Method for the servo-installation of a threaded fastener

A method of installing a threaded fastener into a hole in a structure, the threaded fastener comprising a screw and a nut, the method comprising the following steps:

• a) inserting the screw into the hole, and screwing the nut onto the screw,
• b) simultaneously transmitting ultrasonic waves into the fastener and receiving reflected ultrasonic waves for the measurement of a first parameter representative of a variation in said waves, said first parameter providing an indirect measure of an axial tension in the screw,
• c) stopping the screwing when a target value for the first parameter is reached,
• characterized in that the process further comprises the following steps:
• d) determining the thickness of the structure to be tightened (L1), and
• e) determining the target value of the first parameter in accordance with the thickness of the structure to be tightened (L1) and a geometrical characteristics of the fastener (10).