GFC 500 Install Update

[donkaye, MCFI]

My install was finished last Tuesday. Flight tested it in the afternoon with light to moderate turbulence. I neglected to test one very important function; flying the airplane level for a few minutes.
 

On Wednesday and Thursday I flew the plane 8 hours from San Jose to Longview, Texas. Close to Bakersfield all of a sudden the plane went into a vertical oscillation of +/- 500 ft/min climbs and descents while maintaining a constant altitude, a real roller coaster ride. I just about cancelled the trip at that point because I thought I would have to hand fly the plane for 17 hours round trip. I turned the AP off, leveled the plane, and turned the AP back on. Somehow I was able to stabilize the plane to hold a constant altitude---for awhile. Then it was back to oscillating again. Over the 8 hour trip, this happened about 6 times. Additionally, it was guaranteed to happen anytime ATC had me change heading. The plane would start to turn in a 30° bank, the nose would go down, and the oscillating would start when the nose tried to go back to level.

It goes back to the shop when I get home, but I was wondering if anyone else has experienced this with the GFC 500? I'm probably one of the first installs on the Mooney Bravo. I had not flown the GFC 500 before, but there is one other irritating issue. On all heading changes, the plane leads the rollout by 20° from the selected heading and ends up almost level 10° early. It eventually eases its way to the correct heading, but not like the GFC 700 which rolls out perfectly on the correct heading. Have others experienced this, too?

Notwithstanding these important issues, the airplane is an entirely different airplane as compared to it with the KFC 150. Where the KFC 150 was abrupt in function, the GFC 500 is smooth as silk. The Yaw Damper addition was well worth the additional money, as we were hammered over New Mexico in the afternoon. That allowed me to test the function with and without the Yaw Damper. The difference was remarkable.

Another plus for me is the wing rock that I had with the KFC 150 is gone. When my issues are resolved, this will be an amazing addition to the plane.

(Posted to Beechtalk as well)

 

[donkaye, MCFI]

Just now, donkaye said:

My install was finished last Tuesday. Flight tested it in the afternoon with light to moderate turbulence. I neglected to test one very important function; flying the airplane level for a few minutes.
 

On Wednesday and Thursday I flew the plane 8 hours from San Jose to Longview, Texas for Don Maxwell's MooneyMAX 2019. Close to Bakersfield all of a sudden the plane went into a vertical oscillation of +/- 500 ft/min climbs and descents while maintaining a constant altitude, a real roller coaster ride. I just about cancelled the trip at that point because I thought I would have to hand fly the plane for 17 hours round trip. I turned the AP off, leveled the plane, and turned the AP back on. Somehow I was able to stabilize the plane to hold a constant altitude---for awhile. Then it was back to oscillating again. Over the 8 hour trip, this happened about 6 times. Additionally, it was guaranteed to happen anytime ATC had me change heading. The plane would start to turn in a 30° bank, the nose would go down, and the oscillating would start when the nose tried to go back to level.

It goes back to the shop when I get home, but I was wondering if anyone else has experienced this with the GFC 500? I'm probably one of the first installs on the Mooney Bravo. I had not flown the GFC 500 before, but there is one other irritating issue. On all heading changes, the plane leads the rollout by 20° from the selected heading and ends up almost level 10° early. It eventually eases its way to the correct heading, but not like the GFC 700 which rolls out perfectly on the correct heading. Have others experienced this, too?

Notwithstanding these important issues, the airplane is an entirely different airplane as compared to it with the KFC 150. Where the KFC 150 was abrupt in function, the GFC 500 is smooth as silk. The Yaw Damper addition was well worth the additional money, as we were hammered over New Mexico in the afternoon. That allowed me to test the function with and without the Yaw Damper. The difference was remarkable.

Another plus for me is the wing rock that I had with the KFC 150 is gone. When my issues are resolved, this will be an amazing addition to the plane.

(Posted to Beechtalk as well)

 

 

[ilovecornfields]

You’re braver than I am. I would have turned around at the prospect of hand flying for 17 hours (yes, I’m spoiled). Glad you made it safely.

I’m sure once you get it settled you will once again have the nicest panel.

I hadn’t realized how much I use the autopilot until my flight home from Henderson last week. I asked my son if he wanted to fly and he said “Why? It’s not like you even fly. You just let George do everything” I guess I should feel lucky that he looked away from his iPad long enough to insult my piloting skills.

Let me know if you need a ride back from the avionics shop.

[mike_elliott]

Paul Maxwell is opening up an Avionics shop, Don. While your there....just sayin....

 

[ArtVandelay]

Where does the GFC 500 get it’s altitude, I assume from the G5, via the CanBus. Did the G5 show any altitude changes? If you have dual G5s, power down the primary, see if problem persists.


