Avidyne’s Entegra brings glass cockpit to pistons

 - October 17, 2007, 6:02 AM

When I was shopping for an affordable (that means “old”) Bonanza, one of the mods that I really wanted was a “center stack” panel. V-tails of my vintage came from the factory with 1950s automobile-style panels. All the heading, attitude, airspeed and altitude data was there, but you had to hunt for it and then pull it all together in your mind’s eye. The center-stack mod placed all the radios in a single stack to the right, and the critical instruments on a floating panel in the now-standard T-configuration in front of the pilot, greatly relieving a lot of the mental gymnastics.

But compared to the Avidyne Entegra primary flight display, my panel looks more suited to a Civil War-vintage submarine. Of course, as a $24,500 option on new Cirrus SR22 four-seat piston airplanes, the Entegra costs about half what my entire airplane is worth–and if I wanted to buy one from Avidyne without the SR22 attached, it would be about $46,000. But for someone footing the cost for a new Cirrus, the Entegra option looks like a bargain.

Here’s what you get. The Avidyne FlightMax display is 10.4 inches diagonally across. In the landscape format chosen by Cirrus (portrait is available also for other applications), it dominates the panel in front of the pilot. The Entegra’s accompanying multifunction display is identical in size and incorporates navigation data, moving map and displays datalinked information such as traffic, Nexrad weather and stormscope readouts. But the PFD is what’s new, at least at this price.

On the bottom half of the display is heading and nav info, displayed on a black background just like the big boys and girls flying the jets have. On the top half, the Entegra PFD has tapes to show altitude and airspeed, including trend bars, and a “virtual” needle displaying vertical speed. But it’s the attitude reference line that’s unique. The brown-on-bottom, blue-on-top line extends the entire 8.3 or so inches across the display. Some pilots have complained that it distracts from the airspeed and altitude tapes, but the idea is to provide the most prominent horizon reference possible, mimicking the actual horizon as seen out the window under VFR conditions. The electronic horizon line is constantly within the peripheral vision of a pilot glancing sidelong to tune a radio or reach for a chart in the back seat. It’s why Cirrus president Alan Klapmeier chose the landscape format for the Entegra in his company’s airplanes. His aim is to create an airplane that can be flown on instruments as intuitively as it is under VMC. He shares his vision with Dan Schwinn, president of Avidyne.

The secret is an automatic heading reference system (AHRS) driven by a software matrix that combines input from GPS and air-data computers with input from low-cost micro-electronic mechanical sensors (MEMS) such as those used in automotive anti-skid and stability-augmentation systems. The so-called “tuning-fork” MEMS provide short-term acceleration input, but aren’t sophisticated enough to do the job alone like the automatic heading and reference systems (AHRS) designed and marketed by Collins for small jets. So Avidyne’s software uses multiple inputs to compensate, including a pendulum system that constantly realigns the “gyro” in level flight, but is smart enough to know when to shut itself off and let the MEMS take over when the aircraft begins to maneuver.

The Entegra is big news for the piston-powered pilot population, but Avidyne could expand its horizons to include light jets. In fact, if Cirrus opts to go forward with its nascent plans to build a single-engine jet, the Entegra system could be the foundation of its appeal to owner-pilots who need to fly IFR on occasion, but who haven’t the time or opportunity to stay proficient at flying by old-style instruments.