Auxiliary power unit inlet assembly with filter

An auxiliary power unit assembly for an aircraft, comprising:

• an internal combustion engine;
• a duct in fluid communication with an inlet of the internal combustion engine, the duct configured to be in fluid communication with an environment of the aircraft;
• a filter received in and extending across the duct, the filter including:
• a first filter portion permeable to air, the first filter portion p extending from a side wall of the duct across only part of a span of the duct and defining a transverse edge in the duct,
• a second filter portion permeable to air extending in a downstream direction along the duct from the transverse edge to a downstream end located downstream of the transverse edge, the first and second filter portions being non-parallel, and
• a collection member impermeable to water extending from the downstream end across a remainder of the span of the duct, the second filter portion and the collection member being non-parallel.

A method of feeding air to an internal combustion engine of an auxiliary power unit assembly of an aircraft from a flow including the air and supercooled water droplets, the method comprising:

• circulating the flow in a duct in fluid communication with an inlet of the internal combustion engine;
• removing the supercooled water droplets from the flow by circulating the flow through a first filter portion extending across part of the duct, the supercooled water droplets being retained by the first filter portion;
• and
• upon ice formation from the supercooled water droplets on the first filter portion:
• diverting the flow with the iced first filter portion toward a wall of the duct and a space defined between the first filter portion and the wall;
• abruptly changing a direction of the air in the flow with the wall of the duct and with a collection member extending from the wall downstream of the first filter portion, the change of direction causing the supercooled water droplets to be retained by the wall and the collection member;
• and
• circulating the air through a second filter portion extending between the first filter portion and the collection member.