Learjet 60 - Horizontal Stabilizer Anti-Ice; STAB WING HEAT Switch - Stabilizer Heat Function; WING HT Light

Pilot's Manual
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Learjet 60
WING HT LIGHT
The
amber WING HT
light,
on the glareshield annunciator
panel, will
illuminate
to indicate the
wing
anti-ice system is not
maintaining
the
temperature of the
leading
edge
in
the
normal
operating
range
.
In
the
event that the
wing leading
edge heats to
215°F
(102°C), the overheat
thermoswitch located on the
inner
skin of the
right wing leading
edge
will
cause the
light
to
illuminate
.
If
the
wing leading
edge temperature
cools to 55°F (13°C) and the
STAB
WING
HEAT
switch is
on,
the under-
heat thermoswitch located on
inner
skin of the
right wing leading
edge
will
cause the
light
to
illuminate
.
The light will illuminate
upon
initial
activation of the
wing
anti-ice system
if
the
wing
temperature is below
the set point of the underheat thermoswitch
.
As the temperature of the
wing leading
edge rises, the
light
should
extinguish .
HORIZONTAL STABILIZER ANTI-ICE
The horizontal
stabilizer anti-ice system utilizes sequenced electrical
heating
elements
along
the
horizontal
stabilizer
leading
edge .
The
sys-
tem consists of an electrically heated blanket bonded to each
half
of the
horizontal
stabilizer
leading
edge, three remote control circuit breakers
(RCCB),
a heat
controller,
a caution
light,
a system switch, and associ-
ated aircraft
wiring .
Control circuits operate on 28 VDC supplied
through the
1-amp STAB HEAT
circuit breaker on the copilot's circuit
breaker
panel .
Electrical power
for
the
heating
elements is 28 VDC
supplied through three 50-amp current
limiters
.
STAB WING HEAT SWITCH - STABILIZER HEAT FUNCTION
The horizontal
stabilizer anti-ice system is controlled through the
STAB
WING
HEAT
switch located
in
the
ANTI-ICE
group on the center
switch
panel . The
switch has two positions : On
(STAB
WING
HEAT)
and
OFF .
When the aircraft is
in flight
and the
STAB
WING
HEAT
switch is
On,
28 VDC is supplied through the three RCCBs to the heat
controller
. The
heat controller distributes intermittent electrical power
to the individual
heating
elements
in
a forward-to-aft sequence of 15
seconds duration each
. Approximately
3 minutes are required to
complete a
full
cycle .
The
center, or
parting
elements, are supplied with
continuous electrical power
.
At least one
engine
generator must be
operating to enable the heat controller circuits .
The
controller circuits
are biased by starter engaged and weight-on-wheels
signals
; therefore,
the system is inoperative when the squat switch is
in
the ground mode
and
during engine
start .
6-8
PM-123
Change 5