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Proposed Advisory Circular 120-YY, Widespread Fatigue Damage on Metallic Structure

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Information about this document as published in the Federal Register.

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Federal Aviation Administration, DOT.


Notice of Availability of Proposed Advisory Circular (AC) 120-YY, and request for comments.


This notice announces the availability of and requests comments on a proposed advisory circular (AC) which provides guidance to design approval holders for certain transport category airplanes and on repairs and alterations to those airplanes for developing means to preclude widespread fatigue. 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.


We must receive your comments by July 17, 2006.


You must mail two copies of your comments on the proposed AC to: Federal Aviation Administration, Attention: Walter Sippel, Airframe and Cabin Safety Branch, ANM-115, FAA, Transport Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue SW., Renton, WA 98055-4056. You can inspect comments at the above address between 7:30 a.m. and 4 p.m. weekdays, except Federal holidays.

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Jan Thor, Transport Standards Staff, at the address above, telephone (425) 227-2127.

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Comments Invited

We invite interested people to comment on the proposed AC by sending written data, views, or arguments. You should identify AC 120-YY 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​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.


This proposed AC provides guidance to design approval holders on establishing operational limits (initial and extended) to preclude widespread fatigue damage for certain transport category airplanes. It also provides guidance for evaluating repairs and alterations to those airplanes for developing a means to preclude widespread fatigue damage. This AC also provides guidance to operators of those airplanes for use in incorporating Airworthiness Limitations sections with corresponding initial operational limits and airworthiness limitations items into their maintenance program. This guidance material applies to transport category airplanes operated under 14 CFR part 121 or part 129, that were certificated under the fail-safe and fatigue requirements of Civil Air Regulations (CAR) 4b or 14 Code of Federal Regulations (CFR) part 25; and

1. Have a maximum gross takeoff weight greater than 75,000 pounds, or

2. Were certificated with maximum takeoff gross weight of 75,000 pounds or less, and later increased to greater than 75,000 pounds by an amended type certificate or supplemental type certificate.

It is one means, but not the only means, of complying with the part 25 revisions proposed in Notice No. 06-04 entitled “Widespread Fatigue Damage,” which was published in the Federal Register on April 18, 2006 (71 FR 19928). Issuance of AC 120-YY is contingent on final adoption of the proposed revisions to part 25.

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Issued in Washington, DC, on May 12, 2006.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.

Ricardo Domingo,

Acting Manager, Aircraft Maintenance Division, Flight Standards Service.

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[FR Doc. E6-7794 Filed 5-19-06; 8:45 am]