Alternator Circuit Breaker

[texasag93]

Leaving AUS yesterday, I looked at the alternator charging indicator and it was discharging.


I looked and the alternator circuit breaker had popped.

My training included basic "what to do" with this. Push the breaker back in, and watch the indicator. If it pops again, turn off the alternator at the master and land. If it does not pop again, you are fine.


The indicator showed charging about 50% to the maximum that the guage would indicate for about 20 minutes, then decreased to 25% for 15 minutes, and then normal for the rest of the flight.


I called the A&P member of our club and told him about it.


Is it a short? A one time event?


Thanks!

 

[Capt. Geoffrey Thorpe]

20 minutes at max charge? That's a LOW battery. Any reason for the battery being real low? Could the alternator have been offline for quite a while before you noticed?

 

[texasag93]

It was at 50% max charge and then backed down.

The airplane was parked overnight after I flew from DTO to AUS (about 180nm) and it was charging normally on that trip.

It started and all electronics were working. All other instruments were working within normal ranges.

 

[texasag93]

20 minutes at max charge? That's a LOW battery. Any reason for the battery being real low? Could the alternator have been offline for quite a while before you noticed?

I was less than 10 minutes into the flight. Getting Flight Follow, taxi, and run up was about 10 minutes. So total time from start was less than 20 minutes.

 

[flyingmoose]

As long as it didn't pop again shouldn't be a problem. I know everyone hates when you say it could have just been random, but those things happen. The high charge rate is from the alt trying to get the battery charged back up. If it happens again then I would look more into it.
Cheers

 

[denverpilot]

Most POHs cover it. Some say leave it out and land, others say try one reset. Since 40-50 amps will do a good job of starting a fire at 12/24 VDC, choose wisely. (Like maybe delay pushing that breaker back in until you're over a suitable landing site.)

 

[Clark1961]

Most POHs cover it. Some say leave it out and land, others say try one reset. Since 40-50 amps will do a good job of starting a fire at 12/24 VDC, choose wisely. (Like maybe delay pushing that breaker back in until you're over a suitable landing site.)

This is good advise. My primary flight instructor liked to "fiddle" with things. I had a heck of a time getting him to do nothing with a failed system until we were close to a safe landing spot.

 

[denverpilot]

This is good advise. My primary flight instructor liked to "fiddle" with things. I had a heck of a time getting him to do nothing with a failed system until we were close to a safe landing spot.

The POH assumes a certain level of intelligence.

 

[Capt. Geoffrey Thorpe]

The indicator showed charging about 50% to the maximum that the guage would indicate for about 20 minutes, then decreased to 25% for 15 minutes, and then normal for the rest of the flight.

It was at 50% max charge and then backed down.

The airplane was parked overnight after I flew from DTO to AUS (about 180nm) and it was charging normally on that trip.

It started and all electronics were working. All other instruments were working within normal ranges.

I wouldn't assume that 50% of the gauge is 50% of the charge capability.

It really sounds like the battery was low but not flat - perhaps something got left on overnight? If it needed a lot of charge that may have pushed the breaker over the edge while running at full charge capacity.

Another possibility was that it was overcharging due to a faulty regulator. A quick check with a voltmeter wouldn't be a bad idea.

 

[texasag93]

I wouldn't assume that 50% of the gauge is 50% of the charge capability.

True.

It really sounds like the battery was low but not flat - perhaps something got left on overnight? If it needed a lot of charge that may have pushed the breaker over the edge while running at full charge capacity.

I cannot say one way or the other, I am going to check it tomorrow.

Another possibility was that it was overcharging due to a faulty regulator. A quick check with a voltmeter wouldn't be a bad idea.

I will check with the A&P and see what he says.

I hope that it was something easy like I left something on....

 

[denverpilot]

I wouldn't assume that 50% of the gauge is 50% of the charge capability.

Agreed.

Most ammeters used in light aircraft aren't calibrated to anything and have no marks other than the center. Above that, charging, below that, discharging.

Turn some stuff off when discharging, it'll move some toward the center but not typically a calibrated amount.