[SELF SOLVED] Along track waypoint(s)

[softreset]

I'm practicing some along track waypoints. Currently enroute to MYGF and expecting the RNAV 06 (based on forecasted winds).

However, what I'm attempting to do is put a waypoint, 5nm ahead of the airport as you can see via the attached images. My understanding to create this FMS programming.

• Add the waypoint to the flight plan
• Ensuring it's sequenced after the previous point (no discos)
• Then select the waypoint and do / -Xnm (where X is the distance before the waypoint)
• Then click the waypoint to insert it before

In doing that I'm presented with the message you see: Along track WPT N/A

I'm doing something wrong!  Any advice? The FMS primer documentation doesn't cover this concept so I'm trying to reference what information I've found online regarding the documentation.

Edited January 26, 2022 by Pils

[Tord]

I think this should help?
https://youtu.be/GODF3B7odTE

[Jakobb]

I did not see any relevant limitation in the FCOM but I would assume that it only works with Wpts not airports

[Rodeo]

(1) there is a discontinuity between MYGF and the rest of the route

(2) you're requesting a waypoint along the route 5 miles before MYGF, but your route starts at MYGF -- a waypoint along the route before the route starts or after the route ends doesn't exist, to my knowledge

[Jakobb]

1 hour ago, Rodeo said:

(1) there is a discontinuity between MYGF and the rest of the route

The new WPT should be before the disco, I don‘t see why this is an issue. If it were after the disco I would understand

1 hour ago, Rodeo said:

(2) you're requesting a waypoint along the route 5 miles before MYGF, but your route starts at MYGF -- a waypoint along the route before the route starts or after the route ends doesn't exist, to my knowledge

If you look at the PFD you can clearly see that MYGF is not the first or next WPT

[Rodeo]

My bad-- I guess i just didn't expect an airport inn the middle of the route 

[softreset]

An update & some clarifications as I successfully completed a 5nm before airport insertion on a flight just now into a non STAR'd arrival routing.

Regarding why I built the route this way @Rodeo, I was flying into MYGF with approach on (but no center) and the TAF for airport implied a possible shift in winds. So that waypoint you see below the disco is actual the IAF for the RNV 06 into MYGF. I've also seen a half dozen real world Garmin videos where the example of arrival planning for Un sequenced arrivals was taught to do the ATK -5 or -10nm from the field. I was looking to artificially setup a VNAV profile. Similar to the video that @Tord referenced.

My thought process was, if I'm at pattern altitude (ish) 5-10 NM from the field, I had flexibility to either fly the 06 visually, pick up the IAF, circle to land on 24 or overfly the field and come back on the 24 approach. The 1500 AGL gave me options and some vertical guidance, as a supplemental solution to the rule of 3.

Why it didn't work this time, is because what you can't see on the previous page of the FMS is that my waypoint before MYGF is actually the VOR at the field (ZFP) and I bet it was confused on how to create the -5 NM waypoint from the field because it would have been before ZFP on my routing.

After I did some debugging on the route (after the successful -5nm planned KLIT arrival), after removing ZFP it allowed me to do the -5nm ATK waypoint off MYGF.

TL;DR - Operator error, ATK works just fine. Ensure that the waypoint it's creating isn't further away from the sequenced waypoint before the point you're looking to ATK against.