ICE AND RAIN PROTECTION AIRFRAME DE-ICING

Fokker 50 - Ice & Rain Protection
ICE AND RAIN PROTECTION
AIRFRAME DE-ICING
Description
Controls and indicators of the AIRFRAME DE-ICING system are located at the ice protection
panel.
Airframe de-icing is accomplished by alternately inflating and deflating rubber boots installed
on the leading edges of the wings and tail section. The boots are inflated and deflated in
sequence, symmetrically, across the airframe.
Engine bleed-air is supplied to the boots via pressure-regulating valves and distribution
valves. Each distribution valve has two outlets. If bleed-air pressure is insufficient either in
the supply line to the distribution valves or at the outlets of the tail distribution valves, a lowpressure alert will be presented. One engine can supply sufficient bleed-air for the de-icing
system.
The distribution valves are controlled by a cyclic timer. A de-icing cycle lasts about one
minute. Selection can be made for continuous (HEAVY) or periodic (LIGHT) operation. In
case of a timer fault, the distribution valves can be controlled by the MANUAL de-icing
selector.
The tail plane distribution valves are electrically heated.
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Fokker 50 - Ice & Rain Protection
Functional diagram
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Fokker 50 - Ice & Rain Protection
Controls and indicators
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Fokker 50 - Ice & Rain Protection
Alerts
CONDITION(S) / LEVEL
TIMER FAILURE
AURAL
MWL/MCL
2
CAUTION
TIMER FAILURE
CAP
LOCAL
TIMER
FAULT
LOW PRESS
2
CAUTION
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Fokker 50 - Ice & Rain Protection
ENGINE ANTI-ICING
Description
The formation of ice on propeller and spinner is prevented by electrical heating, and in the air
intake by electrical and bleed-air heating. In addition heated engine oil is used to prevent the
formation of ice on the inlet case of the LP compressor.
Controls and indicators of the electrical engine anti-icing system are located at the ice
protection panel and at the glare shield.
The system is armed to operate when the ENGINE ANTI-ICING pushbutton at the ice
protection panel is depressed to ON. When either ENGINE ANTI-ICING pushbutton is
depressed to ON, two ENG A-I lights, located at the glare shield, illuminate. The system is
activated when the Total Air Temperature (TAT) falls below 5ºC, provided the propeller
speed is above 50%. The system is automatically de-activated when TAT rises above 7ºC or
the propeller speed drops below 50%.
Several surfaces in the air intake are heated electrically and separately. The leading edge of
the air intake and part of the intake duct are heated continuously, while all other surfaces,
including propeller and spinner, are heated periodically. Periodic activity is controlled by a
cycle timer and varies automatically with ambient temperature.
If a fault in the heating of any surface is detected, an engine anti-icing alert will be presented
and the electrical power to that particular surface is switched off automatically. If the timer
fails, also indicated by the engine anti-icing alert, all electrical heating is disabled.
Part of the air intake is heated with bleed-air, tapped upstream of the PR/SO valve in the
engine bleed-air system. Bleed-air is admitted via a shut-off valve. The valve opens when the
ENGINE ANTI-ICING pushbutton is depressed to ON, irrespective of the TAT. If the system
is switched ON and no pressure is available, the engine anti-icing alert is presented.
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Fokker 50 - Ice & Rain Protection
Controls and indicators
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Fokker 50 - Ice & Rain Protection
Alerts
CONDITION(S) / LEVEL
ENGINE ANT-ICING
SYSTEM FAILURE
AURAL
MWL/MCL
2
CAP
LOCAL
L ENG
A-ICE
ENGINE
ANTI-ICING
OR
FAULT
CAUTION
ON
R ENG
A-ICE
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Fokker 50 - Ice & Rain Protection
WINDOW HEAT
Description
The flight deck front windows are heated electrically to prevent ice build-up, to increase bird
impact resistance, and to prevent misting.
Controls and indicators are located at the ice protection panel. Each front window has a
heating control unit. A temperature sensor in each window signals the actual temperature to
the related control unit which accordingly activates or de-activates the heating, provided the
window heat is selected on.
The side windows are not heated. Demisting of flight deck windows can be performed with
airflow from the airconditioning system. See AIRCONDITIONING/PRESSURIZATION.
Window heat type I
Each front window has a heating control unit. A temperature sensor in each window signals
the actual temperature to the related control unit which accordingly activates or de-activates
the heating, provided the window heat is selected on.
The window heat selector has three selector positions, OFF, LO and HI. Heat build-up is
slow in the LO mode and fast in the HI mode. Mode selection does not affect the
temperatures at which the window heat is activated and de-activated. If a failure is detected,
an alert will be presented. Fault detection is active when an other mode is selected, and
when electrical power is applied to the system provided the system is not selected OFF.
The left and right window can be switched OFF individually by depressing the respective
pushbutton located at the ice protection panel.
Window heat type II
Each front window has a heating control unit. A temperature sensor in each window signals
the actual temperature to the related control unit which accordingly activates or de-activates
the heating, provided the window heat is selected on.
The left and right window can be switched OFF individually by depressing the respective
pushbutton located at the ice protection panel.
If a failure is detected power to the heating element will be interrupted and an alert will be
presented.
