The Line

Making sense of the data

The horizon lies bright and clear across my field of view. Which is strange, because this is Maryland and we're on day four of a high-pressure system that has allowed the murk to cuddle up against the Appalachians and blanket the Mid-Atlantic with 8,000 feet of gray.

I'm looking at Avidyne's FlightMax Entegra primary flight display (PFD), as installed in a Cirrus SR22. The top half of the screen contains an electronic attitude direction indicator (EADI) display, the bottom half an electronic horizontal situation indicator (EHSI). In the center of the EADI is an attitude indicator, with standard bars and turn hashes. Along the left side is an airspeed tape; along the right side are an altitude tape and a vertical speed indicator (VSI). Each displays information digitally, as do other EFIS displays currently on the market for all manner of aircraft from jets to single-engine homebuilts. The other half of the Entegra suite is in the center of the panel, an Avidyne EX5000 multifunction display (MFD) that shows moving-map, engine-monitoring, checklist, weather, and traffic information.

The difference between the EX5000 and other MFDs is that horizon. It not only runs through the center of the attitude indicator, but it also stretches across the entire width of the screen. I can't get away from it. This is important.

Dan Schwinn, president of Avidyne, flies as much as he can. In 500 hours of flying a Falcon 100 in recent years, he figures he spent about 50 hours in instrument meteorological conditions. And that was in an airplane that flew in all kinds of weather. Now he owns a Lake amphibian and estimates that he spent five hours in actual conditions during 75 total flight hours last summer. The fact is, the average instrument pilot flying a light single or twin doesn't spend that much time in the soup. And the pilots who do typically aren't 100-percent thrilled about being there. That's where Schwinn thinks the Entegra can help.

"We want the pilot to have the same comfort level flying IFR for 10 hours a year" as pilots who fly significantly more, says Schwinn. "We want to make occasional IFR flying as intuitive as VFR flying."

Schwinn believes that the Entegra's PFD can change the way pilots feel about flying in the clouds for two reasons. First, the horizon is so large and bright that it's almost never outside the pilot's vision field. And second, all the other critical information (airspeed, altitude, vertical speed) is right there along the horizon. Heading information is just below it, on the top of the EHSI.

The large display and intuitive layout let you detect any change in aircraft attitude almost immediately. During my test flight with the Entegra, I spent a lot of time looking intently at the PFD. But any time I looked outside for traffic, or over to the MFD or GPS for navigation information, I never lost the horizon line out of my peripheral vision. The moment I left straight and level — which was often when simultaneously trying to write and fly and look for other airplanes — I saw the horizon line move.

Perfecting the line proved challenging for Avidyne's engineers. The EADI relies on ADAHRS (air data attitude and heading reference system), a three-axis, solid-state gyro and accelerometer unit, combined with a flux-gate compass, for pitch, bank, and rate information. The ADAHRS is similar to those on corporate and commercial jet aircraft, with reliability and accuracy exceeding that of mechanical gyros. However, its sensitivity took time to calibrate. With the long white horizon line, "if you have a one-quarter-degree deflection, you see it," says Schwinn.

Avidyne is on target to meet Cirrus' goal of delivering the Entegra suite in its SR22 by the end of the first quarter of 2003, and plans to work closely with Cirrus on its "next best thing," according to Schwinn. Other aircraft manufacturers that Avidyne is currently working with include Diamond, Lancair, and Eclipse, although Mark Sandeen, director of business development for Avidyne, assures that "we're talking to just about everyone."

Having other critical information presented both in a digital readout and on a tape makes flying precisely not just a goal but an assumption. Before our takeoff from Maryland's Frederick Municipal Airport, the demo pilot gave me several key speeds.

"You want it at 101 knots for V _Y?" I ask as we're climbing out. I find myself hunting to keep the tape fixed at the 101 mark. I would never do that in an airplane with an analog airspeed indicator — even with an examiner breathing down my neck. It's not only possible to hold airspeed within a knot, but it's made easier by the addition of trend indicators.

Above the airspeed data block on the tape is a short blue bar indicating that my airspeed is increasing, but not by much. A similar bar is above the altitude readout. I'm climbing — but not by much. I add a little back-pressure to the side stick. Back on 101.

Altitude, heading, and VSI bugs can be set by using buttons along the right side of the PFD. The VSI bug works in conjunction with the autopilot — in this case an S-Tec/Meggitt System Fifty Five X. Since the PFD also replaces the turn coordinator, a small black-and-white triangle at the top of the attitude indicator shows if I'm staying coordinated. Instead of stepping on the ball, I step on the offset base of the triangle. It takes a minute or two to get the hang of it — most of the time it looks more like a mountain than the pyramid for which I strive.

