.air File Question Around Autopilot

[Guest Doug Moldenhauer]

Hi guys. I was wondering if anyone has any information around some of the parameters in the .AIR File regarding the Autopilot. I have a aircraft that I've been working on andI'd like to tighten up the Speed Hold mode. I assumed that FS2004 .AIR Files and FSX .air files must be simular as some of the planes from 2004 work in FSX.I found a section on the airspeed hold gains and rates in the .air file, but I've adjusted them from hell and back and I cant change the speed hold mode at all. I cant even make it worse. I started by taking readings while accellerating from 180kts to 250, and 250 to 180kts. I started making small adjustments but to no effect. I then made large changes and still no effect.I've been able to change other items in the .air file without issues, but this section doesn't seem to respond. Did they hard code the Autothrottle and speed modes or am I missing something?Any help would be appreciated.

[mgh 89]

Hi guys. I was wondering if anyone has any information around some of the parameters in the .AIR File regarding the Autopilot. I have a aircraft that I've been working on andI'd like to tighten up the Speed Hold mode. I assumed that FS2004 .AIR Files and FSX .air files must be simular as some of the planes from 2004 work in FSX.I found a section on the airspeed hold gains and rates in the .air file, but I've adjusted them from hell and back and I cant change the speed hold mode at all. I cant even make it worse. I started by taking readings while accellerating from 180kts to 250, and 250 to 180kts. I started making small adjustments but to no effect. I then made large changes and still no effect.I've been able to change other items in the .air file without issues, but this section doesn't seem to respond. Did they hard code the Autothrottle and speed modes or am I missing something?Any help would be appreciated.

In FS9 there are autopilot variables in the aircradft .csg file. Have you tried the effects of changing these?

[Guest Doug Moldenhauer]

In FS9 there are autopilot variables in the aircradft .csg file. Have you tried the effects of changing these?

Thanks for the responce mgh.....I've seen some of the autopilot variables in FSX in the aircraft.cfg, however there is no mention of gain, integral, or derivitivefor the autothrottle speed hold mode. I've seen these for other parts of the autopilot, but not this particular section.

[microlight 0]

Doug,There are lines you can add for these parameters, which don't seem to appear by default in the [autopilot] section of the aircraft.cfg, e.g.:nav_proportional_control=9.000000nav_integrator_control=0.250000nav_derivative_control=0.000000nav_integrator_boundary=2.500000nav_derivative_boundary=0.000000gs_proportional_control=9.520000gs_integrator_control=0.260000gs_derivative_control=0.000000gs_integrator_boundary=0.700000gs_derivative_boundary=0.000000You could try altering the groundspeed variables, and see what happens. :(

[mgh 89]

Thanks for the responce mgh.....I've seen some of the autopilot variables in FSX in the aircraft.cfg, however there is no mention of gain, integral, or derivitivefor the autothrottle speed hold mode. I've seen these for other parts of the autopilot, but not this particular section.

I understand that in FS9 some values only appear in aircraft.cfg if that aircraft actually has an autopilot. Have you check one of the more complex default aircraft?

[Guest Doug Moldenhauer]

"I understand that in FS9 some values only appear in aircraft.cfg if that aircraft actually has an autopilot. Have you check one of the more complex default aircraft?"I'll take a look...thanks :)

[rhagen 0]

Doug,There are lines you can add for these parameters, which don't seem to appear by default in the [autopilot] section of the aircraft.cfg, e.g.:nav_proportional_control=9.000000nav_integrator_control=0.250000nav_derivative_control=0.000000nav_integrator_boundary=2.500000nav_derivative_boundary=0.000000gs_proportional_control=9.520000gs_integrator_control=0.260000gs_derivative_control=0.000000gs_integrator_boundary=0.700000gs_derivative_boundary=0.000000You could try altering the groundspeed variables, and see what happens. :(

I believe the gs_* properties are for the glide slope. Are you referring to parameter(s) in the *.air file? I'd like to tighten up the speed hold too, if it

[Guest Doug Moldenhauer]

I believe the gs_* properties are for the glide slope. Are you referring to parameter(s) in the *.air file? I'd like to tighten up the speed hold too, if it

[rhagen 0]

...I've never seen any solution other than to adjusts the Autothrottle max rate ...

