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Topic: Slight off-topic: airplane autopilot speed control< Next Oldest | Next Newest >
Stanley
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Posted: Nov. 23 2016,14:47

Hi everyone,

This question pertains to FSX airplanes, not helicopters.  But people in Hovercontrol forums have been so helpful that I thought I could pose the question here.

Suddenly, on my Microsoft Boeing 747-400, the speed control in my default-supplied autopilot ceased functioning.  Everything else works, but not speed control.  The button won't light up when I press it or if I hit Ctrl-R.  And indeed I don't have auto speed control anymore.  It was working fine yesterday, but not today.

I didn't change any setting.

Along the same lines, I notice that a number of airplane simulators do not offer speed control.  Is there a setting on some file to activate speed control?  I guess the file would be the aircraft.cfg file, the *.air file, or the panel.cfg.  Or maybe some other file of which I am unaware.

Thank you.

Stanley


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Stanley
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Posted: Nov. 24 2016,17:18

Hi everyone,

Since posting my question regarding the airplane autopilot speed control (I have now learned that I should call it auto-throttle), I have done some research and made these two discoveries:

First, in the aircraft.cfg file, turn off "auto-throttle arming required" (that is, change its value from 1 to 0).  Doing so will ensure that the auto-throttle is always available.

Second, on any aircraft, you can always turn on auto-throttle by changing "auto-throttle available" from 0 to 1.

However, this has led to a few other discoveries and questions:

Yes, I can now always get the auto-throttle control to light up, but if the aircraft did not originally have auto-throttle available, just getting the control light to turn on does not actually enable auto-throttle.  So how do I enable it, or is doing so not possible?

And second, if you want to arm and then disarm auto-throttle, how do you do that.

Thanks.

Stanley


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PhantomTweak
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Posted: Nov. 25 2016,19:30

The default key combination to Arm Autothrottle is SHFT+R. To activate it, it is CTRL+R. Many assign the Activate command to a joystick key, just to make life easier. You can Arm it at a specific speed, then when you activate it, I believe it will hold that speed. If you don't Arm it, when you Activate it, it will hold the speed at the time of it's activation.
If you "turn autothrottle on" in the [Autopilot] in the aircraft.cfg, and the autopilot included with the aircraft has autothrottle coded in, autothrottle will function, whether the plane has it normally, or in real life, or not.
A simple edit of the aircraft.cfg [Autopilot] will do it. That's all it takes, depending on whether or not the autpilot called out in the Panel.cfg of the aircraft has it coded in.
Does that help at all?
Pat


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Stanley
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Posted: Nov. 26 2016,13:51

Hi Pat,

Thank you for your response.

So, as I understand the situation, I need to have these two lines of code in my aircraft.cfg file, and I can have them anywhere and in any order within the section entitled [autopilot]:

• autopilot_available=1

• autothrottle_arming_required=1

Furthermore, I arm the auto-throttle by pressing Shift-R and I activate it by pressing Ctrl-R.

Now, here is what happens.  If I press Ctrl-R Before I press Shift-R, then the auto-throttle light (that is the speed light) on my autopilot panel does not even light up when I press Ctrl-R.  However, once I press Shift-R, then when I press Ctrl-R the auto-throttle light does come on.

So far, so good.

But here is the big problem.  Even though the auto-throttle light comes on, it doesn’t work.  When I use the autopilot panel to change the speed, the speed of the airplane does not actually change.

Do you have any thoughts about this, please?

Stanley


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PhantomTweak
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Posted: Nov. 26 2016,19:28

It SOUNDS like, perhaps, the autopilot doesn't have the proper coding for Autothrottle, or, somehow, and I can't see how, we aren't utilizing it properly. Is there a checklist for THAT particular plane someplace? If so, is there a step we are omitting? Do you have to have the gear up, or the flaps at a certain setting? Do you have the throttles too far advanced for the AT to engage? I am just shooting in the dark here (which I have done more than a few times in The Corps. Looks awesome with tracers :D ).
Perhaps you are trying to set a mach number below 18,000', rather that knots of airspeed? IE: is the Mach button lit, when it shouldn't be?
Other than all that, yes, you have things correct.
Before it stopped working, did you add a plane that added a guage to FSX that replaces the default autopilot with a different one? One that works differently somehow? If so you will have to put the FSX default autopilot into the 747's ppanel folder, so it uses that one rather than the replacement in the Gauges folder.
You need to have the two lines you listed in the [autopilot] section.
You also need the line autothrottle_available          = 1 If that got changed to a 0 somehow, or the line was deleted somehow, the AT won't work any longer.
Anywhere therein is perfectly acceptable. So if they aren't there you can just add them to the bottom, for example.
And you also have the key-combo usage correct. You have to arm the AT before you activate it, with the line autothrottle_arming_required=1 in the autopilot section. If it's a 0, you can just hit ctrl+r, and it will activate.
A possible thought: Do you have a plane in your hangar with a similar autopilot in the panel? Or one that calls out the same autopilot in the panel.cfg file? If so, try either comparing the [autopilot] section of the aircfraft.cfg in the plane where it works correctly to the [autopilot] section of the one that doesn't. There may be a line in the one that works missing from the one that doesn't. OR, after making a backup of the aircraft.cfg of the plane where it doesn't work, copy the entire [autopilot] section out of the one that works' aircraft.cfg into the one that doesn't, then test it and see what happens.
Finally, you can try replacing the entry in the plane that doesn't work correctly's panel.cfg that calls the autopilot with the line from the panel.cfg in a plane where it does work. There may be a missing entry in that line in the plane that doesn't work.
Again, shots in the dark, but these are all things I would try in a similar circumstance.
I almost never use autopilot, or fly big iron, so...
I do hope we get this settled out and working properly for you :)
Pat&#9786;


Edited by PhantomTweak on Nov. 26 2016,19:43

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Stanley
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Posted: Nov. 26 2016,20:48

Hi Pat,

Thanks for your reply.

