Final leg cleared when approach selected

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   Would someone be able to enlighten me as to why the final leg disappears when you select an approach from far out? 
For example, if I select KRYW as the departure airport, add the fix GOBBY and then destination as KHDO.  While flying between KRYW and GOBBY, I select the Proc RNAV 17L (but do not activate), the final leg from GOBBY to KHO gets wiped out.   

This caught me out yesterday as I was flying a similar route and got to a fix only to realize that there was no routing set after that. 

TIA!

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Speedbird1 Members Profile Send Private Message Find Members Posts Add to Buddy List Groupie Joined: 16 Mar 2020 Location: New Braunfels Status: Offline Points: 66	Post Options Post Reply Quote Speedbird1 Report Post Thanks(0) Quote Reply Topic: Final leg cleared when approach selected Posted: 08 Mar 2021 at 9:22am
	Would someone be able to enlighten me as to why the final leg disappears when you select an approach from far out? For example, if I select KRYW as the departure airport, add the fix GOBBY and then destination as KHDO. While flying between KRYW and GOBBY, I select the Proc RNAV 17L (but do not activate), the final leg from GOBBY to KHO gets wiped out. This caught me out yesterday as I was flying a similar route and got to a fix only to realize that there was no routing set after that. TIA!

dmtidler Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 12 Feb 2016 Location: USA Status: Offline Points: 628	Post Options Post Reply Quote dmtidler Report Post Thanks(0) Quote Reply Posted: 08 Mar 2021 at 11:55am
	This IFD behavior was discussed in a few threads concerning flight plan gaps a while back. I don't know Avidyne's why's behind this logic. Essentially: if the procedure airport is not the IFD active waypoint when an approach procedure to that airport is selected, the IFD effectively moves the procedure airport to its appropriate place in the selected approach procedure creating a gap between the waypoint prior to the procedure airport and the first fix for the approach. This is the scenario you described. After this occurs and if desirable, the procedure airport can be added as a waypoint prior to the gap that was created by selecting the approach procedure. If the procedure airport is the IFD active waypoint when the approach procedure to that airport is selected, then procedure airport remains the IFD active waypoint and a second instance of the procedure airport occurs at the appropriate place in the selected approach procedure. Had you waited until after GOBBY to select the RNAV 17L approach, this would have been the scenario you would have been in. FWIW - the "Activate Approach" LSK (only available if the active IFD waypoint is followed by a gap before an approach) also has different behaviors depending on the situation: If a VTF approach is selected, The Activate Approach LSK performs the same operation as the Activate VTF LSK or selecting the FAF and using the Activate Leg LSK. If a non-VTF approach is selected and the IFD active waypoint is the procedure airport, selecting Activate Approach LSK performs the same operation as performing a direct-to the IAF from you present position. If a non-VTF approach is selected and the IFD active waypoint is not the procedure airport, selecting the Activate Approach LSK eliminates the gap by connecting the active waypoint and the IAF. Edited by dmtidler - 08 Mar 2021 at 3:11pm

Speedbird1 Members Profile Send Private Message Find Members Posts Add to Buddy List Groupie Joined: 16 Mar 2020 Location: New Braunfels Status: Offline Points: 66	Post Options Post Reply Quote Speedbird1 Report Post Thanks(0) Quote Reply Posted: 08 Mar 2021 at 12:32pm
	Thanks for the information. It helps to know that I didn't do anything wrong, so to speak. It was a little frustrating as I was trying to 'plan ahead' and ended up getting behind (because it caught me out). I guess this is why we learn this stuff back-to-front so that we don't get caught out when it does something 'unexpected'.