Why 2 mags for each engine ?

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Styggron
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Why 2 mags for each engine ?

Post by Styggron »

Hello,

Question re the Avro Anson. There are 2 engines but why are there 4 mag switches ?

Each engine has 2 mags trying to understand
a) why
b) what each do specifically

Thanks in advance
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Shadow95
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Re: Why 2 mags for each engine ?

Post by Shadow95 »

This may help you understand what the magnetoes do.

http://www.qualityaircraftaccessories.c ... ft_magneto

Happy Flying,

Mike
Shadow95

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DHenriques_
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Re: Why 2 mags for each engine ?

Post by DHenriques_ »

Styggron wrote:Hello,

Question re the Avro Anson. There are 2 engines but why are there 4 mag switches ?

Each engine has 2 mags trying to understand
a) why
b) what each do specifically

Thanks in advance


Magnetos are the best solution to solve the ignition issues involved with most piston aircraft engines. The two main reasons for them are redundancy and to provide ignition to the engine completely separated from the aircraft's main electrical system. That way if the electrical system fails, the mags still supply ignition to the cylinders and the engine continues to operate.
Two plugs per cylinder..........one mag fires the #1 plug the other mag fires the #2 plug.
Works like a charm!
Dudley Henriques

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Styggron
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Re: Why 2 mags for each engine ?

Post by Styggron »

DHenriquesA2A wrote:
Styggron wrote:Hello,

Question re the Avro Anson. There are 2 engines but why are there 4 mag switches ?

Each engine has 2 mags trying to understand
a) why
b) what each do specifically

Thanks in advance


Magnetos are the best solution to solve the ignition issues involved with most piston aircraft engines. The two main reasons for them are redundancy and to provide ignition to the engine completely separated from the aircraft's main electrical system. That way if the electrical system fails, the mags still supply ignition to the cylinders and the engine continues to operate.
Two plugs per cylinder..........one mag fires the #1 plug the other mag fires the #2 plug.
Works like a charm!
Dudley Henriques
Thank you Dudley however if this is the logic why don't other aircraft also have it like the B377 ? They only have 1 mag per engine and this Avro has 2.
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Jacques
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Re: Why 2 mags for each engine ?

Post by Jacques »

Styggron,

Only one magneto switch per engine, but still two magnetos. Remember your checks for the magnetos pre flight- you are checking the left magneto, the right magneto and then switching back to both magnetos.

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Styggron
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Re: Why 2 mags for each engine ?

Post by Styggron »

Jacques wrote:Styggron,

Only one magneto switch per engine, but still two magnetos. Remember your checks for the magnetos pre flight- you are checking the left magneto, the right magneto and then switching back to both magnetos.
Jacques,
The Avro Anson has 4 switches.
2 for the left
2 for the right

hence my question.
From what Dudley says, the switches are for each plug. Each magneto has 2 plugs, therefore 4 switches. :)
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Nick - A2A
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Re: Why 2 mags for each engine ?

Post by Nick - A2A »

Styggron wrote:[...] why don't other aircraft also have it like the B377 ? They only have 1 mag per engine [...]
Actually, it seems those 28 cylinder R-4360 Wasp Majors on the KC/C-97 (and presumably the Strat too) had up to seven magnetos per engine according to this chap. :)
JetStar wrote:Another difference from this engine and other radial engines was that the magnetos were mounted on the sides of the front nose section, early models had 7 magnetos firing 8 sparkplugs, there were 56 sparkplugs per engine, later models had 4 magnetos firing 14 sparkplugs.
Not sure about the switching arrangement for that lot. After all, this was about as complex as piston aircraft engines got.

Nick
A2A Simulations Inc.

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Jacques
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Re: Why 2 mags for each engine ?

Post by Jacques »

No room left in the cockpit for twenty-eight individual magneto switches! :D

I don't know Styggron. I could guess that four switches labeled "left" "right" and "both" simplifies and streamlines the checking process, but I wasn't involved in the design and I haven't read anything about "why" they configured the magneto switches as they did.

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Styggron
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Re: Why 2 mags for each engine ?

