G1000 Software bugs with Cessna 172S

gotWXdagain

Polished Member
Has anybody else here noticed that it seems to take forever for the LOW VOLTS indication to actually appear, when simulating electrical malfunctions? The POH for the aircraft says that whenever either M BUS or BUS E volts drops below 24.5, the message should appear, however in practice I've had bus voltage below 24 with current in excess of 10 amps from both M BATT and BATT S with now LOW VOLTS indication. This seems like a lawsuit waiting to happen.
 

pwttogfk

Well-Known Member
That's a typo. First, on page 7-53:
When the voltage for either main or essential buses is below 24.5 volts,
the numeric value and VOLTS text turns red. This warning indication,
along with the LOW VOLTS annunciation, is an indication that the
alternator is not supplying all the power that is required by the airplane.
This is correct that the value and text will turn red below 24.5. That is your first indication of an alternator failure. However, LOW VOLTS will not come on until your voltage has dropped below 24.0 volts. This is incorrectly stated as 24.5 volts in the PIM available online on page 7-55. The actual aircraft POHs might have that corrected--the PIMs aren't updated or corrected nearly as often. Not totally sure on that though.
 

gotWXdagain

Polished Member
That's a typo. First, on page 7-53:
This is correct that the value and text will turn red below 24.5. That is your first indication of an alternator failure. However, LOW VOLTS will not come on until your voltage has dropped below 24.0 volts. This is incorrectly stated as 24.5 volts in the PIM available online on page 7-55. The actual aircraft POHs might have that corrected--the PIMs aren't updated or corrected nearly as often. Not totally sure on that though.
Makes sense, except that even below 24 the thing rarely comes on.
 

ProudPilot

Aeronautics Geek
There was something about it had to be below 24 for 30 seconds or more in a CFI meeting one time, not sure if it was written down. If using it on stage checks the students got bonus points if they caught it early, passed if they dealt with the situation appropriately after the alarm, and failed if they heard the alarm, didn't react, and told me my epaulets weren't cool.

Simulating is good, but I'd rather see a scan anyways. The G1000 has a few things where parameters have to be just right to get the aural. I miss the seminole annunciator panels some days.
 

pwttogfk

Well-Known Member
Sure seems to work to me...it takes a pretty long time to get the battery depleted enough to get the chime though. The system is trying to suppress nuisance alarms, hence why it's so tough to simulate without an actual alternator failure. I have had an alternator fail on me, and it worked nicely to get my attention. For training, though, I liked the Warrior with its "dumb" annunciator panel and breaker panel right by the CFI that let me be sneaky (with breakers that were OK to pull).

Sent from my PC36100 using Tapatalk 2
 

Roger Roger

Paid to sleep, fly for fun
Makes sense, except that even below 24 the thing rarely comes on.
I was thinking for some reason it was even below 24 volts...something like 22.5. Maybe I'm getting it mixed up with what voltage "activates" the standby battery, though it's been so long since I've flown a 172R that I'm probably just talking gibberish.
 

p1l07m4n

SF340 Pirate, First Mate
I know our G1000s in the DA42NG are having the same issues. Our mechanics think that it is related to the old Thielert engines. They have been working with Diamond and Garmin to try and get the situation resolved. Basically in ours, we will have one alternator indicating say 71 amps, and the other -2. There were many cancelled flights, and mx inspections, and both alternators are working correctly. I believe they have been making the fixes here recently because I have seen this situation less and less. Who knows really?
 
Top