05-2608. Airworthiness Directives; MD Helicopters, Inc. Model 600N Helicopters

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes superseding an existing airworthiness directive (AD) for the MD Helicopters, Inc. (MDHI) Model 600N helicopters. That AD currently requires certain inspections of both upper tailboom attachments, nutplates, and angles for a crack or thread damage, and repairing or replacing any cracked or damaged part. Also, that AD requires replacing certain tailboom attachment bolts, adding a washer to each bolt, and modifying both upper access covers. This action would require installing six additional inspection holes in the aft fuselage skin panels and inspecting the upper and lower tailboom attachment fittings, the upper longerons, and the angles and nutplates for cracks. Also, the AD would provide a terminating action of modifying the fuselage aft section to strengthen the tailboom attachments and longerons. This proposal is prompted by an analysis that shows that certain tailboom attachments and longerons may develop cracks. The actions specified by the proposed AD are intended to prevent failure of a tailboom attachment, loss of the tailboom, and subsequent loss of control of the helicopter.

DATES:

Comments must be received on or before April 11, 2005.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Office of the Regional Counsel, Southwest Region, Attention: Rules Docket No. 2004-SW-16-AD, 2601 Meacham Blvd., Room 663, Fort Worth, Texas 76137. You may also send comments electronically to the Rules Docket at the following address: [e-mail]. Comments may be inspected at the Office of the Regional Counsel between 9 a.m. and 3 p.m., Monday through Friday, except Federal holidays.

FOR FURTHER INFORMATION CONTACT:

Fred Guerin, Aviation Safety Engineers, FAA, Los Angeles Aircraft Certification Office, Airframe Branch, 3960 Paramount Blvd., Lakewood, California 90712, telephone [phone], fax [phone].

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 will be considered before taking action on the proposed rule. The proposals contained in this document 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 proposal must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket No. 2004-SW-16-AD.” The postcard will be date stamped and returned to the commenter.

Discussion

On November 28, 2001, the FAA issued Emergency AD 2001-24-51 for MDHI Model 600N helicopters and issued the final rule; request for comments on April 2, 2002 (Amendment 39-12706 (67 FR 17934, April 12, 2002)). That AD requires implementing the procedures described in MD Helicopters, Inc. Service Bulletin SB600N-03, dated November 2, 2001 (SB600N-03), for inspecting both upper tailboom attachments, nutplates, and angles for a crack or thread damage and repairing or replacing damaged parts. In addition, if one bolt is broken, the AD requires replacing all four bolts. Also, adding a washer to each bolt and modifying both upper access covers as well as a 25-hour time-in-service (TIS) repetitive borescope inspection of the tailboom attachments, nutplates, and angles is required. That action was prompted by the discovery of cracked bolts and attachments on several helicopters. The requirements of that AD are intended to prevent failure of a tailboom attachment, loss of the tailboom, and subsequent loss of control of the helicopter.

Since issuing that AD, the FAA has reviewed an analysis by the manufacturer and has determined that the tailboom fittings, part number (P/N) 500N3422-BSC (BSC is interchangeable with basic) and -3, and the upper longerons, P/N 500N3120-3 and -4, will develop cracks due to the same design error as the current AD. Also, the FAA has reviewed MDHI Service Bulletin SB600N-039, dated December 9, 2003, which provides information pertaining to adding six inspection holes in the fuselage and certain inspections of the tailboom attachment fittings and upper longerons for cracks. Also, MDHI has issued Technical Bulletin TB 600N-007, dated January 12, 2004, which provides information pertaining to modifying the fuselage aft section to strengthen tailboom attachment fittings and longerons.

This previously described unsafe condition is likely to exist or develop on other helicopters of the same type design. Therefore, the proposed AD would supersede AD 2001-24-51 to require the following:

• Before further flight, drill an inspection hole at fuselage station L167 and R167 (L indicates Left and R indicates Right) on each side of the fuselage.
• Within 25 hours time-in-service (TIS):
• Drill two additional inspection holes on each side of the fuselage at L166, R166, L153, and R153.
• Visually inspect the lower attachment fittings and the upper longerons through inspection holes at L166, R166, L153 and R153, respectively.
• Thereafter, at specified intervals, remove the plug buttons from the inspection holes at L167, R167, L166, and R166. Using a bright light, inspect the attachment fittings, angles, and nutplates for a crack. Through inspection holes L153 and R153, using a bright light and mirror or borescope, visually inspect the bottom surface of each longeron for a crack.
• Before further flight, replace any cracked attachment fitting, angle, nutplate, longeron, and any nutplate with thread damage with an appropriate airworthy part.

