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###### Department of Transportation

###### Federal Aviation Administration

          - 14 CFR Part 39
          - [Docket No. FAA-2010-0953; Directorate Identifier 2010-NM-010-AD]
          - RIN 2120-AA64

# AGENCY:

Federal Aviation Administration (FAA), DOT.

# ACTION:

Notice of proposed rulemaking (NPRM).

# SUMMARY:

We propose to adopt a new airworthiness directive (AD) for all Model MD-90-30 airplanes. This proposed AD would require repetitive high frequency eddy current inspections for cracking on the hinge bearing lugs of the left and right sides of the center section ribs of the horizontal stabilizer, and related investigative and corrective actions if necessary. This proposed AD results from reports of cracks found on either the left or right (or in one case, both) sides of the center section ribs of the horizontal stabilizer. We are proposing this AD to detect and correct cracking in the hinge bearing lugs of the center section of the left and right ribs, which could result in failure of the hinge bearing lugs and consequent inability of the horizontal stabilizer to sustain the required loads.

# DATES:

We must receive comments on this proposed AD by November 15, 2010.

# ADDRESSES:

You may send comments by any of the following methods:
      -  Federal eRulemaking Portal:                          Go to                          http://www.regulations.gov.                          Follow the instructions for submitting comments.                    
      -  Fax:                          202-493-2251.                    
      -  Mail:                          U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590.                    
      -  Hand Delivery:                          U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.                    

                        For service information identified in this proposed AD, contact Boeing Commercial Airplanes, Attention: Data & Services Management, 3855 Lakewood Boulevard, MC D800-0019, Long Beach, California 90846-0001; telephone 206-544-5000, extension 2; fax 206-766-5683; e-mail                         *dse.boecom@boeing.com;*                         Internet                         *https://www.myboeingfleet.com.*                         You may review copies of the referenced service information at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington. For information on the availability of this material at the FAA, call 425-227-1221.                    

## Examining the AD Docket

                    You may examine the AD docket on the Internet at                     *http://www.regulations.gov;*                     or in person at the Docket Management Facility between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this proposed AD, the regulatory evaluation, any comments received, and other information. The street address for the Docket Office (telephone 800-647-5527) is in the                     **ADDRESSES**                     section. Comments will be available in the AD docket shortly after receipt.                

# FOR FURTHER INFORMATION CONTACT:

Roger Durbin, Aerospace Engineer, Airframe Branch, ANM-120L, FAA, Los Angeles Aircraft Certification Office (ACO), 3960 Paramount Boulevard, Lakewood, California 90712-4137; telephone (562) 627-5233; fax (562) 627-5210.

# SUPPLEMENTARY INFORMATION:

## Comments Invited

                    We invite you to send any written relevant data, views, or arguments about this proposed AD. Send your comments to an address listed under the                     **ADDRESSES**                     section. Include “Docket No. FAA-2010-0953; Directorate Identifier 2010-NM-010-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of this proposed AD. We will consider all comments received by the closing date and may amend this proposed AD because 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 we receive about this proposed AD.                          ( print page 60666)    

## Discussion

We have received seven reports of cracks found on either the left or right (or in one case, both) sides of the center section ribs of the horizontal stabilizer. These cracks were located on the aft face of the hinge bearing lugs on the horizontal stabilizer. Cracks were reported on MD-90 airplanes that had accumulated 9,051 to 21,183 total flight hours, and 8,939 to 20,893 total flight cycles. The cause of the cracking has not been determined. Undetected cracking in the hinge bearing lugs of the center section of the left and right ribs, if not corrected, could result in failure of the hinge bearing lugs and consequent inability of the horizontal stabilizer to sustain the required loads.

## Relevant Service Information

We have reviewed Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010. Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010, describes procedures for doing repetitive high frequency eddy current (HFEC) inspections for cracking on the hinge bearing lugs on the aft face of the horizontal stabilizer center section on the left and right ribs, and doing applicable related investigative and corrective actions. The related investigative action is measuring the crack length. The corrective actions include blending out cracks and replacing the rib of the center section of the horizontal stabilizer. For airplanes on which a blend out is done, Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010, describes procedures for doing repetitive HFEC inspections for cracking of the blend out. For airplanes on which the replacement is done, Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010, describes procedures for doing repetitive HFEC inspections for cracking of the replaced horizontal stabilizer rib.

For the initial HFEC inspection, Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010, specifies a compliance time of before the accumulation of 7,200 total flight cycles or within 1,505 flight cycles after the original issue date of Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010, whichever occurs later.

## FAA's Determination and Requirements of This Proposed AD

We are proposing this AD because we evaluated all relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of the same type design. This proposed AD would require accomplishing the actions specified in the service information described previously, except as discussed under “Differences Between the Proposed AD and Service Bulletin.”

## Differences Between the Proposed AD and Service Bulletin

For Condition 2A specified in Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010, the service bulletin specifies doing repetitive inspections of the blend out but did not identify corrective actions when cracks are found during those inspections. This proposed AD would require replacing the horizontal stabilizer center section rib when cracks are found during inspections of the blend out. We have coordinated this difference with Boeing.

For Condition 2B specified in Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010, the service bulletin specifies doing repetitive inspections of the replaced horizontal stabilizer center section rib at intervals not to exceed 1,680 flight cycles. This proposed AD would require doing an inspection of the replaced horizontal stabilizer center section rib and all applicable corrective actions and repetitive inspections (for Condition 1, the repetitive interval is 1,680 flight cycles; for Condition 2A, the repetitive interval is 400 flight cycles).

