|Details||AAIB Field investigation. The helicopter was operating in the Police role, hovering some 600 feet above houses in Cardiff, when it suffered a loss of yaw control and descended into the roof of a house. The tail rotor pitch change unit (PCU) had come apart some 20 flying hours/11 days after a new bearing had been installed in the PCU in accordance with Modification 076551 (Service Bulletin 65.00.15). This modification had not been implemented correctly due to inexperience of the associated maintenance personnel, lack of proper required equipment and appropriate manuals. The torque loadings for this installation have since been increased by the manufacturer, and the CAA now requires this modification to be carried out by an approved component overhaul workshop, as opposed to the line maintenance level. CAA Letter to Owners/Operators (LTO) No.2073 Revision A refers. See AAIB Bulletin 1/2001, ref: EW/C2000/04/05.
CAA Closure: The hazard is controlled by the actions stated above.|