Chelton offers lightweight helo autopilot

Aviation International News » December 2006
December 8, 2006, 8:57 AM

Flight-testing is well under way for a new helicopter autopilot that, compared with other currently available systems, cuts both weight and cost in half, sources familiar with the project told AIN.

The HeliSAS digital autopilot, under development by Chelton Flight Systems and Hoh Aeronautics, is a full-authority system that can be installed in any helicopter with hydraulic controls. HeliSAS supports all conventional autopilot modes, as well as Chelton’s highway-in-the-sky roll and pitch steering when coupled to Chelton’s synthetic-vision EFIS.

The HeliSAS autopilot, which weighs less than 12 pounds, is currently flying under VFR in a Robinson R44 with the goal of eventual IFR certification in the R44, as well as larger turbine helicopters such as the Bell 206/407 and Eurocopter AS 350/AS 355.

Test pilot and NASA control systems expert Roger Hoh designed and developed HeliSAS and subsequently sold its production rights to Chelton. According to Hoh, Chelton is financing the product’s initial FAA certification in the R44, which the companies say they are on target to achieve by June.

Before working on HeliSAS, Hoh spent a number of years at the NASA Ames Research Center in California researching flight control systems for helicopters for the U.S. Army. Thinking that there might be a civilian application for this technology, Hoh earned a grant from the NASA Small Business Innovation Research (SBIR) program in 2001 to develop a lightweight, low-cost stability system that would make helicopters easier to fly.

“I got my helicopter rating in 1977. I said, ‘This is ridiculous, it’s so unstable. Someday I’m going to do something about this,’” Hoh said. “We had a little simulator in our office. It was all on paper.” When the concept began to take shape and look more promising, Hoh bought a used R44 and developed a flying prototype of the system in 2003. At first it was a limited stability augmentation system but has since developed into a full autopilot, capable of hands-free hovering.

“A typical helicopter autopilot weighs 500 pounds and costs more than $200,000,” Hoh said. “Our target when doing the SBIR was $40,000.”

What makes the HeliSAS system so inexpensive? According to Chelton president Gordon Pratt, most existing helicopter autopilot installations require cutting into the aircraft’s hydraulics, which can be expensive. HeliSAS, on the other hand, is installed at the base of the cyclic and requires no hydraulic line cuts.

“The intent is to have it on all the time,” Hoh said of HeliSAS. “What it would do is make the helicopter easier to fly. The pilot would have more time to do his job. Right now you cannot let go of the cyclic stick to unfold a chart. With HeliSAS you can take your attention away from keeping the helicopter right-side-up to attend to things like checking the weather and navigation.”

Pratt said that he anticipates HeliSAS will cost 30 to 40 percent less than existing
systems. He expects Chelton to begin taking orders for the system at next year’s Heli-Expo, to be held from March 1 to 3, in Orlando, Fla.

Possible R44 Autopilot?
Pratt, a fixed-wing pilot, said that his previous experiences hand-flying helicopters have been comparable to “a wild rodeo.” He said that with HeliSAS installed in the R44, he was able to hover and land in a few hours. “It absolutely blew me away.”

Hoh said HeliSAS makes the R44 easier to hover in a strong wind, which he hopes will prove particularly useful to EMS operators. “Ultimately, we’d like to extend this thing to get light helicopters IFR certified,” he said. “Right now, you can’t really certify a light helicopter IFR because they’re too unstable.”

At this year’s Heli-Expo in Dallas, Robinson Helicopter Company president Frank Robinson told AIN that he was planning to test-fly an R44 equipped with an autopilot, with the goal of getting the four-place piston single certified for IFR operations. “Now we’re talking to him a lot,” Hoh said of Robinson. “Frank has flown it several times.”

Last month v-p of product support Kurt Robinson confirmed to AIN that the Torrance, Calif. company is evaluating “an autopilot for the R44” but said it was “way too early for Robinson to make any public comments.”

Pratt said Chelton is about 250 hours into the flight-test program on the R44 and will probably continue for another 100 hours before it achieves FAA certification. Hoh said the primary task at this point is ensuring that “the probability of a hard-over is essentially zero.”

Hoh said that two of the principal development challenges were keeping the weight low and finding a high-quality, low-cost, electrically driven, autopilot-capable attitude gyro. Engineers eventually settled on one made by Castleberry Instruments and Avionics of Austin, Texas, to use in the R44. Future turbine helicopter installations will likely employ an air-data attitude heading reference system, or ADAHRS, he said.
“Current helicopter technology is heavy and expensive and takes a long time to install,” Pratt said, noting that HeliSAS can be installed on the R44 in less than 40 hours. “Having an autopilot that installs with the EFIS is a natural.”

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