AD 2004-23-15

This amendment adopts a new airworthiness directive (AD) for the MD Helicopters, Inc. (MDHI) Model MD900 helicopters. This action requires reducing the life limit of certain Notar fan system tension- torsion (TT) straps. This action also requires, at a specified time interval, removing each affected TT strap from the helicopter, doing a visual and x-ray inspection, and replacing any unairworthy part before further flight. Reporting the discovery of any unairworthy TT strap is also required. This amendment is prompted by two recent in-flight TT strap failures. The actions specified in this AD are intended to prevent failure of a TT strap resulting in loss of directional control and subsequent loss of control of the helicopter.

Final rule; request for comments.

2004-23-15 MD Helicopters, Inc.: Amendment 39-13870. Docket No. FAA- 2004-19613; Directorate Identifier 2004-SW-38-AD.

Applicability: Model MD900 helicopters, with a Notar fan system that has a tension-torsion (TT) strap, part number (P/N) 900R3442009-103, 900R6442009-103, 900R3442009-101, or 500N5311-5, installed, certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To prevent failure of a TT strap in the Notar fan system, which could result in loss of directional control and subsequent loss of control of the helicopter, accomplish the following:

(a) Before further flight, for TT straps, P/N 900R3442009-103 and 900R6442009-103, reduce the life limit from 3034 to 2500 hours time-in-service (TIS).

(b) Within 10 hours TIS, for any TT strap that has accumulated 1190 or more hours TIS, remove the TT strap from the helicopter and do a visual and x-ray inspection in accordance with the Inspection Instructions, paragraph 2.B.(1). through (5). and Figures 1 and 2 of MD Helicopters Service Bulletin SB900-095, dated November 3, 2004 (SB). Replace any unairworthy part before further flight.

(c) Before the TT strap accumulates 1200 hours TIS, for any TT strap with less than 1190 hours TIS, remove the TT strap from the helicopter and do a visual and x-ray inspection in accordance with the Inspection Instructions, paragraph 2.B.(1). through (5). and Figures 1 and 2 of the SB. Replace any unairworthy part before further flight.

(d) The x-ray inspection of the TT strap must be performed by a Level II or higher x-ray technician who is qualified under the guidelines established by MIL-STD-410E, ATA Specification 105, AIA- NAS-410, or an FAA-accepted equivalent for qualification standards.

(e) Within 7 days, for any TT strap that you find unairworthy, report the helicopter serial number (S/N), the TT strap P/N and S/N, the total hours TIS on the TT strap, and a description of the part condition rendering it unairworthy. Report the information to Roger Durbin, Aviation Safety Engineer, FAA, Los Angeles Aircraft Certification Office, Airframe Branch, 3960 Paramount Blvd., Lakewood, California 90712, telephone (562) 627-5233, fax (562) 627- 5210.

(f) Information collection requirements contained in this AD have been approved by the Office of Management and Budget (OMB) under the provisions of the Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.) and have been assigned OMB Control Number 2120- 0056.

(g) This AD revises the Airworthiness Limitations section of the maintenance manual by reducing the life limit of the TT strap, P/N 900R3442009-103 and 900R6442009-103, from 3034 hours TIS to 2500 hours TIS.

(h) To request a different method of compliance or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. Contact the Los Angeles Aircraft Certification, Transport Airplane Directorate, FAA, for information about previously approved alternative methods of compliance.

(i) The inspections shall be done in accordance with MD Helicopters Service Bulletin SB900-095, dated November 3, 2004. The Director of the Federal Register approved this incorporation by reference in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from MD Helicopters Inc., Attn: Customer Support Division, 4555 E. McDowell Rd., Mail Stop M615- GO48, Mesa, Arizona 85215-9734, telephone 1-800-388-3378, fax 480- 891-6782, or on the web at http://www.mdhelicopters.com. Copies may be inspected at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html .

(j) This amendment becomes effective on December 7, 2004.

