Century IIb

[Bartman]

10 years ago at purchase my Century IIb with STEC add-on altitude hold worked, but it flew like a drunk and was very in comfortable. After a few tweaks on the control box adjustment screws we got the AP working great in heading mode. It used to hunt about 10 deg mostly to the right but it has been dead on for years now, but the Alt hold would search up and down in smooth air but was great with just a little turbulence. With the help of some advice from Mooneyspace I got that figured out and if it is searching in pitch then just give it a little up or down trim such that it's not perfectly trimmed hands off if disengaged. It now flies straight and true in both pitch and roll and it is a joy to fly in smooth air. The thing is I had never tried the Omni setting until just a few months ago. I've been using that recently on approaches and it is awesome to say the least. Just get established inbound, switch to Omni and turn off the Alt Hold and I can manage descent with power and trim.

I know I'm late to the party, but I just wanted to brag on my 40 year old original equipment Century IIb autopilot !

[N201MKTurbo]

2 hours ago, Bartman said:

I know I'm late to the party, but I just wanted to brag on my 40 year old original equipment Century IIb autopilot !

Mine works great too. Especially sense I got my IDF550. it draws amazingly straight lines on Flight Aware. I should be getting my GAD29B any day now I'm anxious to see how that works with the CIIB.

[EricJ]

I enjoyed my forty-year old Century III for a couple of weeks, and even figured out that although the alt-hold didn't work, the pitch hold did, even though my electric trim is inop.

Until it all didn't.   Now it just wants to turn hard left all the time and the pitch control is dead.   I haven't had a chance to start debugging it yet, but I *really* like having those functions working.

[jetdriven]

Omni is a very low sensitivity.  LOC is the highest sensitivity and corrects the fastest, such as on an approach. 

[N201MKTurbo]

11 minutes ago, jetdriven said:

Omni is a very low sensitivity.  LOC is the highest sensitivity and corrects the fastest, such as on an approach. 

I've found NAV works best for everything. Even approaches. I'm pretty sure the GPS changes sensitivity automatically.

[Bartman]

48 minutes ago, jetdriven said:

Omni is a very low sensitivity.  LOC is the highest sensitivity and corrects the fastest, such as on an approach. 

I don't know maybe it's just me, but HDG enroute and OMNI on approach is working great right now.  Been a while since I tried the LOC and even that was before we got it dialed in smooth on HDG, but it was twitchy and too sensitive when I did but maybe that was because it needed adjustment.  I'll do some more experimentation but I'm happy with HDG enroute and OMNI on approach. NAV setting doesn't  do so well either enroute or on approach it's back and forth and searching just a few degrees. 

Anyway, I'm happy with how this 40 year old AP is working. 

[INA201]

I've got a 750 and G5 with GPSS.  While tracking a course the IIB will kind of sway back and forth along the course line.  I am satisfied with it's performance but it seems like other folks have had better luck with more dead on course following than mine vs this lightly back and forth movement.  Does anyone know the best way to tighten this up or where to start?  Thanks in advance.

[jetdriven]

There are 4 adjustment screws behind the panel to adjust this out. 

[N201MKTurbo]

The G5 has a GPSS sensitivity setting. 

I reduced mine and it flew much better. Next time I’m out at the airport I’ll see what value I ended up with.

Edited October 16, 2018 by N201MKTurbo

[INA201]

This is what I found on the 2b for adjustments I think.  Does this look like a good place to begin or should I start simple with the G5? 

[N201MKTurbo]

If it holds a heading without hunting in heading mode (GPSS off), I would start with the G5. Otherwise start by adjusting the gain until it will fly straight at cruise speed without hunting.

The gain will cause it to wander back and forth if it is too low because it will be too slow to correct and if it is too high because it will over correct. If I adjust it so it works good in cruise it will be a bit unstable in climb and visa versa. I choose to make it work best in cruise and accept the instability in climb. It isn't that bad and you can stop it with a little help on the yoke.

 

BTW When I say gain I'm referring to the roll threshold adjustment.

Edited October 16, 2018 by N201MKTurbo

[jetdriven]

2 hours ago, INA201 said:

This is what I found on the 2b for adjustments I think.  Does this look like a good place to begin or should I start simple with the G5? 

