30 Ice & Rain protection
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TTP |
B1-L3 |
ATA 30 |
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Beech 90 Series |
B2-L3 |
Ice &
Rain Protection |
The pneumatic/vacuum system of the aircraft distributes bleed air for the surface deice system to operate the pneumatic boots along the wing and tail surface leading edges. Electrically-heated deicer boots deice the propellers.
The air stall warning vane, pitot masts, and protruding fuel vents are electrically heated to prevent ice buildup. The inertial anti-icing system separates ice-laden air from clean air for engine intake. Electrically-heated elements prevent ice buildup on the windshields.
DEICE SYSTEMS
SURFACE DEICE SYSTEM
Description
The surface deice boots are pneumatically inflatable boots on the leading edge of the wing and tail surfaces. Inflation of the boots breaks accumulated ice and impact air removes accumulated ice. The boots are inflated with 18 psi pressure and are deflated with vacuum from the pneumatic system. These pressures are routed through and controlled by the deice distribution valve under the outboard right seat track in the cabin below the second cabin window. A control switch on the pilot right subpanel is spring loaded to the OFF position.
SURFACE DEICE
Switch
The
SURFACE DEICE switch selects the operational
mode for the pneumatic deice boots.
This switch has two positions as
follows:
• SINGLE—Inflates the wing boots first for approximately six
seconds and then the vertical and horizontal stabilizer boots for approximately four seconds.
•
MANUAL—Inflates all boots simultaneously for as long as the switch
is held down.
Momentarily selecting the SINGLE switch position initiates a single-cycle, semiautomatic mode of operation. The left and right wings then inflate to 18 psi for approximately six seconds and then all three of the tail boots inflate for four seconds. The cycle is now complete and the mode must be reinitiated if additional cycling is required. When the boots are not inflated, vacuum is supplied through the deice distribution valve to hold the boots in a deflated state. The timing circuitry is on a printed circuit board under the center aisle floorboards aft of the main wing spar.
Holding the control switch to MANUAL bypasses the timer circuits of the printed circuit board and inflates all of the boots, both wing and tail, for as long as the switch is held in the MANUAL position.
Deice Boot Maintenance
The surface of the deicer boots should be checked for indications of engine oil after servicing and at the end of each flight. Any oil spots should be removed with a non-detergent soap and water solution. Exercise care during cleaning to avoid scrubbing the surface of the boots, which tends to remove the special graphite surfacing. Use isopropyl alcohol to remove substances which cannot be removed using soap and water; however, the boot must be washed again with mild soap and water, and allowed to dry. The deicer boots are made of soft, flexible neoprene material and may be damaged if fuel hoses are dragged over them, or, if ladders or platforms are rested against the boots. Boot life can be substantially increased by the periodical application of Age Master. The looks of the boots can be enhanced with the use of Shine Master and the ice-shedding properties can be improved with the use of Icex II.
Minor scuffed areas on the boots normally require only the restoration of the conductive surface in the immediate area. However, if the entire surface ply has been removed, exposing the brown natural rubber underlay, or if the boot is cut, torn or ruptured, it is necessary to patch the damage. Deicer Boot Repair Kit 74-451-AA contains cold patches suitable for repairing damaged areas. A cold patch on a deicer boot is considered a permanent repair. Replace any boot that has a cut, torn or ruptured that exceeds 3/4 inch in length.
PROP Switch
The
PROP switch activates the electric
heating elements in the propeller
boots. The switch has
two positions as follows:
• OFF—Deactivates electric heating
elements.
• ON—Activates the automatic timer which directs current to the single-element propeller boot on
each blade in sequence as follows:
° 90 seconds to all boots on one propeller
° 90
seconds
to
all
boots
on
the
other
propeller
Overhead Panel
PROP AMPS Gauge
The PROP AMPS gauge indicates the amount of current applied to the single-element propeller boot on each blade. Current range is 14 to 18 amps for three-bladed propellers and 18 to 24 amps for four-bladed propellers.
