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Autopilot problem @16x-possibly solved


jb30284

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Hello all,

 

Im sure this has been addressed maybe already, but I have seen a lot of questions online regarding the oscillation that happens with fsx at 16x acceleration time. I just want to share the work around that I found to minimize this effect. Something, I'm not quite sure what, changed during the acceleration expansion and made this a problem.

 

Simply changing the autopilot settings to the following should reduce the oscillation greatly, and handling at lower speeds does not seem to be effected greatly. I did not come up with this on my own, and I cant remember exactly where I found this answer, but here it is, hope it helps: ***maybe a moderator can find a good "sticky" place to post this.***

 

[autopilot]

autopilot_available=1

flight_director_available=1

default_vertical_speed=1800

autothrottle_available=1

autothrottle_arming_required=1

autothrottle_max_rpm = 90

autothrottle_takeoff_ga=1

pitch_takeoff_ga = 8;

max_pitch=10.0

max_pitch_acceleration= 0.3

max_pitch_velocity_lo_alt=1.0

max_pitch_velocity_hi_alt=0.02

max_pitch_velocity_lo_alt_breakpoint=20000.0

max_pitch_velocity_hi_alt_breakpoint=28000.0

max_bank=30,25,20,15,10

max_bank_acceleration=1.8

max_bank_velocity=3.00

max_throttle_rate=0.10

nav_proportional_control=12.00

nav_integrator_control=0.25

nav_derivative_control=0.00

nav_integrator_boundary=2.50

nav_derivative_boundary=0.00

gs_proportional_control=25.0

gs_integrator_control=0.53

gs_derivative_control=0.00

gs_integrator_boundary=0.70

gs_derivative_boundary=0.00

yaw_damper_gain = 1.0

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It is not that unusual for APs to struggle at high X times. Pitch stability is largely a factor of the stability built into the model itself so is going to be plane specific.

 

Not knowing what the original settings for this plane where (what you changed) it's hard to be sure, but having worked with modeling extensively for many years, there is nothing in the settings above which affects aircraft pitch stability.

 

max_pitch_acceleration= 0.3

max_pitch_velocity_lo_alt=1.0

max_pitch_velocity_hi_alt=0.02

max_pitch_velocity_lo_alt_breakpoint=20000.0

max_pitch_velocity_hi_alt_breakpoint=28000.0

 

These settings mean the AP will be very reluctant to change altitude above 28K ft.

 

Your real problem is pitch stability, not AP altitude control.

I suspect your change result is circumstantial and your observation may have been more a result in the altitude or weather during your tests. Changing the AP's reaction to altitude changes required by pressure changes only masks the real problem in that the altitude change at high X triggers the pitch instability built into the particular model.

 

If you are flying in default FSX weather, these altitude change instability triggers are more of a problem due to the default Jeppeson station smoothing being very poor.

 

Also note that AP control settings are VERY specific to particular models and there are no single sets of settings which will provide correct AP control for every plane and the settings offered by your aircraft designer are those which were tested to provide the control expected of that plane's AP.

 

Personally, I do not fly more than 4X in most planes and when using increased X, I do so for only short bursts.

-Pv-

2 carrot salad, 10.41 liter bucket, electric doorbell, 17 inch fan, 12X14, 85 Dbm
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I think it's the matter of computing too much in too little time. If you're running fspassengers for example, flying like that would put you in serious negative score,but flying at X16 it doesn't even register the rough flight. I just put it to too much going on too quickly.

 

Sent from my E6653 using Tapatalk

Bart
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I have tried this with over 30 different aircraft. It seems to work fine, despite your misgivings regarding the aircraft specific flight tuning. Yes, there are fluctuations, but the main problem, the oscillation has been greatly reduced from a 1500 fpm climb/descent while at FL. As far as it being only a problem for certain aircraft, I have found that it does not matter what aircraft. Ever since the acceleration update, this has been a problem in every single aircraft I have ever used. It was not a problem in the base model (no sp1,2, or acceleration), nor previous versions. During my "tests", archaic as they were, the oscillation was overcome. The tests were devoid of weather or any "realism" settings, so that was not a contributing factor. All I know, for those of us that like to use the 16x speed once in a while, this is a good fix.
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Yes, maybe. So what exactly DID you 'change'? You can't expect these 'settings' to be good for both a Cessna and a 747 - that does not 'compute'.

 

Here are my observations:

(1). The 1800 fpm vertical speed should be 1200 fpm OR LESS for a Cessna.

(2). 'arming required=1'. If you don't have a switch on panel you are in trouble.

