Still cannot get DC-3 A/P to Engage?

[jagipson]

I downloaded the DC-3 most recently on April 3, and the A/P still doesn't engage...

I only got 3 download links and have used 2 already. Will X-Aviation reset my download links?

P.S. Ooops; make the Forum title "Still cannot get DC-3 A/P to Engage?"

Edited April 4, 2012 by jagipson

[Cameron]

Hi, there,

First off, yes! We will always be happy to assist you in a reset. You can contact us for such issues here: http://www.x-aviation.com/catalog/contact_us.php

We are usually very quick to respond to such inquiries...usually minutes.

As for this issue, can you please state what happens when you click to engage the autopilot? I had a customer write in yesterday with the exact same problem. Oddly enough, he quit X-Plane and restarted it and all went back to being well.

[jagipson]

I've cycled X-plane several times (and even rebooted) but the issue remains.

When I click the A/P master switch to the on position, it snaps immediately to the off position, simultaneously the red A/P engaged lamp flashes on for about 100ms, then off.

I'm not afraid of the shell, so if you need me to run a test or anything in the Gizmo console, just let me know.

[Cameron]

Hi, there,

The only other thing I can think of is a possible plug-in conflict here. Can you temporarily move all plug-ins with the exception of: shrink-wrap, gizmo, and plugin admin to a backup directory and then try again in sim? Should be a quick drag and drop for your plug-ins to test this...

[jagipson]

Can I engage A/P on the ground? (this may speed up troubleshooting).

[Cameron]

Can I engage A/P on the ground? (this may speed up troubleshooting).

You can, though I'm not sure it would be quite as effective.

This is a very simple test that should only require you to test once just to see if we have a plug-in conflict. The files you need to remove are in X-Plane/Resources/Plugins. The only plugins that should remain in that folder for this test are the one's I listed in my previous post.

[jagipson]

AAAhhhhhhhh HA!

The plugin removal had no effect; however, after trying all manners of switches, I discovered that the "Inverter" needs to be activated (Batteries/Generators aren't enough). Does such a primitive A/P really, really use AC power?

Edited April 5, 2012 by jagipson

[jagipson]

okay; suggestion time!

I searched all three manuals for "Inverter." No mention in the Autopilot manual or checklists. The POH only mentions that is supplies A/C power to "some systems." Wherever deemed most appropriate, having the words "Auto Pilot" and "Inverter" together in the documentation would have helped me earlier when I searched for "Autopilot" in an attempt to figure this thing out.

Also, since the A/P Engage lamp illuminates momentarily when the switch is clicked, 'it feels' like the system has power (but something else is wrong). I don't know what level of control plane authors have over the systems (I've only developed scenery (and in fact have one APT that is absolutely darling with the DC-3 parked on the apron - look up T82 - Gillespie County on the ORG)) but it would be nice (if not too much trouble) if the switch was allowed to stay in the "on" position (even with no power), but the light stays off (doesn't even flicker). Then if the inverter is turned on later (with the A/P switch still ON) the A/P engages. Probably not the best thing to happen when fiddling with switches, buy hey, if this is what would really happen, then why not?

[jagipson]

By the way, I reinstalled the plugins, they were not having any side effects. Just the inverter.

[karingka]

Most aircraft require the inverter to be on in order for the A/P to work.

[jagipson]

Most aircraft require the inverter to be on in order for the A/P to work.

Fooled me! Nothing else on the DC-3 seems to be tied to A/C power, and with the gyros being vacuum controlled, I can't image what the A/C power would be used for.

[karingka]

Oh well, now you know!

[jagipson]

The only electrical components are the power light itself, and possibly the pitch/yaw indicator. I just got off the phone w/ my father (who actually, yes, engineers and designs A/P systems and Avionics), and he confirmed this for a vacuum-driven Sperry A/P. The light could be either AC or DC, but if a servo/actuator is used to position the yaw/pitch indicator that would very most likely be A/C.

Edited April 5, 2012 by jagipson

[Goran_M]

When I made the flight model, I used several sources of documentation. One was a dedicated, traditional Sperry Autopilot manual which explains how the VACUUM powered Sperry works. However, the manual I used for the flight model in general is from an airline that has DC-3's that run an electrically operated Sperry Autopilot.

So, what I have decided to do is to take out the inverter and change the gyro's in the autopilot to vacuum powered. This will be updated and made available in the next hour or so, along with an ammended manual.

Apologies for the confusion!

[jagipson]

I'd love to see the documentation you have for the A/P. My father (again, Avionics Engineer) did mention that some very early Sperry A/P only use vacuum power. He mentioned that if electricity is used it would most likely be A/C and control the yaw/pitch feedback indicator; however, to me, it resembles an pneumatic one (but I'm certainly no expert). Which A/P is this one modeled after? The A-1? A-3?

Also, is it true that this A/P doesn't home (heading hold)? It looks like it should have pitch hold, yaw hold, and both a roll hold and a mutually exclusive heading hold. (Again no expert). It seems that the adjustable heading card below the DG acts only like a informational bug, which does not supply an input to the A/P. Is it strictly an informational bug, or is it really a heading input for the A/P HDG mode?

I don't know why I'm so interested. I guess it's because I've always been fascinated by the DC-3.

Thank you for your attention to this matter, and *very* nice job on this ACF.

[Goran_M]

The documentation I have, unfortunately, I am not allowed to share (for obvious reasons). I do have quite a bit of information spread across various manuals, but the main manuals I used were from a systems manual that had a very large section on the A-3 Sperry Autopilot and a general POH from QuebecAir's DC-3.

This autopilot does not turn the aircraft when selecting the heading. The lower, adjustable DG is used to select the heading you want to fly to, then you adjust the roll knob to turn the aircraft so the top DG (which is vacuum powered and indicates the aircrafts magnetic heading) is aligned with the bottom one. This lower, adjustable DG is linked to the autopilot and uses an autopilot "dataref". You can test this yourself by assigning a joystick button to the "Heading Up" or "Heading Down" commands in the "Joystick Keys and Equipment" menu under the "Buttons: Adv" tab in the "Autopilot" section.

As it lines up, return the Roll knob back to centre and follow the selected heading.

All 3 of these knobs act just like the control yoke, except they are a combination of custom programming and X Plane autopilot datarefs and are directly linked to the autopilot.

There are other Sperry Autopilots that have a heading hold function, a pitch hold function, and, IIRC, an ILS function, but I chose to keep it simple. We certainly could have made the autopilot with more functionality, like the A-5 which WAS electric, and we actually started doing that, but after discussing it, we wanted to keep it a bare bones autopilot that does the job and is easy to use.

[jagipson]

For all you panel builders out there, working on the classics:

Source: http://www.aviationancestry.com/

[alexcolka]

Hi,

What I do to get life easier (but not realistic) is to assign a keystroke combo (in my case shift+ctrl+h) to engage autopilot/heading with Sperry AP on and then adjust the DG to my desired heading and the plane turns to that heading very precisely. By the way a recommendation for a future update is to be able to reset the neutral position of the roll and yaw knobs with a click in the center area of the knob.

Thanks,