Garmin’s GFC 600H helicopter flight control system (HFCS), unveiled two years ago at Heli-Expo, is nearly ready for installation in customer helicopters. The company (Booth 4910) has been giving pilots demonstrations of the system’s features in an Airbus AS350 AStar, and certification of the system is “imminent,” according to Garmin.
The GFC 600H is available in a two-axis or three-axis configuration—both have pitch and roll servos, with the latter also having a yaw servo. Later, Garmin will add a servo for the collective, according to Jack Loflin, Garmin’s engineering flight-test team lead.
To install the GFC 600H, a Garmin primary flight display is also required. The G500H TXi, for example, provides helicopter terrain awareness and warning system, Garmin’s WireAware wire-strike avoidance, synthetic vision, multiple video inputs, night-vision goggle compatibility, and “a graphical map overlay within the horizontal situation indicator (HSI) for most display formats.”
The GFC 600H is a “fly-through” flight control system, which means that it is similar to stability augmentation system-type helicopter autopilots in that it maintains a stable state that frees the pilot to perform other tasks and not have to concentrate on maintaining the helicopter’s attitude all the time. Loflin uses the analogy of a fixed-wing airplane’s inherent stability to describe how fly-through stability works.
“Airplanes are inherently stable. Helicopters are not,” he said. The lowest state or mode for the GFC 600H is attitude hold mode (ATT), which makes the helicopter feel a lot like a stable airplane by holding pitch and roll steady, but also allowing the pilot to make changes in the flight path without shutting off the system. “You can go hands-off stick indefinitely without the helicopter going in some random attitude,” Loflin added.
With the optional yaw servo, in ATT mode the HFCS holds heading in hover and keeps the inclinometer ball centered in cruise. In future versions, yaw trim also will be available.
In ATT mode, the pilot can easily change the reference point by moving the controls to change the helicopter’s position, then pushing the force-trim release (FTR) button on the cyclic to lock in the new reference point. Or the pilot can push the four-axis (beep trim) switch on the cyclic to make small changes to the reference point.
ATT mode holds zero degree roll angle (and heading if yaw servo-equipped) and airspeed. But once accelerating above 45 knots, upper or coupled modes are available, such as HDG, NAV, APR, IAS, VS, and ALTS, “like any autopilot,” said Loflin.
The ability for the GFC 600H to hold the hover position by integrating groundspeed and position and not using attitude hold is unique, according to Loflin. Also unique for this HFCS is Garmin’s Helicopter Electronic Stability & Protection (HESP) limit cueing, which helps the pilot avoid excessive bank and pitch and overspeed and underspeed conditions.
In the AStar, the limits are 46 degrees of roll and +14/-13 degrees of pitch. “The onset is gradual and it ramps up over a period of additional pitch/roll exceedance,” he explained, with the system nudging the controls to help the pilot return to a less radical attitude.
HESP engages whether or not the HFCS is switched on. Like Garmin’s fixed-wing autopilots, GFC 600H includes a level (LVL) button, which automatically returns the helicopter to a level-pitch, zero-bank attitude, a great help during inadvertent VMC into IMC encounters.
The GMC 605H mode controller is night-vision compatible and contains its own attitude sensors. Garmin’s G500 TXi display also has its own sensors, and both sources are compared, and if there is a disagreement, the HFCS disconnects.
For helicopters with teetering rotor systems, the GFC 600H’s HESP protects against mast bumping caused by negative g loads by nudging the cyclic back toward positive g. The GFC 600H can be installed on a variety of helicopter types, with the Bell 505 next in line. In any helicopter, the HFCS automatically recognizes the position of the collective and when pulling power, will move the pedal in the correct direction to compensate for torque.
The GFC 600H starts at $79,995 and requires a G500H TXi display, which retails for $23,495 for the 7-inch and $27,495 for the 10.6-inch display.
Flying GFC 600H
Along with the three-axis GFC 600H HFCS and the required G500H TXi touchscreen display, Garmin’s AStar also hosts the latest GTN 650 and 750 Xi touchscreen GPS navigators with faster processors, brighter displays, and wider viewing angles and the Flight Stream 510 wireless gateway. With so many touchscreens, the GFC 600H makes it much easier for a lone pilot to manipulate the touchscreens and focus on other important operational issues rather than manipulating the flight controls.
During a demo flight of the GFC 600H, I was able to experience how even in the lower ATT mode, the HFCS tightens up the “wet noodle” feel of the helicopter so that the AStar feels much more stable.
After taking off from McNary Field in Salem, Oregon, where Garmin engineers developed the new HFCS, Loflin switched off the GFC 600H and handed the cyclic and collective to me so I could feel the AStar’s normal “native” sensitive controls. Loflin then took the controls to demonstrate to me what happens to the helicopter after letting go of the controls, “to give you an idea of how unstable the helicopter is.” Within a handful of seconds, the AStar climbed and banked to the right. He then engaged the HFCS in ATT mode, which holds roll and pitch steady. “Now if I let go, it’s going to hold this attitude indefinitely,” he said, and it holds heading and speed close to what they were when switched on.
Loflin then banked to the right onto a new heading, and the system rolled the helicopter level and maintained the new heading. I tried a similar turn, and the cyclic felt a little springy instead of the normal sensitive looseness.
