Flight Training - December 2019 - 17

HOW IT WORKS

BY JULIE SUMMERS WALKER

MAGNETO

THE SOURCE OF THE SPARK

FARADAY'S LAW:

TECHNOLOGICALLY SPEAKING, ONE OF THE OLDEST COM-

ponents on general aviation aircraft is the magneto,
a technology that is more than 100 years old. The
magneto is a self-contained generator of high voltage that provides ignition to an engine through
spark plugs. A magnet-hence magneto-spins
in close proximity to a coil of wire. As the
magnet spins (or the magnet rotor is turned), it
generates a strong magnetic force that is "held
back" by a primary coil. The moment the contact
points open, a rapid magnetic flow generates a high
voltage in the secondary coil, which ignites the spark
plug, thus firing the engine. The two magnetos on
most GA aircraft-the left and the right-each fire
one of two spark plugs on each cylinder. There are
two magnetos so that if one fails the engine continues to run, but will be less efficient. Magneto ignition
systems are used primarily
in lawn motors, chain saws,
and old tractors; they have
R L BOTH
remained a source of power
OFF
START
in light aircraft because they
are self-contained and not
attached to battery or electric
systems in the aircraft, allowing the engine to continue to
run even during a battery or
electrical failure. Historically
the FAA has required that the
ignition in aircraft be separate
from the battery/electrical system, but newer and
better-performing electronic
ignition systems are gaining
acceptance. 

Magneto housing
Rotating magnet

Contact points

Any relative
motion between
magnet and
wire induces
current and
flow in the wire.

Pole shoe

Coil

Spark plugs

Right magneto

STEVE KARP

Left magneto

AOPA.ORG/FT  17



http://www.AOPA.ORG/FT

Flight Training - December 2019

Table of Contents for the Digital Edition of Flight Training - December 2019

Contents
Flight Training - December 2019 - Cover4
Flight Training - December 2019 - Cover1
Flight Training - December 2019 - Cover2
Flight Training - December 2019 - Contents
Flight Training - December 2019 - 2
Flight Training - December 2019 - 3
Flight Training - December 2019 - 4
Flight Training - December 2019 - 5
Flight Training - December 2019 - 6
Flight Training - December 2019 - 7
Flight Training - December 2019 - 8
Flight Training - December 2019 - 9
Flight Training - December 2019 - 10
Flight Training - December 2019 - 11
Flight Training - December 2019 - 12
Flight Training - December 2019 - 13
Flight Training - December 2019 - 14
Flight Training - December 2019 - 15
Flight Training - December 2019 - 16
Flight Training - December 2019 - 17
Flight Training - December 2019 - 18
Flight Training - December 2019 - 19
Flight Training - December 2019 - 20
Flight Training - December 2019 - 21
Flight Training - December 2019 - 22
Flight Training - December 2019 - 23
Flight Training - December 2019 - 24
Flight Training - December 2019 - 25
Flight Training - December 2019 - 26
Flight Training - December 2019 - 27
Flight Training - December 2019 - 28
Flight Training - December 2019 - 29
Flight Training - December 2019 - 30
Flight Training - December 2019 - 31
Flight Training - December 2019 - 32
Flight Training - December 2019 - 33
Flight Training - December 2019 - 34
Flight Training - December 2019 - 35
Flight Training - December 2019 - 36
Flight Training - December 2019 - 37
Flight Training - December 2019 - 38
Flight Training - December 2019 - 39
Flight Training - December 2019 - 40
Flight Training - December 2019 - 41
Flight Training - December 2019 - 42
Flight Training - December 2019 - 43
Flight Training - December 2019 - 44
Flight Training - December 2019 - 45
Flight Training - December 2019 - 46
Flight Training - December 2019 - 47
Flight Training - December 2019 - 48
Flight Training - December 2019 - 49
Flight Training - December 2019 - 50
Flight Training - December 2019 - 51
Flight Training - December 2019 - 52
Flight Training - December 2019 - 53
Flight Training - December 2019 - 54
Flight Training - December 2019 - 55
Flight Training - December 2019 - 56
Flight Training - December 2019 - 57
Flight Training - December 2019 - 58
Flight Training - December 2019 - 59
Flight Training - December 2019 - 60
Flight Training - December 2019 - 61
Flight Training - December 2019 - 62
Flight Training - December 2019 - 63
Flight Training - December 2019 - 64
Flight Training - December 2019 - 65
Flight Training - December 2019 - 66
Flight Training - December 2019 - 67
Flight Training - December 2019 - 68
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Flight Training - December 2019 - 70
Flight Training - December 2019 - 71
Flight Training - December 2019 - 72
Flight Training - December 2019 - Cover3
Flight Training - December 2019 - Cover4
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