## Interim Action

We consider this proposed AD interim action. The manufacturer is currently developing a modification that will address the unsafe condition identified in this AD. Once this modification is developed, approved, and available, we might consider additional rulemaking.

## Costs of Compliance

We estimate that this proposed AD would affect 16 airplanes of U.S. registry. We also estimate that it would take about 2 work-hours per product to comply with this proposed AD. The average labor rate is $85 per work-hour. Based on these figures, we estimate the cost of this proposed AD to the U.S. operators to be $2,720, or $170 per product.

## 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.

## Regulatory Findings

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

*For the reasons discussed above, I certify 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. 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.

You can find our regulatory evaluation and the estimated costs of compliance in the AD Docket.

# List of Subjects in 14 CFR Part 39

      - Air transportation
      - Aircraft
      - Aviation safety
      - Incorporation by reference
      - Safety

## The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 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 

2. The FAA amends § 39.13 by adding the following new AD:

**McDonnell Douglas Corporation:**                                 Docket No. FAA-2010-0953; Directorate Identifier 2010-NM-010-AD.                                      ( print page 60667)    

## Comments Due Date

(a) We must receive comments by November 15, 2010.

## Affected ADs

(b) None.

## Applicability

(c) This AD applies to all McDonnell Douglas Corporation Model MD-90-30 airplanes, certificated in any category.

## Subject

(d) Air Transport Association (ATA) of America Code 55: Stabilizers.

## Unsafe Condition

(e) This AD results from reports of cracks found on either the left or right (or in one case, both) sides of the center section ribs of the horizontal stabilizer. The Federal Aviation Administration is issuing this AD to detect and correct cracking in the hinge bearing lugs of the center section of the left and right ribs, which could result in failure of the hinge bearing lugs and consequent inability of the horizontal stabilizer to sustain the required loads.

## Compliance

(f) You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.

## Repetitive Inspections and Corrective Actions for Cracking

(g) At the applicable time in paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010, except as required by paragraph (n) of this AD, do a high frequency eddy current (HFEC) inspection for cracking on the hinge bearing lugs of the left and right sides of the center section ribs of the horizontal stabilizer, and do all applicable related investigative actions, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010. Do all applicable related investigative actions before further flight.

(h) If during any inspection required by paragraph (g) of this AD, no cracking is found, repeat the inspection required by paragraph (g) of this AD thereafter at intervals not to exceed 1,680 flight cycles.

(i) If during any inspection required by paragraph (g) or (h) of this AD, any crack is found having a length between Points ‘A’ and ‘B’ less than or equal to 0.15 inch and crack length between Points ‘C’ and ‘D’ less than or equal to 0.05 inch, as identified in Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010: Before further flight, blend out the crack; and within 1,000 flight cycles after doing the blend out, do an HFEC inspection of the blend out on the center section rib hinge bearing lug; in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010. Repeat the HFEC inspection of the blend out thereafter at intervals not to exceed 400 flight cycles until the replacement specified by paragraph (j) is done.

(j) If any cracking is detected during any inspection required by paragraph (i) of this AD, before further flight, replace the horizontal stabilizer center section rib with a new horizontal stabilizer center section rib, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010.

(k) If during any inspection required by paragraph (g) or (h) of this AD, any crack is found having a length between Points ‘A’ and ‘B’ greater than 0.15 inch or crack length between Points ‘C’ and ‘D’ greater than 0.05 inch, as identified in Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010: Before further flight, replace the horizontal stabilizer center section rib with a new horizontal stabilizer center section rib, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010.

(l) For any airplane having a horizontal stabilizer center section rib replaced during the actions required by paragraph (j) or (k) of this AD: Before the accumulation of 7,200 total flight cycles on the new horizontal stabilizer center section rib, do the actions required by paragraph (g) of this AD, and do all applicable actions specified in paragraphs (h), (i), (j), and (k) of this AD.

## Credit for Actions Accomplished According to Previous Issue of Service Bulletin

(m) Actions accomplished before the effective date of this AD according to Boeing Alert Service Bulletin MD90-55A016, dated December 16, 2009, are considered acceptable for compliance with the corresponding actions required by paragraphs (g), (h), (i), (j), and (k) of this AD.

## Exceptions to the Service Bulletin

(n) Where Boeing Alert Service Bulletin MD90-55A016, Revision 1, dated February 17, 2010, specifies a compliance time “after the original issue date on the service bulletin,” this AD requires compliance within the specified compliance time after the effective date of this AD.

## Alternative Methods of Compliance (AMOCs)

(o)(1) The Manager, Los Angeles ACO, FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. Send information to ATTN: Roger Durbin, Aerospace Engineer, Airframe Branch, ANM-120L, FAA, Los Angeles Aircraft Certification Office (ACO), 3960 Paramount Boulevard, Lakewood, California 90712-4137; telephone (562) 627-5233; fax (562) 627-5210.

(2) To request a different method of compliance or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. Before using any approved AMOC on any airplane to which the AMOC applies, notify your principal maintenance inspector (PMI) or principal avionics inspector (PAI), as appropriate, or lacking a principal inspector, your local Flight Standards District Office. The AMOC approval letter must specifically reference this AD.

(3) An AMOC that provides an acceptable level of safety may be used for any repair required by this AD if it is approved by the Boeing Commercial Airplanes Organization Designation Authorization (ODA) that has been authorized by the Manager, Los Angeles ACO to make those findings. For a repair method to be approved, the repair must meet the certification basis of the airplane, and the approval must specifically refer to this AD.

Issued in Renton, Washington, on September 23, 2010.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.

[FR Doc. 2010-24715 Filed 9-30-10; 8:45 am]

BILLING CODE 4910-13-P