I've seen and tried that recommendation in the past too. When I came across this thread I've gotten my hopes up for some new information.Perhaps MS left the PID properties for the auto thottle out because it might function to the same degree as the helicopter governor PID...which is very poorly. For years the helicopter governor functioned poorly. When MS finaly provided the PID properties in the aircraft.cfg file it made no difference. As far as I know, no one has been able to tame it by modifying those properties.Ron

[Guest Doug Moldenhauer]

I've seen and tried that recommendation in the past too. When I came across this thread I've gotten my hopes up for some new information.Perhaps MS left the PID properties for the auto thottle out because it might function to the same degree as the helicopter governor PID...which is very poorly. For years the helicopter governor functioned poorly. When MS finaly provided the PID properties in the aircraft.cfg file it made no difference. As far as I know, no one has been able to tame it by modifying those properties.Ron

Thanks for the reply Ron. I'll keep searching the net and see if I can find anything, but so far I havn't seen anything with real meat to it other than rolling your own IAS/MACH Regulator. I didn't see anything describing how they did it other than it worked for them.I've never tried to program any gauges other than a few test ones from the SDK in either fs9 or 2002, I cant recall. I may just try to throw a simple PID together and try some testing. I havn't read about Sim Connect, but perhaps either that or FSUIPC will allow me to get at setting the throttle and reading the IAS/Mach for a stand alone test without having to create a gauge to test with. Not sure what the bandwidth of simconnect or fsuipc is, but seems like it should work as a stand alone. I'll have to see if I get time to play with it.If I find anything, I'll post here to keep others updated.

[n4gix 4,947]

Sorry I didn't catch this earlier...All of those PID entries in the aircraft.cfg file are used by AI aircraft only. They have no affect whatever on a user-flown aircraft.... :(

[Guest Doug Moldenhauer]

Sorry I didn't catch this earlier...All of those PID entries in the aircraft.cfg file are used by AI aircraft only. They have no affect whatever on a user-flown aircraft.... :(

I'm a bit new at this so thanks for that tidbit of info. I had not tried to tweak any of those yet. I guess that means that there are no knobsto turn regarding the autopilot in either the air file or the cfg file. That seems to shed light on why the professional stuff has their own autopilot.

[_Pv_ 0]

All the parameters mentioned above in the aircraft.cfg file are for approach only. They regulate the capture of the ILS and Glideslope. The items previously identified in the air file for AP control of specific gain functions no longer work in FS9/FSX. The best control is available by editing the aircraft.cfg file for the following:[autopilot]max_throttle_rate[TurbineEngineData]fuel_flow_gainstatic_thrustIt's VERY important that the many and complex engine settings in the air file be finely tuned. Best AP control over the engine(s) are obtained when the throttle/N2 ratio is correctly tuned to the engine power:1503, 1504The ratio of N2/N1 is correct:1502The total engine power for N1 is set for the range of Mach speed the engines produce:1506The inertia of the engine(s) are set to respond at the correct rate for the range of the engine power:1505 (note: this is NON-AFTERBURNING power)In addition, there is a global control over all the control input power response (ailerons, elevator, throttle) over the range of the aircraft's power:1525Hint: If you have trouble controlling the aircraft manually (this includes throttle/speed control) the AP/AT will have as much or more trouble than you.This is an indication the engine power and response curves are not set correctly for the expected performance limits of the aircraft.-Pv-

[n4gix 4,947]

All the parameters mentioned above in the aircraft.cfg file are for approach only. They regulate the capture of the ILS and Glideslope.

http://msdn.microsoft.com/en-us/library/cc...#PIDControllers

PID ControllersPIDs are only used to aid in the handling of AI (computer) controlled aircraft. PID stands for Proportional-Derivative-Integral controller, and is a feedback controller that takes an error for a controlled state and outputs a correction. For example, on an airspeed controller, the error would be the desired airspeed minus the current airspeed. The output is then determined by the sum of three factors using the error and the P, I, and D constants. The "P" factor is simply a factor proportional to the error. The "I" factor is an accumulated factor scaled by the error. The "D" factor is a factor based on the rate of change of the error."P factor" = P * error"Accumulated I factor" = "Accumulated I factor" + (I * error * deltaTime), in Calculus terms, this is simply an integral. The error must reverse its sign to drive this accumulated factor to 0. This is characterized as oscillations, but drives the error to zero."D factor" = D * error/deltaTime. As the error gets smaller, this drives the output to be asymptotic towards the desired value.

[mgh 89]

True but thecorresponding section dealing with the .air file has these entries:nav_proportional_control Proportional controller constant in lateral navigation modes. nav_integrator_control Integral controller constant in lateral navigation modes. nav_derivative_control] Derivative controller constant in lateral navigation modes. nav_integrator_boundary The boundary, or maximum signal error, in degrees in which the integrator function is active. In the example, the integrator is active when the error is between -2.5 and +2.5 degrees from the centerline of the navigation signal.nav_derivative_boundary The boundary, or maximum signal error, in degrees in which the derivative function is active. In the example, the derivative controller is not active because the maximum error is set to 0. I assume that ateral navigation modes cover all lateral modes, not just localiser, especially as there is a corresponding set of entries specifically for the glide slope.http://msdn.microsoft.com/en-us/library/cc...#mozTocId942782Is this helpful?