Emergency Airworthiness Directive: ATA 55 – Stabilizers – Horizontal Stabilizer Attachment Bolts – Inspection/Modification/Clearance Check (link)
During a daily inspection of an EC175 B helicopter, a gap was noticed between the horizontal stabilizer and its fitting. The subsequent torque check revealed the loss of torque of one of the nuts. After removal of the affected nut, the observed clearance was found to be above the maximum allowable value of 0.1 millimetres (mm). During a daily inspection of another helicopter, one of the two horizontal stabilizer attachment bolts was found to be protruding from its seat. At a closer inspection, the bolt was found broken in its threaded section and kept in place by the sealant.
These conditions, if not detected and corrected, could lead to the in-flight loss of the horizontal stabiliser, possibly resulting in loss of control of the helicopter.
Source: CAA/EASA.