Document Headings

                    Document headings vary by document type but may contain                    the following:                  
                -                       the agency or agencies that issued and signed a document                    
                -                       the number of the CFR title and the number of each part                      the document amends, proposes to amend, or is directly                      related to                    
                -                       the agency docket number / agency internal file number                    
                -                       the RIN which identifies each regulatory action listed in                      the Unified Agenda of Federal Regulatory and Deregulatory                      Actions                    

                    See the                                          Document Drafting Handbook                                        for more details.                  

###### Department of Transportation

###### Federal Aviation Administration 

# AGENCY:

Federal Aviation Administration, DOT. 

# ACTION:

Notice of Availability of Proposed Advisory Circular (AC) 120-XX, and Request for Comments 

# SUMMARY:

This notice announces the availability of and requests comments on a proposed advisory circular (AC) which provides guidance to type certificate holders and supplemental type certificate holders for developing damage tolerance data that will support operator compliance with certain airworthiness standards. This proposed AC complements revisions to the airworthiness standards that are being proposed by a separate notice. This notice is necessary to give all interested persons an opportunity to present their views on the proposed AC. 

# DATES:

We must receive your comments by April 20, 2007. 

# ADDRESSES:

You must mail two copies of your comments on the proposed AC to: Federal Aviation Administration, Attention: Greg Schneider, Airframe and Cabin Safety Branch, ANM-115, FAA, Transport Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue SW., Renton, WA 98057-3356. You can inspect comments at the above address between 7:30 a.m. and 4 p.m. weekdays, except Federal holidays. 

# FOR FURTHER INFORMATION CONTACT:

Kenna Sinclair, Transport Standards Staff, at the address above, telephone (425) 227-1556. 

# SUPPLEMENTARY INFORMATION:

## Comments Invited 

                    We invite interested people to comment on the proposed AC by sending written data, views, or arguments. You should identify AC 120-XX and send two copies of your comments to the address specified above. We will consider all communications received by the closing date for comments. We will consider comments received late if it is possible to do so without incurring expense or delay. The proposed AC can be found and downloaded from the Internet at                     *http://www.faa.gov/​aircraft/​draft_​docs*. A paper copy of the proposed AC may be obtained by contacting the person named above under the caption                     **FOR FURTHER INFORMATION CONTACT**                    .                 

## Discussion 

This proposed AC provides guidance material to support Type Certificate (TC) and Supplemental Type Certificate (STC) Holder compliance with proposed rulemaking title 14 Code of Federal Regulations (14 CFR) 25.1823, Supplemental Structural Inspections, Holders of type certificates—Repairs; 14 CFR 25.1825, Supplemental Structural Inspections, Holders of type certificates—Alterations and repairs to alterations; 14 CFR 25.1827, Supplemental Structural Inspections, Holders of and applicants for a Supplemental type certificate—Alterations and repairs to alterations. These proposed regulations would require TC Holders and STC Holders to develop damage tolerance data that would support operator compliance with 14 CFR 121.1109 and 14 CFR 129.109, the Aging Airplane Safety Final Rule (AASFR) (currently found at §§ 121.370(a) and 129.16) with respect to repairs and alterations. Sections 121.370(a) and 129.16 require operators of certain transport airplane models to incorporate into their maintenance program damage tolerance-based inspections and procedures for structure susceptible to fatigue cracking that could contribute to a catastrophic failure. The proposed AC refers to that type of structure as fatigue critical structure. The proposed AC is applicable to repairs and alterations that  affect fatigue critical structure. 

                    The proposed AC also provides guidance for new and existing repairs and alterations made to the original, as delivered, airplane structural configuration, as well as repairs to alterations. For compliance with § 121.1109 and § 129.109, operators will need to demonstrate that new and existing repairs and alterations will have an evaluation and damage                           ( print page 8835)                        tolerance-based inspections or other procedures implemented, if needed.                 

                    Following the guidance in this proposed AC is one means, but not the only means, of complying with the part 25 revisions proposed in Notice No. 05-11 entitled Damage Tolerance Data for Repairs and Alterations, which was published in the                     **Federal Register**                     on April 21, 2006 (71 FR 20574). Issuance of AC 120-XX is contingent on final adoption of the proposed revisions to part 25.                 

Issued in Washington, DC, on February 20, 2007. 

Ali Bahrami, 

Manager, Transport Airplane Directorate, Aircraft Certification Service. 

Dave Cann, 

Manager, Aircraft Maintenance Division,  Flight Standards Service.

[FR Doc. E7-3329 Filed 2-26-07; 8:45 am] 

BILLING CODE 4910-13-P