HiCould somebody please explain how magnetos work? From what I understand, they work like electromagnets...Also, why do magnetos have settings like "off", "both", "left", "right", "start", etc.? Is this to manage current flow?

HiCould somebody please explain how magnetos work? From what I understand, they work like electromagnets...Also, why do magnetos have settings like "off", "both", "left", "right", "start", etc.? Is this to manage current flow?

All aircraft have two magnetos per engine, so magneto positions are off, left, right and both. The start you mention powers the relay that energizes the engine crank motor and is added to the magneto switch only in smaller aircraft (for convenience).A magneto is in essence a dynamo. You can read more about magnetos here.Cheers,- jahman.

The reason why there are two Magnetos is rudundancy. If one of the sets go down the other one will still keep you flying.In run-up checks you cycle through the magnetos, Both - Left - Both - Right - Both to check for a small RPM drop. This is why there are switches for Left Right Both so you can check them pre-flight.

Redundancy has been mentioned, but not how it's redundant.There are two spark plugs per cylinder on aircraft reciprocating engines in general. That means two magnetos per cylinder. Left (left magneto) Right (right magneto) Off (Grounded, no ignition from the magnetos) Start (usually goes to the left magneto for ignition and puts a charge to the starter solenoid to spin the prop). If you have 6 cylinders, there are 12 spark plugs total and 2 magnetos. That's 6 spark plugs per magneto. You following me?All of this is typed assuming you know engine basics. ie. the spark plugs purpose in ignition and what not. Magneto operation is independent of electrical systems. They provide their own current for ignition by spinning like (you said it) an electromagnet with a certain frequency of discharges based on engine speed.

"...spinning like (you said it) an electromagnet..."Hate to be pedantic, but isn't the essential feature of a magneto that it uses a permanent magnet (to induce an EMF in a coil)? :(

I'm no electrical engineer. :( It is a permanent magnetic, an electric generator if you will. But if the OP pictures it that way and it helps the big picture, we've succeeded!

The reason why there are two Magnetos is rudundancy. If one of the sets go down the other one will still keep you flying....

It's not all redundancy: Two magnetos with two separate sparks plugs set up symmetrical flame fronts inside the cylinder after mixture ignition, thus reducing the onset of detonation and allowing a higher manifold pressure setting and correspnding higher BHP output during take-off, and a leaner, more fuel efficient mixture during cruise for added range.Cheers,- jahman. Director, Department of Redundancy Department.

It's not all redundancy: Two magnetos with two separate sparks plugs set up symmetrical flame fronts inside the cylinder after mixture ignition, thus reducing the onset of detonation and allowing a higher manifold pressure setting and correspnding higher BHP output during take-off, and a leaner, more fuel efficient mixture during cruise for added range.Cheers,- jahman. Director, Department of Redundancy Department.

Right. Redundant everything. Including ignition... Redundancy. This thread is getting too pedantic and the meaning is being lost.

Right. Redundant everything. Including ignition... Redundancy. This thread is getting too pedantic and the meaning is being lost.

Not really: Redundancy means "a duplication of components or circuits to provide survival of the total system in case of failure of single components". With piston aircraft redundancy means that at a given RPM you would get exactly the same BHP with the Left, Right or Both magnetos, which is not the case (because you get more with Both).For example, at the limit, there might be a runway that given current conditions you could take-off from with Both magnetos but not with only one, or an island atoll (note the redundancy!) that would be in-range for both magnetos but out of range in case one of the magnetos failed. In both these cases the double magneto arrangment is not redundant. And you could keep going with even more examples: Maximum ceiling (another redundancy!), maximum climb rate (impportant for take-off obstacle clearing), maximum take-off weight, etc.Actually all the performance charts in the Pilot's Operating Handbook for the aircraft will be wrong for single magneto operation.Cheers,- jahman.

Take a look at an old, Briggs & Stratton type lawn-mower engine..There's a magnet imbedded in the flywheel, that passes by a fixed coil.. from that coil there's a wire to the spark plug. That's a crude magneto..

