Garmin G5 & Flat (non-vertical) Panel

[CalebH]

EDIT: Problem Solved

Leveling the airplane and re-running the calibration worked. See my comment at the bottom of the string for more details. 

 

Hi all,

Question for those of you who have installed Garmin G5s. We're wrapping up an avionics install with our A&P-IA that includes dual G5s and after following the pitch calibration procedure based on the level position of the airplane (rivets above tail-section access) we end up maxed out on the G5 in pitch offset with the G5 still showing around 2.5 deg. nose down in level cruise flight. Was reading through the Garmin manual again and it seems that 15 deg. is the max pitch offset that's allowable. For reference, our panel is flat (no step) and we did not add spacers to make the pilot side vertical - it just looks better when it's the same all the way across IMO.

Have any of you successfully done G5's with a flat panel without changing the angle of the entire panel? I could have sworn I'd seen some airplanes set up like ours... I'm really hoping we're missing something, but it's looking like we're going to have to tilt the pilot's side to make up for the 2.5 degs. we can't get with the G5 offset. 

For reference, this is a 1966 C model. The picture of the G5s is in level cruise.

 

Thanks!

Edited January 31, 2024 by CalebH
solved problem

[gwav8or]

Following this topic since my '67 F is going to the shop next week for a 355 GPS and dual G5 install.  Thank you for asking the question!

[CalebH]

Just now, gwav8or said:

Following this topic since my '67 F is going to the shop next week for a 355 GPS and dual G5 install.  Thank you for asking the question!

Does your plane have a flat panel/are they going to install one? 

[Utah20Gflyer]

Could you shim out the top shock mounts on the top of the panel to make up the difference in angle?  Sounds like you are already close. 

[CalebH]

14 minutes ago, Utah20Gflyer said:

Could you shim out the top shock mounts on the top of the panel to make up the difference in angle?  Sounds like you are already close. 

That's what we're probably going to have to do. Just wanted to check with others first. 

[TheAv8r]

Huh, I have a dual G5 flat panel and we didn’t have any issues with the calibration. I think yours is leaned back though and on mine we made it flat and straight all the way across. 
 

 

[7.Mooney.Driver.0]

I would recommend leveling the airplane and completing the calibration that way. You can’t account for panel tilt if you input the degrees from rivet line. Below is my set up, this is what calibration looks like with aircraft level vs what rivet line showed with aircraft off jacks, and how it looks flying.

Hope this helps.

[dzeleski]

Your AI is not a level, its a reference to the horizon. You should not expect it to be level in cruise flight as your pitch at 100kts will be different then at 150kts and then your loading will change that as well. Two examples from my J at two different speeds gives slightly different pitches.

The airplane has to be leveled correctly using jacks and then you can calibrate the units. You can tweak it so its close to "level" at your preferred cruise speed but thats not really how its supposed to be done or what the device is actually visually representing.

See this post:

Lots of good explanations on why it could be wrong. Im betting the airplane was not leveled correctly or a step was missed from the manual.

[nbendure]

Caleb,

On our airplane, we chose to have a flat panel at the angle that the original panel had. Like you, we removed the crease, and kept the original shape of the panel. Where our installs differ, is we continued to use the shock mounts that the aircraft had used previously (although we obviously replaced them). Our AI G5 indicates slightly nose low on the ground, and perfectly level in the air, at an offset of around 14 degrees (I'd have to look in the instrument for the specific). Hope it helps, and I'll even include a sweet post install photo!

-Nolan

 

[M20F]

This is why I never trust my instruments in the clouds and only trust the seat of my pants.  If you want to be safe buy Levi’s 501’s they don’t need any calibration. 

[CalebH]

9 hours ago, TheAv8r said:

Huh, I have a dual G5 flat panel and we didn’t have any issues with the calibration. I think yours is leaned back though and on mine we made it flat and straight all the way across. 
 

 

Is your panel just attached to the sub panel or did you make it more “vertical” when you installed? Ours isn’t changed in angle from the original. We attached flush to the sub panel. 

[67 m20F chump]

How many deg. Nose up gives you a Vy climb?   Mine is nose low in cruise and nose high when going slow.  I want a garmin A/P so I can use the flight director.

[TheAv8r]

2 hours ago, CalebH said:

Is your panel just attached to the sub panel or did you make it more “vertical” when you installed? Ours isn’t changed in angle from the original. We attached flush to the sub panel. 

Yeah, we made it more straight and matched the pilot's side angle vs. the other side of the panel.

[CalebH]

6 hours ago, 67 m20F chump said:

How many deg. Nose up gives you a Vy climb?   Mine is nose low in cruise and nose high when going slow.  I want a garmin A/P so I can use the flight director.

Angle for Vy (airspeed) climb will change based on a lot of factors including environmental and loading. Naturally, your attitude will increase when flying at slower airspeeds if you're in unaccelerated level flight.

[CalebH]

16 hours ago, dzeleski said:

Your AI is not a level, its a reference to the horizon. You should not expect it to be level in cruise flight as your pitch at 100kts will be different then at 150kts and then your loading will change that as well. Two examples from my J at two different speeds gives slightly different pitches.

The airplane has to be leveled correctly using jacks and then you can calibrate the units. You can tweak it so its close to "level" at your preferred cruise speed but thats not really how its supposed to be done or what the device is actually visually representing.

Lots of good explanations on why it could be wrong. Im betting the airplane was not leveled correctly or a step was missed from the manual.

