My KFC150 Autopilot (with Altitude Pre-select) does not couple to an LPV or LNAV+V Approach. Yet it works fine on an ILS all the way down to 200ft agl.
The Avidyne IFD550 shows no errors during either Approach. The indications on the HSI (KI525) are correct in both Approaches. Any suggestions as to what might be amiss.
I have now tried this on 3 different LPV Approaches and 1 LNAV+V Approach and every time the Autopliot does not couple and yet it works flawlessly on an ILS.
My suspicion is that there is something not quite right in the IFD settings, but what.
The big Q is whether it has ever worked?
@garryIAE and @wigglyamp might have ideas but I would start by looking at the ILS ENERGISE wire. These autopilots (including my KFC225) pre-date GPS approaches with vertical guidance (LPV or +V) and require some hacks to make it work. @NCyankee posted the detail of this procedure somewhere here, years ago, for the KFC225 (some buttons have to be pressed twice, IIRC).
I agree with Peters comments, I’d look at the GPS Approach output from the IFD and check to see if that does interface with the Autopilot, whoever installed the IFD should be able to confirm that.
Peter wrote:
The big Q is whether it has ever worked?
Probably not.
It’s only recently I have been trying out GNSS Approaches as I have been in France, where there is plenty of them.
The most common error on a GNS530W is for the installer to use ILS Energize output P5006 Pin 29 instead of ILS/GPS Approach P5001 Pin 14. The latter is supposed to be wired to the ILS Energize input of the autopilot. If the former is wired to the autopilot, then ILS will work great, but GPS vertical guidance will not. I have seen this dozens of times, usually when the original installation was upgraded from a GNS530 to a GNS530W. Since an IFD550 is pin compatible with the GNS530W, I would guess this is your issue. The reason this happens is that experienced installers don’t use the wiring diagrams and just know (incorrectly) that “ILS Energize Out” from the navigator is hooked to “ILS energize In” on the the autopilot. They are just too experienced to need to RTFM.
Well done NCyankee.
That’s a great description of the issue.
I think you are probably right. I have just been reading the Installation Manual and it does show the connections for the KFC150. I’ll get the installation checked.
Thanks for the info, probably good to tell my avionics shop, I’ll get a GNS530 W upgrade and I have a KFC150…
Anyone using the Gama Aviation EASA LPV STC to upgrade their GNS will find this issue is fully described to ensure the AP coupling works correctly.
In what circumstances is that STC required, and how much is it?
Rather than just referencing a commercial product, can the information be found somewhere, or posted here, so that the OP can find it helpful to sort out his problem?
NCYankee wrote:
The most common error on a GNS530W is for the installer to use ILS Energize output P5006 Pin 29 instead of ILS/GPS Approach P5001 Pin 14.
You were absolutely right. It took 2 days of removing radio’s and racks from the centre stack and then removing all the tie wraps, to be able to chase through the wires at the back of the radio’s. In the most inaccessible place, of course.
Both Pin 29 and Pin 14 had been connected for some reason, although after several hours of removing tie wraps and connectors it was finally established that Pin 14 was not connected to anything.
I flew ILS, LPV and LNAV+V approaches at the weekend and everything works properly, now that Pin 14 is correctly connected to the Autopilot.
Thanks for your help.
