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Another Plane power issue

S2D

MEMBER
Montana
Wirewienie

Since you had such good luck diagnosing Gordons problem hoping you could figure mine out.

Cessna Agtruck running the plane power system.
Ran fine for a couple years.
Suddenly this summer it starts spiking and kicking out for a while then kicks back in
repeating the process til it finally burnt the regulator out.

Pulled the cowling and found severe fuel leak in that area. (yea thats a whole nother "Holy $hit" story !!!!!)

Fixed the fuel leak and replaced the regulator.

everything would work fine under 1000 rpm but above that, same story til finally burnt out another regulator.

So now I finally get it in the shop for the winter annual and have to figure out whats causing that !!

Wire shorting ?? loose ??? vibration induced ????

thanks
Brian
 
What did the voltage do during these episodes? Was the voltage constant at 14.2 volts during normal operation? Was it 'kicking out' for high voltage or high current?

Web
 
Ok, listen up. The next guy installing a Plane-Power alternator, contact me! I'm making your wire harness for your new charging system!

Just trying to save time . . . .

Web
 
What did the voltage do during these episodes? Was the voltage constant at 14.2 volts during normal operation? Was it 'kicking out' for high voltage or high current?

Web
The ammeter was pegging. Doesnt have voltmeter.
 
Ok, listen up. The next guy installing a Plane-Power alternator, contact me! I'm making your wire harness for your new charging system!

Just trying to save time . . . .

Web
Yea im sure that would help.
I replaced a lot of worn out wiring about 8 years ago.
But these things take a lot of abuse and im sure a lot more is going to get replaced before i find the problem.
 
The pegged ammeter obviously shows huge current flow. Put a digital voltmeter on the bus and check it when the system acts up. In general, normal or lower voltage means a shorted wire or contact. Higher than normal voltage means possible voltage regulator issues.

Is the ammeter installed in the alternator output lead or on the main bus feed? If on the main bus feed, does it peg to the positive side of the ammeter or to the negative side?

Web

P.S. I'll need the length of wires required if you have a non standard Cessna install.
 
P.S. I'll need the length of wires required if you have a non standard Cessna install.

You mean you have the data to make a complete harness for a cessna Ag truck?, Or are you just talking about the alternator circuit?


Ill check what you asked when i get back , I gave the mechanic enough other discrepancies to fix to keep him busy for a week or two.



Sent from my E6910 using Tapatalk
 
Year/serial number of aircraft
List of all avionics by make and model
List of accessories (I'll need diagrams with the ag items. Don't have much access to that stuff)
List of all items such as nav or landing lights that have been changed over to aftermarket stuff.
Do you want factory markings on airframe wiring?
All wires will mil-spec M22759/34-* or M27500-* wiring, white, with laser engraved markings

Web
 
Wow.
The pilot that owns and flies it for me would love that. Hes always claimed its jinxed.

Ill see what i can come up with.

No avionics, just gps, flagger and crophawk.



Sent from my E6910 using Tapatalk
 
We wound up going thru the wiring, eliminating some possible problems, tightening some grounds etc.
Will see how that works out before ensuing this route.
 
Wow, Web. That is a neat trick, building an entire harness. I did it once on an old Ford - I was really puzzled about this heavy wire that seemed to connect everything. That was in high school, before I learned about circulating grounds.

My Decathlon could use such an improvement - the smart folks at Bellanca made an accessible switch panel, and forgot to leave enough wire for it to flip open. Drives me nuts when a switch fails (so far, two). If I ever have to recover, it gets a new harness. Yes, Plane Power. No, it has been trouble-free.
 
I have a customer that wants a new light weight alternator, I am thinking of just sticking a 89 Geo Metro one on...at least I can replace it for $65.00 which is way cheaper than the Plane power ones. I do know he would like a new wiring harness too, but that may happen at recover. Tim
 
I am thinking of just sticking a 89 Geo Metro one on...

One of my rants, so if you've heard it before, just bear with me.

Automotive alternators with internal regs draw the regulator power from inside the alternator. Not a problem under normal conditions. The field current is controlled by a transistor inside the regulator. When semiconductors fail, 99% of the time its to a shorted state. In a regulator, this means that the shorted transistor controlling the field current will simply dump as much current into the field as is available. This produces high voltage. This, in turn, means more current will be available to the field, which increases the output voltage again. Etc, etc, etc.

Just pull the output breaker? Ok. When that happens, you'll disconnect the alternator from the bus bar, but the alternator will not stop producing power. Remember that the reg gets it's power from inside the alternator which is still producing. So even with the alternator disconnected from the bus, it will continue in an over voltage state until the engine is shut down or it burns up. I've opened car hoods and seen the melted copper and solder slung around. I will NEVER take a chance on that happening in an aircraft.

Web
 
Proper routing and securing seems to be the most important thing.
After replacing a couple worn wires and securing properly, seems to function normally with Gordon's new regulator !!!
 
One of my rants, so if you've heard it before, just bear with me.

