Power Surge killed electronics...

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Retz
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Power Surge killed electronics...

Post by Retz »

Hi all,

On my 2006 DA40, G1000 KAP140, I had a power surge during flight that simultaneously kicked off 5 CBs (ESS TIE, MAIN TIE, CDU FAN, AP, and AV FAN). We found the MFD Fan and Avionics tray fan hard shorted, an autopilot roll servo shorted, both strobe boxes burned out, and I'm sure more to come...

My mechanics think that a broken ground wire that runs from the alternator to the regulator caused the regulator to run away and cause the surge. Does that sound right? I want to make certain we find the cause prior to putting the airplane back up and burning out more equipment.

Additional data: the plane just came out of a 2000hr Inspection (with the wing and tail pull, etc.)

Thanks
Joe
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Steve
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Re: Power Surge killed electronics...

Post by Steve »

Hi Joe. Sorry to hear about your trouble. Certainly not an expert on this type of failure. It sounds reasonable that loss of the VR ground would disable the over voltage protection circuit, and at flight RPM, you had a massive over voltage (as much as 100 volts) which caused the CB trips and damage to your avionics. It does sound weird, however, that an unpowered regulator (it lost its ground) would still power the Alternator Field. This is a good write up on our type of regulators:

http://www.kellyaerospace.com/articles/VoltageReg.pdf

although it doesn't specifically address loss of the ground connection. Unfortunately, after an apparent over voltage event like you experienced, the entire electrical system of your airplane (or at least every piece of equipment that was powered ON at the time of the failure) will have to be carefully checked. Alternator, relays, the entire G-1000 system, lights, etc.

Please keep us informed as to your progress. It must suck to have such a serious (expensive) maintenance issue shortly after such an extensive maintenance evolution. I know you want to fly the airplane, not repair it...

Steve
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Rick
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Re: Power Surge killed electronics...

Post by Rick »

Wow - sorry to hear that, Joe. Any chance you keep a data card in the upper MFD slot? I'd love to see your last couple of flights, the voltage values in particular. I had my VR fail last year, but it was clear from the data card it had been failing for several flights before it failed - I just wasn't looking for it. In my case, though, it was still clamping at 29-ish volts so I never had the surge. When it finally failed, the voltage just went to zero

I hope your shop finds a definitive cause. Possibly a short within the VR? And if we're lucky, the data card may contain a clue as to something we can look for to predict a failure like this before it happens again!
Roanoke, VA (KROA)
Retz
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Re: Power Surge killed electronics...

Post by Retz »

Rick/Steve - thank you for the reply.

I pulled the data card today, and unfortunately, the card had maxed out about 10 flights prior. Lesson learned put a bigger card in and download more regularly. ARRGGGHHH
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Rick
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Re: Power Surge killed electronics...

Post by Rick »

Oh no, that's a shame. It still might be worth uploading the last couple of flights on the card to the Reports section here and look at the voltage traces just to see if anything looks unusual.
Roanoke, VA (KROA)
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