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 25 AUTOPILOT-the only thread please (Read 72990 times)
audiohavoc
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Re: AUTOPILOT-the only thread please
Reply #90 - Apr 21st, 2011 at 2:05am
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I've tried distances ranging from 30nm to 60nm, unless there is a specified VOR changeover point on the airway.  I manage radial tracking very well with heading select mode, it would just be nice if I could get the autopilot to do it without wandering back and forth.  The strange thing is that when I manually align the radial and have the CDI centered, if I switch off HDG select and let VOR/LOC mode take over, the autopilot immediately deviates off the course.  It then starts wandering again to the left and right, obviously not keeping the CDI centered. Huh
  

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CoolP
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Re: AUTOPILOT-the only thread please
Reply #91 - Apr 21st, 2011 at 2:14pm
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Are you running gyro drift enabled in the FSX realism settings?
Maybe there's an offset between the indicated course and the real one and the AP then goes for the real one (internal FSX value) while you see the deviation on the CDI, because it shows you the offset value. This is just guesswork of mine though.
Would be a typical sim problem of course as real planes would always see the offset only on both systems.

I didn't have the 727 much on VOR to VOR enroute nav, only in the approach or departure phase where I was trying to follow some STAR and SID (which sometimes are described for the "old nav" too). I usually went for manual headings there though because she struggled with the short distances to the VORs when trying to catch the radials. Together with the slow AP turn rate, this really was some "chasing the needle" thing and isn't recommended.
So I just took the CDI to confirm my manual headings, not as primary source of driving the AP.
But your mentioned 30nm to 60nm sound very reasonable of course, she should work fine there.

Have to try this in some later flight I think.
  
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CoolP
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Re: AUTOPILOT-the only thread please
Reply #92 - Apr 21st, 2011 at 3:19pm
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I was just doing some circuits around Brisbane (a bigger town on the Isle of Mark  Cheesy) and can confirm quite some S-turn tendency. It gets better when the speeds go down, so VOR approaches as well as some <250kts SIDs and STARs shouldn't be a big problem, but when going fast, the AP really chases the needle.

The turn rates are slow, so he is doing corrections for quite some time to establish a Course.
I had real world weather on and felt much more confident when using the CDI for verification only, keeping all heading inputs manually (with the bug) or flying the whole thing with the AP off.

As my normal enroute Nav comes from the ("sissy"  Tongue) Civa INS, I usually don't run into trouble with this issue. The Civa turns are smart and right on time, corrections are done fast and with close to no overshooting.
If I would go VOR to VOR only, I'd tend to use the manual heading bug and get the wind readings from the Civa, to set up the wind correction course.
As said, approaches aren't a problem since the plane is slower and turns better then, so the AP can throw her around way better.  Cheesy
I've tried it around 210 knots, some flaps out and 3000ft when being within 15-8nm from the station. Worked fine. Even landed later, a bit hard though, but the crew remained silent until arriving at the gate where they ran away, screaming for help.


I remember the 707 to be way better on the VOR to VOR thing, only getting distracted by the cone of silence above the stations, but coming on the right Course pretty fast in between.
  
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audiohavoc
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Re: AUTOPILOT-the only thread please
Reply #93 - Apr 21st, 2011 at 4:35pm
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CoolP wrote on Apr 21st, 2011 at 3:19pm:
I was just doing some circuits around Brisbane (a bigger town on the Isle of Mark  Cheesy) and can confirm quite some S-turn tendency. It gets better when the speeds go down, so VOR approaches as well as some <250kts SIDs and STARs shouldn't be a big problem, but when going fast, the AP really chases the needle.

The turn rates are slow, so he is doing corrections for quite some time to establish a Course.
I had real world weather on and felt much more confident when using the CDI for verification only, keeping all heading inputs manually (with the bug) or flying the whole thing with the AP off.

As my normal enroute Nav comes from the ("sissy"  Tongue) Civa INS, I usually don't run into trouble with this issue. The Civa turns are smart and right on time, corrections are done fast and with close to no overshooting.
If I would go VOR to VOR only, I'd tend to use the manual heading bug and get the wind readings from the Civa, to set up the wind correction course.
As said, approaches aren't a problem since the plane is slower and turns better then, so the AP can throw her around way better.  Cheesy
I've tried it around 210 knots, some flaps out and 3000ft when being within 15-8nm from the station. Worked fine. Even landed later, a bit hard though, but the crew remained silent until arriving at the gate where they ran away, screaming for help.
http://img850.imageshack.us/img850/9162/parkingatbrisbane.th.jpg

I remember the 707 to be way better on the VOR to VOR thing, only getting distracted by the cone of silence above the stations, but coming on the right Course pretty fast in between.


Good post, thanks.  I a will take a look at the 707 autopilot section in the aircraft.cfg and compare it to the 727.  Perhaps the autopilot was improved in the 707.  I don't think I have gyro drift enabled, but I will check it out.
  

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audiohavoc
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Re: AUTOPILOT-the only thread please
Reply #94 - Apr 21st, 2011 at 4:38pm
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CoolP wrote on Apr 21st, 2011 at 2:14pm:
Are you running gyro drift enabled in the FSX realism settings?
Maybe there's an offset between the indicated course and the real one and the AP then goes for the real one (internal FSX value) while you see the deviation on the CDI, because it shows you the offset value. This is just guesswork of mine though.
Would be a typical sim problem of course as real planes would always see the offset only on both systems.

I didn't have the 727 much on VOR to VOR enroute nav, only in the approach or departure phase where I was trying to follow some STAR and SID (which sometimes are described for the "old nav" too). I usually went for manual headings there though because she struggled with the short distances to the VORs when trying to catch the radials. Together with the slow AP turn rate, this really was some "chasing the needle" thing and isn't recommended.
So I just took the CDI to confirm my manual headings, not as primary source of driving the AP.
But your mentioned 30nm to 60nm sound very reasonable of course, she should work fine there.

Have to try this in some later flight I think.


When flying SID/STAR procedures, I don't track radials unless they are specifically requested by the procedure; instead I fly using headings and I use DME to determine where I am on the chart.
  

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Re: AUTOPILOT-the only thread please
Reply #95 - Apr 21st, 2011 at 5:44pm
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Thanks CoolP! I did have gyro drift enabled, and with it disabled the 727 autopilot is tracking VOR radials much more precisely now.
  

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Re: AUTOPILOT-the only thread please
Reply #96 - Apr 21st, 2011 at 8:46pm
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Ah, I can tell you about some trouble with that odd sim gyro drift feature here, not on the 727 though.
This, for me, is one of the FSX items to remain off forever since it doesn't get the thing to be more realistic, but to be more buggy.  Grin
  
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Re: AUTOPILOT-the only thread please
Reply #97 - Jun 17th, 2011 at 8:17am
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On some pages it talks about a Block 5 autopilot, what is that???
Regards
Bjorn Smiley
  
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