Holding this switch in the STALL WARN TEST position
actuates the warning horn by moving the transducer
vane. The circuit is protected by the 5-ampere circuit
breaker, placarded STALL, located on the overhead
circuit breaker panel (fig. 2-9).
2-57. BRAKE DEICE SYSTEM.
Description. The brake deice system may be
used in flight with gear retracted or extended, or on the
ground. When the brake deice system is activated, hot
air is diffused by means of a manifold assembly over the
brake discs on each wheel. Manual and automatic
controls are provided. There are two primary occasions
which require brake deicing. The first is when an aircraft
has been parked in a freezing atmosphere, allowing the
brake systems to become contaminated by freezing rain,
snow, or ice, and the aircraft must be moved or taxied.
The second occasion is during flight through icing
conditions, when brake assemblies which are presumed
to be frozen, which must be thawed prior to landing to
avoid possible tire damage and loss of directional
control. Hot air for the brake deice system comes from
the compressor stage of both engines. Hot air is
obtained by means of a solenoid valve attached to the
bleed air system which serves both the surface deice
system and the pneumatic systems operation.
Operation. A switch located on the overhead
control panel (fig. 2-15), placarded BRAKE - ON,
controls the solenoid valve by routing power through a
control module box under the aisle way floorboards. The
system is protected by a 5-ampere circuit breaker on the
overhead circuit breaker panel (fig. 2-9), placarded
BRAKE DE-ICE. A 10-minute timer limits operation to
avoid excessive wheel well temperatures when the
landing gear is retracted. The control module also
contains a circuit to the green BRAKE DEICE ON
annunciator, and has a resetting circuit interlocked with
the gear uplock switch. When the system is activated,
the BRAKE DEICE ON annunciator should be monitored
and the control switch selected off after the annunciator
extinguishes, otherwise, on the next gear extension, the
system will restart without pilot action. The control
switch should also be selected off if deice operation fails
to self-terminate after approximately 10 minutes. If the
automatic timer has terminated brake deice operation
after the last retraction of the landing gear, the landing
gear must be extended in order to obtain further
operation of the system.
The L BL AIR FAIL or R BL AIR FAIL
simultaneous operation of the surface and brake deice
systems at low N1 speeds. If the annunciators
immediately extinguish, they may be disregarded.
During certain ambient conditions, use of
the brake deice system may reduce available engine
power, and during flight will result in a TGT rise of
approximately 20C. Applicable performance charts
should be consulted before brake deice system use. If
specified power cannot be obtained without exceeding
limits, the brake deice system must be selected off until
after takeoff is completed. TGT limitations must also be
observed when setting climb and cruise power. The
brake deice system is not to be operated above 15C
ambient temperature. During periods of simultaneous
brake deice and surface deice operation, maintain 85%
N1 or higher. If inadequate pneumatic pressure is
developed for proper surface deice boot inflation, select
the brake deice system off. Both sources of pneumatic
bleed air must be in operation during brake deice system
use. Select the brake deice system off during single
2-58. FUEL SYSTEM ANTI-ICING.
Description. An oil-to-fuel heat exchanger,
located in each engine accessory case, operates
sufficiently to prevent freezing of any water in the fuel.
No controls are involved. Three external fuel vents are
provided on each wing. One is recessed to prevent ice
formation, the second is flush mounted so that no ice
can collect upon it, and the third is electrically heated.
Heating is controlled by two toggle switches located on
the overhead control panel, placarded FUEL VENT,
LEFT, RIGHT and ON (fig. 2-15). They are protected by
two 5-ampere circuit breakers, placarded FUEL VENT
HEAT, LEFT, and RIGHT, located on the overhead
circuit breaker panel (fig. 2-9).
To prevent overheat damage to electrically
heated anti-ice jackets, the FUEL VENT heat
switches should not be turned ON unless
cooling air will soon pass over the jackets.
Normal Operation. For normal operation,
switches for the fuel vent anti-ice circuits are turned ON
as required during the BEFORE TAKEOFF procedures.
2-59. WINDSHIELD ELECTROTHERMAL ANTI-ICE
Description. Both the pilot's and copilot's
windshields are provided with an electrothermal anti-ice
system. Each windshield is part of an independent
electrothermal anti-ice system. Each system is
comprised of the windshield assembly with heating wires
sandwiched between glass panels, a temperature