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Aviation History
1999
1999 - 1746.PDF
for increased loads. Flap actuation has changed from a flexible shaft-driven system to torque tubes and ball-screw actuators, while the new two-position slats have driven byrack-and-pin- ion drives and rotary actuators. Both flaps and slats are activated by new dual power drive units, which are in turn controlled by two dual-chan nel flap track electronic control units. The evolution of the Challenger series busi ness jet and later the CRJ series regional jets has been paralleled by die incremental development of the General Electric CF34 turbofan. The engine, in its initial 9,0001b-thrust (40kN) CF34-1A commercial guise, first powered the 601-lAin 1983, followed by the improved -3A powered 601-3A in 1987, theCRJ-lOOin 1991 and the -3B/3Bl-powered CRJ-200 in 1998. Bombardier's decision to launch the CRJ- 700 has resulted in the most radical redesign of the engine to date, to generate the required 50% jump in thrust over the CF34-3B1. The newl3,7901b-thrustCF34-8Cl has full author ity digital engine control, an enlarged 1.12m- diameter fan, new wide chord titanium fan olades, a reduced 10-stage high pressure com pressor (HPC), the first three of which are com prised of integral blade/discs (blisks) - and fewer variable guide vane stages. The machined-ring combustor has been designed for a longer burn life and reduced emis sions. The high-pressure turbine module fea tures directionally solidified second stage blades, three-dimensional aerodynamic refinements ind extended-life boltless blade retainers, repli cated in the four-stage low pressure turbine. The net result is a 10% improved thrust-to-weight ratio and a 30% reduction in parts. MEW PYLONS V larger engine has necessitated a new pylon nounring and nacelle housing from Shorts. To iccommodate the 37% heavier engine, the pylons have been enlarged and built to a thicker gauge, incorporating more titanium in place of iluminium. The mounting has also been lesigned to facilitate faster engine change. There is also a new leading edge fairing. Mounted on the pylon are wide-opening lamshell cowlings to the CF34's fan, reverser md core, with a counterbalance operation for one-man operations. The nacelle has been iesigned for right-left commonality to reduce tarts count and spares provisions. "The thrust 'everser has a hydraulic actuator system and no ilocker doors instead of the pneumatic system i m the -200," says Harpin. Changes have been made to the aircraft's -lectrical power system, including fitting three •nore powerful 40kVA generators and new AC power controllers. Anew emergency 8,000rpm :ir driven generator has been installed. The . ^RJ-700 has fitted new external taxi and navi gation lighting, while the passenger cabin has been equipped with self-illuminating floor sghting. An increased demand for power has meant replacing the present AlliedSignal GTCP36- 150 APU with the AlliedSignal RE-220. The new APU is housed in a 25% larger tailcone produced by GKN Westland Aerospace. The APU is mounted in its own cradle and can be accessed from below via clamshell doors for removal using fishpole hoists. The new APU is large enough to drive a 40kVA generator and can be operated through out the CRJ-700's flight envelope up to a maxi mum altitude of 41,000ft. It can be started at 37,000ft and can assist a main engine start at 2 5,000ft. "What drove the selection of the APU was the requirement ofAmerican Airlines to pull down the cabin temperature within 30min to 2 7°C on a 40°C day," says Erlandson. A new Liebherr environmental control system (ECS) automatically switches • Assembly of the CRJ- 100 takes place under the same roof as the CRJ-200 and Challenger at Dorval Relocation of the -100's more powerful AlliedSignal APU has required the tailcone to be enlarged 25% LIGHT INTERNATIONAL 9 - 15 June 1999 159
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