Environmental Control System for Light Turbo Prop

Honeywell has developed a unique environmental control system (ECS) for light turbo-prop aircraft applications. The ECS consists of two integrated systems, an Air Cycle System (ACS) and a Vapor Cycle Cooling System (VCCS). A single controller interfaces with both systems, and provides control by monitoring temperatures within the environment. The valves and fans of the ECS are then adjusted to provide the necessary control to minimise the error between the actual and set temperatures. The controller specifically provides the following functions:

• ACS control when selected on by the pilot
• VCCS control when selected on by the pilot
• Automatic ACS or VCCS control when selected by the pilot
• System self test

The compressor used in the VCCS is a new generation compressor:

• 28Vdc power supply current
• Hermetical compressor technology
• Brush-less DC motor
• Analogical driving speed

This paper will present the design of the hybrid ACS/VCCS environmental control system and notably its unique characteristics - the compressor and control system.