Next was a low-speed demo. Loflin selected ALT mode then lowered the collective to reduce power. At 45 knots, we heard a “low speed” aural and the HFCS lowered the nose to maintain 45 knots. We could hear and feel the blade slap as the blades hit their own wake. After descending a few hundred feet, Loflin added power and we climbed back to our selected altitude.
Loflin then added a bunch of power so we could see the overspeed feature. He set the HFCS to put us in a vertical speed (VS) descent, and as the speed closed in on the VNE barberpole, we heard a “max speed” aural and the helicopter’s speed stayed just below the redline. (The redline adjusts on the G500H TXi airspeed tape depending on certain variables). Loflin explained that if the helicopter is decelerating or accelerating rapidly, the HFCS will start mitigating the change to help prevent exceeding the low-speed or high-speed limits.
Next was a demo of HESP limit-cueing. He rolled to 60 degrees to the left and explained that he could feel that he was “fighting it” to hold that steep bank. I tried the same in a roll to the right and could feel the controls pushing back against me. I banked steeply to the left and felt the same strong pushback.
We happened to be near a sandbar in the middle of a river, so Loflin, noting that sandbars are part of public land, took us down for a demonstration of the HFCS’s hover capabilities. About six feet above the sandbar, the HFCS was in groundspeed (position) hold mode. “It’s going to try to hold the helicopter right over this position,” he said. At first, he didn’t have the yaw servo engaged, but the system maintained heading pretty well. With the yaw servo off, Loflin could easily pedal turn to a new heading, and then it maintained that. But after switching the yaw servo on, using a switch mounted on the collective, the heading hold was even more steady. “I’m completely hands off the cyclic,” he said, although he kept control of the collective to help manage the height above ground.
We climbed away from the sandbar and I took over the controls in ATT mode. I used the beep trim to make small changes to the climb attitude, then captured the current altitude by pushing the ALT button on the mode controller, and heading with the HDG button (after centering the heading bug on the HSI). Then flying was simply a matter of turning with the heading bug and adjusting the selected altitude.
I pulled up the terrain display on the G500 TXi and could see some hills ahead of us that we needed to climb over. We set the altitude select set to 1,500 feet and selecting VS on the mode controller, we climbed in VS mode until we captured the selected altitude.
Loflin briefed me on the flight path we needed to follow to avoid causing too much noise to residents below us and to avoid the Class C airspace around Portland International Airport as we flew to Portland Downtown Heliport. As we flew along the Willamette River, we could see powerlines crossing the river on the moving-map’s WireAware display, a handy feature for a machine that usually flies close to the ground.
Loflin took the controls for the final approach to Downtown Heliport. “I often fly my approaches with the force trim release held,” he said, “which reduces the force but provides me some spring-tension feel on the controls.” Loflin positioned the helicopter in one of the heliport’s parking spots, and we shut down the engine.
After lunch, which demonstrated the ultra-convenience of this heliport and Portland’s progressive attitude toward helicopters, I lifted the AStar off in “wet noodle” mode with some help from Loflin, then accelerated and climbed south along the river for the flight back to Salem.
Flying south of Portland, I really came to appreciate the GFC 600H’s ability to hold the AStar stable, allowing me to look around for traffic and terrain, manipulate the avionics, and otherwise manage the helicopter. This kind of HFCS is a major safety improvement.
Loflin demonstrated some mode changes as we flew, explaining that HDG and ALT modes are what he typically uses when flying cross country. The inclinometer was a little off, which I could have fixed with some pedal, but it was easier to turn on the yaw servo, which straightened out the helicopter perfectly.
We did some LVL button demos, with Loflin putting the AStar into steep climb and bank situations, then recovering to straight-and-level as soon as I pushed the LVL button. There are two ways to engage LVL, with a button on the mode controller or a button on the cyclic. The HFCS remains in LVL mode until a different mode is selected. “It’s pretty slick,” he said. “That could certainly save your bacon some night.”
For the arrival into McNary Field in Salem, I wanted to see how the GFC G600H flies a GPS approach, so I set up the RNAV (GPS) Rwy 13 approach. This is a simple and typically Garmin-ish procedure using the GTN 750, and of course made easier because the HFCS was keeping the AStar stable while I used the GTN’s touchscreen to set up the approach.
I pushed the APR button on the mode controller as we neared the inbound course, and then we intercepted the course. On reaching the final approach fix, the AStar promptly followed the glide path as I lowered the collective to keep the AStar at about 80 knots. I uncoupled the approach as we descended just to feel how easy it was to hand-fly the approach.
Back at the airport, we asked the tower controller for permission to practice near a convenient spot used by local helicopters, and I practiced hovering in groundspeed mode. While the helicopter doesn’t sit 100 percent still, I could easily make it do what I wanted. I switched off the yaw servo to make pedal turns, tried flying sideways and backwards, and I felt like I had excellent control the whole time. At one point, as I was flying toward the hover spot, I engaged the HFCS groundspeed mode too early, before coming to a full hover, and the system didn’t let me get away with it. I had to turn off groundspeed mode, reestablish a good hover, then switch it back on.
I performed at least five landings and takeoffs, feeling increasingly confident with each one, then at Loflin’s suggestion, I flew back to the Garmin helipad next to the company’s hangar and managed to land in the center of the H circle painted on the asphalt.