Graham Warwick/WITCHITA
Raytheon may be one of the largest producers of turbine-powered business aircraft, but it has yet to design, develop and deliver a corporate jet carrying the Raytheon Aircraft name.
That will change within a year, when the company begins deliveries of the Premier I entry-level business jet - the first all-new design from Raytheon Aircraft since it was formed in 1994 by the merger of Beech Aircraft and Raytheon Corporate Jets.
Within three years, Raytheon will begin deliveries of the Hawker Horizon "super mid-size" business jet, its second all-new design. Both aircraft arguably are the most advanced corporate jets in development, and each is expected to form the basis of a family as Raytheon expands its presence in the business jet market.
All this design activity - Raytheon is simultaneously developing the T-6ATexan II turboprop trainer for the US Air Force/Navy Joint Primary Aircraft Training System - marks a significant change for the Wichita, Kansas-based company. Raytheon is better known for being successful with other companies' designs - turning Mitsubishi's Diamond into the Beechjet and transferring assembly of British Aerospace's Hawker 800 to the USA.
The change followed the creation of Raytheon Aircraft, and the bringing together of the Beech and Hawker product lines. Raytheon, which had owned Beech since 1980, acquired the Hawker line from BAe in 1993 and moved quickly to create a single aircraft company with a wide range of products, from the Bonanza piston single to the mid-size Hawker 800.
At the time of Raytheon Aircraft's creation, the company's last all-new design had been the technically triumphant, but commercially unsuccessful, Beech Starship. The company is understandably sensitive about any negative comparisons between its latest ventures and the Starship, but the commercial failure of this radical, all-composite twin-turboprop taught Raytheon a couple of important lessons.
First, it proved that the customers who have the made the Beech King Air twin-turboprop line a long-term success are conservative, and unwilling to embrace radical ideas. As a result, the conventionally configured Premier I "-is the most customer-oriented aircraft Raytheon has ever built," says vice-president, sales and marketing, Karl Childs.
Secondly, the Starship experience proved that new technology should be used only where it is cost-effective. Both the Premier and Horizon have all-composite fuselages, but the manufacturing technology employed is not that used to produce the Starship, and "...allows us to meet previously unattainable weight, performance and cost goals," says Premier programme director Duncan Koerbel.
LESSONS APPLIED
Soon after its creation, Raytheon set about applying those lessons, launching the Premier I at the 1995 National Business Aviation Association (NBAA) convention and then, a year later, the Hawker Horizon. The Premier is designed to compete against Cessna's entry-level CitationJet, offering a larger cabin and higher performance at a comparable price. The Horizon, meanwhile, is Raytheon's competitor in the new "super mid-size" niche, offering large-aircraft comfort and performance at an aggressive price.
Developing three aircraft (including the T-6) simultaneously has proved a challenge to Raytheon. The Premier programme has slipped, a result of design changes and parts delays, but the Horizon programme has benefited from the experience and both performance and schedule are unchanged, says programme director Tom Reichenberger.
The first Premier I was rolled out on 19 August, and Raytheon hopes to fly the aircraft before the NBAA convention opens on 19 October. The programme establishes several firsts, says Childs: it is Raytheon's first "clean-sheet" jet; it is the first aircraft with a composite fibre-placed fuselage; and it is the first of a family - Raytheon Aircraft chairman Art Wegner says the company should be ready to launch the first derivative within a year.
Despite the delays, slippage in certification and first deliveries has been minimised by adding a fourth aircraft to the flight test programme. Certification is still set for "summer 1999", but the schedule shows this has slipped to the middle of the third quarter. Certification will, however, include all planned options, Koerbel says. "There will be no post-certification work required," he says.
All four flight test aircraft are scheduled to be flying by the end of the year, and all four will be fully configured for certification. The 12-month test programme will involve 1,400h of flying. "It will be a seven-days-a-week effort," admits Koerbel.
With one aircraft completed and the next three in the final stages of assembly, "-weight is on target and we are happy with what it cost to build the aircraft", Koerbel says. Reduced manufacturing cost was a key reason for adopting the composite fibre-placed fuselage. The other was the increase in cabin diameter made possible by using a carbonfibre/honeycomb-sandwich skin structure instead of conventional sheet-metal/frame fuselage construction.
