Graham Warwick/WASHINGTON DC
Business aviation is famously conservative, and buyers of Beech-branded products notoriously so. Not surprisingly, Raytheon's 1995 announcement that it was developing a composite-fuselage business aircraft was greeted with cries of "Not another Starship!"
The unconventional, all-composite Beech Starship was a technical triumph, but a commercial failure. With orders in hand for over 200 aircraft and prototypes meeting the performance guarantees, Raytheon's composite-and-metal Premier I looks set to be both technically and commercially successful.
The Premier I is the first all-new design from Raytheon Aircraft, formed in 1994 by the merger of the Beech and Hawker product lines. "This is not another Starship" has become something of a mantra for the company's marketeers and engineers alike.
The difference between the two aircraft, designed a decade apart, lies as much in the attention Raytheon paid to the market before launching the Premier I as it does in the advances in manufacturing technology since the Starship was developed.
Raytheon talked to more than 100 operators, and worked with an advisory group of more than 20, in defining the Premier I. What they wanted was a mid-size cabin at a light jet price - and in Raytheon's eyes that made a composite fuselage a commercial necessity.
The thin-walled fuselage made possible by composite/honeycomb sandwich construction allowed the cabin diameter to be maximised, while automated fibre-placement technology promised to reduce the manufacturing costs substantially. Mating this lightweight fuselage with a swept, machined-metal wing offered an irresistible combination of high performance and low cost.
With the initial marketing, manufacturing and test results now in, the company believes its instincts have proved correct. Market acceptance of the $4.56 million light jet is strong, prompting Raytheon to increase planned production by 25%, to 60 a year, in response to demand, says Premier I business unit director Duncan Koerbel.
With 18 composite fuselages built so far, cost and quality are tracking projections, he says, and production span time is averaging five to seven days, close to the plan of one fuselage every five days. A second fibre-placement machine will be operational at Raytheon's Wichita, Kansas, plant later this year, to be followed next year by a third such machine.
With over 460h of flight testing, the performance guarantees are being met, Koerbel says. The Premier I is expected to achieve a "best in class" 461kt (853km/h) cruise speed and 2,780km (1,500nm) range. Payload remains on target at 360kg (800lb), with a 68kg contingency for growth during development still unused.
The challenge Raytheon faces is to complete the certification programme on schedule. When it launched the Premier I programme in October 1995, it planned to certificate the aircraft by the end of 1998. Delays pushed the first flight back to December last year, and US certification is now planned for year-end. A fourth aircraft has been added to the flight test programme to help catch up. "The odds are against us to finish this year," Koerbel acknowledges, "but we will by early next year."
In designing the Premier I, Raytheon set out to produce the "undisputed leader" of the entry-level jet class. Subsequently, Cessna has moved to update its CitationJet and Sino Swearingen has repositioned the SJ30-2, but Koerbel believes the Premier I will be the best in its class "for at least five years".
Comfort and performance
This boast is based on the combination of comfort and performance. Cabin width is almost 1.7m (5.5ft), compared with 1.45m for the CitationJet CJ1 and CJ2, and length is matched only by that of the stretched CJ2. The straight-wing CitationJet, even the uprated CJ2, cannot match the swept-wing Premier's performance, Koerbel says. Powered by the same Williams-Rolls FJ44-2 turbofans as the Raytheon aircraft, the CJ2 has a cruise speed of 400kt, a range of 2,460km and a payload of 285kg. "We burn the same fuel per hour and go 60kt faster. Our direct operating costs have got to be lower," he says.
The FJ44-2-powered SJ30-2, meanwhile, has a smaller cabin and payload, similar cruise speed, but longer range (4,350km) than the Premier I. Weight increases have forced Sino Swearingen to move its aircraft up into the commuter certification category, but Koerbel says the Premier I will meet its performance guarantees within the 5,670kg take-off weight limit for Part 23 certification. "This is a full fuel, five-passenger aircraft [at 5,670kg]," he says.
