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Overriding the A/T servo in FLCH or VNAV

Started by Hardy Heinlin, Sat, 9 Apr 2016 06:42

Britjet

I'm pretty sure it goes to hold, but will check.
Peter

Britjet

#21
BA sim test last night. VNAV climb profile. Levelled at 3000ft in VNAV ALT using ALTSEL.
Selected 6000ft in ALTSEL. Pressed the ALTSEL.
VNAV SPD annunciation and throttles advance....

Restrict throttle movement, autothrottle servos don't give up, (in fact they make quite a noise!).
VNAV SPD remains annunciated..
No HOLD mode.

Peter


emerydc8


Will

Thanks for testing, Peter. So we seem to have different behavior in VNAV SPD and FLCH climb.
Will /Chicago /USA

Hardy Heinlin

#24
The FLCH related THR>HOLD override trick is now implemented in PSX 10.0.9-beta11:

http://aerowinx.com/board/index.php?topic=3685.0

emerydc8

Thanks Hardy. I'm looking forward to trying Beta 11.

Jon D.

emerydc8

Hi Hardy,

I'm sure this is an issue with my hardware or settings, but I'm not able to get the FMA to go to HOLD when I manually advance the throttles during a FLCH climb. I have the neutral position of the throttles set to 30. Would that have anything to do with it? Thanks.

Jon D.

Hardy Heinlin

You have to be more aggressive; keep moving into the opposite direction for 3 or 4 seconds.

But never mind. I want to modify this anyway with a true 8° difference check. Originally I didn't want to risk problems with homebuilt servos that may lag behind the commanded TLA.


|-|ardy

Hardy Heinlin

#28
Re-modified in beta13:

http://aerowinx.com/board/index.php?topic=3685.0


PSX users who work with servo hardware:

Please beta-test this modification. If this tolerance is too small for your servo system, I'll make it editable on the Preferences pages. Thank you!


Edit: It is now editable in beta14. But not on the Preferences pages. You need a text editor to edit your pref file.

emerydc8

Thanks, Hardy. I'll check it out.

Jon D.

Hardy Heinlin

#30
Quote from: emerydc8 on Sat, 30 Jul 2016 22:24
Hardy,
I found the pref file. I was looking in the wrong place. When I open my pref folder for the server, there are four folders--the default, two demos (left and right) and my own file that I call "visuals." I was looking in the visuals pref file--not the default. I went into the default pref file and replaced the 80 with 40 on TLA tolerance. Now, when doing the Asiana crash situ, it seems to be easier to get it to go to HOLD (I don't have to move the thrust levers as much).

But, I'm still having problems with getting it out of THR on a regular climb right after I press FLCH and move the throttles forward and manually override the servos. Here's the situ https://drive.google.com/file/d/0B-WRh0Hf7VdZQjVDWnNWYS1aRTA/view?usp=sharing

Looking at the virtual throttle position, it takes about a 2 index on the TQ to maintain the existing speed when the situ opens. I matched my actual physical throttles to the same position. When I set in 10,000 and press FLCH, all I have to do is advance the thrust levers to about 3.5 before it switches from THR to HOLD. But if I set in 6000' and press FLCH, I can advance the thrust levers all the way forward and it stays in THR. I'm not sure why there's a difference. Likewise, if I set 10,000, press FLCH and retard the thrust levers, it doesn't take much to get it into HOLD. But if I put 6000 in and press FLCH, I can pull power back to idle and it will stay in THR.

Jon

First of all: If you don't use servo hardware you need not edit anything.

40 is autoreset to 80. The allowed range is 80 to 999.

If you want a tolerance greater than 8° (80), you need to edit that pref file which your server uses. If it's not default.pref but whatever.pref, you need to load that in the latest PSX version and resave it, so that the latest PSX version can during resaving generate this line "FlchTlaTolerance=80" in whatever.pref.

The name whatever.pref in this forum post is just an example.

I don't have the problem you described. When I move the lever by more than 8° further ahead than the commanded TLA it goes to HOLD.

If the difference is less than 8° from present TLA to commanded target TLA, HOLD will not engage, for obvious reasons. There's also a 1 second delay included in the diff detector for stability reasons.

If you don't use servo hardware you need not edit anything. Just keep it at 8° (80). If you use an old pref file that don't has that line, the default will be 8° as well.


Regards,

|-|ardy

emerydc8

Thanks, Hardy.

I changed it back to 80. I see now that the file it opens on startup isn't the "visuals" file anyway -- it's the default pref file.

When I try a FLCH climb from 4000 to 6000, as soon as I press FLCH and it goes to THR, I can manually pull my throttles back to idle, then all the way forward, then all the way back to idle and then as I'm coming forward it goes to HOLD. Not sure why.

Jon

Hardy Heinlin

I now understand the problem. My modification only works for THR REF climbs and IDLE descents, not for 2-minute thrust settings after the A/T has set its target TLA somewhere between THR REF and IDLE. I'll have to develop a special algorithm for that case.

Your scenario should work if the diff is > 4000 ft.


|-|ardy

emerydc8

Thanks, Hardy. Actually, United744 mentioned that in another post and I found that if I make large altitude changes it does work. Is the logic set up to go to HOLD if I did, say, a descent from 10,000 to 4,000 but pulled the thrust levers back before the system actually went to HOLD?

Jon

Hardy Heinlin


emerydc8

Okay. I think I see what's happening. I can start a FLCH descent from 10,000 to 6000 and pull the throttles all the way back to the idle stops and it won't go to HOLD. But when I change the descent altitude to 5000, it goes right to HOLD when I pull the throttles back. So, the 10,000-to-6000 must be within the 2-minute window.


emerydc8


emerydc8

#38
Hi Hardy,

Two thumbs up on Beta 15. It goes to HOLD when I move the thrust levers more than about 1.5". Thanks again.

Jon

[EDIT]: I think I spoke too soon. If you do a small climb from 4000 to 6000, the FMA correctly goes to HOLD when you manually override the throttles in either direction, but the A/T servo doesn't disengage -- it will still set power.

Hardy Heinlin

It can't move the levers when HOLD is engaged. Do your USB levers vibrate?