Autopilot altitude hold

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Archive88
Airman First Class
Posts: 93
Joined: 01 Mar 2016, 19:08
Location: Washington state

Autopilot altitude hold

Post by Archive88 »

Have been flying this wonderful Comanche 250 for a long time. But now seem to have a problem when in Autopilot when I try to set altitude.
Flying straight and level in autopilot heading mode. When I punch the set the altitude button either on the panel or on the control column, the plane goes into a steep dive that I abort by once again punching the red (is it red? I think so or does that turn off the autopilot mode? Arggh!) button, cancel the hold altitude and bring the plane back to a level configuration. Not always. But dunno why or what makes this happen occasionally. I must be doing something wrong.

I don't know the correct terminology for the round panel autopilot gauge sitting just above the control column...the one that has the blue-green light at the left edge and that you push to move a white-yellow light along 3-4 selections to settle on the hold heading position. Sorry for the crude description. I had at one time a photo and direction for use guide, but alas, it has disappeared. Is there one available on-line? I need to refresh myself (obviously) on the various selections. And the correct name for this necessary gauge??
Sorry age is taking its toll.
Thanks, Archive88

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Nick - A2A
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Joined: 06 Jun 2014, 13:06
Location: UK

Re: Autopilot altitude hold

Post by Nick - A2A »

Hello Archive88,

Looks your whole post relates to the Comanche so I've moved this topic from the Bonanza forum.

The autopilot in question is the S-TEC System 30 and there's a link to the manual in this topic. (Direct link here).

I'd recommend you have a read and then get back to us if you're still having some problems with the altitude hold functionality. Probably the most important thing is to make sure the aircraft is properly trimmed before you engage alt hold. If you're still holding a fair amount of aft yoke pressure, press the alt hold button and then just let go of the yoke, a nose dive would not be an unexpected result.

Of course, this might not be the problem in your case, but in any case it won't hurt to refresh yourself with the autopilot operation from the manual as you mention.

Thanks,
Nick
A2A Simulations Inc.

Archive88
Airman First Class
Posts: 93
Joined: 01 Mar 2016, 19:08
Location: Washington state

Re: Autopilot altitude hold

Post by Archive88 »

Nick - you are correct, I need to review the S-TEC System 30 and, yes the aircraft involved is your Comanche 250 - my favorite aircraft.
Thank you for the courteous reply and link for the manual. I do check that the trim is in neutral...is there a way to actually 'set' trim to neutral without glancing out the window to see where the trim tab is sitting? I have been unaware of having any yolk pressure applied, but then...
Much appreciated.
Archive88

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Nick - A2A
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Posts: 13728
Joined: 06 Jun 2014, 13:06
Location: UK

Re: Autopilot altitude hold

Post by Nick - A2A »

Hi Archive,

Yes, the trim crank and trim position indicator in the Comanche are just above your head on the ceiling.

Thanks,
Nick
A2A Simulations Inc.

Archive88
Airman First Class
Posts: 93
Joined: 01 Mar 2016, 19:08
Location: Washington state

Re: Autopilot altitude hold

Post by Archive88 »

Nick:
Ah yes...how much has disappeared in the past year!
I now have the altitude hold conquered. It depends upon the timing. You must climb to preferred altitude, then select the ST button and activate the engage the altitude button on the control column, and then go to the lo track button to maintain heading. Then both altitude and heading are alive and well.
One final question, then I'll quit bothering you - is there a You Tube or other bit that explains the icons on the GNS 400 screen? I mean all those blue dots or red bits or light green lines that scrawl across the screen...not the clearly GPS heading lines or airfield icons. And not the buttons surrounding the central screen.
One can ignore them I suppose, but I would like to know what I'm supposed to know.
Archive88

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Paughco
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Posts: 2095
Joined: 30 Nov 2014, 12:27

Re: Autopilot altitude hold

Post by Paughco »

Here's a link to the manual for the S-TEC-30 autopilot: http://www.mikeg.net/hobbies/aviation/a ... Manual.pdf.

