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Old 03-17-2021, 04:16 PM
macrafic's Avatar
macrafic macrafic is offline
Join Date: May 2006
Location: Rochester, MN
Posts: 429
Default Interrupting, then Resuming an Approach

This does not happen often and, in an actual IFR situation, I would most likely start the approach over. So, assume this is in a practice IFR approach with a safety pilot or VFR conditions.

I do just fine flying IFR ILS and RNAV approaches with my GTN650 and G3X system. Where I am clueless however is when the approach needs to be interrupted and then resumed. This happened the other day when the tower asked me to do a 360 for spacing at one of the approach fixes.

Does anyone have a set of steps that I need to take (assuming on the GTN) to accomplish this? Is it even possible?
Rich and Cindy Macrafic
Rochester, MN
RV-7A Flying
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Old 03-17-2021, 05:15 PM
BobTurner BobTurner is offline
Join Date: Dec 2011
Location: Livermore, CA
Posts: 7,447

Prior to the holding fix, set the gps to what’s called ‘OBS mode’ on the 430W. Might be called ‘suspend’ on the GTN. Set the OBS to the holding radial. After you have done the requisite number of turns, and are inbound to the fix, hit OBS again on the 430, or ‘unsuspend’ on the GTN.
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Old 03-17-2021, 05:28 PM
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Auburntsts Auburntsts is offline
Join Date: Jan 2005
Location: Tampa, FL
Posts: 2,970

You could treat it as an unpublished hold and follow the steps Bob mentioned or since it’s not really a hold as far as the avionics are concerned I think you could just fly the 360, rejoin the active leg and press as if nothing happened— no button pushing required. If you’re coupled you just go into heading mode and move the bug around and as you close on the inbound course go back into Nav mode.
Todd "I drink and know things" Stovall
RV-10 N728TT - Flying!

Last edited by Auburntsts : 03-17-2021 at 05:32 PM.
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Old 03-17-2021, 05:40 PM
BillL BillL is online now
Join Date: Sep 2007
Location: Central IL
Posts: 5,968

Like stated, just release the AP (G3X), then you can fly the 360 by hand or enter a bank and engage PIT/ALT mode with the disconnect (CWS) button. I think 3 seconds will be required.

The 650 (untouched) will still be giving guidance (in the background) but it won't be engaged with the AP - it might get upset, but will still have that next WPT in its sights and as soon as the 360 is over - directly engage APPR mode and it should resume vertical and lateral guidance coupled to the AP and bring it back on course.

No 650 buttons should be needed and all the action is breaking and reengaging the AP coupling.

Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”

Last edited by BillL : 03-17-2021 at 05:44 PM.
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Old 03-17-2021, 07:41 PM
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Longez Longez is offline
Join Date: May 2009
Location: KS
Posts: 217


As long as you are outside the FAF, and haven't captured the GP/GS, it is pretty simple to accommodate a request to fly a "360 for spacing", especially if you are still in altitude hold.

For this approach I arrive at the SOKYO IAF at 3,100 ft in altitude hold, and stay at that altitude through the procedure turn until intercepting the glidepath prior to the ROKSE FAF.

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If the tower requests a 360 for spacing just as you report inbound on the procedure turn outside of the IAF, leave your navigator alone, and simply reach up and press the autopilot TRK button. You can also use the HDG button, but make sure to push in on the HDG/TRK knob first to sync selected HDG to current HDG.

Next, just use the HDG/TRK knob to turn the plane left or right and the autopilot will follow the HDG/TRK bug, and fly a perfect standard rate turn back around to the approach course. As the plane is coming around the turn on a path to intercept the approach course, just press the APR button and the autopilot will resume the approach right where you left off.

As another example, if the tower requests a 360 for spacing as you report the IAF inbound, the system will have just transitioned to the FAF being the active waypoint (in this example approach), but that is also fine. Just do the same thing using the TRK and APR buttons to circle and then re-capture the approach course.

As mentioned earlier, you can't circle after capturing the glidepath/glideslope, or the navigator will annunciate an approach error condition.


Last edited by Longez : 03-17-2021 at 08:01 PM.
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