The heating elements protect the stall warning lift transducer vane and face plate from ice. How-
ever, a buildup of ice on the wing may change or disrupt the airlow and prevent the system from
accurately indicating an imminent stall.
2-60. STALL WARNING HEAT SYSTEM.
The lift transducer is equipped with anti-icing capability on both the mounting plate and the vane. A switch located
on the overhead control panel placarded STALL WARN controls the heat. The level of heat is minimal for ground
operation but is automatically increased for light operation through the landing gear safety switch. Circuit protection
is provided by a 15-ampere circuit breaker, placarded STALL WARN , on the overhead circuit breaker panel (Fig.
2-61. STALL WARNING SYSTEM.
The stall warning system consists of a transducer, a lift computer, a warning horn, and a test switch. Angle of attack
is sensed by aerodynamic pressure on the lift transducer vane located on the left wing leading edge. When a stall
is imminent, the output of the transducer activates a stall warning horn. The system has prelight test capability
through the use of a switch placarded STALL WARN TEST OFF LDG GEAR WARN TEST on the right subpanel.
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 , on the overhead circuit breaker panel
2-62. BRAKE DEICE SYSTEM.
a. Description. The heated air brake deice system may be used in light with gear retracted or extended, or on
the ground. When 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 irst
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 light through
icing conditions with wet brake assemblies 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 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.
b. Operation. The switch in the overhead control panel, placarded BRAKE - ON , controls the solenoid valve
by routing power through a control module box under the aisle way loorboards. The system is protected by the
5-ampere circuit breaker on the overhead circuit breaker panel (Fig. 2-12) placarded BRAKE DEICE. A 10-minute
timer limits operation and avoids 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
(1) The L BL AIR FAIL or R BL AIR FAIL annunciator may momentarily illuminate during simultaneous
operation of the surface and brake deice systems at low N 1 speeds. If the annunciators immediately extinguish,
they may be disregarded.
(2) During certain ambient conditions, use of the brake deice system may reduce available engine power,
and during light will result in a TGT rise of approximately 20° C. Applicable performance charts should be con-
sulted before brake deice system use. If speciied 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 15° C ambient temperature.
During periods of simultaneous brake deice and surface deice operation, maintain 85% N 1 or higher. If inadequate
pneumatic pressure is developed for proper surface deice boot inlation, 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