AD/BELL 412/40 Amdt 1 - Main Rotor Yoke (Cth)

AIRWORTHINESS DIRECTIVE On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/BELL 412/40 and issues the following AD under subregulation 39.001(1) of CASR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.

Bell Helicopter Textron 412 Series Helicopters AD/BELL 412/40 Amdt 1 Main Rotor Yoke 3/2006

Applicability: Model 412 and 412EP helicopters, serial numbers 33001 through 33213, 34001 through 34036 and 36001 through 36204; and Model 412CF helicopters, serial numbers 46400 through 46499; and All Model AB 412 helicopters: equipped with a main rotor yoke assembly part number 412-010-101-123 or -127. Requirement: Action in accordance with Bell Helicopter Textron Alert Service Bulletins No. 412-98-93, or No. 412CF-98-5, or Agusta Alert Technical Bulletin No. 412-74, as applicable.

Note: FAA AD 99-23-23 and ENAC AD 1999-179 refer. Compliance: As specified in the Requirement documents, as applicable. This Amendment becomes effective on 16 March 2006. Background: The manufacturer determined that main rotor yokes which measured less than 0.478" across a specific portion of the flexure area, does not have a sufficient fatigue margin of safety and have therefore reduced the life by 500 hours time in service.