Cessna 172-sp G1000 PFD1 & MFD1 cooling

A

andreasmkr

New Member
I have a question for you guys that know the g-1000 system pretty well..

In the checklist for the G-1000 C-172SP it tells you to turn off the stby battery if you have an overheating announciator for the PFD/MFD..

In my eyes it makes no sense in just turning the STBY batt off. You should turn off your PFD&MFD for them to not overheat completely?

Scenario:

Say you are en-rounte to your destination (IMC), you get hit my lightning but there is no announciator indication that any of your equipment is malfunctioning.
After a 10 min of flight you get an overheating warning on the MFD & PFD. (PFD/MFD FAN HAS FAILED)

Nrst airport is 25 nm from your position and you request a GPS approach into that airport.

En-route to your alternate... do you leave your PFD & MFD like the checklist says or do you turn off your avionics I & II, MSTR AND Stby battery?

My answer:
Notify ATC that your system is overheating and that you are tuning all electronic equipment off for a period of time en-route to your IAF. You note your ground track and compare it to your mag compass. After notifying ATC and turning the MST off and avionics of, you follow the mag compass for a certain amount of time and then contact ATC when you turn the system up again and cross-reference your track with the track to your IAF.

Then you are basically saving your PFD&MFD for the approach and not wasting it for your en-route flight..?


What do you guys think?
 
If checklist says turn off sby batery why would you do any different from what it says? Sby Batery on the C172 G1000 is between the panel and the firewall, so Im guessing it could cause overheating in the area behind the PFD (excesive rate of charge maybe?). I dont think the PFD is going to blow up because its ventilation fan is not working. You think that the thousands of dollars worth of avionics on a G1000 rely on a 5 dollar fan to keep everything working? My guess is that the designers wouldn't allow for such a simple failure to render all the avionics unusable (you probably know how much redundancy there is in the G1000).

I would simply follow the checklist (turn off the standby batery), hope for the annunciator to come off and proceed with all my avionics working. If annunciator remains on, then I'd ask for priority for landing. I'd also consider dimming the screen, im not quite sure, but I think it'd consume less power (Amperes) and thus less heat would be genereted.

My point is, if a PFD overheat is such an important issue, it would probably show up as a (yellow) message.
 
LV-ARG said:
If checklist says turn off sby batery why would you do any different from what it says? Sby Batery on the C172 G1000 is between the panel and the firewall, so Im guessing it could cause overheating in the area behind the PFD (excesive rate of charge maybe?). I dont think the PFD is going to blow up because its ventilation fan is not working. You think that the thousands of dollars worth of avionics on a G1000 rely on a 5 dollar fan to keep everything working? My guess is that the designers wouldn't allow for such a simple failure to render all the avionics unusable (you probably know how much redundancy there is in the G1000).

I would simply follow the checklist (turn off the standby batery), hope for the annunciator to come off and proceed with all my avionics working. If annunciator remains on, then I'd ask for priority for landing. I'd also consider dimming the screen, im not quite sure, but I think it'd consume less power (Amperes) and thus less heat would be genereted.

My point is, if a PFD overheat is such an important issue, it would probably show up as a (yellow) message.
Click to expand...

BUT IF I put the standby battery on the off position, does it stop the charging of the standby battery?
 
Yes it does, however it should be fully charged, and since you are supplying power to the Essential and main busses (electrical #1 & #2) trough the MAIN battery it shouldn't be draining power from the Standby battery. However, If I were you, once I have my engine running I'd turn off the Standby battery for a moment and check the S ammeter. That way you will know if you can count on that sucker remaining fully charged if you ever have to turn it from Armed to off.

Its been a year since I flew on a G1000 172 so there might be mistakes in what I've just said. Hope another glass pilot can give his insight on this.
 
Sounds like a lot of speculation in here. Methinks y'all need to dig into the manuals and find out a little more about what powers what in the system.
 
I'm flying tonight, I'll grab one of the G1000 and emergency manuals and see what they say about it.
 
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