Propeller Deicing System
The
electric deice system for the propeller
includes the following (Figures
30-4 and 30-5):
• Electrically-heated
deicer boots
• Slip ring and brush block
assemblies
• An automatic timer
• An ammeter with its shunt
•
A circuit-breaker switch
on
the
pilot
inboard subpanel
When the prop deice switch is turned on, the automatic timer directs current to all of the single element propeller boots on one propeller for 90 seconds. The automatic timer then cycles to all the boots on the other propeller for 90 seconds. The 90-second cycling from one propeller to the other continues as long as the system is turned on. During normal operation the propeller ammeter, on the overhead instrument panel, indicates a range of 14 to 18 amps for three-bladed propellers and 18 to 24 amps for four-bladed propellers. Loss of the heating element circuit on one blade does not effect system operation (although propeller imbalance and vibration may occur).
There are no provisions for manual propeller deicing on the King Air C90 aircraft.
Whenever the prop deicing is turned on, operation of the electric heater system is disabled.
ANTI-ICE SYSTEM
STALL WARNING
A stall warning system provides a stall warning light and horn to notify the crew of an impending stall condition. A movable transducer vane on the leading edge of the left wing triggers
the system. Ice protection for the vane is provided through two electrical resistive heaters in the vane assembly. One heater is contained in the vane and another is contained in the plate surrounding the vane. The vane heater is powered through the 5-AMP CB on the copilot circuit-breaker panel. The plate heater is powered through the circuit-breaker switch on the ice-protection switch panel.
Controls and Indications
STALL WARN Switch
The
battery switch activates the heating element in the stall warning transducer vane. The STALL WARN switch activates the electric heating
element in the stall warning
transducer plate. It has two
positions as follows:
•
OFF—Deactivates the heating
element in the stall warning
plate.
• ON—Activates the heating element in the stall warning plate.
PITOT HEAT
The left and right pitot masts are electrically heated to ensure against
freezing during icing conditions. 7.5-amp circuit- breaker switches,
placarded PITOT, LEFT, and
RIGHT, on the pilot inboard subpanel, power the pitot heating elements.
The left and right PITOT switches activate electric heating elements in the pitot masts. They have two positions as follows:
• OFF—Deactivates heating elements.
• ON—Activates heating elements.
PITOT SYSTEM DEICER
Standard System
A heating element in each of the pitot masts prevents the pitot opening from becoming clogged with ice. Application of power to the heating element of each mast is controlled by individual left or right pitot heat 7.5-amp circuit breaker switches. This system does not provide indications to the operator if there is a loss of pitot heat to the mast.
Monitored System (LJ-1847, LJ-1853 and After)
A heating element in each of the pitot masts prevents the pitot opening from becoming clogged with ice. Application of power to the heating element of each mast is controlled by individual left or right pitot heat 7.5-amp circuit breakers switches. The power is fed from the circuit breaker through a current sensor and then onto the heating element. As long as there is a flow of current through the current sensor, the appropriate caution indicator is extinguished. Loss of current flow results in the closing of the contact in the current sensor and the application of annunciator indicator power to the circuit of the annunciator detection circuit card. This results in the illumination of the appropriate caution indicator.
INERTIAL ANTI-ICING SYSTEM
An inertial ice separation system is in each engine air inlet to prevent moisture particles from entering the engine inlet plenum during icing conditions. The system consists of two, electrically-actuated movable doors or vanes in each engine air inlet duct. In normal operation, the vanes are positioned with the forward vane retracted (up) and the aft vane extended (down), which directs all in-coming air into the engine air plenum. When icing conditions are encountered, the forward door is lowered into the inlet airstream to induce an abrupt turn into the airflow before entering the engine plenum and the aft vane is retracted.
The heavy, ice-laden air is then discharged over- board through the lower aft cowling. The doors are extended and retracted simultaneously through a linkage system connected to an electrically-driven, dual-motor actuator.
Two individual
switches, on the pilot outboard
subpanel and placarded LEFT &
RIGHT ENGINE ANTI-ICE–ON–OFF,
control the actuators
on
the left and right engines.
Turning the switches to ON extends the forward
vanes (and retract the aft vanes).