This action proposes to require that operators modify the aft fuselage to strengthen the tailboom attachments and longeron within 4 years, which would constitute terminating action for the requirements of the AD.

The FAA estimates that this proposed AD would affect 39 helicopters of U.S. registry. The proposed actions would take about 322 work hours to modify and inspect the fuselage aft section per helicopter at an average labor rate of $65 per work hour. Required parts would cost approximately $14,960 per helicopter. Based on these figures, we estimate the total cost impact of the proposed AD on U.S. operators to be $1,399,710.

Regulatory Findings

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 economic 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.

Authority for this Rulemaking

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, Section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agency's authority.

We are issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701, “General requirements.” Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

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.

§ 39.13

[Amended]

2. Section 39.13 is amended by removing Amendment 39-12706 (67 FR 17934) and by adding a new airworthiness directive (AD), to read as follows:

MD Helicopters, Inc.: Docket No. 2004-SW-16-AD. Supersedes AD 2001-24-51, Amendment 39-12706, Docket No. 2001-SW-57-AD.

Applicability: Model 600N, serial numbers with a prefix of “RN” 003 through 066 and 068, that have not been modified by following the Accomplishment Instructions of MDHI Technical Bulletin TB600N-007, dated January 12, 2004, certificated in any category.

Compliance: Required as indicated.

To prevent failure of a tailboom attachment, loss of the tailboom, and subsequent loss of control of the helicopter, accomplish the following:

(a) Before further flight, unless accomplished previously, drill an inspection hole at fuselage station L167 and R167 (L indicates Left and R indicates Right) on each side of the fuselage by following the Accomplishment Instructions, paragraph 2.B.(6) of MD Helicopters, Inc. (MDHI) Service Bulletin SB600N-036, dated November 2, 2001.

(b) Within 25 hours time-in-service (TIS), unless accomplished previously:

(1) Drill two additional inspection holes (L166 and L153 on the left side and R166 and R153 on the right side) on each side of the fuselage as shown for the left side of the fuselage in Figure 1 of MDHI SB600N-039, dated December 9, 2003 (SB-039), by following the Accomplishment Instruction paragraphs of SB-039 as follows:

(i) Paragraphs 2.A.(1)(a), (b), and (d) for inspection holes at L166 and R166;

(ii) Paragraphs 2.A.(2)(a), (b), and (d) for inspection holes at L153 and R153; and

(2) Visually inspect for a crack by following the Accomplishment Instruction paragraphs of SB-039 at the following locations, except you are not required to contact MDHI.

(i) The lower left and right attachment fittings through inspection holes at L166 and R166, paragraph 2.A.(1)(c).

(ii) The upper left and right longerons through inspection holes at L153 and R153, paragraph 2.A.(2)(c).

Note:

The reference in Figure 1 of SB-039 to inspection hole at L167 mistakenly states that it was “Added by SB900-036.” Inspection holes at L167 and R167 were originally specified by SB600N-036.

(c) Thereafter, at the specified intervals, remove the plug buttons from the inspection holes, and using a bright light, inspect the upper left and upper right attachment fittings, angles, and nutplates for a crack by following the Accomplishment Instruction paragraphs of SB-039, as follows, except you are not required to contact MDHI.

(1) At intervals not to exceed 25 hours TIS, for inspection holes at L167 and R167, inspect the upper left and upper right attachment fittings, angles, and nutplates by following paragraphs 2.B.(2) through 2.B.(4).

(2) At intervals not to exceed 100 hours TIS, for inspection holes at L166 and R166, inspect the lower left and lower right attachment fittings, angles, and nutplates by following paragraphs 2.B.(2) through 2.B.(4).

(3) At intervals not to exceed 1200 hours TIS, for inspection holes L153 and R153 using a mirror or borescope, inspect the bottom surface of each longeron by following paragraphs 2.C.(2) and 2.C.(3).

(d) Before further flight, replace any cracked attachment fitting, angle, nutplate, longeron, and any nutplate with thread damage with an appropriate airworthy part.

(e) On or before 4 years from the effective date of this AD, modify the aft fuselage to strengthen the tailboom attachments and the longerons by following the Accomplishment Instructions of MDHI Technical Bulletin TB600N-007, dated January 12, 2004 (TB-007). Modifying the aft fuselage by following TB-007 constitutes terminating action for the requirements of this AD.

(f) 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 Office (LAACO), FAA, for information about previously approved alternative methods of compliance.

Issued in Fort Worth, Texas, on February 2, 2005.

David A. Downey,

Manager, Rotorcraft Directorate, Aircraft Certification Service.