O-470 Alternator Conversion

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Andrew L.
Although the generator in my C-182 doesn't seem to want to quit working like a champ, I'm considering converting to an alternator when it shows signs of going kaput. What options are out there? What's the cost to convert? Is it worth it?
 
I pitched my 180's stock alternator and installed a B&C with B&C regulator via field approval. Adios, charging issues, and I'd had a bunch. It's been perfect for 10 years. Plane Power is what most guys use because it's STCd.
 
The main disadvantage of the generator is that it won't charge while idling or taxiing. If that is not an issue for you, it's cheaper to keep her. I'm quite happy with the generator on my C-172 and will probably keep it as long as parts are available.
 
I did the Plane Power conversion several years ago & am happy to not have to worry about my electric load anymore. IIRC it was about $1200 but that was with an A&P who let me help. Saved a bunch of weight pulling the heavier generator & old wires out but the solid-state voltage regulator had to be replaced after just a couple of years when it flaked out on me - 2 years later no further trouble.
 
Thanks y'all. Glad to hear your thoughts.

I've had several friends and an A&P or two over the years telling me I should ditch the generator I dislike that the gennie doesn't really pick up until about 15-1600 RPM, but honestly, I don't fly much at night, and I only have a Nav/Comm, transponder, intercom, and Garmin 696 other than lights, so I haven't experienced any issues since I rarely have everything energized at the same time. Haven't measured the draw, but I don't think that's a whole lot of juice. I was thinking of replacing many of the bulbs with led for less power draw. I don't know, $1200-$1500 seems like a pretty penny for something marginally better. The B&C price point looks more attractive. Is it a direct bolt on? I do like that the gennie will continue to kick out 14+ volts regardless of battery condition as long as I have my foot on the gas.
 
That O-470 might have the old cushioned mount for the generator/alternator, and some of them are in really rotten condition. They can also let the belt jump off under certian vibratory conditions. To make it worse, I've sometimes found mixed parts: cushioned mount with non-cushioned adjusting arm, and vice-versa. This causes wear to the mounting system and can chew up the generator or alternator, too. So a bunch of expensive new parts can add to the conversion costs.

The ONLY advantage a generator has over an alternator is the ability to bootstrap itself and start charging a totally dead battery after hand-propping. An alternator won't do that.
 
The ONLY advantage a generator has over an alternator is the ability to bootstrap itself and start charging a totally dead battery after hand-propping. An alternator won't do that.

Are you sure about that? As Tom D. pointed out many years ago, the aircraft's master contactor needs battery voltage for it to be energized via the master switch. With a totally dead battery this will not happen. The contactor must be energized to connect the battery to the generator and allow charging. You would need to rig up a temporary jumper wire to make this work, the legality of such being questionable.
 
Are you sure about that? As Tom D. pointed out many years ago, the aircraft's master contactor needs battery voltage for it to be energized via the master switch. With a totally dead battery this will not happen. The contactor must be energized to connect the battery to the generator and allow charging. You would need to rig up a temporary jumper wire to make this work, the legality of such being questionable.
Yup, you're right.
 
B&C was a simple bolt-in replacement of my stock alternator. Small and lighter always helps. It's crowded in there.



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+1 on Planepower, make sure you do the voltage regulator too, it's relatively cheap and good insurance to change at the same time.
 
+1 on Planepower, make sure you do the voltage regulator too, it's relatively cheap and good insurance to change at the same time.
It also replaces the old overvolt sensor, and gives that option for older airplanes that didn't have it.
 
It also replaces the old overvolt sensor, and gives that option for older airplanes that didn't have it.

Why does the high-volts light illuminate when I turn the alternator off via the master switch? Cessna 182P. Shouldn’t it be high AND low?
 
I replaced the 1957 generator (C182A) with a PlanePower and regulator in 2014 - worked great until the regulator quit after 270 hrs in 2017. The replacement has been fine since then, about 100 hrs now, keeping my fingers crossed!
Other than the regulator, it's great.
 
Why does the high-volts light illuminate when I turn the alternator off via the master switch? Cessna 182P. Shouldn’t it be high AND low?

