Someone sent me this survey from a US homebuilder site
The first two types are standard automotive types. The B&C are better known for standby/backup alternators but they also do more normal ones.
The problem is that on a certified aircraft it is not easy to just change the alternator model… I recall asking somewhere about the Plane Power ones years ago and it was claimed to be impossible on the TB20. However, how can this be a “basic change to the electrical system”? Under EASA, I have no idea but I believe that short of having an FAA-PMA and the aircraft type being on the PMA list, you can’t do it.
Interesting. But in my experience aviation engineers are as about as skillful as car mechanics when it comes to ‘alternator’ problems. In other words, almost any type of electrical problem results in a knee – jerk ‘change the alternator’ reaction. Of course, the ‘old’ alternator is spirited away such that when the fault recurs, there’s no question of putting it back and refunding the money spent. In reality of course this may be the best use of resources, since any attempt to find out what’s actually wrong might involve expensive head scratching, brain-ache and horror of horrors, understanding the problem.
In my own case, an ‘alternator’ problem (low voltage light coming on in flight) was not cured by changing the alternator, voltage regulator, low voltage light, overvoltage cutout and various wires. Each episode of brute force trial and error resulted in a brief remission of 10-20 Hrs, just enough to recover false confidence, so that when it failed again it would be in the middle of the Baltic or something. It was eventually fixed when one day, during one of the in flight failures I noticed that lightly flicking (Not pushing or pulling) the cap of the field CB restored power. That £1000 (gross cost) aviation quality CB still sits on my desk today.
So I’m wondering how many of these alternator failures above actually were caused by the alternator, especially in the case of the automotive ones.
I was about to exchange my alternator as I have an intermittent flickering of the Alt light, when all consumers are on. The voltage indicator momentarily drops from 28V to about 22V and then half my electrical instruments switch off. This doesn‘t happen when I switch off some of the heavy consumers.
I had the shop check the alternator (not a benchtest though) and they said it showed no malfunctions.
My a&p thinks it could be the main avionics switches as sometimes, especially when the aircraft was sitting in the cold I have to activate the main switch a few times before it turns on the battery. Does this make any sense?
Aveling wrote:
In my own case, an ‘alternator’ problem (low voltage light coming on in flight) was not cured by changing the alternator, voltage regulator, low voltage light, overvoltage cutout and various wires.
I had almost exactly the same situation, with the low voltage light being the one on my electrically controlled propeller…. Which BTW indicated that I’d lost propeller control. The eventual solution was to a fix a bad airframe ground on the control unit, artfully hidden by non-conductive washers etc. Some may be familiar with the acronym ‘DPO’ (for D*psh*t Previous Owner).
The good news was that my existing alternator was at that time 40 years old without overhaul, and a new one was probably a good idea anyway.
The 36 year old alternator in my C182 packed up late last year. I was advised to look at National Air Parts Inc. and bought a PMA unit from them. Nice to deal with and very knowledgeable. Maybe worth a look if you need an Alternator.
Whether they have approval for a TB20 you’ll need to ask. C182 dead easy, there are STCs for nearly anything on a C182.
I too had the “faulty” alternator run-around on a Datsun car in the 1970s…
However I wonder why such a dodgy procedure would be taking place on the first two but not on the B&C? One reason might be a self-selecting owner population for the last type, which knows more about how things work. Social research can be hard to do well because of such factors. But that whole survey was from Vans which is mainly an RV site.
We have an electrical guage with 2 pointers for oil temperature and pressure.
The oil pressure went down fast. Reducing RPM held it steady, for the flight home. The temperature remained steady. The problem proved to be intermittent.
A lot of work failed to solve the intermittent problem, until it was noticed that:
the wire for the “starter engaged” light was loose, and flapping to earth against the engine. Nowhere near the sender. Fixing it solved the problem.
Explanation??
@wigglyamp might have an idea…?
Bad wiring is sooo common. I was looking at one plane the other day… a nice IFR type, often used for AOC work especially sightseeing. The standard of wiring would not be tolerated in a Vauxhall Viva in 1970. But the wiring was current stuff.
I have seen several Alternator “issues” being related to the Field wire system.
Often a bad ALT switch will make the AMP meter jump all over the place, with the alternator often jumping off line.
Same goes for the Circuit Breaker.
I have seen several aircraft where the Alternator and Regulator is changed over and over agin without solving the issue.
The faults are often intermittent and hard to troubleshoot.
Rewiring or controlling the field circuit is a cheap way to troubleshoot.
Flickering amp meter is also a good indication that the Field is being disturbed.
The Cessna double Batt/ALT switch is famous for being the smoking gun. At 15$ its worth to have a spare in the hangar.
Then again, corrosion on the bigger cables can cause issues too.
