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###### Department of Transportation

###### Federal Aviation Administration

          - 14 CFR Part 39
          - [Docket No. FAA-2012-0354; Directorate Identifier 2010-SW-104-AD]
          - RIN 2120-AA64

# AGENCY:

Federal Aviation Administration (FAA), DOT.

# ACTION:

Notice of proposed rulemaking (NPRM).

# SUMMARY:

We propose to adopt a new airworthiness directive (AD) for all Eurocopter France (EC) Model SA-365N, SA-365N1, SA-366G1, AS-365N2, AS 365 N3, EC 155B, and EC155B1 helicopters. This proposed AD was prompted by the discovery of a cracked main rotor mast nut. This condition, if not corrected, could lead to complete failure of the mast nut, resulting in failure of the rotor mast and loss of control of the helicopter. This proposed AD would require replacing the main rotor mast nut with an airworthy main rotor mast nut. We are proposing this AD to prevent failure of the main rotor mast and subsequent loss of control of the helicopter.

# DATES:

We must receive comments on this proposed AD by June 4, 2012.

# ADDRESSES:

You may send comments by any of the following methods:
      -  Federal eRulemaking Docket:                          Go to                          http://www.regulations.gov.                          Follow the online instructions for sending your comments electronically.                    
      -  Fax:                          202-493-2251.                    
      -  Mail:                          Send comments to the U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE., Washington, DC 20590-0001.                    
      -  Hand Delivery:                          Deliver to the “Mail” address between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.                    

*Examining the AD Docket:*                         You may examine the AD docket on the Internet at                         *http://www.regulations.gov*                         or in person at the Docket Operations Office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this proposed AD, the economic evaluation, any                               ( print page 20320)                            comments received, and other information. The street address for the Docket Operations Office (telephone 800-647-5527) is in the                         **ADDRESSES**                         section. Comments will be available in the AD docket shortly after receipt.                    

                        For service information identified in this proposed AD, contact American Eurocopter Corporation, 2701 N. Forum Drive, Grand Prairie, TX 75052, telephone (972) 641-0000 or (800) 232-0323, fax (972) 641-3775, or at                         *http://www.eurocopter.com/​techpub.*                         You may review a copy of the referenced service information at the FAA, Office of the Regional Counsel, Southwest Region, 2601 Meacham Blvd., Room 663, Fort Worth, Texas 76137.                    

# FOR FURTHER INFORMATION CONTACT:

                        Gary Roach, Aviation Safety Engineer, Regulations and Policy Group, Rotorcraft Directorate, FAA, 2601 Meacham Blvd., Fort Worth, TX 76137; telephone (817) 222-5110; email                         *gary.b.roach@faa.gov.*

# SUPPLEMENTARY INFORMATION:

## Comments Invited

We invite you to participate in this rulemaking by submitting written comments, data, or views. We also invite comments relating to the economic, environmental, energy, or federalism impacts that might result from adopting the proposals in this document. The most helpful comments reference a specific portion of the proposal, explain the reason for any recommended change, and include supporting data. To ensure the docket does not contain duplicate comments, commenters should send only one copy of written comments, or if comments are filed electronically, commenters should submit only one time.

We will file in the docket all comments that we receive, as well as a report summarizing each substantive public contact with FAA personnel concerning this proposed rulemaking. Before acting on this proposal, we will consider all comments we receive on or before the closing date for comments. We will consider comments filed after the comment period has closed if it is possible to do so without incurring expense or delay. We may change this proposal in light of the comments we receive.

## Discussion

The European Aviation Safety Agency (EASA), which is the Technical Agent for the Member States of the European Union, has issued AD No.: 2006-0368R1, dated December 2, 2010, and corrected December 8, 2010 (AD 2006-0368R1), to correct an unsafe condition for the EC Model SA 365 N, SA 365 N1, AS 365 N2, AS 365 N3, SA 366 G1, EC 155 B, and EC 155 B1 helicopters. EASA advises that a cracked (partially failed) main rotor mast nut was discovered during a complete overhaul of a main rotor mast. The start of the crack was related to circular scoring found in the nut threads. EASA states that this condition, if not corrected, “could lead to complete failure of the mast nut, possibly resulting in failure of the rotor mast and consequent loss of control of the helicopter.” To address this unsafe condition, EASA issued Emergency AD 2006-0368-E, dated December 6, 2006 (AD 2006-0368-E), to require repetitive inspections of the mast nut, and replacement of the nut if cracked. Since issuance of AD 2006-0368-E, EC has developed modification (MOD) 0762C42 to improve the strength of the mast nut by changing its material. Replacing mast nut part number (P/N) 360A31-1020-20 with mast nut P/N 365A31-2060-20 or 365A31-2060-21 (as applicable to helicopter type) “constitutes an optional terminating action” for the repetitive inspection requirements. For this reason, EASA issued AD 2006-0368R1 “to inform which helicopters remain subject to inspections and replacement requirements” of the AD.

## FAA's Determination

We are proposing this AD because we evaluated all known relevant information and determined that an unsafe condition exists and is likely to exist or develop on other products of these same type designs.

## Related Service Information

We reviewed EC Alert Service Bulletin (ASB) No. 62.00.23, Revision 1, for Model SA-365N, SA-365N1, AS-365N2, and AS 365 N3 helicopters; EC ASB 62.12, Revision 1, for Model SA-366G1 helicopters; and EC ASB 62A014, Revision 1, for Model EC 155B and EC155B1 helicopters, all dated Oct 27, 2010. The ASBs contain procedures for repetitively inspecting the mast nut for a crack or failure. The ASBs remove any helicopter with MOD 0762C42 incorporated from the applicability of the ASB. EASA classified this ASB as mandatory and issued AD 2006-0368R1 to ensure the continued airworthiness of these helicopters.

## Proposed AD Requirements

This proposed AD would require, for EC Model SA-365N, SA-365N1, SA366G1, AS-365N2, AS 365 N3, EC 155B, and EC155B1 helicopters, certificated in any category, with a mast nut P/N 360A31-1020-20 installed:
    - For EC Models SA-365N, SA-365N1, AS-365N2, and AS 365 N3, prior to accumulating 1,650 hours time-in-service (TIS) or within the next 50 hours TIS, whichever occurs later, remove mast nut P/N 360A31-1020-20 and replace with an airworthy mast nut of a different P/N.
    - For EC Model SA-366G1, prior to accumulating 990 hours TIS or within the next 30 hours TIS, whichever occurs later, remove mast nut P/N 360A31-1020-20 and replace with an airworthy mast nut of a different P/N.
    - For EC Models EC 155B and EC155B1, prior to accumulating 660 hours TIS or within the next 50 hours TIS, whichever occurs later, remove mast nut P/N 360A31-1020-20 and replace with an airworthy mast nut of a different P/N.

## Differences Between This Proposed AD and the EASA AD

The EASA AD allows for either inspecting the mast nut at regular intervals or replacing the mast nut, while the proposed AD requires replacing the mast nut. The EASA AD uses flight hours of the main rotor mast assembly, while the proposed AD uses TIS of the helicopter.

## Costs of Compliance

We estimate that this proposed AD affects 30 helicopters of U.S. registry. We estimate that replacing the mast nut with an airworthy mast nut would require 32 work-hours, at an average labor cost of $85 per work-hour. Parts would cost about $3,100. Based on these costs, we estimate a total cost per helicopter of $5,820, and a total cost for the U.S. operator fleet of $174,600.

## Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. “Subtitle VII: Aviation Programs,” describes in more detail the scope of the Agency's authority.

                    We are issuing this rulemaking under the authority described in “Subtitle VII, Part A, Subpart III, Section 44701: General requirements.” Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.                          ( print page 20321)    

## Regulatory Findings

We determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD would not have a substantial direct effect on the States, on the relationship between the national Government and the States, or on the distribution of power and responsibilities among the various levels of government.

For the reasons discussed, I certify this proposed regulation:

1. Is not a “significant regulatory action” under Executive Order 12866;

2. Is not a “significant rule” under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979);

3. Will not affect intrastate aviation in Alaska to the extent that it justifies making a regulatory distinction; and

4. Will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act.

We prepared an economic evaluation of the estimated costs to comply with this proposed AD and placed it in the AD docket.

