AD 96-15-03 ACTIVE

This amendment supersedes an existing Airworthiness Directive (AD), applicable to Sikorsky Aircraft Model S-76B helicopters, that requires an inspection of the drive shaft for cracks or loose balance weights. This amendment also supersedes a Priority Letter AD that currently requires repetitive inspections for cracks in the driveshaft in helicopters with certain engine drive shaft assemblies (drive shafts) installed. This amendment is prompted by a report of a fatigue crack found in a drive shaft that was caused by fretting of a balance weight rivet washer. The actions specified by this AD are intended to prevent failure of the drive shaft, loss of power to the rotor system, and a subsequent forced landing of the helicopter.

Final rule; request for comments

96-15-03 SIKORSKY AIRCRAFT: Amendment 39-9696. Docket Number 96-SW-16-AD. Supersedes Priority Letter AD 93-11-05, issued June 4, 1993, and AD 91-19-02, Amendment 39-8028.

Applicability: Sikorsky Aircraft S-76B helicopters, with engine drive shaft assembly (drive shaft), part number (P/N) 76361-09202-044, -047, -049, or -051, with either rivet, P/N CR3523P-8- XX, with a washer or balance weight, or rivet, P/N NAS1738MW6-X, with or without a washer, installed, certificated in any category.

NOTE 1: This AD applies to each helicopter 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 helicopters 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 (c) 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 helicopter from the applicability of this AD.

Compliance: Required as indicated, unless accomplished previously.

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

(a) Within 6 hours TIS after the effective date of this AD, visually inspect the drive shaft for cracks in the area around each rivet, using a 10X or higher magnifying glass, and inspect the drive shaft for loose balance weights.

(1) The inspection for loose balance weights shall be performed by grasping the balance weights by hand and attemptingto move them in both the radial and axial directions. Any movement of the balance weights constitutes looseness.

(2) If a crack is found on the drive shaft or any balance weight is loose, replace the drive shaft with an airworthy drive shaft before further flight.

(b) Thereafter, inspect for cracks and loose balance weights at intervals not to exceed 6 hours TIS from the last inspection.

(c) 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, 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 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Boston Aircraft Certification Office.

(d) 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.

(e) This amendment becomes effective on August 19, 1996.

On August 26, 1991, the FAA issued AD 91-19-02, Amendment 39-8028 (56 FR 47378, September 19, 1991) to require an initial and repetitive 25-hour interval inspections of the left and right engine input drive shaft assemblies for loose balance weights or cracks. On June 4, 1993, the FAA issued priority letter AD 93-11-05, applicable to Sikorsky Aircraft Model S-76B helicopters, which requires initial and repetitive inspections of certain engine drive shafts assemblies for cracks only.

Both AD 91-19-02, issued August 26, 1991, and priority letter AD 93-11-05, issued June 4, 1993, require initial and repetitive inspections of certain drive shafts assemblies for cracks. AD 91- 19-02 also requires an inspection for loose drive shaft balance weights. As a result of having two ADs that require different corrective actions, operators may be confused about which corrective actions to perform. Such confusion may lead an operator to inadvertently fail to comply with the necessary safety requirements for those rotorcraft and result in an unsafe condition. Therefore, due to the criticality of maintaining the inspection of the drive shaft and the short compliance time, this rule incorporates both corrective actions and must be issued immediately to correct an unsafe condition.

Since the unsafe condition described is likely to exist or develop on other Sikorsky Aircraft Model S-76B helicopters of the same type design, this AD supersedes AD 91-19-02 and priority letter AD 93-11-05 and requires, within the next 6 hours time-in-service (TIS), an initial inspection of Model S-76B helicopters with certain engine drive shafts; balance weights or balance weight rivets (rivets); or balance weight and rivet and washers combinations installed. If a rivet, rivet/washer combination, or rivet/washer/balance weight combination is installed, an initial inspection of the drive shaft is required for cracks and loose balance weights, and thereafter, repetitive inspections every 6 hours TIS.

Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in 30 days.

Comments Invited
Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications should identify the Rules Docket number and be submitted in triplicate to the address specified under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket No. 96-SW-16-AD." The postcard will be date stamped and returned to the commenter.

The regulations adopted herein will not have substantial direct effects onthe 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.

The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, 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, 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 USC 106(g), 40113, 44701.

39.13 - [Amended]
2. Section 39.13 is amended by removing Amendment 39-8028 (56 FR 47378, September 19, 1991) and by adding a new airworthiness directive (AD), Amendment 39-9696, to read as follows:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Office of the Assistant Chief Counsel, Attention: Rules Docket No. 96-SW-16-AD, 2601 Meacham Blvd., Fort Worth, Texas 76137.

Mr. Terry Fahr, Aerospace Engineer, Boston Aircraft Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington Massachusetts 01803, telephone (617) 238-7155, fax (617) 238-7199.