### 80738 Federal Register / Vol. 75, No. 246 / Thursday, December 23, 2010 / Proposed Rules

(3) No uncommanded lateral or directional motion, and the pilot must retain good lateral and directional control by conventional use of the cockpit controls throughout the

maneuver.

(4) The airplane must not exhibit buffeting of a magnitude or severity that would act as a deterrent to completing the maneuver specified in § 25.201(a) as amended by this proposed special condition.

(b) In maneuvers with increased rates of deceleration, some degradation of characteristics associated with a transient excursion beyond the stabilized alpha-limit is acceptable. However, the airplane must not exhibit dangerous characteristics or characteristics that would deter the pilot from holding the longitudinal control on the aft stop for a period of time appropriate to the maneuvers.

(c) It must always be possible to reduce incidence by conventional use of the longitudinal control.

(d) The rate at which the airplane can be maneuvered from trim speeds associated with scheduled operating speeds, such as V 2 and V REF up to alphalimit, should not be unduly damped or significantly slower than can be achieved on conventionally controlled transport airplanes.

7. Atmospheric Disturbances— Operation of the high incidence protection function must not adversely affect aircraft control during expected levels of atmospheric disturbances, nor impede the application of recovery procedures in case of windshear. Simulator tests and analysis may be used to evaluate such conditions, but must be validated by limited flight testing to confirm handling qualities at critical loading conditions.

8. Longitudinal Control—In lieu of the requirements of § 25.145(a), (a)(1) and (b)(6), the following special conditions are proposed:

(a) It must be possible, at any point between the trim speed prescribed in § 25.103(b)(6) as amended by this proposed special condition and Vmin, to pitch the nose downward so that the acceleration to this selected trim speed is prompt.

(b) With the landing gear extended, no change in trim control, or exertion of more than 50 pounds control force(representative of the maximum shortterm force that can be applied readily by one hand) may be required for the following maneuver: With power off, flaps extended and the airplane trimmed at 1.3 V SR1 , obtain and maintain airspeeds between Vmin and either 1.6V SR1 or VFE , whichever is lower. 9. Airspeed Indicating System—In lieu of § 25.1323(c)(1) and (c)(2), the following special conditions are proposed:

(a) VMO to Vmin with the flaps retracted; and

(b) Vmin to VFE with flaps in the landing position.

Issued in Renton, Washington, on December 13, 2010. Ali Bahrami, Manager, Transport Airplane Directorate, Aircraft Certification Service.
[FR Doc. 2010–32236 Filed 12–22–10; 8:45 am]

**BILLING CODE 4910–13–P**

**DEPARTMENT OF TRANSPORTATION**

**Federal Aviation Administration**

**14 CFR Part 39**

**[Docket No. FAA–2008–0847; Directorate Identifier 2008–NM–056–AD]** 

**RIN 2120–AA64**

**Airworthiness Directives; The Boeing Company Model 777–200, –200LR,**  **–300, and –300ER Series Airplanes**

**AGENCY :**  Federal Aviation Administration (FAA), DOT.

**ACTION :**  Supplemental notice of proposed rulemaking (NPRM); reopening of comment period.

**SUMMARY :**  We are revising an earlier proposed airworthiness directive (AD) for certain Model 777–200, –200LR, –300, and –300ER series airplanes. The original NPRM would have required doing an inspection to identify the part number of the motor operated valve (MOV) actuators of the main and center fuel tanks; replacing certain MOV actuators with new MOV actuators; and measuring the electrical resistance of the bond from the adapter plate to the airplane structure, and doing corrective actions if necessary. The original NPRM also would have required revising the Airworthiness Limitations section of the Instructions for Continued Airworthiness. The original NPRM resulted from fuel system reviews conducted by the manufacturer. This action revises the original NPRM by adding airplanes to the applicability. This action also revises the original NPRM by removing the requirement for revising the Airworthiness Limitations section of the Instructions for Continued Airworthiness. We are proposing this supplemental NPRM to prevent electrical current from flowing through an MOV actuator into a fuel tank, which could create a potential ignition source inside the fuel tank. This condition, in combination with flammable fuel vapors, could result in a fuel tank explosion and consequent loss of the airplane.

**DATES :**  We must receive comments on this supplemental NPRM by January 18,
2011.

**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, P. O. Box 3707, MC 2H–65, Seattle, Washington 98124– 2207; telephone 206–544–5000, extension 1; fax 206–766–5680; e-mail me.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 :**  Tak Kobayashi, Aerospace Engineer, Propulsion Branch, ANM–140S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057–3356; telephone (425) 917–6499; fax (425) 917–6590.

