Skip to Content


Technical Amendment; Airworthiness Standards: Aircraft Engines; Correction

Document Details

Information about this document as published in the Federal Register.

Document Statistics
Document page views are updated periodically throughout the day and are cumulative counts for this document including its time on Public Inspection. Counts are subject to sampling, reprocessing and revision (up or down) throughout the day.
Enhanced Content

Relevant information about this document from provides additional context. This information is not part of the official Federal Register document.

Published Document

This document has been published in the Federal Register. Use the PDF linked in the document sidebar for the official electronic format.


Technical amendment; correction.


The FAA is correcting a technical amendment published on July 5, 2012 (77 FR 39623). In that technical amendment, the FAA clarified aircraft engine vibration test requirements in the airworthiness standards. The technical amendment was in response to inquiries from applicants requesting FAA engine type certifications and aftermarket certifications, such as supplemental type certificates, parts manufacturing approvals, and repairs. We revised the regulation to clarify that engine surveys require an engine test. Representatives of industry suggested that our technical amendment was in fact, a substantive change in the regulation, not a clarification. The FAA is correcting our prior action in response to that industry claim. This document amends the FAA's regulations to reverse the changes to § 33.83(a) amendment 33-33 and restore § 33.83(a) to its previous amendment 33-17.


This corrective action becomes effective September 20, 2012.


For technical questions concerning this action, contact Dorina Mihail, Federal Aviation Administration, Engine and Propeller Directorate, Standards Staff, ANE-110, 12 New England Executive Park, Burlington, Massachusetts 01803-5229; (781) 238-7153; facsimile: (781) 238-7199; email:

For legal questions concerning this action, contact Vincent Bennett, Federal Aviation Administration, Office of Regional Counsel, ANE-7, 12 New England Executive Park, Burlington, Massachusetts 01803-5299; telephone (781) 238-7044; fax (781) 238-7055; email



On July 5, 2012, the FAA published a Technical Amendment entitled, “Airworthiness Standards: Aircraft Engine” (77 FR 39623). In that technical amendment, the FAA intended to clarify vibration test requirements in § 33.83 of 14 Code of Federal Regulations Part 33. By letter dated August 3, 2012, the Modification and Replacement Parts Association (MARPA) asserts that the rule appears to be a substantive change that should have been open to public comment. The MARPA further asserts that had the rule been open for comment, it and others would have commented that the technical amendment undermines the existing regulatory system, rather than improving it, and that it imposes unnecessary burdens on the applicant and the government with no commensurate safety benefit. We do not agree with MARPA's assertion that the rule change was substantive. However, in the interest of transparency in the rulemaking process, we are changing the language of § 33.83(a) amendment 33-33 back to the language in § 33.83(a) of the previous amendment 33-17.

List of Subjects in 14 CFR Part 33

The Correcting Amendment

In consideration of the following, the Federal Aviation Administration corrects part 33 of Title 14, Code of Federal Regulations as follows:


1. The authority citation for part 33 continues to read as follows:

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

2. Revise § 33.83(a) to read as follows:

Vibration test.

(a) Each engine must undergo vibration surveys to establish that the vibration characteristics of those components that may be subject to mechanically or aerodynamically induced vibratory excitations are acceptable throughout the declared flight envelope. The engine surveys shall be based upon an appropriate combination of experience, analysis, and component test and shall address, as a minimum, blades, vanes, rotor discs, spacers, and rotor shafts.

* * * * *

Issued in Washington, DC, on September 13, 2012.

Lirio Liu,

Acting Director, Office of Rulemaking.

[FR Doc. 2012-23105 Filed 9-19-12; 8:45 am]