GFC500 Update

[Bob - S50]

We've had our GFC500 for 5 days now and I've already flown with it a few times.  Here are some things we've learned:

1.  I was apparently wrong (what?!) about VNAV.  I thought TOD would calculate differently depending on whether I had NAV or APR selected.  I thought it would calculate to the FAF if NAV was selected and one fix before that if APR was selected.  Apparently that is not true.  We tried an approach that had a long level leg (RNAV 34 at KFHR).  We saw no difference in TOD location between having NAV or APR selected.  In both case it calculated TOD based on a BOD at the fix prior to the FAF.

2.  I was able to successfully trick the system yesterday.  I was flying the RNAV 4L at KSFF.  There is only a 200' descent in 7.6 miles between the FAF and the fix prior to that.  I didn't want to drive almost level for 7.6 miles so I created an along track waypoint 3 miles prior to the FAF and set a hard altitude equal to the FAF altitude.  VNAV planned my descent to cross that point just as I leveled off.  That let me keep my speed up (as requested by ATC) until I needed to slow down to configure.

3.  Apparently, if the FD is in PIT (pitch) mode, you cannot engage the autopilot.  I was just about to takeoff from KOLM and rather than push the TOGA button I pushed the FD button to turn on the flight director and pushed NAV for GPS navigation along my route.  That gave me annunciations of GPS FD PIT.  Above 800' AGL I tried to engage the AP but it would not come on.  I pressed the IAS button to change PIT to IAS and was then able to engage the AP.  I don't know if the same is true about ROL mode.

4.  The GTN 650 will not allow me to change an altitude constraint for the FAF.

5.  Prior to the GFC install, on the GTN, if I was tracking a course the airplane symbol and trend vector would both be aligned with the magenta line.  Now  with the GFC installed, the trend vector still lines up with the magenta line but the aircraft symbol shows the crab it is in to correct for crosswind.

6.  It only took me about one long flight to get used to the button pushing (knowing what to push/twist/roll).  Almost like being back on the 757 only different.

7.  Depending on how you work the altitude bug, you can make a non-precision approach pretty busy or pretty easy.

8.  I'm already loving it!

[donkaye]

6 hours ago, Bob - S50 said:

We've had our GFC500 for 5 days now and I've already flown with it a few times.  Here are some things we've learned:

1.  I was apparently wrong (what?!) about VNAV.  I thought TOD would calculate differently depending on whether I had NAV or APR selected.  I thought it would calculate to the FAF if NAV was selected and one fix before that if APR was selected.  Apparently that is not true.  We tried an approach that had a long level leg (RNAV 34 at KFHR).  We saw no difference in TOD location between having NAV or APR selected.  In both case it calculated TOD based on a BOD at the fix prior to the FAF.

2.  I was able to successfully trick the system yesterday.  I was flying the RNAV 4L at KSFF.  There is only a 200' descent in 7.6 miles between the FAF and the fix prior to that.  I didn't want to drive almost level for 7.6 miles so I created an along track waypoint 3 miles prior to the FAF and set a hard altitude equal to the FAF altitude.  VNAV planned my descent to cross that point just as I leveled off.  That let me keep my speed up (as requested by ATC) until I needed to slow down to configure.

With only 200 feet to descend, why not just fly level and fly into the GP a couple of miles before the FAF?

3.  Apparently, if the FD is in PIT (pitch) mode, you cannot engage the autopilot.  I was just about to takeoff from KOLM and rather than push the TOGA button I pushed the FD button to turn on the flight director and pushed NAV for GPS navigation along my route.  That gave me annunciations of GPS FD PIT.  Above 800' AGL I tried to engage the AP but it would not come on.  I pressed the IAS button to change PIT to IAS and was then able to engage the AP.  I don't know if the same is true about ROL mode.

4.  The GTN 650 will not allow me to change an altitude constraint for the FAF.

I found that no constraint that is part of an approach can be modified.   I guess that makes sense, since once the GP is intercepted the glide path to minimums has been determined.