Depending on the vintage, that light was labelled "High Voltage" or "Low Voltage." The circuitry was exactly the same and the light worked in exactly the same manner. It goes like this: The ALT switch gets its voltage from the bus, and turning it on sends the signal through the overvoltage sensor to the "S" terminal of the regulator, which turns the regulator on and energizes the alternator field so it can start generating. That overvolt sensor monitors the system voltage (as sent to it by the switch) and if the voltage reaches 15 volts (30 in a 24-volt system) it shuts off that feed to the regulator, which kills the regulator and takes the alternator offline to stop the overvolt condition to avoid system damage or fire. So that silly little light is right in either case: if it comes on by itself it likely did so because the overvolt sensor detected a high system voltage and shut things off, now making the system voltage Low, as now the system is running on the battery only, around 12 volts instead of the usual 14 or thereabouts. If you turn your Master on and leave the ALT off, or, as you say, turn that ALT off, the light comes on because the regulator has been shut down just as if the overvolt regulator had shut it off.

There was a serious shortcoming with this setup. The same alternator and regulator was used in Ford cars for many years, but the regulator was switched on by a small signal from the alternator's stator terminal as the alternator started spinning, and the ALT idiot light would go out. If the alternator belt broke or the alternator failed internally, the stator voltage would fail and the regulator would shut off and the idiot light would illuminate. (That light was run off the same "I" terminal on the regulator as the high/low volt light is in the airplane.) In the airplane, though, we needed a means for the pilot to shut off the alternator if it really went rogue, so the regulator was switched on/off by the ALT switch instead of the stator signal, and if the alternator belt failed, or the alternator failed internally, or the alternator fell clean off the airplane, that light wouldn't illuminate. The regulator would still be alive and think everything is OK. Not so good, if the pilot isn't including the ammeter in his scan.

So in the later '70s Cessna started using ACUs, alternator control units, instead of the old regulators. These were electronic boxes that were a little smarter and could detect a failed alternator and signal the pilot via the light. They also contained the overvolt circuitry. The Plane Power regulator, if I recall correctly, has all that same stuff in it, making it the better bet. I last installed one about four years ago.
 
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I replaced the 1957 generator (C182A) with a PlanePower and regulator in 2014 - worked great until the regulator quit after 270 hrs in 2017. The replacement has been fine since then, about 100 hrs now, keeping my fingers crossed!
Other than the regulator, it's great.
That's the trouble with electronics. They work really, really well until they don't. I had considerable trouble with Kelly electronic regulators that were direct PMA replacements for the old electromechanical regulators that were used for decades, and had about four of them go in the fleet, one after the other. I figured it was because the students or instructors were shutting the ALT off in flight, under load, which was warned against in some airplanes. The field coil in the alternator can generate a massive voltage spike when its current is abruptly shut off and can fry sensitive electronics if their internal protection isn't good enough. Eventually the manufacturer got it right and they behaved. The electromechanical regulators were just relays and resistors and couldn't care less about voltage spikes, though the rest of the airplane's radios and stuff still did.
 
Thank you @Dan Thomas .

Mine is a 1976 182P and I believe I get the old school “alternator fall off the plane light not on” variety.
 
I replaced the 1957 generator (C182A) with a PlanePower and regulator in 2014 - worked great until the regulator quit after 270 hrs in 2017. The replacement has been fine since then, about 100 hrs now, keeping my fingers crossed!
Other than the regulator, it's great.
I had similar happen to me - VR premature mortality. IIRC the company had some problems with the earlier versions. They didn't offer to make it right but I wasn't going to complain for < $200. Been a couple years and a few hundred hours so far with no further issues.
 
Although the generator in my C-182 doesn't seem to want to quit working like a champ, I'm considering converting to an alternator when it shows signs of going kaput.

If you can remember to replace the brushes every 700 hours or so (~$15), it will probably never stop working. If by chance it does, you can get them overhauled for next to nothing as it's just an old Delco auto part. Do you still have the stock mechanical regulator? Zeftronics makes a solid-state unit (<$300) that works well. I also have a 182E, and over the years most of my electrical issues end up being due to old switches, breakers or wiring. The major parts of the system (generator, regulator, battery) that everyone suspects first are actually pretty bullet-proof.

C.
 
Be careful with the Planepower. The cheesy stamped and welded mounts are prone to cracking and the holes don't line up worth crap. I've never seen one go over a year without cracking. Don't know why there hasn't been an AD on them. Most guys around here are switching back to the Prestolite mount that kinda sorta fits the Planepower alternator, STC be damned.
 
I did plane power alternators on the 310 back when we had it. Great product. Works very well and got weight reduction from it.

But that said for your VFR day flying, I wouldn’t mess with it preemptively. I would consider it a good upgrade when the time comes, if nothing else it helps resale.
 
Be careful with the Planepower. The cheesy stamped and welded mounts are prone to cracking and the holes don't line up worth crap. I've never seen one go over a year without cracking. Don't know why there hasn't been an AD on them. Most guys around here are switching back to the Prestolite mount that kinda sorta fits the Planepower alternator, STC be damned.
That might apply to the Lycoming conversions and a few Continentals. The O-470's mount is cast as part of the left rear engine mount bracket.

