Assembly for a heat engine air circuit

An assembly for a heat engine air circuit, comprising:

• a first pipe able to convey fluid;
• a second pipe extending between an inlet in the first pipe and an outlet in the first pipe, to form a bypass for a portion of the first pipe, the second pipe comprising a pressure variation source;
• a switching flap for the fluid in one of the second pipe and said portion of the first pipe, the switching flap being movable between:
• a first position allowing the fluid to circulate predominantly in the portion of the first pipe, and
• a second position allowing the fluid to circulate predominantly in the second pipe;
• and
• a maintaining member exerting a torque configured to bring or keep the switching flap in the first position,
• the flap going from the first to the second position when the pressure variation generated in the second pipe by the source exceeds a predefined value, this pressure variation then exerting a torque on the switching flap allowing this change to the second position, despite the torque exerted by the maintaining member,
• the wall of the second pipe at the switching flap and the switching flap being configured to define a passage section for the fluid circulating in the second pipe, said section increasing as soon as possible when said flap reaches a third position which closes off said portion of the first pipe.