Avidyne Homepage
Forum Home Forum Home > Avidyne General > IFD 5 Series & IFD 4 Series Touch Screen GPS/NAV/COM
  New Posts New Posts RSS Feed - VTF
  FAQ FAQ  Forum Search   Register Register  Login Login

VTF

 Post Reply Post Reply
Author
Message
sltx1050 View Drop Down
Newbie
Newbie
Avatar

Joined: 01 Feb 2019
Location: St. Louis, MO
Status: Offline
Points: 14
Post Options Post Options   Thanks (0) Thanks(0)   Quote sltx1050 Quote  Post ReplyReply Direct Link To This Post Topic: VTF
    Posted: 21 Feb 2020 at 2:13pm
Brought this up on the Facebook page, but is there a good reason why the VTF mode for an approach does extended centerline of the final course while all other navigators do VTF and extension of the arrival course from IAF/IF to the FAF.
Back to Top
dmtidler View Drop Down
Senior Member
Senior Member
Avatar

Joined: 12 Feb 2016
Location: USA
Status: Offline
Points: 616
Post Options Post Options   Thanks (0) Thanks(0)   Quote dmtidler Quote  Post ReplyReply Direct Link To This Post Posted: 21 Feb 2020 at 4:29pm
This appears to only be the case for RNAV GPS approaches and is covered by the following caution on page 6-29 of the IFD5XX PG:

VTF Transitions

VTF transitions in the IFD provide guidance to the extended final approach course.

When assigned a VTF clearance on an SBAS approach (WAAS- or EGNOS-based LPV, LP and LNAV/VNAV) with an offset leg into the Final Approach Fix (FAF) where the leg to the FAF is not aligned with the final approach course (i.e. an angled entry to the FAF), the pilot should ask the ATC controller to clarify if those vectors are to extended final or the published offset inbound leg to the FAF.

In the case where ATC responds with the extended final scenario, Avidyne recommends the pilot select the “Vectors” transition option in the FMS approach dropdown. In the case where ATC responds with the published offset leg scenario, Avidyne recommends the pilot activate the inbound leg to the FAF from the FMS FPL tab to ensure the offset leg is accounted for.

I verified this behavior in the IFD simulator using the RNAV GPS 2 at KISW and the VOR/DME-A at 20V. VTF activation for the RNAV GPS 2 at KISW resulted in an extension of the final approach course on both sides of the FAF; however, for the VOR/DME-A at 20V, the VTF inbound course to the FAF was 051 with a change to 034 after crossing the FAF.

I'm not aware of the whys behind that VTF philosophy, but it appears to work as described in the IFD PG.
Back to Top
sltx1050 View Drop Down
Newbie
Newbie
Avatar

Joined: 01 Feb 2019
Location: St. Louis, MO
Status: Offline
Points: 14
Post Options Post Options   Thanks (0) Thanks(0)   Quote sltx1050 Quote  Post ReplyReply Direct Link To This Post Posted: 21 Feb 2020 at 8:50pm
yeah I saw that in the manual
Back to Top
dmtidler View Drop Down
Senior Member
Senior Member
Avatar

Joined: 12 Feb 2016
Location: USA
Status: Offline
Points: 616
Post Options Post Options   Thanks (0) Thanks(0)   Quote dmtidler Quote  Post ReplyReply Direct Link To This Post Posted: 22 Feb 2020 at 11:16am
I did a little more research using the IFD simulator as well as an IFD100. I spot checked four more VOR approaches with offsets to the FAF (KSHR VOR 15, KCEZ VOR 21, KMFR VOR A, and 74V VOR A). In all four of theses cases, VTF to the FAF used the final approach course; not the offset. The KMFR VOR A is very similar in layout to the 20V VOR/DME A; I have no idea why the 20V approach VTF uses the offset and all of these other approaches do not.


Back to Top
 Post Reply Post Reply
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.01
Copyright ©2001-2018 Web Wiz Ltd.

This page was generated in 0.111 seconds.