Graham Warwick/WICHITA
RAYTHEON AIRCRAFT HAS difficulty defining exactly what has made the Hawker family the most successful series of mid-sized business jets. "Balanced", "robust", "honest", "consistent" are words the company uses in trying to encapsulate the qualities that have made the aircraft best sellers. Until now, "advanced" has not been an attribute associated with Hawkers.
Raytheon has decided to distil those Hawker characteristics into a next-generation aircraft, while tackling that aspect of the marque most often criticised: that Hawkers are "old technology". The result is the Hawker Horizon, an all-new, "super mid-size" business jet which was unveiled on 19 November at the US National Business Aircraft Association convention. It was there that the company began taking orders for the $14.5 million Hawker Horizon. The first flight is scheduled for late 1999, leading to certification and first deliveries in the second quarter of 2001.
Work on the next-generation Hawker began soon after Raytheon acquired British Aerospace Corporate Jets, as well as design rights to its 125 series, in 1993. The company decided to phase out production of the Hawker 1000, while upgrading the Hawker 800 and shifting assembly from the UK to Wichita, Kansas, in the USA. "The 800 and 1000 were too close together," says Raytheon Aircraft president Roy Norris. "The 1000 was better in range, but not in cabin or speed."
Preliminary design
When Raytheon Corporate Jets merged with Beech Aircraft in early 1995, the new Hawker, codenamed PD 376, was one of three projects in preliminary design. Seeing an opportunity in the light business-jet market, the company first launched the Premier I, later in 1995, but continued to work on the PD 376. The company's new philosophy is to respond rapidly when it sees an opportunity in the market - "-to be first with the most", says Norris. Raytheon did this when it launched the Premier I, setting a new standard for cabin size and performance in a $3.9 million entry-level business jet (Flight International, 4 October, 1995, P42-43).
Now the company sees an opportunity in the emerging super mid-size market, which it believes is not being adequately served. Of the current contenders, Norris says: "The [Dassault] Falcon 2000 is too expensive, the [Cessna] Citation X is too small and the [Israel Aircraft Industries] Galaxy is not there yet."
The Falcon 2000 inaugurated the market, but has moved up in price to $18.5 million - "-not what we define as super mid-size", says Norris. The Citation X, meanwhile, "-is very fast, but it is difficult to call the cabin super mid-size", he says. As for the Galaxy, Raytheon believes that it will be some time before the aircraft becomes a factor in the market.
The aircraft is neither as large as a Falcon 2000, nor as fast as a Citation X, but it is substantially larger and faster than the Hawker 1000 and costs only $1.5 million more than the aircraft it replaces.
FILLING THE GAP
Norris says that the Horizon is being launched into "-the enormous gap that has been created" between the $11 million Hawker 800XP and the $20 million Canadair Challenger.
Potential customers were allowed unprecedented involvement in the design of the Horizon, including the selection of engine and equipment suppliers. As a result, says Norris, "-the aircraft has changed a lot since its launch". After exhaustive market studies, an advisory council was formed and shown three preliminary designs. One-third of the council members have never operated either a Hawker or a Beech product, he says.
The result was "tight agreement" on one design which embodied the best features of the three options. This became the Model 4000, now christened the Hawker Horizon. The major change demanded by the advisory council was the move from the Hawker 1000's 1.83m-diameter fuselage to one with a 2.13m diameter, to provide a stand-up cabin with a flat floor throughout.
It was important to Raytheon that the aircraft had the characteristics which have made the Hawker marque successful. "We wanted it to be a Hawker," says Norris. To that end, the company brought in experienced Hawker engineers to form the core of the design team. By the end of 1996, some 150 people will have accepted Raytheon's offer to transfer to the USA. "We bought the Hawker genes," he jokes.
Despite being an all-new design - "-only the control yokes are carried over", Norris says - the Horizon has a distinct, and deliberate, Hawker family resemblance. The "not quite a T" tail, dorsal and belly fairings and nose shape are strong visual reminders of the Hawker 1000.
The Hawker heritage is more than skin-deep, as Raytheon has allowed the Horizon team freedom to make the same design trade-offs that resulted in the balanced performance, consistent handling and rugged reliability which have endeared the marque to its operators. "Hawkers were successful because the design decisions were right. We use the same sense of values, the same strategy of balance [in designing the Horizon]," says Norris.
Typical of that balance is the Horizon's range capability: 6,100km (3,300nm) at the Mach 0.8 normal cruise speed, and only 370km less at Mach 0.82. "You don't have to back off speed to get range," says Norris, noting that a US-based operator will be able to fly coast-to-coast, either way, or reach Europe "comfortably".
Despite being substantially larger than the Hawker 1000, and flying further, faster, the Horizon has significantly improved airfield performance, according to Model 4000 project manager Sam Bruner.
Balanced field length is 1,600m (5,250ft), and range from a 1,200m runway is still around 3,500km. The 715m landing distance enables the aircraft to be flown into London City Airport, notes Malcolm Bowd, Hawker project engineer and one of the key people Raytheon brought over from the UK.
