I’m looking for an installation or maintenance manual (or other relevant technical documentation) for a Piper Autocontrol IIIB autopilot. This is the same as a Century IIB, but there have been various hardware revisions. The important thing for me is that the documentation relates to a radio coupler with p/n 1C388-2.
(The service manual in Peter’s repository doesn’t mention the 1C388-2.)
I tried a contact in the US but got no reply.
I would try some ancient avionics repair shed; they tend to have shelves full of old manuals. I know of a local one but most of the time there is nobody there and the guy running it doesn’t reply to messages.
I have the service manual as a .pdf
I’ll pm you. There is also a fantastic online blog – David Crocker’s Solutions Blog – he is an ex flyer who is into 3D printing but has lots of useful stuff on these. It’s pre-Apollo technology but mine has not skipped a beat in 8 years of ownership apart from a few dodgy oxidised pins on the connector plugs
Since I have the same, curious what you’re up to @airborne_again
Snoopy wrote:
Since I have the same, curious what you’re up to @airborne_again
We’re planning an avionics upgrade on a PA28 while keeping (for the moment) the existing A/P. Our local avionics guy is really great but he also very much wants to throw away all old stuff so he’s not overly keen on doing the necessary research to interface the Autocontrol IIIB with the new avionics. :-)
Airborne_Again wrote:
(The service manual in Peter’s repository doesn’t mention the 1C388-2.)
It turned out that Peter’s pdf with the service manual had a schematic of the 1C388-2 at the end so I have what I need! That schematic is not actually part of the service manual – someone just throw it in.
The Avionics people I used interfaced the Garmin G5’s to my Autocontrol IIIB. Looking back through the logbooks it looks like it hasn’t broken down in the last 15 years or so. Old technology is sometimes built better than the new stuff!
How can the Piper Autocontrol IIIb be interfaced with the G5? GPSS and HDG mode?
Any analog autopilot can be driven from any modern avionics if you can generate the L+V signals. For L you can do it by faking a heading bug source; that is what the roll steering converters (DAC100?) do.
I think a lot of these old autopilots are actually very good. They are being chucked out because they are full of analog cicuitry, which uses electrolytic capacitors for time constants (these dry out) and a lot of crappy trimpots which go noisy, and almost nobody in avionics knows any electronics so almost nobody can repair them, and most of those who can are in the US, and most of them will retire next year and won’t be replaced 
If you could find an electronics boffin and work off the books you could keep a lot of stuff going.
Snoopy wrote:
How can the Piper Autocontrol IIIb be interfaced with the G5? GPSS and HDG mode?
I don’t know about the G5 but it certainly works exactly that way with the Aspens and their analogue coupler they sell for this purpose. I think the G5 works similar. I’ve tried both the GPSS implementation of Aspen (which indeed works via the heading bug) and the direct solution and there is virtually no difference.
I’ve flown several planes in the distant past which had Piper Ap’s and I have to say they all worked fine. One of the guys I helped buy an airplane had one which was labled “inop” when he bought it but one of the AP gurus at his avionics shop sorted him out in less than one hour work time.
Airborne_Again wrote:
Our local avionics guy is really great but he also very much wants to throw away all old stuff so he’s not overly keen on doing the necessary research to interface the Autocontrol IIIB with the new avionics. :-)
And in the process sell you $$$$ worth of newer but not necessarily better equipment.
In principle it should not be a big deal. Your GPSS capable GPS needs to be connected to the EFIS and the EFIS needs it’s heading system connected to the EFIS. (At least that is what the ASPEN solution does. The NAV part needs to be wired to the radio coupler. That is all that is to it.
I’ve seen quite a few Autocontrol 3 systems which are augmented by a pitch channel Stec 60 PSS. With a radio coupler this allows full coupled ILS approaches amongst other things and quite possibly also LPV via the EFIS.
