FLIGHT TESTING OF the VisionAire Vantage single-engined business jet is demonstrating the high- and low-speed performance necessary for the aircraft to be competitive and safe, says its developer. VisionAire says that the proof-of-concept (PoC) aircraft, built and flown by Burt Rutan's Scaled Composites, is achieving cruise speeds equivalent to other entry-level business jets and stall speeds comparable with high-performance piston singles. Proving that the single-turbofan Vantage can provide the performance and safety expected of a business jet is central to the fledgling firm's plan to become an aircraft manufacturer, but VisionAire does not intend to stay a single-product company, says president Tom Stark. Work has already begun on a small, single-turbofan two-seater, he reveals.
VisionAire did not set out to build a single-engined business jet - it set out to fill the market niche it had identified for a low-cost, entry-level business jet.
Company founder Jim Rice saw a demand for an aircraft appealing to smaller businesses that could not justify the expense of a corporate jet costing upwards of $3 million.
The resulting Vantage, at $1.65 million, is priced to fill the gap between high-performance piston-singles, such as the Piper Malibu Mirage at $700,000, and existing entry-level business jets, such as the Cessna CitationJet at $3.3 million. "The Vantage is the 21st-century update of the cabin-class piston twin, with better speed, economy and operating cost," says marketing director Mark Jones.
The initial, 59-aircraft orderbook seems to support VisionAire's market research. Almost half the customers now operate piston-powered aircraft, while 20% do not presently own an aircraft. Two-thirds of the companies buying the aircraft have annual revenues of less than $25 million, but 12% exceed $100 million. Sales are divided almost equally between the owner-flown market and operators with a company pilot or flight department, says vice-president, strategic planning, Jorge Perez.
Piston twins were delivered in large numbers in the 1960s and 1970s, and there is growing demand for a replacement aircraft, Jones believes. It is market targeted, with little success, by Aerospatiale with its single-turboprop TBM700. Jones argues that Aerospatiale "missed the price point", pricing the TBM700, at around $2 million, close to competing twin-turboprops and offering a "modest" operating-cost improvement for a "substantial" reduction in comfort.
"The Vantage has the same price point as old piston twins," says Jones. "Twins cost $300,000 a year to operate, while the Vantage operates at $450-500,000 a year," he says, adding: "The Vantage price/performance point represents significant value-added to the customer compared with a single-engined turboprop."
Overcoming perceptions about the safety of single-engined aircraft is VisionAire's greatest challenge. The company retained safety consultant Robert Breiling to analyse accident data, and he concluded that a single-turbofan aircraft will be more reliable than single or twin piston-powered aircraft, more reliable than single-turboprop aircraft and at least as reliable as a twin-turboprop aircraft.
Breiling's analysis, based on US National Transportation Safety Board and Federal Aviation Administration data, shows that turbine-powered aircraft are safer than piston-powered aircraft, and that turbofans are more reliable than turboprops. Some extrapolation is required, as data on single-jet types are limited to homebuilt and ex-military aircraft, but Breiling is able to point to power-loss accident data which show the single-turboprop Cessna Caravan to be seven times safer than the Malibu piston-single, and commercial-airline shutdown rates which show turbofans to be 12 times more reliable than turboprops.
VisionAire marketing advisor Jim Taylor says that training is the key to establishing a safe record for the Vantage. "The pilot has to get a type rating," he says. The purchase price includes training for one pilot and one maintainer. VisionAire has received proposals to provide training from FlightSafety International, SimuFlite Training International and SimCom. Taylor says that it will take time to establish the Vantage with major corporations, but he sees Fortune 500 companies using the aircraft to diversify their fleets, using the Vantage to move lower management while still flying the CEO in a bigger aircraft. "The aircraft has to prove itself first," he says.
Safety has been a driver in design of the Vantage. Stall speed is the main issue. The FAA requires a stall speed of 61kt (113km/h) for single-engine aircraft, but will allow a higher speed if energy-absorbing seats are fitted. The stall speed, and therefore the gross weight and range, is determined by the g capability of the seats, Stark explains. VisionAire is aiming for a stall speed of 70kt, which requires 21g seats. Such seats do not yet exist, he says, so requests for proposals have been issued to seat developers.