(3). 'max throttle=90'. The NEW setting for this is 110 (Google that too).

(4). 'damper gain=1'. Another 'red cod'. Aces left out a lot of specs when they quit FltSim coding. I am afraid this is one of them. Nothing but trouble here. Change to '=0'. Period!

(5). 16X in AP. Another Aces fiasco. Use 4X and quit 'fighting it' (Sim not having that capability). Reality sucks? Deal with it.

 

I am hoping you have many happy 4X flights. But it's up to you.

Chuck B

Napamule

i7 2600K @ 3.4 Ghz (Turbo-Boost to 3.877 Ghz), Asus P8H67 Pro, Super Talent 8 Gb DDR3/1333 Dual Channel, XFX Radeon R7-360B 2Gb DDR5, Corsair 650 W PSU, Dell 23 in (2048x1152), Windows7 Pro 64 bit, MS Sidewinder Precision 2 Joy, Logitech K-360 wireless KB & Mouse, Targus PAUK10U USB Keypad for Throttle (F1 to F4)/Spoiler/Tailhook/Wing Fold/Pitch Trim/Parking Brake/Snap to 2D Panel/View Change. Installed on 250 Gb (D:). FS9 and FSX Acceleration (locked at 30 FPS).
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Yes, maybe. So what exactly DID you 'change'? You can't expect these 'settings' to be good for both a Cessna and a 747 - that does not 'compute'.

 

Here are my observations:

(1). The 1800 fpm vertical speed should be 1200 fpm OR LESS for a Cessna.

(2). 'arming required=1'. If you don't have a switch on panel you are in trouble.

(3). 'max throttle=90'. The NEW setting for this is 110 (Google that too).

(4). 'damper gain=1'. Another 'red cod'. Aces left out a lot of specs when they quit FltSim coding. I am afraid this is one of them. Nothing but trouble here. Change to '=0'. Period!

(5). 16X in AP. Another Aces fiasco. Use 4X and quit 'fighting it' (Sim not having that capability). Reality sucks? Deal with it.

 

I am hoping you have many happy 4X flights. But it's up to you.

Chuck B

Napamule

 

In (4), I am guessing "yaw_damper_gain=1" which in FS2004 used to be either absent or equal to zero. I prefer yaw_damper_gain=1 for all A/C even if the panel doesn't use it.

 

I fly 16X in AP all the time (Heavy-Iron). No way I am flying YSSY-KDFW in real time.

 

The pitch oscillations beyond 4x can be damped in fine-tuning not in the autopilot.

 

Cheers,

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You are absolutely correct with what you said napamule2, but this is just an example of what can be changed to get you started. This is not an end-all use that should be written in stone. Of course there will be different settings for different classes, types, and categories of aircraft. Hmmmm, maybe that should be a pet project for me to start..... my recommended settings for this mod.....:pilot:
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jb,

Project? Why not start by compare of air file (auto pilot) sections for different types. But you will find that even if the 'model' or 'type' is the same, the air file (auto pilot) section entries will be different. Seems like some people like to change values just for fun not knowing what the heck they are tweaking. Who is to blame? MS and Aces are as even the default models are messed up. Their thinking seemed to be: 'Who is going to 'call' us about any 'wrong values'? More than likely no one will ever notice.' They found out better, but too late. So maybe start with the default models and then go on to similar models and compare (ie: reverse engineer). Me? I don't fly any default airplanes. I only use the 'Cessna 1xx' for my 'Default' flight (FS9 and FSX Accel) on initial load to set up the Sim. Then I switch to whatever I am flying at the time. It's time consuming to work on the flight model. But if you have a favorite (I have LOTS of those) you fix, mod, tweak, trade air files, and 4 hrs later you just got started. But it's what I do and love it. But sadly I don't share as the payware guys would snatch the FDEs and use them and they don't even give you credit. Homey don't play THAT game!!

Chuck B

Napamule

i7 2600K @ 3.4 Ghz (Turbo-Boost to 3.877 Ghz), Asus P8H67 Pro, Super Talent 8 Gb DDR3/1333 Dual Channel, XFX Radeon R7-360B 2Gb DDR5, Corsair 650 W PSU, Dell 23 in (2048x1152), Windows7 Pro 64 bit, MS Sidewinder Precision 2 Joy, Logitech K-360 wireless KB & Mouse, Targus PAUK10U USB Keypad for Throttle (F1 to F4)/Spoiler/Tailhook/Wing Fold/Pitch Trim/Parking Brake/Snap to 2D Panel/View Change. Installed on 250 Gb (D:). FS9 and FSX Acceleration (locked at 30 FPS).
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