Summary
This document proposes adopting a new airworthiness directive (AD) for Bell Helicopter Textron Canada (Bell) Model 407 helicopters. This proposal would require creating a component history card or equivalent record for each crosstube assembly, converting accumulated run-on landings to an accumulated Retirement Index Number (RIN) count, and establishing a maximum accumulated RIN for certain crosstube assemblies. This proposal is prompted by fatigue testing, analysis, and evaluation by the manufacturer that determined that run-on landings impose a high stress on landing gear or crosstubes and may cause cracking in the area above the skid tube saddle. The actions specified by this proposed AD are intended to prevent fatigue failure in a crosstube assembly due to excessive stress during run-on landings and subsequent loss of control of the helicopter.