Magneto lesson?

[lowery21]

Anybody have any advice on how to teach students about the Magnetos and how they work? There is not really any information in the POH.

 

[TonyC]

Anybody have any advice on how to teach students about the Magnetos and how they work? There is not really any information in the POH.

How 'bout:

How stuff works...​

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[nosehair]

That link is a very good explaination of the inner workings of a magneto, however it can still be confusing to the simple minded no mechanical experienced mind.

Start with a very basic concept of the magnet. That's where the magic is. The magnet. You can take a magnet and wrap (or coil) a wire around the magnet, and move the magnet back and forth within the coiled wire, and the magnetic field will excite the electrons within the wire and cause (or create) electricity! Wow!

 

[Kream926]

aircraft systems for pilots explains them well

 

[rumpletumbler]

the magnetic field will excite the electrons within the wire

ohhhhhhhh yessssssssssssssssss!

 

[darkvw]

hook one up and have them hold the output lead, that will give them an idea of it (lol), it's basicallty an engine driven generator with an interupter to provide spark. My dad taught me to get up at the first saying with one from a model t and Litz wire around my toes when i was younger and liked to stay out all night. I did n't have to be asked twice after that.

 

[labbats]

Turn the prop with all fuel double checked off and chocks on. Have them listen to the magnetos pop as the blade turns. Feel the blade tighten up before it clicks. Explain how this makes electricity and allows the plane to run without a battery.

 

[A Squared]

Feel the blade tighten up before it clicks.

THat's not he magneto making the blade "tighten up" thats the compression in the cylinders. THe force of winding the impulse coupling spring is very small comparatively when you're turning the prop. You'll feel this same "tightening up" if you turn the prop on an airplane with a shower of sparks magneto instead of an impulse coupling. Also if you take the all the spark plugs out, you don't feel the "tightening up" as you turn the prop

 

[F16fixer]

compare it to a car

I always compare it to a car. You can unhook the battery of a car and it will shut off. Turn off the master and the plane will keep running. I use this when teaching in terms of safety. Two of them means redundancy. Tell them about the two sets of plugs and how each mag runs one set. Hope this helps a little.

 

[lowery21]

Thanks guys...appreciate it.



I guess that is the main thing that I wanted to get across. That the reason for mags...besides a better regulated charge...is that mags separate the engine from the electrical system. Read: losing electricity doesn't mean you lose the engines.



I will also stress the importance of the grounding wire and what happens if it is not there or comes loose.

 

[Geronimo4497]

"Hello Children, today we are going to discuss the wonders of FEDEC! The most important part of this whole system is the battery......."

Faraday rules! Long live the Bendix! (Slicks sux)

 

[Dr Pokenhiemer]

Teach the student how to fly, how to do ao mag check, how to correct a rough running mag, and don't try to teach them how to be a mechanic!!! Teach them well, but don't waste their time and money teaching them something they don't need to know. Simply explain that the mags provide electrical power to the engine after it is started, much like an altenator in a car. We have 2 of them in case one goes out. That way, if the altenator fails, the engine continues to run. Watch a NASCAR race. When a driver switches ingition boxes, that's the same as switching magnetos--just both of ours are working at all times. End of lesson.

 

[TonyC]

I always compare it to a car. You can unhook the battery of a car and it will shut off.

Oh, really? I can unhook the battery, take it in the house, and put it in my closet, and the engine keeps running. The only thing the battery in the car is needed for is starting the thing.


If I unhook the battery in the car and it shuts off, I've got an alternator problem.


I'm with Dr Pokenhiemer here. They don't need to be mechanics. The mag produces electricity for ignition as it turns. Works good, lasts long time. 'Nuf said.



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[lowery21]

Yeah...but I've got my CFI initial coming up. Gotsta know to small stuff too.

Thanks again for all the help.

 

[TrafficInSight]

It goes spinny and makes sparky

 

[troy]

Remember, a lawnmower has mags (most everyone has operated a mower). No battery needed to continue running, just for starting. Also, the student does need to know how it works in order to better understand emergency procedures, etc. Five minutes on a mag lesson is worth it.

Quote: "We have 2 of them in case one goes out. That way, if the altenator fails, the engine continues to run" This is false, the mags and the charging circut are not connected together in any way.

 

[nosehair]

don't try to teach them how to be a mechanic!!! Teach them well, but don't waste their time and money teaching them something they don't need to know.

Nope, Dr. Pokey, can't let you spread this swill. There is much more to learning to fly than wigglin' the stick 'n passin' the checkride. If you don't care to know how the mags work - that's your business, but I, and some people, need to know this simple spark generating system to understand why the engine runs without the battery. You are right that it really can't make any difference about being able to fly the airplane, but in order to be the master of the machine, I think that a basic knowledge of how things work gives me power over the machine. Instructors should be able to explain simple mechanical concepts.

