Graham Warwick/WASHINGTON DC
The engine that launched the regional jet age is powering the next phase of the RJ revolution. Already the leading powerplant in the 50-seat jet market, General Electric's CF34 is to power all major contenders in the 70- and 90-seat markets.
While the CF34-3 powers the 50-seat Bombardier CRJ100/200, the uprated -8 is under development for the stretched 70-seat CRJ700 and 90-seat CRJ900. The CF34-8 will also power the 70-seat Embraer ERJ-170 and Fairchild Dornier 728JET, while the -10 growth derivative has been selected for the 90-seat ERJ-190 and 928JET.
Covering a thrust range from 8,750lb to 18,500lb (38.9-82.3kN) is no mean feat for an engine, but in the CF34's case it involves stretching the definition of a derivative. "The CF34-10 is a new centreline engine," admits Frank Klaus, general manager of GE's small commercial engines operation. "But, from a customer's viewpoint, the accessories are the same as the -8. They are in the same place, for quick removal and replacement."
The CF34-8 is, itself, substantially different from the baseline -3. Thrust is increased by 50%, to 14,000lb, and parts count is reduced by 30% - largely due to the use of a high-pressure (HP) compressor derived from that in GE's F414 fighter engine, with 10 stages instead of the -3's 14. Specific fuel consumption, noise and emissions are all reduced from -3 levels. The -8 also introduces full-authority digital engine control (FADEC) to the CF34.
The -8 programme is on track, says Klaus. The -8C1 for the CRJ700 was certificated in November last year and Bombardier has selected the 5%-uprated -8C5 to power the yet-to-be-launched CRJ900. Ground testing of the -8C5 has begun and certification is planned for the second quarter of 2002. "It's a very aggressive schedule," says Klaus.
The first wing-mounted versions of the CF34 - the -8D for the 728JET and the -8E for the ERJ-170 - are also progressing. Ground testing of both versions begins in the third quarter. The -8E is uprated by 5% from the -8D, which shares the turbomachinery, accessories and FADEC of the -8C. The major difference is the nacelle: the wing-mounted unit for the -8D/E is produced by Aermacchi and Hurel-Dubois, while the fuselage-mounted nacelle for the -8C is produced by Bombardier's Shorts.
GE is introducing its "chevron" nozzle on the -8D/E and is speaking to Bombardier about fitting the noise-reducing device on the -8C. The companies are also talking about standardising on the -8C5 for both the CRJ700 and CRJ900. The -8C5 uses the uprated turbomachinery of the -8E, and would be derated to power the 70-seat CRJ700, offering maintenance benefits.
Selection of the -8C5 to power the CRJ900 gets the engine into the 90-seat regional jet market, but the CF34-10 represents a "dramatic move forward", says Klaus. The need for 30% more growth in thrust, to 18,500lb with the potential for 20,000lb, has resulted in an essentially new engine which follows the CF34 philosophy of using proven, derivative technology.
GE has completed conceptual design of the -10 and will begin detail design by mid-year. Klaus says two main drivers guided the initial design: the need for a core large enough to provide the take-off thrust margins that will be required to meet increased range and payload targets, and the desire to assure low-risk, low-cost development.
The resulting design draws on technology from a range of GE engines: from the CF6, the retention system for the wide-chord fan blades and the composite swept and "leaned" fan outlet guide vanes; from the CFM56, the three-dimensional HP compressor aerodyamics, single annular combustor and single-stage HP turbine; and from the CF34-8, the four-stage HP turbine and FADEC.
The first engine to test is planned for the first quarter of 2002 and the -10 is set to fly on GE's Boeing 747 engine testbed in mid-2002. Certification is set for early 2003. The first aircraft to be powered by the -10 will be Embraer's 110-seat ERJ-190-200.
GE, meanwhile, is not neglecting the CF34-3. Durability and repairability improvements will be introduced into production engines in the third quarter, with upgrade kits for in-service engines available in the fourth quarter. These are expected to increase time "on wing" by 30%, says Klaus, and will keep the CF34 at the front of the regional jet revolution.
Source: Flight International
