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Turning the wrong way at waypoint

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Cruiser View Drop Down
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    Posted: 02 Oct 2017 at 7:14pm
My first long trip using IFD540/440 navigators. Enroute flight using GPSS steering on my Aspen PFD commands all the turns as expected BUT....
entering the procedure and activating the approach requiring a HOLD, crossing the fix the depiction of the HOLD and the entry is shown on the IFD 540 but the autopilot flies out of the fix and does a course reversal IN THE OPPOSITE DIRECTION. The IFD540 announces leaving the HOLD at the fix and then will fly the rest the approach as expected.

This happened three separate times at three different airports and three different approaches.

can anyone explain this for me?
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Catani View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Catani Quote  Post ReplyReply Direct Link To This Post Posted: 03 Oct 2017 at 12:01am
It's doing what you asked it to do: fly the approach as depicted on the chart, including the procedure turn.  If you want to fly only the portion from the final course inbound to the FAF, highlight the FAF after the hold and select the PSK "Activate leg."
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Cruiser Quote  Post ReplyReply Direct Link To This Post Posted: 03 Oct 2017 at 5:10pm
To clarify the issue. The autopilot did not follow the approach as depicted on the chart. That is the problem.
The approach (as shown on the IFD540 included a hold) the autopilot TURNED THE OPPOSITE direction away from the hold, made a 180° turn back to the fix and continued inbound.

To explain it another way, on the SV page of the IFD540 Map, the HOLD was shown in white, the inbound course to the fix was MAGENTA, the teardrop entry (inside the HOLD space) was dashed white/magenta. After crossing the fix, the plane was no where near any of the course lines but way off to the right turning away from the course.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ronl Quote  Post ReplyReply Direct Link To This Post Posted: 04 Oct 2017 at 12:07am
You can also just select (touch) the "hold at" line in the FMS route list. A "delete hold?" Line select key option will instantly pop-up. Push the button and it's gone. Easy peasy.
Ron L
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jamorowitz Quote  Post ReplyReply Direct Link To This Post Posted: 01 Nov 2017 at 11:57am
I believe you are experiencing what I have noticed. Even though the hold for a couse reversal is shown correctly with appropriate entry on the moving map, the CDI does not give appropriate course guidance. It seems to be giving needle indications as though you are inbound, even while you are still outbound. I have never figured this out. Discussed it with tech support a couple of times but never got an answer.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 94S Quote  Post ReplyReply Direct Link To This Post Posted: 02 Nov 2017 at 9:29am
Originally posted by Jamorowitz Jamorowitz wrote:

I believe you are experiencing what I have noticed. Even though the hold for a couse reversal is shown correctly with appropriate entry on the moving map, the CDI does not give appropriate course guidance. It seems to be giving needle indications as though you are inbound, even while you are still outbound. I have never figured this out. Discussed it with tech support a couple of times but never got an answer.


Jamorowitz,
Do you have GPSS?  If not, when flying outbound on a course reversal, the GPS/CDI gives reverse sensing (just like a VOR/LOC).  This is not an IFD thing.  G's products do the same thing.  It must be written into the FAA standards for GPS navigation.  I really don't understand why this is.  One of the fundamental tenets in GPS navigation is that you are always navigating to a waypoint.  Apparently procedure turns are an exception to that rule.  So what if the waypoint happens to be at the far end of two straight segments with a turn between them.

Cruiser, the OP, has GPSS and the autopilot should have followed the magenta line around the procedure turn as depicted.  It's very curious that it went to the opposite side of the procedure turn.

I don't have GPSS in my airplane, so I'm not real certain as to how they work.  I don't know if there are differences between manufactures.  G1000s are the only ones I've flown, and are a different animal because they are fully integrated.  Third party systems may not work the same.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jamorowitz Quote  Post ReplyReply Direct Link To This Post Posted: 03 Dec 2017 at 5:03pm
My problem occurs even when hand flying. You can be tracking the magenta line outbound on a teardrop, and the CDI deflection steadily increases. It is not tracking the line either normal or reverse sensing.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Catani Quote  Post ReplyReply Direct Link To This Post Posted: 03 Dec 2017 at 6:40pm
Originally posted by Jamorowitz Jamorowitz wrote:

My problem occurs even when hand flying. You can be tracking the magenta line outbound on a teardrop, and the CDI deflection steadily increases. It is not tracking the line either normal or reverse sensing.
Can you clarify whether your problem is with an entry into a published hold or an entry into a procedure turn?  Can you also specify the airport and approach plate you were on where the problem occurred, and identify the holding or PT fix you were trying to enter the hold or PT?  Also, for that approach plate, what heading you were using just prior to reaching the fix where the hold or the PT was to begin?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PA20Pacer Quote  Post ReplyReply Direct Link To This Post Posted: 04 Dec 2017 at 9:14am
Originally posted by Jamorowitz Jamorowitz wrote:

My problem occurs even when hand flying. You can be tracking the magenta line outbound on a teardrop, and the CDI deflection steadily increases. It is not tracking the line either normal or reverse sensing.

