AD 2008-20-05

This amendment supersedes an existing airworthiness directive (AD) for MD Helicopters, Inc. (MDHI) Model 600N helicopters. The AD currently requires modifying the fuselage aft section within the next 24 months to strengthen the tailboom attachment fittings and upper longerons. This amendment retains the current required modification and adds the following requirements: Repetitively inspecting the tailboom attachment fittings; installing inspection holes and attachment bolt washers; modifying both access covers; and replacing broken attachment bolts. These additional requirements were inadvertently omitted from the current AD. This amendment is prompted by the need to correct our mistake and continue the repetitive inspections of the tailboom attachment fittings until the fuselage aft section is modified. This series of ADs is prompted by an accident due to failure of the tailboom attach points resulting in loss of control of the helicopter. The actions specified by this AD areintended to prevent failure of the tailboom attachment fittings, separation of the tailboom from the helicopter, and subsequent loss of control of the helicopter.

Final rule; request for comments.

2008-20-05 MD Helicopters, Inc.: Amendment 39-15684. Docket No. FAA-2008-0834; Directorate Identifier 2008-SW-34-AD. Supersedes AD 2008-05-17, Amendment 39-15411, Docket No. FAA-2007-29342, Directorate Identifier 2007-SW-08-AD.

Applicability: Model 600N helicopters, serial numbers with a prefix "RN" and 003 through 058, that have not been modified in the fuselage aft section to strengthen the tailboom attachments and longerons per MD Helicopters (MDHI) Technical Bulletin (TB) TB600N- 007, dated January 12, 2004; TB600N-007, Revision 1, dated April 13, 2006; or TB600N-007, Revision 2, dated October 5, 2006, certificated in any category.

Compliance: Required as indicated.
To prevent failure of the tailboom attachment fittings, separation of the tailboom from the helicopter, and subsequent loss of control of the helicopter, do the following:

Note 1: There is a slight discrepancy between MD Helicopters, Inc. Service Bulletin SB600N-036, dated November 2, 2001 (SB600N- 036) and MD Helicopters Service Bulletin SB600N-039, dated December 9, 2003 (SB600N-039) on the vertical location of the upper left inspection hole. Either location is acceptable for this AD.

(a) Within 5 hours time-in-service (TIS), unless accomplished previously:
(1) Remove the tailboom fairing and tailboom. Remove both upper tailboom attachment access covers in accordance with the Accomplishment Instructions, paragraph 2.B.(2) of SB600N-036.

Note 2: MDHI CSP-HMI-2, Section 53-40-30, pertains to the subject of this AD.

(2) Using a light and a 10x or higher magnifying glass:
(i) Inspect the right and left upper tailboom attachment fittings, part number (P/N) 500N3422 and 500N3422-3, respectively, for a crack as shown in Figure 1 of SB600N-036. If a crack is found, replace any cracked attachment fitting with an airworthy attachment fitting before further flight.
(ii) Inspect both upper tailboom attachment nut plates for thread damage or a crack. Replace any damagedor cracked nut plate with an airworthy nut plate before further flight.
(iii) Inspect both angles for a crack. If a crack is found on a right-hand angle, P/N 500N3429-6, before further flight, install a new clip in accordance with the Accomplishment Instructions, paragraph 2.B.(5)(c) of SB600N-036. If a crack is found on the left- hand angle, P/N 500N3429-7, before further flight, replace the angle with an airworthy angle, or repair the angle in accordance with FAA- approved procedures.
(3) Replace the upper right (pilot side) tailboom attachment bolt (bolt) with a new bolt.
(4) If the removed upper right pilot-side bolt is broken, replace the remaining three bolts with airworthy bolts before further flight.
(5) Add one washer, P/N AN960C516 (NAS1149C0563R) or AN960C616 (NAS1149C0663R), as appropriate, to each tailboom bolt between the tailboom and the NAS1587 countersunk washer. A minimum of two threads must extend past the nut plate.
(6) Modify both access covers in accordance with the Accomplishment Instructions, paragraph 2.B.(6), of SB600N-036.