With a 16,300kg maximum take-off weight, the Horizon is almost 2,300kg heavier than the Hawker 1000, the fuselage 3.56m longer, and the wingspan 3.25m greater. The fuselage is all-composite, produced using the automated fibre-placement technology developed by Raytheon for the Premier I. Compared with a conventional fuselage, this provides 200mm more cabin width and dramatically reduces production costs.
The fuselage will be produced in three sections: nose, centre barrel and tailcone, including dorsal fairing and engine pylons. The 25mm-thick carbonfibre/honeycomb shell encloses a cabin 2m wide and 1.83m high (compared with 1.75m for the Hawker 1000, which has a dropped aisle). The wing passes entirely under the fuselage.
The wing is described as "third-generation supercritical", offering a good blend of high-speed and low-speed performance. Compared with the Hawker 800/1000 wing, sweep is increased to give a Mach 0.84 maximum cruise capability. There are no leading-edge, high-lift devices, and the flaps have the fixed vanes typical of earlier Hawkers. This "simple, cost- effective", design enables the Hawker's flaps to be single-slotted for take-off and double-slotted for landing, says Bowd.
International partners
Fuji Heavy Industries of Japan will design and produce the wing as a risk-sharing partner. Existing Hawker wing-builder British Aerospace put in a bid for the work, as did Northrop Grumman, but, says Norris, Fuji's proposal was the best technically and the lowest priced. The wing will be metal, with trade studies continuing into composite control-surfaces.
All fuel (6,350kg) is housed in the wing, and the supercritical aerofoils have been carefully designed to minimise aft loading and allow the use of manual ailerons. The wing was designed using computational fluid-dynamics (CFD), as was the aft fuselage, which is area-ruled to minimise drag caused by the engine nacelles. CFD was also used to re-profile the original Hawker 1000 nose to reduce drag at the higher cruise speed.
The tail is conventional aluminium, with studies under way into a composite rudder and horizontal stabiliser. Compared with that of the Hawker 1000, the stabiliser is larger and more swept, and, like the wing, is de-iced using engine bleed-air, replacing the fluid system used on earlier Hawkers. The "over fin" which gives the tail its "Hawker" look will house the antenna for the optional satellite-communications system.
Engine choice
Raytheon evaluated three engines - the Allison AE3007, AlliedSignal/General Electric CFE738 and Pratt & Whitney Canada PW308 - focusing on reliability, time between overhauls (TBO), fuel efficiency and thrust growth for later versions of the aircraft. The winning PW308A provides 29.3kN (6,575lb) of take-off thrust, flat-rated to ISA+22¹C, and 15% growth within the nacelle's external lines.
As a risk-sharing partner, P&WC is responsible for the complete powerplant, including the Nordam-supplied nacelle and thrust reverser. The Canadian company has guaranteed a 6,000h TBO at entry into service, to be demonstrated by a "lead-the-fleet" engine at P&WC.
The digitally controlled PW308A is scaled up from the PW305B powering the Hawker 1000, with an 840mm-diameter, wide-chord fan and an increased-flow compressor. Thermodynamic thrust-to-weight ratio is increased by 8% over that of the PW305B, with specific fuel-consumption improved by 7%.
Honeywell is the risk-sharing avionics integrator, supplying its latest Primus Epic system and integrating equipment supplied by Allied Signal and other vendors before delivery to Raytheon. "We'll simply plug a panel in," says Norris. The Primus Epic avionics suite includes five large-format (200x250mm) liquid-crystal displays - two primary-flight and two multi-function displays and an engine-indication and crew-alerting system. Compared with the Honeywell SPZ-8000 avionics in the Hawker 1000, the Horizon system is at least 45kg lighter, has 23 fewer line-replaceable units and has at least twice the reliability. Avionics are located in the "benign environment" of a rack in the cabin, Raytheon says. Growth plans include display formats such as maps, charts and ground-based weather.
Flight controls are manual, with a powered rudder and electrically signalled spoilers and flaps. The electrical system uses variable-frequency generators on the engines and flight-rated auxiliary power-unit (mounted in the tailcone). The redundancy required for extended-range twinjet operations was a consideration in systems design, says Bruner.
Cabin layout
A typical cabin layout would include eight seats and an aft toilet with in-flight access to the 3.1m3 baggage bay through a secondary pressure-bulkhead. Compared with the Hawker 1000, the forward entry door has been enlarged and the baggage-bay external access improved. Digitally controlled pressurisation provides provides a 6,000ft cabin altitude at the 45,000ft ceiling. Direct climb to 41,000ft is the design objective, Raytheon says.
The Hawker Horizon "-will go fast, go a long way and carry a lot of stuff", says Bruner. "This aircraft will fly half way across the USA with a full 3,500lb payload." This "excellent" balance of speed, range and payload was one of the Hawker characteristics that Raytheon sought to recreate in the Horizon.
"We have taken the best of British design and combined it with the US way of making aircraft, and come up with something truly unique," Norris believes.
Source: Flight International
