Auto Pilot Disconnect

[rfazio1951]

I have been having the auto pilot switching off on me during flights recently. It switches off with the announcement, "autopilot disconnect". Then last night it disconnected, and I got a message that the auto pilot servos were unavailable. I could not get them to work and flew the rest of the short flight by hand. Once we landed, I shut down the system and rebooted it. The servos were back online working fine. Any ideas??

 

[Carl_Froehlich]

What were the condtions of flight - as compared to whatever you set for autopilot minimum and maximum air speed?

Carl

 

[rfazio1951]

It was in the evening with very calm conditions. I was in cruise at my normal speed, 150 knots. We were flying IFR for a 30 minute flight. My min and max speeds in the autopilot settings are 90 and 210 if I remember correctly.

 

[airguy]

Servos unavailable could be a power issue, check power and ground.

 

[jakej]

Richard - having both servos disconnect is unusual as I’m sure you would have independent power to each ?
Do you have the ‘disconnect’ resistor/s installed ? ( FWIW) I never install those & haven’t had any requests to add them.
Is your AP Panel affected by the Service Bulletin ? (had to ask).

 

[rfazio1951]

Yes i have two breakers, one for each servo. A disconnect resistor? NO. AP panel? I have to check. Thanks for the info, i‘m on it.

So, the disconnect resistor seems to be for disconnect switch failure? I have to look into that. The AP service bulletin is for the auto trim feature. I do not have auto trim connected. I’m using manual trims.

 

[jakej]

My bad, I should have asked more, assumed too much -
A/P Panel is an unknown but likely not fitted ?
Resistors = not required & not wanted/needed by some.
airguy covered the power/ground possibility.
If A/P panel not fitted, power & grounds are ok, & for both servos to go offline I‘d be thoroughly checking the wiring to the servo disconnect button fitted- IF you have a remote one fitted.

 

[rose1265]

I have been having the auto pilot switching off on me during flights recently. It switches off with the announcement, "autopilot disconnect". Then last night it disconnected, and I got a message that the auto pilot servos were unavailable. I could not get them to work and flew the rest of the short flight by hand. Once we landed, I shut down the system and rebooted it. The servos were back online working fine. Any ideas??

I have been having a random A/P disconnect problem for several months. Just goes off. The TINY AP color change when it goes off is very hard to see. Usually I know when the plane starts vearing off course. Have sent Dynon dumps to see if they could tell what is causing the disconnect. Have not heard from them. Just finished condition inspection and rechecked the 3 extra leads (red, blk, yel) and the disconnect switch. Will fly tomorrow and see if that helps. I don't think there is a problem with the svnetwork.

 

[swatson999]

A/P D/C is via short to ground, isn't it?

Black (ground) wire somewhere is chafing, maybe?

 

[Rhino]

A/P D/C is via short to ground, isn't it?

Yes.

 

[jakej]

A/P D/C is via short to ground, isn't it?

Black (ground) wire somewhere is chafing, maybe?

Read last sentence of post #7 again.

 

[airguy]

Pull the user data from the Skyview and look at the data in Excel. One of the columns of that data is for Autopilot Disconnect, look for the time/date stamp and that value to go positive - that tells you that the system is seeing the disconnect line being connected to ground. If that was happening at a time WITHOUT you pressing the autopilot disconnect button, then you have a chafed disconnect wire somewhere shorting to ground.

 

[rfazio1951]

I think I have it fixed. After answering that I had two feeds fused at 5 amps each, I went back and checked. I realized I had one 5 amp feed, with 20 gauge wire for both servos. I re-feed the aileron servo with a second 20 gauge line to a spare breaker. I flew it and it seems to be fixed. Very strange that I’ve been flying it this way for years, 10, I think. now it starts disconnecting? it’s fixed, I’m happy.

 

[Rhino]

it’s fixed, I’m happy.

That's what matters.

 

[swatson999]

Just be careful...it sounds like you fixed it, but maybe didn't really figure out root cause, so the fix might only be temporary.

Fly safely...

 

[wilkersk]

...Very strange that I’ve been flying it this way for years, 10, I think. now it starts disconnecting?...

Could be a breaker going bad or a wire in the power circuit frayed to the point that its getting hot. 2 SV-32s pulling 1.3 amps each at 100% torque could tax a 5A rated circuit that's no longer working to spec. It could even be a connection that is no longer solid and inducing a high resistance. that resistance could drop enough voltage to pull the servos off-line. I once had a gripe that would intermittently cause the engine fire warning lights to illuminate in both engines. Spent days tracing it to one specific PIDG ring terminal on a terminal strip that was so corroded it would occasional read as an open.