which had fully extended, touched the ground first, and then the massive machine stalled and thumped onto the ground. The intercooler scoop dug into the ground and the aircraft pitched forward on its nose before finally dropping and coming to rest. The aircraft had suffered considerable damage, but considering the circumstances, was remarkably intact. The pilot emerged unscathed.

After the ensuing investigation had been completed, A62- 1001 was returned to CAC in June 1947 for rebuilding. At this stage, it was becoming more and more apparent that the CA-15 had little future, as plans were already being made for the introduction of Vampire and Meteor jet fighters into the RAAF. It was not until 19th May 1948 that the CA-15 was returned to the RAAF after rebuilding, and a limited test flying program was conducted by the Aircraft Research and Development Unit until 1950 when it was decided to cancel the project completely. Apparently unaware of the historical significance of the sole CA-15, the RAAF transferred the aircraft from ARDU to No. 1 Aircraft Depot, also at Laverton, on May 1st, 1950, where this, the epitome of thoroughbred piston fighters was “converted to components”. The Griffon engines were returned to England under the lend-lease agreement through which they had been acquired.

The CA-15 was undeniably an outstanding technical achievement and a credit to the Australian aircraft industry. It is a tremendous pity that the aircraft was not preserved but unnecessarily destroyed. All that remains of the CA-15 are photographic and technical records of both CAC and the RAAF, but some of this too has, over the years, been destroyed through ignorance of its historical value.

The author gratefully acknowledges the assistance of Commonwealth Aircraft Corporation and its employees, RAAF Public Relations, Mr. J. A. L. (Lee) Archer and Mr. D. R. Anderson.