WP sequencing question

[Let'sgoflying!]

Let me ask you about a recent approach I did; maybe you have some ideas.
The autopilot did not take me where I thought it was going to and I am wondering what I did wrong or how I misunderstood the sequencing.
This is an older GNS-XLS; there are manuals (and simulators) online.
See plate below. (linked and; 1st pic)
At the blue dot (pic 2) I was cleared direct SUSIQ, expect the rnav10 - so I entered D-> SUSIQ and prepared the approach in the device but did not select it. There were only two options offered, CRATT or MOLLY, I did not see a difference so I chose CRATT but still did not select the approach in case atc had a change for me. (nb; SUSIQ was not offered as an IAF in the box)
In a few minutes, I was cleared direct SUSIQ, and cleared for the approach....somewhere at the small blue line drawn, (pic3) so I selected the approach and then went to the Direct page and chose direct SUSIQ, the one that was part of the approach. (pic4) I figured it is an IAF so the device should be happy with that and it should go to the wp and then do a teardrop entry with a 30° left turn then enter the hold. (pic5)
I have done this many times at other airports without problem.
Crossing SUSIQ, it began a right turn (pic 6) to the unprotected side of the hold even though SUSIQ was magenta as I approached it, then sequencing to WAREG as I crossed.
So I went to heading mode, completed the course reversal as drawn (pic 7) and it sequenced normally from there on in.
Why did it turn right?
Thanks!
http://www.airnav.com/depart?http://155.178.201.160/d-tpp/1513/09068R10.PDF

 

[aterpster]

Let me ask you about a recent approach I did; maybe you have some ideas.
The autopilot did not take me where I thought it was going to and I am wondering what I did wrong or how I misunderstood the sequencing.
This is an older GNS-XLS; there are manuals (and simulators) online.
See plate below. (linked and; 1st pic)
At the blue dot (pic 2) I was cleared direct SUSIQ, expect the rnav10 - so I entered D-> SUSIQ and prepared the approach in the device but did not select it. There were only two options offered, CRATT or MOLLY, I did not see a difference so I chose CRATT but still did not select the approach in case atc had a change for me. (nb; SUSIQ was not offered as an IAF in the box)
In a few minutes, I was cleared direct SUSIQ, and cleared for the approach....somewhere at the small blue line drawn, (pic3) so I selected the approach and then went to the Direct page and chose direct SUSIQ, the one that was part of the approach. (pic4) I figured it is an IAF so the device should be happy with that and it should go to the wp and then do a teardrop entry with a 30° left turn then enter the hold. (pic5)
I have done this many times at other airports without problem.
Crossing SUSIQ, it began a right turn (pic 6) to the unprotected side of the hold even though SUSIQ was magenta as I approached it, then sequencing to WAREG as I crossed.
So I went to heading mode, completed the course reversal as drawn (pic 7) and it sequenced normally from there on in.
Why did it turn right?
Thanks!
http://www.airnav.com/depart?http://155.178.201.160/d-tpp/1513/09068R10.PDF

Difficult to answer your question because SUSIQ should have been one of your three options when preparing to load the approach. It would then also have the course reversal holding pattern unless that navigator can't handle course reversal holding patterns.

 

[flyingron]

While I've not got experience with this unit, most of the pre-WAAS navigators will not enter course reversals on their own. You're supposed to SUSP it and do it on your own.

 

[Let'sgoflying!]

It does course reversal holding patterns; I have used it this way before.
It will cross the fix, then enter the depicted hold.
The box will say MAN or AUTO.
If you select Manual it will keep holding until you tell it to depart the hold.
If you select Auto it will pass the fix twice and proceed to the next approach wp.
There is no SUSP option that I have ever seen.

I am thinking the database is lacking SUSIQ as an IAF and that is the whole problem.
However, I am still wondering where it was planning to go.
I might have an opportunity to try it out in day vfr soon.

Thanks for looking over my question.

 

[olasek]

I am thinking the database is lacking SUSIQ as an IAF and that is the whole problem.

Could be.
I tried this approach the exact way you flew it on my G1000 trainer and there were no surprises. SUSIQ was available as one of the IAFs. The sim flew tear-drop reversal and then proceeded to WAREG. Had I wanted to stay in the hold pattern a bit longer I had SUSP button available.

 

[Let'sgoflying!]

Thanks
That is one of our regular destinations so I might not just drop it. I will look at it again tomorrow and if not happy might contact Honeywell about it. Er, whoever bought them.

 

[aterpster]

Thanks
That is one of our regular destinations so I might not just drop it. I will look at it again tomorrow and if not happy might contact Honeywell about it. Er, whoever bought them.

It is correct in the Jeppesen database and the Garmin database, the Jeppesen of which all the avionics vendors derive their databases from (except a few high-end avionics that use LIDO (German).

 

[olasek]

Why did it turn right?

The turn to the right could have been simply a turn that the software selected to sequence from SUSIQ to WAREG (if I understand you correctly after you passed SUSIQ WAREG became magenta). Say it had no concept of the 'safe' side it just flipped a coin and turned right heading to WAREG. It could be a useful experiment if you selected MOLLY or CRATT what would happen, would if fly the proper hold on its own in those cases?. If it did it would point to software limitation, your box requires you to fly it by the book, only from available fixes or bad stuff happens.

I made the following experiment in my G1000 trainer - I loaded your approach starting at CRATT but then I forced the sim to fly to SUSIQ direct. Result? It completely removed the hold from the flight plan and after crossing SUSIQ it made left (correct) 180 turn to WAREG. But the prescribed teardrop reversal wasn't done. As you can see a similar mechanism could be at play in your box and in removal of the hold the info about which side was safe was lost.