The EHSI has four presentations from which to select: a 360-degree compass rose or a 120-degree arc with or without your flight-plan course on a moving-map display; a selectable RMI (radiomagnetic indicator) pointer is available on either presentation. The top data block to the left of the EHSI contains primary navigation information sent to the HSI needle, and you can cycle through navigation sources, such as GPS 1, VLOC 1 (VOR or localizer), GPS 2, or VLOC 2; a secondary nav source can be input in the second data block and fed to the RMI pointer. A third data block (labeled Aux ) exists for an additional text data source, such as the destination airport while you're flying an ILS approach. A wind vector shows the direction and speed of winds aloft as calculated by the computer.

Not to be outdone for clarity of presentation, the MFD partnered with the PFD gathers a full range of flight information (see " Pilot Products: Avidyne EX5000," July Pilot). The moving map displays a complete terrain and water base map overlaid with the flight-planned route input from one of the two Garmin GNS 530s (in the case of Cirrus' SR22 demo airplane). Weather — including radar, datalink, and lightning detection information — can be displayed directly on the base map with 19 ranges to select from. You can upload weather through Avidyne's proprietary narrowcast DX50 datalink system. With narrowcasting, you set up your preferences and the flight plan from the GPS unit communicates with the DX50, telling it where you're going next. The system then automatically sends METARs, TAFs, graphical sigmets and airmets, graphical TFRs, and Nexrad images for a predetermined area along your route using the Orbcomm satellite network and Avidyne's own servers, available by the end of this year.

Traffic information from either the Goodrich Skywatch or Ryan TCAD 9900B/BX systems also can be overlaid on the primary map. Nearest-airport information and engine monitoring via Avidyne's EMax (see " Cirrus SR22: Clear Vision," page 70) is available by scrolling from the Map page to the Trip and Engine pages.

I set up for the approach and the demo pilot programs the GNS 530 for the ILS 23 into Frederick. He asks if I plan on vectors to final, a default setting on the 530 for an approach without the hassle of a transition or procedure turn. I hunt around, thinking. And then I say, sure, I can give myself vectors. Gesturing at the MFD, I sigh, "It's all right there." I'm thinking a monkey could fly an approach with this system. In which case I'd do well to fly better than a monkey.

With the approach up, the curved paths of the missed approach and hold are displayed along with the inbound course to Runway 23. Using the PFD and MFD in tandem, I steer the airplane on a vector to the approach course well outside of the outer marker — a vector that keeps me clear of the prohibited area around Camp David, now five miles in radius, just to the northwest of the ILS 23 approach course. The only thing missing is profile information. The demo pilot calls altitudes and keeps an eye out for traffic as I reset the altitude bug and fix upon a good airspeed and rate of descent.

Although highway-in-the-sky (HITS) presentations — the stream of boxes or hoops a pilot flies through to track a course on a PFD — appear to be the future of aircraft control, Avidyne chose to steer away from HITS, claiming that the information presented on the Entegra PFD includes more than 80 percent of the information that a HITS display would, and at less certification risk to the company.

As Schwinn sees it, "There needs to be more integration between the nav receiver, the procedures, and the display" before HITS will work. For example, the information currently output from a typical navigation receiver "won't let me fly an ILS," according to Schwinn. "We think we've got it right," says Sandeen. "The PFD goes a long way toward reducing pilot workload. We think we've got a good product as it stands rather than a stepping stone to HITS."

This isn't about having a crisp, vibrant screen or a fun toy. This is about putting together the sensory information that your brain needs to keep the airplane sunnyside up and pointy-end forward when it cannot receive its usual cues: the natural horizon and the passage of terrain below. Without an omniscient eye that can cut through the murk, the next best thing is the information, presented in a way that makes spatial sense.

I flew the SR22 with the Entegra suite on an October morning. Later that afternoon, we had a photo mission scheduled for another aircraft. As I climbed out from Frederick, flying lead in a Beechcraft A36 Bonanza equipped with a flight director and analog HSI, I felt tunnel vision creep in. I had a safety pilot along, and I was glad for it as we cut up through the haze to get on top. Because although it was VFR, I kept close to the dials. And didn't I know it.

I wanted that long horizon line back.

Price: $45,995 for the PFD, $12,995 for the EX5000; $24,500 for the PFD as an option on the Cirrus SR22 (the EX5000C comes standard)

Contact: 781/402-7400; www.avidyne.com

E-mail the author at [email protected].