Avro Canada CF-105 Arrow
The Avro Canada CF-105 Arrow was a delta-winged interceptor aircraft designed and built by Avro Canada. The CF-105 held the promise of Mach 2 speeds at altitudes exceeding and was intended to serve as the Royal Canadian Air Force's primary interceptor into the 1960s and beyond.
The Arrow was the culmination of a series of design studies begun in 1953 that examined improved versions of the Avro Canada CF-100 Canuck. After considerable study, the RCAF selected a dramatically more powerful design, and serious development began in March 1955. The aircraft was intended to be built directly from the production line, skipping the traditional hand-built prototype phase. The first Arrow Mk. 1, RL-201, was rolled out to the public on 4 October 1957, the same day as the launch of Sputnik I.
Flight testing began with RL-201 on 25 March 1958, and the design quickly demonstrated excellent handling and overall performance, reaching Mach 1.9 in level flight. Powered by the Pratt & Whitney J75, another four Mk. 1s were completed, RL-202, RL-203, RL-204 and RL-205. The lighter and more powerful Orenda Iroquois engine was soon ready for testing, and the first Mk 2 with the Iroquois, RL-206, was ready for taxi testing in preparation for flight and acceptance tests by RCAF pilots by early 1959.
Canada tried to sell the Arrow to the US and Britain, but no agreements were concluded.
On 20 February 1959, Prime Minister John Diefenbaker abruptly halted the development of both the Arrow and its Iroquois engines before the scheduled project review to evaluate the program could be held. Two months later the assembly line, tooling, plans, existing airframes, and engines were ordered to be destroyed. The cancellation was the topic of considerable political controversy at the time, and the subsequent destruction of the aircraft in production remains a topic for debate among historians and industry pundits. "This action effectively put Avro out of business and its highly skilled engineering and production personnel scattered".
Design and development
Background
In the post-Second World War period, the Soviet Union began developing a capable fleet of long-range bombers with the ability to deliver nuclear weapons across North America and Europe. The main threat was principally from high-speed, high-altitude bombing runs launched from the Soviet Union travelling over the Arctic against military bases and built-up industrial centres in Canada and the United States. To counter this threat, Western countries developed interceptors that could engage and destroy these bombers before they reached their targets.A. V. Roe Canada Limited had been set up as a subsidiary of the Hawker Siddeley Group in 1945, initially handling repair and maintenance work for aircraft at the Malton, Ontario, Airport, today known as Toronto Pearson International Airport. The next year the company began the design of Canada's first jet fighter for the Royal Canadian Air Force, the Avro CF-100 Canuck all-weather interceptor. The Canuck underwent a lengthy and troubled prototype stage before entering service seven years later in 1953. Nevertheless, it went on to become one of the most enduring aircraft of its class, serving in a variety of roles until 1981.
Recognizing that the delays that affected the development and deployment of the CF-100 could also affect its successor, and that the Soviets were working on newer jet-powered bombers that would render the CF-100 ineffective, the RCAF began looking for a supersonic, missile-armed successor for the Canuck even before it had entered service. In March 1952, the RCAF's Final Report of the All-Weather Interceptor Requirements Team was submitted to Avro Canada.
Higher speeds
Avro engineering had been considering supersonic issues already at this point. Supersonic flight works in a very different fashion and presents a number of new problems. One of the most critical, and surprising, was the sudden onset of a new form of drag, known as wave drag. The effects of wave drag were so strong that engines of the era could not provide enough power to overcome it, leading to the concept of a "sound barrier".German research during the Second World War had shown the onset of wave drag was greatly reduced by using airfoils that varied in curvature as gradually as possible. This suggested the use of thinner airfoils with much longer chord than designers would have used on subsonic aircraft. These designs were impractical because they left little internal room in the wing for armament or fuel.
The Germans also discovered it was possible to "trick" the airflow into the same behaviour if a conventional thicker airfoil was used swept rearward at a sharp angle, creating a swept wing. This provided many of the advantages of a thinner airfoil while also retaining the internal space needed for strength and fuel storage. Another advantage was that the wings were clear of the supersonic shock wave generated by the nose of the aircraft.
