In April 1954, Canadair started work on the CL-28 airplane. In the middle of last December the first of these giant sub-hunters rolled off the final assembly line.

        The Royal Canadian Air Force looked hard before deciding on a successor for their present maritime aircraft, and the configuration finally chosen (and designated by the RCAF the CP-107) was an adaptation of the Bristol Britannia airliner.

        The CP-107 is basically a vehicle for carrying a vast array of the most up-to-date tactical equipment and weapons. The adaptation of the Britannia to this purpose resulted in one of the largest engineering design and development programs ever undertaken in Canada. By the time of first flight approximately one and three quarter million engineering man-hours will have been expended.

        The objective of basing the airplane on the Britannia was to take advantage of a known aerodynamic configuration, and to effect economy by using as far as practicable the proven and very efficient Bristol structural design. This objective has been achieved, and in fact the wing and enipennage are very much the same as the Britannia components.

        To ensure logistic support in time of emergency, it was a requirement that all utilized Bristol design was to be "Americanized" to cater for the use of North American materials, hardware and shop procedures. The British design was surveyed and a series of equal strength equivalents were selected and compiled as a conversion manual.

        Based on this manual, a systematic Procedure for "Americanization" was developed, and a relatively small group of draftsmen was able to convert and release a large number of drawings at a very early stage of the program, with consequent benefit to the manufacturing operations. Altogether about 7,000 wing, tail, flight controls and other drawings were      "Americanized" in this fashion.

Wing-Tail Changes.

         Although the wing and tail are basically of Bristol design, it was inevitable that some became necessary.

        Noteworthy among these was the introduction in the wing of electrically actuated spoilers to provide greater rolling power for tactical manoeuvring. These plain flap spoilers are arranged to extend proportionally to the aileron deflection at low airspeeds.

        To provide a flush HF antenna, the upper portion of the vertical tail was isolated from the remainder by a nonmetallic insert. The depth of this insert is about a foot and a half, and in an assembly this size its design and fabrication in molded fibreglass laminate and honeycomb was a challenging problem.

        In designing the Britannia, Bristol made wide use of the Redux metal to metal bonding technique. As a result, it became necessary to introduce this method of fabrication at Canadair.

        This required the establishment of a wholly new shop department and the development of a bonding process using Bloomingdale Rubber Co.. FM47 film type adhesive. Metal bonding is used extensively in the wing and tail structures for such applications as the attachment of doublers, stiffeners, etc. and to a lesser extent in the fuselage.

Fuselage Departure.

         The CL-28 fuselage departs from the Britannia configuration and is virtually of new design. The large bomb bays in the belly fore and aft of the wing and the multiplicity of cut-outs for other tactical equipment determined the basic structural arrangement. The cockpit enclosure was designed to provide maximum of visibility for the pilots and the nose section faired to house a manned search station.

        The nose observer's station is enclosed by an acrylic plastic fairing about five and a half by four feet in section and three feet deep which is formed from a single sheet of material to avoid the restriction of visibility by joints.

        At the tail of the fuselage a faired extension about 17 feet long is provided to house some of the tactical equipment. This component is made of resin bonded fibreglass honeycomb and laminate and is fabricated from two separately molded halves.

        Since the airplane is designed to operate over water, one of the design requirements for the fuselage was the ability to withstand ditching loads. A systematic schedule of water pressures was developed and the lower forward fuselage structure designed to withstand them.

        This aspect of the design was made more difficult by the discontinuous nature of the lower structure. To ensure a suitable water barrier at the nose, a solid bulkhead including a sliding door was introduced aft of the observer's station, and the large forward radome, which might cause unsatisfactory hydrodynamic behavior, was designed to shear off on impact with the water.

        To check the hydrodynamic behavior on ditching, a model of the airplane was built and an extensive series of ditching trials carried out in the hydrodynamic tank at the National Aeronautical Establishment in Ottawa.

Power Plant.

         Because the airplane is required to fly low and slow for long periods of time, the engine selected was the Wright 3350 Turbo Cornpound provided with direct cylinder fuel injection and with water methanol injection for increased take-off power.

        A power plant for this engine had to be designed and the philosophy of design adopted was the combination of lightness and simplicity with case of maintenance. A petal type cowling hinged from an engine-mounted nose ring was adopted.

        An oil cooler package assembly comprising the oil coolers, oil cooler ducting and automatic control flaps forms the lower aft portion of the power plant. This removable assembly permits pre-checking of the oil cooler system and also provides access from the bottom to the accessory section of the power plant.

        A test power plant was built and has been operating on a test stand for many months accumulating several hundreds of hours of operating time.

        To suit this power plant rather than the Bristol turbo-prop installation, considerable redesign of the nacelle structures was required. The most interesting feature of this redesign was the use, as a weight saying measure, of titanium for the whole nacelle structure between the front wing spar, and the power plant fire-proof bulkhead.

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