The goal is to provide the student with an opportunity to "review" the course. It focuses on important facts that are repeated throughout the exams and also on the subject of classes. It can also cover material not included in the databases but important to understand some areas that are also impor...
• Electron
Flow
=
-‐-‐
VE
to
+
VE
! !
• In
parallel:
! = ! + ! + !
! ! 𝑅!
• Conventional
Flow
=
+
VE
to
-‐
VE
! ! ! !
• More
resistors,
when
added
in
parallel,
will
ELECTRICAL
CURRENTS
cause
total
resistance
to
decrease
and
current
increase
(assuming
V
is
constant).
𝑪𝒐𝒖𝒍𝒐𝒎𝒃𝒔
• 𝑨𝒎𝒑𝒆𝒓𝒆 = 𝑺𝒆𝒄𝒐𝒏𝒅𝒔
• The
coulomb
=
6.25
x
1018
electrons.
OHM’S
LAW
• I
=
Q
/
t
• Ammeter
connected
in
series.
• V
(Voltage)
=
I
(Current)
x
R
(Resistance)
, ELECTRICS
2
–
AIRCRAFT
WIRING
AND
PROTECTIONS
CIRCUIT
LIMITER
DIPOLE
/
TWO
–
WIRE
SYSTEM
SHORT
CIRCUITS
• Will
allow
for
a
high
transient
load.
• Mainly
used
on
aircraft
constructed
from
• Occurs
when
the
load
is
bypassed.
• Only
breaks
with
high
continuous
overload.
non-‐conductive
/
non-‐metallic
materials.
• Extremely
high
current
will
flow
due
to
• Normally
used
to
protect
heavy
duty
circuits
such
as
negligible
resistance.
the
bus
bar.
• Can
cause
damage
to
circuit
/
burn
cables
/
• Constructed
of
a
high
melting
point
filament
in
a
ceramic
housing.
UNIPOLE
SYSTEM
cause
a
fire.
CIRCUIT
BREAKERS
• A.K.A:
Single
Pole
/
Earth
Return
System
• Metallic
airframe
acts
as
the
return
path
• Can
be
reset
so
no
spare
fuses
required.
between
load
and
the
power
source.
• Can
be
used
as
switches
to
aid
in
diagnosis
• Reduces
wiring
and
saves
space
• When
popped,
a
white
band
will
show.
• Low
resistance
–
Due
to
big
cross
section
• Protects
system
in
event
of
overload
/
• Saves
weight
OPEN
CIRCUITS
overheating.
Fitted
in
series.
• Easier
to
trace
origin
of
wiring
faults.
Can
be
used
in
both
AC
&
DC
circuits.
•
• Short
circuits
are
more
likely
however.
• When
there
is
a
break
in
a
conductor.
• Can
be
thermal
(bi-‐metallic)
or
magnetic.
• Load
becomes
inoperative
like
opening
a
o Magnetic
is
quicker
to
respond
as
it
switch.
does
not
rely
on
heating.
COMMON
REFERENCE
POINT
Thermal
CB
protects
the
system
in
the
event
•
of
a
prolonged
overcurrent
(delayed
due
to
• Earth
is
always
0
V
time
taken
to
heat
bi-‐metallic
strip)
• If
earth
is
at
–
ve
terminal:
• CB
should
only
be
re-‐set
if
necessary
for
o “Negative
Earth”
safe
flight
and
landing
and
fault
has
been
o +
ve
battery
terminal
is
12
V
rectified.
• If
earth
is
at
+
ve
terminal:
• Only
one
reset
should
be
attempted.
o “Positive
Earth”
FUSES
o -‐
ve
battery
terminal
is
-‐12
V
• Spare
Fuses
-‐
10%
with
a
minimum
of
3
for
each
NON
–
TRIP
FREE
CB
• In
either
case,
the
PD
is
still
12
V
(not
+12
V
rating.
or
–
12V)
• Rated
in
amperes
(A)
• The
CB
can
be
held
in
against
the
fault
o The
amp
capacity
of
device
to
be
protected
however
which
can
cause
damage.
should
be
checked
before
installing.
• Constructed
of
a
low
melting
point
filament
in
a
glass
or
ceramic
envelope.
• Located
as
near
to
the
supply
as
possible.
• Only
ever
replace
once
in
flight.
, ELECTRICS
2
–
AIRCRAFT
WIRING
AND
PROTECTIONS
TRIP
FREE
CB
CAUSES
OF
STATIC
ELECTRICITY
GROUNDING
• Secondary
contact
prevents
early
re-‐set.
• Friction
(Skin
&
Propellers)
• Will
equalise
the
airframe
to
0V
and
• It
is
not
possible
to
hold
the
contacts
closed
• Lightning
remove
the
static
charge
that
has
built
up
while
current
fault
exists.
• Electrical
circuits
&
equipment
during
flight.
EFFECTS
OF
STATIC
ELECTRICITY
STATIC
DISCHARGE
WICKS
• Materials
attract
/
repel
each
other.
• If
a
static
charge
on
the
aircraft
fails
to
• Sparks
and
associated
fire
risk.
dissipate,
corona
discharge
occurs.
(Min
• ‘Pitting’
of
materials
leading
to
corrosion.
radii
/
causes
glow
+
interference)
• Interference
with
radio
equipment.
• Static
discharge
wicks
on
the
trailing
edges:
MECHANICAL
SWITCHES
• St
Elmo’s
Fire
o Safely
dissipate
static
charges
o Minimise
radio
interference
o Limit
risk
of
transfer
of
electrical
BONDING
charges
between
aircraft
and
electrified
clouds.
• Bonding
is
the
connection
of
two
or
more
metallic
objects
by
means
of
a
conductor.
LANDING
PROTECTION
• Achieved
using
bonding
strips.
• Creates
a
faraday
cage.
• Earthing
strips
or
semi-‐conductive
tyres
are
• A
electrical
path
of
negligible
resistance
is
used
to
eqaulise
to
earth
potential.
created
throughout
the
structure.
LIGHTNING
STRIKES
STATIC
ELECTRICITY
PURPOSE
OF
BONDING
• Some
components
may
become
magnetised
• “A
build
up
of
electrical
charge
on
the
• Equalising
of
static
charges
/
potential
if
struck
and
compass
becomes
inaccurate.
surface
objects.”
• Provide
a
single
earth
for
unipole
system
• Some
electrical
systems
may
also
fail.
• Occurs
when
electrons
are
transferred
• Safe
transmission
of
lightning
discharges
between
materials.
A.K.A
Tribolectric
• Reduce
interference
(sign
of
poor
bonding)
SCREENING
effect.
• Prevention
of
electric
shocks
• Most
likely
in
dry
/
low
humidity
air
or
in
• Prevention
of
static
discharges
(fire
haz)
• Enclosing
of
cables
in
a
continuous
metal
extreme
turbulence.
• Provides
safe
distribution
of
electrical
sheath
to
reduce
radio
interference.
charges
and
currents
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