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Date: Thu, 23 Aug 2007 17:05:40 -0400
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From: Hamid Wasti <hwasti@lm50.com>
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Subject: Re: [LML] Re: fallability in the digital age
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terrence o'neill wrote:
> I have dual GRT, a/p etc., and a Garmin 396 with its flight panel, 
> which I think will not go dark if everything else does, as it 
> automatically switches to its own battery.  Am I overlooking something 
> here?
Yes, you are overlooking something. If the GRT, a/p etc died because of 
an over-voltage condition, will the 396 that was connected to the same 
power supply and saw the same voltages survive? 

I do not know how Garmin has designed the power input on the 396 so I 
can not give a definitive answer.  My educated guess is that it is 
unlikely that a portable GPS unit that sustains a serious enough 
over-voltage condition to kill the power input will  keep working on its 
internal the battery.

If you want a truly independent GPS, it needs to be independent of the 
aircraft's power bus, which means running it on internal batteries all 
the time.

Regards,

Hamid