Activating Approach

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gtmize
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Activating Approach

Post by gtmize »

"Activate Approach" on the MFD
and / or
APR Key?

So you've loaded an approach ( not activated )
Descending VNAV to the first leg altitude to catch GP .. with a flat place awaiting Clearance to shoot it

When you receive Clearance
is hitting APR key sufficient to activate it?

If so what's the purpose of " Activate Approach" on the MFD menu?
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AndrewM
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Re: Activating Approach

Post by AndrewM »

I am assuming you are using a G1000. The procedure I use is... the very moment you start to receive vector(s) from the approach controller, I hit "activate vectors to final" on the PFD. Then, when you hear the words "cleared for the approach" I hit the "ARP" key.

I believe Activate Approach on the MFD is the same as the APR key on the G1000 panel. However... others may have other techniques or know better!
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Chris B
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Re: Activating Approach

Post by Chris B »

gtmize wrote: Thu Nov 28, 2019 12:54 pm When you receive Clearance is hitting APR key sufficient to activate it?
Yes. This arms the glide slope as appropriate.

gtmize wrote: Thu Nov 28, 2019 12:54 pm If so what's the purpose of "Activate Approach" on the MFD menu?
Initiate a course reversal and take you to a point behind your current position? ;)

Pressing "Activate Approach" is functionally equivalent to "direct-to" the first fix in the approach. Which by the time you receive your clearance is usually far behind.

Garmin should remove the "Activate Approach" soft key. I can't think of any reason to use it, and plenty of reasons to avoid it.

Chris
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Re: Activating Approach

Post by TwinStarScott »

If we're limiting this discussion to the legacy G1000 (say GDU version 9.05, which I'm most familiar with) then:

Along with Garmin removing "Activate Approach", "activate vectors to final" * should also be avoided - according to CFII's like Max Trescott and Gary Reeves. Instead they recommend using "activate leg".

Here's a link to an article from another source located here in the Pacific NW - CFII Bruce Williams (who used to work for Microsoft and on their flight sim program):

https://bruceair.wordpress.com/2010/11/ ... -scramble/

Also:
https://bruceair.wordpress.com/?s=vectors+to+final

* might not apply to more current software versions of the GTN navigators. Perhaps even the NXi.
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Re: Activating Approach

Post by TwinStarScott »

Simply put:

Only use activate for a "leg", and never "vectors to final" or for an "approach".
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Re: Activating Approach

Post by Boatguy »

Short answer:
- Load/Activate approach on the MFD controls the flight plan and flight director.
- APR key controls the Autopilot.

"Load Approach" will load the approach waypoints, nav frequency and nav course (if ILS/LOC or VOR), but not change the active waypoint. Later on you can select the desired active waypoint and use Direct To or Activate Leg (soft key or menu item) to make that waypoint the active waypoint.

If the waypoint is the last in an approach (e.g., MAHP), another approach may be loaded and its waypoints will be inserted after the last waypoint of the previous approach. Loading a second approach while the first approach is otherwise active will replace the currently active approach.

"Activate Approach" in the MFD loads the waypoints, frequency and nav course (if ILS/LOC or VOR) for the approach and makes the first waypoint the active waypoint. If you select VTF (vectors to final), the active waypoint will be the FAF. On older models waypoints before the FAF will not be loaded. With NXi all waypoints are loaded.


Long answer varies depending on the G1000 era. This is what APR does on my G1000NXi system with WAAS.

If the approach is an ILS or VOR, both "Activate" and "Load" will load the ILS/VOR frequency into the active position of the currently selected Nav radio and load the final approach course into the Course of the selected NAV radio. The ILS or VOR need not be the currently selected nav source (i.e., Nav1 or Nav2) in the CDI.

"APR" on the autopilot panel puts a lateral and vertical mode in "standby" in white letters, with the lateral mode to the left of the current lateral mode and the vertical mode to the right of the current vertical mode. What will be in standby and how it proceeds depends on the approach as follows:

RNAV (GPS) LPV (i.e., WAAS active)
- Lateral: GPS is probably already active with the magenta needles in the CDI. I'm not sure what it will do if the current lateral mode is HDG.
- Vertical: "GP" will be in white letters and the autopilot will be waiting to intercept the Glide Path. When the flight path intercepts the glide path, GP will slide to the left and become the active (green) vertical mode and the AP will follow the GP irrespective of selected altitude.


ILS
- Lateral: If the localizer is being received by the nav radio, "LOC" will be in white letters to the left of the current lateral AP mode. Once the localizer is within one dot of deflection, it will switch the current nav on the CDI to LOC (green needles) and track the localizer.
- Vertical: "GS" will be in white letters and the autopilot will be waiting to intercept the Glide Slope. When the flight path intercepts the glide slope, GS will slide to the left and become the active (green) vertical mode and the AP will follow the GS irrespective of selected altitude.

VOR
- Lateral: "VAPP" will be in white letters to the left of the current lateral AP mode. When the VOR radial is intercepted (i.e., the previously loaded course) within one dot of deflection, VAPP will become the active lateral AP mode. VAPP is supposed to have increased sensitivity compared with VOR mode. I'm pretty sure the CDI will automatically switch to green needles upon intercepting the radial.

- Vertical: Manually selected altitude (e.g., VS/FLC) or VNAV glidepath from active waypoint with altitude in flight plan.

VNAV has it's own set of constraints before it will become active.

The combinations of behaviors is somewhat daunting and the above is probably not a perfect description, but it's close to what I've experienced.

YMMV!
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Re: Activating Approach

Post by CFIDave »

Simpler answers to the OP (Gary's) questions:

1. Hitting APR key arms vertical (as well as lateral) guidance for capturing a glideslope/glidepath. If you are flying in NAV mode and forget to hit APR when cleared for the approach, the plane will turn laterally to follow an approach you've loaded, but won't descend vertically.
If you're being vectored to the approach by ATC and flying in HDG mode, hit APR when ATC says you're cleared for the approach over the radio; this will cause the plane to turn inbound when intercepting the inbound course AND descend when it intercepts the glideslope/glidepath.

2. "Activate Approach" both loads an approach AND provides immediate course guidance to the first waypoint of that approach (i.e., the IAF). Most of the time you don't want to use this. Instead only "Load" the approach.
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