5.  Prior to the GFC install, on the GTN, if I was tracking a course the airplane symbol and trend vector would both be aligned with the magenta line.  Now  with the GFC installed, the trend vector still lines up with the magenta line but the aircraft symbol shows the crab it is in to correct for crosswind.

I hadn't noticed that.  Will check the next time I fly. 

6.  It only took me about one long flight to get used to the button pushing (knowing what to push/twist/roll).  Almost like being back on the 757 only different.

7.  Depending on how you work the altitude bug, you can make a non-precision approach pretty busy or pretty easy.

8.  I'm already loving it!

I hope another Bravo near me gets the GFC 500 soon.  While I love the unit, and other people say it flys an approach "on rails", mine flys it on rails alright, but the rails are attached to a shallow roller coaster.  The same thing occurs with turns greater than about 30° of heading.  The pitch trim just moves too fast resulting in some pitch oscillations.   Maybe it's my installation but all cable tensions have been checked as correct.

[mike_elliott]

1 hour ago, donkaye said:

I hope another Bravo near me gets the GFC 500 soon.  While I love the unit, and other people say it flys an approach "on rails", mine flys it on rails alright, but the rails are attached to a shallow roller coaster.  The same thing occurs with turns greater than about 30° of heading.  The pitch trim just moves too fast resulting in some pitch oscillations.   Maybe it's my installation but all cable tensions have been checked as correct.

why not get with Andrew Rutherford, Don? Yea its a few miles north of you, but heck, you have a Mooney!

[donkaye]

35 minutes ago, mike_elliott said:

why not get with Andrew Rutherford, Don? Yea its a few miles north of you, but heck, you have a Mooney!

You're right, Mike.  I'll give him a call.  I did his transition training.

[mike_elliott]

14 hours ago, donkaye said:

You're right, Mike.  I'll give him a call.  I did his transition training.

.uhhhh, after I did

[Bob - S50]

9 hours ago, Bob - S50 said:

We've had our GFC500 for 5 days now and I've already flown with it a few times.  Here are some things we've learned:

1.  I was apparently wrong (what?!) about VNAV.  I thought TOD would calculate differently depending on whether I had NAV or APR selected.  I thought it would calculate to the FAF if NAV was selected and one fix before that if APR was selected.  Apparently that is not true.  We tried an approach that had a long level leg (RNAV 34 at KFHR).  We saw no difference in TOD location between having NAV or APR selected.  In both case it calculated TOD based on a BOD at the fix prior to the FAF.

2.  I was able to successfully trick the system yesterday.  I was flying the RNAV 4L at KSFF.  There is only a 200' descent in 7.6 miles between the FAF and the fix prior to that.  I didn't want to drive almost level for 7.6 miles so I created an along track waypoint 3 miles prior to the FAF and set a hard altitude equal to the FAF altitude.  VNAV planned my descent to cross that point just as I leveled off.  That let me keep my speed up (as requested by ATC) until I needed to slow down to configure.

With only 200 feet to descend, why not just fly level and fly into the GP a couple of miles before the FAF?

Technique only.  I want to minimize fuel burn so I want to stay at cruise altitude as long as I can.

3.  Apparently, if the FD is in PIT (pitch) mode, you cannot engage the autopilot.  I was just about to takeoff from KOLM and rather than push the TOGA button I pushed the FD button to turn on the flight director and pushed NAV for GPS navigation along my route.  That gave me annunciations of GPS FD PIT.  Above 800' AGL I tried to engage the AP but it would not come on.  I pressed the IAS button to change PIT to IAS and was then able to engage the AP.  I don't know if the same is true about ROL mode.

4.  The GTN 650 will not allow me to change an altitude constraint for the FAF.

I found that no constraint that is part of an approach can be modified.   I guess that makes sense, since once the GP is intercepted the glide path to minimums has been determined.

