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Changing Rate of Turn (autopilot) in FSX (Read 4280 times)
Aug 28th, 2010 at 8:45am

Savage   Offline
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Hi

Trying to brush up on my nav holds in FSX and using the autopilot to take me round.

Anybody know how to decrease the rate of turn on the autopilot so it's not quite so dramatic?  At the moment it's banking round at about 30deg.....was hoping for a more leisurely rate1 turn / 15 degrees or thereabouts.  Even in the sim world I feel like i'm spilling my drink.

Have assigned keys to <decrease/increase autopilot bank> but doesn't seem to do anything, but was hoping for a way to just set this up as standard so I'm not chasing the thing the whole time.

Thanks in advance!
 
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Reply #1 - Aug 28th, 2010 at 11:53am

olderndirt   Offline
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The idea is to maintain three degrees per second - your bank angle is based on airspeed.
http://en.wikipedia.org/wiki/ROT_(aviation)
 

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Reply #2 - Aug 28th, 2010 at 12:47pm

Savage   Offline
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That's the problem though.  I'm just in the C172, which at a moderate holding speed (let's call it 85kts) works out at 15-16degs angle of bank to achieve a nice standard rate one turn.

Of course if I flying it manually I would use the turn coordinator.

But trying to do the same with the Autopilot on and using the <hold heading> function actually pulls it round into more like a 30 degree turn.

Here's a screenshot (in this example I'm actually flying at just over 60kt....which should give me about 8deg turn for rate1)


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Bascically what I'm asking is if there is a config file somewhere that can be altered to just limit the actual angle of bank the aircraft will make.  At the moment it's entirely screwing up my nice 4 minute holds!




 
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Reply #3 - Aug 28th, 2010 at 5:22pm

olderndirt   Offline
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The AH and turn coordinator are showing way too much for that airspeed but the visual angle, out the windshield, looks about right.  Something's amiss, probably with the AP if the AH and TC are OK in a manual turn, but I don't know diddly about their .cfg.  If you have a similar plane with the same setup, a 177 or 182, see what they do under similar settings.  A glance at the default 172 acft.cfg reveals the autopilot max bank angle is 25.
 

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Reply #4 - Aug 28th, 2010 at 6:02pm

Savage   Offline
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Yeah - it's definitely not right.  I'll take a look to see if any of the other a/c do it....but at the moment the holds are taking 2 minutes as opposed to 4 because I'm achieving the base and turn to the inbound in about 20 seconds!

And in fact looking back at the map and my trace line I can see it's half the size that the racetrack should be.

Anybody know of a way to amend the config file?  Thinking that if I can force it to not bank beyond 15 degrees I'll have my answer (as I only really need to fly this one aircraft at this one speed in prep for my renewals in a few weeks).

Thanks
 
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Reply #5 - Aug 28th, 2010 at 8:15pm

olderndirt   Offline
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Just for laughs, make a backup of the acft.cfg then go in and change the max bank angle to fifteen - see what it does.  Other than killing time, what's your reason for a four minute turn - that's only half standard rate and, at your slow airspeed, may be outside the capabilities of that AP.  It'll bank that much with just gentle rudder input.
 

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Reply #6 - Aug 30th, 2010 at 1:32pm

Savage   Offline
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Ok - will give it a go.  Not tried amending a config file before, but I'm assuming it's just text I can overtype??

re: 4 minutes..that's actually the timing for the four minute nav hold (ie 1 minute outbound, 1 min turn, 1 min inbound leg and then 1 minute turn to the outbound again....a complete racetrack pattern).

You can achieve that turn from the inbound to outbound in exactly 1 minute, but ONLY if it's a Rate 1 (assuming nil wind also)...pretty standard - and indeed expected - for IFR stuff.

Also just waaay to fast for my fingers to get the OBS turned etc if the aircraft screams round in 20 seconds!

I'll let you know how I get on a post on here.
 
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Reply #7 - Aug 30th, 2010 at 8:26pm

olderndirt   Offline
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Your acft.cfg will open on notepad - be sure to back up the existing.  Scroll down to the autopilot section and you'll find the different specs.  Max bank angle=25 - just type your new value over the existing and end up with just the two digits.  When you 'X' out it'll ask if you want to save the changes - YES and you're good.  Nobody seems to be chiming in here so, if this doesn't help, PM 'Shane G'.  If he can't help, he'll point you at someone who can.
 

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Reply #8 - Sep 1st, 2010 at 9:38pm

Capt.Propwash   Offline
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when setting your Heading Hold, dont just jump to the heading that you are going to end up at.   take it slow on the dial and your turns will become more elongated.

if you are at heading 360, and you want to end up on 090, dont just crank the Heading Hold around to 090. (your plane will end up doing the 30-40* bank and you dont want that).  Instead, tell it to go to 020, wait till you are about 1/2 way through that turn then change it to 040, .. 060, ..080, 090.  This will cause your plane to not bank so hard through the turns.   yeah you have to mind the dial A LOT more, but if you want "lazy turns" this may be 1 way to achieve what you want without having to go digging through .CFG files just to change 1 line.   .. What will you do in the future if you want to go back to the 30-40* bank so that you can zip through downtown Dallas between the buildings??? you have to change the .CFG back... or, just crank it on the Heading Hold.
 

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