GRAHAM WARWICK/WICHITA
The Sovereign is Cessna's "biggest all-new design effort since the Citation X", says programme manager Brad Thress. The company is also endeavouring to obtain an all-new certification in 45 months, compared to over 60 for the Citation X.
Flight testing began in February with US and European Part 25 certification planned for the third quarter of next year, after an 18-month, 2,000h flight test programme involving three aircraft. Customer deliveries are to begin early in 2004.
The mid-size Sovereign was introduced in 1998, along with the CJ1, CJ2 and Encore, but Cessna lacked the engineering manpower to tackle all four programmes simultaneously, so the Sovereign was delayed, finally receiving the go-ahead in January 2000.
Within the Citation line-up, the Model 680 Sovereign takes the place once occupied by the Model 650 Citation III/VI/VII. It is distinctly different and the mildly swept, gently supercritical wing is all new. The 16.3¡ leading-edge sweep increases cruise speed, while the essentially straight trailing edge provides Citation-class short field performance.
As launched, the aircraft bore a strong family resemblance to the existing Citations, but the Sovereign has evolved its own distinctive appearance. The main difference is the tail, which was to have been taken from the straight-wing Citations. But the aircraft has lost the traditional tailplane dihedral and dorsal fin fillet, giving the aircraft a more modern appearance.
The tail is provided by risk-sharing supplier, Fokker. The long tailplane span increases centre of gravity range while the tail fin and rudder reduces minimum control speed. Dihedral was eliminated to increase stability and the fillet removed to increase rudder effectiveness, says Thress. Both wing and horizontal tail have bleed-air anti-icing.
The fuselage is similar to that of the Citation X, and the nose is built on the same tooling. While it has the same cross-section, the improved cabin is slightly longer and the aft lavatory and carry-on baggage compartment are bigger because the Mach 0.78 Sovereign does not require the M0.92 Citation X's aft-fuselage area ruling.
The cabin has other improvements, which may find their way into the Citation X and possibly the Excel. These include fully dimmable LED lighting with a 100,000h design life, software programmable switch panels, and laptop powerpoints and dataports.
The Sovereign is powered by two 5,690lb-thrust (25.3kN) Pratt & Whitney Canada PW306C turbofans, each with dual digital controls. The PW300 series is new to Cessna, but certificated on other business jets. The inlets are acoustically treated for the first time in a Citation, says Thress. Simple single-pivot thrust reversers are standard, as is a Honeywell RE100 auxiliary power unit.
Systems are more complex than in the straight-wing Citations, and include dual electrical buses and dual 207bar (3,000lb/in2) hydraulic systems, which power the landing gear, brakes, nosewheel steering, flaps, spoilers and thrust reversers. The trailing-link main gear has dual wheels and the nose gear is taken from the Citation X, says Thress, with improvements to reduce shimmy.
The cockpit features Honeywell Primus Epic integrated avionics, an advance over the Primus 2000-based cockpit in the Citation X. There are four large liquid-crystal displays and two cursor-control devices (CCDs) on the centre pedestal. The CCDs are used to access drop-down menus on the displays. There are no radio management units: radio tuning is accomplished via the multi-function displays, says Thress.
Performance goals for the Sovereign include a 446kt (826km/h) maximum cruise speed and 5,220km (2,820nm) maximum range. "The aircraft is not truly transcontinental. It cannot fly westbound against headwinds," says Thress. Certificated ceiling will be 47,000ft (14,300m), 2,000ft higher than for the straight-wing Citations but below the Citation X's 51,000ft. Take-off distance will be 1,220m (4,000ft) and landing distance 975m - similar to straight-wing Citation performance - and the Sovereign will be certificated for operations into the UK's London City Airport, as are the Citation CJ1, CJ2 and Bravo.
Cessna has orders for some 125 Sovereigns, including 50 from fractional-ownership firm NetJets. Production should hit 60 by 2006.
Source: Flight International
