AD 99-05-08

This amendment adopts a new airworthiness directive (AD) that is applicable to McDonnell Douglas Helicopter Systems (MDHS) Model MD-900 helicopters. This action requires establishing or reducing certain life limits, applying serial numbers (S/N's), determining hours time-in-service (TIS), and creating component history cards or equivalent records for various parts. This amendment is prompted by analysis that indicates a need for establishing or reducing life limits to avoid fatigue failure of certain parts. The actions specified by this AD are intended to apply appropriate life limits to various parts.

Final rule; request for comments

99-05-08 MCDONNELL DOUGLAS HELICOPTER SYSTEMS: Amendment 39-11056. Docket No. 98-SW-34-AD.

Applicability: McDonnell Douglas Helicopter Systems (MDHS) MD-900 helicopters, 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 (d) 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 casedoes 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 establish life limits and place a serial number (S/N) on various critical parts, accomplish the following:

(a) Remove from service:

(1) Main rotor drive shaft, part number (P/N) 900D2436528-101, 900D6400004-101, 900DF436026-101, or 900DF400100-101, on or before attaining 1,450 hours time-in-service (TIS).

(2) NOTAR pitch plate assembly, P/N 900R2443000-105, on or before attaining 3,527 hours TIS.

(3) Spherical/slider main rotor bearing, P/N 900C3010042-105, on or before attaining 12,807 hours TIS.

(b) On or before attaining 600 hours TIS after the effective date of this AD or by June 30, 1999, whichever occurs first.

(1) Apply the specified S/N to the pitch plate assembly, P/N 900R2443000-105, on each Model MD-900 helicopter with S/N's 900-00002 through 900-00057, as specified in MDHS Service Bulletin SB 900-058R1, dated July 6, 1998.

(2) Determine the hours TIS and create a component history card or equivalent record for the NOTAR tension-torsion fan blade strap assembly, P/N 500N5311-5 or 900R3442009-101, and NOTAR pitch plate assembly, P/N 900R2443000-105.

(c) This AD revises the Airworthiness Limitations Section of the MD-900 Maintenance Manual by establishing new retirement lives and adding parts to the life-limited parts list.

NOTE 2: The Airworthiness Limitations Section of the MD-900 Rotorcraft Maintenance Manual, Reissue 1, Revision 2, dated July 24, 1998, pertains to the subject of this AD.

(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, Los Angeles 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, Los Angeles Aircraft Certification Office.

NOTE 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Rotorcraft Standards Staff.

(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.

(f) The corrective action in paragraph (b)(1) shall be accomplished in accordance with McDonnell Douglas Helicopter Systems Service Bulletin SB 900-058R1, dated July 6, 1998. 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 McDonnell Douglas Helicopter Systems, Technical Publications, Bldg. 530/B11, 5000 E. McDowell Road, Mesa, Arizona 85205-9797, telephone 1-800-388-3378,fax 602-891-6782. Copies may be inspected at the FAA, Office of the Regional Counsel, Southwest Region, 2601 Meacham Blvd., Room 663, Fort Worth, Texas; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(g) This amendment becomes effective on March 18, 1999 .

This amendment adopts a new AD that is applicable to MDHS Model MD-900 helicopters. Analysis indicates a need for establishing life limits, applying S/N's, determining hours time-in-service (TIS), and creating component history cards or equivalent records for various parts. This AD requires (1) establishing a life limit for the main rotor drive shafts, P/N's 900D2436528-101, 900D6400004-101, 900DF436026-101, and 900DF400100-101 to 1,450 hours TIS; reducing the life limit for the NOTAR pitch plate assembly, P/N 900R2443000-105, from 10,000 to 3,527 hours TIS; and establishing a life limit for the spherical/slider main rotor bearings, P/N 900C3010042-105, of 12,807 hours TIS; (2) determining the hours TIS and creating a component history card or equivalent record for the NOTAR tension-torsion fan blade strap assembly, P/N 500N5311-5 or 900R3442009-101, and NOTAR pitch plate assembly, P/N 900R2443000-105; and (3) applying appropriate S/N's to the NOTAR pitch plate assembly, P/N 900R2443000-105, on each helicopter S/N's 900-00002 through 900-00057. This amendment is prompted by the FAA's determination, after reviewing the manufacturer's analysis, that a reduction in life limits is necessary. The actions specified in this AD are intended to establish appropriate life limits for certain parts.

The FAA has reviewed MDHS Service Bulletin (SB) 900-058R1, dated July 6, 1998, which provides procedures for applying life limits and S/N's to certain parts.

Since an unsafe condition has been identified that is likely to exist or develop on other MDHS Model MD-900 helicopters of the same type design, this AD requires reducing or establishing life limits, adding S/N's, determining hours TIS, and creating component history cards or equivalent records for various parts. The actions are required to be accomplished in accordance with the SB previously described. The short compliance time is required because the previously described critical unsafe condition can adversely affect the controllability and structural integrity of the helicopter. Therefore, establishing appropriate life limits for various parts is required because several helicopters are approaching life limits, and this AD must be issued immediately.

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 less than 30 days.

The FAA estimates that 27 helicopters will be affected by this proposed AD, that it will take approximately 2.5 work hours to add S/N's to the parts and create component history cards or equivalent records, 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 $4,050 assuming no parts will be replaced as a result of this AD.

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. 98-SW-34-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, 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. 106(g), 40113, 44701.

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