Saab 340B, Руководство по эксплуатации

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ICE AND RAIN PROTECTION
Description
Aircraft Operations Manual
11.1
PAGE 5
Jun 01/17
− The L/R PROP DE − ICE lights (blue) on the flight
status panel which will come on when the system
is working and will go out in case of system fail-
ure.
− One ICE PROT light (amber) on the CWP which
will come on flashing together with MASTER
CAUTION in case of failure.
− Two L/R PROP lights (amber) on the overhead
panel will come on in case of failure.
During normal operation each propeller de − icer boot
is powered by it’s associated AC generator. In the
event of an engine or AC generator failure the pro-
pelled de
− icer boots are automatically powered
from the opposite side.
When the L/R PROP de − ice switch is in NORM/
MAX position 28 VDC will be applied to the timer/
switching/monitor unit. The timer unit alternately
turns on power to two opposite pair of blades.
In NORM position power is on for 11 seconds and
off for 79 seconds. In MAX position power is on for
90 seconds and off for 90 seconds.
It is very important to observe the temperature
switching point for use of NORM resp MAX modes.
If using MAX mode at temperatures warmer than
− 12

and NORM mode at temperatures warmer
than − 5

, there is a risk for the ice to melt and ”run
back” and re − freeze behind the boots. Run back will
cause a drastic reduction in Propeller thrust, up to
about 30%. However, MAX mode may be used in
the temperature range
− 10

to − 12

SAT if unac-
ceptable propeller vibrations are experienced. If un-
acceptable vibrations occur at warmer temperatures
than
− 10

SAT use MAX mode for a short period
until the vibrations disappear. Bear in mind the risk
for run back.
A timer fault monitoring unit will automatically dis-
connect the power and activate L or R PROP cau-
tion light in the ICE PROTECTION panel together
with ICE PROT CWP light whenever one or more of
the following faults arise:
− AC or DC power failure.
− Timer not cycling or remaining permanently on.
− Over − /Undercurrent to propeller boots.
− Cycling interval periods are off by more than

0.5%.
2.4 Windshield heating (Fig. 4)
The front windshields and the forward part of the
side windshields are electrically heated from the
115 VAC, wild frequency buses for anti
− icing. L AC
BUS supplies heating power for L front and side
windshields and R AC BUS supplies heating power
for R front and side windshields. In addition, air
from the air conditioning system is directed to the
inside of the windshields to prevent fogging as soon
as the air conditioning system is working.
The power used for heating is regulated by two con-
trollers. The left controller powers the left front and
right side windshields while the right controller pow-
ers the right front and left side windshields.
Once the windshields have reached their working
temperature, the controllers will modulate the power
output to keep this temperature. If an open or short
circuit occurs in the normal temperature sensor, the
over
− temperature sensor will take over and modu-
late the temperature together with the controller.
Each controller also provides overheat and fault
protection. If a controller detects an overheat sen-
sor circuit failure or a complete controller fault, it
shuts off power to the affected windshield and illu-
minates the respective windshield L/R SIDE or L/R
FRONT light. If, however, only the normal tempera-
ture circuit fails and the over
− temperature sensor
circuit takes over, the caution light will illuminate but
the windshield is still heated. Positioning the switch
for the affected windshield to OFF will extinguish
the caution light and resets the controller channel
for this windshield.
The front windshields heating can only be selected
ON or OFF. When set to ON, power is applied grad-
ually by the controller to reduce thermal stresses in
the windshields. If the windshields are cold, it may
take up to 6 minutes before full power is applied.
A/C 160 − 299
The side windshields have no low power warm-up
period. Instead, there are two power settings avail-
able, NORM and HIGH. NORM is used for defog-
ging while HIGH is used for de
− icing. When heating
is applied to a side windshield NORM setting must
be used for at least 7 minutes before HIGH may be
selected in order to reduce the thermal stresses. As
an additional precaution when HIGH is selected,