(b) Within 5 hours TIS, unless accomplished previously:
(1) Drill four additional inspection holes in the fuselage as shown for the left side of the fuselage in Figure 1 of SB600N-039, by following the Accomplishment Instruction paragraphs of SB600N-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.
(2) Thoroughly clean the attachment fittings and surrounding area. If the attachment fittings and surrounding area cannot be satisfactorily cleaned to accomplish a borescope inspection, then accomplish the actions in paragraph (c) of this AD.
(3) Using a lighted borescope, inspect all four attachment fittings and the surrounding area for cracking.
(i) If a crack is found in the upper right attachment fitting, accomplish the actions in paragraph (c) of this AD.
(ii) If a crack is found in any of the other three attachment fittings, before further flight, accomplish the actions described in paragraph (f) of this AD.
(4) Visually inspect the upper longerons for cracking in accordance with the Accomplishment Instructions, paragraph 2.C., of SB600N-039. If a crack is found in the upper longeron, accomplish the actions in paragraph (e) of this AD.

Note 3: The reference in Figure 1 of SB600N-039 to the 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) Within 25 hours TIS, unless accomplished previously:
(1) Thoroughly clean all attachment fittings and the surrounding areas, inspect the area for cracking, replace the upper right attachment fitting and all four nut plates, and paint the area inside of the attachment fittings in accordance with the Accomplishment Instructions, paragraph 2.B., of MD Helicopters Service Bulletin SB600N-043, dated April 13, 2006 (SB600N-043). If a crack is found in any of the other three attachment fittings, before further flight, accomplish the actions described in paragraph (f) of this AD.
(2) Using a 10x magnifying glass, inspect the attachment bolts' threads and shanks for wear or damage in accordance with paragraph 2.B., of SB600N-043. If wear or damage is present, replace the attachment bolts with airworthy bolts.

(d) Thereafter, at the specified intervals, remove the plug buttons from the inspection holes, and using a bright light, inspect the upper and lower left and upper and lower right attachment fittings, angles, and nut plates for a crack by following the Accomplishment Instruction paragraphs of SB600N-039, as follows, except you are not required to contact MDHI to meet the requirements of this AD.
(1) At intervals not to exceed 25 hours TIS, through inspection holes at L167 and R167, inspect the upper left and upper right attachment fittings, angles, and nut plates by following the Accomplishment Instructions, paragraphs 2.B.(2) through 2.B.(4), of SB600N-039.
(2) At intervals not to exceed 100 hours TIS, through inspection holes at L166 and R166, inspect the lower left and lower right attachment fittings, angles, and nut plates by following the Accomplishment Instructions, paragraphs 2.B.(2) through 2.B.(4), of SB600N-039.

(e) If a crack is found in the upper right attachment fitting, or in any angle, nut plate, longeron, or if thread wear or damage is found on any nut plate or bolt, before further flight, replace the cracked or worn or damaged part with an appropriate airworthy part, or accomplish the actions in paragraph (f) of this AD. If cracking is found in any of the other three attachment fittings, before further flight, accomplish the actions described in paragraph (f) of this AD.

(f) If required by paragraph (c)(1) of this AD, or if you make this modification to comply with paragraph (e) of this AD, modify the fuselage aft section to strengthen the tailboom attachments and the upper longerons by following paragraph 2, Accomplishment Instructions, of MDHI TB600N-007, dated January 12, 2004; TB600N- 007, Revision 1, dated April 13, 2006; or TB600N-007, Revision 2, dated October 5, 2006; except you are not required to contact the manufacturer. This modification to the fuselage aft section is terminating action for the requirements of this AD.

(g) Within 24 months, modify the fuselage aft section to strengthen the tailboom attachments and upper longerons by following paragraph 2, Accomplishment Instructions, of MDHI TB600N-007, Revision 2, dated October 5, 2006, except you are not required to contact the manufacturer. This modification to the fuselage aft section is terminating action for the requirements of this AD.

(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 Manager, Los Angeles Aircraft Certification Office, Airframe Branch, FAA, ATTN: Eric Schrieber, Aviation Safety Engineer, 3960 Paramount Blvd., Lakewood, California 90712, telephone (562) 627-5348, fax (562) 627-5210, for information about previously approved alternative methods of compliance.

