The plane I will soon be purchasing has an generator, working fine, but wanted to know the advantages of switching out the generator for a new alternator. I've heard good things about the Plane Power conversion kit. But to tell you the truth, I'm not real clear on what the advantages are, I know there is a weight savings, other then that what are the advantages of switching to an alternator, and is it worth switching out a perfectly good generator or is this something most people do when the generator goes?

If it's working now, and you will be VFR all or most of the time, don't spend the money to replace it until it fails. It may very well last several hundred hours. When it does quit replace it with an alternator, unless you are broke at the time and can get a generator rebuild a lot cheaper than an alternator conversion. Just my $.02 worth on the subject.

Nothing wrong with running a generator. I would just fly with it for awhile.You can always upgrade later. Pretty good info here:
http://www.rowand.net/Shop/Tech/AlternatorGeneratorTheory.htm

All good advice.
1. The generator is heavier for how many amps you get. You will maybe have a 20-30 amp generator that weighs more then twice what a 60 amp plane power alternator will.
2. The available amperage is less of an issue now days with radios that draw less power and LED lights, but if you have a big IFR stack of king radios, big landing lights, old rotating beacons you might be exceeding the available load of that generator. My 182 has a generator and with one radio, both landing lights, old beacon and nav lights im pulling 20amps on a 30 amp generator.
3. Most of the time generators go a very very long time where alternators usually dont make it to TBO.
4. Even with a dead battery your generator will produce voltage. IE if you have a dead battery, hand prop your plane, you can still fly home to your towered field with all your electronics working. If you had an alternator and you get your plane hand propped, your still going to have no power.
5. Generators have a coming in speed. You will be running on battery power alone until you get your RPM up around 1500-2000RPM. This can be an issue if you fly at night allot and have long ground hold times. Alternator produces much more power at lower idle speeds.

The single biggest advantage of an alternator is that it puts out a whole lot more power at slower rpm, which can be pretty important if a night time taxi is very long after a lengthy low power approach. A generator puts out very little power at idle. In addition to landing lights, one of the other major power draws comes from a heated pitot. For instance, I can recall years ago, taxiing in at old Denver Stapleton to Combs-Gates in our Skylane, and having the radios go silent because the lengthy approach with the pitot heat and landing/taxi lights on plus the long taxi with the landing/taxi lights on had run the battery down below what the radios needed to operate. An alternator at idle rpm will put out good charging power.

When I bought my 63 P172D 10 1/2 years ago, I threw a rod in only 15 flight hours and landed in a field. While it was in for the new engine, I had an alternator conversion done (there were several possibilities--Plane Power didn't exist yet). So I have a 65 amp alternator, which is totally capable of covering all of my airplane's power needs plus charge the battery. I have a full IFR panel (steam gauge), heated pitot and heated AOA probe, HID landing/taxi lights, wingtip strobes, and a tail strobe, plus the normal navigation lights. The HID lights draw less power than standard incandescent lights and the tail strobe draws less power than the former rotating beacon did, but the alternator could handle it if I had stock lights.

In addition to being able to handle all of the power needs while taxiing or in flight, an alternator will recharge the battery after starting in cold weather, much more quickly.

None of that answers whether you should replace your generator right away. But if I were to buy another old airplane, I'd make it a priority, based on my personal experience. When my IA and I first discussed the alternator conversion, it was an easy decision to make. My only question was "how much?" Because he also changed out the fuse panel and replaced it with a custom circuit breaker panel and did some other electrical changes, the total came to about $1500--totally worth it. A straight conversion without other changes should be less.

Cary

Max Torque wrote:Nothing wrong with running a generator. I would just fly with it for awhile.You can always upgrade later. Pretty good info here:
http://www.rowand.net/Shop/Tech/AlternatorGeneratorTheory.htm

Great link, just what I needed. And thanks for the additional comments by everyone. I'm not IFR, and don't do much night flying and I plan on switching all the lights to LED, so sounds like I can keep running the generator till it gives out and go for the alternator conversion at that time. Thanks everyone.

Careful on the hand prop idea.
Some planes I have flown had what is called a shower of sparks ignition.
My experience is that they do not work with a DEAD battery. So if no impulse starter you are dead in the water until you get it charged.

Have flown a couple old 180s set up that way.
When I bought my 170 that damned little red box was the first to go while the engine was being overhauled.
Had an impulse mag put on the left side.

Chris C

my Maule goes in to my Mechanic tomorrow to find out this very problem... Noticed the other day on a flight the guage wasn't in the pos range... it was in the discharge side the whole flight. and on restart after a fuel stop battery seemed a bit sluggish turning over the prop....returned home and will check out the engine driven Generator tomorrow.... haven't decided whether to go alternator or just overhaul the gen at a way cheaper price....I don't mind spending money on the plane and I have spent a bunch on improvements in the past but there's nothing wrong with a Generator vs an alternator... been using a generator since it was born in 1966 so after we trouble shoot to find out the actual problem I'll wait on any decision.. after all it could be a regulator or a dead cell in the battery.....will keep you posted....as to decision and costs....

I find it imteresting that originally a lof of the classics (C140, C170, etc) came with a 15 or 25 amp generator. Although our modern avionics and lighting draws less current most have been replaced with 50-60amp alternators. Seems to me that a small, light 25 or 30 amp alternator would be adequate for most of us. I know it would for me.

hotrod150 wrote:I find it imteresting that originally a lof of the classics (C140, C170, etc) came with a 15 or 25 amp generator. Although our modern avionics and lighting draws less current most have been replaced with 50-60amp alternators. Seems to me that a small, light 25 or 30 amp alternator would be adequate for most of us. I know it would for me.

On the other hand, why should anyone make or buy one, when one with double the power costs about the same and weighs about the same?

Cary

Look at the baby B&C models, esp the one that bolts onto a vacuum-pump drive on a Lycoming. Much smaller & lighter than the Interav alternator (50 amp?) on my 320. Keeping an airplane light is a game of ounces, which add up into pounds.

But, it's sure nice when out in the boonies, when some knucklehead leaves YOUR master switch on, to be able to flip a prop and start making electricity again. Not that I'VE ever done that....

If I flew IFR other than a quick pop-up out of, or descent into a small airport now and then, and had a huge electrical load to worry about, I'd swap out my generator. But for playing out in the dirt, with one Comm and a GPS to feed, and the ability to generate with a dead battery if the need arises, I'll keep what I got.

Gump

so I said I'd keep you posted....sent generator to rebuild shop... brushes were worn... bearings were almost worn out completely, shaft is out of round.... they can't do the overhaul so we are sending it out to someone who can do it all....total cost will be about 350...should take about a week... will update then...still cheaper than converting to alternator...