..Oh.. and besides redundancy (two of them), it's a matter of simple reliability.You can have a complete, electrical failure.. have the battery fall out of the airplane, and the alternator belt snap, and a magneto ignition system will keep humming along..

Not really: Redundancy means "a duplication of components or circuits to provide survival of the total system in case of failure of single components". With piston aircraft redundancy means that at a given RPM you would get exactly the same BHP with the Left, Right or Both magnetos, which is not the case (because you get more with Both).For example, at the limit, there might be a runway that given current conditions you could take-off from with Both magnetos but not with only one, or an island atoll (note the redundancy!) that would be in-range for both magnetos but out of range in case one of the magnetos failed. In both these cases the double magneto arrangment is not redundant. And you could keep going with even more examples: Maximum ceiling (another redundancy!), maximum climb rate (impportant for take-off obstacle clearing), maximum take-off weight, etc.Actually all the performance charts in the Pilot's Operating Handbook for the aircraft will be wrong for single magneto operation.Cheers,- jahman.

In engineering, redundancy means duplicating critical components of a system to increase its reliability and hence safety. It's to ensure that a single failure cannot on its own create an unacceptable risk. Pre-take off checks include switching to left and right magnetos and checking that the rpm drop is within acceptable limits. If it is isn't you don't take off. Can you givwe me an example of a take off chart for a piston engined aircraft that distinguishwes between one and tow magnetos?It's you who is wrong - not the POHs. As was said years ago a little leaning is a dangerous thing.

Hi.I was wondering until I reached part of the way down this thread why a cylinder would need 2 plugs (I only know about cars and electronics) but reading about the flame fronts and smoothing the ignition (I mean of the mixture, not the wiring) makes sense and explains (less power) why you get a drop in RPM when you test the magnetos by switching to L or R instead of Both. That implies why you shouldn't fly if you don't get a drop.Cheers,D

Hi.I was wondering until I reached part of the way down this thread why a cylinder would need 2 plugs (I only know about cars and electronics) but reading about the flame fronts and smoothing the ignition (I mean of the mixture, not the wiring) makes sense and explains (less power) why you get a drop in RPM when you test the magnetos by switching to L or R instead of Both. That implies why you shouldn't fly if you don't get a drop.Cheers,D

The absence of a drop in rpm should be treated with suspicion because it could arise from faulty grounding or or an incorrectly timed magneto.

Not really: Redundancy means "a duplication of components or circuits to provide survival of the total system in case of failure of single components". With piston aircraft redundancy means that at a given RPM you would get exactly the same BHP with the Left, Right or Both magnetos, which is not the case (because you get more with Both).For example, at the limit, there might be a runway that given current conditions you could take-off from with Both magnetos but not with only one, or an island atoll (note the redundancy!) that would be in-range for both magnetos but out of range in case one of the magnetos failed. In both these cases the double magneto arrangment is not redundant. And you could keep going with even more examples: Maximum ceiling (another redundancy!), maximum climb rate (impportant for take-off obstacle clearing), maximum take-off weight, etc.Actually all the performance charts in the Pilot's Operating Handbook for the aircraft will be wrong for single magneto operation.- jahman.

That's exactly what the magneto system is ["a duplication of components or circuits to provide survival of the total system in case of failure of single components"]... Yes engine performance would be compromised, but have you ever flown at night or in the soup with one mag? One magneto operating will get you to the runway if the other fails. That's pretty damn redundant! I'm really not understanding why this could possibly be an argument. Go to your local flight school and argue semantics with them over the word redundancy and you'll be over your head in no time! :( I do agree that the primary purpose was probably to allow even fuel combustion, but it's now commonly excepted as a fail safe, too.

The absence of a drop in rpm should be treated with suspicion because it could arise from faulty grounding or or an incorrectly timed magneto.

Yes. I'd be more inclined to fly if I had no drop in RPM as opposed to too much drop/rough rpm.