Lost my HSI (G1000) in IMC yesterday

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Doug
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Re: Lost my HSI (G1000) in IMC yesterday

Post by Doug »

Tim wrote:
Doug wrote:I had this happen in my DA42 and it was the Magnometer needed to be re-calibrated. It usually happened just as I was entering cloud. Have another 200hrs on it and it has not came back. Should take less than 1 hr to recalibrate.
Doug, this might sound like a strange question, but do you normally switch off you strobes when you enter IMC? Thanks. Tim
I was thinking the same thing that you are thinking; I always use both position and strobe lights for VFR and IFR flight. The only time I don't use strobe is while on ramp or taxiway at night or snowfall. If I'm off the ground both position and strobes are on.
I hope that the magnometer re-calibrate fixes the problem!
Doug Thompson
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Gary
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Re: Lost my HSI (G1000) in IMC yesterday

Post by Gary »

Rick wrote: So... we call Diamond Tech Support, and they said they have seen this before. In fact, they said this is why passing the Magnetometer Interference Test is not required on the DA40 - because many of them fail on the Pos lights. There is a SB on this issue, but only for the DA40F - although they said some shops have successfully applied the SB to the DA40's also. It involves relocating the Magnetometer away from the internal metal structures in the wing. It currently sits between the steel wire tray and the metal grounding straps for the control surfaces, despite Garmin's requirement that it should not be placed within 8" of any metal. Not sure what Diamond was thinking here when it choose the current location. But I'm not ready to move it yet, either - it looks like a big deal.
A well equipped avionics shop can measure the magnetometer interference using special equipment. I had this done prior to the installation of the Garmin G500 in my formerly steam gauge DA40. This could be used to determine if you actually need the SB that replaces the steel aileron counterweight with a brass one.
http://www.diamond-air.at/fileadmin/upl ... alance.pdf

Here is an exerpt in the email from my shop:
...we have completed the Garmin magnetometer location check in your aircraft. While we did see both the aileron counter weight and the nav lights effect the current flux detector location, they are both within the allowable tolerances outlined by Garmin. Based on this we will proceed with the G500 installation as planned.
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Rick
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Re: Lost my HSI (G1000) in IMC yesterday

Post by Rick »

Gary wrote:A well equipped avionics shop can measure the magnetometer interference using special equipment. I had this done prior to the installation of the Garmin G500 in my formerly steam gauge DA40. This could be used to determine if you actually need the SB that replaces the steel aileron counterweight with a brass one.
The G1000 has the flux disturbance test built in. Allowable tolerances are 4 milliGauss in the X and Y axes, and 8 mg in the Z axis. Our aileron disturbances are all less than 1 mg, so I don't think we need the brass counterweight, but turning on the Position lights produces a 12.7 mg disturbance!
Gary wrote:Here is an exerpt in the email from my shop:
...we have completed the Garmin magnetometer location check in your aircraft. While we did see both the aileron counter weight and the nav lights effect the current flux detector location, they are both within the allowable tolerances outlined by Garmin. Based on this we will proceed with the G500 installation as planned.
Gary, I'm just curious - how far from the wingtip did your shop mount your Magnetometer? It seems the "ideal" location would be much farther outboard than the sopt Diamond choose for the G1000 installation.
Roanoke, VA (KROA)
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Gary
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Re: Lost my HSI (G1000) in IMC yesterday

Post by Gary »

Rick wrote:The G1000 has the flux disturbance test built in. Allowable tolerances are 4 milliGauss in the X and Y axes, and 8 mg in the Z axis. Our aileron disturbances are all less than 1 mg, so I don't think we need the brass counterweight, but turning on the Position lights produces a 12.7 mg disturbance!Gary, I'm just curious - how far from the wingtip did your shop mount your Magnetometer? It seems the "ideal" location would be much farther outboard than the sopt Diamond choose for the G1000 installation.
The test equipment used by the shop might be more accurate. Did the position lights always have that reading or did somebody mess with something during maintenance?
They placed the new Garmin magnetometer in the same location as the old Honeywell unit. I can take measurements and post some photos (if I remember) next time I am out at the hangar.
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Re: Lost my HSI (G1000) in IMC yesterday

Post by Tim »

After Rick took the '40 into the shop and did the recalibration of the magnetometer, I flew with my wife to Beaufort NC (KMRH) and back yesterday (I'll post a separate trip report on that later). The journey was about 250nm each way and the conditions were very good. Not CAVU but close.

I tried everything to get the HDG problem back: cellphones, ipad and running with the nav lights on for the whole trip. The HDG indicator never blinked, not even during the runup in Roanoke when it normally burps for a few moments.

Perhaps the calibration did the trick. We'll monitor it carefully and report back if there's any backsliding.

Tim
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Rick
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Re: Lost my HSI (G1000) in IMC yesterday

Post by Rick »

After a month of post-magnetometer-recalibration flights, I am happy to report we have not had a single HDG failure, either in flight or on the ground. I am now confident the recalibration solved the problem. Before, we would routinely have HDG failures during the run-up at our home base, probably 80% of the time.

I now believe Diamond is correct about the high interference numbers from the Position lights not being significant, although it is still a bit unnerving. I received a set of numbers from another member who tried the interference test, and our Nav interference numbers were 100 times higher then their numbers. But, it's all working now, so I can't complain! :)
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Re: Lost my HSI (G1000) in IMC yesterday

Post by Antoine »

Hi all

My turn to report here. I think I need help!
The X'ed out heading information has come progressively, more and more over 6 months or so - but always on the ground. Last weekend I flew to Norwich, England and it was a low-ceiling rainy day. Upon departing, the problem occurred several times on the ground and then just as we entered clouds.
I can't remember exactly but I think I may have switched the position lights to on when it happened.
Emergency landing in minimum IFR (Norwich had the fire trucks waiting for us!) and tried removing and reconnecting GMU, checking GPS RAIM to no avail .

I am going through a big cleanup of contacts now, but I'd like your opinion: the problem has been happening more and more frequently over the last few months (only on the ground until this event). It became extreme in very wet weather and disappeared altogether as the weather became warm and sunny and the plane sat for a few hours in sunlight - it did NOT happen in the 4+ hour flight home in VMC and summerly temps.

Garmin say that because the problem was worsening gradually they suspect a GMU failure (I have already had one replaced...)

What do you think? Should I go through the hassle of removing seats etc to clean every bloody connector or just start by ordering a new GMU? What about recalibrating?
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Re: Lost my HSI (G1000) in IMC yesterday

Post by Steve »

Antoine:

Based on the above, it may be worthwhile to recalibrate the magnetometer. At least it is an easy first step, before replacing boxes that may, or may not, be bad. Good luck,

Steve
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Re: Lost my HSI (G1000) in IMC yesterday

Post by BurdetteB »

I had the exact same problem and replaced the ahrs memory chip and fixed the problem
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Re: Lost my HSI (G1000) in IMC yesterday

Post by Rick »

Like Steve said, you have nothing to lose by trying the magnetometer recalibration. It takes maybe 15 minutes to do, you can do it yourself, and it's free. Worst case, you still have your problem and you've wasted 15 minutes and 1 gallon of gas. But I know of a number of cases where the recalibration just made the problem go away - hopefully you will be another success story!

I will PM you the instructions in case you want to try it...
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