DFC90: Activating the APPR button on the ILS

HI Roger,

I think I may need some more info.  You can elect to either answer here so that others may see the interaction or send me a direct email at sjacobson@avidyne.com.

As for the extra information (I apologize for any sophomoric sounding questions):

1.  I see you have the PFD in VLOC mode. Can you confirm that Primary Nav was indeed tuned to the proper localizer frequency?
2.  Can you confirm you had the proper inbound course set in the Primary Nav datablock?
3.  What is your typical technique on Vectors-To-Final approaches?  My normal technique is to be in HDG mode and then when either cleared for the approach by ATC or when established on final, I arm NAV APPR by pressing the HDG & NAV (or APPR) buttons on the autopilot at the same time.  Pressing either HDG-NAV or HDG-APPR will work and the other one (APPR or NAV) "comes along for the ride" but my habit is to press HDG NAV.  At that point, I should see HDG in green and NAV and APPR lit up in blue.    It is possible that the capture criteria are immediately satisfied so it might be a near immediate transition to no HDG and just solid green NAV and APPR.
4. Do you ever have NAV lit up in green on the DFC control panel and in the PFD annunciator strip?


To answer your last question about conditions that may prevent activation of APPR, there are a few.  In general terms, you need to have the proper freq and selected course dialed in, the radio needs to see the VHF signal, and you've got to be pretty closely aligned with the final approach course and inside 18nm.