Envelope Protection Comes to GA

Systems from Garmin and Avidyne that aim to prevent loss-of-control accidents are already showing up in light airplanes. Here's how one of them might just save your life.

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In this composite photograph, we show the envelope protection capabilities of the Avidyne DFC90 autopilot. The display, from my flight in a Cirrus SR22 with Avidyne's Jake Jacobson, shows us in a steep, nose-down spiral with the airspeed building and a rate of descent of approximately 4,000 fpm. The autopilot annunciation of "straight and level" indicates that this emergency recovery button has been selected as the active mode on the autopilot, something I'd done just seconds before I took the photograph. In fact, a moment later, the airplane had recovered to straight-and-level flight without pulling more than 2.2 G's in the process.Robert Goyer
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To see the envelope protection capabilities of the GFC700 autopilot, I simulated a level-off on an approach with full flaps and the power retarded. The system kept the airspeed at 70 knots while allowing a rate of descent of around 550 fpm to maintain that airspeed while giving visual and audible alerts of "airspeed."
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The Avidyne DFC90 digital autopilot, a slide-in replacement for the popular S-Tec 55X, features extensive envelope protection when the autopilot is turned on.
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The DFC90 features overspeed protection. On this maneuver, with the autopilot off, I put the nose down and let the airspeed build to just shy of the SR22's VNE of 201 kias. I then activated the autopilot, which raised the nose to prevent exceeding VNE.