107: Aviation Life Support System (ALSS) / Utilities Fundamentals

107.1 Discuss the basic operation of an Air Cycle Air Conditioning system.

The air-conditioning system uses an air cycle refrigeration unit and supplies bleed air to provide heating and cooling. Bleed air entering the air cycle refrigeration unit passes through the heat exchanger and is cooled by a flow of ram air. The ram, air enters through the ram air scoop and the left side of fuselage, is circulated around the fins of the heat exchanger and than dumped overboard.

The cooled bleed air passes through the mass flow control valve and is ducted to the cooling turbine. Energy is extracted as the air expands and drives the turbine, resulting in further cooling of the air. The cooling turbine drives the ram air exhaust fan, which is mounted on a common shaft.

In other words, the engine bleed air is further compressed as it is passed to the cooling turbine. From there it is rapidly expanded, this rapid expansion is what cools the air.

A water separator in the system is used to extract entrained moisture from the refrigerated air discharged from the cooling turbine. Water is collected in a sump and drained overboard.

107.2 Discuss the basic operation of a Cabin Pressurization system.

The cabin pressurization control system consists of two outflow safety valves operated by an outflow control valve through two pneumatic relays. Pressurization starts when an altitude of 4000 feet is attained. Pressure in the aircraft is maintained until pressure differential of 6.5 psi exists the aircraft and the atmosphere. Cabin pressure is automatically dumped upon touchdown by the air /ground safety switch and NO.4 AIR/GND SAFETY RELAY.

107.3 Discuss the effects of ice accumulation on the aircraft. a. Increased liftoff speed and increased stalling speed b. Higher takeoff, landing, and minimum flight speeds than are normally required c. Reduced rate of climb d. Increased power requirements, thus causing increased fuel consumption and decreased range and endurance e. Reduced engine power caused by obstruction of the engine inlet air duct * The biggest danger caused by ice accumulation is the reduced aerodynamic efficiency of the aircraft. Increased drag and diminished lift because of lowered propeller efficiency and engine power are typical results.