Avionics: Garmin G3X

April 1, 2010

The first time I saw Cessna’s new SkyCatcher, I wanted one. Not the airplane—the avionics.

The light sport aircraft was equipped with a gorgeous two-screen Garmin primary flight display/multifunction display (PFD/MFD) known as the G300 that strongly resembles a slimmed-down version of the G1000 integrated avionics suite, which has rapidly become an industry standard.

When I asked Garmin when the rest of us could buy G300s, the answer was discouraging. The SkyCatcher’s avionics system is proprietary and will only appear in new Cessnas.

At AOPA’s 2008 convention, Garmin introduced its portable GPSMAP 696. The tablet-size 696 was the MFD half of the G300 ripped from the SkyCatcher and fashioned into a standalone unit. The 696 broke new ground in terms of its heft, capability, and price ($3,295). Almost immediately, a cottage industry arose offering creative ways to affix, at least temporarily, the bulky units to instrument panels. Docking stations, massive suction cups, and metal brackets made it clear that pilots would do just about anything to put the 696 in, or on, their panels.

Garmin responded with its GDU 375—a 696 frame (sans battery) meant to be permanently mounted in instrument panels of Experimental aircraft.

Now, the G3X takes that idea a giant step further by marrying the GDU 375 to a GSU 73 attitude and heading reference system (AHRS) and GMU 44 magnetometer derived from the G1000 system. The result is a one-, two-, or even three-screen PFD/MFD that brings unheard-of capability and sophistication to experimental and light sport aircraft.

By packing so much digital flight, navigation, and—since late February—engine information into a seven-inch screen (or two, or three), the G3X makes it possible for sport aircraft, even those with limited panel space, to carry solid-state avionics that offer real-time weather, terrain, traffic, TFRs, and IFR approaches.

David Buckwalter, founder of Avionics Systems LLC in Leesburg, Virginia, recently installed one of the first G3X units in my Van’s RV–3, a single-seat sport airplane designed as a day/VFR flier—and the results are transforming.

The RV–3 instrument panel is so small it could barely accommodate a standard “six-pack” instrument cluster. With a single com radio and transponder, all the panel real estate was spoken for. There was no room for a panel-mount GPS, so the sole navigation source was a portable unit attached by Velcro to a kneeboard.

The G3X installation required digging deep into the airframe—and it wasn’t always pretty. Buckwalter, six feet tall and 200 pounds, had to wedge himself into the diminutive airplane’s cocoon-like aft fuselage to attach the magnetometer. (He wanted it as far from the engine’s magnetic interference as possible.) He then removed the entire instrument panel and its now obsolete vacuum system. The attitude indicator and directional gyro were out, along with the suction gauge, vacuum pump, regulator, filter, and lines.

Buckwalter learned his craft at Embry-Riddle Aeronautical University in Daytona Beach, Florida, in the early 1980s. He launched his own firm in the early 1990s and worked on FAA-certified avionics only. But most of his business these days has shifted to high-end experimental aircraft such as Lancairs and RV–10s, and Garmin G900 panel installations have become a sub-specialty. Since the G3X uses similar components, he knew what to expect.

“The Experimental world gives me more flexibility to install the newest, most innovative products in ways that my experience tells me make the most sense,” Buckwalter said. “Things like synthetic vision and completely digital panels were available in the Experimental category long before that technology became available in Standard-category aircraft. Those are the kinds of things I like to work on.”

Most of the replacement RV–3 panel’s assembly took place at Buckwalter’s shop in Leesburg, and two weeks after the original was removed, the new panel had been painted, wired, and was ready to put in the airplane. Buckwalter installed and calibrated the new instruments in two days, and total shop time for the project was about 40 hours.

Flying the G3X

The G3X is wired directly to the aircraft electrical system and doesn’t have an internal battery. The AHRS aligns within two minutes (assuming the airplane is outside with good GPS satellite reception), and it is capable of finding itself while taxiing or realigning in flight. The single-screen PFD depicts flight instruments on top with a moving map/HSI on the bottom. The seven-inch (diagonal) display is the same as the 696’s, and it’s exceptionally bright and easy to read, even in direct sunlight.

