Setting and Activating VS

[Guest Ron Freimuth]

>>Also, the decription of default_pitch_mode in the>>AircraftContainer SDK suggests that the FS2004 AP has a>>"PitchHold" function (value 1: maintain current pitch). IMO>>this is not implemented too.>>Oddly enough, while experimenting this afternoon, I did find>that at least in C, the AP ATT HOLD does work... ;)> ............. In fact, one can control AC pitch from the KB. I believe the K:Variables are also available. I found I could assign "Synch FD Pitch" to the KB. If the Autopilot is ON, then the FD pitch bar is set to the current AC pitch, and the pitch trim is servoed to hold that pitch. This pitch hold is more stable than the FS 'ALT Hold'. I have also assigned 'Change FD Pitch' to Ctl+ (increase) and Ctl- (decrease). Thus, I can change the AC pitch the autopilot holds from the KB. No doubt, 'FD Pitch' can also be changed in a gauge. Thus, I think 'FD Pitch' would be the K Variable to use to set the Pitch Command. By adjusting FD Pitch from the KB I can set VS near zero once I'm at the desired altitude. AC Alititude is less likely to hunt than if ALT Hold is set. However, one has to adjust FD Pitch regularly to keep altitude from drifting off the desired altitude. To disable the 'Hold FD Pitch' I have to hit Ctl-T. That returns pitch control to the KB trim. I think the FD Pitch is also returned to 0 deg. This also worked in FS2K, but there were no key assignments to increase/decrease FD pitch. I display 'FD pitch' in XML Test gauges so I can see the setting more clearly than on the FD bars. Observations of the FS ALT hold lead me to believe that ALT hold changes 'Hold FD Pitch' to the value that results in the set VS. Once near and at the set Altitude another feedback loop comes in that forces Pitch to the value that maintains VS=0. However, this Integration FB reduces the AC's pitch stability so many AC hunt in altitude. I have little doubt that one could synthesise improved Pitch, VS, and Alt control by simply engauging 'Hold FD Pitch' in a gauge. Then, varying 'FD Pitch' (pitch command) in an appropriate way. If there were a similar way to 'Hold Bank', one could also control Turn Rate and Heading more accurately. Ron

[n4gix 4,947]

> I have also assigned 'Change FD Pitch' to Ctl+ (increase)>and Ctl- (decrease). Thus, I can change the AC pitch the>autopilot holds from the KB. No doubt, 'FD Pitch' can also>be changed in a gauge.>> Thus, I think 'FD Pitch' would be the K Variable to use to>set the Pitch Command.Actually, it can be done Ron, and I posted the C code yesterday that shows how it may be accomplished.Like yourself, I did notice that using the Pitch Hold seemed much more stable and certainly responds much more smoothly than does using VS to control ascending and descending inputs.However, being constrained as I am to implementing the operational features of a specific real world autopilot, that isn't even an option for me to consider (unless cleverly hidden by programming magic)...On this AP, instructing the AP to ascend is as simple as dialing in the desired VS and pressing the selector knob. The a/c will immediately begin an ascent or descent as commanded, at the selected vertical speed, and will continue to do so until told otherwise... ;)

[n4gix 4,947]

>I tried AP_VS_VAR_INC but this doesn't work as it only pre>selects a climb rate - it doesn't engage the climb. Do I have>to deviate from the original autopilot and add a VS button as>well?You should be able to place all the needed code in your mouse event to initiate an ascent or descent using the same series of commands I've listed above (either in C or translated to XML>. Pressing the ALT button again would effectively cancel the VS mode for you, so you needn't worry about that at all.

[Guest adameke777]

Bill,Did you have a chance to check whether KEY_AP_ATT_HOLD_ON is functional only with AP ON ? Or does it work independently of the master AP switch ?Adam

[Varmint007 2]

I'm going to look into that method myself, Ron. Currently I emulate pitch hold very effectively by engaging or disengaging WING LEVELER after engaging ATT HOLD. The pitch command I need to emulate does not use VS, so I can get away with it. It simply captures the pitch at the time of engagement and holds it (although it could certainly be more responsive).But using the 'FD Pitch' may be a better option.--Jon

[Guest Ron Freimuth]

>I'm going to look into that method myself, Ron. Currently I>emulate pitch hold very effectively by engaging or disengaging>WING LEVELER after engaging ATT HOLD. The pitch command I need>to emulate does not use VS, so I can get away with it. It>simply captures the pitch at the time of engagement and holds>it (although it could certainly be more responsive).>>But using the 'FD Pitch' may be a better option.>--Jon Since 'FD Pitch' and 'AC Pitch' are A: Variables, one could also create his own 'L:pitch error,number' error and use it to control pitch trim. Which ultimately sets VS and finally Altitude. One could log and plot that L:Pitch Error variable to get a better idea of how the control loop is working. Ron

[phjvh 0]

Hi,Is there a Variable to see wether >K:AP_PITCH_REF_INC_DN>K:AP_PITCH_REF_INC_UP and>K:SYNC_FLIGHT_DIRECTOR_PITCH are in use?Btw. works perfect.Alt Hold seems to disable it.Jan"Beatus Ille Procul Negotiis"

[n4gix 4,947]

>Bill,>>Did you have a chance to check whether KEY_AP_ATT_HOLD_ON is>functional only with AP ON ? Or does it work independently of>the master AP switch ?It is only "functional" whenever the AP Master is on.I've posted the "final solution" in a new message ('cause it'd be buried in this thread!) ;)Thanks to everyone for their suggestions!

[nickpike 0]

Hi Bill, where is the "final solution"Had a search but no luck.I also suppose things are different in FSX now.cheers,nick

[n4gix 4,947]

>Hi Bill, where is the "final solution">Had a search but no luck.>I also suppose things are different in FSX now.>cheers,>nickOh goodness! I have no idea now, three years later... ;)I would suspect that it's either the same day or within a few days after this last post though...