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VOR Approaches Not Working |
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rjt 
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Joined: 10 Jun 2018 Location: Charleston WV Status: Offline Points: 13 |
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 Topic: VOR Approaches Not WorkingPosted: 05 Jul 2023 at 7:37pm |
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Equipment: Two Garmin G5's IFD440 with Version 10.3.1.2 GFC 500 Autopilot Summary: 1. The IFD will accept but NOT use any Course Input from the pilot on VOR approaches. 2. After a VOR approach is cancelled, inputting a Direct To command is ignored. The Direct To function returns after a while. Details: Setting up for the VOR into 12V (Ona Airport) from WV12, the IFD shows GPS->VLOC. Passing the IAF (HVQ) the IFD changes to VLOC and advises the heading is 293 degrees and sets that value as the G5 COURSE. The aircraft will then fly 293 and go right of course. The G5 will let the pilot change the 293 to the FAA specified Course of 288 degs, but the IFD continues using the 293 as verified by a second Nav radio that show an approximate 293 track. The buttons used on the GFC500 are NAV and AP. Cancelling that approach changing Mode from VLOC to GPS and attempting to fly back to origin of WV12 using the Direct TO does not work. Even if the original Route is cancelled, Direct To does not work correctly. Doing a straight VOR approach by turning the IFD to VLOC, inputting the COURSE of 288 and flying manually to the the VOR HVQ, and setting the GFC500 to NAV and AP is not honored. The G5 shows VOR but does not track the 288 COURSE. The failure of the IFD software to honor a COURSE setting existed in 10.3.0.1 (?). This equipment would do VOR approaches correctly earlier this year when a Garmin 430W was in the aircraft. Any suggestions or ideas would be appreciated.
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Ron
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dmtidler
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Joined: 12 Feb 2016 Location: USA Status: Offline Points: 616 |
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Posted: 05 Jul 2023 at 9:27pm |
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Just so we are not mixing up VOR radials and magnetic tracks/courses. The HVQ VOR variation of 3 degrees west most likely aligned with the magnetic variation that existed locally when it was set in 1965. Today, the HVQ VOR lies in an area of variation that is now 8 degrees west; a 5 degree west shift. That means that what was in the 288 degree radial and magnetic course in 1965 is the 288 degree radial and 293 degree magnetic course today. If the VOR approach is flown in VLOC, then it's important to make sure the correct radial specified in the approach procedure is set. The IFD automatically sets the approach magnetic course when it switches to VLOC; which generally needs to be adjusted a few degrees to indicate the proper VOR radial.
I'm curious what the GFC500 FMA roll mode was indicating on the G5 AI after the IFD switched to VLOC? Ideally, the FMA roll mode would have been VOR which would have meant the GFC500 was trying to track the VOR radial set in the G5 HSI. If the GFC500 roll mode was GPS (tracking GPS) before when the IFD switched to VLOC, the GFC500 may have defaulted to ROL mode if NAV wasn't subsequently selected again. In ROL mode, the GFC500 would have just flown wings level and not tried to follow any course or even hold a heading.
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rjt
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Joined: 10 Jun 2018 Location: Charleston WV Status: Offline Points: 13 |
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Posted: 05 Jul 2023 at 10:13pm |
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In answer to some of the questions raised by dmtidler: 1. The IFD automatically sets the approach magnetic course when it switches
to VLOC; which generally needs to be adjusted a few degrees to indicate
the proper VOR radial. Yes, the IFD set the COURSE at 293 deg when changing to VLOC. But even after adjusting Course back to the official value of 288 deg, the system still honored the 293. Nothing I do will change the course from 293 deg. 2. Ideally, the FMA roll mode would have been VOR which would have meant
the GFC500 was trying to track the VOR radial set in the G5 HSI Yes, the G5 was showing VOR in both cases and tracking the G5 of 293 perfectly wrong and unadjustable; that is the issue. You may be onto something; the the plane seemed on several occasions to fly wings level not following any course. This was also evident when I tried to do a Direct To the origin airport. Even trying to help the A/C go in the right direction, I set it almost on the correct course and then did another Direct To. Still seemed to stay wings level and not follow any course. Thanks for the comments.
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Ron
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rjt
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Joined: 10 Jun 2018 Location: Charleston WV Status: Offline Points: 13 |
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Posted: 07 Jul 2023 at 2:57pm |
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A big thanks to dmtidler for his clue as to what was happening with VOR approaches. Workaround: The A/C will fly the VOR approach with 2 caveats: 1. The Avidyne sets the COURSE when flipping into VLOC to 292 deg on the 12V VOR approach. That is not correct and needs to be changed to 288 by the pilot after VLOC appears to stay in compliance. 2. Watch out as the autopilot sometimes drops the NAV setting and will run on AP Button only which by definition is ROL Mode. Opportunities for AVIDYNE 1. When changing from GPS to VLOC, change the course from 292 to the FAA-authorized 288 deg. course. It is now more clear why the Avidyne uses 292 with GPS guidance for a while after crossing the VOR IAF as it would be difficult for the autopilot to track a scalloping radial so close to the VOR. Garmin 430W seemed to do this seamlessly. 2. As a minimum, when changing from GPS to VLOC, consider displaying a message to the effect: Changed to VLOC: Verify Course. The pilot would be alerted to do the COURSE reset. |
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Ron
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rjt
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Joined: 10 Jun 2018 Location: Charleston WV Status: Offline Points: 13 |
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Posted: 03 Aug 2023 at 9:20pm |
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The following is more information about this topic after talking with Mike Salmon, Avidyne user rep, and Gary Reeves, a renowned Avidyne trainer: 1. Per Gary, the FAA requires that an autopilot be disabled if the source guidance changes. This is why the GFC500 goes into ROL mode. 2. Gary supports the idea of displaying a message to the effect that the IFD has changed to VLOC, and check course, etc. He will forward that idea to Avidyne technical group. 3. A request was sent to Mike Salmon to consider populating the COURSE Field on the Garmin G5 with the correct radial when the IFD changes to VLOC. Thus, one press of the NAV Button would re-engage the autopilot similar to what is required today when doing a Go Around on the GFC500. This would provide some consistency when the NAV function is discontinued.
Edited by rjt - 03 Aug 2023 at 9:59pm |
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Ron
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ricardo
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Joined: 17 Jan 2022 Location: Seattle, wa Status: Offline Points: 133 |
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Posted: 03 Aug 2023 at 11:54pm |
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you can avoid having the GFC500 go into ROL PIT mode by making sure you are flying in HDG mode and then switch the IFD from GPS to VLOC.
you can then put the GFC500 back into NAV mode to follow radio nav guidance. this works best if you disable automated switching of GPS to VLOC for approaches.
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rjt
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Posted: 04 Aug 2023 at 10:34pm |
If one disables the automated switching, does the IFD still show the GPS->VLOC status and put the GPS course in the G5 COURSE Field? Thanks for the suggestions.
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Ron
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ricardo wrote: