Summary
This document proposes to revise an existing airworthiness directive (AD), applicable to Aerospatiale (Societe Nationale Industrielle Aerospatiale) (SNIAS) (now known as Eurocopter France) Model AS 350 and AS 355 series helicopters that currently requires repetitive inspections of the main rotor head components, the main gearbox (MGB) suspension bars, and the ground resonance prevention system components at intervals not to exceed 400 hours time-in-service (TIS). This action would require the same inspections, but at intervals not to exceed 500 hours TIS. This proposal is prompted by reports of confusion and unnecessary costs associated with the difference in the current 400 hours TIS inspection interval and the current manufacturer's master service recommendation of 500 hours TIS inspection interval. The actions specified by the proposed AD are intended to eliminate confusion and unnecessary costs and to prevent ground resonance due to reduced structural stiffness, which could lead to failure of a main rotor head or MGB suspension component and subsequent loss of control of the helicopter.