About 45 minutes into a 70 minute flight, cruising along at 10,000 feet, I looked over to see my engine monitor gauge flashing “25.0 VOLTS” at me (it’s a 28 volt system). I cross checked with the ammeter above it, which was showing a discharge. Then, a few seconds later, my low voltage light began glowing bright red. It appeared I was having an alternator failure. I followed the “LOW VOLTAGE” emergency checklist, and found the voltage regulator circuit breaker had popped out. I reset it, and the system began charging for about 20 seconds, but then it popped out again. I tried calling our base in Tarakan on the HF radio, about 100 miles away, but apparently the gremlins that took away my voltage regulator also got into the HF radio, because they couldn’t hear anything I was saying. I was now only about 20 minutes to my destination of Long Metun, well over halfway there, and the weather was nice, so I wrote down my position, time, and ETA, and turned off the master switch to the electrical system in order to preserve my battery power. Thankfully, unlike a car, an airplane’s engine is not dependent on the battery (at least after starting), for situations such as this.
Just before landing, I switched on the power briefly to lower the flaps, and tried to contact our base again to tell them I was landing. No answer. After landing, I looked under the panel to see if I could find out what was causing that circuit breaker to pop. I opened the cowl and looked at the alternator and voltage regulator. Everything looked normal. It had now been over 45 minutes since anyone had heard from me, and they would begin looking for me soon if they didn’t hear anything. So, I and the airstrip agents made the 15 minute hike into the village to use their HF radio. After telling them I was OK, I got a waiver from our chief pilot to make the one-and-a-half hour flight back to Tarakan, since I’d be without an alternator and flying “in the dark” most of the way. I was disappointed since I’d specially arranged my schedule that day to do some church flights for several folks out of Long Metun: two pastor’s wives and their children were heading home to two different villages, one pastor was heading to Malinau, and there was a medical patient in another village I was to pick up. They were also pretty disappointed.
I told them I was going to have to head straight to Tarakan without passengers, but if for some reason I started the plane and it began working again, I’d shut down and they could get on board. Well, someone must have been praying hard, because sure enough, when I started it up, everything was working normally! I made it the rest of the day without another problem with the electrical system. (We still haven’t figured out what caused that circuit breaker to pop, and we’ve flown it several days since it happened).