from the temperature sensor and the temperature selector and supplies open and close signals, as appropriate, to the vent suit temperature control valve. The vent-air flow controllers, as the name implies, control the flow of air from the vent-air system ducting to the personnel services dis- connects and the seat cushion or the vent connection of the antiexposure suit. One controller is provided for each crew member. The controller has an inlet connector, an outlet connector, and a thumbwheel-operated flow controller. The thumbwheel shaft connects to a rotating plug, which gradually opens or closes off the outlet port as it rotates up to a maximum of 180 degrees. The flow controller will be fully open when turned to the full counterclockwise position. The temperature selector is a thumbwheel- operated potentiometer, located on the pilot’s console, aft of the flow controller thumbwheel. One temperature selector serves both vent suit outlets. The thumbwheel is numbered 1 through 14, and the console is labeled HOT and COLD. Turning the thumbwheel clockwise to the lower numbered settings lowers the temperature of vent- air system air. Counterclockwise movement towards the hot position and the higher numbered settings increases the temperature. Response to temperature changes initiated by repositioning the temperature selector thumb- wheel will be noticeable at the disconnect outlet within a few seconds after making a selection change. When the aircraft is in a stabilized flight condition (maintaining a steady altitude), the temperature of vent air will be monitored and controlled within a ±2°F tolerance of the temperature selected by the temperature selector thumbwheel. When the aircraft is changing altitude, the temperature is maintained within a ± 10°F tolerance. The thermal switch senses any abnormally high temperatures not compensated for by the temperature sensor and will provide a signal, via the cabin and vent suit temperature controller, to the temperature control valve to drive it towards the closed position. The system pressure relief valve protects the system from accidental overpressurization. The relief valve will open as necessary to prevent vent- air system ducting pressure from exceeding 10 psi. The check valve prevents conditioned air from backing up into the environmental control system ducting. Cooled air flows through the check valve, is mixed with the appropriate amount of hot bleed air, and is forced into the vent-air system ducting. DEICE/ANTI-ICING SYSTEMS On days when there is visible moisture in the air, ice can form on aircraft leading edge surfaces at altitudes where freezing temperatures start. Water droplets in the air can be supercooled to below freezing without actually turning into ice unless they are disturbed in some manner. This unusual occurrence is partly due to the surface tension of the water droplet not allowing the droplet to expand and freeze. However, when air- craft surfaces disturb these droplets, they immediately turn to ice on the aircraft surfaces. The ice may have a glazed or rime appearance. Glazed ice is smooth and hard to detect visually. Rime ice is rough and easily noticed. Frost is formed as a result of water vapor being turned directly into a solid. Frost can form on aircraft surfaces in two ways. First, it can accumulate on aircraft parked in the open over- night when the temperature drops below freezing and proper humidity conditions exist. Second, it can form on aircraft surfaces, caused by flying at very cold altitudes and descending rapidly into warm, moist air. In this case, frost deposits will result before the structure warms up because of the marked cooling of air adjacent to the cold skin. Ice or frost forming on aircraft create two basic hazards: (1) the resulting malformation of the airfoil, which could decrease the amount of lift; and (2) the additional weight and unequal formation of the ice, which could cause un- balancing of the aircraft, making it hard to control. Enough ice to cause an unsafe flight condition can form in a very short period of time, thus some method of ice prevention or removal is necessary. Presently there are two methods for removing or preventing ice. One method, deicing, employs a mechanical system to break up and remove the ice after it has formed. The second method, anti- icing, uses heated bleed air to prevent the formation of ice. Deicing systems are common to older aircraft, and are now generally being replaced by anti-icing systems. Deice Boot Systems The deice system for the wing, horizontal, and vertical stabilizer leading edges of E-2 aircraft is an example of a typical deice boot system. The system removes accumulated ice from the wing surfaces through the use of rubber deice boots, which are bonded to the leading edges. The cells 1-7