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Fokker 50 - Ice & Rain Protection
Controls and indicators
Controls and indicators - Type I
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Fokker 50 - Ice & Rain Protection
Controls and indicators - Type II
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Fokker 50 - Ice & Rain Protection
Alerts
CONDITION(S) / LEVEL
AURAL
MWL/MCL
CAP
LOCAL
FAULT
WINDOW HEAT
FAILURE
1
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Fokker 50 - Ice & Rain Protection
PROBE AND VANE HEAT
Probe heat
To prevent the formation of ice on air data sensors, electrical heating is provided for pitotstatic heads and angle-of-attack vane.
Controls and indicators of the probe heat system are located at the ice protection panel. The
pitot heads are heated when the relevant pushbutton is blank and electrical power is
available. In battery-power-only condition, only the left-hand lower head (L LO), which
supplies information for the captain’s air data instruments, remains heated. In the event that
a pilot heat system fails or a pitot heat system is OFF when the parking brake is released, an
alert will be presented.
Vane heat
Type I
The angle-of-attack vane heater is active when the VANE pushbutton is blank and the
aircraft is airborne.
Type II
The angle-of-attack vane heater is active when the VANE pushbutton is blank.
All
In the event that the heater fails an alert will be presented.
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Fokker 50 - Ice & Rain Protection
Controls and indicators
Controls and indicators - Type I
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Fokker 50 - Ice & Rain Protection
Controls and indicators - Type II
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Fokker 50 - Ice & Rain Protection
Alerts
CONDITION(S) / LEVEL
PITOT HEAT OFF
AFTER PARKING
BRAKE RELEASE
AURAL
MWL/MCL
CAP
LOCAL
INOP
1
OFF
PITOTS
PITOT HEAT FAILURE
INOP
2
PITOT
HEAT
CAUTION
VANE
VANE HEAT FAILURE
INOP
2
CAUTION
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Fokker 50 - Ice & Rain Protection
RAIN PROTECTION
Description
Type I
Rain is removed from the flight deck front windows by two wipers. The wipers are driven by a
single four-speed electric motor, which is operated by the wiper speed selector at the
overhead panel. Wiper operation stops in the park position when the selector is turned via
OFF to PARK. The selector is spring loaded from PARK to OFF.
Type II
Rain is removed from the flight deck front windows by two wipers. The wipers each driven by
a two-speed electric motor are controlled by the window wiper speed selector at the
overhead panel. The selector has a low and a high position for operating the wipers. The
wipers will return to the park position when the selector is positioned to OFF.
Type III
Rain is removed from the flight deck front windows by two wipers. Each wiper is driven by an
independent two-speed electric motor, and can be controlled by the window wiper speed
selectors at the side panels. Each selector has a low and a high position for operating the
respective wiper, and a both high position for operating both wipers. The respective wiper will
return to the park position when the selector is positioned to OFF and the offside selector is
not in the both high position.
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Fokker 50 - Ice & Rain Protection
Controls and indicators
I
Controls and indicators - Type I
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Fokker 50 - Ice & Rain Protection
Controls and indicators - Type II
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Fokker 50 - Ice & Rain Protection
Controls and indicators - Type III
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Fokker 50 - Ice & Rain Protection
SYSTEM OPERATION
Engine anti-icing
Engine anti-icing must be switched ON when icing conditions are encountered or anticipated.
Switch anti-icing off three minutes after icing has ceased and in clear air.
Icing can be expected to occur when the ambient temperature or TAT is below plus 5 deg C,
when visible moisture is present or when standing water or slush is present on the ground.
CAUTION:
Use the criteria of TAT and visible moisture for switching on the engine Antiicing system.
Insufficient ice shedding from the non-heated parts of the propeller is noticed as propeller
vibration.
If ice on propeller is noticed as propeller causes excessive vibration:
ERP ..............................................................SELECT MCT
TORQUE .............................................................. ADJUST
Set torque according to tables ERP INOPERATIVE
Airframe de-icing
On ground procedure
If the airplane was parked overnight in sub-zero temperatures, it is recommended to check
airframe de-icing operation before the first flight of the day. After engine start operate the
system in MANUAL 1 and 2 twice and visually check the wing leading edge boots outside the
engine nacelle for inflation.
In-flight procedure
When ice deposits are detected, the airframe de-icing system must be switched to LIGHT.
When the thickness of the ice deposit layer building up between cycles, is estimated to be
more than ¼ inch (6 mm) or when the crew judges that conditions so justify, select HEAVY.
The airframe de-icing system must be kept in operation as long as ice accumulation
continues. When the ice has been removed the system must be switched OFF. Some
residual ice is normal, especially with low TAT’s.
Before commencing the approach at a TAT below plus 10 deg C, select the airframe de-icing
system to HEAVY for approx 3 minutes to clear the airframe of any residual ice unless it is
confirmed that the wing boots are clean.
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Fokker 50 - Ice & Rain Protection
Window heat
The window heat must be switched on when TAT is below plus 18 degrees C.
For type I window heat
Operate the heating at least 3 minutes in LO before using HI.
Probe heat
All probe heaters should be switched ON whenever the aircraft is moved by its own power.
Wiper
Use wipers with precipitation only.
Operation with engine anti-icing inoperative
Operate the aircraft such that no icing conditions will be encountered.
Operation in icing conditions with engine anti-icing OFF
CAUTION:
In case of too late a detection of icing conditions, operate engine anti-Icing
on one engine at a time with an interval of two minutes.
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