AD 95-11-01

This amendment supersedes an existing airworthiness directive (AD), applicable to Turbomeca Arriel 1 series turboshaft engines, that currently requires repetitive checks for engine rubbing noise during gas generator shutdown, and for free rotation of the gas generator by rotating the compressor manually after the last flight of the day. This amendment continues to require these checks, but eliminates the reference to the Turbomeca service bulletin, allows the pilot to perform all the checks required in this AD, clarifies the inspection interval requirement for daily checks, and specifies terminating action for the repetitive checks required by this AD. In addition, this AD allows the check for engine rubbing noise to be performed during engine motoring, and specifies that the engine turbine (T4) temperature must be below 150 degrees Centigrade when performing the check for free rotation. This amendment is prompted by comments submitted by operators of the affected enginesin response to the existing AD and the availability of an improved design 2nd stage nozzle guide vane. The actions specified by this AD are intended to prevent engine failure due to rubbing of the 2nd stage turbine disk on the 2nd stage turbine nozzle guide vane, which could result in complete engine failure and damage to the aircraft.

Final rule.

95-11-01 Turbomeca: Amendment 39-9235. Docket 94-ANE-08. Supersedes AD 93-23-09, Amendment 39-8745.
Applicability: Turbomeca Arriel turboshaft engines Models 1B that do have modification TU 76 but do not have modification TU 197 or TU 202; Arriel Models 1D and 1D1 that do not have modification TU 197 or TU 202; Arriel Models 1A, 1A1, 1A2 that have had modification TU 76 but do not have modification TU 197 or TU 202; and Arriel Models 1C, 1C1, and 1C2 that do not have modification TU 197 or TU 202. These engines are installed on but not limited to Aerospatiale Models AS350B, SA365, and AS565 helicopters. NOTE: This AD applies to each engine identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For engines that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must use the authority provided in paragraph (f) to request approval from the FAA. This approval may address either no action, if the current configuration eliminates the unsafe condition, or different actions necessary to address the unsafe condition described in this AD. Such a request should include an assessment of the effect of the changed configuration on the unsafe condition addressed by this AD. In no case does the presence of any modification, alteration, or repair remove any engine from the applicability of this AD.
Compliance: Required as indicated, unless accomplished previously.
To prevent engine failure due to rubbing of the 2nd stage turbine disk on the 2nd stage turbine nozzle guide vane, which could result in engine failure and damage to the aircraft, accomplish the following:
(a) For Turbomeca Arriel turboshaft engines Models 1B that have modification TU 76 but do not have modification TU 197 or TU 202; and Arriel Models 1D and 1D1 that do not have modification TU 197 or TU 202; accomplish the following:
(1) Perform a daily check for unusual engine rubbing noises during gas generator shutdown or as engine gas generator speed decreases after completion of engine motoring.
(2) Perform a daily check for free rotation of the gas generator, when T4 temperature is below 150 degrees Centigrade, by rotating the compressor manually.
(3) While checking for free rotation of the gas generator, perform a check for engine rubbing noise.
(b) For Turbomeca Arriel turboshaft engines Models 1A, 1A1, 1A2 that have modification TU 76 but do not have modification TU 197 or TU 202; and Arriel Models 1C, 1C1, and 1C2 that do not have modification TU 197 or TU 202; accomplish the following:
(1) Within 50 hours time in service (TIS) after the effective date of this AD, perform a check for unusual engine rubbing noise during gas generator shutdown or as engine gas generator speed decreases after completion of engine motoring.
(2) Thereafter, at intervals not to exceed 50 hours TIS since the last check, perform a check for unusual engine rubbing noise during gas generator shutdown or as engine gas generator speed decreases after completion of engine motoring.
(3) Perform a daily check for free rotation of the gas generator when T4 temperature is below 150 degrees C, by rotating the compressor manually.
(4) While checking for free rotation of the gas generator, perform a check for engine rubbing noise.
(c) If any engine rubbing noise is detected during the checks required by paragraphs (a) and (b) of this AD, prior to further flight replace gas generator module M03 with a serviceable module.
(d) Install the improved 2nd stage nozzle guide vane, modification TU 202 or TU 197, at the next engine overhaul after the effective date of this AD, but not later than December 31, 2002, in accordance with Turbomeca Service Bulletin (SB) 292 72 0150, dated April 10, 1992, or in accordance with SB 292 72 0153, dated February 22, 1993, respectively. Installation of this hardware constitutes terminating action to the checks required by this AD.
(e) The checks required by paragraphs (a) and (b) of this AD may be performed by the pilot holding at least a private pilot certificate as an exception to the requirements of part 43 of the Federal Aviation Regulations (14 CFR part 43). The checks must be recorded in accordance with Sections 43.9 and 91.417(a)(2)(v) of the Federal Aviation Regulations (14 CFR 43.9 and 14 CFR 91.417(a)(2)(v)), and the records must be maintained as required by the applicable Federal Aviation Regulation.
(f) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Engine Certification Office. The request should be forwarded through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Engine Certification Office. NOTE: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Engine Certification Office.
(g) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the aircraft to a location where the requirements of this AD can be accomplished.
(h) The actions required by this AD shall be done in accordance with the following Turbomeca SB's:

Document No.
Pages
Date
292 72 0150
1-4
April 10, 1992
Total pages: 4.