Automotive alternators with internal regs draw the regulator power from inside the alternator. Not a problem under normal conditions. The field current is controlled by a transistor inside the regulator. When semiconductors fail, 99% of the time its to a shorted state. In a regulator, this means that the shorted transistor controlling the field current will simply dump as much current into the field as is available. This produces high voltage. This, in turn, means more current will be available to the field, which increases the output voltage again. Etc, etc, etc.

Just pull the output breaker? Ok. When that happens, you'll disconnect the alternator from the bus bar, but the alternator will not stop producing power. Remember that the reg gets it's power from inside the alternator which is still producing. So even with the alternator disconnected from the bus, it will continue in an over voltage state until the engine is shut down or it burns up. I've opened car hoods and seen the melted copper and solder slung around. I will NEVER take a chance on that happening in an aircraft.

Web

And if you EVER consider an EarthX battery, never install one with an alternator with an internal regulator!


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Why would that be? Considering EarthX batteries are for ATV's, UTV's, race cars, motorcycles, sleds (snowmobiles), ...... it would seem they are designed to work with automotive type alternators.
 
I am still using an alternator that was used on the Honda Civic. Put it on the original build 24 yrs ago and have had no problems so still running it. It has an external regulator and I have been running the EarthX battery for the last year and a half. I did use a pulley that used to be available at Spruce to slow the alt. speed because of the large aircraft flywheel. It is small and light (30amp ) and works very well for me. Would replace with same if i needed one.
 
I have a bit different opinion about internal regulators. My background has been a mix of aircraft and road race and rally cars. These cars are about the harshest environment out there with the driveline solidly mounted to the chassis. The rally cars run very high current load with all the lighting for long periods. Most every car has been either 4 or 6 cylinder which have rather high vibration loads.
In the mid 70s I saw one fresh rebuilt alternator fail high when new, this was the last external reg unit in a car I have touched. A bad alternator that did damage. Every other charging system failure went low causing no damage whatsoever, and that has not been many failures. Most currently one road race car had repeated wire failures right at the alternator during track sessions all resulting in DNFs, tiny batteries do not keep fuel injected engines alive very long.
The common failure I have seen in aircraft has been a failed crimp terminal at the alternator causing system failure. Once I started replacing the field wire so I could get a good strain relief those failures became rare.
My own airplane will use a Denso or Mitsubishi alternator as every race car has, no off brand look alike with components sourced from who knows where.
 
It has an external regulator and I have been running the EarthX battery for the last year and a half.

External automotive charging systems are what the stock systems are on small aircraft. The wiring between the reg and alternator allow for a manual control switch (one pole of the master switch) to be installed. This switch is what turns off the regulator power to de energize the field.

Web
 
I have a bit different opinion about internal regulators. My background has been a mix of aircraft and road race and rally cars. These cars are about the harshest environment out there with the driveline solidly mounted to the chassis. The rally cars run very high current load with all the lighting for long periods. Most every car has been either 4 or 6 cylinder which have rather high vibration loads.
In the mid 70s I saw one fresh rebuilt alternator fail high when new, this was the last external reg unit in a car I have touched. A bad alternator that did damage. Every other charging system failure went low causing no damage whatsoever, and that has not been many failures. Most currently one road race car had repeated wire failures right at the alternator during track sessions all resulting in DNFs, tiny batteries do not keep fuel injected engines alive very long.
The common failure I have seen in aircraft has been a failed crimp terminal at the alternator causing system failure. Once I started replacing the field wire so I could get a good strain relief those failures became rare.
My own airplane will use a Denso or Mitsubishi alternator as every race car has, no off brand look alike with components sourced from who knows where.

If I didn't do the installation, I can't help with bad wiring/poor connections, lol.
But as far as regulator failures, I stand by my original assessment. Just looking at the regulators, they tend to fail in a shorted mode. This is separate from alternator failures such as worn brushes or bearings. If this happens, there needs to be a means of disconnecting power from the alternator field to prevent continuous over voltage and over charging. Worse case scenario for even competition cars is to end up stalled out. Aircraft systems use a switch and breaker combination to control the field for safety, do you have a similar arrangement in the rally cars?

Web
 
In all the years of flying these cessna spray planes, we've had one runaway alternator.
Pilot said turning the master off didnt help.
Fried the guages but didnt hurt the wiring.
This system had an overvoltage sensor in it but that didnt stop it either.



Sent from my E6910 using Tapatalk
 
In all the years of flying these cessna spray planes, we've had one runaway alternator.
Pilot said turning the master off didnt help.
Fried the guages but didnt hurt the wiring.
This system had an overvoltage sensor in it but that didnt stop it either.
Just curious, was the voltage regulator an earlier electromechanical type or a newer solid state type?
 
In all the years of flying these cessna spray planes, we've had one runaway alternator.
Pilot said turning the master off didnt help.
Fried the guages but didnt hurt the wiring.
This system had an overvoltage sensor in it but that didnt stop it either.


Sent from my E6910 using Tapatalk

Sounds like it was mis wired. Shutting off the field switch should have de energized the reg system. And the fact that the OV relay didn't trip raises a HUGE red flag.

Web
 
Sounds like it was mis wired. Shutting off the field switch should have de energized the reg system. And the fact that the OV relay didn't trip raises a HUGE red flag.

Web
That hold true even if the field wire shorted to ground

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