If I have two AHRS can I get rid of my vacuum system?

[Guest]

  On 5/19/2021 at 7:29 PM, RobertGary1 said:

My guess is that pitot is required for the AHRS correction and shutting one down wouldn’t help. My shop said another customer had this happen when they encountered pitot icing. In the soup pitot ices up and you loss airspeed then you lose attitude. Bad day. 

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Bad day caused by bad design.

Clarence

[RobertGary1]

  On 5/19/2021 at 11:32 PM, Immelman said:

Thanks for letting us know, but...

May I suggest letting the NTSB know? Ref NTSB 830, required reports.

I'm serious.... this is more than a support ticket for someone who does elect to drink the punch and remove their vaccum system, thinking two of these devcies provides sufficient redundancy for safe instrument flight

https://www.law.cornell.edu/cfr/text/49/830.5

 

(9) A complete loss of information, excluding flickering, from more than 50 percent of an aircraft's cockpit displays known as:

(i) Electronic Flight Instrument System (EFIS) displays;

(ii) Engine Indication and Crew Alerting System (EICAS) displays;

(iii) Electronic Centralized Aircraft Monitor (ECAM) displays; or

(iv) Other displays of this type, which generally include a primary flight display (PFD), primary navigation display (PND), and other integrated displays;

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I was wondering about this. We had similar happen in a g1000 when I was flying for an operator but in that case you don’t forward to ntsb. But in the g1000 Garmin requires a vacuum attitude and you cannot replace it with a g5. 

[RobertGary1]

  On 5/19/2021 at 11:46 PM, M20Doc said:

Bad day caused by bad design.

Clarence

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Oddly the purpose of this flight was to check things out after I swapped the vacuum pump which was getting weak and had tumbled while waiting for ifr release out of Monterey last week. At the time I though I had two gi-275’s so no big deal. 

[aviatoreb]

Oye - I hate to see that.  I just had a pair of GI275's installed and I ditched the vacuum gauge - but I did keep my mechanical lifesaver attitude indicator.

[carusoam]

Inviting @Fly_M20R who’s video is referenced above...

May want to forward a link to trek @TrekLawler often found at BT...

Garmin has a reporting mechanism that can be found at their website...

PP consideration for getting this challenge solved.... if not an installation issue... there are a few more people that would like to know more about this...

Best regards,

-a-

[Guest]

  On 5/20/2021 at 2:18 AM, RobertGary1 said:

Oddly the purpose of this flight was to check things out after I swapped the vacuum pump which was getting weak and had tumbled while waiting for ifr release out of Monterey last week. At the time I though I had two gi-275’s so no big deal. 

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Many of us have installed modern electronic flight displays because old vacuum driven mechanical gyros are supposed to be unreliable, yet by design they stop working when they loose pitot pressure.

Clarence

[GeeBee]

There is no reason for AHRS to loose alignment due to loss of airspeed input. AHRS requires a speed input, but it can use GPS groundspeed as a backup. Garmin has always allowed this (it is internal to the G1000) and other displays as long as there is a GPS input. I suspect in this case that data was lost, and the question is why are the two displays not switching to GPS input with airspeed loss? It is one of three things. Wiring, configuration or software. Two are installation problems, the last is Garmin's.

 

 

 

[LANCECASPER]

  On 5/20/2021 at 12:42 PM, GeeBee said:

There is no reason for AHRS to loose alignment due to loss of airspeed input. AHRS requires a speed input, but it can use GPS groundspeed as a backup. Garmin has always allowed this (it is internal to the G1000) and other displays as long as there is a GPS input. I suspect in this case that data was lost, and the question is why are the two displays not switching to GPS input with airspeed loss? It is one of three things. Wiring, configuration or software. Two are installation problems, the last is Garmin's.

 

 

 

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If it was software then every GI-275 on this software version would be having issues. I think you're right on an installation issue.

[Yetti]

There is something software too.  Something tripped in the code to cause both of the units to go into the "level the plane" routine.

[Yetti]

Note there is a very small "check engine light" symbol in the very top left.

[GeeBee]

  On 5/20/2021 at 1:41 PM, Yetti said:

There is something software too.  Something tripped in the code to cause both of the units to go into the "level the plane" routine.

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Not necessarily. If the data bus is bad or lacking, nothing is getting through to either unit.

 

[RobertGary1]

  On 5/20/2021 at 12:42 PM, GeeBee said:

There is no reason for AHRS to loose alignment due to loss of airspeed input. AHRS requires a speed input, but it can use GPS groundspeed as a backup. Garmin has always allowed this (it is internal to the G1000) and other displays as long as there is a GPS input. I suspect in this case that data was lost, and the question is why are the two displays not switching to GPS input with airspeed loss? It is one of three things. Wiring, configuration or software. Two are installation problems, the last is Garmin's.

