An alternator as used in GA (a standard motor vehicle 3 phase alternator) has no failure mechanism which can be “reset”.
What you do get on the electronic voltage regulators, like e.g. the Lamar one, is an overvoltage protection circuit which kills the field current if the alternator output goes above say 18/36V (for 12V/24V systems respectively) and interrupting the supply to the regulator (by interrupting the field current CB) resets this.
Yes I agree that an alternator failure would not bring down a PA28. These were Brits and thus prob99 flying with an Ipad for navigation. You would lose comms however; almost nobody in the wider PPL population carries a handheld radio.
Having an alternator voltage reg trip out due to UNDERvoltage is deeply dodgy… Does the accident aircraft really have such a thing?
Unfortunately I am not that familiar with 19th century electrics…
Antonio wrote:
THis PA-28 does not look so different…if they had a vacuum AI (so it looks) and some independent GPS navigation, then the alternator loss, by itself and if it did happen, did not have to mean loss of control or awareness
I don’t think an alternator failure will cause such fuss (if you have a simple plan for it before hand), however, if you try to debug/fix it in the air one may cause loss of awareness, especially after 2h in IMC
Few hours after skill-test, I had an electrical failure just after getting contact with tower in a sunny day, my first “out of box reflex” was to get some cell reception by flying low, called the tower by phone (I find it difficult to fly while speaking on phone with weak signal, I a sunny day I had +/-500ft height changes while flying & calling 
At the end of it, I decided to join the circuit and land (ATC suggested a nice read of radio failures protocols but they were far more happy for me to come and land rather than go back to “London Area” with no radio)
It turns out some fuses have pop out, how easy to see and fix in the air? well not that easy, you have to by push few fuses in while few other pop out, G430/COMM/XPDR goes back to factory setting, you have to open the map note & dial frequencies, switch on comm1/comm2, switch off nav1/nav2, it took 15min on the ground after I vacated the runway to fix before I can “call for taxi”…
Antonio wrote:
When they do, it may contain a reference to loss-of-comm if it did happen.
I will not use my cell phone nor debug an electrical failure while in IMC, but I am happy to fly as many 2min triangles above clouds until escorts comes in (subject to endurance)
FWIW I’ve had an alternator failure on an Archer II once over Scotland in less than ideal weather conditions. Upon noticing the ammeter stuck at zero, I could bring back the alternator for some time by switching it off and on again. After a few iterations, this didn’t work anymore either. Switching off all unnecessary equipment and lights, we could make it from Barra to Dundee with enough battery to the end for the radio.
The mechanic in Dundee changed the regulator and could get it back to work but said that someone would have to spend more time debugging all the wires. It seems that if some wires and connections get older, their resistance may increase to the point where the regulator won’t compensate for this any more. The plane had also developed a jumping charging current, manifesting itself in the ammeter needle swinging back and forth in 2 sec intervals.
As it’s a club plane I don’t have the full detail, but from what I heard the main battery switch and the regulator have been changed. It works perfectly stable now again.
Peter wrote:
An alternator as used in GA (a standard motor vehicle 3 phase alternator) has no failure mechanism which can be “reset”.
Please don’t mark words. It is the overvoltage relay which is reset. Quote from a typical PA28 emergency checklist:
ALTERNATOR FAILURE
Verify failure
Reduce electrical load as much as possible
Alternator circuit breakers ……. CHECK
Alt switch ……. OFF (for 1 second), then ON
If no output
Alt switch ……. OFF
Reduce electrical load and land as soon as practical
Having once encountered an alternator failure myself in a TB20, I recall that the procedure is similar in that aircraft.
Having once encountered an alternator failure myself on a TB20, I recall that the procedure is similar in that aircraft.
Exactly – when I got new alternator with new engine in my TB20, after few hours it started to fail within 5 min of flying. Turning off and on gave it next 5 min of functioning. I flew like that for almost an hour and while working it was supplying the aircraft with current. Lycoming immediately sent me new one and after replacing it everything was ok.
boscomantico wrote:
The other one on board was a very experienced pilot who featured in a couple of videos of The Flying Reporter.
Sadly it is Simon Moores, yes, he did banner towing for few editions of “We are Festival” at Damyns Hall, a very skilled pilot…
Peter wrote:
I meant what does it actually do?
It’s just the typical IT first attempt to fix something – turn it off then turn it on again.
It does sometimes work even with the stone age stuff. On my night VFR training in the US, we lost the alternator (in a C172N) about halfway through the night cross country. We turned around and came home, but turning the alternator side of the master switch off then turning it back on again restored operation.
alioth wrote:
It’s just the typical IT first attempt to fix something – turn it off then turn it on again.
Not really. There could be spurious trips of the overvoltage relay and “cycling” the alternator is usually the only way you can reset it.
I agree. I’ve had to reset my RV10 alternator a couple of times for no apparent reason. It must have been a hundred hours since last reset and it’s been good as gold.
My gazelle helicopter has two push buttons for resetting the alternator and generator. Apparently they need the odd reset. Not had one yet though.
