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Environmental System Squawks

July 2009

As summer temperatures rise, so do the number of environmental system squawks. For all aircraft that have an air cycle machine, the discomfort of passengers and crew become more evident as the airflow and temperature are reduced.

Airflow reduction is simple. Hot air is being diverted to the cooling packs and cooling air requires more energy. As this natural energy drain occurs, leaks, cooling turbine, intercoolers, regulators and air supply sources are now more prone to show their deficiencies if they are not up to specification.

When troubleshooting this squawk, do not change the cooling turbine unless it is locked up and all other sources have been ruled out. A cooling turbine with higher torque than specified is not ideal; however in my experience it is typically not the primary problem.