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Posted
19 hours ago, kortopates said:

You mean the missing compass deviation card that the plane is un-airworthy without? Yeah, noticed that as well.....

Legit question, my plane has a pair of GI-275s and no whiskey compass. Does the G3x touch with magnetometer not fulfill the requirements for magnetic direction device? The manual on the -275 says that it is a replacement for primary heading. It's not approved for EASA registered aircraft though. 

Posted
Legit question, my plane has a pair of GI-275s and no whiskey compass. Does the G3x touch with magnetometer not fulfill the requirements for magnetic direction device? The manual on the -275 says that it is a replacement for primary heading. It's not approved for EASA registered aircraft though. 

I was thinking of that too, but in the end found a spot for the whiskey compass. I noticed there’s no planes with deviation cards for fancy magnetometers?
  • Like 1
Posted (edited)
1 hour ago, ArtVandelay said:


I was thinking of that too, but in the end found a spot for the whiskey compass. I noticed there’s no planes with deviation cards for fancy magnetometers?

The Garmin G3X/GDU460 installation manual has a section (35.4.8) on calibrating the GMU11 or GMU22 magnetometer, so the displayed data is already corrected--the "deviation card" is built in and already taken into account before the magnetic heading is displayed.

Edited by 1001001
  • Like 1
Posted
1 hour ago, ArtVandelay said:


I was thinking of that too, but in the end found a spot for the whiskey compass. I noticed there’s no planes with deviation cards for fancy magnetometers?

Nice! I have a panel mount compass too but just didn't install it with the Garmins. There is only one spot where the compass can be corrected and it was exactly where the AID resides. So I'm gonna let my buddy try to install it in his Mooney. Otherwise, a new compass will be for sale on here shortly!  

Posted
2 hours ago, ArtVandelay said:


I was thinking of that too, but in the end found a spot for the whiskey compass. I noticed there’s no planes with deviation cards for fancy magnetometers?

Uh, unfortunately, for now... I have one.. Apparently getting the magnetometer installed in our wing is a bit of a task... Unlike the other birds out there. He plans on adjusting it during annual so I should be able to remove it. but right now I am about 5 degrees out when they did the calibration. Not entirely happy about that, but it'll get fixed.

I made this up and it is above my g5's for now:

image.png.03ed3f1a59c8670126b822f77a773c28.png

Posted
Uh, unfortunately, for now... I have one.. Apparently getting the magnetometer installed in our wing is a bit of a task... Unlike the other birds out there. He plans on adjusting it during annual so I should be able to remove it. but right now I am about 5 degrees out when they did the calibration. Not entirely happy about that, but it'll get fixed.
I made this up and it is above my g5's for now:
image.png.03ed3f1a59c8670126b822f77a773c28.png
It looks like your GMU11 needs to be rotated about 5 degrees CW. You can do all the calibration procedures you want but it won't change the results. Ask me how I know :)
  • Like 1
Posted
4 hours ago, gmonnig said:

Legit question, my plane has a pair of GI-275s and no whiskey compass. Does the G3x touch with magnetometer not fulfill the requirements for magnetic direction device? The manual on the -275 says that it is a replacement for primary heading. It's not approved for EASA registered aircraft though. 

AFAIK, neither the GI-275 or G3X can replace a non-stabilized magnetic compass. I don't have an install manual for a certifed G3X touch but the attached image is from an older GI-275 manual.

275.jpg

Posted
37 minutes ago, N231BN said:

AFAIK, neither the GI-275 or G3X can replace a non-stabilized magnetic compass. I don't have an install manual for a certifed G3X touch but the attached image is from an older GI-275 manual.

275.jpg

Yeah I don't have the install manual in front of me but I'm pretty sure with the HSI and reversion switch, it has a different requirement. I know a single 275 with vacuum instruments for backup does need the Compass. The GI-275 3-in-1 is the multifunction display and not the HSI, so I'm guessing there's a difference in there. 

8C7A7674-DFA9-4D37-9FF3-8FE9517EACA6.png

Posted
2 hours ago, N231BN said:

It looks like your GMU11 needs to be rotated about 5 degrees CW. You can do all the calibration procedures you want but it won't change the results. Ask me how I know :)

Yep, that's the plan..

Posted
21 hours ago, philiplane said:

You have to retain the magnetic compass for the eventuality of glass panel failure, or electrical system failure. 

Wonder how Garmin got the TBM940 certified without a compass? I get where people are coming from with this but how many levels of protection do we need? What if a screen goes out? A-Well there’s a redundant screen? What if the ships power is lost? A- The units have a battery backup. What if the magnetometer goes out? Well the screens are connected to a waas navigator and revert to ground track, still better than a compass. What happens if you must shed an electrical load and can’t keep the GTN powered, and simultaneously lose the gmu11 heading reference? Well, it’s time to start cranking the gear down to land….. and I still have four battery backed up screens. Both 275s, the Tie breaking AV20S, and an iPad running with a Stratus 3 ADAHRS. The iPad approach could certainly save the day. It’s a miracle that I used to fly IFR with a single vacuum pump, single nav radio, and paper charts. Kind of gives me the chills now. 

