Orenda Iroquois

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The Orenda Iroquois was a advanced turbojet engine for military use developed by the Canadian aircraft engine manufacturer Orenda Aerospace. As Canada's primary engine supplier and repair company it devleoped a number of engines. The most audacious and sophisticated design from this company was the Iroquois turbojet engine destined for the Avro CF-105 Arrow interceptor.

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1 Origins
2 Turbo Research
3 A.V. Roe Canada
4 Orenda PS.13 Iroquois design
5 Iroquois Testing
6 Orenda Iroquois Found
7 References
8 See also

[edit] Origins

During the Second World War, the National Research Council of Canada undertook a limited aerodynamics program. In 1942, after an initial study, the work on the Frank Whittlejet engine became the basis of further interest. The RCAF and NRC supported research in this field.

In May 1943, the Banks Report, a top secret Report on Development of Jet Propulsion in the United Kingdom recommended the setup of a cold weather testing centre in Winnipeg and an engine company as soon as possible.

[edit] Turbo Research

Following the advice of the Report, in March 1944, the Canadian government formed Turbo Research as a crown corporation in Leaside, now a part of downtown Toronto. Several members of the NRC teams that had surveyed UK developments, moved to the new company, including K.F. Tupper as chief engineer and Winnett Boyd, initially as the combustion engineer, but later as the chief designer.

Boyd quickly outlined two "paper designs", the TR.1 based on Whittle's centrifugal-flow design, and the TR.2 using an axial-flow design. The more promising axial-flow design led to work on the TR.3, a larger version of the TR.2. As work progressed, Boyd moved onto his own project, a smaller axial-flow design called the TR.4, later known as the Chinook. Work on the TR.3 was later abandoned.

[edit] A.V. Roe Canada

In 1945, the former Victory Aircraft plants in Malton were being converted into the new A.V. Roe Canada (Avro) plants. In the spring of 1946, the government decided to turn all engine development over to private industry, and sold Turbo Research to Avro. Paul Dillworth remained as chief engineer of the newly christened Gas Turbine Division, which was moved to Avro's plants just outside what is today Toronto Pearson International Airport.

Work on the TR.4 continued through this period, but in the summer, Avro asked them to produce a new 6,500 lbf (28.9 kN) engine for their CF-100 Canuck interceptor design. The resulting TR.5 Orenda design was essentially a scaled-up Chinook, with work continuing on the later to bring the production and test teams up to speed. The Chinook, the first Canadian-designed jet engine, first ran on March 1948, producing 2,600 lbf thrust.

The Orenda design was similar enough to the Chinook that prototype production was completed in less than a year. When it entered production, it was the most powerful engine in the world, a title it held until 1952. Almost 4,000 Orenda engines of various versions were built. In 1955, another reorganization led to the creation of Orenda Engines Ltd.,as well as Avro Aircraft Ltd.

[edit] Orenda PS.13 Iroquois design

In 1953, Avro Canada once again turned to Orenda to produce an engine for the Avro CF-105 Arrow project. Avro had originally intended to use one of three different engines all UK designs: Rolls-Royce RB-106, the Bristol B.0L.4 Olympus and a license-built version of the Olympus the Curtiss-Wright J67. These ran into delays.

Orenda quickly responded with the PS.13 Iroquois design. Once again, Orenda was able to prototype the new engine in a short period of time, starting development in 1953, completing it in May 1954, and building and running the prototype by December 1954.

The Iroquois design was based on simplicity and lightness. With this in mind, Orenda pioneered work in the use of titanium, with 20% by weight of the Iroquois (mainly the compressor rotor blades) consisting of this metal. Titanium has light weight, high strength and good temperature and corrosion resistance. It was estimated that the engine would be 850 lb lighter than if steel had been used. During the early 1950s, this material was in short supply, and the lack of knowledge of its physical properties and fabrication techniques created problems which had to be overcome. It was also very expensive relative to the more common materials such as steel and aluminum.

It was recognized that if the engine part could be designed with titanium, then the supporting structure could also be lightened, with an overall saving in weight. Other parts, such as gearbox casings were made with a magnesium alloy. Inconel was another light metal used to make the blades in the low pressure turbine assembly and the metal insulation blanket found at the rear of the engine. This heat resistant nickel-chrome alloy retains its strength at high temperatures and resists oxidation and corrosion. The primary reason for using these light metals was to save weight, and have an engine with a 5:1 thrust to weight ratio that could produce a sea level dry thrust of 19,250 lb (26,000 lb. with afterburner).

The design, development and manufacture of such an advanced jet engine was accomplished in an incredibly short time by the Orenda Iroquois engine team. The detailed design was completed in May 1954, and the first run was achieved in December 1954. The earlier Orenda 9 had more parts but produced less power. For example, the earlier engine weighed 2,560 lb. (1,160 kg) and produced 6,355 lb (2 883 kg) static thrust. The Iroquois weighed 5,900 lb. (2,675 kg) but was reported to have produced 30,000 lb (13 608 kg) static thrust with afterburner for take off. (The earlier engine did not have an afterburner.) The thrust was enormous for an engine of that time, and the highest dry thrusts produced in North America were recorded.

[edit] Iroquois Testing

Wind-tunnel tests revealed the engine's successful operation under sustained high inlet temperatures, and the ability to make normal relights up to 60,000 ft. (18 290 m), the limit of the wind-tunnel in which the tests were conducted.

A B-47 Stratojet was loaned in 1956 to the Royal Canadian Air Force to test the Orenda Iroquois turbojet for the Avro Canada CF-105 Arrow interceptor. Canadair Aircraft, the sub-contractor, attached the Iroquois engine to the right side of the rear fuselage near the tail, of all places, simply because there was no other place to put it. Flying the CL-52 was reportedly a nightmare. After the Arrow project was cancelled in early 1959, the B-47B/CL-52, with about 35 hours of engine flight tests to its credit, was returned to the US. Some sources claimed it was bent out of shape by the tests, but in any case, it was subsequently scrapped. The CL-52 was the only B-47 to be used by any foreign service.

By 1958, the Iroquois had completed more than 5000 hours of ground running, and many thousands of hours had been spent testing the engines' principal components at the Orenda test establishment at Nobel, near Parry Sound, Ontario.

During the testing period, the Iroquois was the most powerful jet engine in the world, rated at 19,250 lbf (85.6 kN) dry, 25,000 lbf (111 kN) afterburning. It was aerodynamically matched for peak performance at 50,000 feet (15,200 m) altitude and Mach 2 speed. After some 7,000 hours of development testing, up to a simulated altitude of 70,000 feet (21,300 m) and a forward speed of Mach 2.3, the program was canceled, along with the Arrow on "Black Friday," 20 February 1959.

[edit] Orenda Iroquois Found

The Canada Aviation Museum in Ottawa houses the nose and cockpit section of Avro Arrow RL 206, along with various wing and fuselage components, and a PS-13 Orenda Iroquois engine (see illustration). Another example is found at the Canadian Warplane Heritage Museum in Mount Hope, near Hamilton, Ontario.