Canadair CL-84
Encyclopedia
The Canadair CL-84 "Dynavert", designated by the Canadian Forces
as the CX-131, was a V/STOL
turbine tilt-wing monoplane designed and manufactured by Canadair
between 1964 and 1972. Only four of these experimental aircraft were built with three entering flight testing. Two of the CL-84s crashed due to mechanical failures, but no loss of life occurred as a result of these accidents. Despite the fact that the CL-84 was very successful in the experimental and operational trials carried out between 1972 and 1974, no production contracts resulted.
and VTOL
. The incidence of the tailplane (or stabilizer) was automatically altered to deal with trim changes as the wing-incidence varied. The two sets of blades were locked in a fore and aft position in conventional flight.
At the time of the CL-84 project, Canadair was a subsidiary of General Dynamics
and the parent company christened the new aircraft, the "Dynavert." Canadair project personnel typically referred to it simply as the "84".
Contra-rotating rotors on a vertical axis in the tail provided fore-and-aft (pitch) control during hovering and transitional flight. The propulsion and lifting propellers were handed (i.e. 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 (roll) 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. The flap/ailerons gave yaw control when hovering. In the cockpit fore and aft stick was always pitch, side to side was always roll and the rudder pedals were always yaw, irrespective of the wing position through its full range.
Two 1500 shp Lycoming T53
shaft-turbines were used to drive the two 14 ft (4.3 m) four-bladed propellers. The engines were interconnected by cross shafts, so that in the event of the failure of one engine, it would automatically disconnect (through torque spring clutches) and both propellers would be driven by the remaining engine.
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.
The first newly designed CL-84-1 (CX8401) flew on 19 February 1970 with Bill Longhurst again at the controls. He continued with the CL-84 program until his retirement from active flying in January 1971. Doug Atkins then assumed the role of chief test pilot. At about the same time, at the height of the Vietnam War, the US Navy expressed interest in the concept. Atkins was dispatched on a cross-country tour that took a CL-84-1 to Washington DC (landing on the White House lawn), Norfolk, Virginia
, Edwards Air Force Base
and eventually full-blown trials on the USS Guam
. The CL-84-1 performed flawlessly, demonstrating versatility in a wide range of onboard roles, including troop deployment, radar surveillance and anti-submarine warfare.
The potency of the CL-84-1 as a gun platform was dramatically illustrated in a Canadair promotional film. Fitted with a General Electric
SUU 11A/A pod with a 7.62 mm mini-gun, Adkins maintained a rock-steady position as he sprayed a ground target. The rotating six-barrel “Gatling” gun delivered 3,000 rounds per minute, ripping up the target.
Continuing Tripartite trials by Canadian, US (Navy/Marine) and RAF
evaluation pilots at the US Navy’s Patuxent River Experimental Test Center showed that the CL-84-1 was a suitable multi-mission aircraft. RAF Flight Lieutenant
Ron Ledwidge became the first to make a descending transition from hovering to conventional flight and back to hovering while on instruments.
On 8 August 1973, the first CL-84-1 was lost when a catastrophic failure occurred in the left propeller gearbox in a maximum power climb. The US Navy and US Marine pilots aboard ejected safely. Canadair representatives were sure something was wrong – the entire propeller and supporting structure of the gearbox had broken away during the climb. It was rumoured that the pilots had attempted to set an unauthorized climb record to 10000 ft (3,048 m) to take that distinction away from the F-4 Phantom that had held it. The second CL-84-1 (CX8402) was rushed stateside to complete the Phase 2 trials on board the USS Guadalcanal
. In the face of gale storm conditions, the "84" performed magnificently in tasks such as ferrying troops and “blind-flight.” Phase 3 and 4 trials proceeded immediately after, but, despite rave reviews from over 40 pilots, the CL-84-1 did not land any production contracts.
meant a scaling back on military requirements, but Canadair designer Fred Phillips had been cognizant of other factors gravitating against the "84." The first and most crucial was the “NBH” (not built here) factor; Canada had overcome it with other sales to the US military but the de Havilland Canada Beaver, Otter and Caribou
loomed as exceptions to the rule. It was also "a prop job in the age of jets" and, lastly, the CL-84 "tilt-wing" concept did not have a "grand champion" who would fight for it in boardrooms and military procurement offices. Canadair had tried to sell the Dynavert to others – Germany
, Holland
, Italy
, Scandinavia
and the United Kingdom
were all courted, but, in the end, the Canadair CL-84 project died in 1974 for lack of interest, not even in Canada.
A prototype and three evaluation aircraft had been built. The three CL-84s that flew made a total of over 700 flights and were flown (besides Canadair test pilots) by 36 pilots from Canadian, UK and US civil and military agencies.
The two remaining CL-84s ended up in museums. CX8402 resides in the Canada Aviation Museum
in Ottawa alongside the Avro Arrow, another faded dream of technological greatness in Canada. CX8403 was never flown; it was donated to the Western Canada Aviation Museum
. Shipped as two main sections, fuselage and wings, the last CL-84 has never been restored and only the fuselage and portions of the wing are on display in the main gallery.
Canadian Forces
The Canadian Forces , officially the Canadian Armed Forces , are the unified armed forces of Canada, as constituted by the National Defence Act, which states: "The Canadian Forces are the armed forces of Her Majesty raised by Canada and consist of one Service called the Canadian Armed Forces."...
as the CX-131, was a V/STOL
V/STOL
Vertical and/or short take-off and landing is a term used to describe aircraft that are able to take-off or land vertically or on short runways. Vertical takeoff and landing describes craft which do not require runways at all...
turbine tilt-wing monoplane designed and manufactured by Canadair
Canadair
Canadair Ltd. was a civil and military aircraft manufacturer in Canada. It was a subsidiary of other aircraft manufacturers, then a nationalized corporation until privatized in 1986, and became the core of Bombardier Aerospace....
between 1964 and 1972. Only four of these experimental aircraft were built with three entering flight testing. Two of the CL-84s crashed due to mechanical failures, but no loss of life occurred as a result of these accidents. Despite the fact that the CL-84 was very successful in the experimental and operational trials carried out between 1972 and 1974, no production contracts resulted.
Development
Between 1957 and 1963, Canadair carried out research in VTOL (vertical takeoff and landing) technology with the assistance of the National Research Board (NRB) and the Defense Research Board (DRB) of Canada. The studies pointed the way to a unique tilt-wing design. The wing and the powerplants of the aircraft could be tilted hydro-mechanically (recirculating ball actuator) so that the wing incidence changed through 100 degrees from a normal flight angle to those for STOLSTOL
STOL is an acronym for short take-off and landing, a term used to describe aircraft with very short runway requirements.-Definitions:There is no one accepted definition of STOL and many different definitions have been used by different authorities and nations at various times and for a myriad of...
and VTOL
VTOL
A vertical take-off and landing aircraft is one that can hover, take off and land vertically. This classification includes fixed-wing aircraft as well as helicopters and other aircraft with powered rotors, such as cyclogyros/cyclocopters and tiltrotors...
. The incidence of the tailplane (or stabilizer) was automatically altered to deal with trim changes as the wing-incidence varied. The two sets of blades were locked in a fore and aft position in conventional flight.
At the time of the CL-84 project, Canadair was a subsidiary of General Dynamics
General Dynamics
General Dynamics Corporation is a U.S. defense conglomerate formed by mergers and divestitures, and as of 2008 it is the fifth largest defense contractor in the world. Its headquarters are in West Falls Church , unincorporated Fairfax County, Virginia, in the Falls Church area.The company has...
and the parent company christened the new aircraft, the "Dynavert." Canadair project personnel typically referred to it simply as the "84".
Design
Two 1500 shp Lycoming T53
Lycoming T53
-External links:* *...
shaft-turbines were used to drive the two 14 ft (4.3 m) four-bladed propellers. The engines were interconnected by cross shafts, so that in the event of the failure of one engine, it would automatically disconnect (through torque spring clutches) and both propellers would be driven by the remaining engine.
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.
Testing
CF-VTO-X, the CL-84 prototype first flew in hover on 7 May 1965, flown by Canadair Chief Pilot Bill Longhurst. On 12 September 1967, after 305 relatively uneventful flights, CF-VTO-X was at 3000 ft (914.4 m) when a bearing in the propeller control system failed. Both pilot and observer successfully ejected but the prototype was lost. Canadair redesigned its replacement, the CL-84-1 incorporating over 150 engineering changes including the addition of dual controls, upgraded avionics, an airframe stretch (1.6 m, 5 in 3 in (1.6 m) longer) and more powerful engines (boosted by 100 hp).The first newly designed CL-84-1 (CX8401) flew on 19 February 1970 with Bill Longhurst again at the controls. He continued with the CL-84 program until his retirement from active flying in January 1971. Doug Atkins then assumed the role of chief test pilot. At about the same time, at the height of the Vietnam War, the US Navy expressed interest in the concept. Atkins was dispatched on a cross-country tour that took a CL-84-1 to Washington DC (landing on the White House lawn), Norfolk, Virginia
Norfolk, Virginia
Norfolk is an independent city in the Commonwealth of Virginia in the United States. With a population of 242,803 as of the 2010 Census, it is Virginia's second-largest city behind neighboring Virginia Beach....
, Edwards Air Force Base
Edwards Air Force Base
Edwards Air Force Base is a United States Air Force base located on the border of Kern County, Los Angeles County, and San Bernardino County, California, in the Antelope Valley. It is southwest of the central business district of North Edwards, California and due east of Rosamond.It is named in...
and eventually full-blown trials on the USS Guam
USS Guam (LPH-9)
USS Guam , an Iwo Jima-class amphibious assault ship, was laid down by the Philadelphia Naval Shipyard 15 November 1962; launched 22 August 1964; sponsored by Mrs. Vaughn H. Emory Green; and commissioned 16 January 1965, Captain N. E. Thurmon in command...