(i) Inspect, replace, and modify the fuselage aft section according to the specified portions of the following MD Helicopters service information, as applicable.
(1) Service Bulletin SB600N-036, dated November 2, 2001; incorporated by reference as of April 29, 2002 (67 FR 17934, April 12, 2002).
(2) Service Bulletin SB600N-039, dated December 9, 2003; Service SB600N-043, dated April 13, 2006; and Technical Bulletin TB600N-007, Revision 1, dated April 13, 2006; incorporated by reference as of April 27, 2006 (71 FR 24808, April 27, 2006).
(3) Technical Bulletin TB600N-007, Revision 2, dated October 5, 2006; incorporated by reference as of April 16, 2008 (73 FR 13096, March 12, 2008).
(4) The incorporation by reference of these documents was approved previously by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51.
(5) Copies of this service information may be obtained from MD Helicopters Inc., Attn: Customer Support Division, 4555 E. McDowell Rd., Mail Stop M615, Mesa, Arizona 85215-9734, telephone 1-800-388- 3378, fax 480-346-6813, or on the Internet at http:// www.mdhelicopters.com.
(6) 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 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 October 27, 2008.

On February 27, 2008, we issued AD 2008-05- 17, Amendment 39-15411 (73 FR 13096, March 12, 2008), to supersede AD 2006-08-12, Amendment 39-14569 (71 FR 24808, April 27, 2006), which superseded AD 2001-24-51, Amendment 39-12706 (67 FR 17934, April 12, 2002), for the MDHI Model 600N helicopters. AD 2008-05-17 required modifying the fuselage aft section within the next 24 months to strengthen the tailboom attachment fittings and upper longerons. AD 2001-24-51 was prompted by the discovery of a cracked bolt. AD 2006-08- 12 was prompted by an accident due to failure of the tail boom attach points resulting in loss of control of the helicopter. That condition, if not corrected, could result in failure of the tailboom attachment fittings, separation of the tailboom from the helicopter, and subsequent loss of control of the helicopter.
Since issuing AD 2008-05-17, we discovered that we inadvertently omitted the requirements from AD 2006-08-12 to repetitively inspect the tailboom attachment fittings; install inspection holes and attachment bolt washers; modify both access covers; and replace broken attachment bolts. Since the compliance time in AD 2008-05-17 for modifying the fuselage aft section is 24 months, this results in a 24-month period of time for which the helicopters would not be subject to the actions contained in AD 2006-08-12, which was not our intention. The accident that prompted these ADs may have resulted from failure of the thread engagement between the nut plate and bolt or by cracking in the attachment bathtub ring. Therefore, the tailboom attachment fittings and upper longerons must be inspected at 25- and 100-hour time-in- service (TIS) intervals to detect any unairworthy parts and prevent failure of the tailboom attachment fittings, separation of the tailboom from the helicopter, and subsequent loss of control of the helicopter.
Since an unsafe condition has been identified that is likely to exist or develop on other MDHI Model 600N helicopters of the same type design, this AD supersedes AD 2008-05-17 to reinstate certain actions related to the tailboom attachment fittings inadvertently omitted from the current AD and to continue to require the modification of the fuselage aft section within 24 months. The inspections and modification must be accomplished by following the specified portions of the service bulletins.
The short compliance time involved is required because the previously described critical unsafe condition can adversely affect the structural integrity and the controllability of the helicopter. The inspections are required at 25 and 100-hours time-in-service (TIS). We consider that the 100-hour TIS inspection is a relatively short interval because some of the affected helicopters may reach those hours within 2 months. Therefore, this AD must be issued immediately to reinstate the previous requirements related to the tailboom attachment fittings.
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 18 helicopters and will take about 322 work hours to modify each helicopter and will require about 1 work hour to do a repetitive inspection with 24 inspections per helicopter per year at an average labor rate of $80 per work hour. Required parts will cost about $14,960 per helicopter. Based on these figures and assuming 24 repetitive inspections per helicopter per year for 2 years until the modification is required, we estimate the total cost impact of the AD on U.S. operators to be $802,080.

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-2008-0834; Directorate Identifier 2008-SW-34-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:// www.regulations.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).

Regulatory Findings

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 AD docket to examine the economic evaluation.

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, Incorporation by reference, Safety.

Adoption of the Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal AviationAdministration 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.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by removing Amendment 39-15411 (73 FR 13096, March 12, 2008), and by adding a new airworthiness directive (AD), Amendment 39-15684, to read as follows: