One of my biggest gripes with my Cirrus, was the autopilots inability to track straight on any sort of navigational aide, especially an ILS. Especially if it was windy or even gusty, the S-Tec 55X was incapable of accurately intercepting or tracking these signals and would wander back and forth, back and forth, back and forth. Now there is an option that will not only provide digital preciseness, but also add more safety to boot!
The Avidyne DFC90 was released a little over a year ago with the primary flight ship being the Cirrus SR2X. They marketed this autopilot directly at the S-Tec 55X in hopes to lure a fairly large market of aircraft owners to upgrade to a far superior and safer autopilot.
The Avidyne DFC90 is an attitude based autopilot, whereas the S-Tec it replaces is rate based. The DFC90 follows the attitude indicator and the AHRS. Rate based autopilots like the S-Tec, use a turn coordinator for reference. This makes the DFC90 extremely precise and far more accurate than the S-Tec. Turns are exactly standard rate, intercepts are way more precise, level offs from climbs and descents are also much more smooth and right on target. The DFC90 flies approaches beautifully, and extremely precise. An ILS approach is flown straight and true all the way to minimums. No more back and forth drunken sailor effect like the S-Tec did. It now truly flies like it’s on rails!
In addition to the increase preciseness of the DFC90, Avidyne incorporated its “Envelope Protection.” One of the major safety issues using the S-Tec, is that you could stall the aircraft with the autopilot. There have been several accidents in the Cirrus fleet alone, where pilots get busy and aren’t monitoring the aircraft and the aircraft is set up to climb at a rate in which it cannot keep up with. The end result is that the autopilot flies the plane into an autopilot induced stall. The envelope protection of the DFC90 eliminates this issue. If you command a climb that the aircraft is not capable of, the autopilot will allow the climb until the airspeed bleeds off and then the autopilot will hold a safe speed, not allowing a stall. When this takes place, a voice will sound off in the headsets stating “Speed Protection Active.” The same applies on the over speed side if you command a vertical decent that would result in exceeding Vne, the DFC90 will intervene and not allow an over speed to occur.
Another one of the major improvements of this system is the “Straight and Level” button. This is a great safety feature for a pilot who might be in IMC or flying at night and become disoriented and put the plane into an unusual attitude. If the pilot becomes disoriented, all he has to do is push this button and it will bring the plane back to straight and level.
The DFC90 is a VAST improvement over the S-Tec 55X autopilot. This upgrade gives Garmin Perspective precision to your Avidyne Entegra plane at a significantly lower cost. If you own an older S-Tec 55X autopilot, I highly recommend you upgrade to the DFC90. It is the best money spent on an upgrade for your Cirrus!
How many hours have you flown with the autopilot now? Are you still liking it just as much? Any service issues?
ReplyDeletePhilip, I flew it for over a year and about 230 hours. Once we got it all configured it works awesome! I especially like the envelope protection, level button, and the IAS settings. The later I learned to use a lot on climbs since it just works so well and you don't have to fiddle with anything to keep from getting too slow. If you are rapidly climbing the e-protection will catch it if you are in busy airspace and IMC and aren't watching, but setting the IAS for climbs is just easier and safer IMO. I didn't have any service issues at all and it just works. The only recommendation I would suggest is to do WAAS (G430W or GTN650) since it significantly improves the preciseness of the autopilot. It is a much better autopilot than the Stec 55X, but still tends to wander a little in windy conditions. With WAAS, it's rock solid and truly on rails. I didn't have WAAS, but got to fly one with and you could definitely tell the difference. It's a great upgrade though over the Stec regardless.
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