5.  Prior to the GFC install, on the GTN, if I was tracking a course the airplane symbol and trend vector would both be aligned with the magenta line.  Now  with the GFC installed, the trend vector still lines up with the magenta line but the aircraft symbol shows the crab it is in to correct for crosswind.

I hadn't noticed that.  Will check the next time I fly. 

6.  It only took me about one long flight to get used to the button pushing (knowing what to push/twist/roll).  Almost like being back on the 757 only different.

7.  Depending on how you work the altitude bug, you can make a non-precision approach pretty busy or pretty easy.

8.  I'm already loving it!

 

[k8n]

3 hours ago, donkaye said:

I hope another Bravo near me gets the GFC 500 soon.  While I love the unit, and other people say it flys an approach "on rails", mine flys it on rails alright, but the rails are attached to a shallow roller coaster.  The same thing occurs with turns greater than about 30° of heading.  The pitch trim just moves too fast resulting in some pitch oscillations.   Maybe it's my installation but all cable tensions have been checked as correct.

I recently had a GFC500 installed in my Eagle (also a long body - as you know). I have flown it about 5 hours with the new autopilot and have the same problem. The GFC500 works well overall, but there is a minor pitch oscillation while tracking the GP on an LPV approach. The airplane hunts up and down at 100fpm but stays right on the GP.  "Shallow roller coaster" is a great description for this. I have not noticed it when making heading changes while flying level.

[donkaye]

2 hours ago, k8n said:

I recently had a GFC500 installed in my Eagle (also a long body - as you know). I have flown it about 5 hours with the new autopilot and have the same problem. The GFC500 works well overall, but there is a minor pitch oscillation while tracking the GP on an LPV approach. The airplane hunts up and down at 100fpm but stays right on the GP.  "Shallow roller coaster" is a great description for this. I have not noticed it when making heading changes while flying level.

So maybe I'm not crazy.   It's going to take a lot more people to complain before Garmin is likely to look at it.  The issue in the turns is that with less than about 30° of turn, the bank angle does not go to the maximum of 30°, so the trim servo moves more slowly and can keep up with loss of lift of the wing.  With 30° of bank the nose will drop and the pitch trim servo starts overcorrecting back and forth.  If I hold the pitch trim wheel and override the servo, I can minimize the oscillations both in turns and on approach, but I shouldn't have to do that.   I've flown the J model and it flys both turns and glide slope perfectly.  Not so my airplane.  What makes the problem more interesting is that the GFC 500 will fly a multiple step-down VNAV profile perfectly without any oscillation.  While I love the GFC 500, I am disappointed in those idiosyncrasies.    I just can't complain to Garmin after they helped me so much last summer with an installation problem that fixed a major pitch oscillation problem in level flight.  I feel like they'd think I was crying wolf.

[Emmet]

Have you checked if this behavior is airspeed dependent?

The GFC trim speed can be adjusted according to airspeed.

[donkaye]

5 hours ago, Emmet said:

Have you checked if this behavior is airspeed dependent?

The GFC trim speed can be adjusted according to airspeed.

The settings per airplane model are fixed in stone.  I got into big trouble with Garmin when I posted that I had changed one of the settings, not realizing that was a big no-no.  Since extensive testing was done within the whole legal operating envelope of the airplane and at various airspeeds and altitudes, the ones given in the installation manual are the only ones permitted per the STC.  Changing them is not only illegal, but would probably nullify your insurance due to having a non airworthy airplane.

[bradp]

@Bob - S50 did you do the yaw damper? @81X your J has it correct? 

I got my two final quotes that I’ve been comparing.  Both 16.5amu for three servos no yaw damper.  Both shops say it’s not needed.  I wanted to ask your advice for a med body before I commit to my feet on the pedals or on the floor.  

[Emmet]

I completely agree and it makes a lot of sense, but it might be possible that your setting is incorrect (which you can check yourself) or that Garmin made a mistake and put a wrong value in the STC paperwork (which has to be checked by Garmin)

I did find an error in the drawings and they had a problem with the software of the G3X Touch which they fixed with 6.30  - so this is not completely out of scope...