Post by Styggron »

Jacques wrote:No room left in the cockpit for twenty-eight individual magneto switches! :D

I don't know Styggron. I could guess that four switches labeled "left" "right" and "both" simplifies and streamlines the checking process, but I wasn't involved in the design and I haven't read anything about "why" they configured the magneto switches as they did.
That's ok, at least we know why there are 4 as Dudley explained. :)
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Piper_EEWL
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Re: Why 2 mags for each engine ?

Post by Piper_EEWL »

I don't have the Avro Anson but I'm guessing it has the same setup as the Spitfire. It has two seperate magneto switches for the two magnetos that fire the one engine up front. In later aircraft they moved the magneto switch into one unit as Jacques explained above. Hence the 4 switch positions. Off, L, R, Both. Off meaning the obvious off. L meaning the left magneto only. R the right magneto only and Both meaning both magnetos at the same time. It's the same on the Stratocruiser than on the Cessna 172 (as for the switches). The difference being that the Strat has four switches for four engines and the 172 has one switch for one engine. They still have two (or more) magnetos per engine. Only the switch has been modified to switch both magnetos. I'm also guessing this has something to do with streamlining the cockpit.
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Styggron
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Re: Why 2 mags for each engine ?

Post by Styggron »

Piper_EEWL wrote:I don't have the Avro Anson but I'm guessing it has the same setup as the Spitfire. It has two seperate magneto switches for the two magnetos that fire the one engine up front. In later aircraft they moved the magneto switch into one unit as Jacques explained above. Hence the 4 switch positions. Off, L, R, Both. Off meaning the obvious off. L meaning the left magneto only. R the right magneto only and Both meaning both magnetos at the same time. It's the same on the Stratocruiser than on the Cessna 172 (as for the switches). The difference being that the Strat has four switches for four engines and the 172 has one switch for one engine. They still have two (or more) magnetos per engine. Only the switch has been modified to switch both magnetos. I'm also guessing this has something to do with streamlining the cockpit.
Hello Piper,
The switches are not off,L,R,Both,OFF
They are specific and labelled.

2 are for the left only this one only affects engine 1
2 are for the right only when you try those, it only affects engine 2 for example.

You can't see the detail on the manual though.
I'll have a look close up and say what they are labelled as.
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Piper_EEWL
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Re: Why 2 mags for each engine ?

Post by Piper_EEWL »

Well that's my point. You'll have two switches for the left engine (left and right magneto for engine 1) and two switches for the right engine (left and right magneto for engine2). Same as the Stratocruiser but with seperate switches.

If both switches for one engine are in the on position it's equal to the both position of the combined magneto switch.
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Styggron
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Re: Why 2 mags for each engine ?

Post by Styggron »

Piper_EEWL wrote:Well that's my point. You'll have two switches for the left engine (left and right magneto for engine 1) and two switches for the right engine (left and right magneto for engine2). Same as the Stratocruiser but with seperate switches.

If both switches for one engine are in the on position it's equal to the both position of the combined magneto switch.
Because each engine has 2 sparks therefore 2 magnetos right ?

If each engine has 2 magnetos, is there a situation where you would need to turn one of the two magnetos off ?
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Piper_EEWL
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Re: Why 2 mags for each engine ?

Post by Piper_EEWL »

Exactly. Two redundant ignition circuits per engine. So if one fails the engine doesn't fail.

I guess you would turn one of the magnetos of of it has failed or if the ignition timing is off.
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bmbrzmn101
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Re: Why 2 mags for each engine ?

Post by bmbrzmn101 »

Piper_EEWL wrote:Exactly. Two redundant ignition circuits per engine. So if one fails the engine doesn't fail.

I guess you would turn one of the magnetos of of it has failed or if the ignition timing is off.
The simple answer is if the engine is running rough in flight and the pilot determines a mag may be suspect he can switch the mags from both to lt or rt. If it smooths out for instance on the rt mag, he has determined a source of the problem is related to the left mag running on that engine and can continue to run on the single mag until until he can let down to the nearest airport or the nearest airport with a maintenance facility. Actually had the occur in flight in a C45 EN ROUTE to an airshow. Was a loose p lead. Tightened her back up and flew away. Hope this helps.

Cheers, Chris
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