[Docket No. FAA-2006-25970; Directorate Identifier 99-NE-12-AD] 

RIN 2120-AA64 

Airworthiness Directives; Turbomeca S.A. Turboshaft Engines 

AGENCY: Federal Aviation Administration (FAA), DOT. 

ACTION: Notice of proposed rulemaking (NPRM). 

SUMMARY: We propose to supersede airworthiness directive (AD) 2006-23-17, which 

applies to certain Turborneca S.A. Turmo IV A and IV C turboshaft engines. AD 2006-

23-17 currently requires repetitive inspections of the centrifugal compressor intake wheel 

(inducer) blades for cracks and corrosion, replacement of parts that fail inspection, and 

replacement of the TU 197 standard centrifugal compressor. This proposed AD would 

require the same inspections but at revised intervals, add the replacement of the TU 215 

standard centrifugal compressor, and require replacement of parts that fail inspection. We 

are proposing this AD to prevent failure of the centrifugal compressor inducer, which 

could lead to an uncontained blade release, damage to the engine, and damage to the 

airplane. 

DATES: We must receive comments on this proposed AD by [INSERT DATE 60 

DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER]. 

ADDRESSES: You may send comments, using the procedures found in 14 CFR 11.43 

and 11.45, by any of the following methods: 

• Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the 

instructions for submitting comments. 

• Fax: 202-493-2251. 
Monday through Friday, except Federal holidays. 

For service information identified in this proposed AD, contact Turbomeca S.A., 

40220 Tarnos, France; phone: 33 (0)5 59 74 40 00; fax: 33 (0)5 59 74 45 15. You may 

view this service information at the FAA, Engine & Propeller Directorate, 12 New 

England Executive Park, Burlington, MA. For infonnation on the availability of this 

material at the FAA, call 781-238-7125. 

Examining the AD Docket 

You may examine the AD docket on the Internet at http://www.regulations.gov by 

searching for and locating Docket No. F AA-2006-25970; or in person at the Docket 

Management Facility between 9 a.m. and 5 p.m., Monday through Friday, except Federal 

holidays. The AD docket contains this proposed AD, the regulatory evaluation, any 

comments received and other information. The street address for the Docket Office 

(phone: 800-647-5527) is in the ADDRESSES section. Comments will be available in the 

AD docket shortly after receipt. 

FOR FURTHER INFORMATION CONTACT: Wego Wang, Aerospace Engineer, 

Engine Certification Office, FAA, Engine & Propeller Directorate, 12 New England 

Executive Park, Burlington, MA 01803; phone: 781-238-7134; fax: 781-238-7199; email: 

wego.wang@faa.gov. 

SUPPLEMENTARY INFORMATION: 

Comments Invited 

We invite you to send any written relevant data, views, or arguments about this 

NPRM. Send your comments to an address listed under the ADDRESSES section. 

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comments. 

We will post all comments we receive, without change, to 

http://www.regulations.gov, including any personal information you provide. We will 

also post a report summarizing each substantive verbal contact we receive about this 

NPRM. 

Discussion 

On November 7, 2006, we issued AD 2006-23-17, Amendment 39-14829 (71 FR 

66664, November 16, 2006), ("AD 2006-23-17"), for all Turbomeca S.A. Turmo IV A 

and IV C turboshaft engines. AD 2006-23-17 resulted from a Turbomeca S.A. review of 

the engine service experience and their determination that more frequent borescope 

inspections (BSis) are required on engines not modified to the TU 191, TU 197, or TU 

224 standard. AD 2006-23-17 requires repetitive BSI and eddy current inspections (ECis) 

or ultrasonic inspections (Uis) of centrifugal compressor intake wheel (inducer) blades 

and replacement of parts that fail inspection and replacement of the TU 197 standard 

centrifugal compressor. We issued AD 2006-23-17 to prevent centrifugal compressor 

intake wheel (inducer) blade cracks, which can result in engine in-flight power loss, 

engine shutdown, or forced landing. 

Actions Since AD 2006-23-17 Was Issued 

Since we issued AD 2006-23-17, a centrifugal compressor inducer blade loss 

occurred on an engine modified to TU 224 standard. This blade loss was due to cracks caused by impacts combined with significant erosion of the part not related to the TU 224 

modification. Turbomeca S.A. has revised the inspection intervals for the centrifugal 

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the TU 197 and TU 215 standard centrifugal compressors. 

Related Service Information under 1 CFR Part 51 

We reviewed Turbomeca S.A. Alert Mandatory Service Bulletin (MSB) No. 

A249-72-0100 Version H, dated May 21, 2015. The MSB describes procedures for the 

inspection and replacement of the centrifugal compressor inducer blades. This service 

information is reasonably available because the interested parties have access to it 

through their normal course of business or by the means identified in the ADDRESSES 

section of this NPRM. 

