generator to alternator

[bweyers]

Well, after more than half a century, the generator is going out on my 52 170b. Its been suggested I convert to an alternator. I'm looking for suggestions on the best way to go. Plane still has an O-300. Will this require a 337? Any other comments welcome...
Thanks
Bill

[blueldr]

I suggest you give serious consideration to having your GENERATOR rebuilt. With todays solid state avionics, there is little demand for more electrical power than can be supplied by your generator. The generator has a distinct advantage over the alternator in that its risidual magnetism will provide the ability to come on line,after a hand propped start, without having an external source of field excitation in the event of a completely dead battery.
This feature is probably more important to those who fly around out in the boonies, and is best accomplished with a jumper wire with a diode, or a momentary switched jumper circuit, on the master solenoid.

[Bruce Fenstermacher]

Bill,

A change to an alternator will require an approval of some sort either a one time by the feds or an STC which will be executed on a 337.

BL is right you will probably be hard pressed to exceed a generators capacity today but it could be done.

What you need to find out exactly is what engine and crank you have. You say you have a 0-300 but could it be a C-145-2? If a C-145-2 and you don't have a dampened crank like mine, you are limited to a 25 amp generator. You probably shouldn't be putting an alternator on it either. Most likely you have a dampened crank and can use up to a 35 amp generator. What is your current generator capacity? Good chance it's only a 20 amp. Of course any upgrade will require a higher rated voltage regulator and perhaps wiring changes as well.

[k0al]

I finally gave in and replaced my original 15 ampere generator with a JASCO 50 ampere alternator conversion. I had contemplated such a conversion for some time, but liked the ability to hand prop and have the old generator "bootstrap" itself into charging. In my case, the generator finally died, which is what put me over the edge.

For me it was a good decision, as the old generator would not carry all the lights and other electric devices unless the rpm was in the 1800 - 1900 rpm range. Thus unless on a night cross country, any night pattern work was a losing battle. The alternator carries everything at a fast idle.

The conversion came with the STC and good instructions.

Al

N5455C

[KevinS]

Hey Al

My generator also bit the dust last year. I too decided to go with the Jasco alternator kit and haven't had any problems as yet. Given that, I have a question for you or anyone else that may want to jump in as well regarding weight and balance. My mechanic replaced the generator with the alternator kit but did not re-do the weight and balance. The logbook says that the W&B changes were negligible. For my own curiosity, does anyone have a weight of the generator as well as the "moment" measurement? I would have thought that the alternator would have been a bit lighter.

Thanks

Kevin

[buzzlatka]

If you have the Jasco alternator, there is a big GOTCHA that can be missed
YOU MUST REMOVE THE ALTERNATOR EVERY 250HRS

We stumbled upon this in the back of the STC. I think it is called and ICA and
means In continuation of airworthiness or somthing like that. All STCs have them
and most basically say inspect at annual. This one in particular states that every 250 hours
you must remove the alternator and inspect and replace the bushing if needed.
In order to keep your plane airworthy you have to comply with these ICAs and must log them
in the logbook. The generic entry....Annual complete, everything complied with....will not
work.

This is kind of a pain when you fly your airplane a lot. Also good luck trying to get the correct bushing.
We did notice some wear and decided to replace it. After many calls to Jasco about a part number it took
2 tries at spruce and more phone calls to Jasco to get the correct part.
As I say, every time I order a part for this airplane, it doesn't fit or it is the wrong part#. No matter how much
I try or how sure I am of the part number. I will go into my records and try to find the correct part number.

[Bruce Fenstermacher]

ICA = Instructions for Continued Airworthiness.

It is not correct to say that all STCs have these. ICAs started sometime in the late 90's about two years or so before change 15 which made field approvals difficult.

STCs approved before this time will not have ICAs unless they have been updated.

It is correct that you must comply with all ICAs that apply to your aircraft to keep it airworthy.

[bweyers]

Thanks for all the feedback. The engine is indeed a c145-2, not an 0-300.

Ok, so lets say I decide to stick with the generator, rebuild or new? If rebuild, any suggested shops or can my A&P/IA do it.

Thanks guys....
Bill

[N2625U]

http://www.aerotechlou.com/generators.shtml

I had my generator rebuilt last year by these folks. The generator that was in my plane was also from them and lasted about 1500 hours.

[Kellym]

Thanks for all the feedback. The engine is indeed a c145-2, not an 0-300.

Ok, so lets say I decide to stick with the generator, rebuild or new? If rebuild, any suggested shops or can my A&P/IA do it.

Thanks guys....
Bill

I dealt with this situation about 13 years ago. The 35 amp generator has a poor seal arrangement, and oil was repeatedly damaging the commutator in the generator, and they were expensive to replace.
Cessna at one time sold a kit to make the conversion. HQ had a copy of the drawing for the kit, and 337s based on installing the kit. I used that to obtain the appropriate Ford alternator from Aerotech of Louisville, along with the right regulator. The only extra wiring I had to do was to install a circuit to control the field, with a pullable circuit breaker (5 amp). I used a circuit breaker for the output that matched the max current for the output wire, which was about 10 amps below the rated output of the alternator, as I had no need for the extra output, and didn't want to have to upgrade the wiring all the way to the panel bus with heavier wire. It worked fine for the remaining 4 years I had the plane. FSDO signed a 337 with no problem when presented with the existence of a factory drawing and previous 337s.

