STUDENT GUIDE FOR T-1A AIRCRAFT SYSTEMS
803. WING LEADING EDGE ANTI-ICE SYSTEM
The leading edges of the wings are protected from ice formation by engine bleed air. The engine
bleed air is pressure regulated at 38-44 psi and mixed with ambient air for distribution to an air
duct formed by the double walls of the leading edge of the wing.
Controls and Indicators
Overtemperature Switches - Three overtemperature switches are installed in each wing to
monitor the bleed air temperature, and illuminate a wing overheat annunciator when excessive
temperatures are sensed. One overtemperature switch closes at approximately 350° F, and two
overtemperature switches close at approximately 212° F. When any of the overtemperature
switches close, the red warning annunciator on the main annunciator panel illuminates the letters
WING OV HT.
804. HORIZONTAL STABILIZER ANTI-ICE SYSTEM
The ice protection system for the horizontal stabilizer is comprised of electrical heating elements
molded into heating mats on the leading edges of the horizontal stabilizer, the gap between the
elevator and the stabilizer, and the elevator horns. A temperature sensor and an overheat sensor
are installed in the left horizontal stabilizer heater mat.
Anti-Ice Switch and Operation
With the switch in the ON position and the aircraft airborne, a temperature controller
automatically controls the heater elements on the stabilizer leading edge and tip of the elevator
horn. When the temperature of the horizontal stabilizer leading edge drops below 260° F, power
is automatically initiated. When the temperature sensor detects a maximum temperature of
280° F, the power is interrupted. The system will continue to cycle on and off until the switch is
placed in the OFF position.
Anti-Ice System Failure
If the overtemperature sensor detects an overheat temperature of 310° F, the temperature
controller interrupts electrical power to the heating elements. The STB ANTI-ICE FAIL light on
the main annunciator panel will illuminate.
Deice Switch and Operation
With the switch in the ON position, the deice timer receives signal through the right landing gear
safety switch (only when the aircraft is airborne). The heater mats on the stabilizer leading edge,
the elevator horn, and the gap between the elevator and the stabilizer are powered in a cycle of
12 steps (one for each zone in the mats). After the cycle is completed, the sequence repeats. The
full cycle requires approximately three and a half minutes.
8-2 ANTI-ICE AND DEFOG SYSTEMS