I've seen the OEM Lycoming alternator mount crack at the bends. They didn't dress and smooth the cut edges before bending and heat treating, so cracks can be expected. It was one of the things I looked for during inspections.
 
That might apply to the Lycoming conversions and a few Continentals. The O-470's mount is cast as part of the left rear engine mount bracket.
I only have experience with the 470 and up Continental conversions. And they required swapping out the LR integral cast mount with a plain leg to install the stamped planepower mount.
 
I only have experience with the 470 and up Continental conversions. And they required swapping out the LR integral cast mount with a plain leg to install the stamped planepower mount.
Strange. I did one and it went right onto the existing cast mount.
 
The main disadvantage of the generator is that it won't charge while idling or taxiing. If that is not an issue for you, it's cheaper to keep her. I'm quite happy with the generator on my C-172 and will probably keep it as long as parts are available.
I PREFER a generator in an airplane because it is more rugged. A generator rectifies AC to DC with a massive commutator while an alternator uses fragile diodes. An alternator is more efficient, smaller and lighter but less reliable because diodes do not like big voltage spikes and the greater vibration of an aircraft engine. It is very cheap and easy to replace brushes every 1000 hours or so and my C-210D hardly cares about weight.
 
I PREFER a generator in an airplane because it is more rugged. A generator rectifies AC to DC with a massive commutator while an alternator uses fragile diodes. An alternator is more efficient, smaller and lighter but less reliable because diodes do not like big voltage spikes and the greater vibration of an aircraft engine. It is very cheap and easy to replace brushes every 1000 hours or so and my C-210D hardly cares about weight.
Uh... have you ever had an alternator apart? Ever maintained a fleet of airplanes with alternators and one or two with a generator? Big difference. Huge difference. That alternator is far more reliable, makes power at idle, its brushes last as long or longer and cost no more, it weighs a lot less. It produces twice the power. The regulator is simpler. Diodes rarely fail; I never came across one in all my years as a mechanic. Not one. Generators are simply long obsolete, like a Commodore 64 computer. Or a 1965 TV. So are magnetos with their points and condensers, but we're stuck with them until the FAA gets with the program. If generators are so great, why did car manufacturers drop them 55 years ago?
 
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Dan, by your argument we should all stop flying our 50 year-old airplanes and buy a new SR22. It's obsolete technology, right?

The OP was asking what make practical and economic sense. I think he's heard from several posters that the old generator still has some advantages.

The good news for you is that there ARE FAA approved solid-state replacements for your old magnetos available (SureFly and others). Have you converted your fleet yet? Or are those obsolete mags still getting the job done?

C.
 
Dan, by your argument we should all stop flying our 50 year-old airplanes and buy a new SR22. It's obsolete technology, right?

The OP was asking what make practical and economic sense. I think he's heard from several posters that the old generator still has some advantages.

The good news for you is that there ARE FAA approved solid-state replacements for your old magnetos available (SureFly and others). Have you converted your fleet yet? Or are those obsolete mags still getting the job done?

C.

I didn't imply that generators all need to be replaced. I was replying to Snowmass's assertion that the generator was better than the alternator, which it manifestly is not. I could find no advantages to having the generators whatsoever, especially in airplanes that need consistent dispatchability, reliability at night, and good output for night flying when considerable taxiing is involved. Replacing the brushes in an alternator is easy, and if the slip rings need cleaning up it's much easier than cleaning a generator commutator and scraping the insulation down between the segments. Leaving the insulation level eventually causes output loss. Besides that, these things are all getting very old and once a commutator is shot, that's pretty much the end of the line.

Replacing a 50-year-old airplane with a Cirrus doesn't gain much other than a young airframe and huge loan payment and higher insurance costs. It's still full of much the same technology as any old airplane, aside from the electronics.

To me, then, keeping a generator and spending money on it is almost as bad as keeping the vacuum-tube NavCom that came with your 1959 Cessna 172 and spending money keeping it going.

I'm retired and left the fleet work 8 years ago. If there had been a reliable e-Mag and I was still there I'd have certainly considered it. The maintenance time savings alone would have been worthwhile. The reviews on those things at the time were not good, certainly not good enough to consider replacing the mags with them. Things have changed in 8 years. I did install LED landing lights in everything, even back then, long before most people were willing to spring for them. They saved me a lot of hassle replacing incandescent bulbs every few days, and they were ready to go to work at night every time. They used so little current that the light switches never got hot like they could with the incandescents. Saved the switches.

