Location of GMU44 & GRS77 in a 2011 DA40-XLS

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HPNAviator
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Location of GMU44 & GRS77 in a 2011 DA40-XLS

Post by HPNAviator »

Having intermittent issues with loosing heading indication on G1000. Was wondering if anybody on this board knows the location of the GMU44 Magnetometer and the GRS 77 AHRS on a 2011 DA40-XLS. Taking plane to a Garmin 1000 Avionics shop on Wednesday but they have little experience with DA40's mostly Cessna's and Cirrus's. Thank you in advance.
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Re: Location of GMU44 & GRS77 in a 2011 DA40-XLS

Post by Antoine »

The magnetometer is located in the wing. check AMM for details. It is available here

http://support.diamond-air.at/da40-180_ ... 73ab0.html

I had a case of losing heading (in IMC just after take-off mind you!) on a very humid and rainy day (yes, in the UK)

To fix it "we" tried two things:
- recalibrate magnetometer (have a G1000 specialist do that!) - was Garmin's recommendation
- check all cabling connectors from magnetometer to G1000 and clean them with the magical contact cleaner (forgot name) that was PIREPed on this forum. It was sold by a an audio recording studio in NY.
number 2 worked. There are quite a few connectors including one which is impossible to reach in he wing root IIRC.

Good luck! Please share the solution as it seems to be quite a common problem.
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ThomasD
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Re: Location of GMU44 & GRS77 in a 2011 DA40-XLS

Post by ThomasD »

The GMU is way out in the right wing - look underneath for a round plate. I had exactly this issue - took ages to diagnose as intermittent.

Went to 3 avionics shops plus Diamond Canada themselves. Spent ages doing recalibrations, balancing the prop, replacing LRUs... Turned out to be a very simple thing - poorly crimped connectors between the GMU and AHRS: the right avionics shop diagnosed it within an hour. FYI there are 4 (more?) connectors between the AHRS and GMU (presumably to make installing wiring easier). The avionics shop who found the problem disconnected the GMU and AHRS then buzzed out the wiring between, gently pulling on the wires.
Suggest you get the avionics shop to do this first.

Also have a look at the AUX page on the G1000 - will tell you if the GMU only or the AHRS also has a problem.

Good luck.
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Re: Location of GMU44 & GRS77 in a 2011 DA40-XLS

Post by HPNAviator »

Thomas and Antoine, thank you for your replies. Do either of you know where the AHRS is located? I did check the AUX page and no errors show when the heading indication is lost. I wonder if there are any error logs in maintenance mode on the G1000 that can be accessed to see what has happened. Also one other question do you start your engine while the AHRS is still aligning or wait until the AI and heading come up before starting the engine?
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Re: Location of GMU44 & GRS77 in a 2011 DA40-XLS

Post by Antoine »

Hi IIRC the AHRS is mounted near the avionics rack, under the baggage compartment.
Check this for more background
http://www.pprune.org/private-flying/37 ... blems.html
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Re: Location of GMU44 & GRS77 in a 2011 DA40-XLS

Post by ThomasD »

Actually I am thinking again and will check - I seem to remember that maybe I had the same i.e. no red X when it was just the GMU connection problem - I have some photos of the G1000 screens from the time concerned, I will find them this evening or tomorrow and see. From recollection the GMU does not have a direct connection to the G1000 - it has 4 wires that only go to the AHRS - so from memory I am not sure that it has it's own line on the G1000 AUX page (and if this is the case there could be a connection problem between the GMU and AHRS which is not shown).

BUT - health warning - I might be completely mis-remembering - I will check and I'll get back on this
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Re: Location of GMU44 & GRS77 in a 2011 DA40-XLS

Post by ThomasD »

My mistake ! The GMU does have an indicator on the AUX page - you need to scroll down on the AUX page to see it.

Photos attached showing the red X by the GMU and the HDG with red X
Attachments
Red X with GMU fault on PFD 30-May-09 rdcd.jpg
G1000 AUX page showing GMU faulty pic2 30-May-09.jpg
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Re: Location of GMU44 & GRS77 in a 2011 DA40-XLS

Post by Sandy »

I have had intermittent issues with the heading taking a long time to come up. Each time it would be X'd, as in ThomasD's first photo. Unfortunately, I never looked at the Aux screen when it happened. Last week I had a new issue, in that the heading came up, but I had a red X to the right of the Altitude tape. Again, I forgot about checking the Aux screen, but the heading was working perfectly. After thinking about the issue, I went back to my hangar, and, sure enough, I had the red X, again. This time I went to the Aux screen (engine off in the hangar), and saw that there was a red X on GMU1. Related to the heading X issue? Other thoughts? What does the red X on the PFD indicate? Why was heading working perfectly (on ground and in the air) with the red X on the right of the Altitude tape?
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Re: Location of GMU44 & GRS77 in a 2011 DA40-XLS

Post by CFIDave »

FWIW, I've seen the big red X in the PFD precisely where it is on your display -- it was caused by a database mismatch. This was in a DA40 by not having the same NavData file loaded on both PFD and MFD.

This would be a good thing to check first.
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Re: Location of GMU44 & GRS77 in a 2011 DA40-XLS

Post by Rick »

Was anything listed under the ALERT (or ADVISORY) button on the far right of the PFD? It looks like it is lit up in your picture, indicating there is some message there that might shed some light on the problem.
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