### 38069 Federal Register / Vol. 76, No. 125 / Wednesday, June 29, 2011 / Proposed Rules

Manual, CSP A–012; and the service bulletins listed in table 6 of this AD; for related information.



### TABLE 

### 6—R ELATED 

### S ERVICE 

### I NFORMATION

Document Revision Date

Bombardier Alert Service Bulletin A601R–29–029 .............................................. B ............................................................ May 11, 2010. Bombardier Alert Service Bulletin A601R–29–031 .............................................. A ............................................................ March 26, 2009. Bombardier Alert Service Bulletin A601R–32–103 .............................................. D ........................................................... May 11, 2010. Bombardier Service Bulletin 601R–29–032 ......................................................... A ............................................................ January 26, 2010. Bombardier Service Bulletin 601R–29–033 ......................................................... A ............................................................ May 11, 2010. Bombardier Service Bulletin 601R–29–035 ......................................................... A ............................................................ December 8, 2010. Bombardier Service Bulletin 601R–32–106 ......................................................... A ............................................................ May 11, 2010. Bombardier Service Bulletin 601R–32–107 ......................................................... B ............................................................ December 8, 2010.

Issued in Renton, Washington, on June 16,
2011. Ali Bahrami, Manager, Transport Airplane Directorate, Aircraft Certification Service.
[FR Doc. 2011–16365 Filed 6–28–11; 8:45 am]

**BILLING CODE 4910–13–P**

**DEPARTMENT OF TRANSPORTATION**

**Federal Aviation Administration**

**14 CFR Part 39**

**[Docket No. FAA–2011–0647; Directorate Identifier 2010–NM–193–AD]** 

**RIN 2120–AA64**

**Airworthiness Directives; Airbus Model A300 B4–600, B4–600R, and F4–600R**  **Series Airplanes, and Model C4–605R Variant F Airplanes (Collectively Called**  **A300–600 Series Airplanes) and A310 Series Airplanes** 

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

**ACTION :**  Notice of proposed rulemaking (NPRM).

**SUMMARY :**  We propose to adopt a new airworthiness directive (AD) for the products listed above. This proposed AD results from mandatory continuing airworthiness information (MCAI) originated by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as:

Surface defects were visually detected on the rudder of an Airbus A319 and an A321 in-service aeroplane. Investigation has determined that the defects reported on both rudders corresponded to areas that had been reworked in production. The investigation confirmed that the defects were the result of de-bonding between the skin and honeycomb core. Such reworks were also performed on some rudders fitted on A310 and A300–600 aeroplanes.

An extended de-bonding, if not detected and corrected, may degrade the structural integrity of the rudder. The loss of the rudder leads to degradation of the handling qualities and reduces the controllability of the aeroplane.
* * * * * The proposed AD would require actions that are intended to address the unsafe condition described in the MCAI.

**DATES :**  We must receive comments on this proposed AD by August 15, 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 W12–40, 1200 New Jersey Avenue, SE., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

For service information identified in this proposed AD, contact Airbus SAS– EAW (Airworthiness Office), 1 Rond Point Maurice Bellonte, 31707 Blagnac Cedex, France; telephone +33 5 61 93 36 96; fax +33 5 61 93 44 51; e-mail account.airworth-eas@airbus.com; Internet http://www.airbus.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 Operations office 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 Operations 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 :**  Dan Rodina, Aerospace Engineer, International Branch, ANM–116, Transport Airplane Directorate, FAA, 1601 Lind Avenue, SW., Renton, Washington 98057–3356; telephone (425) 227–2125; fax (425) 227–1149.

