nigelspeedy
Well Known Member
After 40 hours flight time my Plane Power AL 12-EI60/B alternator failed. My aircraft has a Lithium Iron Phosphate battery, VPX-Pro, and Skyview EFIS and a couple of Garmin radios. Prior to this failure the electrical system was very consistent at around 13 amps at 14.1 volts during normal operations. The day it failed I was about 60 minutes into the flight, the alternator output went to zero and the bus voltage fell back to the battery level in about 1 second. Luckily I have a B&C SD-8 backup and with just a little load shedding life went on. On the ground I found that the field circuit was energized with the alternator switch in the ON position. If I turned the pulley by hand you could feel it 'cogging'. If you turned the pulley with a power drill in the correct direction with the field circuit energized there was no electrical output but the case/body of the alternator got very hot in just 10 seconds. Changing the voltage regulator did not fix the problem. So I take it off and send it back for warranty. But being the impatient kind of guy I am and not wanting to be on the ground for weeks I order a replacement rationalizing that I will have a spare. Unfortunately after 3 hours the second alternator also fails. This time the engine monitor download shows that after an hour of flight time the alternator current output goes from being nice and steady at 14 amps to 14 +/- 4 amps for about 10 minutes then over the period of a further minute drops to zero, at the same time the voltage drops back to the battery level. Again turning on the backup B&C returned life to normal.
What are the most likely causes of alternator failure?
Any suggestions would be greatly appreciated.
Cheers
Nigel
What are the most likely causes of alternator failure?
Any suggestions would be greatly appreciated.
Cheers
Nigel