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Autopilot replacement

Autopilot century 21 avionics upgrades M20J

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#1 AlanA

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Posted 12 September 2012 - 03:24 AM

The Century 21 autopilot in my M20J no longer holds a heading. I am thinking about replacing it with a new or refurbished autopilot rather than attempt to have it fixed only to have it still not work. Any suggestions about what to replace it with? If you have installed one about how much did it cost? The Century 21 is a single axis autopilot. I'm thinking about replacing it with another single axis autopilot because the two axis is so expensive. Do you think I will be disappointed if I only do single axis? Can I easily upgrade later to add the other axis?

#2 jetdriven

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Posted 12 September 2012 - 03:45 AM

I'd advise getting it repaired. An altitude hold S-TEC autopilot is in the 15-20K range, and there are many unhappy owners of those, too.

It may be the DG that is the problem. Try Autopilots Central in Tulsa. They are highly regarded.
Byron
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#3 aerobat95

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Posted 12 September 2012 - 04:09 AM

When I was looking at autopilots I was quoted 16K for the S-Tec autopilot w/ altitude hold. I think they are out of their minds. I know we cant put them in our certified planes but you get a whole lot more for a whole lot less with some of the experimental autopilots. If my budget would have allowed I would have went with a RV-10.

#4 AmigOne

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Posted 12 September 2012 - 04:24 AM

I was going to make exactly the same recommendation adding that another excellent and reasonable shop (price wise) is the avionics shop in Leesburg, Fl. One of only a handful of shops in the USA that would repair a 1973 a/p in a Cessna 210 I was ferrying to South America. They did it in a couple of days and they said that all it needed was a thorough cleaning of contacts, plugs, some adjustments etc. They could have told us that they had replaced expensive parts and we would have believed them. The bill was $500 plus dollars and it is still working perfectly a year later.
As to the specific issue of not holding a heading I had a similar issue in my 201 (KFC200) and after a bunch of money, replacing the computer board, etc, by a shop in Manassas with no improvement, I took it to another shop and they discovered that the torque value in the aileron servo was way off!!! they set right and voila!! problem solved.

#5 Skybrd

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Posted 12 September 2012 - 04:27 AM

I had problems with mine and it turned out to be a dirty electrical connector on the rear of the DG. I have the Century III AP. You might want to clean all your AP connectors. I also noticed my trim switch sometimes fouls up activating the AP.


#6 AmigOne

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Posted 12 September 2012 - 04:32 AM

Curiously how we have similar tastes. I looked for a long time for an RV 7 but I did not find one that I liked and could afford. So I settled for my M20C but w/o an autopilot. I'd be crazy to dump that kind of money to add an a/p. I can fly IFR with my wing leveler, it is not the same but in a way it keeps me sharp. And when I say IFR I mean easier IFR, I never have to be anywhere. I still check the listings for somebody wanting to trade and RV for a Mooney but I don't think there are any out there. By the way, I love my Mooney M20C, it is my third Mooney.

#7 jetdriven

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Posted 12 September 2012 - 04:35 AM

We have the Century IIB with the S-TEC 30ALT altitude hold. We just flew from Sedona to Houston today and it took 6:30. All of the cruise was hands off. Meaning I slept while wife flew.

We bought it that way, the 30ALT is like 9K by itself. Its totally worth it.
Byron
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#8 Vref

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Posted 12 September 2012 - 07:41 AM

The Century 21 autopilot in my M20J no longer holds a heading. I am thinking about replacing it with a new or refurbished autopilot rather than attempt to have it fixed only to have it still not work. Any suggestions about what to replace it with? If you have installed one about how much did it cost? The Century 21 is a single axis autopilot. I'm thinking about replacing it with another single axis autopilot because the two axis is so expensive. Do you think I will be disappointed if I only do single axis? Can I easily upgrade later to add the other axis?


Having Altitude hold is big+ when flying long distances. What I do sometimes is selecting altitude hold and my oldest son 8 years can steer the aircraft ....the STEC30 is good add on I think

#9 Steve Dawson

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Posted 12 September 2012 - 10:28 AM

I had the same problem with my Century IIB and our local avionics shop (Brant Aero) repaired some contacts and confirmed other connections to make the autopilot work again for $400.00. Sarasota offered a Stec 30 w/ altitude hold installed for $13,500 or the altidude only for $7,500.00 and if my memory is right AutoPilot Central were a little lower. My suggestion would be to check the CIIB first before spending significantly more.

#10 N601RX

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Posted 12 September 2012 - 11:43 AM

Post like these make me happy to say I have a Brittain.

#11 Piloto

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Posted 12 September 2012 - 01:20 PM

I have a Century 31 and like many have posted here I had the same contacts problem. Just disconnect the A/P connector going to the DG and spray contact cleaner on the contacts. Also pull out the computer from its tray and spray contact cleaner on the contacts. Try this first before deciding on spending money. Check the aileron servo clutch by engaging the A/P on the ground and try to turn the yoke by hand. It should require significant force to turn. If not you may have a worn out servo clutch that either requires to tighten the servo shaft nut or a new clutch.

Altitude hold is nice to have, specially when you need to relief yourself.

José

#12 AlanA

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Posted 12 September 2012 - 08:56 PM

Thanks for all the great ideas! I really don't want to spend a fortune on a new AP so I think I will contact one of the shops mentioned and see what they say about fixing it.