Turning the switches
to OFF retracts the forward vanes (and extend
the aft vanes).
Two sets
of microswitches on each side
act through right and left printed circuit boards, in the left wing
center section, to monitor the position of the
vanes.
Illumination of the L–R
ENG ANTI-ICE green annunciators indicate
the system is actuated.
Should the vanes fail to correctly position within 33 ± 4
seconds after the system is actuated, the appropriate L–R ENG ICE FAIL
amber annunciator illuminates.
Two additional switches, just underneath the right and left engine anti-ice switches and placarded ACTUATORS STANDBY and MAIN, are used to select which internal motor drives the actuator. If one motor fails to operate the system, the other motor can be used. There are no restrictions on using standby motor and either motor can be used to operate the system.
ENGINE
INLET ANTI-ICING
Engine air inlet anti-icing is always in operation when the engine is running. Exhaust gases are picked up by a scoop in the left engine exhaust stack, routed through the engine intake lip, and then exhausted out through the right exhaust stack.
WINDSHIELD
ANTI-ICING Description
The windshield anti-ice system consists of a windshield with an embedded electronic heating element and a solid-state controller to cycle power through one or two relays to prevent icing. The pilot and copilot systems are two independent systems; however, they are identical in operation. Switches located on the pilot inboard subpanel labeled OFF, NORMAL and HI actuate each system. Whenever the windshield heat is functioning, operation of the electric heater system is disabled.
The windshield is comprised
of two plies of tempered glass
bonded together with a layer of
polyvinylbutyl (PVB).
The electric heating element and a temperature-sensing element is embedded in the PVB.
The heating
element has normal (low) and high heat grids. Both grids share a common ground.
When the windshield is being heated in the NORMAL
mode, both grids are heating
the windshield. In the HI mode, only the outer grid
is heating the outer two thirds of the windshield. Heating a smaller portion
of the glass applies the electric heat to
a more concentrated area of
the windshield which is more
effective in heavier icing conditions. Electric connections
to the system are provided by terminal blocks
bonded to the inner ply
of the glass along the bottom.
Each terminal is lettered with the first initial
of its function as follows:
• HP
for high power
• LP
for low power (normal)
• Two Ss for sensor
Normal Heat
Each system power is
provided through a 50-amp current limiter on the DC power panel and is routed to the normal (low)
heat relay. Power is then
routed through a 5-AMP CB to the wind-
shield anti-ice switch.
When the switch is placed in
the NORMAL (low) position,
power is applied to the controller, which applies potential to the sensor element in the windshield. The sensor is a thermistor that increases in resistance as it increases in temperature. If the temperature of the glass
is less than approximately
32°C
(90°F), the controller closes the low-heat
relay applying power
to the low side of the windshield
heating element. When the temperature of the glass reaches 32°C through 43°C (90°F through
110°F), the resistance of the sensor is great enough to cause the controller to remove power from the low-heat relay, which
removes
power from the heating element.
The controller cycles the low-heat
relay as necessary while the system is activated.
High Heat
When the windshield anti-ice switch is placed in the HI position, power is applied to close the high heat relay and also passes through a diode to the low side of the switch to the control- ler. The controller makes no distinction between NORMAL and HI. It cycles the low-heat relay the same in either mode. Although potential is applied to both the low- and the high-heat grids in the windshield, current only flows through the high-heat grid since its resistance is less than that of the low-heat grids.
WSHLD
ANTI-ICE Switches
The pilot and copilot WSHLD ANTI-ICE switches activate heating elements
in the wind- shields.
These switches have three positions
as follows:
• OFF—Deactivates the heating
elements.
• NORMAL—Activates
the
heating
elements to all of the windshield.
• HI—Activates the heating elements to the outer two thirds of the windshield.
FUEL ANTI-ICE
SYSTEMS
Fuel anti-icing is provided
by three independent systems.
Fuel Heater
Fuel flow to the engine passes through an oil-to- fuel heat exchanger to melt any ice crystals present in the fuel. The temperature of the fuel controls the oil flow to or around the heat exchanger so the fuel temperature is maintained at a nominal temperature of 21°C through 32°C (70°F to 90°F).