What is described above is normal and expected behavior. On the entry to a hold, the CDI will show the deviation with respect to the inbound (holding) leg, so the deviation should continuously increase during a teardrop entry. An autopilot with GPSS will follow the magenta line, but the CDI will still show the deviation with respect to the inbound leg.

Regards,

Bob
Bob Siegfried, II
Brookeridge Airpark (LL22)
Downers Grove, IL
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Catani Quote  Post ReplyReply Direct Link To This Post Posted: 04 Dec 2017 at 12:10pm
Originally posted by PA20Pacer PA20Pacer wrote:

Originally posted by Jamorowitz Jamorowitz wrote:

My problem occurs even when hand flying. You can be tracking the magenta line outbound on a teardrop, and the CDI deflection steadily increases. It is not tracking the line either normal or reverse sensing.

What is described above is normal and expected behavior. On the entry to a hold, the CDI will show the deviation with respect to the inbound (holding) leg, so the deviation should continuously increase during a teardrop entry. An autopilot with GPSS will follow the magenta line, but the CDI will still show the deviation with respect to the inbound leg.

Regards,

Bob
Quite true, as to the OP's last post.  But he said the autopilot turns in the wrong direction in an earlier post.  Really?  Getting to the bottom of the OP's concerns, and what is right or wrong about his equipment or pilot technique and understanding, is difficult for me without the additional information I requested from the OP.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ac11 Quote  Post ReplyReply Direct Link To This Post Posted: 04 Dec 2017 at 11:35pm
@Cruiser, what autopilot do you have? I had an aha moment a while back where I was flying the departure procedure out of my home airport, and the autopilot (a Century III) with GPSS selected on the Aspen started turning me left instead of right. I discovered that this was due to having LOC selected on the CIII. When I switched to HDG, the AP successfully followed the course. Does this possibly match your scenario?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Cruiser Quote  Post ReplyReply Direct Link To This Post Posted: 07 Dec 2017 at 11:39am
Originally posted by Catani Catani wrote:


Quite true, as to the OP's last post.  But he said the autopilot turns in the wrong direction in an earlier post.  Really?  Getting to the bottom of the OP's concerns, and what is right or wrong about his equipment or pilot technique and understanding, is difficult for me without the additional information I requested from the OP.

I am sorry but I don't know what additional information you requested? 
As a followup,  I have done several more approaches as I become more comfortable with my new equipment and they have all performed as expected.
My concern is that I am doing something that caused the problem. I don't want it to happen again.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Catani Quote  Post ReplyReply Direct Link To This Post Posted: 07 Dec 2017 at 1:17pm
Originally posted by Cruiser Cruiser wrote:

Originally posted by Catani Catani wrote:


Quite true, as to the OP's last post.  But he said the autopilot turns in the wrong direction in an earlier post.  Really?  Getting to the bottom of the OP's concerns, and what is right or wrong about his equipment or pilot technique and understanding, is difficult for me without the additional information I requested from the OP.

I am sorry but I don't know what additional information you requested? 
As a followup,  I have done several more approaches as I become more comfortable with my new equipment and they have all performed as expected.
My concern is that I am doing something that caused the problem. I don't want it to happen again.
My post above on December 3rd asked:  

"Can you clarify whether your problem is with an entry into a published hold or an entry into a procedure turn?  Can you also specify the airport and approach plate you were on where the problem occurred, and identify the holding or PT fix you were trying to enter the hold or PT?  Also, for that approach plate, what heading you were using just prior to reaching the fix where the hold or the PT was to begin?"

While your problems could have occurred on multiple occasions at different airports or approaches, narrowing things down to one particular problem approach plate, as just one example situation to evaluate, eliminates a lot of variables that should make it easier to figure out exactly what's going on in any approach you've had problems with.

Or, just keep practicing as you've been doing.  And go back and re-read the manual's discussion of the particular function that puzzles you - it never sinks in completely the first few times. With familiarity comes understanding, and with understanding comes confidence in the equipment and the ability to recognize mistakes and correct them more quickly.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Cruiser Quote  Post ReplyReply Direct Link To This Post Posted: 07 Dec 2017 at 4:33pm
here is one of the approaches that was captured on FlightAware. After attempting the ILS at KGRR we transisioned to Sparta 8D4. I loaded the approach for Rwy 07 and allowed the autopilot to fly outbound to the IAF HUUNT 
It is very clear on the flight track that we did a procedure turn on the opposite side of the approach instead of the hold as depicted on the approach plate. As I recall, the autopilot flew to the fix(HUUNT) and then continued outbound turning right instead of left. The Avidyne displayed the teardrop entry and the hold but the autopilot did not fly what was on the Avidyne IFD540 screen.