[GAHorn]

This is NOT intended as a criticism, but as a constructive critique:

Using a C.B. that is smaller than the capacity of the alternator adds risk of complete loss of generated electrical capacity inflight and is not a proper method of limiting alternator output. It also risks an electrical fire in the event of a failed C.B. (a common event.) And that method did not comply with the "factory drawing and previous 337s" and therefore the FAA field-approval was invalidated.

"bweyers wrote: Ok, so lets say I decide to stick with the generator, rebuild or new? If rebuild, any suggested shops or can my A&P/IA do it.

Thanks guys....
Bill"

The alternator has a similar oil-seal setup as the generator and is subject to the same failure mode. The oil seals are frequently installed improperly and/or with interference with the woodruff key. Sacramento Sky Ranch wrote about this issue years ago and it's likely that John out there can help troubleshoot that matter.

The generator rebuild option is much less expensive also. (About $200 versus $800-$1,000 PLUS labor.)

You don't say exactly what you mean by your generator is "going out". They are easily repaired. It might not be the generator at all. It could be the regulator. It could be the ammeter. (Have you read the Electrical Service Manual?) What symptoms are you having? Many "modern" mechanics are simply not well-versed with generators so they take the path of "parts-replacers" by suggesting a shotgun approach of conversion to alternator when there's no need for additional capacity.

It's unlikely there are any "new" generators so the only option is rebuild. This is also the least expensive route. Aerotech of Louisville is the best source, in my opinion. They know how to install the oil seal properly. http://www.aerotechlou.com

[Kellym]

[quote="gahorn"]This is NOT intended as a criticism, but as a constructive critique:

Using a C.B. that is smaller than the capacity of the alternator adds risk of complete loss of generated electrical capacity inflight and is not a proper method of limiting alternator output. It also risks an electrical fire in the event of a failed C.B. (a common event.) And that method did not comply with the "factory drawing and previous 337s" and therefore the FAA field-approval was invalidated.

"bweyers wrote: Ok, so lets say I decide to stick with the generator, rebuild or new? If rebuild, any suggested shops or can my A&P/IA do it.

Thanks guys....
Bill"
I disagree entirely. All circuit breakers are there to protect the WIRE, not the alternator, not to limit alternator output(which is fully done by the voltage regulator and overvoltage circuit). Your scenario would require failure of both the circuit breaker and the voltage regulator and the field circuit breaker. It also requires the circuit breaker to fail to trip, a far rarer failure mode than tripping at lower current than designed. You also need a load or direct short drawing more current than the circuit breaker capacity. You don't know the details of what was on the approved 337. The factory drawing was only used as supporting data, not as the actual data on the 337. The generator seal design repeatedly failed in short timeframes. The alternator seal did not.

[GAHorn]

...I used a circuit breaker for the output that matched the max current for the output wire, which was about 10 amps below the rated output of the alternator, as I had no need for the extra output, and didn't want to have to upgrade the wiring all the way to the panel bus with heavier wire. It worked fine for the remaining 4 years I had the plane. FSDO signed a 337 with no problem when presented with the existence of a factory drawing and previous 337s.

Yes, we do disagree. Not on the purpose of a C.B., but on the method of controlling alternator output. According to your prior statement you used a C.B. to regulate the maximum alternator output. That's the job of the regulator, not a C.B. Since the installation changed the basic design of the sytem referenced in the drawings, the FAA approval was invalidated. IMHO

[Kellym]

...I used a circuit breaker for the output that matched the max current for the output wire, which was about 10 amps below the rated output of the alternator, as I had no need for the extra output, and didn't want to have to upgrade the wiring all the way to the panel bus with heavier wire. It worked fine for the remaining 4 years I had the plane. FSDO signed a 337 with no problem when presented with the existence of a factory drawing and previous 337s.

Yes, we do disagree. Not on the purpose of a C.B., but on the method of controlling alternator output. According to your prior statement you used a C.B. to regulate the maximum alternator output. That's the job of the regulator, not a C.B. Since the installation changed the basic design of the sytem referenced in the drawings, the FAA approval was invalidated. IMHO

We disagree because you are mis-reading my original statement. The circuit breaker was merely the limiting/protection device, NOT the controlling device, which we agree is the regulator. The FAA approval was not solely based on the Cessna drawings, and the 337 stands on its own. The only difference from the Cessna drawings was the size of the load wire to the regulator and buss, and the size of the CB. No IA inspecting the aircraft since then has had any issue with it, to my knowledge.
A 170 has no need for the output of the smallest alternator Cessna used on the 172, unless you have added a lot of load. Part of any modification to the electrical system has to be a load analysis. Since most 170s had either 25 or 35 amp generators, they are unlikely to need a 50 amp alternator and few smaller certified ones are available. BTW, the cost was well under $500, by acquiring overhauled alternator with overhaul shop giving trade-in core credit on old generator, and only regulator and a couple CBs needed to complete the job.

[170C]

Not to distract from the subject of the thread, but other than the "legality" of the matter, is there any reason a starter, generator or alternator can not be overhauled/repaired by any local auto electric shop? I did this several times over the years I have owned vrs aircaft (25 yrs) and never had any problem with the preformance of the rebuilt units. The last time I needed work done on my alternator, I did so with a certified repair shop, but he did exactly what the auto/electric shop would have done. Now, possibly the alternator or generator could be considered flight critical, but the starter would not appear to be so since it isn't used while in flight. With this in mind is it technically illegal for me to replace old bushings, seals & brushes on my starter? If so does it make it OK if my IA signs it off?