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The Garmin manuals are a bit confusing regarding the visual approach waypoints on NXi. I came across this great explanation by Peter King from www.MasterFlight.aero on the Cirrus Owners site, and he gave me permission to copy it.

The idea behind the FMS visual approaches is to provide support for a visual approach using traditional FMS waypoints, sequencing, and lateral and vertical guidance.

The FMS creates vertical guidance for a visual approach path similar to the way it creates vertical guidance for an LNAV+V approach. The ACFS captures visual approach guidance the same way it captures LNAV+V guidance and the PFD displays visual approach guidance the same way it displays LNAV+V guidance.

However, the selection of altitudes and vertical descent angles is somewhat simplistic, and does not really take terrain into account. These approaches must be flown in visual conditions, and the vertical guidance is advisory only.

The Visual Approach creates three waypoints based on the configuration and orientation of the runway:

RWxxx
The runway threshold.

FINAL
A waypoint placed on the extended centerline of the runway at a position that approximates where you would roll out onto final flying a normal pattern. Usually, this is around 1nm from the runway threshold, but that distance can be adjusted by the aircraft manufacturer.

STRGHT
A waypoint placed farther out on final, to be used for straight-in approaches. The design for the straight-in transition is to descend to traffic pattern altitude (TPA) at STRGHT, level off, and from there capture the glidepath to descend to the runway. Typically this is around 3.5nm for a 1,000’ AGL TPA and a 3 degree glidepath, i.e., about 0.5nm outside where the glidepath intercepts TPA.

The glidepath extends from the runway touchdown point past the FINAL waypoint. If the navigation database contains the visual glide slope indicator (VGSI) angle for the runway, e.g. a PAPI or VASI, it will use that to generate the FMS glideslope. Otherwise, an approach glide path angle of 3 degrees is typically used. Consequently, the typical altitude on the glidepath at FINAL is approximately 370’ AGL.

When a “STRAIGHT” transition is activated, advisory vertical guidance (magenta diamond) is available after the STRGHT waypoint has been passed and the FINAL leg is active. When the “VECTORS” transition is selected, a 30NM coure-to-fix (CF) leg ending at FINAL(FAF) is activated. The STRGHT waypoint remains in the flight plan, if you desire to use it, but FINAL is the active waypoint.

If you want to understand the behavior, compare it to an LNAV+V approach, and think of FINAL as the FAF, and STRGHT as the preceding intermediate fix. All the FMS sequencing works the same. You can use VNAV (magenta caret) to descend to STRGHT, where, by default, you will end up at pattern altitude approximately 3.5nm, away from the airport (regardless of terrain). When FINAL becomes the active waypoint, the glidepath (magenta diamond) will appear, to guide you down along the VGSI angle to the touchdown point.

The main difference from an RNAV approach is that these fixes are much closer to the airport than you are used to. As I said before, the nominal altitude at STRGHT is pattern altitude, and the nominal altitude at FINAL is 370’ AGL. It takes a while to get your mind wrapped around that difference.

[Username Protected]

Thanks for posting this!

I see that the manufacturer can modify these points. It seems that in my a/c (Phenom 100EV, G3000) that the STRAIGHT waypoint is more like 5nm out and at 1500' AGL. I don't know if that is the case all the time, but it seems like it that's the case most of the time that I have used this feature.

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Makes sense that Cirrus is at Pattern Altitude is set at 1,000' and Phenom Pattern Altitude is set at 1,500'

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(Username Protected),

Can you check the nm distance from FINAL to the runway on the G3000. It is 1 nm on NXi (I am guessing Garmin default) which seems a bit tight, specially when using it from a base leg.

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(Username Protected),

The FINAL waypoint on my G3000 is also 1nm out. STRAIGHT is at 5nm.

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