FlightSafety LEARJET 45 - Wing;Stab Anti-Ice System

WING/STAB ANTI-ICE SYSTEM
General
The wing/stab anti-ice system (Figure 10-6)
utilizes high pressure bleed-air directed
through piccolo (diffuser) tubes in the lead-
ing edge of the wings and the horizontal sta-
bilizer. The hot bleed-air to the wings warms
the leading edge and is then directed into the
center wing area. The heated air from the hor-
izontal stabilizer is vented overboard at the out-
board ends of the stabilizer.
System components consist of the piccolo
tubes, anti-ice pressure regulating and shut-
off valves (PRSOVs), anti-ice check valves,
WING/STAB on/off control switch, wing tem-
perature control and under/overheat sensors,
horizontal stabilizer overheat sensors, CAS
system messages, electrical circuitry, and in-
puts from the integrated ECS temperature
controller.
The wing/stab anti-ice system is powered by
28 VDC from the left and right main busses
respectively, and is protected by circuit break-
ers labeled L and R WING/STAB HT on the
pilot and copilot circuit breaker panels. Loss
of electrical power will cause the wing/stab
anti-ice shutoff valves to close. Should the
airplane experience a single generator fail-
ure, the system is not affected. Should both
generators fail inflight the main bus contac-
tors automatically open, depowering the main
busses and the wing/stab anti-ice control
valves. The main busses must be re-selected
manually if it is necessary to restore wing/stab
anti-ice.
Operation
The wing/stab anti-ice system is selected on
by depressing the WING/STAB switch/indi-
cator (S/I), located on the anti-ice control
panel (Figure 10-2). When the S/I is depressed
an ON caption illuminates within the switch;
when the system is off the S/I is blank.
When selected ON, both anti-ice pressure reg-
ulating and shutoff valves (PRSOVs) are en-
ergized open (Figure 10-6).
The A/I PRSOVs are opened and closed (mod-
ulated) by regulating the amount of servo air
used to push the valves open against spring
pressure. The servo air to the A/I PRSOVs is
electrically contolled by the two-channel ECS
Temperature Controller through a torque motor
and shut-off solenoid on each side. Electrical
power to the shut-off solenoids is provided
when the Wing/Stab S/I is ON, but the circuits
also go through the BLEED S/Is. The shut-off
solenoids on each A/I PRSOV are only ener-
gized open when the corresponding BLEED
A/I is ON. However, the system does incor-
porate a pneumatic cross-over capability that
allows both A/I PRSOVs to open in the event
of power loss to the torque motor and shut-off
solenoid on either side. If either L or R
Wing/Stab HT circuit breaker is out, either
channel of the ECS Temperature Controller
fails, or either BLEED S/I is OFF, both A/I
PRSOVs should still function.
The integrated ECS temperature controller
normally uses single control channels for each
side to provide automatic control of the air-
plane wing and stabilizer leading edge skin
temperature. The controller maintains a tem-
perature range of 140 +
7° F (60° C).
Each wing is continuously monitored by a
wing temperature control sensor, mounted on
the inside surface of the wing leading edge,
near the wing root. The sensors supply the
sensed wing skin temperature information to
the integrated ECS temperature controller,
that regulates the amount of high-pressure
bleed-air allowed into the system. The ECS
controller does this by modulating the PRSOVs
on each side to maintain the colder of the two
wings at 140° F.
Under/overheat sensors also monitor wing and
stabilizer temperature and provide under/over-
heat signals to the controller. The controller
then relays these output warning signals
through the IC-600s for display on the CWP
and CAS (Figure 10-7). The amber “WING
TEMP LOW” or amber “STAB TEMP LOW”
CAS message will be displayed if the corre-
sponding surface is less than shown in Figure
10-6 with the WING/STAB heat switch on. The
CAS messages are inhibited for 2.5 minutes
10-9
FOR TRAINING PURPOSES ONLY
LEARJET 45 PILOT TRAINING MANUAL
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