Airworthiness Directives; Engine Alliance Turbofan Engines

[Federal Register Volume 78, