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Plane Power Alternator Failure

nigelspeedy

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
 
Pair of Spares

You and Dan H have an affinity for spare PP alternators.

Do a search for "ALTERNATOR FAILURE" then scan down until you find "Alternator Fooled Me" by Dan H

Thankfully it looks like Dan has posted a direct link for you at Post #9. If yours has the same problem, it will be an easy fix.
 
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nigelspeedy said:
What are the most likely causes of alternator failure?
Click to expand...

I would have to say the cause could be choice of vendor. I have no experience with that alternator, but I would start looking at different options for your next alternator. Clearly your voltage regulator is working properly. Have you confirmed that your wiring is in good shape? However, I can't envision how wiring issues could cause the symptoms you are describing.

Larry
 
You mention an external regulator and I thought the PP's were internally regulated. I am sure you have researched this and installed accordingly, but thought I would mention it.

Larry
 
Most common issues with internal regulated alternators is the failed regulator due to heat. As the alternator is installed close to the engine, it gets a lot of heat from it. Check your blast tube.
The big benefit of a seperate alternator and regulator is that you could install the regulator with the sensitive electronics in a cooler area, e.g. behind the firewall.
B&C has great alternators available.
 
Sounds like I have the same setup as you do and I just went through the same type of issues with my PP alternator. Now I have a spare as well.

Like you I have a B&C 20 amp mounted to my accessory case and it gets me through the day but I am getting really tired of all the issues and will be looking for an alternative if the PP dies again soon.
 
Paul K said:
Sounds like I have the same setup as you do and I just went through the same type of issues with my PP alternator. Now I have a spare as well.

Like you I have a B&C 20 amp mounted to my accessory case and it gets me through the day but I am getting really tired of all the issues and will be looking for an alternative if the PP dies again soon.
Click to expand...

Gee, common thread is plane power alt, plus B and C back up alt and or B and C external voltage regulator with an internally regulated Plane Power alternator.

On our field we have about 15 RV's with most running plane power, cumulative hrs are probably in the 5000 range. NO plane power failures.

Mine personally has 1200 hours without any blast tube.

I admit to being "blissfully" unaware because my copy of "The Aero-Electric Connection" has been unopened for 15 years.
I decided to build my airplanes with the well proven Vans electrical drawing, simple and reliable.

I doubt the problem lies with the Plane Power Alternator!
 
If it had a contractor, and, If there was a short in the B+ wire back to the contractor, when it energized it would short the battery to ground. So that would be eliminated as the issue for the first alternator - unless the VPX is doing something funny in the magic box.

I would just treat the second alternator as a single failure until it is diagnosed as well. Did you test it too? Like an Autozone test?

It is extremely rare, but double component failures do happen. I have installed thousands of sets of ignition points cars. One day a Caddy was towed to a shop where I was working. (I had only done a few hundred at the time, a novice.) No fire, shorted points, replaced with a new set. Same result ??? Whhaaaat? The owner, a true master mechanic, did not miss a beat, he said, points are still shorted, replace with a (another) new set. I did and all worked. The first new set was shorted! New Delco. Lesson - never assume - coincidences do happen. Trouble shoot each occurrence independently until you find correlation.
 
Just a quick note, the failure with my PP alternator started as loss of voltage and when instructed by PP to remove the back cover and look at the brushes, ended up with several small plastic parts falling out. I also had it checked by an alternator shop and they said it was fine, it wasn't!

The electrical system I used is pretty basic as far as the connection between the alternator and the battery. can't get any simpler. I don't see any connection between what lies beyound the battery back to the panel etc. The stand-by alternator is only connected to the PP alternator via the common connection at the battery contactor. Never run both at the same time, in fact other than testing the stand-by alternator about once every 3 months, never run it at all.

The Aero-Electric Connection was my bible when I built the electrical system and I still consult it.
 
