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Alternators vs Generators

Comanche Electrical System

Last Post by William Hughes 4 years ago

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William Hughes

Joined: 5 years ago

Posts: 49

Topic starter 22/11/2020 4:10 am

Per a question from a Comanche owner: Otto

Otto:

"1) I have original generator installed - no record in log books of it ever being removed/inspected/overhauled. In process of annual and my IA recommended an overhaul/replacement - AM I better off just overhauling existing generator or possibly replacing with an Alternator? Any recommendations on vendors?

2) Exhaust stack on left side of engine needs repair for cracks ( 1 crack in front stack and 1 crack in rear stack near the where manifold bolts into cylinders) found during pressure test. What are recommendations and estimated costs for repair/replacement?"

There are plenty of items to consider when it comes to alternators vs generators:

- an alternator is lighter

- an alternator makes lots of power at low idle

- an alternator could be considered less reliable and has a bit more of a chance to fry things when it goes wrong

- generators are heavier

- generators do not charge the system at low rpm

- generators could be considered more reliable and less prone to fry things if they go wrong

- generators can make power if the battery is totally dead.

Realistically, that last issue is only relevant if you do something like hand prop the engine and are hoping to charge the battery. Or if perhaps you had a total melt-down of the battery in flight that actually disconnected it or something like that. (As a side note I have actually been in the cockpit running the throttles while a mechanic hand started a Comanche 250 with a three bladed prop and a completely dead battery. It was a tense and careful business but the battery charged - something not likely with an alternator.)

I have chosen to keep my Comanche with her generator. I have replaced the regulator with a solid state one, the landing lights with LEDs to reduce power, it has a modern and light starter, and copper welding cables for main power wiring. I am still careful not to have too many electrical things going when sitting on the ground waiting for a clearance.

This is a good article. Note the references at the bottom for vendors: ttps://www.aopa.org/training-and-safety/students/solo/special/alternators-and-generators

Otto, this is such a good topic I am going to add it to the maintenance forum.

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Alternators Generators

William Hughes

Joined: 5 years ago

Posts: 49

Topic starter 22/11/2020 4:22 am

As a follow up, if my generator ever packed it in all the way I would probably replace it with an alternator. Modern alternators are reliable, and the solid state regulation and protection is also good.

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