AD 99-11-04

This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) 99-11-04 which was sent previously to all known U.S. owners and operators of Sikorsky Aircraft Model S-76A helicopters by individual letters. This AD requires, before further flight, either revising the flight manual to show reduced single-engine rotorcraft performance or determining if an AC generator interlock system is installed. If an interlock system is installed, the flight manual revision is not required. This amendment is prompted by the discovery that Sikorsky Aircraft Model S-76A helicopters with Turbomeca Arriel 1S1 engines may fail to achieve the specified single-engine rotorcraft performance if an AC generator interlock system is not installed. The actions specified by this AD are intended to prevent the inability of the rotorcraft to achieve certain published one-engine-inoperative performance.

Final rule; request for comments

99-11-04 SIKORSKY AIRCRAFT CORPORATION: Amendment 39-11205. Docket No. 99-SW-26-AD.

Applicability: Sikorsky Model S-76A helicopters with Turbomeca Arriel 1S1 engines installed in accordance with Supplemental Type Certificate SH568NE, including drawing number 76070-30601.

NOTE 1: This AD applies to each helicopter identified in the preceding applicability provision, regardless of whether it has been otherwise 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 request approval for an alternative method of compliance in accordance with paragraph (e) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Before further flight, unless accomplished previously.

To reduce the published Category "A" maximum takeoff and landing gross weights and single-engine forward climb performance limitations of the Rotorcraft Flight Manual (RFM), when an AC generator interlock system is not installed, accomplish the following:

(a) Insert Sikorsky Model S-76A RFM Supplement (RFMS) No. 29B, Temporary Revision 1, dated April 9, 1999, into RFMS No. 29B, dated December 21, 1993, or

(b) Determine if the AC generator interlock relays are installed by conducting the following inspection:

(1) Uncover the No. 2 Relay Panel, located in the right side of the cockpit overhead. This panel is also referred to as the right-hand panel.

(2) Inspect for the presence of the AC generator interlock relays identified as K43 and K44 (two relays) or K46, K47, and K48 (three relays).

NOTE 2: For S-76A helicopters, serial numbers (S/N s) 760001 through760237, the AC generator interlock relays are wired through splice groups to the K31, K32, K11, and K13 relays. For S-76A helicopters, S/N s 760238 and higher, the AC generator interlock relays are wired through splice groups to the K11 and K13 relays. Depending on how and when each helicopter was modified, the labels on these relays could be K43 and K44 (two relays) or K46, K47, and K48 (three relays).

NOTE 3: Sikorsky Aircraft Corporation Alert Service Bulletin 76-77-4A, Revision A, dated May 5, 1999, pertains to the subject of this AD.

(3) If the AC generator interlock relays are installed, no further action is required by this AD.

(4) If the AC generator interlock relays are not installed, insert Sikorsky S-76A RFMS No. 29B, Temporary Revision 1, dated April 9, 1999, into RFMS No. 29B, dated December 21, 1993.

(c) This AD revises the Limitations Section of the RFM for helicopters on which the AC generator interlock relays are not installed by inserting a new RFMS revision limiting Category "A" gross weight and reducing published climb performance.

(d) Remove Sikorsky Model S-76A RFMS No. 29B, Temporary Revision 1, dated April 9, 1999, inserted into RFMS No. 29B, dated December 21, 1993, from the RFM upon installation of one of the following, as applicable:

(1) For Model S-76A helicopters, S/N s 760001 through 760237, AC generator interlock kit (kit), part number (P/N) 33776-84790-012.

(2) For Model S-76A helicopters, S/N s 760238 and higher, kit, P/N 33776-84790-011.

(e) 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 4: 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) This amendment becomes effective on July 9, 1999, to all persons except those persons to whom it was made immediately effective by Priority Letter AD 99-11-04, issued May 13, 1999, which contained the requirements of this amendment.

On May 13, 1999, the FAA issued Priority Letter AD 99-11-04, applicable to Sikorsky Aircraft Model S-76A helicopters, which requires, before further flight, either revising the flight manual to show reduced single-engine rotorcraft performance or determining if an AC generator interlock system is installed. If an interlock system is installed, the flight manual revision is not required. That action was prompted by the discovery that Sikorsky Aircraft Model S-76A helicopters with Turbomeca Arriel 1S1 engines may fail to achieve the specified single-engine rotorcraft performance if an AC generator interlock system is not installed. This condition, if not corrected, could result in the inability of the rotorcraft to achieve certain published one-engine-inoperative performance.

Since the unsafe condition described is likely to exist or develop on other Sikorsky Aircraft Model S-76A helicopters of the same type design, the FAA issued Priority Letter AD 99-11-04 to reduce the published Category "A" maximum takeoff and landing gross weights and single-engine forward climb performance limitations of the Rotorcraft Flight Manual (RFM), when an AC generator interlock system is not installed. The AD requires, before further flight, revising the RFM to publish reduction of Category "A" weight by 150 pounds and single-engine performance by 50 feet per minute, or determining whether an AC generator interlock system has been installed. If the AC generator interlock system is not installed, the revision to the RFM is required. The short compliance time involved is required because the previously described critical unsafe condition can adversely affect the controllability of the helicopter. Therefore, revising the flight manual to show reduced single-engine rotorcraft performance or determining if an AC generator interlock system is installed is required before further flight, and this AD must be issued immediately.

Since it was found that immediate corrective action was required, notice and opportunity for prior public comment thereon were impracticable and contrary to the public interest, and good cause existed to make the AD effective immediately by individual letters issued on May 13, 1999, to all known U.S. owners and operators of Sikorsky Aircraft Model S-76A helicopters. These conditions still exist, and the AD is hereby published in the Federal Register as an amendment to section 39.13 of the Federal Aviation Regulations (14 CFR 39.13) to make it effective to all persons. There is a minor editorial change in this published version of the priority letter AD; the FAA has determined that this change will neither increase the economic burden on any operator nor increase the scope of the AD.

The FAA estimates that 5 helicopters of U.S. registry will be affected by this AD, that it will take approximately 0.5 work hour per helicopter to revise the RFM, and that the average labor rate is $60 per work hour. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $150 to revise the RFM on the entire fleet.

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 wouldbe 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. 99-SW-26-AD." The postcard will be date stamped and returned to the commenter.

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.

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 U.S.C. 106(g), 40113, 44701.

39.13 [Amended]
2. Section 39.13 is amended by adding a new airworthiness directive to read as follows: