shelldrake wrote:
Thanks Mark
great collection, can you add any more details on the Boomerang with the 4 blade prop assembly?
Shelldrake
There were 249 production Boomerangs built across the CA-12, CA-13 and CA-19 models which had relatively minor differences.
The 250th example was the CA-14, A46-1001, fitted with the P&W 1830 as per other Boomerangs, but modified to carry a GE turbocharger from a B-24 in the rear fuselage on the starboard side. This modification arose from combat trials between an early Boomerang, P-39 and P-40.
Other than the turbocharger fitted on the starboard rear fuselage, there was an air intake on the port rear fuselage, the fin had a modified leading edge/tip.
The CA-14 improved performance at altitude with 348mph at 28,000' compared to 305mph at 15,500' for a standard Boomerang, However the CA-14 suffered heating problems.
The intention of this design work was to produce a revised Boomerang fitted with an R2000, and to overcome the heating problems A46-1001 underwent modifications to become the CA-14A.
The CA-14A deleted the air intake from the port rear fuselage, and instead took its air from the cowling, the turbocharger remained on the starbard rear fuselage, and the fin and rudder were squared off.
A major improvement in cooling was achieved through the use of a geared engine cooling fan fitted behind the propellor, and a moveable intercooler exhaust duct behind the canopy.
The improvements of the CA-14A was intended to achieve a speed of 372mph at 27,000' and a climb rate of 1,700' per minute at 30,000' compared to the 500' per minute of the standard Boomerang.
While the CA-14 and the CA-14A both flew with the standard 3 blade propellor, it appears that another R&D Boomerang A46-157 was trialled with a four blade Curtiss Electric prop in preparation of the intended use of R2000 in production examples.
An improved version of the Boomerang was originally concepted around the R2800 but limitations of the steel tube fuselage resulted in the focus around a R2000 development.
The CA-14A and R2000 development gave way to a new fuselage development and return to the R2800 powerplant that began the design evolution of the CA-15.
Although the Griffon powered CA-15 is considered by many to simply be a P-51 derivative, its design is a direct extension of the CA-14A and the Cannon Fighter Wright Cyclone developments planned for the Boomerang, and the need to develop a new fuselage to carry the R2600.
The models show the CAC Factory trials Boomerang A46-157* with its 4 blade prop, in front of the CA-14A A46-1001 with its 3 blade prop and prototype yellow "P" marking, closer to the camera from that model is the earlier CA-14 A46-1001 sporting its air intake on the port side of the fuselage.
* It is unclear to me if the 4 blade prop was fitted to the CA-14A A46-1001, or the standard Boomerang A46-157 which was used by CAC for other development work, and was also fitted with the geared fan, this model shows the modified tail of the CA-14A, but does not carry the yellow "P" marking which A46-1001 carried to its demise at Laverton from scrapping, I therefore think this model is actually portraying A46-157, although I am unaware of it carrying the modified fin/rudder? However I know these modellers have sought significant assistance by historians so it would be expected to be accurate.
regards
Mark Pilkington