Arrow III autopilot
How does the autopilot work in the Arrow III? I've tried it and I'm no wiser, and haven't found anything on the web that I have understood (!). A very basic guide would be great - I'm starting on the very good YT guide, but the chapter on the AP is yet to come.
@clarkac Just to get some terminology out of the way:
Ok, so the engage switch (1) turns the A/P on or off, so that has to be on for AP to work first and foremost (though it's probably actually the last switch you touch when turning the AP on)
The heading switch (3) enables or disables heading mode. If this is ON, the AP controls the DIRECTION you fly. If this is OFF, the AP controls your ROLL only.
If AP is ON and the heading switch (3) is OFF, you can use the roll knob (2) to roll the airplane left or right. If the knob is centered, it either tries to keep wings level or simply gives no aileron input (i'm not 100% sure which tbh, though I think in the sim it just goes neutral aileron).
With the heading switch (3) ON, you now can use the coupler knob (4) to select the mode:
- The simplest is HDG mode, where the plane will just fly the heading selected by the heading bug on the HSI/DG.
- In NAV mode, the AP will follow a VOR radial or GPS path. Which one of these it follows depends on the current setting of the GPS (or if using the GPS100, the position of the GPS/NAV switch on the bottom-right of the left main panel). It will essentially try to keep the needle of the NAV1 or NAV2 instrument (use switch #5 to select between theses) in the center.
- LOC NORM mode (or simply LOC) is like NAV mode, but for localizers (used for instrument (IFR) approaches)
- LOC REV mode (or LOC BC) is used when flying on a localizer back course. In that case you get reverse sensing (needle to the left = you need to fly right), so this mode will correct for that.
- I'm not sure about OMNI mode, hopefully someone else can fill in what that is used for.
@n293wk Thanks, that's very helpful. I got this working - I mean following a heading - by selecting 'Omni' after selecting CDI on the GN750 and seeing 'GPS'.
@clarkac See here for Piper's AutoControl III B operating Instructions Manual:
Since you are making informative posts about the AP, I'm wondering whether you know anything a out the following problem:
I am unable to bind the “Heading hold” autopilot rocker switch to any keyboard key or joystick button for some reason.
Shouldn’t it be the “Heading mode ON” and “OFF” functions that I would expect to have to bind to? When I assign these functions, they work in every other plane except the Arrow - that switch doesn’t move unless I use the mouse!
The "altitude hold" switch works fine, no problem binding it at all. So why is the heading one differnt? Does that switch simply not correspond to the "AP heading hold" in other planes?
Has anyone managed to bind this heading hold switch to ON/OFF? Is it possible at all?
Would be really thankful for any hints!
(I’m not interested in the “toggle” version btw - I need ON/Off as I am trying to bind to a physical switch with 2 states. But as I said, I can't even bind it to keyboard key)
@bearsarecool Unfortunately idk how to help you there, I tried it myself and observed the same thing you said. I use SPAD.neXt to control LVars directly which works great.
I would recommend creating a support ticket though (https://support.justflight.com/support/tickets/new), they usually can help if there is a solution or if not they might add it in a future update
@n293wk Thanks, already created a ticket.
How can Spad.Next fix this problem though?
The problem is not between the device and the simvar, but between the simvar and the plane. Heading ON/OFF exist as simvars, but for some reason they dont have any effect on the plane.
Its the same for the NAV hold and the others too - only the toggle vars work (except alt hold, which doesnt even have an actual button)
@bearsarecool SPAD.neXt can control LVars directly, which exist at a lower level than simvars. Simvars are meant to be easier to work with, while LVars give developers more fine-grained control over aspects of the model. Also, simvars are generally more limiting to prevent people from messing things up, while LVars often don't have such protections and allow values to be set to whatever you want
@n293wk so is there a way in Spad of diagnosing which var is being used when i click the heading switch?
@bearsarecool This can be done with the in-game dev tools. With developer mode enabled in settings, open the console window and click the "Local Behavior" tab, and there will be a list of LVars that update in real time (those steps are from memory, so I apologize if they are incorrect). SPAD can show you the current state of LVars but it won't refresh until you reopen the window so viewing them in-game is much better
@n293wk I tried this but the console window doesn't have a tab called "Local Behavior", it just shows Errors/Warnings/Messages.
Do you perhaps mean the "Behaviors" window?
This one has a tab called "InputEvents", but for some reason it only contains three autopilot actions that just change the heading bug.
Do you perhapps know of any documentation that describes the feature you are talking about?
EDIT: I have tried Spad.Next event monitor but it's not helping at all. Apparently that the heading hold button triggers is: AP_HDG_HOLD_ON
But binding this event to a button on my throttle does not trigger the rocker switch (despite the fact that it IS "in theory" triggering the heading hold, which I can see on my multipanel, where HDG lights up). It makes no sense...
Hmmm… took a look at what mine was bound to as it works fine, event AP_HDG_HOLD. It does however seem to be a toggle, as setting it to 0 or 1 makes no difference.
There is supposed to be an lvar, L:AUTOPILOT_hdg but it doesn’t seem to be coming through spad for some reason.
@weptburrito I use
LVAR:AUTOPILOT_ONOFFfor the AP switch and
LVAR:AUTOPILOT_HDGfor the heading switch, setting them to 0 or 1 has the expected effect
@n293wk yeah, those are what I would assume as they are in the xml code for the switches, but spad isn't showing those to me. This isn't the first time I've had variables not showing up, I might need to reinstall spad or the lvar bridge.