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

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of availability of proposed Advisory Circular (AC) 25.905-X and request for comments.

SUMMARY:

This notice announces the availability of and requests comment on a proposed advisory circular (AC) that provides 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 relative to design precautions that should be taken to minimize the hazards to an airplane in the event that a propeller blade fails or is released by a hub failure. 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 June 12, 2000.

ADDRESSES:

Send all comments on the proposed AC to: Federal Aviation Administration, Attn: Michael Dostert, FAA, Transport Airplane Directorate, Aircraft Certification Service, Propulsion/Mechanical Systems Branch, ANM-112, 1601 Lind Avenue SW., Renton, Washington 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:

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

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 must identify the AC by title and submit comments in duplicate to the address specified above. The Transport Airplane Directorate will consider all communications received on or before the closing date for comments before issuing the final AC.

Availability of Proposed 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” under the “Available Information” drop-down menu. A paper copy of the proposed AC may be obtained by contacting the person named above under the caption “FOR FURTHER INFORMATION CONTACT.”

Discussion

Proposed AC 25.905-X, “Minimizing the Hazards from Propeller Blade and Hub Failures,” has been prepared to provide guidance on one means of demonstrating compliance with the requirements of § 25.905, “Propellers,” of Title 14, Code of Federal Regulations (CFR) part 25, commonly referred to as part 25 of the Federal Aviation Regulations (FAR). Part 25 contains the airworthiness standards applicable to transport category airplanes.

The means of compliance described in proposed AC 25.905-X is intended to provide guidance to supplement the engineering and operational judgment that must form the basis of any compliance findings relative to paragraph § 25.905(d). That paragraph addresses design precautions that should be taken to minimize the hazards to an airplane in the event that a propeller blade fails or is released by a hub failure.

In accordance with § 25.905(d), the hazards that must be considered include:

1. Damage to structure and vital systems due to the impact of a failed or released blade, and

2. The consequent unbalance created by such failure or release.

The proposed AC addresses the hazards associated with damage created by the impact of failed or released propeller blades, and provides a discussion of design practices to minimize such hazards. However, it does not address the hazard associated with unbalance created by such failure or release.

Harmonization of Standards and Guidance

The proposed AC is based on recommendations submitted to the FAA by the Aviation Rulemaking Advisory Committee (ARAC). The FAA tasked ARAC (63 FR 50954, September 23, 1998) to provide advice and recommendations on “harmonizing” certain sections of part 25 (including § 25.1183) with the counterpart standards contained in Joint Aviation Requirements (JAR) 25. The goal of “harmonization tasks,” such as this, is to ensure that:

• Where possible, standards and guidance do not require domestic and foreign parties to manufacture or operate to different standards for each country involved; and
• The standards and guidance adopted are mutually acceptable to the FAA and the foreign aviation authorities.

The guidance contained in the proposed AC has been harmonized with that of the JAA, and provides a method of compliance that has been found acceptable to both the FAA and JAA.