Airworthiness Directives; Turbomeca Arriel 1B, 1D, and 1D1 Turboshaft Engines

This AD is being issued to detect and prevent perforation of the 2nd stage nozzle guide vanes (NGV2) that could cause fracture of a turbine blade that could result in an uncommanded engine in-flight shutdown on a single-engine helicopter.


   EFFECTIVE DATE: This AD becomes effective April 27, 2006. The Director of the Federal Register approved the incorporation by reference of certain publications listed in the regulations as of April 27, 2006.

   ADDRESSES: You can get the service information identified in this AD from Turbomeca, 40220 Tarnos, France; telephone 33 05 59 74 40 00, fax 33 05 59 74 45 15.

   You may examine the AD docket on the Internet at http://dms.dot.gov or in Room PL-401 on the plaza level of the Nassif Building, 400 Seventh Street, SW., Washington, DC.

   FOR FURTHER INFORMATION CONTACT: Christopher Spinney, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803; telephone (781) 238-7175; fax (781) 238-7199.

   SUPPLEMENTARY INFORMATION: The FAA proposed to amend 14 CFR part 39 with a proposed airworthiness directive (AD). The proposed AD applies to Turbomeca Arriel 1B, 1D, and 1D1 turboshaft engines. We published the proposed AD in the Federal Register on November 4, 2005 (70 FR 67099). That action proposed to require inspecting the NGV2 for wall thickness.

Examining the AD Docket

   You may examine the docket that contains the AD, any comments received, and any final disposition in person at the Docket Management Facility Docket Office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Office (telephone (800) 647-5227) is located on the plaza level of the Department of Transportation Nassif Building at the street address stated in ADDRESSES. Comments will be available in the AD docket shortly after the DMS receives them.

Comments

   We provided the public the opportunity to participate in the development of this AD. We have considered the comment received.

Request To Include an End Date

   One commenter requests that we include an end date in the AD, of December 31, 2006. This end date would help manage the risk of failure, while causing the least amount of disruption in the form of helicopter grounding.

   We agree. We changed compliance paragraph (e) to read "You are responsible for having the actions required by this AD performed at the next shop visit or the next accessibility of the NGV2 after the effective date of this AD, whichever occurs first, but no later than December 31, 2006, unless the actions have already been done."

Clarification of Unsafe Condition

   For clarification that the AD is applicable to only single-engine installations, we changed the unsafe condition in the AD to read "We are issuing this AD to detect and prevent perforation of the 2nd stage nozzle guide vanes (NGV2) that could cause fracture of a turbine blade that could result in an uncommanded engine in-flight shutdown on a single-engine helicopter."

Conclusion

   We have carefully reviewed the available data, including the comment received, and determined that air safety and the public interest require adopting the AD with the changes described previously. We have determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.

Costs of Compliance

   We estimate that this AD will affect 571 engines installed on helicopters of U.S. registry. We also estimate that it will take about 0.5 work hours per engine to perform the actions, and that the average labor rate is $65 per work hour. No parts are required. Based on these figures, we estimate the total cost of the AD to U.S. operators to be $18,558.

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