**SUPPLEMENTARY INFORMATION :** 


### 80739 Federal Register / Vol. 75, No. 246 / Thursday, December 23, 2010 / Proposed Rules

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–2008–0847; Directorate Identifier 2008–NM–056–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.

Discussion

We issued a notice of proposed rulemaking (NPRM) (the ‘‘ original NPRM ’’ ) to amend 14 CFR part 39 to include an airworthiness directive (AD) that would apply to certain Model 777– 200, –200LR, –300, and –300ER series airplanes. That original NPRM was published in the Federal Register on August 7, 2008 (73 FR 45893). That original NPRM proposed to require doing an inspection to identify the part number of the motor operated valve (MOV) actuators of the main and center fuel tanks; replacing certain MOV actuators with new MOV actuators; and measuring the electrical resistance of the bond from the adapter plate to the airplane structure, and doing corrective actions if necessary. The original NPRM also would have required revising the Airworthiness Limitations section of the Instructions for Continued Airworthiness (ICA). Actions Since Original NPRM Was Issued

Since we issued the original NPRM, the manufacturer has informed us that certain airplanes were missing from the effectivity in Boeing Alert Service Bulletin 777–28A0034, dated August 2, 2007, which was referenced in the original NPRM as the appropriate source of service information.

In addition, since we issued the original NPRM, we have determined that the proposed requirement for revising the Airworthiness Limitations (AWL) section of the ICA is unnecessary. Incorporation of AWL No. 28–AWL–19 and AWL No. 28–AWL–20 is already mandated by AD 2008–11–13, Amendment 39–15536 (73 FR 30737, May 29, 2008), which is applicable to Model 777–200, –200LR, –300, and –300ER series airplanes. Therefore, we have removed Note 1 and paragraphs (h), (i), and (j) from the original NPRM.

Relevant Service Information

Since the issuance of the original NPRM, we reviewed Boeing Alert Service Bulletin 777–28A0034, Revision 1, dated May 20, 2010, which adds airplanes to the effectivity, and corrects an MOV actuator part number. We also reviewed Boeing Service Bulletin 777– 28A0034, Revision 2, dated September 20, 2010, which specifies to cap seal the bonding jumper fasteners when installing the MOV actuator. Boeing Service Bulletin 777–28A0034, Revision 2, dated September 20, 2010, specifies that no more work is necessary on airplanes modified in accordance with Boeing Alert Service Bulletin 777– 28A0034, dated August 2, 2007; and Revision 1, dated May 20, 2010.

We have revised paragraphs (c), (g), and (h) of this supplemental NPRM to refer to Boeing Service Bulletin 777– 28A0034, Revision 2, dated September 20, 2010. In addition, we have added new paragraph (j) to this supplemental NPRM to provide credit for actions accomplished before the effective date of this AD in accordance with Boeing Alert Service Bulletin 777–28A0034, dated August 2, 2007; and Revision 1, dated May 20, 2010.

Comments

We gave the public the opportunity to participate in developing this AD. We considered the comments received from the two commenters. Request To Use Later Revisions of the Maintenance Planning Data (MPD) Document

Boeing, and Air Transport Association (ATA) on behalf of its member United Airlines (UAL), requested that the FAA reference later revisions of the MPD document in paragraph (h) of the original NPRM.

As stated previously, we have removed paragraph (h) (the requirement to revise the AWL section of the ICA) of the original NPRM. Therefore, no revision to this supplemental NPRM is necessary in this regard.

Allow the Use of Later Revisions of Alternative Critical Design Configuration Control Limitations (CDCCLs)

ATA, on behalf of its member UAL, stated that paragraph (i) of the original NPRM should include instructions similar to those in paragraph (i) of AD 2008–11–13, which allows operators to use alternative ‘‘ CDCCLs that are part of a later revision of February 2008 of the MPD ’’ that is approved by the FAA to avoid confusion and to promote common compliance rules.

As stated previously, we have removed paragraph (i) of the original NPRM. Therefore, no revision to this supplemental NPRM is necessary in this regard. Request To Revise the Costs of Compliance

Boeing, and ATA on behalf of its member UAL, requested that we revise the Costs of Compliance section in the original NPRM to include the cost of parts. ATA stated that the cost of parts presents a significant expense to the operators since there are 11 MOV actuators on each of the 197 airplanes affected by the original NPRM, costing $5,477 per actuator. Boeing stated that the cost of parts is substantial and, when accounted alongside with the cost of labor, estimated work-hours, and the total number of affected airplanes, the cost would be higher than what is stated in the original NPRM.

