AD 94-12-07

This amendment supersedes an existing airworthiness directive (AD), applicable to Sikorsky Aircraft Model S-58T series helicopters, that currently requires a one-time inspection of the engine drive shaft assembly (drive shaft assembly) for cracks and loose balance weights. This amendment requires initial and repetitive visual and florescent penetrant inspections of the drive shaft assembly for cracks and improperly installed rivets. This amendment is prompted by three reported incidents of loose or missing drive shaft assembly balance weights and two reported incidents of fatigue cracks on the drive shaft assembly near the balance weight rivet hole. The actions specified by this AD are intended to prevent failure of the drive shaft assembly, loss of power to the rotor system, and a subsequent forced landing of the helicopter.

Final rule

94-12-07 SIKORSKY AIRCRAFT: Amendment 39-8935. Docket Number 93-SW-07-AD. Supersedes AD 90-10-02, Amendment 39-6590.

Applicability: Model S-58T series helicopters, equipped with engine drive shaft assembly (drive shaft assembly), part number (P/N) 58350-10030-045 and subassembly P/N 58350-10030-046, or drive shaft assembly, P/N 58350-10030-047 and subassemblies 58350-10030-048 and -049, certificated in any category. The subassembly part numbers will appear adjacent to the 58350-10030-045 and 58350-10030-047 drive shaft assembly part numbers.

Compliance: Required as indicated, unless accomplished previously.

To prevent failure of the drive shaft assembly, loss of power to the rotor system, and a subsequent forced landing of the helicopter, accomplish the following:

(a) Within the next 25 hours' time-in-service (TIS) after the effective date of this AD, or at the next removal of the drive shaft assembly, P/N 58350-10030-045 and subassembly -046, or P/N 58350-10030-047 and subassemblies -048 and -049, whichever comes first--

(1) Remove and inspect the drive shaft assembly for proper installation of rivets, loose balance weights, and cracks in accordance with paragraphs 2.A.(1), (2), and (4) of the Accomplishment Instructions of Sikorsky Alert Service Bulletin (ASB) No. 58B35-31A, Revision A, dated February 17, 1993.

(2) If a crack, loose balance weight, or improper rivet installation is found, replace the drive shaft assembly with an airworthy drive shaft assembly.

(b) Within the next 25 hours' TIS after compliance with paragraph (a) of this AD, and at every 25 hours' TIS thereafter, visually inspect the drive shaft assembly for cracks in accordance with paragraph 2.B. of the Accomplishment Instructions of ASB No. 58B35-31A, Revision A, dated February 17, 1993.

(c) For drive shaft assembly, P/N 58350-10030-045 and subassembly -046, that have not been reworked in accordance with Sikorsky Overhaul Repair Instruction (ORI) No. 58350-001, Revision A, dated November 18, 1992, within 250 hours' TIS after the inspections required by paragraph (a) of this AD, and thereafter at intervals not to exceed 250 hours' TIS, remove and inspect the drive shaft assembly in accordance with paragraph 2.C. of the Accomplishment Instructions of ASB No. 58B35-31A, Revision A, dated February 17, 1993.

(d) For drive shaft assembly, P/N 58350-10030-047 and subassemblies -048 and -049, and additionally, for drive shaft assembly, P/N 58350-10030-045 and subassembly -046, that have been reworked in accordance with ORI No. 58350-001, Revision A, dated November 18, 1992, within 2,500 hours' TIS after the inspections required by paragraph (a) of this AD, and thereafter at intervals not to exceed 2,500 hours' TIS, remove and inspect the drive shaft assembly in accordance with subparagraph 2.D of the Accomplishment Instructions of ASB No. 58B35-31A, Revision A, dated February 17, 1993.

(e) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used when approved by the Manager, Boston Aircraft Certification Office, FAA. Operators shall submit their requests through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Boston Aircraft Certification Office.

NOTE: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Boston Aircraft Certification Office.

(f) 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 helicopter to a location where the requirements of this AD can be accomplished.

(g) The inspections and replacement, if necessary, shall be done in accordance with Sikorsky Alert Service Bulletin No. 58B35-31A, Revision A, dated February 17, 1993. This incorporation by reference was approvedby 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 Sikorsky Aircraft Division, United Technologies Corporation, North Main Street, Stratford, Connecticut 06601. Copies may be inspected at the FAA, Office of the Assistant Chief Counsel, 2601 Meacham Boulevard, Room 663, Fort Worth, Texas; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(h) This amendment becomes effective on August 1, 1994.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 90-10-02, Amendment 39-6590 (55 FR 18305, May 2, 1990), which is applicable to Sikorsky Aircraft Model S-58T series helicopters, was published in the Federal Register on August 31, 1993 (58 FR 45859). That action proposed to require initial and repetitive visual and florescent penetrant inspections of the engine drive shaft assembly for cracks and loose balance weights, and replacement as necessary.

Interested persons have been afforded an opportunity to participate in the making of this amendment. No comments were received on the proposal or the FAA's determination of the cost to the public. The FAA has determined that air safety and the public interest require the adoption of the rule as proposed, except for editorial changes.

The FAA estimates that 58 helicopters of U.S. registry will be affected by this AD, that it will take approximately18 work hours per helicopter to accomplish the required actions, and that the average labor rate is $55 per work hour. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $57,420.

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 asubstantial 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 39-6590, (55 FR 18305, May 2, 1990), and by adding a new airworthiness directive (AD), Amendment 39-8935, to read as follows: