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Interface with S-Tec-30

Postby recapen » Wed Mar 01, 2017 3:33 pm

I have my Mini-AP connected to my S-Tec-30 via the GRT ARINC interface to the S-TEC-30 ARINC interface through a switch that allows me to choose between the Mini-AP and the 430W.

The 430W recently replaced a 420W and the interface between it and the S-Tec-30 works very well.
The Mini-AP however does not work as well as I think it should...allow me to explain:

Using the Mini-AP Heading-bug mode (in a manner similar to the NSD-1000 HSI that the Mini-AP recently replaced), when I select a heading greater than 45 degrees (or so) away from my current heading, the commands from the Mini-AP to the S-Tec-30 provide for a standard-rate turn until the heading gets to within 20 degrees of the new selection - at which point the Mini-AP commands half-standard turn rate for about ten degrees - then takes an excruciatingly long time to close on the selected heading.

The NSD-1000 would command standard-rate turn to a smooth rollout within the last few degrees. Granted, this is using the analog heading mode of both the NSD-1000 and the ARINC interface for the S-Tec-30.

The 430W (when I perform a similar 45 degree course change) commands a standard-rate turn to a smooth rollout within the last few degrees. This uses the same ARINC adapter that the Mini-AP's ARINC adapter is attached to so I know that the 430W to S-Tec-30's ARINC adapter's ARINC signal stream can command the desired turn rate and rollout.

Since the ARINC interface is data-stream based, it seems as though the output from the Mini-AP adapter is not the same as the output from the 430W.

Anyone else running a S-Tec-30?
Anyone else experienced this with a different autopilot?
Anyone want to educate me on ARINC interfaces if my understanding is incorrect?

Thanks,
Ralph Capen
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Re: Interface with S-Tec-30

Postby GRT_Jeff » Thu Mar 02, 2017 1:35 am

For ARINC, the sender decides the exact roll angle. The Mini AP autopilot calculations are leveling out sooner than the 430W. Once it is under the standard rate, it is proportional to the remaining degrees to turn. The last few degrees shouldn't be extremely long. You could try increasing the heading gain, but make sure it does not oscillate.
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Re: Interface with S-Tec-30

Postby recapen » Thu Mar 02, 2017 12:59 pm

Thanks for the response - reinforced my understanding of the functionality was correct.
I have looked through the Mini-X manual (since there isn't a manual for the Mini-AP yet) but can't find any references on how to change the autopilot gain settings. Any instructions would be appreciated. I'll re-try after we figure out how to get my autopilot gain settings adjusted - to see if the settings change improves the performance.

Meanwhile, is there a way to submit a feature request to have the Mini-AP out put a roll rate more similar to the 430W?
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Re: Interface with S-Tec-30

Postby GRT_Jeff » Fri Mar 03, 2017 2:57 am

There is an introduction to the gains in the GRT Autopilot Installation and Setup manual. The gains that affect all autopilots (GRT or ARINC-429) are at the end of SET MENU, General Setup. The servo gains (any setting in the A/P Maintenance page) apply only to the GRT autopilot servos.

We don't have any information on how the 430W computes roll, but I will make a note that you want faster turns when you're near the selected heading.
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Re: Interface with S-Tec-30

Postby recapen » Fri Mar 03, 2017 1:22 pm

Thanks - I'll download the autopilot manual and give it a go this weekend.

I'll also be installing updated software for the Mini and AHRS that you just published.

Since I have multiple sets of equipment installed, is there a way to capture and record the ARINC streams coming from these devices? It might help in your analysis of matching the roll commands. I would be more than happy to connect some sniffers in line to capture the data streams. Helping in this way could benefit the entire user community.

Thanks
recapen
 
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Re: Interface with S-Tec-30

Postby GRT_Jeff » Sat Mar 04, 2017 6:52 am

The DEMO RECORD function records the ARINC-429 data received by the EFIS. If you have both ARINC channels connected (as would be used for GPS approach and GNAV modes) then the 430W's roll commands are included and would be recorded.
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Re: Interface with S-Tec-30

Postby recapen » Sun Mar 05, 2017 6:26 pm

Just got back from a flight after adjusting the Heading gain from 100 to 250. That did help - I'll try 300 on the next flight to see if that makes it closer to what I'm looking for. Also on the next flight I'll try the DEMO RECORD on the next flight as well - haven't read up on that one - hopefully, I'll be able to retrieve the data stream after shutdown...will it record an entire hour flight?! I have both inbound channels and the outbound channel hooked up on the ARINC box. I'll try to replicate some turns using both the VOR and GPS portions.

Thanks
recapen
 
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Re: Interface with S-Tec-30

Postby Bobturner » Sun Mar 05, 2017 9:47 pm

I have not done this for a while so I may be wrong on some details, but I think...
Data recording time is limited only by memory stick memory. As you fly along data is stored on internal EFIS memory. When that gets full it will download onto the memory stick (make sure you leave it in for the flight). During the downloading, maybe 30 seconds, no new data will be stored. So you'll have a few small gaps in the data. How many depends on how much data and how frequently you're sampling. After landing, make sure you push 'save' or 'record' (I forget the label) to write the last data batch to the stick, before powering down the EFIS.
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Re: Interface with S-Tec-30

Postby GRT_Jeff » Tue Mar 07, 2017 4:12 am

The EFIS does not save the DEMO RECORD data internally. It must be saved before powering down the unit. It also has a limited amount of memory for recording until the memory must be saved. On most systems this is not enough for an entire hour. You can stop and start separate recordings at any time, but the data from the previous recording must be saved before starting again.
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Re: Interface with S-Tec-30

Postby recapen » Tue Mar 14, 2017 1:28 am

Flew yesterday and captured a demo log file while performing two turns under autopilot control...

First with the Mini-AP commanding a turn via the HSI heading bug to the S-Tec-30 ARINC adapter...
Second with the 430W commanding a similar turn in the opposite direction via Direct-to to the S-Tec-30 ARINC adapter...

Since the output of the 430W goes to the Mini-AP, it should have recorded it as well.

I'll try to send them direct...

Thanks,
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