Wing Leading Edge Anti-ice System

CHAPTER EIGHT

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