Piper SENECA III - Page 296

SECTION 9
PIPER
AIRCRAFT CORPORATION
SUPPLEMENT
6
PA-34-220T, SENECA IH
Electrothermal
propeller
deicer pads
are
bonded
to
the
leading
edges
of the
propeller
blades. The
system
is
controlled by
an
ON-OFF
type
PROP
DE-lCE
switch
(Figure
9-3)
located
to
the
right
of
the
surface
deice
switch
Power
for
the
propeller
deicers is
supplied
by
the
airplane's electrical
system
through
a
PROP DE-lCE
circuit
breaker
in
the
circuit
breaker
panel.
When
the
prop
deice switch
is
actuated,
power
is
applied
to
a
timer
through the
PROP DE-lCER
ammeter
which monitors
the
current
through
the
propeller
deicing
system.
With the propeller
deicing
system
on,
the
prop
deicer
ammeter
needle
should
indicate within the
shaded
portion
of
the
ammeter
for
a
normal
reading.
Power
from
the
timer is
cycled
to
brush
assemblies which
distribute
power
to
slip
rings.
The
current
is then
supplied from the
slip rings
directly
to
the
electrothermal propeller
deícer
pads.
The
Hartzell
2-blade
propellers
are
deiced by
heating the
outboard
half
and
then the
inboard
half of
the
deicer
pads
in
a
timer
controlled
sequence.
The
heating
sequence
of
the
deicer
pads
is conducted
in the
following
order:
(a)
Outboard halves
of the propeller
deicer pads
on
the
right engine.
(b)
Inboard halves
of
the
propeller deicer pads
on
the
right
engine.
(c)
Outboard
halves
of
the
propeller
deicer pads
on
the
left engine.
(d)
Inboard
halves
of
the
propeller
deicer pads
on
the
left
engine.
The
optional
McCauley
3-blade propellers
are
deiced
by
heating
the
entire
deicer pads
alternately
in
the
following
sequence:
(a)
The
entire
deicer pads
on
the
right
engine
for
90
seconds.
(b)
The
entire
deicer pads
on
the
left
engine
for 90
seconds.
When
the
system
is
turned
ON,
heating
may
begin
on any
one
of
the
above
steps,
depending
upon
the
positioning
of the
timer
switch
when
the
system
was
turned
OFF
from previous
use.
Once begun,
cycling
will proceed
in
the above
sequence
and
will
continue
until
the
system
is
turned
off.
A
preflight
check
of
the
propeller
deicers
can
be
performed
by
turning
the
prop
deice
switch
on
and
feeling
the
propeller
deicer
pads
for
proper
heating
sequence.
The
deicer pad
should become
warm
to
the
touch.
The
heat
provided by the
deicer
pads
reduces
the
adhesion
between
the
ice and
the
propeller
so
that
centrifugal
force
and the
blast
of
airstream
cause
the
ice
to
be
thrown
off
the
propeller
blades.in
very
small
pieces.
REPORT: VB-1110
ISSUED:
JANUARY 8;
1981
9-48,
.4
of
10