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Proposed Advisory Circulars; Vibration and Fatigue Evaluation of Airplane Propellers and Guidance Material for Fatigue Limit Tests and Composite Blade Fatigue Substantiation

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Federal Aviation Administration, DOT.


Notice of availability of proposed advisory circulars and request for comments.


The Federal Aviation Administration (FAA) announces the availability of two draft advisory circulars (ACs): AC No. 20-66 [DRAFT], Vibration and Fatigue Evaluation of Airplane Propellers, and AC 35.37-1[DRAFT], Guidance Material for Fatigue Limit Tests and Composite Blade Fatigue Substantiation.


Comments must be received on or before April 2, 2001.


Send all comments on the proposed ACs to the Federal Aviation Administration, Attn: Engine and Propeller Standards Staff, ANE-110, 12 New England Executive Park, Burlington, MA 01803-5299.

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Jay Turnberg, Engine and Propeller Standards Staff, ANE-110, at the above address; telephone: (781) 238-7116; fax: (781) 238-7199; e-mail:

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Comments Invited

A copy of the subject ACs may be obtained by contacting the person named under FOR FURTHER INFORMATION CONTACT or by downloading the draft ACs from the following Internet website:​avr/​air/​acs/​draftach.htm. The FAA invites interested parties to comment on the proposed ACs. Comments should identify the subject of the AC and be submitted to the individual identified under FOR FURTHER INFORMATION CONTACT. The FAA will consider all communications received by the closing date before issuing the final ACs.


The FAA issued AC 20-66, “Vibration Evaluation of Airplane Propellers,” on January 29, 1970. The FAA issued AC 35.37-1, Change 1, “Composite Propeller Blade Fatigue Substantiation,” on September 7, 1993. Since the issuance of these ACs, there have been substantial technological advances in the design, fabrication and continued airworthiness of propellers. These advances have involved the introduction of composite materials, the development of damage tolerance methodologies, and a better understanding of the propeller operating environment.

The FAA has decided to revise AC 20-66 and AC 35.37-1 simultaneously, based on the relationship between the propeller fatigue limits developed to show compliance with § 35.37, Fatigue Start Printed Page 8461limit tests, and the propeller vibration evaluation conducted on an airplane to show compliance with §§ 23.907 and 25.907, Propeller vibration. To update these advisory circulars, the FAA has incorporated substantial contributions from the Propeller Harmonization Working Group (PHWG) tasked on August 17, 1994, by the Aviation Rulemaking Advisory Committee (ARAC). Part of the PHWG task was to clarify and redefine existing propeller requirements to include new standards to reflect recent advancement in the design and construction of composite material propellers. The proposed ACs would revise the Current ACs to address recent technological advances.

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Authority: 49 U.S.C. 106(g), 40113, 44701-44702, 44704.

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Issued in Burlington, Massachusetts, on January 19, 2001.

Jay J. Pardee,

Manager, Engine and Propeller Directorate, Aircraft Certification Service.

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[FR Doc. 01-2645 Filed 1-30-01; 8:45 am]