We agree to include the cost of parts in this supplemental NPRM. We have revised the Costs of Compliance section accordingly. Request To Clarify the Accomplishment Instructions in the Service Bulletin

ATA, on behalf of its member UAL, requested clarification of the Accomplishment Instructions in Boeing Alert Service Bulletin 777–28A0034, dated August 2, 2007. UAL asserted that the logical flow ( ‘‘ if—then ’’ condition) of the installation instructions is incomplete and can be further clarified. UAL also stated that certain Boeing 777 aircraft maintenance manuals referenced as sources of guidance in Boeing Alert Service Bulletin 777– 28A0034, dated August 2, 2007, have two sections, ‘‘Pre ’’ and ‘‘Post’’ Boeing Alert Service Bulletin 777–28A0034, and that the service bulletin should specify which section is applicable.

We agree with UAL that some of the instructions in Boeing Alert Service Bulletin 777–28A0034, dated August 2, 2007, are unclear. Those issues have been clarified in Boeing Alert Service Bulletin 777–28A0034, Revision 1, dated May 20, 2010; and Boeing Service Bulletin 777–28A0034, Revision 2, dated September 20, 2010. As stated previously, we have revised this supplemental NPRM to refer to Boeing Service Bulletin 777–28A0034, Revision 2, dated September 20, 2010, and to provide credit for accomplishment of Boeing Alert Service Bulletins 777– 28A0034, dated August 2, 2007, and to


### 80740 Federal Register / Vol. 75, No. 246 / Thursday, December 23, 2010 / Proposed Rules

Revision 1, dated May 20, 2010, before the effective date of the AD. Request To Prohibit the Installation of Part Number (P/N) MA20A1001–1

ATA, on behalf of its member UAL, expressed that the intent of the original NPRM is to remove the MOV actuator having P/N MA20A1001–1 and to prohibit installation of P/N MA20A1001–1 once the AD has been complied with. UAL stated that it has reviewed the NPRM and cannot find language that prohibits the installation of P/N MA20A1001–1; UAL stated that such language should be in this proposed AD.

We partially agree. We disagree that it is necessary to specifically prohibit the installation of P/N MA20A1001–1 once the AD has been complied with because after accomplishing the mandatory actions, operators are required to maintain airplanes in compliance with the AD. To ensure that the unsafe condition cannot be introduced before compliance with the AD, we have added paragraph (i) to this supplemental NPRM to prohibit installation of an MOV actuator, P/N MA20A1001–1, after the effective date of this AD. Request To Postpone the AD or Extend the Compliance Time

ATA, on behalf of its member UAL, requested that the FAA postpone the proposed AD or extend the compliance time until reliability issues pertaining to the MOV actuator with P/N MA30A1001 are resolved. UAL stated that Boeing Fleet Team Digest 737NG– FTD–28–07002 discusses the potential of the P/N MA30A1001 actuator having cracked or damaged capacitors. UAL stated that if the MOV actuators with the defective design are installed due to regulatory mandate, the opportunity of actuator failure is introduced, which creates unnecessary economic burden for operators. We disagree with UAL’s request to postpone the AD or extend the compliance time. The problem of the capacitor does not constitute a new unsafe condition. The investigation conducted by the supplier of the affected MOV actuators concluded that damage to the capacitors was introduced due to certain manufacturing processes. To address this issue, the supplier changed manufacturing processes in March 2007. We are aware that a number of MOV actuators that were produced under the manufacturing processes before that change were returned to the supplier between December 2006 and October 2007. Boeing also informed us that no actuators have been returned to the supplier due to damaged capacitors since October 2007. We have determined that the manufacturing process changes have adequately addressed the reliability issues; therefore, the current inventory of spare MOV actuators would be unlikely to contain a discrepant part. We consider it inappropriate to delay this AD since we have determined that an unsafe condition exists and that replacement of certain parts must be accomplished to ensure continued safety. We have not changed this supplemental NPRM in this regard. FAA’s Determination and Proposed Requirements of the Supplemental NPRM

We are proposing this supplemental NPRM because we evaluated all pertinent information and determined an unsafe condition exists and is likely to exist or develop on other products of the same type design. Certain changes described above expand the scope of the original NPRM. As a result, we have determined that it is necessary to reopen the comment period to provide additional opportunity for the public to comment on this supplemental NPRM. Additional Changes to the Original NPRM

In the Costs of Compliance section in the original NPRM, 197 airplanes were estimated to be affected. The correct number of affected airplanes in this supplemental NPRM is 127 airplanes. We have revised the Costs of Compliance section accordingly.

