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Aviation History
1961
1961 - 1290.PDF
392 FLIGHT, 1 September 1961 CANADAIR CL-41 in the Air . . . The CL-41 in the wooded mainten- ance area at Frankfurt airport. Note the clamshell canopy and high- set tailplane normally a button is pressed on the stick to activate hydraulicnosewheel steering after the wheel has been aligned with the steering pawls. Starting is quite automatic and extremely simple, and theengine control makes mishandling impossible. A burst of power started us forward and I engaged nosewheel steeringand coasted down the long taxiway at idling power. Take-off flap was set, stick-top trim button held forward until a lightshowed elevator trim neutral, and tab position showed aileron trim neutral. Fuel contents were 1,5001b. to give this instru-mented prototype a representative production weight. For take-off I pushed the throttle hard forward and keptnosewheel steering engaged. After a pause the engine wound up and pushed us off down the runway. At about 50kt Ireleased nosewheel steering and used the rudder, raised the nosewheel slightly at 70kt and pulled off at 80kt. Under-carriage retraction provided no trim change, the flaps gave a slight sink and we settled to climb at about 190kt and some-thing over 2,000ft/min, homing on Nierstein NDB, near Worms. First impression was of great smoothness, combined with apleasant elevator and very crisp ailerons. Ian MacTavish had achieved an excellent combination of spring-tab lightnesswithout the unpleasant springiness which these controls often have. For fast rolls at above 200kt the ailerons were a trifleheavy for the purist, but probably right for inexperienced pupils. Rudder, when used for deliberate yawing, was heavyand rather soggy. After letting the rudder go suddenly, at low speeds, the resulting oscillation continued for rather a longtime. At speeds above 90kt, fast rolls into steep turns and rapid changes of direction could be made without any use ofrudder, but below 90kt light rudder was necessary to keep the slip ball centred. Elevator forces during 2g steep turnsappeared appropriate and comfortable. I particularly liked the CL-41's combination of crisp manoeuvrability with willingnessto fly hands-off. Elevator trim was sensitive at the 80-per-cent-power cruisingspeed of 220kt at about 6,000ft. but not difficult to set after a little practice. At this speed, the airbrakes produced a firmnose-up trim change, and moderate drag with slight vibration. At lower speeds, particularly during approach, only the nose-uptrim change remained, without any perceptible drag. As already noted, airbrake effectiveness is to be greatly increasedin production aircraft. With the aircraft clean I throttled right back and waited asthe speed slowly reduced at constant height. Below lOOkt the angle of attack increased considerably and a sharp, completelyunmistakable vibration was followed almost immediately by a progressive wing-drop which developed into a spiral dive. Thestick had just reached its back-stop. The stall was full-blown, but not rough, and the CL-41 recovered immediately back- pressure was released. I pulled out into level flight without applying power after losing 500ft. There was no tendency to stall again. In steep turns at about 150kt the stall was announced by the same pronounced vibration and a wing-drop, but recovery was again instantaneous when back-pressure was released. I next slowed down and lowered gear and take-off flap at175kt. Gear caused no trim change, but flap pulled the nose well down and a good pull on the trim button was needed.Full flap, lowered at 140kt, caused further nose-down trim change, but all could be fully cancelled out, power-off, at 95kt.I pulled back to the stall, which came, again with the stick just fully back, at about 70kt. Warning, wing-drop and recoverywere the same. CANADAIR CL-4IA (One Pratt & Whitney JTI2 derated to 2,5701b thrust) Span. 36fc 4in; length, 32ft; usable fuel, 1,9001b; gross weight, 7,2001b; limit load factor, 7.33g to —3.0g. Performance; Maximum sea-level speed, 387kt; max speed at 30,000ft, 421 kt; limit dive speed, SOOkt; limit Mach number, 0.8; stalling speed, 68kt; service ceiling, 44,600ft; sea-level climb, 3,650ft/min; time to 20,000ft, 7.2min: take-off to 50ft, 2,230ft: landing distance from 50ft. 1,570ft. We now headed for Frankfurt with fuel for possibleextended holding. Being cleared straight in we decided on a roller landing, lowered gear, take-off flap and airbrakes down-wind and settled at 125kt. I made a normal curved approach, applied full flap, slowed progressively to 95kt over the hedgeand found no difficulty in wiping the main wheels onto the runway in traditional jet fashion. Holding the nose up 1reduced to take-off flap, closed airbrakes and banged the throttle open. The nosewheel finally settled onto the runwayjust before the whoosh of full power sent us immediately into the air again for a normal take-off without any trim change.With everything out and down, the CL-41 climbs at 500ft/min at HOkt, but ttie angle of climb increases well as things comeup and in. A curved climb put us back onto the downwind leg at 170kt and I went through another touch-and-go circuitbefore making the final landing between a Connie and a Convair. During my limited flight I felt that the CL-41 rudder washeavy and rather weak, but in jet aircraft rudder function is rather specialized. The windscreen arch badly obstructed viewof the runway at the end of a normal curved approach, but the arch thickness will be greatly reduced in production aircraft.More effective airbrakes will assist in steepening the approach, which is a trifle shallow at present. Otherwise the CL-41 wassmooth and easy to fly and should really give pupils very little trouble and no pitfalls. "Flight" photograph ™ Rear view of the CL-41 with air- brakes open during final pre-flight checks after assembly- The Boeing 707 belongs to Lufthansa, whose maintenance base Canadair use
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