GFC 500 dropping NAV coupling with GPS>VLOC switch

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   I don't know if this is reported elsewhere on this forum, but I discovered a glitch in my new GFC 500 operation with dual G5s and IFD 540 today. I was able to replicate this three times today, so I feel it is a real issue. I also believe it happened during a series of coupled approaches a week ago when I was having problems with NAV tracking on some of the approaches (the ILS and VOR ones). My system tracks and executes all GPS approaches attempted to date - LPV, LNAV+V, LNAV).
Today I took a video of this so I have the details of what happened. While letting the autopilot fly (via GPS mode) to a VOR and then fly from that VOR on a VOR-A approach (ACO, KPOV), the GFC 500 accurately followed what the IFD wanted. This included navigating to the VOR, making a rather tight turn to follow the procedure turn outbound (on one of the trials, I intentionally set this up to see what navigator and autopilot would do) and then do the approach. As would be expected, the GPS>VLOC appeared on the IFD. As the instant that the GPS>VLOC changed to VLOC and the HSI changed from magenta CDI to green CDI, the G5 showed a yellow blinking GPS to the left of a ROL indicator, showing that the GPS nav signal had been lost. At this point, the NAV indicator on the autopilot also dropped off, leaving it in the ROLL mode as the green CDI drifted away from centered. 

I pressed the NAV button and re-coupled in the NAV mode, but the autopilot didn't change heading to recapture the CDI. Instead, it stayed on the heading it was when it went into ROL mode above. I switched to HDG mode, set an intercept heading for the 'desired track' of the plotted course of the VOR approach, The autopilot dutifully followed the heading to intercept the track, switched to NAV mode by itself, and flew the remainder of the approach as it should.

In reflection, I believe this issue also happened on the attempts to fly two coupled ILS approaches in my earlier practice session - when the GPS>VLOC auto sequences to VLOC, the NAV function of the GFC drops, leaving it in the ROL mode and allowing the aircraft to drift off course. Of course, during these ILS approaches, the GFC failed to capture and track the GS.

I will double-check this in the coming days.

Anyone else experience this? I'll also send this to TJ along with the video. I'll trim the video and see if I can figure out how to post it or at least a link for y'all to view.

 https://youtu.be/hjxg_NOq3mk

Edited by compasst - 26 Jul 2020 at 10:49am