Tom

[EricJ]

2 hours ago, ArtVandelay said:

Where does the GFC 500 get it’s altitude, I assume from the G5, via the CanBus. Did the G5 show any altitude changes? If you have dual G5s, power down the primary, see if problem persists.


Tom

If it oscillated around the proper altitude like he described, it isn't an altitude sensing problem, it's a control loop problem.    The loop damping went away for some reason and it started oscillating...it's a fundamental control loop issue.   Since the loop filters in the GFC are all software, it may be a configuration problem, but it's curious that it works sometimes and not others.   Maybe it's just not ready for prime time yet.

 

[carusoam]

MS history of APs and altitude challenges....

Often, a connection to the static system is involved...

Static system provides the best resource of stable alt data...

Recently MSers have found the rubber hose connecting the AP to the static system to be broken or missing...

Another MSer found a similar challenge with a Garmin AOAi that was not certified to be connected to the static system...

Check to see if the altitude data is properly connected to the static system...

Without it being connected, the data being generated can be a bit off causing other problems....

PP thoughts only, not an instrument tech...

Best regards,

-a-

[Emmet]

The GFC gets the altitude from the G5 - if the G5 shows the correct altitude it should not be the problem ...

[wcb]

On 6/8/2019 at 3:53 AM, ilovecornfields said:

You’re braver than I am. I would have turned around at the prospect of hand flying for 17 hours (yes, I’m spoiled). Glad you made it safely.

I’m sure once you get it settled you will once again have the nicest panel.

I hadn’t realized how much I use the autopilot until my flight home from Henderson last week. I asked my son if he wanted to fly and he said “Why? It’s not like you even fly. You just let George do everything” I guess I should feel lucky that he looked away from his iPad long enough to insult my piloting skills.

Let me know if you need a ride back from the avionics shop.

All I do is hand fly !!!! Come on Garmin and the FAA get the GFC 500 for the F!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[bradp]

@donkaye  Don did this get sorted out? 

[donkaye, MCFI]

1 hour ago, bradp said:

@donkaye  Don did this get sorted out? 

I'm sorry to say, No, not yet.

[mike_elliott]

Don, what is Andy's plane doing? Is the AP behaving, while yours is not? 

[donkaye, MCFI]

1 hour ago, mike_elliott said:

Don, what is Andy's plane doing? Is the AP behaving, while yours is not? 

I called him.  He says that in level flight he sometimes feels a little G force on the elevator from  time to time, but not the issues I am having.  I wish there were some other installs I could compare.  If it is not the install, and I don't think it is, while the G500 has potential, I can't recommend it until my issues are resolved.  It's unsatisfactory right now.  I've never had this experience with any GFC 700.  It's disappointing to say the least. I've apparently traded wing rock in HDG, NAV, and APPR, but stability in pitch in GPSS for pitch oscillation in all modes, definitely not a good tradeoff.

[201Mooniac]

47 minutes ago, donkaye said:

I called him.  He says that in level flight he sometimes feels a little G force on the elevator from  time to time, but not the issues I am having.  I wish there were some other installs I could compare.  If it is not the install, and I don't think it is, while the G500 has potential, I can't recommend it until my issues are resolved.  It's unsatisfactory right now.  I've never had this experience with any GFC 700.  It's disappointing to say the least.

Don, I should have my plane back from my install in two weeks and can let you know then how it handles in pitch.

[201Mooniac]

So it might be a little longer until I get my plane back as it turns out there is a small serial number range of the M20Js that have slightly different wing and access panel design.  It seems mine is one of that range where an access panel is slightly shifted and the nut plates are on the access panel, rather than the ring mounted to the wing.  Garmin is going to fit a new roll servo bracket design to my plane and get it added to the STC addendum drawings.  Hopefully this won't take too long.

[bradp]

On 6/19/2019 at 7:08 PM, 201Mooniac said:

So it might be a little longer until I get my plane back as it turns out there is a small serial number range of the M20Js that have slightly different wing and access panel design.  It seems mine is one of that range where an access panel is slightly shifted and the nut plates are on the access panel, rather than the ring mounted to the wing.  Garmin is going to fit a new roll servo bracket design to my plane and get it added to the STC addendum drawings.  Hopefully this won't take too long.

What year and SN are you? 

[201Mooniac]

3 hours ago, bradp said:

What year and SN are you? 

Mine is 1980 M20J 24-0938.  It seems M20Js before 24-1030 are slightly different than those that follow.  Garmin was out fitting a new bracket at my plane yesterday and they will be back to install and test the new bracket next week.  Expect to have it complete and approved in about another week or so.