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Missed Approach Question

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PEFeinman View Drop Down
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    Posted: 10 May 2015 at 7:24am
I have been flying with my IFD540 now for about 3 flights.  At the same time we installed our IFD540, we installed an ASPEN 2000 (Pro PFD and MFD.)  The question I have relates to missed approach procedures at KOXC which is my home base.  The missed approach on either the GPS 18 approach or the ILS requires a climb (in the case of the ILS a left turn back)  to a waypoint south of the airport and then a hold at that fix.  When I load the approaches into the 540 all looks good.  When I enable the missed approach on the GPS 18 approach, I get the message "manual sequencing required" although I'm not sure what that means.  The box shows the course to the holding point properly in magenta and flies to it directly.  The problem arises in the entry to the hold in both approaches.  Instead of doing a parallel entry or tear drop on the protected side, it does a tear drop entry on the unprotected side of the hold.  The aspen depicts what I would expect and what the IFD540 simulator does.  I'm assuming this is some kind of pilot error but I have no idea what.  Any ideas from those who have been flying the box longer then me?
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MysticCobra View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MysticCobra Quote  Post ReplyReply Direct Link To This Post Posted: 10 May 2015 at 10:23am
This may not be your issue, but I noticed it in my plane so I'll mention it.

I had GPSS installed along with my 540.  The shop told me to always have my autopilot set to "HDG" mode when GPSS was engaged.  This made sense to me, because the whole purpose of GPSS is to "spoof" the heading error signal to drive the autopilot.

However, in practice, I noticed that the AP would sometimes "hunt" (steer back and forth) in HDG mode, whereas it would be glassy-smooth in NAV mode.  I couldn't tell any difference otherwise between the two settings, so I got in the habit of leaving the AP in NAV mode...

...until the day I was flying practice approaches and asked for a hold.  The AP was riding the magenta line just fine, until the hold entry.  For holds, the CDI is always showing the deviation from the inbound leg, and so having the AP in nav mode resulted in the AP being unable to fly the hold accurately.  The track in the sky looked like it ballooned out on the protected side, and extended beyond the normal hold length until I manhandled it around back on course.  Switching back to HDG mode (where I should have had it from the start) resolved the issue, as the AP was once again responding to the heading error signal alone, not a combo of the CDI and HDG error signals.


Edited by MysticCobra - 10 May 2015 at 10:24am
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PEFeinman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PEFeinman Quote  Post ReplyReply Direct Link To This Post Posted: 10 May 2015 at 11:27am
Mystic,

Thanks for sharing that.  Actually in my case, the autopilot(KFC200 with EA100 card for Aspen) flies exactly as the IFD540 tells it to fly as long as you are in hdg mode and don't activate appr mode until inbound or established on the final approach course.  The problem is simply that the IFD540 is giving it some weird entry that I have never seen.  It would be a perfect teardrop entry if the hold were left hand turns south of the waypoint.  It depicts the holding pattern on one side properly, but the entry it flies is on the unprotected side.  As I said, on the simulator app it depicts and flies it exactly as you would expect.  I really wish I understood why and what it was doing.

Best,

Phil
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Post Options Post Options   Thanks (0) Thanks(0)   Quote oskrypuch Quote  Post ReplyReply Direct Link To This Post Posted: 10 May 2015 at 12:49pm
I'd call technical support, they can run it on the bench, and maybe send a log dump. That might yield some clues.

* Orest

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KIM View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KIM Quote  Post ReplyReply Direct Link To This Post Posted: 11 May 2015 at 10:22am
Originally posted by MysticCobra MysticCobra wrote:

This may not be your issue, but I noticed it in my plane so I'll mention it.

...until the day I was flying practice approaches and asked for a hold.  The AP was riding the magenta line just fine, until the hold entry.  For holds, the CDI is always showing the deviation from the inbound leg, and so having the AP in nav mode resulted in the AP being unable to fly the hold accurately.  The track in the sky looked like it ballooned out on the protected side, and extended beyond the normal hold length until I manhandled it around back on course.  Switching back to HDG mode (where I should have had it from the start) resolved the issue, as the AP was once again responding to the heading error signal alone, not a combo of the CDI and HDG error signals.


And for those of us who do not have a GPSS for hold entry, next course (i.e. "tear drop entry course XXX") as CAS advisory would be great, as well as next leg ("next leg course xxx") after 1 min.


Klaus
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Post Options Post Options   Thanks (0) Thanks(0)   Quote chflyer Quote  Post ReplyReply Direct Link To This Post Posted: 11 May 2015 at 5:49pm
Originally posted by MysticCobra MysticCobra wrote:

This may not be your issue, but I noticed it in my plane so I'll mention it.

I had GPSS installed along with my 540.  The shop told me to always have my autopilot set to "HDG" mode when GPSS was engaged.  This made sense to me, because the whole purpose of GPSS is to "spoof" the heading error signal to drive the autopilot.

However, in practice, I noticed that the AP would sometimes "hunt" (steer back and forth) in HDG mode, whereas it would be glassy-smooth in NAV mode.  I couldn't tell any difference otherwise between the two settings, so I got in the habit of leaving the AP in NAV mode...

...until the day I was flying practice approaches and asked for a hold.  The AP was riding the magenta line just fine, until the hold entry.  For holds, the CDI is always showing the deviation from the inbound leg, and so having the AP in nav mode resulted in the AP being unable to fly the hold accurately.  The track in the sky looked like it ballooned out on the protected side, and extended beyond the normal hold length until I manhandled it around back on course.  Switching back to HDG mode (where I should have had it from the start) resolved the issue, as the AP was once again responding to the heading error signal alone, not a combo of the CDI and HDG error signals.


