This is an excerpt from a report made to the Aviation Safety Reporting System. The narrative is written by the pilot, rather than FAA or NTSB officials. To maintain anonymity, many details, such as aircraft model or airport, are often scrubbed from the reports.
The previous afternoon, the Piper PA-28 had been worked on by an A&P and returned to service for a fault in the electrical charging system.
Upon start-up the next morning, the alternator failed to come online as evidenced by the ammeter reading zero.
After a brief phone call to the mechanic, I was advised to try briefly cycling the master switch, which produced no results. The mechanic said he would drive to the airport to look at the problem.
In the meantime, I read through the Pilot Operating Handbook (POH) which, being from 1964, is not very detailed.
It does, however, describe resetting the over-voltage relay by turning off the master switch for a full 30 seconds. I elected to shut the plane down by pulling the mixture and turned off the master as well. After more than 30 seconds, I restarted the aircraft and the alternator came online normally.
To verify everything was working, I ran the engine up to about 1,700 rpm for 5-10 seconds and also switched the avionics on/off two or three times. Everything reacted normally with the ammeter showing more load as devices were turned on.
I proceeded with the 20-minute flight to my destination where I was to meet another person for a local flight. About two miles from my destination (in Class E airspace), the transmit on the radio produced static, and I suspected low voltage. I was able to land normally.
I sat on the ramp for about 20-25 minutes with the engine at fast-idle and all avionics turned off, in the hopes of reducing the load so that the battery would better charge.
After turning the avionics back on, we departed normally and flew for about an hour with things working as expected.
When returning to the airport to drop off my passenger, about two miles from the airport, the electrical system failed due to what seemed like low voltage. We used a handheld radio to enter the pattern while making radio calls and landed normally. We were the only aircraft using the airport at the time.
While we had the avionics on during flight, there is a chance that due to the possibly low voltage, our ADS-B signal became inoperative.
After landing back at ZZZ, we called a mechanic to come service the airplane with a fresh battery so we could have ample electrical power for the short flight back to our home base where the charging system could be examined.
There is no good way to know if our ADS-B was fully operational near the end of each flight as the voltage appeared to drop to a low state. The electrically powered fuel gauges and electric fuel pump worked normally at all times as they require only small amounts of power.
Primary Problem: Aircraft
ACN: 1907992
With over 35 years behind me as an FAA certified A&P and holder of an Inspection Authorization for over 20 years I can tell you that the ultimate responsibility for the airworthiness of an aircraft is the owner/operator. He or she must ascertain that all maintenance is performed to FAA approved standards and meets manufacturers requirements. All appl icable Airworthiness Directives and Service Bulletins must be complied with and signed off in the maintenance logbook as well. Depending upon if the aircraft is operated under Part 91, 121, 135, etc. Mandatory S.B.s may or may not be required. It is up to the owner/operator to ensure compliance.
I say this because some owners have failed to see that aluminum wiring was replaced years ago with copper wiring. This can cause the problem.
And if this had ended in a mishap, it probably would have been blamed on the Mechanic.
FYI the correct alternator is a Chrysler alternator and voltage regulator per the OEM Piper parts manual. Exact same part numbers because they are the exact same parts. This is the ONLY known automotive parts in all the aviation industry that I have seen in 40 years.
Now, there may be newer approved part numbers for newer versions of voltage regulators-with extra features I.e. over voltage protection built in. Still the original Chrysler part numbers are valid for a Cherokee.
I agree 200%, Jim. I owned a ’67 PA28-140 w/ only a load meter and hated it. Even an airplane with an ammeter isn’t sufficiently instrumented. Years ago, I had three simultaneous problems with my 172 but each masked one another. The OEM ammeter had failed so it always seemed to indicate zero amps or a fully charged condition. The voltage regulator wasn’t working correctly and wound up weakening the battery so it never had a full charge. The Piper setup w/ the load meter is worse and doesn’t really serve any purpose; you know you’re presenting the electrical system with a load but you don’t know if the battery is being charged in the process.
As you say, having BOTH a voltmeter and ammeter tells you everything you want to know about the charging system. The EI VA-1A is a great instrument that serves both purposes. There are others.
While I’m on this subject, newer car charging systems are controlled by the onboard computer vs a discrete regulator. To eke a bit more mpg, they limit the amount of charge so the batteries never really get a full up “bulk” charge. Sitting in a partially charged condition, sulfation begins and that’s the start of a shorter life for the battery as well as less than the rated amp-hour capacity when it’s in use. I STRONGLY recommend vehicles get a full ‘bulk’ charge a couple times a month from an external charger. I have a seldom used pickup in my hangar which is on a hand-picked trickle charger putting out 13.4v. 24/7/365 unless I’m running it. THAT battery is now … 17+ years old !! Sulfation is the enemy of batteries and keeping ’em fully charged is key to keeping ’em happy and living a long time.
I recall that about 50 years ago a customer came to me for an oil and filter change on his Cherokee 180. After uncowling the engine and while draining the oil, I did a visual check of the engine, and noticed that the customary Chrysler-type alternator didn’t appear correct. I checked, and there was no Piper or Lycoming part number evident. The owner said that a friend of his had recently installed it, having obtained the the unit from a local auto parts store. I told the owner that this installation was illegal as the replacement part was not approved for use on aircraft as it did not come from the TC/PC holder, or if otherwise obtained, did not come from an FAA-PMA holder. In addition, I showed him that due to the orientation of the alternator on the Lycoming engine, it turned in the opposite direction than with an automotive application. This meant that the alternator cooling fan also turned backwards, and could not supply cooling air to the unit. Further flight operation would likely cause the alternator to overheat and fail in the near future!
Did you get that car alternator at NAPA – national aircraft parts association? 🙂
I don’t know why Piper ever decided to use a loadmeter vs an ammeter. An ammeter will indicate that the battery is being charged, while a loadmeter shows the system amp load, but no indication of the battery being charged
All aircraft need a voltmeter to show that the alternator/ voltage regulator is operating at the required voltage, usually 14.0- 14.5 volts [ for a 12 volt system], with the ammeter showing the charging current. If the voltage is set too low, the battery will not be fully recharged and will have less than the rated amp-hour capacity.
I had the same problem, same aircraft. I put a regular dodge car alternator in and never had another problem
Wondering why this pilot chose to report something that seems like an appropriate response to the problem. I have had several malfunctions of equipment (stuck airspeed indicator, total electrical failure, loose throttle cable, etc.). In each case the problem was dealt with without incident – nothing to report except to the maintenance shop.
I was thinking the same thing when I read this. I assume he was worried about losing ADS-B Out in an area where it was required.
Of course that is the substrate of the report