composite inner beam to strengthen the structure of an aircraft

A beam for reinforcing the structure of an aircraft is located inside the fuselage of the aircraft. The fuselage includes at least one pressurized zone (P) that is separated by at least one airtight wall (18) of at least one other non-pressurized zone (16), the beam and the at least one airtight wall being intersecting. The beam traverses the at least one airtight wall (18) that includes a cutaway that is adapted to the section of the beam, whereby sealing elements (30) are provided to ensure the sealing between the beam and the airtight wall (18) that is traversed.