Attack CF-100 competitor to B-57?

toura said:

and detail

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As the U.S. Air Force had little time ahead to replace that aircraft, a specification was drafted in September 1950 for a light bomber capable of 1000 km/h speed, 12,000 m altitude and 18,500 km range. Moreover it had to be able to operate from rough airfields, carry both conventional and nuclear bombs and operate at night or in foul weather. Given the short deadline, manufacturers submitted variants of existing types: the Martin XB-51, the North American B-45 Tornado, the North American AJ-1 Savage, the Avro Canada CF-100 Canuck and the English Electric Canberra. The Savage was partly powered by piston engines, the B-45 was not maneuverable enough, the CF-100 was incapable of carrying a sufficient bomb load, and finally the British Canberra was prefered to the XB-51. Although it did not meet all the specifications, it could loiter for 2.5 hours around a spot located 1,400 kms from base, while its competitor could do only one hour at 650 kms.

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The CF-100, an all-weather interceptor, was too small and lacked sufficient range.

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The CF-100 was rejected because of insufficient range and payload.

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Colonel Frank Allen, USAF, worked on the requirements and was a member of the group of senior USAF officers who evaluated and tested five airplanes for the job. They narrowed the available contenders down to the Martin XB-51, a tri-jet bomber which had been flying for more than a year; the North American B-45 Tornado four-jet bomber and AJ-1 Savage two-motor carrier attack aircraft; the Avro Canada CF-100 Canuck twin-jet fighter; and the English Electric Canberra.
Allen wrote later that the most serious deficiency was the lack of poor-weather and night sensors and weapon-release systems. The Board concluded that only the Canberra had the available volume to accomodate those sensors and systems when they became available, and selected the Canberra as the B-26 replacement.

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To determine the usefulness of the CF-100 as a ground attack aircraft, bomb trials were conducted in 1954 at Malton. Aircraft 18105 was modified as a Mk.3 aerodynamically, and 14 bomb-dropping trips were flown over the Lake Ontario range. In all, twenty-one 1000 lb bombs were dropped and twenty 100 lb practice bombs. Problems encountered included bombs fouling each other when released, but the pilot's comments were favourable as far as performance went:
"Bomb dropping was satisfactory under conditions tested. Change of trim at moment of bomb or bombs release was small or negligible."
Bombs had been dropped at speeds between 230 and 550 mph.
The CF-100 was not developed any further in the bomb carrying mode. This was explained later in an Avro memo relating to the proposed STOVL (Short Takeoff and Vertical landing) CF-100: "At 27,000/30,000 lb. gross the CF-100 Mk.4 strength factor is about 7g limit. Between 10/12g limit is recommended for ground attack planes... Low strength factors and the cost incurred to correct the situation was one reason why the CF-100 ground attack proposal in 1954 was not developed."

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An unusual CF-100 proposal originated from Avro's project research group in 1958. This group, headed by Mario Pesando, proposed an STOVL (Short Takeoff and Vertical Landing) CF-100 for use in the ground attack role. At the time NATO was becoming increasingly aware of the powerful Soviet tank force poised on its borders. Also at this time Hawker was beginning to work on the P.1127 V/STOL strike aircraft.
The Avro proposal was simple, as the basic CF-100 airframe was readily adaptable to short takeoff/vertical landing configuration. The fuselage-hugging engines were well placed for C of G needs. The long undercarriage provided ample ground clearance, and the wing had originally been designed to carry ordnance.
In part the description of this aircraft in the brochure reads: "From the start a short takeoff, vertical landing version of this aircraft was considered for a ground attack role only, with a considerable curtailment in range compared with that of the all weather interceptor fighter presently in service. ...To achieve a reasonable distance for clearing a fifty foot obstacle, a thrust weight ratio of at least 0.85 is required so that on the assumption of 12,000 lb installed thrust per engine being available, the aircraft weight should be trimmed down to 28,500 lb. ...The use of the present airframe will mean that although not representing the best possible structure in view of its early conception, the marriage of this aircraft with the BE 53/2 engines should result in the ground attack aircraft with the ability to operate out of and into relatively confined spaces, being available sooner than an aircraft designed from the start to have V/STOL capabilities. It is reasoned that a proven airframe is already available which should give Avro considerable lead time over Hawkers, assuming the engines will be available at the same time a delivery is available to Hawkers... Aircraft structural changes necessary to the installation of the BE 53/2 will include reworked forward and rear nacelles, and some modification of the centre section to accept the highly variable thrust (both magnitude and direction) will be necessary. In addition, the running of trimming nozzle ducting will be a considerable problem although the present hollow wing leading edge will reduce the magnitude of the work required. A sophisticated auto-pilot will be vital to successfull takeoff and landing since for much of the time in these phases the flying control surfaces will be thoroughly ineffective."
Weight savings of 8065 lb were anticipated from such measures as removal of the fire control system, the fuselage fuel system, the heavier Orenda engines, and the rear cockpit, and the shortening of the fuselage by four feet and of each wing by eight feet.
The proposal concluded that such a CF-100 would have its limitations,e.g. in range, but "as a research vehicle for investigation of the technique of short or vertical takeoff and landing autopilot performance and as a working model for acquiring acquaintance with the environment from which short and vertical takeoff aircraft can operate a CF-100 modfied in this manner would be valuable."
Avro saw little future in the STOVL CF-100. A company memo of the day commented, "The CF-100 STOVL vehicle is unlikely to be more than 12-18 months ahead of operational Hawker P.1127s since both projects are tied to the same engine time scale with first flight late in 1960. At 27,000/30,000 lb gross the CF-100 STOVL is a much bigger vehicle than NATO, for example, requires for the ground attack role... Moreover, the CF-100 STOVL, as presently exploited, does not appear to have any more capability than the P.1127 with which to justify the larger size. In some respects it does not equal the P.1127 capability."
The Avro proposal never left the drawing board. Meanwhile work at Hawker continued, the P.1127 making its maiden flight in October 1960. From it grew the successful series of Harrier strike aircraft.

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While the CF-100 Mk.5M was being developed, so was a scheme to further boost aircraft performance over and above the use of such innovations as the Orenda 11R and vortex generators to improve ceiling. With the extra weight of the anticipated Mk.6, i.e. of its Sparrow missile system, more power was thought necessary. What Avro proposed in May 1956 was the retrofitting to each CF-100 wingtip of a Bristol Orpeus engine, instead of replacing the regular engines with the Orenda 11R with its marginal 20 percent thrust augmentation.
The Orpheus was a small engine, just 111 inches long and weighing only about 850 lb. It provided 4850 lb of thrust. With such boosters the CF-100 could fly beyond 50,000 feet, though Avro recommended partial pressure suits for the crew at such altitudes. The intended version was referred to as the CF-100 Mk.X. It never materialized. It was simply another of many CF-100 development ideas.

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