  • Like 3
Posted
50 minutes ago, gmonnig said:

Wonder how Garmin got the TBM940 certified without a compass? 

Not really apples to apples to compare a new certification that incorporates integrated avionics as part of the TC to retrofit avionics modifying an existing type certificate that’s many decades old. 

Posted
1 hour ago, gmonnig said:

Wonder how Garmin got the TBM940 certified without a compass? 

Those systems are certified to a higher level than the retrofit avionics are, so the standby equipment rules are different.

Posted
48 minutes ago, ZuluZulu said:

Not really apples to apples to compare a new certification that incorporates integrated avionics as part of the TC to retrofit avionics modifying an existing type certificate that’s many decades old. 

You do bring up the point that has me hung up on the compass thing too. The Type Certificate. But if the FAA classifies the GMU11 with certain displays to be used as primary magnetic display, then that satisfies the requirement of FAR91.205. Even back in 2017 they were talking about this with the dual G5 setups in Cessnas. My plane is in annual but I'll dig a little deeper into this since my A&P is a Dynon and Garmin dealer/installer. I'll report back in a week.

DDFD915E-1974-4913-B854-FE886156087C.png

Posted
On 12/12/2022 at 2:03 PM, ArtVandelay said:


Show me a NTSB report that blames an accident on a missing calibration card for the whisky compass.

I missed my left turn at Albuquerque for that exact reason. :lol:

Posted
12 minutes ago, gmonnig said:

You do bring up the point that has me hung up on the compass thing too. The Type Certificate. But if the FAA classifies the GMU11 with certain displays to be used as primary magnetic display, then that satisfies the requirement of FAR91.205. Even back in 2017 they were talking about this with the dual G5 setups in Cessnas. My plane is in annual but I'll dig a little deeper into this since my A&P is a Dynon and Garmin dealer/installer. I'll report back in a week.

DDFD915E-1974-4913-B854-FE886156087C.png

G5 installation limitations:

Screenshot_20221214-195934.png

Posted
2 minutes ago, N231BN said:

G5 installation limitations:

Screenshot_20221214-195934.png

Ah Ok, so maybe not the G5s. I had dual G5s in my other plane but kept the whiskey compass with that setup. I'm definitely not trying to be defiant here. My situation is unique because I did a single piece windshield mod and the old compass wouldn't swing mounted to the center bar anymore. I bought a new panel mounted Airpath and it worked perfectly in "one spot only" on the panel, right where the attitude indicator normally went. I flew in this goofy setup for the summer. When I did the GI-275, a third compass was not purchased to go on the center post because it supposedly wasn't necessary. I figured no need to by whiskey compasses to total a G5 if I didn't have to have it.

My friend did his IFR checkride in his Mooney with G5s and an INOP compass. Before the checkride he verified with 3 DARs of the legality (because it would fail you on a checkride), 2 of the 3 said they interpret the FAR as it being totally legal. He obviously passed his checkride with no issues. We are both FAA guys too, so not trying to slip one by the big guys. 

Posted

The issue with the Garmin displays (G5, GI-275) is the backup battery doesn't power the GMU-11. They both have an internal GPS which can give you ground track although that is apparently not good enough.

Posted

To be airworthy, the airplane must conform to it's TCDS and any incorporated STCs or field-approved modifications. The Garmin equipment has to be installed in accordance with the STC, or if not in accordance, it requires a field approval according to Garmin. So, legality (airworthiness) of the installation -- and thus the backup instrumentation required -- depends on what the STC installation manual requires unless you got a field approval for something different.

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  • Like 2
Posted
1 hour ago, N231BN said:

The issue with the Garmin displays (G5, GI-275) is the backup battery doesn't power the GMU-11. They both have an internal GPS which can give you ground track although that is apparently not good enough.

It does in fact power the gmu11. So in a total power loss from the ship, you will have heading info from battery backup. Not sure about the G5s but it does on the GI-275.

  • Like 1
Posted
It does in fact power the gmu11. So in a total power loss from the ship, you will have heading info from battery backup. Not sure about the G5s but it does on the GI-275.
I forgot that the GI-275 does, thanks.
Posted

Yikes.

When I read how much you all pay for avionics installs, my heart is crushed. Y’all must have Veryon’s in your driveways….

I get that time is money and all. Garmin charges a ton of insane money because we feed the beast and pay it. Their margins are insane. I despise giving money to garmin as much as I dislike paying the IRS.

I cut my teeth installing a KcS55a in my 172. Pain in the rump, but done. After that? A little MX20/GMX200 and a 430 was cake.

Installing a 650 from a 430 isn’t that difficult - just takes a little time. A G5? Cake. Navcom’s and transponders? No big issue.

Remote transponders and other things get tricky but ok.

If I can save 25/30k by painting my own airplanes or 50/60k by pinning my own avionics under supervision, I’ll gladly spend my money on other things. A nice pair of magnified glasses, strippers and crimpers, wax cord, pins and a bright light, I’m golden…

  • Like 1
Posted
On 12/12/2022 at 11:23 PM, PT20J said:

CAR3 3.758 only says it has to be on or “in close proximity” to the compass. Since close proximity isn’t defined, it’s open to reasonable interpretation. :D

"On"? I'm getting ideas now how to legally hide one ... :)

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