Say you're flying in your Comanche at your normal cruise altitude, and the airplane is trimmed out nicely, so that it maintains a pretty constant altitude "hands off." You turn on your autopilot master switch and give the autopilot a few seconds to warm up. You turn the heading bug on your HSI to your desired heading, then push the mode button twice to get HD mode and the Comanche will fly on the chosen heading. Then you push the altitude hold button on the control yoke and the autopilot will maintain altitude. You may get a beep and see an up or a down trim light, and you adjust the trim accordingly. You can change altitude by pressing the altitude hold button to disengage altitude hold, change power, adjust trim, or simply change pitch with the control yoke until you get the desired rate of climb or descent. Then, when you are at your new desired altitude, re-establish steady cruise speed and then re-trim the Comanche so she's flying at a constant altitude "hands off," and press the altitude hold button to engage altitude hold. Sometimes when you're flying over mountains you'll get a trim-up light on one side of a ridge then a trim-down light on the other side of the ridge.

Here's a link to the manual for the GPS 400: https://static.garmincdn.com/pumac/GPS4 ... sGuide.pdf. The map symbols are shown on page 2-6. If that's not the correct Garmin model, keep looking on the Internet - it's all out there. Also, there are plenty of YouTube videos that show how to use the standard FSX/P3D GPS, and all the add-on GPS units that are available.

Seeya
ATB
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Archive88
Airman First Class
Posts: 93
Joined: 01 Mar 2016, 19:08
Location: Washington state

Re: Autopilot altitude hold

Post by Archive88 »

atb
You guys are wonderful. And most patient with this Ancient Mariner - Got it now for the alt hold and heading.
And will review the GPS 400 material. I am familiar with usual Section maps and their icons/Legend, but the ones on the 400 do not seem to correlate.
Why do I constantly get Morse code blaring B-G-D (_.../__./_..) that I do not seem to be able to turn off? Sorry - that's actually another question.
-=Archive=-

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Jacques
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Joined: 26 Jun 2011, 17:54
Location: West Coast, USA

Re: Autopilot altitude hold

Post by Jacques »

That is the identifier morse code for the VOR (navigation aid ) you have actively tuned. There should be a small turnable and pushable button on your nav radio that says “ Pull ID/ Push BRG. You mouse over that and use your mouse wheel to turn it left and right, which adjusts the volume for the identifier. Its used to verify you have tuned the correct navaid. When you look at a navigation chart, you see that each VOR or VOR/DME has a frequency and a three letter identifier with the corresponding morse code in print. So listening to the morse code and comparing it with the information on your charts is one way to ensure you have tuned the correct VOR. Hope that makes sense!

I think I found a link to the radio manuals for the Comanche here: https://a2asimulations.com/downloads/ma ... Manual.pdf

Archive88
Airman First Class
Posts: 93
Joined: 01 Mar 2016, 19:08
Location: Washington state

Re: Autopilot altitude hold

Post by Archive88 »

Ah, OK, got that. will look for the magic adjustment. I am familiar with the identifiers for the VOR stations on the sectionals, but I have not been routinely flying via VOR - although I have recently been reviewing and adding it to the usual GPS nav aid - belt and suspenders. And I seemedto get the morse even with GPS, but maybe the Nav setting (which I generally ignore with GPS active) is actually the problem and is set to something that is triggering the Morse. Thank you, my friend.
Archive

Archive88
Airman First Class
Posts: 93
Joined: 01 Mar 2016, 19:08
Location: Washington state

Re: Autopilot altitude hold

Post by Archive88 »

Jacques:
Actually that is not the Nav aid type in the A2A Comanche. I find no audio volume control on the Nav panel. But I think I can handle the problem by manipulating the VOR.
Thanks.
-=Archive-=

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