[donkaye]

17 minutes ago, Emmet said:

I completely agree and it makes a lot of sense, but it might be possible that your setting is incorrect (which you can check yourself) or that Garmin made a mistake and put a wrong value in the STC paperwork (which has to be checked by Garmin)

I did find an error in the drawings and they had a problem with the software of the G3X Touch which they fixed with 6.30  - so this is not completely out of scope...

In addition to having the 2 stabilizing brackets missing on the pitch trim servo installation, there were a couple of settings that were not correct.  I went through all settings with the flight test pilot (in person) who did the Bravo certification, so I know they are correct.

[Emmet]

We spent more than 10 hours troubleshooting the abnormal disconnects with Garmin guys on the phone, swapping units, rechecking the installation etc. and all of a sudden the new software came out which fixed the problem ...

I am now very happy with the installation and the performance, but it was was very frustrating at the beginning.

[Bob - S50]

2 hours ago, bradp said:

@Bob - S50 did you do the yaw damper? @81X your J has it correct? 

I got my two final quotes that I’ve been comparing.  Both 16.5amu for three servos no yaw damper.  Both shops say it’s not needed.  I wanted to ask your advice for a med body before I commit to my feet on the pedals or on the floor.  

Yes, we did the yaw damper.  I haven't flown enough yet in turbulent air to see how much difference it makes.

If I subtract the approximately $2000 for KFC200 removal and new blind altitude encoder, our final cost was about $28,500 for dual G5's and 4 servos.

[Bob - S50]

I did some more thinking about VNAV and the point to which it is calculated.  I've decided that for the way ... I ... fly the plane, it doesn't matter.  Your mileage may vary, but here's why:

If the approach requires a descent of about 300'/mile during the segment terminating at the FAF, I'm going to need gear down anyway so I don't care to which point VNAV is calculated.  In either case, the point to which it is calculated won't matter because the descent gradient is steeper than my default gradient and it will make me cross the fix prior to the FAF at that fix's altitude constraint.

If there is a long relatively level segment leading up to the FAF such as the RNAV 4L at SFF or RNAV 34 at FHR I won't care either.  If it is taking me to the fix prior to the FAF, that's not what I want so I'll probably set an along track waypoint 2 miles prior to the FAF and set a hard altitude equal to the FAF altitude.  If it is taking me to the FAF, that's not what I want either because I want some time to slow down, configure, and get my act together prior to the FAF so I'll probably set an along track waypoint 2 miles prior to the FAF just like before.  Same thing.

So bottom line, I'll either need to configure one or more fixes prior to the FAF or I'll set an along track waypoint 2 miles prior to the FAF.  I'll make that determination based on approach plate study.

However, I do still have academic curiosity so if I'm looking for an excuse to go flying some day I may still go out and do some testing to try and determine how it decides which fix to use for VNAV calculations.

[donkaye]

8 minutes ago, Bob - S50 said:

Yes, we did the yaw damper.  I haven't flown enough yet in turbulent air to see how much difference it makes.

If I subtract the approximately $2000 for KFC200 removal and new blind altitude encoder, our final cost was about $28,500 for dual G5's and 4 servos.

The Yaw Damper operation is not well documented.  Actually it's not documented at all except to say, "not to be used on takeoff and landing".  I have rudder trim and fully trim it right on takeoff.  Since the YD can be turned on independently of the AP, after takeoff in the climb, I turn it on.  Since even with full right rudder trim some right rudder needs to be held on takeoff, when the YD comes on some torque is apparently generated by the YD servo to try and hold the ball centered. The YD operates with inputs from yaw rate, roll angle, lateral acceleration, and airspeed.  Changing to level flight changes the forces on the rudder.  I disconnect the YD, the rudder pedals significantly move having been held in place by the YD servo.  I trim the rudder for level flight and then turn the YD back on.  I figure this means minimal torque will be constantly held by the YD servo.  Periodically, I'll turn the YD off and then back on to check if extra torque is being held by the YD.  In level flight it is not.  I try to stay out of turbulence for passenger comfort through proper preflight planning, but have gotten into moderate turbulence from time to time.   While subjective, the YD does make a difference.  In the shorter body Mooneys I would think it would make even more of a difference, since the arm for the stabilizing rudder is shorter.

