A compound engine assembly including a compressor, an engine core including at least one rotary internal combustion engine and having an inlet in fluid communication with an outlet of the compressor, a turbine section having an inlet in fluid communication with an outlet of the engine core and configured to compound power with the engine core, and an air conduit having at least one heat exchanger extending there across. An outer wall of the air conduit has a plurality of openings defined there through downstream of the heat exchanger(s), each selectively closable by a pivotable flap movable between a retracted position where the opening is obstructed and an extended position away from the opening. Each opening defines a fluid communication between the air conduit and the ambient air when the respective flap is in the extended position. A method of directing flow through a compound engine assembly is also discussed.
