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###### Department of Transportation

###### Federal Aviation Administration 

# AGENCY:

Federal Aviation Administration, DOT. 

# ACTION:

Notice of issuance of advisory circular. 

# SUMMARY:

This notice announces the issuance of Advisory Circular (AC) 23.629-1B. This advisory circular presents information and guidance to provide one means, but not the only means of complying with § 23.629, Flutter (including divergence, and control reversal) of part 23 of the Federal Aviation Regulations. Accordingly, this material is neither mandatory nor regulatory in nature. 

The complexity of flutter analysis has historically prompted endeavors to find simplified methods of flutter substantiation. The advent of electronic computers has de-emphasized the need to make drastic assumptions previously necessary to enable mathematical treatment of the flutter phenomenon. However, there remains a need to simplify flutter solution as much as possible consistent with safety in order to minimize the cost and effort required to show freedom from flutter. Past experiences gained by the necessity to judiciously choose degrees of freedom, and by the need to make essential parametric studies has resulted in a generally recognized set of good practices. These good practices form the basis for this advisory circular. 

The draft advisory circular was issued for Public Comment on February 25, 2004 (69 FR 8728). When possible, comments received were used to modify the draft advisory circular. 

                        We received some comments regarding the general layout of the advisory circular. We will consider reorganizing the content for the next revision. Any suggestions for the reorganization will be considered. For more information, or to make recommendations for the improvement of this advisory circular, contact Mark James, Standards Office, Small Airplane Directorate, Aircraft Certification Service, Kansas City, Missouri 64106, telephone (816) 329-4137, fax (816) 329-4090,                         *mark.james@faa.gov.*

# DATES:

Advisory Circular (AC) 23-629-1B was issued by the Manager, Small Airplane Directorate on September 28, 2004. 

*How to Obtain Copies:*                         A paper copy of AC 23.629-1B may be obtained by writing to the U.S. Department of Transportation, Subsequent Distribution Office, DOT Warehouse, SVC-121.23, Ardmore East Business Center, 3341Q 75th Avenue, Landover, MD 20785, telephone 301-322-5377, or by faxing your request to the warehouse at 301-386-5394. The policy will also be available on the Internet at                         *http://www.airweb.faa.gov/​AC.*

Issued in Kansas City, Missouri, on September 28, 2004. 

Dorenda D. Baker, 

Manager, Small Airplane Directorate, Aircraft Certification Service. 

[FR Doc. 04-23068 Filed 10-13-04; 8:45 am] 

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