**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–2011–0647; Directorate Identifier 2010–NM–193–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 based on 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

The European Aviation Safety Agency (EASA), which is the Technical Agent for the Member States of the European Community, has issued EASA Airworthiness Directive 2010–0144, dated July 16, 2010 (referred to after this as ‘‘the MCAI’’), to correct an unsafe condition for the specified products. The MCAI states:

Surface defects were visually detected on the rudder of an Airbus A319 and an A321 in-service aeroplane. Investigation has determined that the defects reported on both rudders corresponded to areas that had been reworked in production. The investigation


### 38070 Federal Register / Vol. 76, No. 125 / Wednesday, June 29, 2011 / Proposed Rules

confirmed that the defects were the result of de-bonding between the skin and honeycomb core. Such reworks were also performed on some rudders fitted on A310 and A300–600 aeroplanes.

An extended de-bonding, if not detected and corrected, may degrade the structural integrity of the rudder. The loss of the rudder leads to degradation of the handling qualities and reduces the controllability of the aeroplane.

To address this unsafe condition EASA issued AD 2010–0002 [which corresponds to FAA AD 2010–16–13, amendment 39– 16390], superseding [EASA] AD 2009–0166, to require inspections of specific areas and, depending on findings, the application of corrective actions for those rudders where production reworks have been identified.

This new [EASA] AD addresses the rudder population that has also been reworked in production, but not included in the applicability of EASA AD 2010–0002. The required actions, for certain rudders, include vacuum loss inspections and elasticity laminate checker inspections for defects including de-bonding between the skin and honeycomb core of the rudder. The corrective action is contacting the FAA or EASA for repair instructions if any defects are found. For certain other rudders, the required actions include replacing the rudder with a serviceable rudder. We are considering similar rulemaking action on Model A319 and A321 airplanes. You may obtain further information by examining the MCAI in the AD docket.

Relevant Service Information

Airbus has issued Mandatory Service Bulletins A310–55–2049 and A300–55– 6048, both dated March 16, 2010. The actions described in this service information are intended to correct the unsafe condition identified in the MCAI. FAA’s Determination and Requirements of This Proposed AD

This product has been approved by the aviation authority of another country, and is approved for operation in the United States. Pursuant to our bilateral agreement with the State of Design Authority, we have been notified of the unsafe condition described in the MCAI and service information referenced above. We are proposing this AD 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.

Differences Between This AD and the MCAI or Service Information

We have reviewed the MCAI and related service information and, in general, agree with their substance. But we might have found it necessary to use different words from those in the MCAI to ensure the AD is clear for U.S. operators and is enforceable. In making these changes, we do not intend to differ substantively from the information provided in the MCAI and related service information.

We might also have proposed different actions in this AD from those in the MCAI in order to follow FAA policies. Any such differences are highlighted in a NOTE within the proposed AD. Costs of Compliance

Based on the service information, we estimate that this proposed AD would affect about 215 products of U.S. registry. We also estimate that it would take about 4 work-hours per product to comply with the basic requirements of this proposed AD. The average labor rate is $85 per work-hour. Based on these figures, we estimate the cost of the proposed AD on U.S. operators to be $73,100, or $340 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.

We prepared a regulatory evaluation of the estimated costs to comply with this proposed AD and placed it 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:

Airbus: Docket No. FAA–2011–0647; Directorate Identifier 2010–NM–193–AD.

Comments Due Date

(a) We must receive comments by August
15, 2011.

Affected ADs

(b) None.
Applicability

(c) This AD applies to Airbus Model A300 B4–601, B4–603, B4–620, B4–622, B4–605R, B4–622R, F4–605R, F4–622R, and C4–605R Variant F airplanes; and Model A310–203, –204, –221, –222, –304, –322, –324, and –325 airplanes; certificated in any category; equipped with carbon fiber reinforced plastic rudders having any part number and serial number listed in Table 1, 2, 3, or 4 of this
AD.



### T ABLE 

### 1—R UDDER 

### I NFORMATION

Rudder part No. Affected rudder serial No.

A554–71710–000–00 ................... TS–2010 A554–71710–000–00 ................... TS–2027 A554–71710–000–00 ................... TS–2030 A554–71710–002–00 ................... TS–2043 A554–71710–004–00 ................... TS–2048


### 38071 Federal Register / Vol. 76, No. 125 / Wednesday, June 29, 2011 / Proposed Rules

TABLE 

### 2—R UDDER 

### I NFORMATION

Rudder part No. Affected rudder serial No.

