Autopilot Power

flickroll · #1 11-16-2008, 05:25 PM

I'm wiring up my -8 for a Dynon autopilot. In the Bonanza that I recently owned the AP was powered through the avionics master. I'm not sure I like that and am thinking about powering it through the main power buss. What have others done? Pros/cons of either way?

Thanks

Jim Shannon
RV-8 N52VV
Charlottesville, VA

N941WR · #2 11-16-2008, 05:44 PM

Jim,

I don't know if one connection location is any better than any other, as long as you include a way to drop power to it. This goes for any autopilot, not just the Dynon.

In my plane, it is wired to the avionics buss.

DickDe · #3 11-16-2008, 05:47 PM

Jim...

I wired my auto pilot through the avionics master which controls the avionics buss. Why? Because all the electronics which are sensitive to voltage spikes (usually during engine start up or shut down) are controlled by the avionics switch which is turned on after the engine is running smoothly, meaning a stable voltage, and I shut them off before pulling the idle cutoff when voltage spikes could again be present. I don't know if the new generation electronics are that sensitive to spikes but that is my reason for an avionics master. It eliminates the need to shut each radio of individually and my TruTrak AP is also digital so I wired it to the avionics buss.

Dick DeCramer
N500DD flying
RV8 wings complete
Northfield, MN

flickroll · #4 11-16-2008, 05:53 PM

Agree with the thought for a QUICK way to un-power the AP. There will be a dedicated CB for it, and I may also use a SPDT on-off switch. Although I never have experienced a dysfunctional AP, you sure do need a quick way to get rid of it, just in case. I did experience a run away trim in the Bonanza once. Not a fun experience, and in the -8 I'm using a Safety-Trim trim controller which should minimize the chances of that happening in the -8.

Jim Shannon

mannanj · #5 11-16-2008, 06:40 PM

I'm not so sure there should be a dedicated power switch for the Tru-Trak Autopilot systems. They have an auto disconnect terminal in their DB-25 connector that you can put on your controll stick or any other place that's handy to instantly disconnect the auto pilot. This feature is built in, and has worked perfectly every time I have used iit n on my RV-8 over the last 240+ hours. I even have a switch placed so that my back seater can disable the autopilot shoud I become incapacitated.

There is something to be said for a seperate power switch though. Most solid state auto pilots need to be stationary for boot up. There are times when you might want to start the engine and be taxiing to the runway before you wait for the auto pilot to boot up.

If you're in this big of a hurry like that though, you might be like me and miss something on the before taxi, or the before takeoff checklist!

There's one thing good about homebuilding----------CHOICES!!!!!!!!!!!

RatMan · #6 11-16-2008, 10:59 PM

Quote:

Originally Posted by flickroll

I'm wiring up my -8 for a Dynon autopilot. In the Bonanza that I recently owned the AP was powered through the avionics master. I'm not sure I like that and am thinking about powering it through the main power buss. What have others done? Pros/cons of either way?

Well, the EFIS that controls the autopilot can be (should be) wired to the main (master) bus so I don't really see anything wrong with getting the power for the servos from the sameplace. The installation procedure is well documented in the lasted install manual from Dynon. Don't know which EFIS you'll be going with but here's one for a D180. Page 8-3 will pretty much answer your questions.

Jamie · #7 11-17-2008, 05:49 AM

FWIW, my my autopilot is connected to my main buss, and I have no switch or CB on it (just an ATO-type fuse). It is not on my essential buss. If something with the AP fubars, I'll just switch over to my e-buss.

BTW: I upgrade my firmware and flew with the Dynon autopilot last night for the first time.

First impressions: It's very smooth in the roll axis, but I can't get it to track a GPS waypoint. It will fly a GPS course, just not a waypoint. Weird. This is with my Garmin 496. I looked on-line and there is a firmware update available for the 496 and I've already upgraded it but have not had a chance to try again.

I couldn't quite get the pitch axis dialed in last night. It was wandering +- 100 feet...kind of made me seasick. I tried adjusting the sensitivity but it didn't seem to help. I'm sure it's just a setting tweak and I didn't have a lot of time to play with it.

I elected to not install the AP74 because I wanted to see how the Dynon AP actually performed first. After playing with the AP for a bit I think that I will probably install the AP74.

Brantel · #8 11-17-2008, 06:36 AM

Jamie,

Make sure the GPS is set to "Normal" under the advanced serial settings. In "Fast" mode, it leaves out some of the GPS labels that the Dynon might need.

mburch · #9 11-17-2008, 07:46 AM

Quote:

Originally Posted by Brantel

Make sure the GPS is set to "Normal" under the advanced serial settings. In "Fast" mode, it leaves out some of the GPS labels that the Dynon might need.

Well, I don't know about that... when the GPS is set to "Fast" NMEA output mode, none of the NMEA sentences that are omitted are really important for navigation. I could be wrong though.

mcb

Brantel · #10 11-17-2008, 08:06 AM

Quote:

Originally Posted by mburch

Well, I don't know about that... when the GPS is set to "Fast" NMEA output mode, none of the NMEA sentences that are omitted are really important for navigation. I could be wrong though.

mcb

Not sure which ones are left out when set to fast but all of Dynon's FAQ's, literature and responses to problems on their forum state that it needs to be in NORMAL and not FAST mode.

The manual for the 496 sez that a "minimum number of sentences are sent when set to fast at a 1 second interval" who knows what minimum includes? It is possible that the 1 second interval is to fast for the Dynon to parse the data????