Three years before I left we bought a 172SP with the Garmin G1000. Loved it. It was nice flying it, but not having to fool with the usual gyro hassles was nice too.

I'm not a dinosaur. I was a mechanic, flight instructor and owner of a homebuilt. I can see the cost effectiveness of newer technology and the pitfalls of sticking with old stuff no matter what. There are better ways to do things, and aviation has been a long time catching up. There are still too many archaic items, even on new airplanes, like felt wheel grease seals, something the automakers abandoned 100 years ago. We haven't even gotten to leather seals yet. Cleveland finally came out with nitrile nosewheel seals, but the mains are still made of felt. They get filthy and let water in. Still using Buna O-rings in hydraulic oleos, when there have been many newer compounds available for a long time that don't harden and shrink in very cold weather and split and let the oil and gas out. And we're still using bias-ply tires. With tubes, yet. And most never get any balancing of any sort, leading to wheel hop and nosewheel shimmy. In such cases, brand-new airplanes are no better than 50-year-old airplanes.
 
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Dan, why don't you actually pay attention to what I wrote and not what you imagined I wrote. I stated all the things you love about alternators but I love reliability more. The key factor is that diodes are far more fragile than a massive commutator at rectifying current. I have had alternator failures but not generator failures as long as brushes and bearings are changed at 1000 hours or so which is a very cheap and simple thing to do. Want me to show you how? I have no need for charging at low RPM or lighter weight but I do not want to lose charging due to diode failure. Also alternators are more subject to belt slippage or failure as the the high power output at low RPM means much higher belt loading.

Sayonara
 
Dan, why don't you actually pay attention to what I wrote and not what you imagined I wrote. I stated all the things you love about alternators but I love reliability more. The key factor is that diodes are far more fragile than a massive commutator at rectifying current. I have had alternator failures but not generator failures as long as brushes and bearings are changed at 1000 hours or so which is a very cheap and simple thing to do. Want me to show you how? I have no need for charging at low RPM or lighter weight but I do not want to lose charging due to diode failure. Also alternators are more subject to belt slippage or failure as the the high power output at low RPM means much higher belt loading.

Sayonara

DId you read what I said about diodes? Are you sure your alternator failures were diodes and not the usual worn-out brushes? As I said, I did not run into one single failed diode in all my years as a mechanic. Not one. It's a bogus criticism of alternators.

Your "massive commutator" is one of the reasons your alternator is limited to 35 amps or whatever. Too much current through it heats it up and those commutator segments melt through the insulation and are thrown out. So the generator regulator has to have a current limiting relay, something the alternator doesn't need.

There is a torque-slip specification to use when tensioning alternator belts. If one applies it, the belt never slips and it's never too tight. Furthermore, if the alternator was producing its full 60 amps at 14 volts at idle (which is never the case, since gear isn't being retracted or extended), it's absorbing 1.126 horsepower, hardly a slipping load. (80 amps times 14 volts is 840 watts; divide that by 746 watts per HP and get 1.126 HP.)

I built an inboard boat and installed a marinized Chev 283 that I overhauled. I ditched the generator and installed an alternator. I restored a 1949 Farmall Cub tractor, and ditched its generator and installed an alternator. I restored a 1951 International pickup, installing a Ford 300. Ditched the generator and installed an alternator. Not one of those ever gave me any trouble over many years. And as I said. as the director of maintenance for a flight school fleet, I had alternators off the airplanes every 500 hours to inspect the brushes, and running at as much as 3500 hours for the fleet per year, that happened as many as seven times per year. Some of those alternators were passed from engine to engine as the engines hit TBO, and had many thousands of hours on them, never having a single diode failure.
 
When some folks think of diodes, this is what they visualize:

serveimage


In the alternator, the diodes are massive-case things fused into two steel plates:

serveimage


Those round discs in the plates are the diode case bottoms. They're not fragile. They're big. They have to be, to handle 60 amps or 70 amps or whatever. Modern diodes have low forward resistance so they don't generate all that much resistive heat. In fact, you can bypass the regulator, feeding the field directly off the battery, and disconnect the alternator output from the battery, and by modulating the RPM you can get 120 volts DC at up to 60 amps, and that alternator will take it. This was an old trick used by a small kit you could buy in the '70s to generate power for incandescent lights or power tools that used series-wound motors, stuff that runs happily on DC. I bought one and used it on one of my vehicles. SOme huys said they could actually weld light metals with it. I didn't try that. Didn't hurt the alternator at all other than probably wearing the brushes a bit faster due to the heavy field loading.
 
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