 

 

 

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But it’s still displaying gps course on the bottom. Not had any issue with the HSI in gps mode for this last year or since this happened. 
If there was a wiring issue wouldn’t that have affecting my ability To shoot lpv approaches over the last year?

Edited May 20, 2021 by RobertGary1

[RobertGary1]

  On 5/20/2021 at 1:44 PM, Yetti said:

Note there is a very small "check engine light" symbol in the very top left.

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Yea that also jus happened. It saying the battery is due for an annual capacity test. Hopefully that doesn’t cause this but it just came on the same day (probably my 1 year anniversary since installing) 

[Yetti]

  On 5/20/2021 at 2:20 PM, GeeBee said:

Not necessarily. If the data bus is bad or lacking, nothing is getting through to either unit.

 

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Well unless the wiring went bad to both units at the same time then under your path we have a bad AHRS unit.  Or it tripped and is resetting.

[GeeBee]

  On 5/20/2021 at 2:50 PM, RobertGary1 said:

But it’s still displaying gps course on the bottom. Not had any issue with the HSI in gps mode for this last year or since this happened. 
If there was a wiring issue wouldn’t that have affecting my ability To shoot lpv approaches over the last year?

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Course, but what about ground speed input?

 

[RobertGary1]

  On 5/20/2021 at 3:32 PM, GeeBee said:

Course, but what about ground speed input?

 

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Idk. There is no way to display that on the 275. But when I load an lpv approach the 275 hsi aligns with it. So it’s bene on the buss and talking 

[takair]

Robert, You mentioned a pitot problem was the first link in the chain, was it plugged or open?  It might make a difference on what the unit thought it was seeing.  Open might purely read zero, but if it was plugged...depending on when it plugged and if associated with altitude change, might drive backwards and confuse the software in an unanticipated way.  In other words, it might have had a negative airspeed?

[RobertGary1]

  On 5/20/2021 at 4:08 PM, takair said:

Robert, You mentioned a pitot problem was the first link in the chain, was it plugged or open?  It might make a difference on what the unit thought it was seeing.  Open might purely read zero, but if it was plugged...depending on when it plugged and if associated with altitude change, might drive backwards and confuse the software in an unanticipated way.  In other words, it might have had a negative airspeed?

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The automatic flip up cover failed and stayed closed.

[LANCECASPER]

  On 5/20/2021 at 4:17 PM, RobertGary1 said:

The automatic flip up cover failed and stayed closed.

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There we go. That has to be it. Have you taken that off and tried it again?

Neither of them saw airspeed and could give a reliable attitude so by design that had to show red X's.

[Ragsf15e]

  On 5/20/2021 at 4:44 PM, LANCECASPER said:

There we go. That has to be it. Have you taken that off and tried it again?

Neither of them saw airspeed and could give a reliable attitude so by design that had to show red X's.

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I don’t doubt that this is part of the issue, but they shouldn’t fail on loss of airspeed.  They also have groundspeed input.  Since the old aspens which did fail on loss of airspeed, designers have avoided that due to the possibility of pito tube ice.

[RobertGary1]

  On 5/20/2021 at 4:44 PM, LANCECASPER said:

There we go. That has to be it. Have you taken that off and tried it again?

Neither of them saw airspeed and could give a reliable attitude so by design that had to show red X's.

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Then that should be in big red print on the box when you buy a GI-275. "Warning pitot failure will result in death". I paid good money for two GI-275's under the impression it provided redundancy. 

Edited May 20, 2021 by RobertGary1

[Yetti]

  On 5/20/2021 at 5:14 PM, RobertGary1 said:

Then that should be in big red print on the box when you buy a GI-275. "Warning pitot failure will result in death". I paid good money for two GI-275's under the impression it provided redundancy. 

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If you want back up you need separate systems.  

[RobertGary1]

  On 5/20/2021 at 5:25 PM, Yetti said:

If you want back up you need separate systems.  

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Garmin's whole ad campaign shows replacing an entire panel with two gi-275's. No airspeed, turn coordinator, altitude etc. 

[Ragsf15e]

  On 5/20/2021 at 5:27 PM, RobertGary1 said:

Garmin's whole ad campaign shows replacing an entire panel with two gi-275's. No airspeed, turn coordinator, altitude etc. 

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are you gonna try contacting Garmin or maybe through Trek on BT?

[RobertGary1]

  On 5/20/2021 at 5:53 PM, Ragsf15e said:

are you gonna try contacting Garmin or maybe through Trek on BT?

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They contacted me and asked for contact information. I provided it and am waiting. Initially I was going to allow the shop that installed it last year to deal with it but they're so far behind on work they're probably busy, although they share the concern.