An engine of an aircraft; the engine comprises: a tubular housing having a tubular lateral wall without openings and one single air intake opening, which is arranged at the front in the area of a front base perpendicular to the lateral wall and through which the engine takes in the external air needed to operate; at least one air filter, which has a tubular shape having a cylindrical symmetry, is completely arranged inside the tubular housing, and is narrower than the tubular housing, so that a lateral wall of the air filter is at a given distance other than zero from the lateral wall of the tubular housing; and a separation wall, which is completely arranged inside the tubular housing in the area of an intermediate portion of the tubular housing, is oriented perpendicularly to the lateral wall of the tubular housing, provides a support for a base of the air filter, divides the inside of the tubular housing into a front intake chamber containing the air filter and a rear propulsion chamber, and has a first passageway through opening, which establishes a pneumatic communication on the inside of the air filter with the rear propulsion chamber; the engine is characterized in that: the separation wall comprises at least one second passageway through opening, which is arranged on the outside of the air filter in an annular area of the separation wall extending from the lateral wall of the air filter to the lateral wall of the tubular housing and directly establishes a pneumatic communication between the intake chamber and the propulsion chamber without going thorough the air filter; at least one shutter element is provided, which is mounted so as to be movable between an opening position, in which the shutter element allows air to flow through the second passageway opening, and a closed position, in which the shutter element prevents air from flowing through the second passageway opening; and an actuator is provided, which moves the shutter element between the opening position and the closing position. a tubular housing having a tubular lateral wall without openings and one single air intake opening, which is arranged at the front in the area of a front base perpendicular to the lateral wall and through which the engine takes in the external air needed to operate; at least one air filter, which has a tubular shape having a cylindrical symmetry, is completely arranged inside the tubular housing, and is narrower than the tubular housing, so that a lateral wall of the air filter is at a given distance other than zero from the lateral wall of the tubular housing; and a separation wall, which is completely arranged inside the tubular housing in the area of an intermediate portion of the tubular housing, is oriented perpendicularly to the lateral wall of the tubular housing, provides a support for a base of the air filter, divides the inside of the tubular housing into a front intake chamber containing the air filter and a rear propulsion chamber, and has a first passageway through opening, which establishes a pneumatic communication on the inside of the air filter with the rear propulsion chamber; the engine is characterized in that: the separation wall comprises at least one second passageway through opening, which is arranged on the outside of the air filter in an annular area of the separation wall extending from the lateral wall of the air filter to the lateral wall of the tubular housing and directly establishes a pneumatic communication between the intake chamber and the propulsion chamber without going thorough the air filter; at least one shutter element is provided, which is mounted so as to be movable between an opening position, in which the shutter element allows air to flow through the second passageway opening, and a closed position, in which the shutter element prevents air from flowing through the second passageway opening; and an actuator is provided, which moves the shutter element between the opening position and the closing position. the separation wall comprises at least one second passageway through opening, which is arranged on the outside of the air filter in an annular area of the separation wall extending from the lateral wall of the air filter to the lateral wall of the tubular housing and directly establishes a pneumatic communication between the intake chamber and the propulsion chamber without going thorough the air filter; at least one shutter element is provided, which is mounted so as to be movable between an opening position, in which the shutter element allows air to flow through the second passageway opening, and a closed position, in which the shutter element prevents air from flowing through the second passageway opening; and an actuator is provided, which moves the shutter element between the opening position and the closing position.