VTF |
Post Reply |
Author | |
sltx1050
Newbie Joined: 01 Feb 2019 Location: St. Louis, MO Status: Offline Points: 14 |
Post Options
Thanks(0)
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.
|
|
dmtidler
Senior Member Joined: 12 Feb 2016 Location: USA Status: Offline Points: 616 |
Post Options
Thanks(0)
|
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.
|
|
sltx1050
Newbie Joined: 01 Feb 2019 Location: St. Louis, MO Status: Offline Points: 14 |
Post Options
Thanks(0)
|
yeah I saw that in the manual
|
|
dmtidler
Senior Member Joined: 12 Feb 2016 Location: USA Status: Offline Points: 616 |
Post Options
Thanks(0)
|
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.
|
|
Post Reply | |
Tweet
|
Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |