AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

SUMMARY: We are adopting a new airworthiness directive (AD) for certain
Rolls-Royce Corporation (RRC) 250-C20, -C20B, and -C20R/2 turboshaft
engines. This AD was prompted by seven cases reported of released
turbine blades and shrouds, which led to loss of power and engine in-
flight shutdowns (IFSDs). This AD requires a one-time visual inspection
and fluorescent penetrant inspection (FPI) on certain 3rd and 4th stage
turbine wheels for cracks in the turbine blades. We are issuing this AD
to prevent failure of 3rd or 4th stage turbine wheel blades which could
cause engine failure and damage to the airplane.

DATES: This AD is effective August 14, 2012.

ADDRESSES: For service information identified in this AD, contact
Rolls-Royce Corporation Customer Support, P.O. Box 420, Indianapolis,
IN 46206-0420; phone: 888-255-4766 or 317-230-2720; fax: 317-230-3381,
email: royce.com">helicoptercustsupp@rolls-royce.com, and Web site: www.rolls-
royce.com. You may review copies of the referenced service information
at the FAA, Engine & Propeller Directorate, 12 New England Executive
Park, Burlington, MA. For information on the availability of this
material at the FAA, call 781-238-7125.

Examining the AD Docket

You may examine the AD docket on the Internet at http://www.regulations.gov;
or in person at the Docket Management Facility
between 9 a.m. and 5 p.m., Monday through Friday, except Federal
holidays. The AD docket contains this AD, the regulatory evaluation, any comments
received, and other information. The address for the Docket Office
(phone: 800-647-5527) is Document Management Facility, U.S. Department
of Transportation, Docket Operations, M-30, West Building Ground Floor,
Room W12-140, 1200 New Jersey Avenue SE., Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT: John Tallarovic, Aerospace Engineer,
Chicago Aircraft Certification Office, FAA, 2300 E. Devon Ave., Des
Plaines, IL 60018; phone: 847-294-8180; fax: 847-294-7834; email:
john.m.tallarovic@faa.gov.

SUPPLEMENTARY INFORMATION:

Discussion

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR
part 39 to include an AD that would apply to the specified products.
That NPRM published in the Federal Register on December 20, 2011 (76 FR
78863). That NPRM proposed to require a one-time visual inspection and
FPI on certain 3rd and 4th stage turbine wheels for cracks in the
turbine blades.

Comments

We gave the public the opportunity to participate in developing
this AD. The following presents the comments received on the proposal
and the FAA's response to each comment.

Proposed AD Applicability Clarity

One commenter said that the proposed AD applicability is unclear.
The commenter stated that the RRC Commercial Engine Bulletins (CEBs)
referenced in the proposed AD apply to specific model 250 engines in MD
Helicopter, Inc. aircraft only. However, the proposed AD appears to
cover the subject part number (P/N) wheels in three engine models in
all applications. Also, the subject P/N wheels can be installed in many
engine models in addition to the 250-C20, C20B, and C20R/2 engines
called out in the proposed AD. The original issue with the wheels
cracking was tied to specific power turbine speed ranges as manifested
in specific aircraft applications. As the proposed AD is written, there
are airframe applications where one model of installed engine would be
subject to the AD and another model being only slightly different and
identical in the power turbine section concerned, would not be subject
to the AD.
We do not agree. The proposed AD is only applicable to the model
250-C20, C20B, and C20R/2 turboshaft engines on all installations. The
affected turbine wheels, P/N 23065818 and P/N 23055944, can be
installed on other model 250 engines. However, the proposed AD is only
applicable to the model 250-C20, C20B, and C20R/2 turboshaft engines.
While RRC Alert CEB-A-1407, Revision 1, dated February 7, 2011 and CEB-
A-72-4098, Revision 1, dated February 7, 2011 (combined in one
document) is directed at engines installed on MD Helicopters Inc.
aircraft, the proposed AD is applicable to all installations of model
250-C20, C20B, and C20R/2 turboshaft engines. The service bulletins do
not establish the applicability for the proposed AD. The service
bulletins are referenced as related information only. We did not change
the AD.

Overhaul Period

One commenter pointed out that paragraph (e)(1) of the proposed AD
stated to remove the turbine wheels at the next 1,750 hour overhaul.
The overhaul period in these engines is 3,500 hours, not 1,750 hours.
We agree. We changed paragraph (e)(1) to state to remove the 3rd
stage turbine wheel, P/N 23065818, and the 4th stage turbine wheel, P/N
23055944, before accumulating 1,750-hours since last inspection.

Conclusion

We reviewed the relevant data, considered the comments received,
and determined that air safety and the public interest require adopting
the AD with the change described previously.

Costs of Compliance

We estimate that this AD will affect 500 RRC C250-C20, -C20B, and -
C20R/2 turboshaft engines installed on aircraft of U.S. registry. We
also estimate that it will take about 5 hours to perform a one-time
visual inspection and FPI of the 3rd stage turbine wheel and the 4th
stage turbine wheel for each engine. The average labor rate is $85 per
work-hour. Based on these figures, we estimate the total cost of the AD
to U.S. operators to be $212,500.

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to
issue rules on aviation safety. Subtitle I, Section 106, describes the
authority of the FAA Administrator. Subtitle VII: Aviation Programs,
describes in more detail the scope of the Agency's authority.
We are issuing this rulemaking under the authority described in
Subtitle VII, Part A, Subpart III, Section 44701: ``General
requirements.'' Under that section, Congress charges the FAA with
promoting safe flight of civil aircraft in air commerce by prescribing
regulations for practices, methods, and procedures the Administrator
finds necessary for safety in air commerce. This regulation is within
the scope of that authority because it addresses an unsafe condition
that is likely to exist or develop on products identified in this
rulemaking action.

Regulatory Findings

This AD will not have federalism implications under Executive Order
13132. This AD will not have a substantial direct effect on the States,
on the relationship between the national government and the States, or
on the distribution of power and responsibilities among the various
levels of government.
For the reasons discussed above, I certify that this AD:
(1) Is not a ``significant regulatory action'' under Executive
Order 12866,
(2) Is not a ``significant rule'' under DOT Regulatory Policies and
Procedures (44 FR 11034, February 26, 1979),
(3) Will not affect intrastate aviation in Alaska, and
(4) Will not have a significant economic impact, positive or
negative, on a substantial number of small entities under the criteria
of the Regulatory Flexibility Act.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by
reference, Safety.

Adoption of the Amendment

Accordingly, under the authority delegated to me by the
Administrator, the FAA amends 14 CFR part 39 as follows:

PART 39--AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

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

Sec. 39.13 [Amended]

2. The FAA amends Sec. 39.13 by adding the following new airworthiness
directive (AD):