AD FAA-2012-0221

We are adopting a new airworthiness directive (AD) for a certain Spectrolab Nightsun XP Searchlight Assembly (searchlight) installed on, but not limited to Agusta S.p.A. (Agusta) Model AB139 and Model AW139 helicopters, Sikorsky Aircraft Corporation (Sikorsky) Model S-92A helicopters, and Eurocopter Deutschland GmbH (Eurocopter) Model EC135 and Model MBB-BK 117 C-2 helicopters. This AD requires, before further flight, inserting information into the Normal Procedures section of the Rotorcraft Flight Manual (RFM), a daily check of the searchlight, and at a specified time interval or if certain conditions are found, modifying any affected searchlight gimbal assembly. This AD was prompted by a report of a searchlight vibrating and an investigation that revealed that the gimbal azimuth top nut was loose. A loose nut, if not detected and corrected, could result in a gap between the rubber edging of the top shroud and the gimbal frame, leading to degradation of pointing accuracy and stability performance of the searchlight and excessive vibration. If the nut were to entirely disengage, the searchlight could disconnect partially or totally from the helicopter, resulting in damage to the helicopter and injury to persons on the ground. The actions of this AD are intended to ensure that the searchlight remains firmly attached to the helicopter.