IMPOSSIBLE ACHIEVED
"We could not do the Premier I with the same internal volume and stay within [the weight limits] for Part 23 certification," says Koerbel. "With aluminium, we would need a 13% bigger fuselage for the same volume." Weight is reduced by 20% and cost by about 10% over an aluminium fuselage.
The fuselage is produced in two sections by direct placement of carbonfibre tows on to a mandrel. The inner skin plies are fibre-placed automatically, Nomex honeycomb core is then positioned manually and the outer carbonfibre skin fibre-placed. Cutouts for windows and doors are created automatically by stopping and starting the tows.
The metal mandrel is then removed and the fuselage section enclosed in a clamshell mould for curing in an autoclave. The company's goal is to produce one fuselage every five days, using a double-headed fibre-placement machine at its Wichita plant. A second, similar machine is to be installed alongside the produce the three sections that will make up the Horizon fuselage.
Cured fuselage sections are inspected for defects using laser shearography. Raytheon says defects, such as voids and delaminations, have reduced dramatically as it has gained experience with the fibre-placement process. This is evident on a walk down the assembly line. The first fuselage sections show several patches where skin and core have been replaced, but later examples are essentially clean.
Raytheon plans to build 50 Premier Is a year, but the assembly line is short. Internal fuselage structure (metal) is preassembled and installed into the fuselage sections before they are joined. High-value items such as engines, avionics and landing gear are installed late in final assembly to minimise inventory costs.
The wing is metal and mostly machined. "There are only 180 parts in the primary structure," says Koerbel. (Overall parts count is reduced from 13,000 to 6,000). Raytheon plans to move to machine drilling and rivetting of the wing to reduce costs further. The wing is already fully equipped and tested when it is mated to the fuselage. Mating for the first wing took just 30min, Koerbel says.
The ease of assembly is attributed to the fact that the entire aircraft has been modelled and digitally pre-assembled using the CATIA computer-aided design system. "You do not save upfront engineering effort," says Wegner. "You save in parts fitting together."
SHARING RISK
This experience is reading across the Horizon programme, although it differs substantially in scale and scope. The Horizon is Raytheon's first programme to involve risk-sharing partners as a way of spreading the development cost and risk.
Major partners are Japan's Fuji Heavy Industries, supplying the wing; Pratt & Whitney Canada (PW308A engine); Honeywell (avionics); Messier-Dowty (landing gear); Sundstrand (utility system); Smiths Industries (fuel system); Vickers (hydraulic system); and AlliedSignal (environmental control system and auxiliary power unit).
Following the Premier's example, the Horizon has a composite fibre-placed fuselage and all-metal wing. The empennage is a hybrid, with aluminium substructure and carbonfibre skins and metal-bond rudder and elevators.
The fuselage will be produced in three sections, mechanically joined at two metal hoop frames which carry the wing loads. This makes the design "easy to stretch", Reichenberger notes. The sections will be "stuffed" separately, then joined. Other similarities with the Premier include the machined wing construction. Fuji is expected to supply fully equipped and tested wings ready for mating.
Raytheon is scheduled to complete fibre placement of the first Horizon fuselage sections this month. Fuji is to ship the first wing in December. Joining of the fuselage sections, and mating for the wing and fuselage is set for the second quarter on next year. Roll-out is set for the third quarter and first flight for December 1999. Certification and first deliveries are planned for the second quarter of 2001.
Because of the Horizon's sophistication, Raytheon is building an integrated systems development facility at its plant in Wichita. This will allow the aircraft systems and their integration to be tested thoroughly before first flight. "The utility system is a challenge, as it is new to us," says Reichenberger.
The Horizon programme is benefiting from the experience of the Premier team, admits Reichenberger. "The Premier team is developing the systems as they develop the aircraft - like laying the track while driving the train. What they have done is now available to the Horizon team. It's another reason not to be late."
Raytheon's investment in the development of new business aircraft is unlikely to end with these two aircraft. A Premier derivative is already on the cards for next year and the company continues to look at the market for piston and turboprop aircraft.
Asked why the company has not replaced the long-running Bonanza, Baron and King Air lines, Wegner has answered: "We will when we can build a better aircraft." As the company's experience with the Starship showed, "...the trouble with turboprops is building one as good as a King Air," he says. So, for the foreseeable future, it appears that Raytheon will focus its engineering resources on developing business jets. Will the company go back to buying other manufacturers' design? Asked if Raytheon was interested in buying Gulfstream (a long-running rumour), Wegner answers, flatly: "No."
Source: Flight International