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Visual Approaches - How to intercept final
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guenter_ms View Drop Down
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Points: 28 		Post Options Post Options   Thanks (0) Thanks(0)   Quote guenter_ms Quote  Post ReplyReply Direct Link To This Post Topic: Visual Approaches - How to intercept final
    Posted: 03 May 2023 at 3:14am
Hi,

I'm not sure about the best practice to intercept the final on a visual approach on my 540/440 combo.

Assuming the last waypoint on my FPL is a VFR only airport and the waypoint is active and autopilot is in GPSS mode. Loading (and not activating) the Visual Approach to the active runway appends two new waypoints to the FPL: RW09 (final track) and repeats the destination airport marked as "destination". So far so good.

Now: How to intercept the final?

My questions:

  1. How to find the TOD at which altitude according to the configured final length (setup VA)?
  2. How to get a waypoint there for easy navigation and autopilot setup, altitude constraint included?
  3. How to activate the visual approach *automatically* when passing the last waypoint before the /Visual Approach/ gap in FPL (the final track is next leg and magenta/white)?
  4. What will be the GPSS track output = input to autopilot (e.g. s-tex 55x) when visual approach is active (I tried a lot with the simulator app but didn't get a clear answer to that question)?

As an FI I'm also familiar with the GTN 750 form Garmin. When loading an visual approach, a (configurable) 3 nm waypoint with altitude constraint according to the configured glide path is automatically included into the FPL, followed by the final track to the RWY. That is awesome!

Is there any setup I missed to get that behavior as well?

Thanks so much for answers to my questions. Maybe I didn't understood the correct how to's. I love the avidyne's but this point is really unclear for me.

Take care!
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vas4avidyne View Drop Down
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Points: 51 		Post Options Post Options   Thanks (0) Thanks(0)   Quote vas4avidyne Quote  Post ReplyReply Direct Link To This Post Posted: 04 May 2023 at 12:59am
Unlike with an instrument approach where one can connect the rest of the flight plan to the approach, I haven't found any way to connect the visual approach to the rest of the flight plan. It seems to exist in isolation and only becomes active when one selects "Activate Visual". I haven't found a way to automatically activate the visual approach even if one intercepts the final approach path.

I am not sure what the protocol level output is to the AP when it is active but for all intents and purposes, the AP tracks it just like it would an RNAV approach with vertical guidance (e.g. LPV).

Vas
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Ibraham View Drop Down
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Points: 363 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Ibraham Quote  Post ReplyReply Direct Link To This Post Posted: 04 May 2023 at 3:46pm
Treat it like being vectored by ATC to intercept an ILS or final approach course on an RNAV approach. 

Autopilot in heading mode with NAV (or APR) armed (blue), it will fly the selected heading then intercepts the final approach course (visual approach course in this case) and automatically activates NAV. 
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guenter_ms View Drop Down
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Points: 28 		Post Options Post Options   Thanks (0) Thanks(0)   Quote guenter_ms Quote  Post ReplyReply Direct Link To This Post Posted: 11 May 2023 at 3:57am
@avidyne:

Can you comment? The answers to the 4 questions above seems to be:

1. not possible
2. not possible
3. not possible
4. unclear

Thats not really satisfying. So I demand this

FEATURE REQUEST

When loading an visual approach, an additional waypoint is inserted at 3nm (customizable, e.g. from defined „final length") from RWY with an altitude constraint computed by distance form RWY and glidepath. This will solve all questions and makes it possible to append the VA to the plan, allowing to see all timings and distances in advance. That would be a great kick. Why should Garmin be so much better at this easy point?

By the way: Loading a VTF approach does this since day one: Automatic waypoint to FAF is inserted. Why not on a VA?

Best Guenter
(Any one supporting this?)
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paulr View Drop Down
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Points: 558 		Post Options Post Options   Thanks (0) Thanks(0)   Quote paulr Quote  Post ReplyReply Direct Link To This Post Posted: 11 May 2023 at 11:33am
I like that idea, Guenter.
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guenter_ms View Drop Down
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Points: 28 		Post Options Post Options   Thanks (0) Thanks(0)   Quote guenter_ms Quote  Post ReplyReply Direct Link To This Post Posted: 24 Jul 2023 at 1:47am
@avidyne: please comment. Thank you. 
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MysticCobra View Drop Down
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Points: 662 		Post Options Post Options   Thanks (0) Thanks(0)   Quote MysticCobra Quote  Post ReplyReply Direct Link To This Post Posted: 24 Jul 2023 at 8:17am
Originally posted by guenter_ms guenter_ms wrote:

FEATURE REQUEST

When loading an visual approach, an additional waypoint is inserted at 3nm (customizable, e.g. from defined „final length") from RWY with an altitude constraint computed by distance form RWY and glidepath. This will solve all questions and makes it possible to append the VA to the plan, allowing to see all timings and distances in advance. That would be a great kick. Why should Garmin be so much better at this easy point?
Guenter, have you submitted this via Avidyne's "official" feature request form?

Avidyne forum post about the process:  http://www.avidynelive.com/submit-your-suggestions_topic2483.html

Direct link to the form:  https://www.avidyne.com/contact-us-2/
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AviSteve View Drop Down
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Points: 2244 		Post Options Post Options   Thanks (0) Thanks(0)   Quote AviSteve Quote  Post ReplyReply Direct Link To This Post Posted: 24 Jul 2023 at 9:45am
Visual approaches are preceded by a discontinuity just like vectors-to-final for an instrument approach.  The difference is that an instrument approach has a FAF (from the database) whereas a visual approach does not (because a visual approach doesn't come from the database).

We tried various implementations of visual approaches during development, including the addition of a waypoint at "final length", but eventually settled on the current implementation because we thought that it worked best.

I've created a feature request in our database for consideration.
Steve Lindsley
Avidyne Engineering
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guenter_ms View Drop Down
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Points: 28 		Post Options Post Options   Thanks (0) Thanks(0)   Quote guenter_ms Quote  Post ReplyReply Direct Link To This Post Posted: 24 Jul 2023 at 10:48am
Thank you Steve,

as an FI I'm flying Avidyne and Garmin units and can strongly confirm the advantage of that feature.
I understood you copied the request, so I don't need to do that again.

Best
Guenter
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