We have determined that a review of airplane records will be adequate to identify the MOV actuator part number. Therefore, we have added a records review as an option to the inspection in paragraph (g) of this supplemental NPRM (paragraph (f) in the original NPRM).

We have revised paragraph (h) of this supplemental NPRM (paragraph (g)(1) in the original NPRM) to specify the correct replacement actuator part number. We have also revised paragraph (h) of this supplemental NPRM to allow the installation of a serviceable MOV actuator. In addition, we have revised paragraph (h) of this supplemental NPRM to clarify that measuring the electrical resistance of the bond from the adapter plate is only required at certain MOV actuator locations.

We have added a new paragraph (d) to this supplemental NPRM to provide the Air Transport Association of America (ATA) Code 28, Fuel. This code is added to make this supplemental NPRM parallel with other new AD actions. We have reidentified subsequent paragraphs accordingly.

We have revised this AD to identify the legal name of the manufacturer as published in the most recent type certificate data sheet for the affected airplane models. Costs of Compliance

We estimate that this proposed AD will affect 127 airplanes of U.S. registry. We estimate the following costs to comply with this proposed AD:



### E STIMATED 

### C OSTS

Action Labor cost Parts cost Cost per product Cost on U.S. operators

Inspection of MOV Actuators ........ Up to 6 work-hours × $85 per hour = $510 .............. $0 Up to $510 ....... Up to $64,770.

We estimate the following costs to do any necessary replacements that would be required based on the results of the proposed inspection. We have no way of determining the number of aircraft that might need these replacements.



### O N 

### -C ONDITION 

### C OSTS

Action Labor cost Parts cost Cost per product

Replacement of MOV Actuator Without

Fuel Tank Access. Up to 47 work-hours × $85 per hour = $3,995. Up to $5,477, per actuator ................... Up to $9,472.


### 80741 Federal Register / Vol. 75, No. 246 / Thursday, December 23, 2010 / Proposed Rules

O N 

### -C ONDITION 

### C OSTS

### —Continued

Action Labor cost Parts cost Cost per product

Replacement of MOV Actuator With

Fuel Tank Access. Up to 423 work-hours × $85 per hour = $35,955. Up to $5,477, per actuator ................... Up to $41,432.

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 [Amended]**

2. The FAA amends § 39.13 by adding the following new AD:
The Boeing Company: Docket No. FAA– 2008–0847; Directorate Identifier 2008– NM–056–AD.

Comments Due Date

(a) We must receive comments by January 18, 2011.

Affected ADs

(b) None.
Applicability

(c) This AD applies to The Boeing Company Model 777–200, –200LR, –300, and –300ER series airplanes, certificated in any category; as identified in Boeing Service Bulletin 777–28A0034, Revision 2, dated September 20, 2010.
Subject

(d) Air Transport Association (ATA) of America Code 28, Fuel.

Unsafe Condition

(e) This AD results from fuel system reviews conducted by the manufacturer. The Federal Aviation Administration is issuing this AD to prevent electrical current from flowing through a motor operated valve (MOV) actuator into a fuel tank, which could create a potential ignition source inside the fuel tank. This condition, in combination with flammable fuel vapors, could result in a fuel tank explosion and consequent loss of the airplane.
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.
Inspection

(g) Within 60 months after the effective date of this AD, do an inspection of the MOV actuators of the main and center fuel tanks for part number (P/N) MA20A1001–1, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 777– 28A0034, Revision 2, dated September 20, 2010. A review of airplane maintenance records is acceptable in lieu of this inspection if the part number can be conclusively determined from that review. Replacement (h) If any P/N MA20A1001–1 is found during the inspection required by paragraph (g) of this AD, within 60 months after the effective date of this AD, replace the MOV actuator with a new or serviceable MOV actuator, P/N MA30A1001; and as applicable, measure the electrical resistance of the bond from the adapter plate to the airplane structure and do all applicable corrective actions; in accordance with the Accomplishment Instructions of Boeing Service Bulletin 777–28A0034, Revision 2, dated September 20, 2010. Do all applicable corrective actions before further flight.

