Autopilot Problem or G5?

NealRomeoGolf

NealRomeoGolf

Final Approach
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Today flying home my autopilot decided to stop working. It would drift left off of the GPSS or from the heading bug. I could get it to fly straight if I pointed the heading bug 10 degrees to the right from what I needed. Is the GAD29B having issues and converting wrong or has my Century IIIc stopped working? My first leg of the day it worked perfect. 45 minutes later it was doing this. Weird.
 
I'd put money on (but not into) the Century IIIc being the issue. My Narco #2 NAV sometimes works, sometimes doesn't. That's getting replaced by something else, soonish.
 
My WAG …. It’s the static lines
 
I'd wiggle the wires.

Then make the appointment for the G500.
 
I'll pay for yours if you pay for mine.


Oh wait....that doesn't help.
 
One odd thing was on the ground and parked I put the heading bug to the right, turned on the AP and the yoke immediately turned right. Same with the left. But in the air, not so much. I had to make huge heading bug moves to get it to even turn 10 degrees.
 
Not familiar with autopilots, but that sounds like it could be a servo issue. Wind resistance on the aileron and it doesn't want to turn in the last 10 degrees of the course. Remove the resistance and it is fine. Does the CIIIb normally decrease the roll rate the last 10 degrees?
 
EdFred said:
sounds like it could be a servo issue
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Yessir, I believe you're onto it. More specifically an under-torqued servo clutch.

OP, your shop should be able to check to make sure the roll servo is properly working and properly set by measuring the torque at the capstan and adjusting as req'd.

It's not very likely for your GAD to take a dive without you seeing lots of colorful Garmin warnings strewn about your various equipment.

Question: what is your autopilot using for heading source? Do you have a GMU? Or is it a legacy unit like a KMT-112 or whatever?
 
Der Fliegermeister said:
Yessir, I believe you're onto it. More specifically an under-torqued servo clutch.

OP, your shop should be able to check to make sure the roll servo is properly working and properly set by measuring the torque at the capstan and adjusting as req'd.

It's not very likely for your GAD to take a dive without you seeing lots of colorful Garmin warnings strewn about your various equipment.

Question: what is your autopilot using for heading source? Do you have a GMU? Or is it a legacy unit like a KMT-112 or whatever?
Click to expand...
GMU11 provides heading source from the G5 HSI.
 
Could be needing a roll gain adjustment. Lots of times the old amplifiers just need tweaking. But also check all the connections (plugs) for corrosion, backed-off or broken pins, etc.

I know you probably don't want to hear this but it's worth considering and planning for if you're going to keep the bird: it may be nearly time for a new autopilot. Garmin's kicks a** and the STec 3100 is good.
 
Der Fliegermeister said:
Could be needing a roll gain adjustment. Lots of times the old amplifiers just need tweaking. But also check all the connections (plugs) for corrosion, backed-off or broken pins, etc.

I know you probably don't want to hear this but it's worth considering and planning for if you're going to keep the bird: it may be nearly time for a new autopilot. Garmin's kicks a** and the STec 3100 is good.
Click to expand...
See post #5. ;)

GFC500 and a second G5 are on the list but there has been so much cash outflow in my family lately I'm not up for it. That said, I do not want to be doing the type of flying I do with IFR now added on top without an autopilot.
 
I'd say most likely it's the roll servo. The fact that you're seeing a difference in roll response on the ground with no air load vs. in the air suggests the correct voltage is being delivered and interpreted by the autopilot but the roll servo is unable to deliver the correct input.

I just had both of my servos overhauled... not cheap.
 
I wouldn't be so fast to give up on the Century IIIC unless you've got major problems with the unit. Even a GFC500 (which I'd be really excited about) is going to put you in the $20k range for fully installed and out the door at a quality shop. You can do a field overhaul of a Century IIIC for a quarter of that price and get a heck of a nice flying autopilot. Obviously this is a case-by-case consideration, but I elected to go the "value" route here and I haven't regretted it. The airplane flies like it's on rails now.
 
Ryan F. said:
I wouldn't be so fast to give up on the Century IIIC unless you've got major problems with the unit. Even a GFC500 (which I'd be really excited about) is going to put you in the $20k range for fully installed and out the door at a quality shop. You can do a field overhaul of a Century IIIC for a quarter of that price and get a heck of a nice flying autopilot. Obviously this is a case-by-case consideration, but I elected to go the "value" route here and I haven't regretted it. The airplane flies like it's on rails now.
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I actually have a spare roll servo. Not giving up easy.
 
NealRomeoGolf said:
See post #5. ;)

GFC500 and a second G5 are on the list but there has been so much cash outflow in my family lately I'm not up for it. That said, I do not want to be doing the type of flying I do with IFR now added on top without an autopilot.
Click to expand...
I'm sorry, I missed that! Understood:oops:
 
Update on this: the issue ended up being intermittent, which makes troubleshooting worse. I would fly one leg with no autopilot and then the next leg it would work. I took the plane up to Mayday Avionics in Michigan and they tried to replicate the issue (the AP worked the whole way up there) and they couldn't. So they cleaned all the connectors and tested a bunch of stuff. I've flown 12 hours since and it has worked fine the whole time.

While we were in there, I asked them to look at my disconnected glideslope coupler. They tested it and said it worked but they would need a wiring diagram to interface it back to the 530W or would have to spend the time to reverse engineer it. I guess I was surprised by that since there have to be tons of 530s connected to these types of autopilots. I've googled wiring diagrams 530 glideslope coupler and came up empty. Anyone have wiring info to glideslope couplers for the GNS series?
 
Ryan F. said:
***DELETIA***
Even a GFC500 (which I'd be really excited about) is going to put you in the $20k range for fully installed and out the door at a quality shop.
***DELETIA***
Click to expand...

With all the bells and whistles (roll/pitch/autotrim/no yaw), dual G5s, interfacing to existing 430w/530W/etc, OAT, yoke switches, and the 'oh, by the way..." closer to 25K.

it is an exciting AP. Still learning the buttonology on mine...but extremely pleased. Admittedly, my experience is with KAPs and various S-Tecs, but, this system, at this price point, is a game changer for the better for the lower end of the GA world. And when you throw in envelope protection and the big blue button...hard to argue.

Just my $.02, no financial interest, etc.
 
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