G5 power question

Discussion in 'Avionics and Upgrades' started by Jdm, Jun 26, 2020.

  1. Jdm

    Jdm Pre-takeoff checklist

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    I’m sure there’s a simple answer but here goes.. How does a G5 know the difference between power failure and just cutting off the master switch? It’s suppose to run for hours in the event of a power failure but it shuts down within a min or so of switching off the master.

    Here’s what has me concerned. I’m looking over our 45 year old emergency procedures and thinking about what would actually happen with all the updated equipment. For electrical fire in flight the Cessna procedure is to obviously cut off the Master switch as the 1st step. It seems to me that this would kill my only source of attitude info. It’s possibly more appropriate to just cut off the avionics master as the 1st step and then the aircraft master as necessary.
    This airplane didn’t have an avionics master from Cessna and therefore it isn’t addressed in the procedure.

    Appreciate it.
     
  2. bnt83

    bnt83 Final Approach

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    It doesn't. When it loses power it starts a timer, you have 45 seconds to tell it stay one or they shutdown by themselves. Its very obvious what is happening if did that awhile airborne. Just push a button or knob and they stay on till they run out of battery, are manually turned off or external power is restored.

    All emergency procedures related to aftermarket equipment will be identified in the applicable Airplane Flight Manual Supplements for that equipment.
     
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  3. Ryan Klems

    Ryan Klems Pre-takeoff checklist

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    Two things, one it won’t auto power off of it detects airspeed and two, if it were to start the auto power off countdown, all you have to do is press the power button or the knob and it cancels the countdown and stays on.
     
  4. bnt83

    bnt83 Final Approach

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    I should try pulling the breaker again with the newer software, I'm pretty sure they started the countdown while airborne last time I did it.
     
  5. Jesse Saint

    Jesse Saint Line Up and Wait

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    If it started the countdown in flight, it was not configured correctly. The configuration says to only set auto power off on ground only. It’s easy to change.
     
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  6. Jdm

    Jdm Pre-takeoff checklist

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    Excellent, that explains it. Either it stays on due to airspeed/flight data or I’ll have the option of selecting to continue with G5 battricity
    Thanks!
     
    Last edited: Jun 26, 2020
  7. WannFly

    WannFly Final Approach

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    related Q ... if you have a fire behind the panel.... do you still want to keep the batteries going? does it matter? will it add so called more fuel to the fire if power is drawn from that battery vs no power drawn?
     
  8. Jdm

    Jdm Pre-takeoff checklist

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    I suppose if it’s an electrical fire with the source being the G5 itself maybe. Otherwise I don’t see how it could “fuel” anything based on draw. The only reason I would even consider leaving them powered is in the event of a fire in IMC. I got rid of the vacuum AI system all together. If it were VMC I wouldn’t think twice about powering it down totally.
     
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  9. 3Y3Flyer

    3Y3Flyer Pre-Flight

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    I fly dual G5's and love them....the reason you kill power at the Master for a fire is to eliminate spark or hot spots caused by wire chaffing or shorts behind the panel that the fuse or breaker failed to trip on. The direct voltage provided by the batteries in the G5 will not back feed into the wiring, thus not fueling an electrical fire behind the panel. Kill the master in a fire, if in IMC...keep flying your bugs, extinguish the electrical fire, then bring your nav and comms back on line one at a time if possible. If not possible, have a back up...I carry a portable nav/comm for just this situation. But the overall point is you should be able to maintain your G5's for 3-4 hours, and therefore have a 6 pack worth of information regardless of your power situation.
     
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  10. Jdm

    Jdm Pre-takeoff checklist

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    Thanks! I get the idea, and you’re plan is exactly what I was thinking myself. Just wasn’t sure how the G5 knows to remain powered up with the master off in the air.
    I need to figure out if the process is automatic in flight (unlike on the ground) or if I need to select to continue on g5 power. Either way it’s a great system
     
  11. MauleSkinner

    MauleSkinner Final Approach

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    I just want to reiterate...make sure you’re looking in the right place for any applicable procedures.
     
  12. chemgeek

    chemgeek Pattern Altitude

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    Keep in mind that your GMU-11 magnetometer is not powered by the backup batteries, so you will lose magnetic heading when the main power goes out completely. The G5 HSI can still derive heading information from your GPS if it is powered. If the GPS is also powered down, you will have no heading information on the G5 HSI and will have to revert to the magnetic compass for heading.
     
  13. Jdm

    Jdm Pre-takeoff checklist

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    Excellent point. I have the supplement in the airplane.
     
  14. Jdm

    Jdm Pre-takeoff checklist

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    That’s good info there! Attitude only right? In the example of electrical fire there would be no gps once the master is switched off. My GI-275 however has a internal self contained VFR “direct to only” GPS that powers up during such an electrical failure. This brings up more power questions. I didn’t opt for the 275’s $400 remote battery so it probably wouldn’t do jack. I’m going to take Maules advice and reference the supplements before getting into all that...
     
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  15. WannFly

    WannFly Final Approach

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    in a situation like that i would turn the internal GPS of G5 on and at least get ground track, i know there are few people who have an external antenna connected to G5 just for this reason
     
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  16. Jdm

    Jdm Pre-takeoff checklist

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    Didn’t realize the G5 has an internal GPS? I know the 275 has it. We connected the 275 to an external antenna instead of using the hockey puck
     
  17. WannFly

    WannFly Final Approach

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    It’s disabled in certificated install. I think in one of the revisions they said if you have an external antenna , that can be enabled.

    The 275 GPS is VFR only rt?
     
  18. Jdm

    Jdm Pre-takeoff checklist

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    Yes, VFR only. I’ve never actually tried it. Plenty busy with the other gadgets
     
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  19. flyingcheesehead

    flyingcheesehead Touchdown! Greaser!

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    I would highly recommend that you take the POH emergency procedures and combine them with the supplements yourself to create emergency (and normal, if you so choose) checklists that are correct for your airplane. In the event of a real emergency, the last thing you want to have to do is dig out aircraft flight manual supplements and page through everything to be sure you're covering all your bases.
     
  20. Jdm

    Jdm Pre-takeoff checklist

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    Yep. Working on that now. The supplements are not the easiest to understand with various options. Definitely want to be ahead of that with a personal checklist