"We are definitely moving CitationJet owners into Premier Is," says Koerbel. At the same time, Raytheon is protecting its Beech King Air customer base by offering them something to move up into. Here, the large cabin, keen price and conservative design are key factors.
The Premier I is intended to be the first in a family of aircraft, the second member of which is likely to be launched in a year's time. As the company has pointed out previously, the fuselage construction method does not restrict it to simply stretching the Premier I. The manufacturing technology is being used already, to produce the much larger fuselage of Raytheon's "super mid-size" Hawker Horizon, scheduled to fly for the first time early next year. The three Cincinnati Milacron Viper fibre-placement machines that will be operational by next year will be used to build fuselages for both aircraft.
The Premier I fuselage is produced in front and aft sections. Carbonfibre tows are rolled on to a mandrel to form the inner skin. Fibre placement is computer-steered to lay down plies at different angles and the machine can stop and start tows to create apertures for the doors and windows. Nomex honeycomb core panels and reinforced door and window frames are hand-placed over the inner skin and the outer carbonfibre laminate is then fibre-placed. The completed fuselage section is placed in a clamshell tool, the mandrel is removed and the structure is cured in an autoclave. The resulting fuselage shell is just 20mm thick, says Koerbel.
Fuselage production time has reduced substantially and quality has improved dramatically as Raytheon has perfected the fibre- placement process. Fuselage sections are inspected automatically using laser shearography and defects detected "have come way down", he says.
Metal internal structure is installed pre-assembled in the fuselage halves before they are bonded together, to ease access. The wing, meanwhile, is all metal and is made largely of machined components, which has reduced the parts count dramatically, says Koerbel. Automatic riveting is used to attach the skins, and all systems are installed and tested before the wing is mated to the fuselage.
Swept for speed
The high-speed wing, which has a quarter-chord sweep of 20°, has 75%-span Fowler flaps to reduce take-off field length to 915m. Hydraulically powered spoilers augment the roll control provided by the small ailerons, and act as speed brakes and lift dumpers. The dual 207bar (3,000lb/in²) hydraulic systems also power the landing gear and brakes.
The vertical stabiliser has a metal substructure and carbonfibre/honeycomb skins, while the horizontal stabiliser is largely composite. To reduce demand for bleed air from the relatively small, 2,300lb-thrust (10.2kN), FJ44-2A turbofans, electromagnetic actuators on the horizontal stabiliser expel ice aft of the electrically heated leading edges.
The engines are controlled digitally by a single-channel electronic fuel control unit with hydromechanical backup. All fuel is stored in the wing. Pressurisation is also controlled digitally, and the maximum pressure differential of 0.5796bar provides an 8,000ft cabin at the maximum operating altitude of 41,000ft.
The Premier I is aimed at the "owner-flown" market, and the aircraft will be certificated for single-pilot operation, but the cockpit is fully equipped for dual control. Rockwell Collins Pro Line 21 integrated avionics are installed as standard, with the baseline cockpit having two large liquid-crystal displays (LCDs) for the pilot. These are a primary flight display and a multifunction display.
Most customers are expected to specify the optional third LCD, Koerbel says, which provides a primary flight display for the co-pilot. "The standard aircraft is pretty good, but the three-tube layout is very popular, as it provides RVSM [reduced vertical separation minimum] capability," he says. RVSM compliance will be required in Europe, where the Premier I is proving popular.
About 40% of aircraft sold so far are to international customers, and talks are under way on gaining European Joint Aviation Authorities approval. Raytheon's focus for now is on winning US Federal Aviation Administration approval and getting deliveries under way.
As well as setting a new standard for entry-level business jets, the Premier I could redefine the light end of the market. "We have a bigger cross-section than the Learjet 45 and it's just 1in smaller than the Citation Excel's," says Koerbel. "It previously took $8-10 million to buy this combination of payload and speed."
Source: Flight International
