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Garmin GI 275 - TSB Report

Canadian_JOY

Well Known Member
This report hit the wire today. It documents a very hair-raising flight following failure of a dual GI-275 installation. The 23,000 FPM descent must have had the pilot thinking he would soon be just a grease mark on the face of the earth.

One of the most telling features of the report is Garmin's refusal to share their failure analysis findings with the TSB. What is the Big G covering up? Definitely not confidence-inspiring, especially given the commonality of AHARS solution across multiple Garmin avionics platforms.

https://www.tsb.gc.ca/eng/rapports-reports/aviation/2021/A21P0001/A21P0001.html
 
I don't see where Garmin "refused" to provide data. The document states:
"no supplemental information about the instrument, possible reasons it would require realignment while the aircraft was in flight, or analysis of the occurrence aircraft’s recorded fault logs were provided to the investigation by Garmin"

This could simply mean they are still working on it, or a number of other reasons.

Personally I'm baffled that the aircraft did not have a redundant attitude source. This was one of the things I was told repeatedly I needed when I was designing my panel.
 
I don't see where Garmin "refused" to provide data. The document states:
"no supplemental information about the instrument, possible reasons it would require realignment while the aircraft was in flight, or analysis of the occurrence aircraft’s recorded fault logs were provided to the investigation by Garmin"

This could simply mean they are still working on it, or a number of other reasons.

Personally I'm baffled that the aircraft did not have a redundant attitude source. This was one of the things I was told repeatedly I needed when I was designing my panel.

from my read, it appears the pilot did think he had a backup. Apparently the backup only works if the units are not configured as primary, as they were in his case. I feel for the certified guys who probably don't have access to the installation manuals and may not know this. Though I suppose it may have been discussed in the pilots guide.
 
I should have clarified, sorry. Two copies of the same unit do not qualify as redundancy in my opinion. You need two different code bases to avoid software issues. This is why people add a G5 to their G3X setup.
 
Redundancy

I should have clarified, sorry. Two copies of the same unit do not qualify as redundancy in my opinion. You need two different code bases to avoid software issues. This is why people add a G5 to their G3X setup.
I completely agree with that and would further mention that any backup attitude information should be completely isolated from the electrical system. Dedicated battery only. Dynon D3 is a reasonable option.
 
GI-275

I have read this report a few times since I have two GI-275s installed in my Mooney. What I have, is not what the report claims is in the incident aircraft. The difference being the options and setup configuration. There are three units available from Garmin: A basic unit, a unit with a battery and an ADAHRS board, and a unit with a battery, ADAHRS board and autopilot reference. To replace the attitude indicator, the incident aircraft had the unit with a battery and ADAHRS configured as a Primary ADI (attitude and direction indicator). In this configuration, only the ADI page will display. There was no autopilot in the airplane so it did not have the autopilot reference board (unlike my airplane).

The second unit in that plane had the battery and ADAHRS and was configured as a Primary HSI. When configured as a Primary HSI, it will only display the HSI and HSI + Map pages. It will not display anything else. When configured this way, it will not automatically revert to an ADI if the other unit fails. There will be will be no reversionary switch installed on the panel. Other standby instruments must remain in the panel and this airplane still had the old airspeed, altimeter and T&B. Yes both units in this airplane were the same but configured differently.

Why anyone would spend the exact same money to install the exact same unit configured as a Primary HSI versus what I have, a MFD/Standby ADI
is beyond my comprehension. As a MFD/Standby ADI it will automatically revert to being an ADI if it senses something is amiss with the Primary ADI. There is also a required revisionary switch installed on the panel that would change from whichever page is being used to the Standby ADI page. Configured as a MFD/Standby ADI, many pages are available: first always will be ADI, and in order selected by the installer, HSI, HSI Map, Map, CDI, Traffic, Terrain. If you followed this, you're probably realize the versatility
of the MFD and wonder why they configure the 2nd unit as a Primary HSI. The pilot was not the owner, wonder if the pilot realized he wasn't dealt the full hand.

As to the failure itself, the picture in the report showed airspeed. track not heading, no pitch or roll. Was that an actual picture soon after? 14 Climbing 15,000 in Canada in January, and it hit the fan when entering the clouds. Was ice involved? Was the pitot heat on? Will a frozen over pitot show 0 airspeed or last airspeed? Realize a 6000 hour ATP rated pilot with a failed attitude indicator ought to be able to fly partial panel on those steam gauges unless he had no airspeed. And he apparently didn't realize he exceeded VNE by 70 knots until Garmin told on him.

Why did the ADI fail to begin with? Don't know. You can bet Garmin is looking at the data. But the instrument configuration was so short-changed by the installer, there may be some other lacking in the installation.
 
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Dave has pointed out a few items which raised flags for me. Of course that big question of why an ATP-rated pilot wasn't flying needle-all-airspeed when he lost primary attitude indication is a real puzzler. Helmet fire? Focus on trying to get the HSI to show attitude? Who knows?

The comment about Garmin not supplying any investigative data to the TSB remains fair - they had plenty of time (reports are not published against deadlines - if a manufacturer needs more time to investigate, they get it) and actively chose not to provide any information concerning cause of the AHARS failure.

As for the configuration of the instruments, I suspect there's sufficient complexity that an installer might suffer from glazed over eyes and not realize just how significant are the impacts of choosing one installation configuration over another. This might be an opportunity for Garmin to include in the installation manual a "101-level" roadmap to the various configurations, their strengths and their weaknesses.
 
The comment about Garmin not supplying any investigative data to the TSB remains fair - they had plenty of time (reports are not published against deadlines - if a manufacturer needs more time to investigate, they get it) and actively chose not to provide any information concerning cause of the AHARS failure.

I have never heard of any manufacturer not supplying any and all data to the TSB. There's more to this story, and it's a bit tricky to read between the lines.

Usually it's quite advantageous to be open with the Canadian TSB. Admit the weakness with whatever fault occurred and show willingness to be open and improve the system. Inspires confidence in customers, and users.
 
I have never heard of any manufacturer not supplying any and all data to the TSB. There's more to this story, and it's a bit tricky to read between the lines.

Usually it's quite advantageous to be open with the Canadian TSB. Admit the weakness with whatever fault occurred and show willingness to be open and improve the system. Inspires confidence in customers, and users.

The fact remains that our TSB has no means by which to compel a manufacturer to fully share information. Yes, many manufacturers do, fully intending to advance aviation safety. Some, though, prefer to limit their liability or protect their earnings, thus some information never makes it into the public eye.
 
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