Advisory Circular 25.905-1, Minimizing the Hazards From Propeller Blade and Hub Failures

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of issuance of advisory circular.

SUMMARY:

This notice announces the issuance of Advisory Circular (AC) 25.905-1, Minimizing the Hazards from Propeller Blade and Hub Failures. The AC describes methods acceptable to the Administrator for showing compliance with the airworthiness standards for propeller installations on transport category airplanes. The guidance provided in the AC supplements the engineering and operational judgment that must form the basis of any compliance findings on design precautions to minimize the hazards to an airplane if a propeller blade fails or is released by a hub failure.

DATES:

Advisory Circular 25.905-1 was issued on September 27, 2000, by the Manager of the Transport Airplane Directorate, Aircraft Certification Service, Federal Aviation Administration.

How to Obtain Copies:

You can get a paper copy of AC 25.905-1 by writing to U.S. Department of Transportation, Subsequent Distribution Center, SVC-121.23, Ardmore East Business Center, 3341 Q 75th Avenue, Landover, Maryland 20785. You also can find the AC on the Internet at http://www.faa.gov/avr/air/airhome.htm,, at the link titled “Advisory Circulars” under the “Available Information” drop-down menu.

FOR FURTHER INFORMATION CONTACT:

For technical issues, contact Michael Dostert, FAA, Transport Airplane Directorate, Aircraft Certification Service, Propulsion/Mechanical Systems Branch, ANM-112, 1601 Lind Avenue SW., Renton, Washington 98055-4056; telephone (425) 227-2132; fax (425) 227-1320; e-mail mike.dostert@faa.gov.

For other information contact: Jill DeMarco, FAA, Transport Airplane Directorate, Program Management Branch, ANM-114, 1601 Lind Avenue SW., Renton, Washington 98055-4056; telephone (425) 227-1313; fax (425) 227-1320.

SUPPLEMENTARY INFORMATION:

Discussion of Comments

On March 31, 2000, the FAA issued a notice of the availability of proposed Advisory Circular (AC) 25.905-X, “Minimizing the Hazards from Propeller Blade and Hub Failures.” That notice was published in the Federal Register on April 11, 2000 (65 FR 19423), and requested public comment on the proposed AC document. Only one commenter filed comments to the proposed AC.

The commenter points out that, in the discussion of the “Purpose” of the AC, the FAA stated that the AC does not address hazards associated with unbalance created by blade release or similar failures. However, unbalance vibratory forces could be significant and can interfere with the required corrective actions. The commenter asks why the FAA did not cover this issue in the AC, and if we will address it in another AC.

We agree that imbalance is a critical issue following a propeller or hub failure. Structural issues and the flightcrew's ability to cope with the failure are of concern. We are considering separate action to address these issues. We have asked the Aviation Rulemaking Advisory Committee (ARAC) to review these issues and provide recommendations for further action.