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How to use PFC A/T Disconnect? Setup?


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Hi Pete,

I have a PFC Jetliner console with the 737 throttle quadrant. My question is, how do I make use of the A/T Disconnect feature on the throttles?

The Jetliner console was rewired by PFC to support the 737 throttle quadrant. So I should be okay as far as hardware. They said the firmware fine, also.

When I'm flying with the Autothrottle engaged and I want to disengage it I press the "A/T Disconnect" button on the throttle lever, but it seems to set the speed bug to whatever my current airspeed is, rather than turn off the Autothrottle.

Do I need to do something in the PFC.dll setup? Or maybe FSUIPC? (I have the 737 quadrant selected in the PFC.dll.) My expectation is that the autothrottle would turn off, but still be armed because the arming switch is turned on. Is that correct?

Any help is much appreciated, as I haven't really explored this feature much yet.

Cheers,

Steve

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I have a PFC Jetliner console with the 737 throttle quadrant. My question is, how do I make use of the A/T Disconnect feature on the throttles?

The buttons on the outside of the two throttle levers? Press either or both of them, and the A/T disconnects. That's it. I have them on my Jetliner and in my 737NG cockpit.

When I'm flying with the Autothrottle engaged and I want to disengage it I press the "A/T Disconnect" button on the throttle lever, but it seems to set the speed bug to whatever my current airspeed is, rather than turn off the Autothrottle.

Really? It isn't programmed to do that. It sounds like you've re-programmed it (in FSUIPC?), though I've really no idea what function would do that, at least not consistently. What does the PFC driver say in its "Test" mode page when you press it?

What aircraft are you using it with in FS? Maybe it is a function of some add-on aircraft?

My expectation is that the autothrottle would turn off, but still be armed because the arming switch is turned on. Is that correct?

No. That isn't possible. In the real aricraft that arming switch would actually flick off when you pressed that button, but that needs a switch with an electromagnetic catch. It's one of the occasions (the A/P disconnect is the same) where some of your switches become out of sync. To re-engage A/T you'd need to toggle the A/T switch off and back on.

If the A/T disconnect has been re-programmed to operate the "speed" button then that might explain what you are seeing, though that would depend on what A/T mode you are using at the time, and probably on what aircraft you are flying. There are several A/T modes - Speed, Level Change and VNAV. No toggling of any of them disengages the A/T, only disengaging the A/T does that.

Regards,

Pete

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Hi Pete,

Here's a little more info. I can arm the autothrottle with the toggle switch to the left of the throttle quadrant and I see the autothrottle switch on the PM MCP flip up and the light turn green. Now if I push the A/T disengage switch on the side of the throttle levers, I see the autothrottle switch on the MCP switch very quickly turn off but then back on as I release the button.

If I try to press and release the A/T Disengage button very fast, maybe one in ten tries results in the A/T switch on the MCP turning off and staying off. But the rest of the time, it seems to do a quick toggle off and back on.

I think that might be why I've seen the speed bug reset a few time. As the autothrottle turns on again, it is setting the speed in the MCP to the current airspeed.

Anyhow, I hope that helps. Please let me know what you think. Is this some sort of timing issue? I know the A/T Disengage buttons are momentary switches..... It seems that as I press it, going low to high turns off the Autothrottle, but as I release the switch the state changes from high to low and seems to effectively turn on the autothrottle again.

On the test page, when I depress the switch it says:

9C 00 JetSwchs=00

When I release it it says:

9C 01 JetSwchs=01

Is there perhaps a setting somewhere I'm overlooking? I haven't reprogrammed anything. At least, not that I know of. ;-)

Cheers,

Steve

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On the test page, when I depress the switch it says:

9C 00 JetSwchs=00

When I release it it says:

9C 01 JetSwchs=01

Okay. I've looked into this, and those codes are wrong, and completely explain the problem. On my Jetliner the codes the A/T disconnect produce are:

Press: 9C 08

Release: 9C 00

Now, according to the PFC protocol documentation that code is supposed to be TO/GA, and I understand that's how the original throttles were labelled, but in fact they are now labelled (correctly) "A/T disconnect", and I've programmed the 9C 08 code as A/T disconnect.

In test mode, try your A/T Arm toggle switch. doesn't that also give you 9C 00 when off, 9C 01 when on? It does here.

The 9C 00/01 code IS the A/T arm switch as far as my driver knows. that's how it is documented.

So it looks like your button is wired to disconnect the A/T when pressed and reconnect it when released, exactly as if you flicked the toggle off and on. The driver cannot distinguish between identical codes.

Check the toggle switch. Maybe they've got the wiring mixed up? Either way you certainly have a need for hardware support from PFC. Sorry I can't help with that.

Regards,

Pete

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In test mode, try your A/T Arm toggle switch. doesn't that also give you 9C 00 when off, 9C 01 when on?

Yes. That is what happens.

Pete, what's the date on your firmware? When I power up the Jetliner console I get 04-14-2001 in the NAV1 window, which I assume is the firmware date.

Thanks,

-Steve

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On the test page, when I depress the switch it says:

9C 00 JetSwchs=00

When I release it it says:

9C 01 JetSwchs=01

Further to my previous replies on this, I've now done some additional investigations.

This is the story regarding the AT Arm toggle, the A/T disconnect button, and the TO/GA button.

When PFC first added the buttons on the outsides of the two 737 throttle levers they assigned them to "TO/GA", though this was of course incorrect -- the TO/GA buttons are mounted lower down, in a vertical position on the throttles.

Because it was more important to have the A/T disconnect buttons correctly working, I programmed the TO/GA buttons on the 737 quadrant for the Jetliner to operate A/T disconnect.

Then PFC developed a version for the 737NG cockpit. this featured both A/T disconnect and TO/GA buttons in their correct places on the quadrant. In the cockpit there is no A/T Arm toggle switch because, naturally, the arm switch on the MCP is used instead.

On this version of the quadrant and its control board the A/T disconnect buttons do the same as yours -- 9C 00/01. When the 737NG cokcpit is selected as the CONSOLE in my driver, these codes are interpreted as A/T disconnect and work fine. The TO/GA buttons produce the codes expected of them, and they work fine too.

So, it looks like your quadrant's A/T disconnect buttons are wired/connect as if they are the A/T disconnect buttons in a PFC 737NG cockpit.

I'm not sure how to resolve this. I've written to PFC but haven't received a reply yet, and I am on holiday after tomorrow until May 14th. If you are using an MCP with an A/T Arm switch, and don't mind losing the use of the toggle for it on the Jetliner, then I could possibly put in an option to treat the Jetliner 737NG quadrant like the console version. I cannot treat the A/T toggle and the disconnect buttons differently at all because they send the same codes.

Please see if you can arrive at a solution with PFC. If you still need this option in PFC.DLL when I return on May 14th, let me know.

Regards,

Pete

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