FAA's Determination 

We are proposing this NPRM because we evaluated all the relevant information 

and determined the unsafe condition described previously is likely to exist or develop in 

other products of the same type design. 

Proposed AD Requirements 

This NPRM would require repetitive BSis, and ECis or Uls based on the inservice requirements established for the various centrifugal compressor inducer 

standards, replacement of parts that fail inspection, and replacement of the TU 197 and 

TU 215 standard centrifugal compressors. 

Costs of Compliance 

We estimate that this proposed AD affects 36 engines installed on airplanes of 

U.S. registry. We estimate that two of these engines will require compressor replacement. 

We also estimate that about 40 hours per engine are required to comply vvith this 

proposed AD. The average labor rate is $85 per hour. Parts cost about $40,000 per 

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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 44 701, "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 . 

. Regulatory Findings 

We have 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 above, I certify that the 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 II 034, February 26, 1979), 

(3) Will not affect intrastate aviation in Alaska to the extent that it justifies 

making a regulatory distinction, and 

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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. I 06(g), 40II3, 44701. 

§ 39.13 [Amended] 

2. The FAA amends§ 39.13 by removing airworthiness directive (AD) 2006-23-

I7, Amendment 39-I4829 (7I FR 66664, November I6, 2006) ("2006-23-IT'), and 

adding the following new AD: 

Turbomeca S.A.: Docket No. FAA-2006-25970; Directorate Identifier 99-NE-12-AD. 

(a) Comments Due Date 

The FAA must receive comments on this AD action by [INSERT DATE 60 

DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER]. 

(b) Affected ADs 

This AD replaces AD 2006-23-I7. 

(c) Applicability 

This AD applies to Turbomeca S.A. Tunno IV A and IV C turboshaft engines. 

(d) Unsafe Condition 

This AD was prompted by a centrifugal compressor inducer blade loss. We are 

issuing this AD to prevent failure of the centrifugal compressor inducer, which could lead 

to an uncontained blade release, damage to the engine, and damage to the airplane. 

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this AD. 

(2) Perform initial and repetitive ultrasonic inspections (Uis) or eddy current 

inspections (ECis) of the centrifugal compressor (inducer). Use Accomplishment 

Instructions, paragraph 6.B.(l)(b) ofTurbomeca S.A. Alert Mandatory Service Bulletin 

(MSB) No. A249 72 0100 Version H, dated May 21, 2015 to do the inspections. Use 

Appendix 1 ofTurbomeca S.A. Alert MSB No. A249 72 0100 Version H, dated May 21, 

2015 for the schedule of inspections. 

(3) Perform initial and repetitive borescope inspections (BSis) of the centrifugal 

compressor inducer. Use Accomplishment Instructions, paragraphs 6.B.(1)(a) of 

Turbomeca S.A. Alert MSB No. A249 72 0100 Version H, dated May 21, 2015 to do the 

inspections. Use Appendix 1 ofTurbomeca S.A. Alert MSB No. A249 72 0100 Version 

H, dated May 21,2015 for the schedule of inspections. 

( 4) If, during any inspection required by paragraphs (e)(2) or ( e)(3) of this AD, 

any crack, corrosion, or other damage is detected on the inducer, then before next flight, 

replace the centrifugal compressor. 

(5) Accomplishment of a UI or ECI of the centrifugal compressor inducer, 

required by paragraph (e)(2) of this AD, is acceptable in lieu of a BSI required by 

paragraph ( e)(3) of this AD for that engine. 

( 6) Replacement of a centrifugal compressor required by paragraph (e)( 4) of this 

AD, does not constitute terminating action for the repetitive inspections required by 

paragraphs (e)(2) and (e)(3) of this AD. 

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72 0100, Version G, or an earlier version. 

(g) Alternative Methods of Compliance (AMOCs) 

The Manager, Engine Certific_ation Office, FAA, may approve AMOCs for this 

AD. Use the procedures found in 14 CFR 39.19 to make your request. You may email 

your request to; ANE-AD-AMOC@faa.gov. 

(h) Related Information 

(1) For more information about this AD, contact Wego Wang, Aerospace 

Engineer, Engine Certification Office, FAA, Engine & Propeller Directorate, 12 New 

England Executive Park, Burlington, MA 01803; phone: 781-238-7134; fax: 781-238-

7199; email: wego.wang@faa.gov. 

(2) For service information identified in this AD, contact Turbomeca S.A., 40220 

Tarnos, France; phone: 33 (0)5 59 74 40 00; fax: 33 (0)5 59 74 45 15. 

(3) You may view this service information at the FAA, Engine & Propeller 

Directorate, 12 New England Executive Park, Burlington, MA. For information on the 

availability of this material at the FAA, call 78!-238-7125. 

Issued in Burlington, Massachusetts, on November x:-., 2015. 

Colleen M. D' Alessandro, 

Directorate Manager, Engine & Propeller Directorate, 

Aircraft Certification Service. 

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