The extra cost of the YD is small in comparison to its benefits in my opinion.  Just know that, while it is not a rudder trim, it will try and hold the ball centered in the climb.  Therefore, when you transition to level flight, turn it off, stabilize the airplane, then turn it back on.  For those who are flying or have flown the big iron (@Bob-S50), I'd be interested in knowing how the YD is handled in those aircraft.  With the Citation, I just remember turning it on right after takeoff and off before landing.

 

[Ragsf15e]

2 hours ago, donkaye said:

The Yaw Damper operation is not well documented.  Actually it's not documented at all except to say, "not to be used on takeoff and landing".  I have rudder trim and fully trim it right on takeoff.  Since the YD can be turned on independently of the AP, after takeoff in the climb, I turn it on.  Since even with full right rudder trim some right rudder needs to be held on takeoff, when the YD comes on some torque is apparently generated by the YD servo to try and hold the ball centered. The YD operates with inputs from yaw rate, roll angle, lateral acceleration, and airspeed.  Changing to level flight changes the forces on the rudder.  I disconnect the YD, the rudder pedals significantly move having been held in place by the YD servo.  I trim the rudder for level flight and then turn the YD back on.  I figure this means minimal torque will be constantly held by the YD servo.  Periodically, I'll turn the YD off and then back on to check if extra torque is being held by the YD.  In level flight it is not.  I try to stay out of turbulence for passenger comfort through proper preflight planning, but have gotten into moderate turbulence from time to time.   While subjective, the YD does make a difference.  In the shorter body Mooneys I would think it would make even more of a difference, since the arm for the stabilizing rudder is shorter.

The extra cost of the YD is small in comparison to its benefits in my opinion.  Just know that, while it is not a rudder trim, it will try and hold the ball centered in the climb.  Therefore, when you transition to level flight, turn it off, stabilize the airplane, then turn it back on.  For those who are flying or have flown the big iron (@Bob-S50), I'd be interested in knowing how the YD is handled in those aircraft.  With the Citation, I just remember turning it on right after takeoff and off before landing.

 

Is there an annunciation that will come on if the yaw servo is holding a lot of rudder in for a long time?  The G1000/GFC700 Meridian I fly has electric rudder trim and yaw damper, however they are not connected.  Takeoff trim is 2-3 degrees right rudder.  When you transition from climb to cruise, you will get a trim caution until you trim it left.  I doubt they would just let the rudder trim servo sit there burning itself up?

Also, the Meridian has noticeable tail wag in a little turbulence with the YD off.  The YD makes it completely go away.  My midbody Mooney doesn’t have noticeable tail wag...  YD might be a tough sell for me.

[Niko182]

5 minutes ago, Ragsf15e said:

Is there an annunciation that will come on if the yaw servo is holding a lot of rudder in for a long time?  The G1000/GFC700 Meridian I fly has electric rudder trim and yaw damper, however they are not connected.  Takeoff trim is 2-3 degrees right rudder.  When you transition from climb to cruise, you will get a trim caution until you trim it left.  I doubt they would just let the rudder trim servo sit there burning itself up?

Also, the Meridian has noticeable tail wag in a little turbulence with the YD off.  The YD makes it completely go away.  My midbody Mooney doesn’t have noticeable tail wag...  YD might be a tough sell for me.