Almost every fighter project in the postwar era immediately applied the concept, which started appearing on production fighters in the late 1940s. Avro engineers explored swept-wing and tail modifications to the CF-100 known as the CF-103, which had proceeded to wooden mock-up stage. The CF-103 offered improved transonic performance with supersonic abilities in a dive. The basic CF-100 continued to improve through this period, and the advantages were continually eroded. When a CF-100 broke the sound barrier on 18 December 1952, interest in the CF-103 waned.
Delta wings
Another solution to the high-speed problem is the delta wing. The delta wing had many of the same advantages of the swept wing in terms of transonic and supersonic performance, but offered much more internal room and overall surface area. This provided more room for fuel, an important consideration given the inefficient early jet engines of the era, and the large wing area provided ample lift at high altitudes. The delta wing also enabled slower landings than swept wings in certain conditions.The disadvantages of the design were increased drag at lower speeds and altitudes, and especially higher drag while maneuvering. For the interceptor role these were minor concerns, as the aircraft would be spending most of its time flying in straight lines at high altitudes and speeds, mitigating these disadvantages.
Further proposals based on the delta wing resulted in two versions of the design known as C104: the single engine C104/4 and twin-engined C104/2. The designs were otherwise similar, using a low-mounted delta-wing and sharply raked vertical stabilizer. The primary advantages of the C104/2 were its twin-engine reliability and a larger overall size, which offered a much larger internal weapons bay. The proposals were submitted to the RCAF in June 1952.
AIR 7-3 and C105
Intensive discussions between Avro and the RCAF examined a wide range of alternative sizes and configurations for a supersonic interceptor, culminating in RCAF Specification AIR 7-3 in April 1953. AIR 7-3 called specifically for a two crew, twin engine, aircraft with a range of ) for a normal low-speed mission, and for a high-speed interception mission. It also specified operation from a runway; a Mach 1.5 cruising speed at an altitude of ; and manoeuvrability for 2 g turns with no loss of speed or altitude at Mach 1.5 and. The specification required five minutes from starting the aircraft's engines to reaching altitude and Mach 1.5. It was also to have turn-around time on the ground of less than. An RCAF team led by Ray Foottit visited US aircraft producers and surveyed British and French manufacturers, concluding that no existing or planned aircraft satisfied these requirements.In 1955 Avro estimated the performance of the Arrow Mk 2 as follows, from the January 1955 British evaluation titled Evaluation of the CF.105 as an All Weather Fighter for the RAF: "Max speed Mach 1.9 at 50,000 ft, Combat speed of Mach 1.5 at 50,000 feet and 1.84 g without bleeding energy, time to 50,000 ft of 4.1 minutes, 500-foot per minute climb ceiling of 62,000 feet, 400 nmi radius on a high-speeds mission, 630 nmi radius on a low-speed mission, Ferry range is not given, but estimated at 1,500 nmi."
Avro submitted their modified C105 design in May 1953, essentially a two-man version of the C104/2. A change to a "shoulder-mounted" wing allowed rapid access to the aircraft's internals, weapons bay, and engines. The new design also allowed the wing to be built as a single structure sitting on the upper fuselage, simplifying construction and improving strength. The wing design and positioning required a long main landing gear that still had to fit within the thin delta wing, presenting an engineering challenge. Five different wing sizes were outlined in the report, ranging between ; the sized version was eventually selected.
The primary engine selection was the Rolls-Royce RB.106, an advanced two-spool design offering around. Backup designs were the Bristol Olympus OL-3, the US-built Curtiss-Wright J67 version of the OL-3, or the Orenda TR.9 engines.
Armament was stored in a large internal bay located in a "belly" position, taking up over one third of the fuselage. A wide variety of weapons could be deployed from this bay, such as the Hughes Falcon guided missile, the CARDE Velvet Glove air-to-air missile, or four general-purpose 1,000 lb bombs. The Velvet Glove radar-guided missile had been under development with the RCAF for some time, but was believed unsuitable for supersonic speeds and lacked development potential. Consequently, further work on that project was cancelled in 1956.
In July 1953, the proposal was accepted and Avro was given the go-ahead to start a full design study under the project name "CF-105". In December, CA$27 million was provided to start flight modelling. At first, the project was limited in scope, but the introduction of the Soviet Myasishchev M-4 Bison jet bomber and the Soviet Union's testing of a hydrogen bomb the next month dramatically changed Cold War priorities. In March 1955, the contract was upgraded to CA$260 million for five Arrow Mk.1 flight-test aircraft, to be followed by 35 Arrow Mk. 2s with production engines and fire-control systems.