Avionics back up question

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john cronin

Filing Flight Plan
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jc4461
I have a piper archer with a g1000 installation. No vacuum pump but in Piper's infinite wisdom ... only one alternator. Not even an open accessory drive for a standby alternator.
I have had Alternator failure in the past in VFR and it was really no big deal... Vacuum pump still worked and i just landed VFR and installed a rebuilt alternator... problem solved.
However, with the G1000 glass panel, if the alternator dies... it automatically goes to the back up battery ( which is ONLY about thirty minutes). If i am flying IFR and this happens, it would be really cutting it close to get on the ground in less than thirty minutes unless i could find VFR really fast and land. No vacuum pump in this airplane.
I was thinking about any options which might be available if the unthinkable happens but i am not sure if is actually a feasible idea.
I was thinking of using the synthetic vision in my iPad mini ( forelight) coupled with a sentry ADSB-in) that would give me synthetic vision just to get on the ground and i would be running off a batteries ,not the aircraft batteries.

Maybe i am overthinking this and 30 minutes is more than enough time on an IFR fight to declare an emergency and land o the standby battery.

Is this a good option?
John
 
Correct me if I'm wrong, but wouldn't the ship's battery(ies) be able to provide power for some additional minutes before the G1000's backup battery had to kick in?
 
30 minutes is the regulatory requirement for minimum time with an older battery, no ship power, maximum power consumption of the device, etc. In real life, you'll have more time available.

Having said that, the key is early recognition and execution of an immediate alternate plan. It should be a rare event that 30 minutes can't take us to an airport with good approaches (low minimums).

- Martin
 
ISU_Radar said:
Correct me if I'm wrong, but wouldn't the ship's battery(ies) be able to provide power for some additional minutes before the G1000's backup battery had to kick in?
Click to expand...

I just checked my POH.... you are absolutely Right! i am wrong! thank you for helping me out... reading it carefully.. explained exactly what you said. It was just not as clear LOL

Thank you for the help!
 
Martin Pauly said:
30 minutes is the regulatory requirement for minimum time with an older battery, no ship power, maximum power consumption of the device, etc. In real life, you'll have more time available.

Having said that, the key is early recognition and execution of an immediate alternate plan. It should be a rare event that 30 minutes can't take us to an airport with good approaches (low minimums).

- Martin
Click to expand...

Thank you Martin... I guess I am too cautious ! good point!
 
john cronin said:
Maybe i am overthinking this and 30 minutes is more than enough time on an IFR fight to declare an emergency and land o the standby battery.
Click to expand...

As stated above, with the Ship's battery and then the Garmin standby battery, you *should* have enough time. Making sure the ship's battery is in good shape suddenly becomes more important on your pre-flight considerations!

-Skip
 
Skip Miller said:
As stated above, with the Ship's battery and then the Garmin standby battery, you *should* have enough time. Making sure the ship's battery is in good shape suddenly becomes more important on your pre-flight considerations!

-Skip
Click to expand...
Skip,
You are right

I didn't read the POH correctly.... It said exactly that in about 4 pages and i missed it.
 
john cronin said:
I just checked my POH.... you are absolutely Right! i am wrong! thank you for helping me out... reading it carefully.. explained exactly what you said. It was just not as clear LOL
Click to expand...

I was gonna say - I don't have any time in the G1000 Archer, but in the DA40 the progression after an alternator failure would be to switch on the essential bus switch first, which automatically disables GIA 2 (which takes down the second GPS, Nav, Com, and the computer behind them among other things). Only when the ship's battery is unable to provide sufficent power do you end up flipping the Emergency switch and being stuck with the backup instruments with their additional half hour backup battery.

It'll certainly be somewhat different on the Archer, but it's well worth taking the time in the POH to both learn the procedures and understand the systems in detail so that you know intuitively what actions to take immediately in such an event before you pull out and run the checklist.
 
It would be a good safety feature IF non required back up instrumentation didn't need to go through extensive approval.
 
What about the company that was going to market a standby alternator to fit in place of a removed vacuum pump ? Haven’t heard much about them lately. I would think that might be an option to buy some time in the event of the primary alternator failure.
 
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