Avidyne IFD with autopilot switch?

[EricJ]

Talked to Avidyne and got a fair amount of useful information that was interesting and helpful.   The suggestions:

1.  Wire an annunciator in plain sight of the two indicators (HSI/CDI) to show which is driving the autopilot.   This would require a fair amount of wiring, relays, etc.

2.  Some King installation manuals showed the switch in place, and that documentation might be able to be used if it was relevant to the installation (the avionics being replaced is the original King stack).

3.  The Nav1/Nav2 switch was probably original equipment from the factory, so a Mooney diagram showing the switch installation could potentially be used as well.

The above may still require sign-off from the local fed, but the documentation trail could be used to support the case.   It is true that the issue comes from the wiring diagrams not showing the switch, and apparently that's true for all sorts of equipment STCs so the switch is not an unusual stumbling block. 

So this isn't specifically an Avidyne issue.   The same, exact issue exists for the Garmin units as well.   This is also relevant because the IFDs are slide-in replacements for the GNS units.

We may have a compromise that I'm going to propose to the installer and go from there.    Things are seldom as simple as they could be. 

[carusoam]

Some BK original from the factory are so integrated to together, the switch probably came from BK as well...

AI, HSI, Nav1, GPS, AP, and a couple of annunciators and servos are all connected together...

And by extension the nav devices that have aural IDs all come through the BK audio panel...

The nav1 /GPS switch is quite capable...  Mega pole, single throw... 

Early 90s when the GPS was a single box like an ADF... before the Big G multi nav com was standard...

Best regards,

-a-

[Piloto]

My M20J had the NAV1/NAV2 switch for the autopilot.  After I installed the G530 I removed the switch/relay because of previous problems found.  When you are switching from NAV sources you switching eight wires through a multipole relay that is controlled by the NAV switch. In addition you have added connectors. Because of the very low voltage used (less than 0.150 Volts) any contact resistance will create deviation changes on the GS and LOC signals.

José

[carusoam]

That makes my switch a single throw / Octapole switch... 

Does that include turning on the blue light when the GPS is the active source? Or is that a ninth pole?

Best regards,

-a-

[Piloto]

Most autopilot don't care about the GPS blue light since there was no GPS in the past. The autopilot validate the deviation signal using the flag signal voltage, which is also switched for NAV source. And if the HSI is also switched you also have the synchro 6 wires to be switched.

José

Edited May 14, 2018 by Piloto

[Cruiser]

This is a failure on the avionics shop. They are demanding you remove something that has been installed and used previously. 

Find out what they claim is needed in order for it to remain. 

do you have one of these? http://www.katerno.com/detail/s/273505/p/RS12-020/Gps/loran-Data-Switch/20k---Rs12-020

I can't believe they would not allow it to remain.