AOPA Pilot Senior Editor Paul Richfield was in Houston to cover the rotorcraft industry’s premier show from Feb. 24 through 26.
Sikorsky Aircraft has unveiled its much-anticipated “X2” technology demonstrator—a next-generation helicopter prototype designed to exceed speeds of more than 250 knots in level flight.
X2 will achieve this goal through the use of rigid, counterrotating rotor blades, coupled with a fly-by-wire control system that slows the blades as forward speed increases. This, according to Sikorsky, mitigates the speed-limiting retreating blade stall phenomenon.
“We want to break the paradigm of 160 knots,” said Sikorsky President Jeff Pino. “With fly-by-wire, we can keep the rotor blades apart and stop the flapping. The control rods run inside the shaft of the rotor blade.
“At 210 knots, the main rotor blades start slowing, at the 265-knot design speed, the retreating blades are 80 percent in reverse flow with 90 percent of the thrust going through the [aft-mounted] six-bladed propeller.”
Plans are to power the X2 with a Rolls-Royce 801 turboshaft producing 450 shaft horsepower, coupled to the same automatic vibration control system on the Sikorsky S92 medium-lift utility helicopter.
Since the demonstrator has no tail rotor, hover turns will be accomplished with aerodynamic surfaces. In the interest of drag reduction, the X2 will feature flush-riveting and retractable landing gear.
“I don’t know when it will fly, or when this will be a production aircraft,” Pino said. “I’ve instructed our engineers to fly it when it is ready to fly. What we do know is that this could be the future of our business.
“This is not an airplane that we’ve taught to hover; it’s a true helicopter that will exceed 250 knots. We are not going to let [Sikorsky Aircraft founder] Igor [Sikorsky] down.”
Development of the Robinson R66—the company’s first foray into the turbine helicopter market—is moving forward at a “slow but steady pace,” according to founder Frank Robinson.
Speaking to a packed crowd, Robinson said the R66 prototype has been flying for several months, exhibiting handling characteristics not unlike that of the piston-powered R44.
“Of course there are some procedural differences, and it has that turbine whine on start-up, but the vibration was a little less than the R44 and the speed is the same or higher,” Robinson said. “The rate of climb is higher, but you expect that.
“Everything is going well—slower than it should—but we don’t want any surprises later on. This time we have the luxury to do everything in order; typically it takes about two years to develop a new helicopter.”
Robinson was enthusiastic about the R66’s powerplant; the new Rolls-Royce 300 turboshaft. He said the engine now flying on the prototype is “close” to the final production engine.
“It’s got a single-stage centrifugal-flow compressor and does away with all those axial flow blades on the [Rolls-Royce] 250,” he said of the model 300. “It’s a good engine and a good installation; Rolls-Royce has promised me the [time between overhaul] will be the same as the R44’s piston engine.”
Asked whether the R66 would have an electronic flight information system or “glass cockpit,” Robinson dismissed the technology as inappropriate to the aircraft and its visual flight rules mission profile.
“I’m not interested in anything that distracts the pilot from keeping his eyes outside the cockpit,” he said. “When [the displays] reach the point where the pilot can get all the information he needs with just a glance...we’re not going to put in anything that will reduce the safety of the aircraft.”
Robinson is also uninterested in autopilots, but did express interest in a “good, reliable,” stability augmentation system to provide helicopters with stability comparable to fixed-wing aircraft. But so far, he said, “the cost and weight numbers are too high.”
Despite developments with the R66, Robinson is also positioning his piston helicopters for future sales. Specifically, he would like to see the carbureted R44 Raven I augment and ultimately, replace the R22 in the primary training role.
“The R44 Raven I is always going to burn more fuel than an R22, but it’s still a much better training aircraft, with better autorotation characteristics,” he said. “This is particularly important among older [student] pilots.”
A bid to combine the best attributes of the Schweizer 333 single-turbine and RQ-8B Fire Scout unmanned helicopter has yielded the first new offering from the combined Sikorsky-Schweizer: the S-434.
Launched Feb. 24 at Heli-Expo, the S-434 will target a wide range of rotary-wing missions, with an initial focus on civil and military flight training, aerial law enforcement, and private utility flying.
Paul Schweizer, founder of the Elmira, New York-based manufacturer and now a vice president with Sikorsky Aircraft, said the S-434 will take operators where “the 333 never quite had the performance.”
The Rolls-Royce CR250-C20W-powered S-434 will carry 20 percent more fuel than the 333, with a 300-pound gross weight increase. At a base price of $933,000, the new aircraft costs $110,000 more than its predecessor.
Launch customer for the S-434 will be the Saudi Arabian interior ministry, which is slated to receive its first deliveries this summer. Schweizer said the first civil variants are expected to reach customers in about 15 months, following FAA certification.
February 25, 2008