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###### Department of Transportation

###### Federal Aviation Administration

# AGENCY:

Federal Aviation Administration, DOT.

# ACTION:

Notice of availability of proposed advisory circular (AC) 25-XX and request for comments. 

# SUMMARY:

                        This notice announces the availability of and requests comments on a proposed advisory circular (AC) which provides methods acceptable to                               ( print page 31206)                            the Administrator related to the aircraft design for sustained engine rotor imbalance conditions provisions of 14 CFR part 25 regarding the type certification requirements for transport airplane structure. This notice is necessary to give all interested persons an opportunity to present their views on the proposed AC.                    

# DATES:

Comments must be received on or before July 10, 2000.

# ADDRESSES:

Send all comments on the proposed AC to: Federal Aviation Administration, Attention: Jim Haynes, Airframe/Airworthiness Branch, ANM-115, Transport Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue SW, Renton, WA 98055-4056. Comments may also be submitted electronically to the following address: jim.haynes@faa.gov. Comments may be inspected at the above address between 7;30 a.m. and 4:00 p.m. weekdays, except Federal holidays.

# FOR FURTHER INFORMATION CONTACT:

Jim Haynes, Airframe/Airworthiness Branch, ANM-115, Transport Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue SW, Renton, WA 98055-4056; telephone (425) 227-2131; facsimile (425) 227-1320. Questions may also be submitted electronically to the following address: jim.haynes@faa.gov.

# SUPPLEMENTARY INFORMATION:

## Comments Invited

You may obtain an electronic copy of the advisory circular identified in this notice at the following Internet address: www.faa.gov/​avr/​air/​airhome.htm. If you do not have access to the Internet, you may request a copy by contacting Susan Boylon, Program Management Branch, ANM-114, FAA Transport Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue SW., Renton, WA 98055-4056; telephone (425) 227-1152. Interested persons are invited to comment on the proposed AC by submitting such written data, views, or arguments, as they may desire. Commenters should identify AC 25-XX, and submit comments, in duplicate, to the address specified above. All communications received on or before the closing date for comments will be considered by the Transport Standards Staff before issuing the final AC.

## Discussion

This AC contains guidance for the latest amendment of the regulations and applies to all transport category airplanes for which a new, amended, or supplemental type certificate is required. This guidance should be applied to any portion of the airplane structure that has been modified. In the past, advisory and guidance information applicable to transport airplane structure has been published as AC's. Advisory circulars have not been developed for all of the regulatory requirements applicable to transport airplane structure, however. In many instances, certification of new technology airplanes resulted in the need to interpret the existing regulations and to apply new regulations. Issue papers and special conditions were generated to document the compliance method agreed upon between the applicant and the FAA. In other instances, applicants, FAA Aircraft Certification Office (ACO) managers, and foreign regulatory authorities have requested interpretation of the intent of specific regulations. This guidance was documented in the form of policy memorandums that were distributed to all ACO's, letters to applicants and foreign airworthiness authorities, and issue papers. In many instances, this information was not organized in a manner that allowed easy access, and applicants were not aware of revised policy. This AC formalizes existing policy so that the public and FAA personnel have access to this information. The methods and procedures described in this AC have evolved after many years and represent current certification practice.

Issued in Renton, Washington, on May 8, 2000.

Vi L. Lipski,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service, ANM-100.

[FR Doc. 00-12311  Filed 5-15-00; 8:45 am]

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