Start with that. The G5 GPSS gain can be evaluated by whether it consistently overshoots or undershoots a course change. Build a flight plan that changes 90-120 degrees.  Go fly it in GPSS Mode and note if it turns inside or outside of the new course line. Often the cIIB won’t bank enough to fly the anticipated turn and you can’t help that. But note the turn inside or outside the new course and adjust gain based on that.  But hunting, wing rocks, or oscillations are an autopilot or attitude gyro issue. 

Edited October 16, 2018 by jetdriven

[katzhome]

I know I'm reviving an old thread here, but seeing if anyone out there has the Roll Servo part number used with the Century IIB autopilot.  My logs state "Century IIB, drawing 830123" for installation.  I will be seeing if I can recover the solenoid function, but if it isn't the control head (I have a spare), I would have to replace the Servo...the Century manuals have lots of different part numbers. 

My best estimate is a 1C363-1-183R, which the Cherokee's use, but that is mounted under the seat, not out in the wing.  I'll be opening up the panel out there soon to take a look, but if anyone has the number immediately at hand, I would be very appreciative!

[EricJ]

52 minutes ago, katzhome said:

I know I'm reviving an old thread here, but seeing if anyone out there has the Roll Servo part number used with the Century IIB autopilot.  My logs state "Century IIB, drawing 830123" for installation.  I will be seeing if I can recover the solenoid function, but if it isn't the control head (I have a spare), I would have to replace the Servo...the Century manuals have lots of different part numbers. 

My best estimate is a 1C363-1-183R, which the Cherokee's use, but that is mounted under the seat, not out in the wing.  I'll be opening up the panel out there soon to take a look, but if anyone has the number immediately at hand, I would be very appreciative!

My Century III (nearly the same thing) is inop but still installed, and won't be coming back because I deleted the vacuum system.   At some point I'll be taking all that stuff out, and the servos were still fully functional (it'd pass all the ground tests).   The next time I think of it I'll grab the pn for the roll servo.

[katzhome]

1 hour ago, EricJ said:

My Century III (nearly the same thing) is inop but still installed, and won't be coming back because I deleted the vacuum system.   At some point I'll be taking all that stuff out, and the servos were still fully functional (it'd pass all the ground tests).   The next time I think of it I'll grab the pn for the roll servo.

Thanks @EricJ!  Much appreciated!  I'm also going to try to get a look, but most of our visits to the plane lately have been to fly.  With my (limited) avionics upgrade coming, I want to see if I can get the IIB back operational.

[N201MKTurbo]

3 hours ago, katzhome said:

I know I'm reviving an old thread here, but seeing if anyone out there has the Roll Servo part number used with the Century IIB autopilot.  My logs state "Century IIB, drawing 830123" for installation.  I will be seeing if I can recover the solenoid function, but if it isn't the control head (I have a spare), I would have to replace the Servo...the Century manuals have lots of different part numbers. 

My best estimate is a 1C363-1-183R, which the Cherokee's use, but that is mounted under the seat, not out in the wing.  I'll be opening up the panel out there soon to take a look, but if anyone has the number immediately at hand, I would be very appreciative!

Should be easy to troubleshoot. There are only 4 wires going to the servo. Two are for the servo motor and the other two are for the clutch solenoid. I would expect a wiring issue before a failure of the servo assembly.

[katzhome]

1 hour ago, N201MKTurbo said:

Should be easy to troubleshoot. There are only 4 wires going to the servo. Two are for the servo motor and the other two are for the clutch solenoid. I would expect a wiring issue before a failure of the servo assembly.

Hi @N201MKTurbo, that is what I'm hoping.  I've read some of the troubleshooting steps in various forums, it is just a matter of getting down to the plane to work on it for a few hours versus getting my time or my son's time flying in.

 

I expect it is the drive transistors for the solenoid or wiring like you said.  Luckily I do have a backup control head that should be fully operational, but I don't want to try using it until I've made sure I don't blow the transistors due to a bad solenoid. 

[OR75]

1C508-1-523R is the roll servo part number