Canadair CL-84

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Image:CanadairCL-84DynavertSerialCX8402.jpg

The CL-84 was a Canadian V/STOL turbine tilt-wing monoplane designed and manufactured by Canadair between 1964 and 1972. Only four of these experimental aircraft were built and flown, despite the fact that it was very successful in the experimental and operational trials carried out between 1972 and 1974.

Two of the CL-84s crashed due to mechanical failures, but no loss of life occurred as a result of these accidents.

1 Description
2 References
3 Specifications
4 Trivia
5 Related content

[edit] Description

The wing and the powerplants of the aircraft could be tilted hydraulically so that the wing incidence changed through 100 degrees from a normal flight angle to those for STOL and VTOL. The incidence of the tailplane (or stabilizer) was automatically altered to deal with trim changes as the wing-incidence varied.

Contra-rotating rotors on a vertical axis in the tail provided fore-and-aft control during hovering and transitional flight. The propulsion and lifting propellers were handed (ie revolved in opposite directions) and were interconnected by shafts through a central gearbox from which the tail rotors and accessories were also driven. The thrust from the propellers was matched automatically except when over-ridden by the pilot for lateral control in slow or hovering flight. A mechanical "mixing" unit was used to adjust the functions of the various controls in the different modes of flight.

Two 1,500 shp Lycoming T53 shaft-turbines were used to drive 14 ft four-bladed propellers. The engines were connected by cross shafts, so that in the event of the failure of one engine, it could disconnect and both propellers be driven by the remaining engine.

The CL-84 was evaluated for the U.S. Navy, with some deck landings made. However, no contract resulted. The CL-84 first flew in hover on 7 May 1965. A prototype and three evaluation aircraft were built.

The three CL-84s that flew made a total of over 700 flights. They were flown by 36 pilots from Canadian, UK, and U.S. military and civil agencies.

There were two main reasons for the technical success of the CL-84 design. Aerodynamic considerations were given a very high priority, and the controlling of power was kept as simple and direct as possible.

The propeller disks extended slightly beyond the wingtips, so the whole of the wing (except for the portion above the fuselage) was immersed in the propeller slipstream. This, together with full-span leading edge and trailing edge flaps which were programmed with wing tilt angle, ensured that the wing was never stalled. Trim changes were minimized by programmed tilting of the tailplane. All programming was based on extensive testing in the wind tunnel and on an outdoor mobile test rig.

The power of both engines was controlled by a single "power lever" in all flight regimes. To provide crisp thrust control during hover, movement of the power lever caused a direct adjustment of blade angle, analogous to the collective pitch control of a helicopter, with the propeller cpu governor making a follow-up adjustment of blade angle to maintain the selected rpm. The direct adjustment of blade angle was faded out automatically as the blade angle increased with increasing forward speed.

The only unfamiliar control function the pilot had to deal with was the wing tilt control, which was a switch on the power lever (and took the place of controlling the flaps). The combination of smooth aerodynamics and simple power control made it easy for fixed-wing pilots to perform transitions between hover and wing-down modes on their first flight in the CL-84.

[edit] References

Airliners.net photo 0108113 [1]
Canada Aviation Museum CL-84 pageCanada Aviation Museum CL-84 page accessed 09 October 2006.
"CL-84 Aircraft Operating Instructions." available on CD from http://www.flight-manuals-on-cd.com
F.C. Phillips. The Canadair CL-84 Experimental Aircraft - Lessons Learned. "AIAA-1990-3205," AHS, and ASEE, Aircraft Design, Systems and Operations Conference, Dayton, OH, 17-19 Sept., 1990.
F.C. Phillips. The Canadair CL-84 Tilt-Wing V/STOL Programme. "The Aeronautical Journal of the Royal Aeronautical Society, Vol. 73, No. 704, August 1969."
Pickler, Ron and Milberry, Larry. Canadair: The First 50 Years. Toronto: CANAV Books, 1995. ISBN 0-921022-07-7.

[edit] Specifications

This aircraft article has not been updated to WikiProject Aircraft's current standards. Please see this page for more details.

Wing Span: 33ft 4in (10.16 m)
Maximum width over propeller tips: 34.66 ft (10.56 m)
Length: (tip of instrumented nose boom to tip of tail prop) 53.62 ft (16.34 m)
Maximum height over propellers during wing tilt: 17ft 1.5in (5.36 m)
Diameter - main propellers: 14.0 ft (4.3 m)
Diameter - tail propeller: 7.1 ft (2.2 m)
Weight empty (equipped, less crew): 9023 lb (4093 kg)
Max T/O Wt (VTOL): 12600 lb (5710 kg)
Max T/O Wt (STOL): 14500 lb (6580 kg)
Max Speed: 321 mph (518 km/h)
Max Range: (with max wing fuel, VTOL, & 10% reserves) 420 miles (680 km)

[edit] Trivia

At the time of the CL-84 project, Canadair was a subsidiary of General Dynamics. Someone at General Dynamics thought it would be neat for all their products to have names starting with "Dyna-", and as the CL-84 was a vertical take-off aircraft, it was christened "Dynavert." This moniker was received at Canadair with a mixture of amusement and chagrin - mostly the latter. The name was never used within the project - the aircraft was always referred to as the "84."

It is interesting that the present day V-22 Osprey VTOL aircraft bears a similar appearance some 30 years later although it utliizes a tilting engine concept.