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  #1  
Old 02-10-2019, 01:02 PM
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TJCF16 TJCF16 is offline
 
Join Date: Mar 2015
Location: Greenville SC
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Default Flying coupled approach

I have been practicing approaches with my autopilot and having difficult getting a stabilized approach. I have G3x touch and a Garmin 625 and Garmin 307 autopilot. I have tried flying 100 kts 90 kts, 80 kts. I ave tried all different flap settings. The problem is the autopilot will push the plane below the glide path then pitchís up to correct above the flight path. I can fly it by hand with no problem. I am sure it is a configuration setting that needs to be adjusted. I was wondering if anyone else has this kind of set up that can recommend configuration settings. This pitching and diving would not be ideal in the soup!
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  #2  
Old 02-10-2019, 01:09 PM
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Brantel Brantel is offline
 
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Default

Should be like it is on a guide wire. Send your log to G3Xpert and they will help you get it sorted.
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  #3  
Old 02-10-2019, 01:28 PM
sibriggs sibriggs is offline
 
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Default Pitch Gain settings

Review the G3x install manual about configuring the autopilot pitch torque and gain settings. I had to adjust mine after some issues and it fixed my problem.

Use the AUTOPILOT SETUP page to adjust the PITCH SERVO gain settings.

Steve
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  #4  
Old 02-10-2019, 01:33 PM
sibriggs sibriggs is offline
 
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Default Pitch setting

Additional info about the settings, I had to make my settings higher than the book default settings printed in the examples. Actually quite a bit higher, think each RV is unique and may or may not work with someone else's values.

Fly it, and take your time going through the procedure outlined in the manual top get the correct settings.

Steve
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  #5  
Old 02-10-2019, 01:47 PM
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Also, the settings required for the -9 are good bit different than the short wing RV's.
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  #6  
Old 02-10-2019, 06:25 PM
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airguy airguy is offline
 
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You likely need to tweak the autopilot settings - my Dynon autopilot will fly the RNAV like it's on rails. ILS will hunt a little above 95 knots, and VOR approaches I just hand fly rather than couple them because the corrections are all over the place.
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  #7  
Old 02-11-2019, 04:00 AM
RFazio RFazio is offline
 
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Location: LI, NY
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Default Maybe a bit slow?

Tim,

I fly coupled approaches in my 6 a lot. I have a Dynon system. I have found that in the RV6, 90 is a bit slow. To me, when I am trying to maintain 90 knots, the plane is like a boat just about on plane. You are heading down hill and it wants to speed up. You slow the engine and it slows, then too much. So you add power again. You speed goes up and down. I fly the approach at 110 to 120 knots, no flaps. Then as I get down to below 1000 ft or so AGL, I pull power, and then add flaps when I have the runway in sight. With these planes landing a little hot or long is not a problem. Iím still turning off most runways at the mid point. The plane is just so much more stable at 120 knots, itís one less thing to worry about. Like others have said I had to turn up my gain and sensitivity a lot also.

Another thing about RVs and auto pilots. Since the plane has such a broad speed range, setting the autopilot to work right at cruise means it might be sluggish at approach speeds. Setting it for approach speeds means it may be a little twitchy at cruise. I have mine set for approach speeds, 120 knots. And it is a little quick at cruise, but I like it that way.

RF
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  #8  
Old 02-11-2019, 08:53 AM
Latech15 Latech15 is offline
 
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I agree on the speed comments above. I set my engine at 1450 rpm. Fixed pitch. And no flaps. That stays at 100-105 on the glide slope. I just keep my eyes pegged on the tach and fidget with it to maintain 1450. Once you break out or hit mins, kill the AP and pull up and drop the flaps in.
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  #9  
Old 02-11-2019, 10:03 AM
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i will have the trim set up in level flight at say 130 kts. when i intercept glide slope i will throttle back to maintain 130 kts. trim stays the same. if the plane flys well in level flight it should do well on GS. when i finally start slowing down i know to trim up a bit at the same time. good luck.
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  #10  
Old 02-11-2019, 11:06 AM
lr172 lr172 is online now
 
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Quote:
Originally Posted by RFazio View Post
Tim,

I fly coupled approaches in my 6 a lot. I have a Dynon system. I have found that in the RV6, 90 is a bit slow. To me, when I am trying to maintain 90 knots, the plane is like a boat just about on plane. You are heading down hill and it wants to speed up. You slow the engine and it slows, then too much. So you add power again. You speed goes up and down. I fly the approach at 110 to 120 knots, no flaps. Then as I get down to below 1000 ft or so AGL, I pull power, and then add flaps when I have the runway in sight. With these planes landing a little hot or long is not a problem. I’m still turning off most runways at the mid point. The plane is just so much more stable at 120 knots, it’s one less thing to worry about. Like others have said I had to turn up my gain and sensitivity a lot also.

Another thing about RVs and auto pilots. Since the plane has such a broad speed range, setting the autopilot to work right at cruise means it might be sluggish at approach speeds. Setting it for approach speeds means it may be a little twitchy at cruise. I have mine set for approach speeds, 120 knots. And it is a little quick at cruise, but I like it that way. On low approaches, I tend to start slowing down after the FAF. Yes, it is harder to control at 90 knots than 130, but I don't need to deal with slowing down at low altitudes in the soup.

RF
I concur, but caution the need for practice. It is very easy to drop speed and set up when breaking out at 500+' but you don't want to learn how to do it on the gauges when breaking out at minimums. It is very doable, just requires a bit of practice. The needles get sensitive that close and increase the challenge of slowing down 40 knots.

Larry
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