This amendment adopts a new AD applicable to MDHI Model MD900 helicopters with a TT strap, part number (P/N) 900R3442009-103, 900R6442009-103, 900R3442009-101, or 500N5311-5, installed. This action requires:

Before further flight, for TT strap, P/N 900R3442009-103 and 900R6442009-103, reducing the life limit from 3034 to 2500 hours time-in-service (TIS);

Within 10 hours TIS, for any TT strap that has accumulated 1190 or more hours TIS, doing a visual and x-ray inspection of each TT strap and replacing any unairworthy part before further flight;

Before the TT strap accumulates 1200 hours TIS, for any TT strap with less than 1190 hours TIS, doing a visual and x-ray inspection of each strap and replacing any unairworthy part before further flight; and

Within 7 days, reporting information about any unairworthy TT strap to Roger Durbin, Aviation Safety Engineer, FAA, Los Angeles Aircraft Certification Office, Airframe Branch, 3960 Paramount Blvd., Lakewood, California 90712, telephone (562) 627-5233, fax (562) 627- 5210.

This amendment is prompted by two recent in-flight TT strap failures. The cause of the failures is not known at this time, and this AD is interim action. We will consider further rulemaking once our investigation is complete. The actions specified in this AD are intended to prevent failure of a TT strap resulting in loss of directional control and subsequent loss of control of the helicopter.

We have reviewed MD Helicopters Service Bulletin SB-900-095, dated November 3, 2004. The service bulletin advises of the reduction of the TT strap life limit and describes procedures for performing an inspection of each TT strap for nicks, cuts, cracks, or wear. Procedures for a Level II or higher X-Ray Technician to do and interpret an x-ray inspection of each TT strap for progressive fiber fractures are also included in the service bulletin.

This unsafe condition is likely to exist or develop on other helicopters of the same type design. Therefore, this AD is being issued to prevent failure of a TT strap resulting in loss of directional control and subsequent loss of control of the helicopter. This AD requires, before further flight, reducing the life limit of certain part-numbered TT straps. This AD also requires, depending on the hours accumulated on the TT strap, doing a visual and x-ray inspection within 10 hours TIS or before the accumulation of 1200 hours TIS and replacing any unairworthy part before further flight. Reporting the discovery of any unairworthy TT strap is also required. Accomplishing the inspections in accordance with the previously described service bulletin 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, reducing the TT strap life limit before further flight, inspecting each TT strap at the specified time interval, and reporting information about any unairworthy TT strap is required within 7 days, 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.

We estimate that this AD will affect 31 helicopters. It will take approximately 7 work hours for each inspection and replacement at an average labor rate of $65 per work hour. It will also cost $100 for each x-ray inspection. Required parts will cost approximately $757 per TT strap replacement. Based on these figures, we estimate the total cost impact of the AD on U.S. operators to be $40,672 (assuming a visual and x-ray inspection on each helicopter and a TT strap replacement on 8% of the fleet).

Comments Invited

This AD is a final rule that involves requirements that affect flight safety and was not preceded by notice and an opportunity for public comment; however, we invite you to submit any written data, views, or arguments regarding this AD. Send your comments to an address listed under ADDRESSES. Include "Docket No. FAA-2004-19613; Directorate Identifier 2004-SW-38-AD" at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the AD. We will consider all comments received by the closing date and may amend the AD in light of those comments.

We will post all comments we receive, without change, to http://dms.dot.gov , including any personal information you provide. We will also post a report summarizing each substantive verbal contact with FAA personnel concerning this AD. Using the search function of our docket web site, you can find and read the comments to any of our dockets, including the name of the individual who sent the comment. You may review the DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you may visit http://dms.dot.gov .

We have determined that this AD will not have federalism implications under Executive Order 13132. This AD will 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.

For the reasons discussed above, I certify that the 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. 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.

We prepared an economic evaluation of the estimated costs to comply with this AD. See the DMS to examine the economic evaluation.

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 to read as follows: