DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2011-0961; Product Identifier 2011-NE-22-AD; Amendment
39-19023; AD 2017-18-14]
RIN 2120-AA64

Airworthiness Directives; Rolls-Royce Corporation Turboshaft Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: We are superseding Airworthiness Directive (AD) 2015-02-22 for
certain Rolls-Royce Corporation (RRC) model 250 turboprop and
turboshaft engines. AD 2015-02-22 required repetitive visual
inspections and fluorescent-penetrant inspection (FPIs) on certain 3rd-
stage and 4th-stage turbine wheels for cracks in the turbine wheel
blades. This AD requires repetitive visual inspections and FPIs of 3rd-
stage turbine wheels while removing from service 4th-stage turbine
wheels. We are also revising the applicability to remove all RRC
turboprop engines and add additional turboshaft engines. This AD was
prompted by our finding that it is necessary to remove the 4th-stage
wheels at the next inspection. We are issuing this AD to address the
unsafe condition on these products.

DATES: This AD is effective October 13, 2017.

ADDRESSES: See the FOR FURTHER INFORMATION CONTACT section.

Examining the AD Docket

You may examine the AD docket on the Internet at http://www.regulations.
gov by searching for and locating Docket No. FAA-2011-
0961; 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 final rule, 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,
FAA, Chicago ACO Branch, Compliance and Airworthiness Division, 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 supersede AD 2015-02-22, Amendment 39-18090 (80 FR 5452,
February 2, 2015), (``AD 2015-02-22''). AD 2015-02-22 applied to
certain RRC 250-B17, -B17B, -B17C, -B17D, -B17E, -B17F, -B17F/1, -B17F/
2, turboprop engines; and 250-C20, -C20B, -C20F, -C20J, -C20R, -C20R/1,
-C20R/2, -C20R/4, -C20S, and -C20W turboshaft engines. The NPRM
published in the Federal Register on March 29, 2017 (82 FR 15474). The
NPRM was prompted by our determination that it is necessary to remove
the 4th-stage wheels at the next inspection. The NPRM proposed to
require repetitive visual inspections and FPIs of 3rd-stage turbine
wheels while removing from service 4th-stage turbine wheels. We are
also revising the applicability to remove all RRC turboprop engines and
add additional turboshaft engines. We are issuing this AD to prevent
failure of the 3rd-stage and 4th-stage turbine wheel blades, damage to
the engine, and damage to the aircraft.

Comments

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

Request To Remove Certain 3rd Stage Turbine Wheel From AD

RRC requested that we remove references in this AD to the 3rd stage
turbine wheel, part number (P/N) RR30000236, installed on the RRC 250-
C300/A1 and 250-C300/B1 turboshaft engines. RRC indicated that 3rd
stage turbine wheels, P/N RR30000236, are not susceptible to cracks.
RRC noted that there have been no cracks observed on 3rd stage wheels
installed on RRC 250-C300/A1 or 250-C300B/1 engines.
We agree. The 3rd stage turbine wheel, P/N RR30000236, installed on
RRC 250-C300/A1 and 250-C300/B1 engines does not require inspections.
They are subject to less severe operating conditions and are not
susceptible to this type of failure. We removed references to the 3rd
stage turbine wheel, P/N RR30000236, from this AD.

Request To Revise Power Turbine Reference

RRC requested that we change references in this AD from ``power
turbine'' to ``turbine.'' RRC noted that this AD should refer to the
entire turbine module rather than just to the power turbine. RRC also
commented that the risk analysis for this AD is based on changing the
parts anytime the turbine is being serviced, not just the power
turbine. Revising the reference in this AD to ``turbine'' would remove
the affected 4th stage turbine wheels from the fleet in a shorter time
period since the actions specified in this AD are to be complied with
whenever the turbine is at the shop and is dissembled for any reason,
or at the next turbine wheel replacement, whichever occurs first.
We agree. We changed the reference in the Compliance section of
this AD from ``power turbine'' to ``turbine.''
RRC also commented that changing the references to ``turbine''
would allow for removal of the Definition section from this AD.
We disagree. The term ``engine shop visit'' is used as one of the
criteria in this AD to determine when an inspection of affected
applicable turbine wheels is required. Given that ``engine shop visit''
may be interpreted in different ways, we provide a definition for this
term in this AD. We did not change this AD.

Request To Clarify Removal of Blades With Cracks From Service

RRC requested that we revise the Compliance section of this AD so
that it does not require removal from service all turbine wheels found
with cracks. RRC commented that only certain cracks are related to this
AD and are a safety concern.
We agree. The intent of this AD is to address cracks at the
trailing edge of the turbine wheel blades, near the fillet at the rim.
The maintenance manuals for these engines allow certain cracks in areas
of the turbine wheels not subject to this AD. Engines may still operate
safety with turbine wheels that have allowable cracks. We revised
paragraph (f)(3) of this AD to refer to cracks found at the trailing
edge, near the fillet at the rim, of the turbine blades.

Revision to Costs of Compliance

We reduced the estimated cost of inspection of 3rd stage wheels
from $320,365 to $288,320 since we removed the 3rd stage wheel, P/N
RR30000236, from the applicability of this AD. As noted in our previous
comment response, these P/N 3rd stage wheels are not subject to the
unsafe condition identified in this AD.

Conclusion

We reviewed the relevant data, considered the comments received,
and determined that air safety and the public interest require adopting
this AD with the changes described previously and minor editorial
changes. We have determined that these minor changes:
Are consistent with the intent that was proposed in the
NPRM for correcting the unsafe condition; and
Do not add any additional burden upon the public than was
already proposed in the NPRM.
We also determined that these changes will not increase the
economic burden on any operator or increase the scope of this AD.

Costs of Compliance

We estimate that this AD affects 3,769 engines installed on
airplanes of U.S. registry.
We estimate the following costs to comply with this AD:

Estimated Costs

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.
This AD is issued in accordance with authority delegated by the
Executive Director, Aircraft Certification Service, as authorized by
FAA Order 8000.51C. In accordance with that order, issuance of ADs is
normally a function of the Compliance and Airworthiness Division, but
during this transition period, the Executive Director has delegated the
authority to issue ADs applicable to engines, propellers, and
appliances to the Manager, Engine and Propeller Standards Branch,
Policy and Innovation Division.

Regulatory Findings

We have determined that 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 to the extent
that it justifies making a regulatory distinction, 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 removing Airworthiness Directive (AD)
2015-02-22, Amendment 39-18090 (80 FR 5452, February 2, 2015), and
adding the following new AD: