Cobham HeliSAS Brings Viable Autopilot to Light Helicopters
Bill Antwerp of Gaffney, S.C., owns and flies a pristine Bell 407 with a newly installed Cobham HeliSAS stability and augmentation system and autopilot. With another pilot, he flew his helicopter from his home in South Carolina to Las Vegas for Heli-Expo ’13. At his first fuel stop, he texted Jamie Luster, director of sales and marketing of Cobham Avionics in Mineral Wells, Texas, saying, “I love the autopilot.”
Antwerp’s 407 is serving as Cobham’s HeliSAS demonstrator here, flying out of North Las Vegas Airport. Frank King, a retired LAPD pilot and experienced Bell 407 pilot, is conducting the demo flights. He had never flown with HeliSAS before he flew with Antwerp on the Sunday before Heli-Expo. Even though Antwerp’s insurance company had already vetted King, Antwerp wanted to fly with him, too. “It is my helicopter,” he told AIN.
Though my flight with King went swimmingly, this is not the typical setup with aircraft demos, which, in my experience, are usually flown with high-time, very experienced OEM test and demonstration pilots. But it does illustrate Cobham’s confidence in the simplicity and effectiveness of the product, or an amazing corporate recklessness. The latter would appear highly unlikely for an international corporation the size of Cobham.
The company has delivered more than 100 HeliSAS autopilots mostly in Bell 407s and 206s and Eurocopter AS350s and EC130s. The system received FAA certification in late 2011 for Part 27 helicopters, which must have maximum weights of 7,000 pounds or less and nine or fewer passenger seats.
HeliSAS also been certified by authorities in Brazil and Australia. At Heli-Expo, Cobham announced recent approvals by Europe’s EASA for installation of HeliSAS on Eurocopter AS350s and EC130B4s across the European Union and by the Civil Aviation Administration of China (CAAC) for installation on Bell 407s.
Cobham offers HeliSAS in three configurations: the stability augmentation system (SAS) alone; SAS with beep trim; and SAS and two-axis autopilot (pitch and roll) with beep trim. Antwerp’s Bell 407 has the latter, with the beep trim and SAS off button on the pilot’s cyclic only. HeliSAS was initially designed by Hoh Aeronautics of Lomita, Calif., with funding provided by a grant from NASA Ames Research Center. Cobham did further development and completed the initial STC. Cobham Avionics now has an exclusive sub-license agreement with Hoh Aeronautics.
The SAS on/off button is on the control panel on the far left. The panel also holds the autopilot buttons, from left to right, HDG (heading hold), NAV (navigation signal tracking), BC (localizer back course tracking), ALT (altitude hold) and VRT (glideslope hold). Luster said the panel was designed to be consistent with airplane autopilots. “It’s just like an airplane,” said Antwerp, who has some 4,000 hours in airplanes (singles and twins) and 2,000 hours in helicopters and holds an instrument rating in airplanes, but not helicopters.
Flying the 407
We had planned to fly the 407 on Sunday afternoon, but strong winds and turbulence during an earlier flight caused King to postpone our flight until Monday morning. After Cobham’s Luster, who is an airplane pilot, gave a quick overview about the HeliSAS system, King and I took off in stunningly clear skies, but gusty wind conditions, 15 to 20 knots, with Luster and AIN’s videographer in the back. King flew in the right seat, because the HeliSAS cyclic switches are only on the right cyclic.
Heading north, King switched off HeliSAS and passed control to me. I flew for a few minutes this way, getting a feel for the controls, as it was my first flight in a Bell 407. After a few minutes, King switched the stability augmentation portion of HeliSAS back on.
Luster said HeliSAS is meant to stay on all the time, although some pilots prefer to turn it off on landing. As we flew, King let me try the various autopilot functions of the system from the control panel, which is located below the Garmin 430 GPS at the bottom of the control panel’s center section.
HeliSAS controls the pitch and roll axes, so the tail rotor pedal and collective remain under pilot control. Flying SAS-only is very stable, but changes in wind will push the helicopter off altitude or course. The pilot can also “fly through” the SAS; release pressure on the cyclic and the helicopter will return to its previously commanded position.
Heading hold does just that. The pilot turns to the desired heading, pushes the “HDG” button and the autopilot will holds that heading. If the autopilot is connected to the HSI or EFIS, then the pilot can change heading with the heading bug.
Altitude hold maintains the altitude. If an updraft increases the helicopter’s altitude, the autopilot will initiate a descent to get back to the selected altitude.
NAV, BC and VRT couple to and track navigation signals, all very much like basic airplane autopilots. On our way back to North Las Vegas, King selected the ILS using NAV and the glideslope with VRT. They all worked as advertised, as I expected they would. Note that HeliSAS does not qualify a VFR helicopter for flight in instrument conditions, but there’s no rule against using it for practice instrument approaches in visual conditions.
Of greater interest to me, however, was to test the ability of the SAS to automatically recover the helicopter to a neutral attitude when the pilot simply releases the cyclic. After about 15 minutes of flying, I asked King if it would be OK to try this and he agreed. Gently at first, I started a shallow climb and let go of the cyclic. The SAS easily put the helicopter back level. Then I tried a descent, let go again and we were quickly back level. Experimenting with left and right turns had the same result. I quickly gained confidence in the SAS.
Then I tried climbing and descending turns in both directions, quickly increasing to about 35 degrees of bank, trying to imagine inadvertently flying into the soup and becoming disoriented. Releasing the cyclic seemed completely unnatural, but when I did it, the SAS quickly went wings level and brought the nose to the horizon. The system seemed to hunt a bit for the right attitude, and it was a bit rough for our passengers, but it got the job done.
HeliSAS won’t fly you out of inadvertent IMC, but it will keep you flying straight and level, which is a lot better than losing control of the helicopter and becoming another CFIT accident.
Antwerp and Frank both really like HeliSAS, and I after my short flight, I do, too.
During Heli-Expo, Luster said Cobham expects to fly about 17 demo flights in the Bell 407. o