Auxiliary power unit inlet assembly with particle separator

An auxiliary power unit assembly for an aircraft, comprising:

• an internal combustion engine received in a compartment;
• a particle separator configured to remove particles from a flow;
• an inlet assembly including:
• a first inlet fluidly communicating between an environment of the aircraft and the internal combustion engine via a particle separator when the inlet assembly is in a first configuration and fluidly communicating between the environment and the compartment via the particle separator when the inlet assembly is in the first configuration;
• a second inlet fluidly communicating between the environment and the engine independently of the particle separator when the inlet assembly is in a second configuration and fluidly communicating between the environment and the compartment when the inlet assembly is in the second configuration;
• a member selectively positionable to substantially block communication between the second inlet and the engine when the inlet assembly is in the first configuration;
• wherein the first and second inlets communicate with the internal combustion engine through a filter and with the compartment independently of the filter.

A method of feeding air to an auxiliary power unit assembly of an aircraft, the method comprising:

• in a contaminated environment, circulating air from the environment of the aircraft via a first inlet on an exterior skin of the aircraft into a plenum through a particle separator to remove particles from the air;
• in a clean environment, circulating air from the environment of the aircraft via a second inlet on the exterior skin into the plenum at least in part without circulating through the particle separator;
• and
• in the contaminated and clean environments, circulating a first portion of the air from the plenum to an inlet of an internal combustion engine of the auxiliary power unit assembly through a filter and a second portion of the air from the plenum to a compartment containing the internal combustion engine independently of the filter;
• wherein, in the contaminated environment, the method further comprises positioning a door in a closed position to substantially block communication between the second inlet and the internal combustion engine.