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CGS Ground School
Technical
The Vigilant Electrical System
© Crown Copyright 2012
No Part of this presentation may be reproduced without the permission of the issuing authority.
The views expressed in this presentation do not necessarily reflect the views or policy of the MOD.
TERMINOLOGY
A/C – Alternating Current. With alternating current, the
flow of electricity periodically reverses direction.
D/C – Direct Current. With direct current, the flow of
electricity is only in one direction.
Alternator – An engine driven system whereby a
magnet is rotated inside a wire coil. The alternator
produces alternating current (A/C).
Generator – This is simply an alternator fitted with a
device called a rectifier. The rectifier converts the A/C
output into D/C output.
Circuit Breaker (c/b) – A circuit breaker is a device
within an electrical circuit that can either be activated by
the pilot ‘pulling’ it, or by the aircraft system ‘popping’ it.
A c/b will be rated to a certain amperage, if this figure is
exceeded the c/b will ‘pop’ and stand proud in its
housing.
Fuse – A device within a circuit similar to a c/b but a
fuse can’t be reset.
PARTS OF THE
SYSTEM
Main busbar
The Vigilant
electrical system
+ve from
has a number of
load bus
components:
A
generator
fuse.
This
islinked
ais50
Allstarter
Three
An
A
main
mainswitch
of
engine
these
busbars:
fuse.
motor
driven
devices
This
Agenerator
busbar
isare
a 40
a
12v
28a
battery
ampere
circuit
labelled
viaprovide
series
ampere
to
an of
electrical
circuit
conductors
D/C.breaker
breaker
circuit.
carrying
‘GENERATOR
FUSE’.
Despite
all power‘MAIN
labelled
to or from
FUSE’.
a station.
it’s
namethe
it isname
actually
Despite
it is a circuit
breaker
is also
referred to
actually and
a circuit
breaker.
as the Alternator c/b.
- ve
+ ve
12 V
GEN
FUSE
MAIN
FUSE
Avionics busbar
-30
+30
Load busbar
START UP
Main busbar
Although
This
With
energises
the engine
this a
The load
busbar
relay
running
looks
which
complex,
the
oil it
provides
electricity
+ve from
connects
pressure
operates
very
the
to
the generator
load bus
battery
increases.
simply.
relay. to the main
An
oilthe
pressure
switch
then
circuit.
With
generator
relay
When the
connects
circuit
to the
energised,
themain
electricity
from
When
thethe
ignition
key
is turned,
mainswitch
is
load
busbar.motor
the
generator
flows into the
the
started
switched
‘ON’, is earthed and
main
circuit.
turns
part ofthe
theengine
circuit which then
turns
the generator.
is earthed.
GEN
FUSE
MAIN
FUSE
Avionics busbar
-30
+30
Load busbar
- ve
+ ve
12 V
All
these electrical
TheofVigilant
has threedevices
busbars.
are
protected from
Thefurther
Main busbar.
surges
by independent
The Avionics
busbar. c/bs.
The
havebusbar.
different ratings
And c/bs
the Load
depending
on what
piece of
The main busbar
supplies
equipment
electricity tothey
the:are protecting.
BUSBARS
Main busbar
5
1
5
Avionics busbar
1
5
5
1
1
Electric fuel pump
Fuel quantity sensor
Artificial horizon
Outside air temp gauge
Turn and slip indicator
Instrument lights
Engine instruments
RPM Gauge
The avionics busbar supplies
electricity to the:
Load busbar
5
2
When
the
engine
is of
switched
To
the
testing
the lights
Allallow
of these
c/bs
are
located
in off,
the
pressure
switch
during
thisthe
the oil
footmaintenance,
well underneath
disconnects
thebe
link
between
the
disconnect
can
by-passed
by
right hand instrument
panel
circuitswitch
and the
loadthe
busbar.
amain
guarded
under
engine cowling.
►
►
►
►
►
►
►
►
► Radio
► Transponder
The load busbar supplies
electricity to the:
15
10
10
1
1
►
►
►
►
►
Strobe lights
Landing lights
Navigation lights
Engine hours counter
Generator relay
MALFUNCTIONS
Main busbar
As
such
ammeter will
Overvolting
This
thenthe
disconnects
the
show
a discharge
the
generator
from theand
main
If
the voltmeter reads above
voltmeter
a from
circuit. will indicate +ve
load bus
15v
or thevoltage.
ammeter indicates
reducing
The aircraft
electrical
above
+20electrical
amperesloads
charge,
Reducing
circuit is now
fed purely
pull
the alternator
c/b
will
prolong
the battery
by the
battery.
(generator
fuse). This is
life.
usually
caused
Switching
off allby
of the
the failure
of
the will
voltage
on the
lights
haveregulator
the
generator.
biggest effect.
- ve
+ ve
12 V
GEN
FUSE
MAIN
FUSE
Avionics busbar
-30
+30
Load busbar
MALFUNCTIONS
Main busbar
If the generator
Undervolting
c/b pops again
c/b has
or if
it hadn’t popped
‘popped’,
the aircraft
initially,
will
If the voltmeter
less
alternator reads
belt does
+ve
from
reduce
be
usingthe
battery
electrical
power
than12v
the ammeter
snap,
theorRPM
gaugeload
willbus
loads (all lights in the first
only.
indicates
-5the
read
zerobelow
despite
instance) and then land
amperes
Initially
push
charge,
thenormally.
c/b
ensure
back
engine running
as soon as practicable.
the generator c/b is in.
in.
This could also be
ONLY EVER RESET A
caused by the alternator
C/B ONCE
belt snapping.
- ve
+ ve
12 V
GEN
FUSE
MAIN
FUSE
Avionics busbar
-30
+30
Load busbar
MALFUNCTIONS
Main busbar
Initiallyc/b
Main
reset the c/b.
Be aware that if it has
If
ONLY
the main
EVER
c/bRESET
pops
is from
+ve
popped
again,
none itofA
trying
C/B
ONCE
to protect
the load bus
the electrical
services
electrical
components
on
provided
by
the land
busbars,
If it pops again,
as
the
busbarthe
against
including
radio, a
soon as practicable.
surge
(more and
thanthe
40 RPM
transponder
amps).
gauge will work.
GEN
FUSE
MAIN
FUSE
Avionics busbar
-30
+30
Load busbar
- ve
+ ve
12 V
THE END
Any Questions?