A 70kt stall speed will allow a maximum gross-weight of 3,400kg and a range of some 1,700km (900nm) with full, 560kg payload and 750kg fuel. WIng fuel capacity has been measured at 1,300kg, Stark says, which will give operators the option of offloading payload to fly further. Stall performance of the PoC aircraft is "as predicted, or better", and Rutan believes wing efficiency can be improved to increase weight by 135kg and range by 460km.
Performance guarantees
The PoC aircraft was first flown in November 1996. "The aircraft has remarkably good flying qualities," says Rutan. VisionAire has been "very conservative" on its performance guarantees, he says, promising a 350kt cruise "-when the aircraft will perform at least 390kt, That's good performance with a large cabin and a single engine". The forward-swept wing has "excellent" stall characteristics, Rutan says. "The roots stall first, with no tendency to drop a wing,even in an aggressive stall."
The horizontal tail has been increased in span by 0.6m on each side, to increase centre-of-gravity range and the rear fuselage will be reprofiled slightly on the production aircraft, Rutan says. The inlets for the Pratt & Whitney Canada JT15D-5 turbofan appear to work well. Stark says tests at 30,000ft (9,100m), with full yaw in both directions, stalls and throttle slams have given no indications of any problems.
Drag is close to predictions, he says. The Vantage is designed to have a glide ratio of 16:1, allowing the aircraft to glide for 110km. "It's a very slick aircraft," Stark says, and VisionAire is looking at using the main-gear doors as airbrakes. PoC tests have shown that idle thrust is low enough that the aircraft can be taxied without excessive use of brakes, avoiding the extra weight of a thrust attenuator.
Scaled is responsible for certification of the Vantage's all-composite structure, and will make production airframes at its new Scaled Technology Works plant being set up in Montrose, Colorado. The Vantage will be built using low-cost production methods developed by Scaled and used on the PoC aircraft. The fuselage is laid up on a Styrofoam mandrel - machined for the PoC aircraft, but cast for production Vantages - and the composite stiffening grid, ring frames, longerons, door and window frames and other details are laid into grooves in the mandrel. The skin is then fibre-placed on to the mandrel - manually in the case of the PoC aircraft - and the completed structure is placed in a female tool for co-curing.
Rutan says that this method avoids the use of expensive pre-impregnated composite plies and Nomex honeycomb core. By constructing the aircraft from basic fibre and resin, Rutan hopes to be able to build the Vantage with a material cost closer to $40/kg, compared with $110-175/kg for pre-preg composites. The cost goals for the structure "-are very difficult, but I think they are achievable," he says.
VisionAire is also trying to bring down the cost of the interior, and has requests for proposals out to several suppliers. "We have established cost goals for the interior and we expect to come in substantially below current price levels," says Jones. The Vantage full-scale cabin mock-up, produced by Rutan and outfitted by design consultant Benn Isaacman, is being updated to make the cockpit and cabin roomier. A revised instrument panel with AlliedSignal Bendix/King avionics will be installed.
Flight-test aircraft
Two certification flight-test aircraft are planned, to be built by Scaled and flown from VisionAire's plant at Spirit of St Louis Airport. The first flight is planned for April 1998, leading to certification and first deliveries in April 1999. VisionAire is privately funded. The company has so far raised $15 million by selling equity, raising debt and securing inducements from Ames, Iowa, where the final-assembly plant is to be located. VisionAire is now raising $34 million via a private placement to take the programme through to first delivery, and chief financial officer Gary Pluth hopes to have the funding signed up by mid-year. The intention is to take the company public by the end of 2000.
Local and state governments provided $3 million in cash and incentives to bring the Vantage plant to Ames. VisionAire is in final negotiations with local investors who will fund construction the $4 million factory, then lease it to the company. The plant will have the capacity to assemble and flight-test 115 aircraft a year. Cellular manufacturing will be used, with six-person teams building the complete aircraft.
With Scaled's parent company Wyman-Gordon having committed to building the Montrose plant as its investment in the Vantage programme, VisionAire has already attracted strong backing. Perez believes the company's success so far has been because "...we are building a business, not going out to investors with the idea of an aircraft. We are going out with a blueprint for a business."
Source: Flight International
