AD/Bell 412/57 Main Rotor Yoke (Cth)
AIRWORTHINESS DIRECTIVE
For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (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 412/57 | Main Rotor Yoke | 5/2009 DM |
Applicability: | Model 412 and 412EP helicopters with a main rotor yoke part number Model 412CF helicopters with a main rotor yoke part number 412-010-101-127, or |
Requirement: | 1. Review the helicopter records to determine all of the helicopter models on which the affected yoke has been installed since its production, and the accumulated hours time in service of each affected yoke. 2. If an affected part numbered yoke is installed or has ever been installed on a Model 412CF helicopter or on a Model 412 or 412EP helicopter with a a. Re-identify the part number on the existing yoke data plate by using a vibrating stylus and etching two lines through the last three digits of the existing part number, and etching “137FM” adjacent to where last three digits were etched through the original part number. This action converts each affected yoke part number to a new yoke part number 412-010-101-137FM. The serial number remains the same. b. Record the re-identified part number on the applicable component history card or equivalent record. Note 1: The “FM” part number suffix denotes a field modified part. 3. If it cannot be determined all of the model helicopters on which an affected yoke has been installed since its production or whether it has ever been installed on a Model 412 or 412EP helicopter with a (BHT-412-SI-62) slope landing kit, part number 412-704-012-101, installed, re-identify the yoke part number as part number as 412-010-101-137FM using a vibrating stylus in accordance with Requirement 2.a. of this Directive. Record the re-identified part number on the applicable component history card or equivalent record. |
| 4. For each identified yoke, part number 412-010-101-137FM, reduce the retirement life from 5,000 hours time in service to 4,500 hours time in service. Record the revised life limit on the applicable component history card or equivalent record. This Directive revises the Airworthiness Limitations section of the applicable maintenance manual or the Instructions for Continued Airworthiness (ICAs) by reducing the retirement life from 5,000 hours time in service to 4,500 hours time in service for each re-identified yoke, part number 412-010-101-137FM. Note 2: Bell Helicopter Textron Inc. Alert Service Bulletins No. 412-08-128 original issue and 412CF-08-35 original issue, or later FAA approved revisions, refer. Note 3: FAA AD 2009-05-09 Amdt 39-15833 refers. | |
Compliance: | Within 10 hours time in service after 31 March 2009, unless already accomplished. |
| This Airworthiness Directive becomes effective on 31 March 2009. | |
Background: | The FAA requires certain actions as a result of fatigue analysis which indicated that the retirement life should be reduced on certain yokes. The actions specified in this Directive are intended to prevent fatigue cracking of a yoke, failure of a yoke, and subsequent loss of control of the helicopter. |
David Villiers
Delegate of the Civil Aviation Safety Authority
17 March 2009
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