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Stan Fields wrote:
I like the idea of the Garmin 396 for backup. Have you ever had to use it?
Whether you are using a Garmin 396 or a classic 6-pack, you need to practice with it under a hood in VMC with a safety pilot to make sure that you can control the airplane with it. Being in IMC with a malfunctioning PFD and on the verge of going into an unusual attitude is no time to test this.
A backup system, whether it is vacuum gyros or a 396 is useless unless you practice using it on a regular basis. Also, if a Garmin 396 is you backup, it needs to be powered up and preferably on the appropriate page before you get IMC. Being in IMC with a dead PFD and on the verge of going into an unusual attitude is no time to be fiddling with the Garmin 396 or waiting for it to power up and acquire satellites.
Are your two GRT EFIS on different busses? It seems like that would make it
tough to loose them both.
Not really. Two busses, if designed and wired properly can protect against some adverse events. But even the best designed system would not quality as "tough to loose them both." If you are thinking battery/alternator failure or a short on the bus, a buss can die leaving the other buss unharmed. However, depending upon how the system is designed and wired, there are failure modes where a dying buss can take the other one with it.
As Jeff already pointed out, you need to worry about other things besides a dead battery & alternator. You can not address the issue of proximity on an airplane the size of a Lancair. Even completely independent busses will feel the effects from a lightning event or HIRF almost equally and if one fails, the other is likely to fail as well. If you are using identical systems, they likely have the same code and hence the same bugs.
Regards,
Hamid
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