292 72 0153
1-5
February 22, 1993
Total pages: 5.

This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Turbomeca 64511 Bordes Cedex - France. Copies may be inspected at the FAA, New England Region, Office of the Assistant Chief Counsel, 12 New England Executive Park, Burlington, MA; or at the Office ofthe Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.
(i) This amendment becomes effective on June 21, 1995.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 93-23-09, Amendment 39-8745 (58 FR 63061, November 30, 1993), which is applicable to Turbomeca Arriel 1 series turboshaft engines, was published in the Federal Register on September 6, 1994 (59 FR 46005). That notice of proposed rulemaking (NPRM) proposed to continue to require repetitive checks for engine rubbing noise during gas generator shutdown, and for free rotation of the gas generator by rotating the compressor manually at a daily interval until installation of the improved 2nd stage nozzle guide vane. That NPRM proposed to allow pilots to perform all the required checks. Performing these checks does not require special training beyond that already incurred by pilots of the aircraft having affected engines, or the use of tools or special measuring equipment, or reference to technical data. Accordingly, the FAA has determined that pilots may perform all the checks required by that NPRM as an exception to Section 43.3 of the Federal Aviation Regulations (14 CFR 43.3) regarding the performance of maintenance.
In addition, the NPRM proposed to allow the check for engine rubbing noise to be performed during engine motoring, and specifies that the engine turbine (T4) temperature must be below 150 degrees Centigrade when performing the check for free rotation. Also, the NPRM proposed to require installation of modification TU 202, which incorporates an improved 2nd stage nozzle guide vane manufactured from a new material that is more resistant to fatigue cracking, at the next engine overhaul after the effective date of the NPRM, but not later than December 31, 1999, as terminating action for the repetitive checks. This calendar end-date is based upon parts availability. The installation would be performed in accordance with Turbomeca Service Bulletin No. 292 72 0150, dated April 10, 1992.
This engine model is manufactured inFrance and is type certificated for operation in the United States under the provisions of Section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement in effect at the time of type certification. The Direction Generale de L'Aviation Civile (DGAC), which is the airworthiness authority for France, has kept the FAA informed of the situation described above. The FAA has examined the findings of the DGAC, reviewed all available information, and determined that AD action is necessary for products of this type design that are certificated for operation in the United States.
Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.
One commenter (the manufacturer) states that Arriel engine models 1A, 1A1, 1A2, 1C, 1C1, and 1C2 should be removed from the AD's applicability since these models are all installed in twin- engine helicopters. The FAA does not concur. The engine design characteristics that produce the unsafe condition are common to the Arriel 1 engine models specified in the applicability section of the proposed rule, and therefore must remain in the AD to correct for the unsafe condition.
The commenter also states that the compliance end-date for installation of the terminating action should be extended from December 31, 1999, to December 31, 2002, to facilitate logistical support of the improved hardware. The FAA concurs and has revised the compliance section of this final rule accordingly.
The commenter also states that modification TU 197 should be designated in addition to TU 202 as terminating action for the inspection requirements of this AD. Modification TU 197 is an improved 2nd stage nozzle guide vane introduced to correct for the unsafe condition that is installed on production engines, whereas TU 202, which is a similar design improvement, was introduced for in-service engines.The FAA concurs and has revised the compliance section of this final rule accordingly.
Since publication of the NPRM, the FAA has increased its estimate of labor cost from $55 to $60 per work hour to better reflect current maintenance labor rates. The FAA has revised the economic analysis of this final rule.
After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes described previously. The FAA has determined that these changes will not increase the scope of the AD.
The FAA estimates that 160 engines installed on aircraft of U.S. registry will be affected by this AD, that it will take approximately 0.2 work hours per engine to accomplish the required actions, and that the average labor rate is $60 per work hour. Required parts will cost approximately $8,000 per engine. Based on an assumed utilization rate and an assumed modification rate,the total cost impact of the AD on U.S. operators over the five year compliance period is estimated to be $3,105,440.
The regulations adopted herein will not have substantial direct effects 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. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.
For the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) 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. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES." List of Subjects in 14 CFR Part 39
Air Transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (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. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89. 39.13 - [AMENDED]
2. Section 39.13 is amended by removing Amendment 39-8745 (58 FR 63061, November 30, 1993) and by adding a new airworthiness directive, Amendment 39-9235, to read as follows: