Proposed Advisory Circular 25.335-1A, Design Dive Speed

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of Availability of Proposed Advisory Circular (AC) 25.335-1A, and request for comments.

SUMMARY:

This notice announces the availability of and requests comments on a proposed advisory circular (AC) which sets forth an acceptable means, but not the only means, of demonstrating compliance with the provisions of part 25 of the Federal Aviation Regulations (FAR) related to the minimum speed margin between design cruise speed and design dive speed for transport category airplanes.

DATES:

Comments must be received on or before September 15, 2000.

ADDRESSES:

Send all comments on the proposed AC 25.335-1A to: Federal Aviation Administration, Attention: James Haynes, Airframe and Cabin Safety Branch, ANM-115, Transport Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue SW, Renton, WA 98055-4056. 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:

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

SUPPLEMENTARY INFORMATION:

Comments Invited

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 proposed AC 25.335-1A 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. The proposed AC can be found and downloaded from the Internet at http://www.faa.gov/avr/air/airhome.htm , at the link titled “Draft AC's.” A paper copy of the proposed AC may be obtained by contacting the person named above under the caption FOR FURTHER INFORMATION CONTACT.

Discussion

Section 25.335(b) requires the design dive speed, V_D, of the airplane to be established so that the design cruise speed is no greater than 0.8 times the design dive speed, or that it be based on an upset criterion initiated at the design cruise speed, V_C At altitudes where the cruise speed is limited by compressibility effects, § 25.335(b)(2) requires the margin to be not less than 0.05 Mach. Furthermore, at any altitude, the margin must be great enough to provide for atmospheric variations (such as horizontal gusts and the penetration of jet steams), instrument errors, and production variations. This AC provides a rational method for considering the atmospheric variations.