Airworthiness Directives; Sikorsky Aircraft-manufactured Model CH-54A Helicopters

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the supersedure of an existing airworthiness directive (AD), applicable to Sikorsky Aircraft-manufactured Model CH-54A helicopters, that currently requires initial and recurring inspections and rework or replacement, if necessary, of the second stage lower planetary plate (plate). This action would require the same actions as the existing AD but would add two additional type certificate (TC) holders to the applicability of the AD and change one TC holder who has transferred ownership of the affected helicopters since the issuance of the existing AD. This proposal is prompted by the discovery that the applicability section of the existing AD is incomplete. The actions specified by the proposed AD are intended to prevent failure of the plate due to fatigue cracking which could result in failure of the main gearbox, failure of the drive system, and subsequent loss of control of the helicopter.

DATES:

Comments must be received on or before June 19, 2000.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Office of the Regional Counsel, Southwest Region, Attention: Rules Docket No. 99-SW-81-AD, 2601 Meacham Blvd., Room 663, Fort Worth, Texas 76137. You may also send comments electronically to the Rules Docket at the following address: 9-asw-adcomments@faa.gov. Comments may be inspected at the Office of the Regional Counsel between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal holidays.

FOR FURTHER INFORMATION CONTACT:

Uday Garadi, Aviation Safety Engineer, Rotorcraft Standards Staff, Rotorcraft Directorate, FAA, Fort Worth, Texas 76193-0110, telephone (817) 222-5123, fax (817) 222-5961.

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the proposed 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 above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this notice may be changed in light of the comments received.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their mailed comments submitted in response to this notice must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket No. 99-SW-81-AD.” The postcard will be date stamped and returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request to the FAA, Office of the Regional Counsel, Southwest Region, Attention: Rules Docket No. 99-SW-81-AD, 2601 Meacham Blvd., Room 663, Fort Worth, Texas 76137.

Discussion

On March 25, 1999, the FAA issued AD 99-07-16, Amendment 39-11102 (64 FR 15669, April 1, 1999), to require initial and recurring inspections and rework or replacement, if necessary, of the plate. Cracks on the plate, part number 6435-20229-102, initiate at and radiate from the lightening holes in the plate web due to fatigue. That action was prompted by cracked plates that were found during overhaul and inspections. The requirements of that AD are intended to prevent failure of the plate due to fatigue cracking, which could result in failure of the main gearbox, failure of the drive system, and subsequent loss of control of the helicopter.

Since the issuance of that AD, the FAA has discovered that two TC holders were inadvertently omitted from the applicability section and one TC holder has transferred the TC for an affected model helicopter.

Since an unsafe condition has been identified that is likely to exist or develop on other Sikorsky Aircraft-manufactured Model CH-54A helicopters of the same type design, the proposed AD would supersede AD 99-07-16 to require initial and recurring inspections and rework or replacement, if necessary, of the plate.

The FAA estimates that 12 helicopters of U.S. registry would be affected by this proposed AD, that it would take approximately 8 work hours per helicopter to accomplish the proposed inspections and 56 hours to remove and replace the plate, and that the average labor rate is $60 per work hour. Required parts would cost approximately $8,000 per helicopter. Based on these figures, the total cost impact of the proposed AD on U.S. operators is estimated to be $142,080 to replace the plates in the entire fleet.

The regulations proposed herein 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. Therefore, it is determined that this proposal would not have federalism implications under Executive Order 13132.

For the reasons discussed above, I certify that 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); and (3) if promulgated, 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 copy of the draft regulatory evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting 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

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend 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. 106(g), 40113, 44701.

(b) For any plate, P/N 6435-20229-102, that has been reworked and identified with “TS-107,” on or before the accumulation of 1,500 hours TIS and thereafter at intervals not to exceed 70 hours TIS, accomplish the following:

(1) Inspect the plate for a crack in the area around all nine lightening holes using a Borescope or equivalent inspection method (see Figure 2).

(2) If a crack is found, replace the plate with an airworthy plate prior to further flight.

Image Not Available

(c) On or before the accumulation of 2,600 hours TIS, remove from service plates, P/N 6435-20229-102, reidentified as P/N 6435-20229-102-TS-107 after rework. This AD revises the airworthiness limitation section of the maintenance manual by establishing a retirement life of 2,600 hours TIS for the main gearbox assembly second stage lower planetary plate, P/N 6435-20229-102, reidentified as P/N 6435-20229-102-TS-107 after rework.

(d) 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, Rotorcraft Certification Office, Rotorcraft Directorate, FAA. Operators shall submit their requests through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Rotorcraft Certification Office.

Note 2:

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

(e) 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.