
[Federal Register Volume 77, Number 129 (Thursday, July 5, 2012)]
[Rules and Regulations]
[Pages 39623-39624]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2012-16290]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 33

[Amendment No. 33-33]


Airworthiness Standards: Aircraft Engines; Technical Amendment

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule; technical amendment.

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SUMMARY: This amendment clarifies aircraft engine vibration test 
requirements in the airworthiness standards. The clarification is 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 are 
revising the regulations to clarify that ``engine surveys'' require an 
engine test. The change is not substantive in nature, and will not 
impose any additional burden on any person.

[[Page 39624]]


DATES: This amendment becomes effective July 5, 2012.

FOR FURTHER INFORMATION CONTACT: 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: dorina.mihail@faa.gov.
    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 
vincent.bennett@faa.gov.

SUPPLEMENTARY INFORMATION:

Background

    The airworthiness standards in Sec.  33.83 refer to engine surveys, 
vibration surveys, vibration test, or simply surveys with the intent to 
prescribe engine vibration surveys conducted by the means of an engine 
test. This intent has been applied since the regulation was first 
issued in 1964 and is common certification practice. However, FAA 
continues to receive requests for clarification in regard to the 
``engine surveys'' required in the second sentence of Sec.  33.83(a). 
The requested clarification was whether an ``appropriate combination of 
experience, analysis, and component test'' is acceptable in lieu of an 
engine test. We are revising Sec.  33.83(a) to clarify that the 
applicants must conduct the engine surveys by the means of an engine 
test, and that the applicants may use an ``appropriate combination of 
experience, analysis, and component test'' in support of conducting the 
engine test. This clarification is not substantive in nature, and will 
not impose any additional burden on any person.

List of Subjects in 14 CFR Part 33

    Aircraft, Aviation safety.

The Amendment

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

PART 33--AIRWORTHINESS STANDARDS: AIRCRAFT ENGINES

0
1. The authority citation for part 33 continues to read as follows:

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

0
2. Revise Sec.  33.83(a) to read as follows:


Sec.  33.83  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. Compliance with 
this section must be demonstrated by engine test, and must address, as 
a minimum, blades, vanes, rotor discs, spacers, and rotor shafts. The 
conduct of the engine test should be based on an appropriate 
combination of experience, analysis, and component test.
* * * * *

    Issued in Washington, DC, on June 7, 2012.
Lirio Liu,
Acting Director, Office of Rulemaking.
[FR Doc. 2012-16290 Filed 7-3-12; 8:45 am]
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