MSN—scrapped ........................... TS–1362 A554–71710–000–00 ................... TS–2006 A554–71710–000–00 ................... TS–2008 A554–71710–002–00 ................... TS–2033 A554–71710–004–00 ................... TS–2054 A554–71710–004–00 ................... TS–2061 A554–71710–004–00 ................... TS–2071 A554–71710–004–00 ................... TS–2072 A554–71710–004–00 ................... TS–2073 A554–71730–000–00–0000 ......... TS–2082 A554–71730–000–00–0000 ......... TS–2084 A554–71730–000–00–0000 ......... TS–2085 A554–71730–000–00–0000 ......... TS–2086 A554–71730–000–00–0000 ......... TS–2087



### TABLE 

### 3—R UDDER 

### I NFORMATION

Rudder part No. Affected rudder serial No.

A554–71500–016–30 ................... HF–1254 A554–71710–004–00 ................... TS–2049 A554–71710–004–00 ................... TS–2055 A554–71710–004–00 ................... TS–2059



### TABLE 

### 4—R UDDER 

### I NFORMATION

Rudder part No. Affected rudder serial No.

A554–71500–016–91 ................... HF–1044 A554–71500–014–00 ................... HF–1116 A554–71500–016–00 ................... HF–1183 A554–71500–016–00 ................... HF–1184 A554–71500–026–00 ................... TS–1402

Subject

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

Reason

(e) The mandatory continuing airworthiness information (MCAI) states:

Surface defects were visually detected on the rudder of an Airbus A319 and an A321 in-service aeroplane. Investigation has determined that the defects reported on both rudders corresponded to areas that had been reworked in production. The investigation confirmed that the defects were the result of de-bonding between the skin and honeycomb core. Such reworks were also performed on some rudders fitted on A310 and A300–600 aeroplanes.

An extended de-bonding, if not detected and corrected, may degrade the structural integrity of the rudder. The loss of the rudder leads to degradation of the handling qualities and reduces the controllability of the aeroplane.
* * * * *
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.
Inspections and Corrective Actions for Rudders Identified in Tables 1, 2, and 3

(g) For rudders identified in Table 1 or Table 2 of this AD: Do the actions specified in paragraph (g)(1) or (g)(2) of this AD, as applicable, and paragraphs (g)(3) and (g)(4) of this AD, at the time specified. Do the actions in accordance with the Accomplishment Instructions of Airbus Mandatory Service Bulletin A310–55–2049 (for Model A310 series airplanes) or A300–55–6048 (for Model A300–600 series airplanes), both dated March 16, 2010.

(1) For rudders identified in Table 1 of this AD: Within 8 months after the effective date of this AD, perform a vacuum loss inspection in the ‘‘area 1’’ location defined in Airbus Mandatory Service Bulletin A310–55–2049 or A300–55–6048, both dated March 16, 2010, as applicable, to detect defects, including de-bonding.

(2) For rudders identified in Table 2 of this AD: Within 24 months after the effective date of this AD, perform a vacuum loss inspection in the ‘‘area 1’’ location defined in Airbus Mandatory Service Bulletin A310–55–2049 or A300–55–6048, both dated March 16, 2010, as applicable, to detect defects, including de-bonding.

(3) Within 24 months after the effective date of this AD: Do an elasticity laminate checker inspection to detect defects, including de-bonding, in the trailing edge location.

(4) Repeat the inspection required by paragraph (g)(3) of this AD two times at intervals not to exceed 4,500 flight cycles, but not fewer than 4,000 flight cycles from the most recent inspection.

(h) For rudders identified in Table 3 of this AD: Do the actions specified in paragraphs (h)(1) and (h)(2) of this AD at the time specified. Do the actions in accordance with the Accomplishment Instructions of Airbus Mandatory Service Bulletin A310–55–2049 (for Model A310 series airplanes) or A300– 55–6048 (for Model A300–600 series airplanes), both dated March 16, 2010.

