EASA 2019-0199

Requires a one-time inspection of titanium bolts with P/N L535M2001203 installed on the forward tail rotor drive shaft and, depending on findings, replacement. This AD also prohibits installation or reinstallation of these bolts. Prompted by an occurrence reported of a broken titanium bolt on a helicopter. Subsequent investigation results determined that an improper heat treatment process was accomplished on a certain batch of bolts, which can lead to hydrogen embrittlement.