I tested it in flight today. When I press the test button all the lights turn on so it appears that at least the computer is recognizing input from the heading bug and VOR. But there is no resistance at all to turning the yoke. Also when I set the heading bug for turn nothing happens.

Does this indicate then a probable servo problem?

#13 jetdriven

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Posted 12 September 2012 - 09:02 PM

Most of the problems with Century autopilots are related to servos, output transistors which drive the servos, and the connectors. The servos get old, brushes wear, bearings get dirty, the clutches stick, and the breakout (startup) voltage rises above 2V. Then the autopilot wing rocks because the servo delays on startup and then overshoots constantly. Eventually the excessive amp draw blows the output transistors on Century autopilots and it quits working. That, and the intermittent connections in the split pin connectors.

Another thing is the roll pickoffs in the AI and DG. if they send a bad signal it screws with the autopilot. Another thing which causes wing rocks is a badly rigged plane. If the ball is not centered in level flight, the autopilot tries to hold wings level. It then turns in a skid. Then the autopilot banks to correct heading, now its not wings level. It can't have both, so it wing rocks. rigging the rudder cures that.

Our Century IIB had all this done before we bought it and it works really well.

If it were my plane I would measure the startup voltage. But the easiest is to pull the autopilot head unit and the servo and send them to Autopilots Central.
Byron
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#14 jnisley

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Posted 13 September 2012 - 01:09 AM

Four years ago we installed a STEC30 with alt-hold and GPSS steer for around $14,000 if I recall correctly. With the GPSS coupled with the 430W it flies procedure turns, holds and GPS approaches perfectly, it does however seem a little weak when tracking a localizer needle in windy conditions, perhaps there's an adjustment that I'm not aware of. I like the idea of it being independent of the attitude indicator which is vacuum powered.
John

#15 AlanA

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Posted 14 September 2012 - 04:19 AM

I contacted Autopilots Central in Tusla as some of you suggested. I asked if there was something I could do first to localize the problem before sending the AP in. Barry there gave me some great instructions which I will try first. If I need to send it in I will definitely send it to them. I copied his email. I thought it might be of interest to anyone else having similar issues with their AP.

Alan, Go to the roll servo. Unplug the connector. There are four pins, A, B, C & D. Pins A & B are the engage solenoid. Pin A is ground and pin B is 12 volts or battery voltage. If you put your volt meter on Pins A & B at the same time, you should read approximately 12 volts DC with the autopilot engaged. If no voltage you have a bad controller. If you do have 12 volts, bad servo. Next, go to pins C & D. This is motor drive. If you engage the autopilot in the heading mode, while your volt meter is across pins C & D, if you move the heading bug, you should get varying voltages of 0 - 10 volts DC. This will go positive and negative according to witch side of the lubber line the heading bug is on. If you have no voltage, bad controller, voltage and no motor drive, bad servo.
Good Luck
Barry
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#16 N201MKTurbo

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Posted 27 September 2012 - 10:56 PM

It is easier then stated above to test the autopilot.

With the airplane on the ground, engine off, master on.

To test the servo clutch, just turn on the left switch, you should hear the clutch engage and feel the autopilot restrict the movement of the ailerons.

Test the servo by rotating the roll knob all the way to the left, the yoke should rotate slowly to the left, then rotate the roll knob all the way to the right, the yoke should rotate to the right.

Do this before you do the above tests. If the clutch doesn't work, try wiggling the connector on the disconnect relay (on my 77 J it is way up on the firewall behind the vacuum manifold) to see if it causes the clutch to engage intermittently, if so fix the connector. Try the disconnect switch on the yoke, you should hear the disconnect relay click when you actuate the switch.

Does your electric trim work? The electric trim and the autopilot clutch both go through the disconnect relay.

I have had the disconnect relay fail, the connector on the disconnect relay box fail, the connector at the servo fail, and a broken wire in the cable that goes to the servo. I was able to fix them all for no money, just my time. My autopilot currently works perfect (knock on wood)
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#17 rbs4159

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Posted 24 October 2012 - 06:05 PM

Do any of you with the fancy autopilots have the parts to add autopilot to my beautiful Brittain PC system? I agree with one of the posts that feels dumping $15K or so into a 1968 C model doesn't make sense, but I would add the Brittain A/P parts if I could find them.

#18 KSMooniac

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Posted 24 October 2012 - 07:55 PM

You should check in with Brittain themselves b/c they acquire and service components as they can, and sell them to folks on a list according to what I've read. You could also try the salvage route and ebay to find components that could be sent to Brittain for service/overhaul. I think it is well worth the effort to scrounge up the parts and get the Brittain system serviced and functional...

It is a shame that TruTrak has no interest in pursuing STCs for us, and STEC acts like the near-monopoly they are. I'm happy my plane came with an STEC, but sure wouldn't install one today due to their pricing and customer (dis)service policies. Hopefully the Avidyne DFC90 and Aspen combo will be available for Mooneys soon.
Scott
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#19 N601RX

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Posted 25 October 2012 - 03:26 PM

Unfortunately their waiting list is a couple of years long. Looks like there is a good demand for cheap autopilots.

#20 Marauder

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Posted 29 October 2012 - 05:19 PM

Do any of you with the fancy autopilots have the parts to add autopilot to my beautiful Brittain PC system? I agree with one of the posts that feels dumping $15K or so into a 1968 C model doesn't make sense, but I would add the Brittain A/P parts if I could find them.


You can have everything I took out of mine. PM with your contact information and I will send you a list of what I have.





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