# List of Subjects in 14 CFR Part 39

      - Air transportation
      - Aircraft
      - Aviation safety
      - Incorporation by reference
      - Safety

## The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 14 CFR part 39 as follows:

# PART 39—AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

Authority:49 U.S.C. 106(g), 40113, 44701.

§ 39.13 

2. The FAA amends § 39.13 by adding the following new Airworthiness Directive (AD):

**Eurocopter France:**                                 Docket No. FAA-2012-0354; Directorate Identifier 2010-SW-104-AD.                            

##  (a) Applicability

This AD applies to Eurocopter France (EC) Model SA-365N, SA-365N1, SA-366G1, AS-365N2, AS 365 N3, EC 155B, and EC155B1 helicopters with a mast nut, part number (P/N) 360A31-1020-20, installed.

## (b) Unsafe Condition

This AD describes the unsafe condition as a cracked main rotor mast nut. This condition could result in failure of the rotor mast and subsequent loss of control of the helicopter.

## (c) Compliance

You are responsible for performing each action required by this AD within the specified compliance time unless it has already been accomplished prior to that time.

## (d) Required Actions

(1) For EC Models SA-365N, SA-365N1, AS-365N2, and AS 365 N3, prior to accumulating 1,650 hours time-in-service (TIS) or within the next 50 hours TIS, whichever occurs later, remove mast nut P/N 360A31-1020-20 and replace with an airworthy mast nut that has a P/N other than P/N 360A31-1020-20.

(2) For EC Model SA-366G1, prior to accumulating 990 hours TIS or within the next 30 hours TIS, whichever occurs later, remove mast nut P/N 360A31-1020-20 and replace with an airworthy mast nut that has a P/N other than P/N 360A31-1020-20.

(3) For EC Models EC 155B and EC155B1, prior to accumulating 660 hours TIS or within the next 50 hours TIS, whichever occurs later, remove mast nut P/N 360A31-1020-20 and replace with an airworthy mast nut that has a P/N other than P/N 360A31-1020-20.

## (e) Alternative Methods of Compliance (AMOC)

                                (1) The Manager, Safety Management Group, FAA, may approve AMOCs for this AD. Send your proposal to: Gary Roach, Aviation Safety Engineer, Regulations and Policy Group, Rotorcraft Directorate, FAA, 2601 Meacham Blvd., Fort Worth, TX 76137; telephone (817) 222-5110; email                                 *gary.b.roach@faa.gov.*

(2) For operations conducted under a Part 119 operating certificate or under Part 91, Subpart K, we suggest that you notify your principal inspector, or lacking a principal inspector, the manager of the local flight standards district office or certificate holding district office before operating any aircraft complying with this AD through an AMOC.

## (f) Additional Information

                                (1) Eurocopter Alert Service Bulletin No. 62.00.23, No. 62.12, and No. 62A014, which are not incorporated by reference, contain additional information about the subject of this AD. All of the service bulletins are Revision 1 and all are dated Oct 27, 2010. For service information identified in this AD, contact American Eurocopter Corporation, 2701 N. Forum Drive, Grand Prairie, TX 75052, telephone (972) 641-0000 or (800) 232-0323, fax (972) 641-3775, or at                                 *http://www.eurocopter.com/​techpub.*                                 You may review copies of the service information at the FAA, Office of the Regional Counsel, Southwest Region, 2601 Meacham Blvd., Room 663, Fort Worth, Texas 76137.                            

(2) The subject of this AD is addressed in in European Aviation Safety Agency AD No.: 2006-0368R1, dated December 2, 2010, and corrected December 8, 2010.

## (g) Subject

Joint Aircraft Service Component (JASC) Code: 6300, main rotor drive system.

Issued in Fort Worth, Texas, on March 26, 2012.

Scott A. Horn,

Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.

[FR Doc. 2012-8056 Filed 4-3-12; 8:45 am]

BILLING CODE 4910-13-P