 

[Dr Pokenhiemer]

What I meant was--New students have so much information to learn, it's like drinking from a fire hose. Don't add more to it than what they can handle. I instructed for 2 years-fulltime. Some students try to make a mountain out of a molehill on some things and make it harder than it has to be. Keep it simple for them, but challenge them at the same time.

 

[nosehair]

What I meant was--New students have so much information to learn, it's like drinking from a fire hose. Don't add more to it than what they can handle. I instructed for 2 years-fulltime. Some students try to make a mountain out of a molehill on some things and make it harder than it has to be. Keep it simple for them, but challenge them at the same time.

Riiight! That is exactly true - and my little simplified explaination of how the mag makes a spark is about all I usually say about it, unless the student wants more.
You are right about some students and some instructors trying to do too much too soon.

 

[F16fixer]

O.K. thanks for corecting me on that statement! What I ment to add was that many newer vehicles have an electric fuel pump that is only run by the BATTERY. And if you unhook the battery it will shut off. Yes I have done this and that is what happens. (It has nothing to do with the alternator), but when it comes to airplanes you either have gravity fed tanks on your 152 or you have an engine driven fuel pump, so there is no reliance on a battery. This will keep the airplane running.
So why don't you go out in your drive way and unhook the battery from your CRX and see if it keeps running. If the fuel pump is directly hooked to the battery, I bet you can guess what will happen.

Oh, really? I can unhook the battery, take it in the house, and put it in my closet, and the engine keeps running. The only thing the battery in the car is needed for is starting the thing.


If I unhook the battery in the car and it shuts off, I've got an alternator problem.


I'm with Dr Pokenhiemer here. They don't need to be mechanics. The mag produces electricity for ignition as it turns. Works good, lasts long time. 'Nuf said.



.

 

[TonyC]

So why don't you go out in your drive way and unhook the battery from your CRX and see if it keeps running.

Well, for starters, I don't have a CRX in my driveway. I've never seen a component that was attached directly to a car battery which would not also be connected to the car's electrical system, powered by the alternator, were the battery cable to be disconnected from the battery. Fuel pumps are powered by alternators, too. But, I'm not an expert, and I haven't seen them all, so there could be such a system.


Nevertheless, the point of the magneto discussion is not related to fuel delivery. The point is the magneto is an independent electrical system. As long as the engine is turning, the magnetos will provide a spark.







.

 

[Stifler's Mom]

Site

Interesting website.

 

[USMCmech]

Quote: "We have 2 of them in case one goes out. That way, if the altenator fails, the engine continues to run" This is false, the mags and the charging circut are not connected together in any way.

One other thing,

Airplane engines do not need two magnetos. Some only have one, with dual distributors.

Airplane engines DO need two sparkplugs. Since the cylinder of a airplane engine is so huge the dual sparkplugs allow more complete combustion of the fuel. Combustion starts at both sides and meets in the middle. Think about it, an O-360 each cylinder has 1.5 liters of displacement in each jug. That's a lot of fuel to burn in just 12 degrees of crank rotation.


Having the second mag is just backup. Since you already have to use the dual distributors, wires, ect, why not go ahead and use an extra mag.

 

[Geronimo4497]

Having the second mag is just backup. Since you already have to use the dual distributors, wires, ect, why not go ahead and use an extra mag.

I hope that you are not bad mouthing the beautiful Bendix D-3000 dual magneto?! We won WWII with the dual mag (i.e. 1 common shaft with two "distrubutors") that was on the likes of the Corsair, P47, P51, B24/25 etc. etc. etc.

No doubt that it is more complicated than a Slick mag, however, I would argue that this magneto has recieved too much critizime for being a "piece of junk", not that I am accusing anything......

This particular style of mag is far too often the victim of "tinker-itis". Some specialized knowlege is needed to work on and service this device. I would argue that if one takes the time (no more than one weekend) to sit down with the service manual and an example of this very well enginereed magneto that vast knowlegdge can be obtained. So much, in fact, that all of your friends at the local airport will come by your hangar on the weekend and annoy you with questions about proper mag timing!!!!

I do not have an airplane that has this mag installed, but have been fortunate enough to work on several airplanes with this type of mag (172N, 182RG).

If you have the burning desire to 'know all there is to know' about basic a/c engine systems, checkout http://www.avweb.com/sponsors/skyranch/index.htm.

I'm not affiliated with skyranch, just impressed by the info that has been compilied on the CD.

Off to go admire my Bendix S-200 starting vibrator mags now........


By the way, throw away any Slick mag you see, I would be very greatful!

 

[Balou]

It goes spinny and makes sparky

Laughed my a** off, mind if I use that one in the future ?

 

[TrafficInSight]

Laughed my a** off, mind if I use that one in the future ?

not at all