I will take another look at things against all of your helpful recommendations, and try to see if I can determine what's happening.

Meanwhile, I have another question, and I am going to post a new topic right below in a few minutes.

Stanley


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PhantomTweak
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Posted: Nov. 27 2016,05:49

I hope something in all my rambling helps :D
I saw your other post, and couldn't keep my nose out of that one too :D
Good luck!
Pat&#9786;


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PhantomTweak
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Posted: Nov. 27 2016,05:51

I hope something in all my rambling helps :D
I saw your other post, and couldn't keep my nose out of that one too :D
Good luck!
Pat&#9786;


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Stanley
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Posted: Nov. 29 2016,14:53

Pat,

I am still not solving this problem that I am having with the auto-throttle.

I would like to eliminate one thing.  Is there any setting in the *.air file that I need to look at?

Thanks.

Stanley


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PhantomTweak
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Posted: Nov. 29 2016,19:34

Short answer: No.
Slightly longer answer (for me anyway): The IS an autopilot section you can tweak in the .air file, but I would leave it for now. aircraft.cfg [autopilot] section overrides the settings in the .air file.
If you like, later on, we can go over the [autopilot] section of the aircraft.cfg file line by line to see if there is an error someplace.
Pat&#9786;


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Stanley
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Posted: Nov. 30 2016,03:56

Hi Pat,

I have been working on this quite a lot today, and I thought that I may have figured something out, but now I am not sure.

I had come to the conclusion that, to get the auto-throttle to work, I first needed to de-acativate it, then de-arm it, then re-arm it, and then re-activate it.

Sometimes when I did this, then the auto-throttle seemed to respond to my commands.  But it is not working consistently.

I really appreciate the help that you have given me.  Believe me, it has been immensely helpful.

Don't feel obliged to do this, of course, but I have copied the auto-pilot section of my aircraft.cfg file.  If you want to take a look at it, please do.

Here is the code:

[autopilot]
autopilot_available = 1
flight_director_available = 1
default_vertical_speed = 1200
autothrottle_available = 1
autothrottle_arming_required = 1
autothrottle_max_rpm =  1000
autothrottle_takeoff_ga = 1
pitch_takeoff_ga = 8
max_pitch_velocity_hi_alt = 1.5
max_pitch_velocity_lo_alt_breakpoint = 20000
max_pitch_velocity_hi_alt_breakpoint = 28000
max_pitch = 10
max_pitch_acceleration = 1
max_pitch_velocity_lo_alt = 2
max_bank= 35
max_bank_acceleration = 1.8
max_bank_velocity = 3
max_throttle_rate = 0.1
nav_proportional_control = 9
nav_integrator_control = 0.25
nav_derivative_control = 0
nav_integrator_boundary = 2.5
nav_derivative_boundary = 0
gs_proportional_control = 15  //9.52
gs_integrator_control = 0.26
gs_derivative_control = 0
gs_integrator_boundary = 0.7
gs_derivative_boundary = 0
yaw_damper_gain = 0
use_no_default_bank=1
use_no_default_pitch=1
default_pitch_mode=0
default_bank_mode=0

Stanley


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PhantomTweak
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Posted: Nov. 30 2016,19:51

Just at a quick glance, 2 things jump out at me.
First, the line yaw_damper_gain = 0 should read yaw_damper_gain = 1.0. Important to have the yaw damper work properly in FSX.
Second, the line autothrottle_max_rpm =  1000 should be autothrottle_max_rpm =  100. I am not certain what the effect that the extra 0 will have, but I know it's not right. That tells the AP what the maximum throttle setting may be. If you set it to 100, then the throttles may be moved up to maximum, ie 100%, by the AP. You can't set the throttles to 1000%, and may be confusing the system. Most tube-liners usually set it to 90%, but 100% is, obviously, the maximum throttle setting you can have.
I don't see any other glaring errors, but I will look over it more carefully as I have time.
Hope that helps a little bit...
Pat


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Stanley
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Posted: Nov. 30 2016,20:36

Hi Pat,

Great information.  Thank you so much, as always.

Stanley


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Stanley
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Posted: Nov. 30 2016,21:31

Most interesting.  The auto-throttle is beautifully response down to 240 knots, but not below that.  For example, let's say that I am flying at 320 knots.  I then set the AT to 150 knots, and the speed quickly and responsively starts decreasing to 240 knots -- but then it stops at 240 and will not go lower.

What is going on?


Edited by Stanley on Nov. 30 2016,21:58

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