You make a good point about the AI being a horizon reference - I think this is something many people don't understand (and I understand I may have sounded like I didn't either!). Yes, the airplane's attitude in flight relative to level changes based on a number of factors including environmental, loading, airspeed, etc.

The problem we're having is that the AI is notably nose down (like 2.5 deg.) which is lower than it should be, even after we followed the calibration procedure. Now, the current Garmin manual calls for you to take a reference level (from a rivet line on our model), do the calibration, and then put in that offset. This negates any need to level the aircraft for calibration in theory. I think we may just level the plane and calibrate it again to see if we were doing the procedure wrong in the Garmin manual, though. 

[dzeleski]

1 hour ago, CalebH said:

You make a good point about the AI being a horizon reference - I think this is something many people don't understand (and I understand I may have sounded like I didn't either!). Yes, the airplane's attitude in flight relative to level changes based on a number of factors including environmental, loading, airspeed, etc.

The problem we're having is that the AI is notably nose down (like 2.5 deg.) which is lower than it should be, even after we followed the calibration procedure. Now, the current Garmin manual calls for you to take a reference level (from a rivet line on our model), do the calibration, and then put in that offset. This negates any need to level the aircraft for calibration in theory. I think we may just level the plane and calibrate it again to see if we were doing the procedure wrong in the Garmin manual, though. 

We leveled my airplane on jacks and did the calibration but this was in 2020 on older firmware. I would try doing it that way and see if you get a better result.

But yeah dont be surprised to see your AI not level in cruise thats completely normal. 2.5 degrees is too much though unless the airplane is wildly out of rig or something strange(doubtful).

[Vance Harral]

While this doesn't directly address your issues with panel tilt and limits, my opinion on calibrating the zero airframe pitch setting of an electronic attitude indicator is that most people seem to overthink it.  I'm aware Garmin prescribes a detailed calibration procedure.  But remember that for most of the almost-hundred-year history of attitude indicators, you could directly adjust the zero-pitch setting of the AI using a knob right on the instrument, in flight (mostly to deal with parallax differences for pilots of different height).  Nobody paid any attention to how precisely that setting matched the actual zero pitch of the airframe.  You just got it close, then figured out in flight what attitude produced level flight at a particular speed on a particular day.  As others have noted, this varies, so it's not like you can really train yourself to achieve level flight by always holding the airplane representation exactly on the dividing line between sky and ground anyway.  Some pilots - like me - even periodically tweaked the AI in flight, as you might do with a heading bug, to mark exactly where to hold pitch on a particular flight segment.

If you translate that to an EFIS, the equivalent would be to install it, leave the tare setting at zero, and go fly on a nice VFR day.  Pick your normal cruise speed, hold level flight based on looking outside and at the ALT/VSI, and just note the pitch setting on the AI.  Get back on the ground, change the tare setting to the opposite of that noted value, and you're done.  Again, I recognize this doesn't exactly follow the calibration procedure in the installation manual, but it certainly meets the intent, and is entirely reasonable and safe.

[N201MKTurbo]

28 minutes ago, Vance Harral said:

 But remember that for most of the almost-hundred-year history of attitude indicators, you could directly adjust the zero-pitch setting of the AI using a knob right on the instrument, in flight (mostly to deal with parallax differences for pilots of different height). 

This isn't true. When an AI is installed in a tilted panel, it had to be specifically balanced for the tilted panel. If you ever played with one on a rate table, you would see that if it isn't balanced properly, vertical, lateral and longitudinal accelerations can cause false pitch and roll indications. Plus the horizon card would be way off from the fixed horizon marks when level.

AIs are typically sold as 0 degree tilt or 8 degree tilt. An instrument shop can adjust it for any tilt you like within the limits of adjustment of the horizon card.

[CalebH]

3 hours ago, N201MKTurbo said:

This isn't true. When an AI is installed in a tilted panel, it had to be specifically balanced for the tilted panel. If you ever played with one on a rate table, you would see that if it isn't balanced properly, vertical, lateral and longitudinal accelerations can cause false pitch and roll indications. Plus the horizon card would be way off from the fixed horizon marks when level.

AIs are typically sold as 0 degree tilt or 8 degree tilt. An instrument shop can adjust it for any tilt you like within the limits of adjustment of the horizon card.

Yes, what you're saying is true for mechanical gyros. In this case, the G5 being solid-state ADAHRS, it just comes down to a calibration. I think what @Vance Harral was getting at is that the adjustment on the AI was to accommodate different pilots' flying positions since parallax is a physical limitation of the mechanical AIs. For a digital unit like the G5 you certainly want to follow the procedure and ensure that the attitude indicator is on the horizon when the plane is level. Then, it shouldn't be changed as there is no parallax with a screen. There's a reason Garmin doesn't give you the option for in-flight adjustments.

The issue we were running into is even after following Garmin's procedure for calibration it seems that the attitude indicator does not show level when the plane is level. Our next step is to just level the plane and recalibrate to see if doing it the "hard way" fixes it somehow. 

[gwav8or]

On 10/4/2023 at 3:59 PM, CalebH said:

Does your plane have a flat panel/are they going to install one? 

No, after looking at it, mine is actually more straight up and down.  The shop is going to put in a flat panel.

[CalebH]

RESOLUTION:

We solved the problem. Even though Garmin states you should be able to calibrate the devices when the plane isn't leveled and then measure and manually apply the offsets, we were limited to 15 degrees of offset which didn't quite get us to where we needed to be. We leveled the plane and then had the devices automatically do their calibration - solved the issue. Not quite sure why this would work and the method garmin calls out in the manual wouldn't. Who cares, it's working now...