I'm not sure exactly what NAV means on your AP, but I've had an STEC 30 and GPSS connected to my old GNS430W. I'm just starting to get used to my new IFD540 so I might discover something different but I'm expecting it to work the same. In any case, one really needs to look at the specific GPSS docs how it and that AP are set up with the GPS unit. For example, the STEC GPSS manual states the following: "Conduct all GPSS operations with the AP in the HDG mode only. Selecting any lateral mode besides HDG (NAV,APR,REV,etc) will decouple the AP from the GPSS function.

The GPSS has 2 modes: GPSS and HDG. The STEC 30 AP has 4 tracking states: ST HD and LO/HI TRK(LO for enroute VOR use and HI for LOC use). ST is just a stable state (turn left turn right control), HD is heading, and TRK is for VOR tracking. In GPSS GPSS mode, the AP should be in HD(heading) mode as mentioned above. The GPS provides digital roll steering data (ground speed and bank angle signals) that the GPSS scales and converts to ac/dc heading error info that is fed to the AP. On the other hand, a heading system (HSI/DG) input is already in the form of ac/dc heading error info and the GPSS just forwards it to the AP. That is, if using a VOR/ILS for guidance to the exclusion of GPS overlay, then the GPSS switch should be in HDG mode and the AP should be in TRK mode. Heading bug needs to be used to drive AP through PT and Holds. If using GPS overlay, then AP should be in HDG mode and GPSS in GPSS mode and GPS signals are translated by it to look to the AP like heading bug adjustments.

Vince
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jrlumpp Quote  Post ReplyReply Direct Link To This Post Posted: 12 May 2015 at 10:14pm
I Noticed my Piper auto control auto pilot wandered left and right of the approach course in the heading mode with a Aspen 1000. I see I'm not alone in this issue. I didn't know if it's the Avidyne or the Aspen doing this. I plan to bring the plane back to the shop next week and test fly the auto pilot approaches with the tech guy. The Aspen didn't lose the needle, just didn't keep it centered.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Kentucky Captain Quote  Post ReplyReply Direct Link To This Post Posted: 23 Jul 2015 at 4:21am
Now I'm terribly confused.  We just went through a complete panel upgrade of which part is an Avidyne IFD 540, Aspen EDF 1000 Pro, and a S-Tec System 30 autopilot. I'm trying to figure out the HD and Hi_Trk modes and I seem to get different info depending on who I talk to.

During the test and acceptance flights I attempted to engage the autopilot in Hi-Trk mode while the IFD had an enroute flight plan. The autopilot commanded a turn away from the course every time.  Once back on the ground we were told that you always leave the autopilot in HD mode. That seemed to do the trick.

Last week I was working with the autopilot and flew a GPS approach with the autopilot in HD mode for the entire time.  All was fine until we got within five miles of the airport on final.  We started moving further left of the final the closer we got.  At 2 miles we were a full dot left of the centerline on the CDI.

I went home and read more of the manual and I read where it said that on an approach you are supposed to engage the autopilot in Hi-Trk mode once you are within +-1 degree of the final approach course.  I did that next flight and it seemed that we were a lot closer to the final than before but we ended up about 1/3 of a dot left of the CDI center this time at 2 miles.

Some mitigating factors.

There was a 10kt quartering tailwind from the right but I would think that would be compensated for.

Something else that I can't reconcile is that we were doing the GPS 20 approach to KBRY using the initial approach fix of ESSEV.  The IFD shows a course of 296 from ESSEV to OXVOR and a course of 206 while inbound from OXVOR on the final.  The approach plate shows a course from ESSEV to OXVOR of 295 and a course of 205 inbound from OXVOR on the final.  Why would there be a difference here?

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PEFeinman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PEFeinman Quote  Post ReplyReply Direct Link To This Post Posted: 23 Jul 2015 at 5:34am
I should have come back to the forum and posted the response I got from Avidyne.  As it turns out, the 540 needs baro corrected altitude to fly some published misses.  In other words, if the missed says Fly hdg xxx until reaching 1500 ft then make a left turn to 2,500 direct to xxx, the GPS needs a baro corrected altitude to know when it can proceed with each step.  That's all fine, but once I removed that very expensive altimeter that used to tell my KY297 when it reached the desired altitude in favor of the ASPEN evolution 2000 PFD/MFD there was no feedback to the 540 to give it that information.  There was a potential work around in wiring but I couldn't ask my avionics shops to go against the Aspen install wiring, instead we reached an agreement for the upgraded card from Aspen which provides that baro reading.  Fixed and working perfectly.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jack Seubert Quote  Post ReplyReply Direct Link To This Post Posted: 23 Jul 2015 at 9:58am

I received this from Tim McNany at Aspen on July 9th.  It looks like Aspens AOA has been approved by the FAA so this IM revision should be available to all Aspen dealers.


Jack,

 

The install manual was revised to Rev BB and it removed all the notes that would prevent anyone from being able to connect the PFD output to a GPS or other device.  It will not be released for a week or two as we need the AOA STC approval from the FAA.  Any dealer that has an issue with this can contact me in the meantime and I can explain the timing and the contents of the change.

 

Tim

There has been quite a bit of discussion in other IFD topics about this issue.  The long and short of it is that Aspen has removed all references to being prohibited from connecting to 2 data pins 26 and 27 with the ACU installed.  That means that you can get that baro corrected altitude from the Aspen without purchasing the ACU2


Any questions have your dealer contact Tim McNany at Aspen.

Jack 
Jack Seubert
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