Double-shell lightning protection cap with improved assembly

A lightning protection cap for sealing an attachment element attached to the structure of an aircraft, the lightning protection cap comprising:

• an inner shell defining an interior volume for receiving the attachment element and an outer shell configured to cover the inner shell, the inner and outer shells comprising complementary first and second attachment means configured for cooperating to enable engagement of the outer shell on the inner shell;
• wherein one of the inner shell or the outer shell comprises the second attachment means, said second attachment means comprising at least one lug;
• and
• wherein the other of the inner shell and the outer shell comprises the first attachment means, including a ramp and a protuberance separated from the ramp to form a housing between the ramp and the protuberance, said ramp, said housing and said protuberance being circumferentially and consecutively arranged with said housing intermediate said ramp and said protuberance, said ramp being configured to allow the lug to slide until reaching the housing when the outer shell is rotated relative to the inner shell, in order for the housing to angularly lock the outer shell relative to the inner shell.