SPn prototype to complete envelope expansion soon

 - October 24, 2006, 10:08 AM

The flight-test program of the Grob Aerospace G180 SPn Utility Jet is progressing well, officials at the German manufacturer said last month at a briefing at the Grob headquarters near Munich. Attendees could also see the prototype fly. The SPn was unveiled at the Paris Air Show this summer.

JAA certification is scheduled for the first quarter of 2007, with deliveries of the $7.1 million light business jet to follow in the second quarter. The SPn utility jet–a collaborative program between Grob and charter operator ExecuJet–is optimized for operations from short, unprepared runways.

The company remains tight-lipped about the number of orders it has received but estimates that the program will produce 400 aircraft in the next 10 years. Grob expects an initial production rate of 15 aircraft per year, and about 40 per year later.

Between its maiden flight on July 20 and September 7, the prototype had flown 23 hours during some 24 sorties. The all-composite aircraft was flown at its predicted stall speed, “which indicates that we still have margin,” test pilot Gérard Guillaumaud told AIN. In addition, engine-out control was said to be “satisfactory” at 1.1 Vs. So far the prototype has reached a maximum of 230 knots, 30 knots below Vmo. The aircraft has also reached 24,000 feet, and Grob expects now to venture up to 41,000 feet.

Guillaumaud insisted he would have “very few stories to tell his grandchildren” about the SPn, recalling the first flight occurred after only two high-speed ground runs instead of the six planned. “This gives you an idea of the level of confidence we have in this airplane,” he said. Similarly, the first series of flights was made from a longer runway in Allgäu. “But only 14 days after the maiden flight we landed here on the 2,360-foot strip,” Guillaumaud said.

The prototype was fitted with basic VFR instruments. IFR equipment will be installed this month, flight-test engineer Alan Lawless told AIN. Nevertheless, the flight deck will not conform to the production standard, the Honeywell Apex avionics suite.

Among the upcoming tests are full-stall and flutter-free demonstrations. The company is waiting for a special parachute for each of these evaluations. The company will also assess the aircraft’s stability and control. Flight envelope testing should be completed before year-end.

Lawless and Guillaumaud, both 44, met at the National Test Pilot School in Mojave, Calif., where Lawless was an instructor. Guillaumaud is a former French Air Force pilot. Before joining Grob Aerospace, Guillaumaud was working with Diamond Aircraft.

Prototype number two, which will be dedicated to system development and certification, is scheduled to make its first flight in March.

The static load airframe completed static tests in February. “We elected to schedule them before the first flight to avoid the weight problems that can emerge during the flight-test phase otherwise,” said Niall Olver, CEO of ExecuJet, which will handle worldwide distribution and support of the utility jet. He added that static tests have shown the airframe has so much margin between certification-required loads and break-up that EASA certification people have allowed Grob to use the same airframe for fatigue testing, a phase that will start in the second quarter of next year.

According to Grob Aerospace COO Andreas Strohmayer, the story of the G180 started right after the 2003 Paris Air Show, when Grob contacted ExecuJet about becoming a distributor for the G160 Ranger turboprop single. ExecuJet officials answered by expressing their need for a light business jet that offered turboprop flexibility, said Olver. Grob then showed conceptual studies it had done recently and, after some adaptations, engineering design of the G180 was completed in September last year and the first fuselage began to take shape the following month.

Asked about the company’s choosing composite construction, Strohmayer answered, “There was no question about it, this is our know-how; Grob has not delivered a single aluminum aircraft.” Proponents of carbon fiber assert it to be as strong as aluminum but 44 percent lighter. In addition, they say, the parts count of a composite aircraft is 40 percent lower than that of a conventional business jet, although metal promoters would challenge these figures.

The German-based airframer claims to have delivered more composite aircraft– 3,500 of them, mostly gliders– than any manufacturer in the world. However, Grob has not delivered any aircraft during the past two years. “We have morphed into a development company,” Strohmayer told AIN.

Grob is reticent about where the program’s funding comes from. “There is an investor we do not name but who is definitely not ExecuJet,” a Grob spokeswoman said. As for Grob’s portion of the funding, AIN understands it is possible thanks to the group’s owner.

Grob’s Development Programs

Such support for the SPn Utility Jet is all the more striking because the G140TP four-seat trainer and the G160 are not certified yet and both still await a first order. Although it had slowed before the Paris Air Show, the G160 program has since ramped up again. Flight testing is under way and certification is pegged for the middle of next year.

Some might wonder if it wouldn’t have been easier for the company to certify the G160 Ranger before beginning certification work on the SPn. “It would have been easier for everyone,” Strohmayer conceded. But time to market was the driver on the jet program. “Once you have identified the niche, just go,” he added.

Marketing people did not always have the final decision. For example, the marketing team would have preferred a T-tail. But the cruciform tail won thanks to its weight advantage.

Assembly is made easier by the high level of parts integration composite materials allow. For example, when Grob took the as yet unflown prototype to the Paris Air Show, it took five people only two hours to disassemble the airplane. In Paris, the same team reassembled it in about four hours.

Strohmayer told AIN that the G180 is not 100 percent new. “It has the same cross section as the G160 at its maximum width,” he said. As a result, the company could apply some of its experience with the 160 to the 180. The G160 wasn’t a new airplane either; it was a longer-range, pressurized derivative of the G140, itself a derivative of the G120 piston-single trainer.

While Grob is in charge of development and manufacture, Zurich, Switzerland-based ExecuJet Aviation Group is responsible for sales and support. For customer support, ExecuJet plans to use its existing network of airframe and engine maintenance service facilities.

Customer interest in the jet has come mainly from Europe and North America as well as from Australia and South Africa, where unprepared runways are common. “We can accommodate a U.S. customer now. But we look forward to establishing a U.S. operation,” Olver clarified, adding that the company is studying several options. Training will be offered first in Europe and then in the U.S.

Grob is promoting the G180 SPn jet as a King Air replacement. “We say ‘utility’ as in an SUV [sport utility vehicle], not as in a pick-up truck,” Olver pointed out. The SPn therefore features a reinforced landing gear, a wide door and quick-change capability. “Seats, cabinets and the lavatory can be removed in one hour,” Olver said.

Performance specifications include a 77-knot stall speed (at max landing weight, forward cg, landing configuration), 4,360-feet-per-min rate of climb (at ISA, sea level, mtow) and a 3,000-foot balanced field length. Max payload of the single-pilot, nine-passenger aircraft is 2,491 pounds, and mtow is 13,890 pounds. Standard range (one pilot and six passengers, 100-nm NBAA IFR alternate) is 1,800 nm. Max-payload, mtow range is still 1,280 nm.

The utility jet is powered by two 2,800-pound-thrust Williams FJ44-3A turbofans. The airplane’s maximum cruise speed of 407 knots is lower than that of the competition because “we elected to optimize the wing for fuel capacity and short-field performance,” Olver said.