I have Aspen 2500, dual Avidynes and S-tec 55x equipment. Is there a combination of settings that would make this happen?

http://flightaware.com/live/flight/N99MS/history/20171001/1945Z/KVLA/8D4


Edited by Cruiser - 07 Dec 2017 at 4:38pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mfb Quote  Post ReplyReply Direct Link To This Post Posted: 07 Dec 2017 at 10:16pm
What mode was the autopilot in? Did you have the GPSS mode selected on the Aspen?

It sounds like the problem is with the autopilot, not the IFD540. My Century autopilot needs to be in HDG mode with GPSS engaged until it's on the final approach course. Then I switch to APCH mode. I suspect that your STEC is the same.

Mike
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Catani Quote  Post ReplyReply Direct Link To This Post Posted: 08 Dec 2017 at 2:52pm
Originally posted by Cruiser Cruiser wrote:

here is one of the approaches that was captured on FlightAware. After attempting the ILS at KGRR we transisioned to Sparta 8D4. I loaded the approach for Rwy 07 and allowed the autopilot to fly outbound to the IAF HUUNT 
It is very clear on the flight track that we did a procedure turn on the opposite side of the approach instead of the hold as depicted on the approach plate. As I recall, the autopilot flew to the fix(HUUNT) and then continued outbound turning right instead of left. The Avidyne displayed the teardrop entry and the hold but the autopilot did not fly what was on the Avidyne IFD540 screen.

I have Aspen 2500, dual Avidynes and S-tec 55x equipment. Is there a combination of settings that would make this happen?

http://flightaware.com/live/flight/N99MS/history/20171001/1945Z/KVLA/8D4
I agree with Mike.  I don't think Cruiser's autopilot was in GPSS mode for any number of possible reasons.  You might want to investigate to find out if you have equipment problems, if you are sure you activated the GPSS mode on the autopilot. (Note the autopilot will try to fly the CDI or heading bug if not in GPSS mode, and depending upon your orientation to the fix may seem to be in GPSS mode when it's really not.  Unless in GPSS mode, however, the autopilot can't fly procedure turns or enter holding properly and the failure is obvious as you found out, so that would be a good test of your equipment if you want to try to duplicate the problem.)  With the IFD540 showing the correct course, the proper information was being provided by the IFD to whatever output your installation has it wired up to.  That's all you can expect the IFD to do.  If it happens again in actual IMC before you figure out what is going wrong, hand fly the course depicted on the IFD - don't let the autopilot fly the airplane off course.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mfb Quote  Post ReplyReply Direct Link To This Post Posted: 08 Dec 2017 at 4:58pm
Maybe you know this already, but here's how things work:

Typical analog autopilots (like your STEC and my Century) can't process the steering commands generated by a modern digital flight management system like the IFD540. GPSS is a magic box that goes between the IFD and the autopilot. It emulates the heading bug on the autopilot, so the autopilot steers the courses provided by the IFD.  You generally don't use the autopilot NAV mode with the IFD, because NAV can't handle large course changes like holds, procedure turns, or even turns across enroute waypoints.

So the general rules are:

1) For normal enroute and terminal flying, put the autopilot in HDG mode and select GPSS on the Aspen. (The Aspen includes a built-in GPSS. If you don't have an Aspen you need a stand-alone GPSS box.) That enables the IFD to steer the airplane and track whatever route you have programmed. The autopilot thinks that you're steering it with the heading bug, but the GPSS is really doing the work.

2) When lined up on the final approach course, put the autopilot in APPROACH mode. It will follow the approach course and track the glide slope (if you have a two-axis autopilot). This is pretty much a straight-line phase of flight. The autopilot follows the CDI and thinks it's tracking an ILS, even if you're really doing a GPS LPV approach. It doesn't matter if you leave GPSS engaged. The autopilot isn't using it any more because it's not in HDG mode.

3) When you miss an approach, put the autopilot back in HDG mode and make sure that GPSS is still turned on. The IFD will steer the airplane through the missed approach procedure.

Hope this helps.

Mike


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ibraham Quote  Post ReplyReply Direct Link To This Post Posted: 09 Dec 2017 at 6:42pm
The first thing to do when the autopilot is not doing what you expect it to do is to either put in the heading mode (after setting the heading bug) or disconnect it. In the above scenario, the autopilot commanded the airplane to turn right, which is outside the protected side of the published hold, something ATC does not expect and could potentially be problematic.

The GPSS button in the Aspen is a nice feature, but could be problematic as the STEC has to be in the heading mode. That is confusing when you look at the autopilot display. A better option is to use the GPSS button on the STEC,  that way there is no doubt what mode it is in.

Again, Disconnect the autopilot and manually fly the airplane if it is doing something unexpected.

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