A hat-stringer assembly (100) for an aircraft (500) comprises a hat stringer (110) with a first hat-stringer leg (140), a second hat-stringer leg (150), a first hat-stringer sidewall (114), a connecting wall (112), a second hat-stringer sidewall (116), and a ventilation opening (128), extending through the connecting wall (112). The hat stringer assembly (100) also comprises a fitting (200), comprising a first channel member (210) in contact with the first hat-stringer sidewall (114) and the first hat-stringer leg (140). The fitting (200) also comprises a second channel member (240) in contact with the second hat-stringer sidewall (116) and the second hat-stringer leg (150). The fitting (200) further comprises a web cap (260), in contact with the first channel member (210) and the second channel member (240). The web cap (260) comprises a web-cap opening (262), which is in fluidic communication with the ventilation opening (128).