Part Installation

(i) As of the effective date of this AD, no person may install an MOV actuator, P/N MA20A1001–1, on any airplane.
Credit for Actions Accomplished in Accordance With Previous Service Information

(j) Actions done in accordance with Boeing Alert Service Bulletin 777–28A0034, dated August 2, 2007; or Boeing Alert Service Bulletin 777–28A0034, Revision 1, dated May 20, 2010; are considered acceptable for compliance with the corresponding actions required by paragraphs (g) and (h) of this AD; except that replacement of an MOV actuator in accordance with Boeing Alert Service Bulletin 777–28A0034, dated August 2, 2007, is acceptable for the replacement required by paragraph (h) of this AD, provided that the replacement P/N is MA30A1001.
Alternative Methods of Compliance (AMOCs)

(k)(1) The Manager, Seattle Aircraft Certification Office (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: Tak Kobayashi, Aerospace Engineer, Propulsion Branch, ANM–140S, FAA, Seattle ACO, 1601 Lind Avenue SW., Renton, Washington 98057–3356; telephone (425) 917–6499; fax (425) 917–6590. Information may be e-mailed

to: 9-ANM-Seattle-ACO-AMOCRequests@faa.gov

.

(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.


### 80742 Federal Register / Vol. 75, No. 246 / Thursday, December 23, 2010 / Proposed Rules

Issued in Renton, Washington, on December 16, 2010. Ali Bahrami, Manager, Transport Airplane Directorate, Aircraft Certification Service.
[FR Doc. 2010–32208 Filed 12–22–10; 8:45 am]

**BILLING CODE 4910–13–P**

**DEPARTMENT OF TRANSPORTATION**

**Federal Aviation Administration**

**14 CFR Part 39**

**[Docket No. FAA–2010–1202; Directorate Identifier 2010–NM–167–AD]** 

**RIN 2120–AA64**

**Airworthiness Directives; McDonnell Douglas Corporation Model MD–90–30**  **Airplanes**

**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 inspections for cracking of the left and right upper center skin panels of the horizontal stabilizer, and corrective action if necessary. This proposed AD was prompted by a report of a crack found in the upper skin panel at the aft inboard corner of a right horizontal stabilizer. We are proposing this AD to detect and correct cracks in the horizontal stabilizer upper center skin panel. Uncorrected cracks might ultimately lead to the loss of overall structural integrity of the horizontal stabilizer.

**DATES :**  We must receive comments on this proposed AD by February 7, 2011.

**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: Deliver to Mail address above 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 (phone: 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, Los Angeles ACO, Airframe Branch, ANM– 120L, FAA Los Angeles Aircraft Certification Office, 3960 Paramount Blvd, Lakewood, CA 90712–4137; telephone: (562) 627–5233; fax: (562) 627–5210; e-mail: roger.durbin@faa.gov.

**SUPPLEMENTARY INFORMATION :** 
Comments Invited

We invite you to send any written relevant data, views, or arguments about this proposal. Send your comments to an address listed under the **ADDRESSES** section. Include ‘‘Docket No. FAA– 2010–1202; Directorate Identifier 2010– NM–167–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.

Discussion

We have received a report of a crack to a Model MD–80 airplane upper center skin panel of the right horizontal stabilizer at the aft inboard corner during an inspection for cracks in the upper and lower aft skin panels of the horizontal stabilizer in accordance with AD 2007–10–04, Amendment 39–15045 (72 FR 25960, May 8, 2007). That airplane had accumulated 47,146 total flight hours and 26,490 total flight cycles when the crack was found. The cause of the cracking is suspected to be fatigue. The Model MD–90–30 airplane horizontal stabilizer is similar in design and loading to that of the Model MD– 80 airplane horizontal stabilizer. Therefore, Model MD–90–30 airplanes may also be subject to the identified unsafe condition.

A crack in the upper center skin panel may transfer the load to the upper aft skin panel. This may result in the upper aft skin panel cracking faster than the existing inspection intervals that are required by AD 2009–13–08, Amendment 39–15947 (74 FR 30922, June 29, 2009). Uncorrected cracking could result in loss of the overall structural integrity of the horizontal stabilizer.

Relevant Service Information

We reviewed Boeing Alert Service Bulletin MD90–55A015, dated July 16, 2010. This service bulletin describes procedures for repetitive eddy current inspections, either (Option 1) two high frequency eddy current (ETHF) scans and one low frequency eddy current (ETLF) scan, or (Option 2) three ETHF scans, to detect cracking of the right and left upper center skin panels of the horizontal stabilizer. Corrective actions include replacing any cracked horizontal stabilizer upper center skin panel with a serviceable panel or contacting Boeing for possible temporary repair instructions.

The repetitive interval is 5,200 flight cycles or 2,500 flight cycles depending on the eddy current inspection option selected.

FAA’s Determination

We are proposing this AD because we evaluated all the relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of the same type design. Proposed AD Requirements

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 the Service Information. ’’ Differences Between the Proposed AD and the Service Information

Boeing Alert Service Bulletin MD90– 55A015, dated July 16, 2010, provides an option to contact the manufacturer for instructions on how to repair