Paul K said:
Just a quick note, the failure with my PP alternator started as loss of voltage and when instructed by PP to remove the back cover and look at the brushes, ended up with several small plastic parts falling out. I also had it checked by an alternator shop and they said it was fine, it wasn't!

The electrical system I used is pretty basic as far as the connection between the alternator and the battery. can't get any simpler. I don't see any connection between what lies beyound the battery back to the panel etc. The stand-by alternator is only connected to the PP alternator via the common connection at the battery contactor. Never run both at the same time, in fact other than testing the stand-by alternator about once every 3 months, never run it at all.

The Aero-Electric Connection was my bible when I built the electrical system and I still consult it.
Click to expand...

I'll re-iterate my recommendation to look elsewhere for your next alternator. I am using an automotive ND Alt. - 55 amps, proper rotation for cooling, externally regulated (my preference) and a $45 cost (replacement if free via autozone warranty). If you want aviation grade, I have heard very good things about the B&C model.

Larry
 
BillL said:
A bit off topic, but Dan, what did the Hartzell guys say about the fretting on that connector? Are they adding the plug on the end of the wires to prevent so much motion transferred to the terminal?
Click to expand...

Have not seen Tommy lately. I'll call him tomorrow...if I don't forget.
 
same boat...

I also had my PP alternator fail (one day all of a sudden it went intermittent on/off in flight for 20 minutes, then just died), after about 250 hrs TT.
The subsequent interaction with Hartzell was, in my opinion, unsatisfactory. Basically they recommended replacing the regulator, which I did, and it did not solve the problem. Since they refused to sell me a regulator directly, I had to call Aicraft spruce, who had to order the regulator from them and have them drop ship it to me (which added a bunch of charges, I ended up paying about 115$ for a 50$ part). And no, they did not offer any warranty replacement (which is ok, the alternator was 6 years old, although, as I said had only 250 hrs).
Then, on close examination, i realized that 2 of the 4 wires from the STATOR coils were broken. So I called Hartzell again, asked them if they would sell a new stator (Answer: no) or if they would repair/overhaul my old stator (Answer: there is no overhaul procedure, you know all that FAA regulatory stuff..., to which I replied what regulatory stuff, it is an Experimental alternator! and they said you're right, but still no overhaul - seriously this is exactly what they told me).
So at the end I repaired my broken wires myself.
But this left me with the clear determination to choose a different vendor next time my alternator dies.
YMMV
Happy flying.
Geo.
 
Thanks for all the advice so far I'll report back once I have the issue resolved. Wish I'd bought the $7 replacement plug before I bought the $465 replacement alternator.


Note to self: "Self check the VAF before using brute force solve problems"

Cheers

Nige
 
So far I have had good luck with my PP ALT-FLEX. No blast tube but my nominal electrical load is only about 60% of design full load and that is with the air conditioning on.
 
So knowing that the aircraft wiring and plug were common to both failures and seeing Dan's earlier thread I took a pair of fine needle nose pliers to sockets in the plug and gave them a gentle squeeze. Well I gently squeezed two of the three, the third one I was a bit heavy handed. Reinstalled the alternator and went flying. It worked for about 45 minutes then failed again. So at this point I am thinking the plug is definitely a culprit and will go down the route or installing the replacement plug that Dan H suggested. More details to follow.
Cheers
Nigel
 
Update.

As one of the previous posters noted PP was not that great initially and did not seem to care that it had failed at 40 hours and told me to buy a new regulator from Spruce. Spruce does not carry them so you have to pay Spruce to pay PP to drop ship it so that adds up to about $75 shipping and charges for a $50 part. Not so good, and it did not fix it so I shipped the alternator back to them under a warranty RMA.

Today I got a response that they found the following "Unit made knocking noise at low RPM on test stand. Slip ring end housing bearing bore is worn. Allowed for rotor/stator contact. 3 out of 4 stator leads broken-suspect due to vibration". They were nice enough to send a replacement alternator though.

So going forward I'll replace the plug with the one Dan H suggested and reinstall the replacement alternator. I made a little heat shield which will also protect the fuel line from the fuel servo as a bonus.

What does worry me a bit though is the vibration as a suspected cause. The motor was balanced nicely on assembly and subsequently I used a Dyna-Vibe to balance it and got a very good result. Can my 10:1 engine really be that harsh? Wouldn't the belt absorb most of the torsional vibration? I guess the alternator is bolted to the case so its going to move with the engine.

Cheers

Nige
 
I had the same problem as Dan H's PP plug with my B&C alternator field plug. One day no charging. Pulled the Alt and ran it on a lath with power to the field, worked fine. Just about to buy another B&C regulator when I thought to check the plug.. The connector was loose, I squeezed it tight and it's been working fine ever since. Always check the little things.
 
nigelspeedy said:
Update.

As one of the previous posters noted PP was not that great initially and did not seem to care that it had failed at 40 hours and told me to buy a new regulator from Spruce. Spruce does not carry them so you have to pay Spruce to pay PP to drop ship it so that adds up to about $75 shipping and charges for a $50 part. Not so good, and it did not fix it so I shipped the alternator back to them under a warranty RMA.

Today I got a response that they found the following "Unit made knocking noise at low RPM on test stand. Slip ring end housing bearing bore is worn. Allowed for rotor/stator contact. 3 out of 4 stator leads broken-suspect due to vibration". They were nice enough to send a replacement alternator though.

So going forward I'll replace the plug with the one Dan H suggested and reinstall the replacement alternator. I made a little heat shield which will also protect the fuel line from the fuel servo as a bonus.

What does worry me a bit though is the vibration as a suspected cause. The motor was balanced nicely on assembly and subsequently I used a Dyna-Vibe to balance it and got a very good result. Can my 10:1 engine really be that harsh? Wouldn't the belt absorb most of the torsional vibration? I guess the alternator is bolted to the case so its going to move with the engine.

Cheers

Nige
Click to expand...

While the compression ratio is a factor in the vibration on the engine, that alone should not become the prime suspect in this failure. The alternator is turning over 10,000 rpm. If it were a front bearing we could point to excessive belt tension, but the different issues point to the vibration as noted by Hartzell. Hopefully, they will be looking at the balance of their inbound components, among other possible causes. Stator wire breakage is pretty severe and yours was not the first.

As a minimum it is time for a good reliability engineer to study, gather data, and provide a definitive recommendation for solving this. Maybe, this is why B&C is always touting balance of their rotors.

By way of example, (you know I always have an example) a diesel engine can have 50g's at a head bolt. Spark ignited excitation is less, but it is not a massive hunk of cast iron either, so lets just say -our engines are "energetic". If your baffles are not falling off, you are probably OK.
 
Replacement alternator and plug fitted today and so far it has survived 2.0 hours. Hopefully it will live a long and productive life.
Cheers
Nige
 
nigelspeedy said:
Replacement alternator and plug fitted today and so far it has survived 2.0 hours. Hopefully it will live a long and productive life.
Cheers
Nige
Click to expand...

Good to hear Nige, I assume you potted the wire going into the plug with some sensor safe RTV?

Or . . . did Hartzell/PP begin installing plugs in those wire entrance holes?
 
FasGlas said:
I had the same problem as Dan H's PP plug with my B&C alternator field plug. One day no charging. Pulled the Alt and ran it on a lath with power to the field, worked fine. Just about to buy another B&C regulator when I thought to check the plug.. The connector was loose, I squeezed it tight and it's been working fine ever since. Always check the little things.
Click to expand...

Did your plug have strain relief plugs around the wires where they enter the plug or loose (open). B&C should have addressed every failure mode for their price.
 
The PP plug supplied does not have strain relief so I stuffed the holes around the wires with RTV to try and stop them fretting like Dan H experienced.
Cheers
Nige
 
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