Fan with dual action check valves

摘要

An assembly includes a selectively driven fan (46) and a bypass flow passage (149) for bypassing the fan (46). The bypass flow passage (149) communicates with a first check valve (50) to allow air to flow from the bypass flow passage (149) to a downstream location (48). A second check valve (60) allows air driven by the fan (46) to pass into a return passage and return to an inlet of the fan (46) in the event that the discharge pressure from the fan (46) overcomes a spring force associated with the second check valve (60). A heat exchanger pack (20) and an environmental control system (18) for use on an aircraft and a method are also disclosed.