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Multi Engine magnetos. Which is faulty?

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Multi Engine magnetos. Which is faulty?

Old 7th Oct 2013, 00:17
  #1 (permalink)  
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Join Date: Jul 2013
Location: RU
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Multi Engine magnetos. Which is faulty?

Recently i have started to prepare myself for ME rating, so i have started to read Jeppesen ME book. After aircraft systems chapter there have being a small quiz. And i cant understand one of the questions:

While performing a magneto check on a multi-engine airplane equipped with
toggle-type switches, the engine dies when you actuate the left magneto switch on
the left engine. Which magneto is faulty?

I have answered the right on left engine, and it was right answer, but

On a multi-engine airplane equipped with paddle-type ignition switches, the engine dies when you select the left position on the left engine ignition switch.
Which magneto is faulty?

I have answered the same, but it was wrong. The correct answer was the left magneto on the left engine.

Why? I cant get it, even text book doesn't explain it.

Please, would you please explain me this answer.

Thank you guys.
levashov is offline  
Old 7th Oct 2013, 01:43
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Join Date: May 2012
Location: Sydney
Posts: 67
As a general rule, it goes as follows:

Switch:- Off Left Right Both

Off = Both mags grounded (won't supply ignition)

Left = Left magneto live and right magneto grounded (Left will supply ignition)

Right = Right Magneto live and left magneto grounded (Right will supply ignition)

Both = Both Mags live and will supply ignition.

Disclaimer: In my experience, a lot of aircraft that are older have had many wiring repairs and even new looms fitted which can lead to the switch doing the opposite to the above chart. However, the switch is supposed to be Off Left on Right on Both on.

I wouldn't be surprised if the correct answers in your exams are as confused as some of the aircraft wiring out there.

To be 100% on this, you'd need to verify it by sifting through some wiring diagrams on various ME trainers to be sure.

Cheers
Aviater is offline  
Old 7th Oct 2013, 03:35
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jxk
 
Join Date: Apr 2008
Location: Cilboldentune, Britannia
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What Aviater says is correct, however there is no way of knowing whether the mechanic has wired the mags the correct way around without testing that the grounded mag relates to the correct switch position by delving under the cowlings.
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Old 7th Oct 2013, 07:07
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Join Date: Feb 2000
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The magneto switches on the multiengine recip airplanes I have flown have either been toggle switches, or rotary switches. I have no idea what a "paddle" type switch means in this context.
A Squared is offline  
Old 7th Oct 2013, 07:20
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Join Date: Feb 2000
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Originally Posted by levashov View Post
While performing a magneto check on a multi-engine airplane equipped with
toggle-type switches, the engine dies when you actuate the left magneto switch on
the left engine. Which magneto is faulty?

I have answered the right on left engine, and it was right answer,
Makes sense, If the engine is running, then presumable both toggles switches for both magnetos are "on". If you "actuate" the left magneto switch, that presumably, means you move it to the "off" position, grounding the let magneto, leaving the right magneto on. Engine dies so right magneto must be faulty.


Originally Posted by levashov View Post

On a multi-engine airplane equipped with paddle-type ignition switches, the engine dies when you select the left position on the left engine ignition switch.
Which magneto is faulty?
Like I said, I have no idea what "paddle" switch means, but some aircrat have a rotary magneto switch, like Aviator said, these have 4 positions: off, left, right, both.

Again, you have the engines running, so presumably, the switch is on "both" you move the switch to the "left" position, this grounds the right magneto, leaving the left magneto "on" and the engine dies, so obviously the left magneto was faulty.

That's the way it would work with a rotary magneto switch.
A Squared is offline  
Old 7th Oct 2013, 07:35
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Join Date: Jul 2013
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Yes, paddle switch is a rotary switch.
I got your explanation, it really make sense. Thank you very much!
levashov is offline  
Old 7th Oct 2013, 08:47
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Join Date: May 2008
Location: Scotland
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With the toggle type switch you select the mag to 'off',with the rotary you are selecting the mag 'on'.
bcgallacher is offline  

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