(1) Within 4,500 flight cycles after the effective date of this AD, but not fewer than 4,000 flight cycles from the most recent elasticity laminate checker inspection: Do an elasticity laminate checker inspection to detect defects, including de-bonding, in the trailing edge location.

(2) Repeat the inspection required by paragraph (h)(1) of this AD one time within 4,500 flight cycles, but not fewer than 4,000 flight cycles from the last inspection.

(i) If any defect is found during any inspection required by paragraphs (g) and (h) of this AD, before further flight, repair in accordance with a method approved by the Manager, International Branch, ANM–116, Transport Airplane Directorate, FAA, or the European Aviation Safety Agency (EASA) (or its delegated agent).

(j) If no defect is found during the inspections required by paragraphs (g)(1) and (g)(2) of this AD, before further flight, restore the vacuum loss holes with the temporary restoration with self adhesive tape, temporary restoration with resin, or permanent restoration with resin and surface protection. Do the applicable actions specified in paragraph (j)(1) or (j)(2) of this AD.

(1) For airplanes on which a temporary restoration with self-adhesive disks or tapes is done, within 4 months after doing the restoration, do a detailed inspection for loose or missing self-adhesive disks or tapes and repeat the inspection thereafter at intervals not to exceed 4 months until the permanent restoration is done, in accordance with the Accomplishment Instructions of Airbus Mandatory Service Bulletin A310–55–2049 (for Model A310 series airplanes) or A300– 55–6048 (for Model A300–600 series airplanes), both dated March 16, 2010. If any loose or missing self-adhesive disks or tapes are found during any inspection required by this AD, before further flight, close the holes, in accordance with the Accomplishment Instructions of Airbus Mandatory Service Bulletin A310–55–2049 or A300–55–6048, both dated March 16, 2010, as applicable. Do the permanent restoration within 4,500 flight cycles after doing the temporary restoration, in accordance with the Accomplishment Instructions of Airbus Mandatory Service Bulletin A310–55–2049 or A300–55–6048, both dated March 16, 2010, as applicable.

(2) For airplanes on which a temporary restoration with resin is done: Within 4,500 flight cycles after doing the temporary restoration do the permanent restoration, in accordance with the Accomplishment Instructions of Airbus Mandatory Service Bulletin A310–55–2049 (for Model A310 series airplanes) or A300–55–6048 (for Model A300–600 series airplanes), both dated March 16, 2010.
Reporting

(k) At the applicable time specified in paragraph (k)(1) or (k)(2) of this AD: Report the results of each inspection required by paragraphs (g) and (h) of this AD, including no findings, to Airbus, as specified in Airbus Mandatory Service Bulletin A310–55–2049 (for Model A310 series airplanes) or A300– 55–6048 (for Model A300–600 series airplanes), both dated March 16, 2010.

(1) Inspections done before the effective date of this AD: Within 30 days after the effective date of this AD.

(2) Inspections done on or after the effective date of this AD: Within 30 days after accomplishment of the inspection.
Replacement for Rudders Identified in Table 4

(l) For rudders identified in Table 4 of this AD: Within 8 months after the effective date of this AD, replace the affected rudder with a serviceable unit, in accordance with a method approved by the Manager, International Branch, ANM–116, Transport Airplane Directorate, FAA, or the EASA (or its delegated agent).

Parts Installation

(m) As of the effective date of this AD, no person may install any rudder identified in Table 1, 2, or 3 of this AD on any airplane, unless the rudder has been inspected and all applicable corrective actions have been done in accordance with paragraphs (g), (h), and (i) of this AD, as applicable.


### 38072 Federal Register / Vol. 76, No. 125 / Wednesday, June 29, 2011 / Proposed Rules

(n) As of the effective date of this AD, no person may install any rudder identified in Table 4 of this AD on any airplane.

FAA AD Differences

Note 1: This AD differs from the MCAI and/or service information as follows: No differences.