In flight, the G3X speed and altitude tapes precisely match the data from the mechanical airspeed indicator and altimeter; the digital vertical speed tape shows none of the instrument lag that generations of pilots learned to expect with traditional instruments. Pitch, bank, and heading information appear instantaneously, and a white slip/skid ball at the center of the screen offers remarkable fidelity.

Unlike electromechanical gauges, the G3X has no pitch or roll limitations and won’t tumble in unusual attitudes. The display’s rapid refresh rate (five times a second) easily keeps up with the RV’s 120-degree-per-second roll rate, and aerobatic maneuvers such as Immelmans, half-Cubans, and hammerheads don’t bother it at all.

Point rolls are a different story, however, as the abrupt starts and stops are too quick for the AHRS to process, and the unit requires about one minute of level flight to reset itself.

A series of red chevrons appear when the pitch attitude exceeds 50 degrees nose up or 30 degrees nose down to guide pilots through unusual-attitude recoveries. As in the G1000, moving maps disappear during unusual attitudes and the display reverts to the HSI screen.

The G3X also has the capability to display traffic information when connected to a Garmin GTX 330 Mode S transponder; and XM weather, TFRs, and IFR approach plates are available through subscriptions. As with the 696, the charts disappear from the database when they’re six months old.

The button logic of the G3X is very similar to that of the 696, and it will seem familiar to GNS430/530 operators as well. Building and editing flight plans—and loading and activating approaches—are much the same, although the G3X/696 joystick brings some new twists to those accustomed to the 430/530 series. Unlike the 430/530s, however, the G3X map page shows airways—a major benefit to East Coast pilots where airway routes are the ATC norm.

The G3X also has a clever and useful “vectors” feature: A single soft-key push extends the final approach course 15 miles so that it’s easy to recognize on the map page. Also, the names of intermediate fixes appear on the moving map, a useful aid at busy times.

The moving map’s terrain features get quite colorful during approaches with the shading turning yellow and red at pilot-selected intervals. The G3X also offers vertical and lateral guidance throughout the descent and approach. A pair of tiny pink triangles appears with an “approaching VNAV profile” message; the vertical guidance triangle is situated next to the VSI tape, and lateral guidance is close to the slip/skid ball. The default setting for vertical guidance is a 500-foot-per-minute descent that disappears at 1,000 feet agl, although pilots can configure the rate of descent however they like. When linked to an IFR-approved GPS or nav radio the G3X can display glideslope and localizer signals all the way to the surface and, with proper calibration and pitot-static checks, be used for IFR flight.

Every G3X has a front-mount SD card, and there’s speculation that Garmin will someday use it to add Synthetic Vision Technology (SVT)—although Garmin is quick to point out that SVT was never promised to G3X buyers and there are no guarantees it will ever be offered. Still, it’s a tantalizing prospect.

The G3X provides exceptionally high situational awareness and navigational precision in a space- and weight-saving package. It makes the RV–3 a better sport airplane because aerobatics won’t harm the attitude instruments. Cross-country navigation is far more precise, and restricted airspace and adverse weather are much easier to avoid.

It’s hard to comprehend that sport aircraft and LSAs are being fitted with glass panels, solid-state ADAHRS; and 12-channel, WAAS-enabled GPS that many airliners and corporate jets would envy—but the G3X will make that increasingly commonplace.

Thank you, SkyCatcher!

E-mail the author at dave.hirschman@aopa.org.

Dave Hirschman

Dave Hirschman | AOPA Pilot Senior Editor, AOPA

AOPA Pilot Senior Editor Dave Hirschman joined AOPA in 2008. He has an airline transport pilot certificate and instrument and multiengine flight instructor certificates. Dave flies vintage, historical, and Experimental airplanes and specializes in tailwheel and aerobatic instruction.