I cant wait til i get to the point in life where i need to compare my mooney to my meridian

[donkaye]

12 minutes ago, Ragsf15e said:

Is there an annunciation that will come on if the yaw servo is holding a lot of rudder in for a long time?  The G1000/GFC700 Meridian I fly has electric rudder trim and yaw damper, however they are not connected.  Takeoff trim is 2-3 degrees right rudder.  When you transition from climb to cruise, you will get a trim caution until you trim it left.  I doubt they would just let the rudder trim servo sit there burning itself up?

Also, the Meridian has noticeable tail wag in a little turbulence with the YD off.  The YD makes it completely go away.  My midbody Mooney doesn’t have noticeable tail wag...  YD might be a tough sell for me.

There's no annunciation.  The data can be downloaded off the G5, which records data on almost everything imaginable.  I've attached a sample file to show what I mean.  The manual rudder trim does not interfere with the YD.

DATA_LOG.xls

[ArtVandelay]

There's no annunciation.  The data can be downloaded off the G5, which records data on almost everything imaginable.  I've attached a sample file to show what I mean.  The manual rudder trim does not interfere with the YD.
DATA_LOG.xls

How do you get the G5 to log data?


Tom

[donkaye]

11 minutes ago, ArtVandelay said:

How do you get the G5 to log data?


Tom

Put a microSD card of up to 32GB in the microSD Card Slot.  Data will be recorded for each flight as you can see from my data file.

[ArtVandelay]

Put a microSD card of up to 32GB in the microSD Card Slot.  Data will be recorded for each flight as you can see from my data file.

I assume there is a secret setting or something to turn it on?


Tom

[Ragsf15e]

3 hours ago, Niko182 said:

I cant wait til i get to the point in life where i need to compare my mooney to my meridian

Well I just fly it, not mine.  It’s real nice, but my F model has more useful load left with full fuel, so there’s that.  I use to fly an F-15E, and I’d really miss that, except my F model fits the family much better and uses less runway.  All our planes are good...

[Bob - S50]

8 hours ago, donkaye said:

The Yaw Damper operation is not well documented.  Actually it's not documented at all except to say, "not to be used on takeoff and landing".  I have rudder trim and fully trim it right on takeoff.  Since the YD can be turned on independently of the AP, after takeoff in the climb, I turn it on.  Since even with full right rudder trim some right rudder needs to be held on takeoff, when the YD comes on some torque is apparently generated by the YD servo to try and hold the ball centered. The YD operates with inputs from yaw rate, roll angle, lateral acceleration, and airspeed.  Changing to level flight changes the forces on the rudder.  I disconnect the YD, the rudder pedals significantly move having been held in place by the YD servo.  I trim the rudder for level flight and then turn the YD back on.  I figure this means minimal torque will be constantly held by the YD servo.  Periodically, I'll turn the YD off and then back on to check if extra torque is being held by the YD.  In level flight it is not.  I try to stay out of turbulence for passenger comfort through proper preflight planning, but have gotten into moderate turbulence from time to time.   While subjective, the YD does make a difference.  In the shorter body Mooneys I would think it would make even more of a difference, since the arm for the stabilizing rudder is shorter.

The extra cost of the YD is small in comparison to its benefits in my opinion.  Just know that, while it is not a rudder trim, it will try and hold the ball centered in the climb.  Therefore, when you transition to level flight, turn it off, stabilize the airplane, then turn it back on.  For those who are flying or have flown the big iron (@Bob-S50), I'd be interested in knowing how the YD is handled in those aircraft.  With the Citation, I just remember turning it on right after takeoff and off before landing.

 

It's been over 4 years since I retired, but I don't remember having to turn on the yaw damper.  Either that or it was such a part of the normal flow that I didn't really have to think about it.  Never noticed any yawing in the DC9.  Worked pretty well in the 757-200 but not so much in the 757-300.  That plane was so long that the pilots could be feeling light turbulence up front and the back end would be whipping around so much that the flight attendants were experiencing moderate turbulence.  Sitting in the back and looking forward you could even see the fuselage bending and twisting.