Other FAA AD Provisions

(o) The following provisions also apply to this AD:

(1) Alternative Methods of Compliance (AMOCs): The Manager, International Branch, ANM–116, FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. In accordance with 14 CFR 39.19, send your request to your principal inspector or local Flight Standards District Office, as appropriate. If sending information directly to the International Branch, send it to ATTN: Dan Rodina, Aerospace Engineer, International Branch, ANM–116, Transport Airplane Directorate, FAA, 1601 Lind Avenue, SW., Renton, Washington 98057– 3356; telephone (425) 227–2125; fax (425) 227–1149. Information may be e-mailed to: 9-ANM-116-AMOC-REQUESTS@faa.gov. Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the local flight standards district office/ certificate holding district office. The AMOC approval letter must specifically reference this AD.

(2) Airworthy Product: For any requirement in this AD to obtain corrective actions from a manufacturer or other source, use these actions if they are FAA-approved. Corrective actions are considered FAA-approved if they are approved by the State of Design Authority (or their delegated agent). You are required to assure the product is airworthy before it is returned to service.

(3) Reporting Requirements: A federal agency may not conduct or sponsor, and a person is not required to respond to, nor shall a person be subject to a penalty for failure to comply with a collection of information subject to the requirements of the Paperwork Reduction Act unless that collection of information displays a current valid OMB Control Number. The OMB Control Number for this information collection is 2120–0056. Public reporting for this collection of information is estimated to be approximately 5 minutes per response, including the time for reviewing instructions, completing and reviewing the collection of information. All responses to this collection of information are mandatory. Comments concerning the accuracy of this burden and suggestions for reducing the burden should be directed to the FAA at: 800 Independence Ave., SW., Washington, DC 20591, Attn: Information Collection Clearance Officer, AES–200.

Related Information

(p) Refer to MCAI EASA Airworthiness Directive 2010–0144, dated July 16, 2010; and Airbus Mandatory Service Bulletins A310–55–2049 and A300–55–6048, both dated March 16, 2010; for related information. Issued in Renton, Washington, on June 16,
2011. Ali Bahrami, Manager, Transport Airplane Directorate, Aircraft Certification Service.
[FR Doc. 2011–16367 Filed 6–28–11; 8:45 am]

**BILLING CODE 4910–13–P**

**DEPARTMENT OF TRANSPORTATION**

**Federal Aviation Administration**

**14 CFR Part 39**

**[Docket No. FAA–2011–0644; Directorate Identifier 2010–NM–265–AD]** 

**RIN 2120–AA64**

**Airworthiness Directives; The Boeing Company Model 777 Airplanes** 

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

**ACTION :**  Notice of proposed rulemaking (NPRM).

**SUMMARY :**  We propose to adopt a new airworthiness directive (AD) for the products listed above. This proposed AD would require repetitive detailed inspection and high frequency eddy current (HFEC) inspections for cracks of the wing center section (WCS) spanwise beams, and repair if necessary. This proposed AD was prompted by reports of cracks found in the web pockets of the WCS spanwise beams. We are proposing this AD to detect and correct cracking in the WCS spanwise beams, which could result in reduced structural integrity of the wings.

**DATES :**  We must receive comments on this proposed AD by August 15, 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, 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 (phone: 800–647–5527) is in the

**ADDRESSES** section. Comments will be available in the AD docket shortly after receipt.

**FOR FURTHER INFORMATION CONTACT :**  Duong Tran, Aerospace Engineer, Airframe Branch, ANM–120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057–3356; phone: (425) 917–6452; Fax: (425) 917–6590; e-mail: duong.tran@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– 2011–0644; Directorate Identifier 2010– NM–265–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 reports of cracking in the wing center section (WSC) spanwise beams. Two operators reported finding a crack in the web pockets of WCS spanwise beams on two airplanes. In the first report, metallurgical testing showed the cracks were the result of fatigue from reverse bending (diagonal tension buckling).

If cracking at multiple locations occurs in multiple spanwise beams, the WCS spanwise beams might not be able