Fuel Vent Heaters
Right and left FUEL VENT
heat switches,
on the pilot inboard subpanel, control the resistive wire- wrapped heating elements
on the protruding fuel vents, on the bottom of the wings outboard of the nacelles. Power is supplied
through 5-AMP CBs placarded FUEL VENT.
P3 and Py Line Heaters
When a condition lever is moved
out of the cutoff position,
a microswitch
in the pedestal
(one for each engine) closes to
power
insulated wire-wrapped heating elements in the P3 to the
fuel control unit and to the Py line to the fuel top-
ping governor. Power
is supplied through 7.5-AMP CB placarded FUEL CONTROL HEAT.
ENGINE
AIR INLET ANTI-ICE
LJ-242 THROUGH LJ-1062,
LW-1 AND AFTER, LA-2
THROUGH LA-201 AND LA-203
AND LA-204
Each engine air inlet is equipped with an electrically heated
anti-ice boot to prevent ice formation on
the air intake.
Power for each boot is taken from individual 25- amp circuit breakers. When the control switch is turned on, a relay completes the circuit to each boot. Since the boots have a high heating capacity and damage will result if there is insufficient airflow over them, the relays are grounded through the right landing gear safety switch. With the struts compressed, the relay circuit is open, deenergizing the relay and opening the circuit to the boots.
LJ-76, LJ-114 THROUGH LJ-241
A control switch
on the subpanel just to
the right of the pilot’s control wheel, and a solenoid
valve, screen actuator, and two vanes
(one fixed and the other movable) on the lower
cowling of each engine comprise
the inertial anti-ice system. With the control
switch in its normally closed position, bleed air from the
engine is directed by
the solenoid valve into the
bottom of the actuator cylinder, thereby forcing the cylinder
up to retract the vane attached
to the end of the piston rod.
NOTE: On Serials LJ-125 and
LJ-170 through LJ-241 and on all airplanes equipped
with Kit 90-4015, the engine bleed air is routed through a dryer that
removes all moisture to prevent malfunction of the actuator valve through icing.
During icing conditions, the control switch is actu- ated to open the circuit. The solenoid valve then directs the bleed air into the top of the actuator cylinder, forcing the piston down and extending the vane. When in the extended position, the vane increases airflow velocity and forces the airstream to turn abruptly before entering the engine plenum. The air, unladen with ice or snow, enters the plenum around the trailing edge of the vane and through the screen adjacent to the vane. The heavy, ice-laden air is discharged overboard through the bypass duct over the oil cooler. The anti-icer vanes automatically extend upon the loss of electrical power.
Magnets attached to the vane actuate limit switches at the up and down stops when the vane reaches the extremity of its travel. During vane travel, the circuit is completed through the limit switches to fail indicator lights on the annunciator panel above the instrument panel. Should the vane fail to reach either stop, its respective light will continue to indicate mechanical failure.
LJ-242 AND AFTER, LW-1 AND AFTER
The system for each engine is controlled by a push-pull handle mounted on a bracket attached to the bottom of the subpanel directly under the pilot’s control column. A cable is routed from the control handle, along the leading edge of the wing, and up the RH side of the nacelle to the linkage that moves the vane. When the control handle is pushed in, the linkage attached to the vane is retracted against a spring stop to hold the vane in the up position for flight under normal conditions. When icing is encountered and the control handle is pulled out, the interconnecting cable rotates a torque tube to extend the movable vane, which is then locked in the down position when the attaching linkage passes overcenter. The extend vane causes the velocity of the incoming air to increase. While the lighter portion of the incoming air turns abruptly to enter the engine plenum around the trailing edge of the extended vane, that air which is laden with ice and snow rushes on past the entrance to the plenum and is discharged overboard through the bypass duct over the oil cooler.
|
PTP Beech 90 Series |
B1 |
LOC |
FOT |
SGH |
|
MEL |
TS |
|
B2 |
LOC |
FOT |
SGH |
|
MEL |
TS |
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