Avidyne autopilots offer digital solutions for avionics retrofits

 - May 16, 2011, 8:20 PM

Avionics manufacturer Avidyne is displaying its full line of cockpit displays and flight control systems as well as its R9 integrated flight deck at this year’s EBACE show (Stand 1951). New for the company is the announcement that it is working with Aspen Avionics on an interface between the Avidyne DFC90 digital autopilot and Aspen’s Evolution retrofit cockpit displays.

The Aspen Evolution interface for Avidyne’s DFC90 is to be certified later this year, with pricing for the Aspen interface to be announced soon. Evolution displays include an integrated air data and attitude heading and reference system (ADAHRS), so the combination of the Aspen display and the Avidyne DFC90 autopilot delivers an all-digital solution for avionics retrofits.

The DFC90 is a slide-in replacement for the S-Tec 55X autopilot system in Cirrus airplanes equipped with Avidyne Entegra flight displays. DFC90 features include improved stability, indicated airspeed hold, straight-and-level button for one-touch unusual attitude recovery and Avidyne’s new flight envelope protection and alerting system.

Avidyne received FAA technical standard order (TSO) and supplemental type certification (STC) for its DFC100 digital flight control system in February. The STC covers installation in the Cirrus SR20 and SR22 aircraft. The company’s DFC100 adds new features for Entegra-equipped airplanes, including redundant attitude inputs provided by both flight displays, full FMS integration allowing coupled Vnav (vertical navigation) descents, approaches and missed approaches and full-time envelope alerting, which works even when the autopilot and flight director are not engaged, according to the company. The DFC100 also includes the straight-and-level button.

The DFC100 offers many features not available in more sophisticated aircraft and is a “turbine-class autopilot system,” according to Avidyne, with flight director, altitude, airspeed and vertical speed hold, Vnav and navigation capabilities for localizer/glideslope, Lnav/Vnav and Lnav+V.

The autopilot’s full-time envelope alerting system warns pilots of underspeed, overspeed or excessive bank conditions via aural and text alerts even with the autopilot off. When the autopilot is engaged, the protection system not only provides alerts but it also actively intervenes and prevents the airplane from stalling or flying too fast. The DFC90 flight control system offers both these capabilities, but the DFC100 also offers full-time envelope alerting, which works all the time, not only when the flight director is engaged.

With the autopilot engaged, both the DFC90 and -100 use the roll and pitch servos to keep the airplane within the flight envelope. During an IFR approach descent at reduced power, for example, if the autopilot is used to level the airplane when nearing the final approach fix, the pilot might forget to advance the power. The airspeed will decay and when the autopilot’s parameters are exceeded, it will normally turn off, leaving control to the pilot, who suddenly has to figure out what’s wrong.

With envelope protection, the autopilot’s aural and visual “underspeed” warning will alert the pilot and the system will also lower the pitch attitude to maintain a 20-percent margin above stall speed, according to Avidyne. If the airplane is turning, the system will also reduce the bank angle to help maintain the 20-percent margin.

Flight envelope protection can also help a pilot survive an oxygen system failure. If a pilot is flying at high altitude in a turbocharged airplane and suffers from hypoxia due to oxygen system failure, the Avidyne autopilot will maintain altitude until the engine runs out of gas. Then, instead of allowing the airplane to stall after the autopilot exceeds limits and turns off, the envelope protection system will lower the nose to maintain the 20-percent stall margin, allowing the airplane to descend to a lower altitude where, hopefully, the pilot will wake up, switch to a tank with fuel and restart the engine or make an emergency landing.

Other unique DFC100 features include the Vnav mode, which automatically starts descent at the computed top of descent point and climbs to and levels off at the target altitude during a missed approach. The DFC100 also works with the R9’s FMSVectors feature. This allows the autopilot to follow the dashed magenta vectors line on the HSI display, after the HDG button is pushed on the autopilot, and then automatically intercept nav legs or approach procedures (when the magenta line is drawn to intercept the leg or procedure).

Other Avidyne products include the dual-antenna TAS600 active traffic advisory system, MLB700 broadcast datalink, MLX770 worldwide datalink and TWX670 tactical weather detection system.