. The CL-84-1 performed flawlessly, demonstrating versatility in a wide range of onboard roles, including troop deployment, radar surveillance and anti-submarine warfare.
The potency of the CL-84-1 as a gun platform was dramatically illustrated in a Canadair promotional film. Fitted with a General Electric
General Electric
General Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...
SUU 11A/A pod with a 7.62 mm mini-gun, Adkins maintained a rock-steady position as he sprayed a ground target. The rotating six-barrel “Gatling” gun delivered 3,000 rounds per minute, ripping up the target.
Continuing Tripartite trials by Canadian, US (Navy/Marine) and RAF
Royal Air Force
The Royal Air Force is the aerial warfare service branch of the British Armed Forces. Formed on 1 April 1918, it is the oldest independent air force in the world...
evaluation pilots at the US Navy’s Patuxent River Experimental Test Center showed that the CL-84-1 was a suitable multi-mission aircraft. RAF Flight Lieutenant
Flight Lieutenant
Flight lieutenant is a junior commissioned rank in the Royal Air Force and the air forces of many Commonwealth countries. It ranks above flying officer and immediately below squadron leader. The name of the rank is the complete phrase; it is never shortened to "lieutenant"...
Ron Ledwidge became the first to make a descending transition from hovering to conventional flight and back to hovering while on instruments.
On 8 August 1973, the first CL-84-1 was lost when a catastrophic failure occurred in the left propeller gearbox in a maximum power climb. The US Navy and US Marine pilots aboard ejected safely. Canadair representatives were sure something was wrong – the entire propeller and supporting structure of the gearbox had broken away during the climb. It was rumoured that the pilots had attempted to set an unauthorized climb record to 10000 ft (3,048 m) to take that distinction away from the F-4 Phantom that had held it. The second CL-84-1 (CX8402) was rushed stateside to complete the Phase 2 trials on board the USS Guadalcanal
USS Guadalcanal (LPH-7)
USS Guadalcanal , the third Iwo Jima-class amphibious assault ship , was launched by the Philadelphia Naval Shipyard 16 March 1963, sponsored by Mrs. David Shoup, wife of General Shoup, the former Commandant of the Marine Corps; and commissioned 20 July 1963, Captain Dale K. Peterson in command...
. In the face of gale storm conditions, the "84" performed magnificently in tasks such as ferrying troops and “blind-flight.” Phase 3 and 4 trials proceeded immediately after, but, despite rave reviews from over 40 pilots, the CL-84-1 did not land any production contracts.
Cancellation
The end of the Vietnam WarVietnam War
The Vietnam War was a Cold War-era military conflict that occurred in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. This war followed the First Indochina War and was fought between North Vietnam, supported by its communist allies, and the government of...
meant a scaling back on military requirements, but Canadair designer Fred Phillips had been cognizant of other factors gravitating against the "84." The first and most crucial was the “NBH” (not built here) factor; Canada had overcome it with other sales to the US military but the de Havilland Canada Beaver, Otter and Caribou
De Havilland Canada DHC-4 Caribou
The de Havilland Canada DHC-4 Caribou is a Canadian-designed and produced specialized cargo aircraft with short takeoff and landing capability...
loomed as exceptions to the rule. It was also "a prop job in the age of jets" and, lastly, the CL-84 "tilt-wing" concept did not have a "grand champion" who would fight for it in boardrooms and military procurement offices. Canadair had tried to sell the Dynavert to others – Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
, Holland
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
, Scandinavia
Scandinavia
Scandinavia is a cultural, historical and ethno-linguistic region in northern Europe that includes the three kingdoms of Denmark, Norway and Sweden, characterized by their common ethno-cultural heritage and language. Modern Norway and Sweden proper are situated on the Scandinavian Peninsula,...
and the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
were all courted, but, in the end, the Canadair CL-84 project died in 1974 for lack of interest, not even in Canada.
A prototype and three evaluation aircraft had been built. The three CL-84s that flew made a total of over 700 flights and were flown (besides Canadair test pilots) by 36 pilots from Canadian, UK and US civil and military agencies.
Aircraft on display
Canada Aviation Museum
The Canada Aviation and Space Museum is Canada's national aviation history museum. The museum is located in Ottawa, Ontario, Canada, at the Ottawa/Rockcliffe Airport...
in Ottawa alongside the Avro Arrow, another faded dream of technological greatness in Canada. CX8403 was never flown; it was donated to the Western Canada Aviation Museum
Western Canada Aviation Museum
The Western Canada Aviation Museum is a museum in Winnipeg, Manitoba, Canada. It is the second largest aviation museum in Canada. The collection is housed in an original Trans-Canada Air Lines hangar dating from the 1930s....
. Shipped as two main sections, fuselage and wings, the last CL-84 has never been restored and only the fuselage and portions of the wing are on display in the main gallery.