Installation manual

Avidyne | DFC90, 100 FAQs (Last updated: 26 June 2012)

This is accessible through the Avidyne Live forum at

http://avidynelive.com/forum_posts.asp .

(DFC90, 100) How can I be sure my aircraft will see better performance with a DFC

autopilot? You will. A digital autopilot is really just a bunch of equations but not all

equations are created equal and ours are better. We have an altitude estimator, gain

scheduling, cross feeds, feed forward, lift calculations and range-to-go estimations. The

results are better flight. You will see this at high altitudes, high speeds, altitude lost in

turns, stability in 50 knot crosswinds, course captures from any reasonable position or

attitude, ILS captures at 7 miles and 90 deg intercepts, no more s-turning during captures,

etc.

There are several field reports of roll oscillation and/or pitch porpoising in DFC-equipped

aircraft. Every one of these to date has been traced back to out-of-spec aileron-rudder

interconnect bungees (Cirrus configurations), trim motors or servos. There are several

threads on this topic with more detail on-line at

http://avidynelive.com/forum_topics.asp?FID=16&SID=7eezbafa2d84dcaadzacbd6439e6

365a&title=dfc90-dfc100-digital-autopilot . (updated 17 April 2012)

(DFC90, 100) What is the maximum intercept angle the DFC can smoothly

accomplish? 179.9 degrees.

(DFC90, 100) Does the DFC autopilot perform the same VS step down as it approaches

the target altitude that the S-TEC does? No it does not. An Entegra-55X combination

system would gradually step down the VS rate as you approach the target altitude and

some customers found that round off to be too gradual. The Entegra-DFC system has a

quicker and more precise level off capability.

(DFC90) Can you explain more about the Underspeed protection that comes with

Envelope Protection in the DFC90? Underspeed protection is designed to prevent

autopilot-induced stall conditions. If, between a combination of power settings or

commanded climb conditions result in a decaying airspeed to be approximately 1.2

Vstall, the autopilot will: provide an annunciation on the PFD that UNDERSPEED is

active; provide an aural alert in your headset that speed protection mode is active; flash

the engaged (green) lateral and vertical mode annunciators; and will adjust the aircraft

pitch angle and/or bank angle as required to maintain 1.2 Vstall. The system will stay in

this state until there is sufficient energy/airspeed to provide the original commanded state

through a pilot-commanded action such as adding power or changing the commanded

condition (e.g. lowering the requested climb rate, increasing the requested IAS value,

etc). The autopilot needs to be engaged in some mode for this protection to be active.

Envelope protection is also functional in Flight Director only operations. Release 2 adds

the capability to know flap configuration which improves the accuracy of the

determination of 1.2Vs. While optional for existing DFC90 equipped Cirrus aircraft,

Avidyne highly recommends adding the optional flap wiring for this improvement. All

other installs require the addition of the flap position wiring. (updated 17 April 2012)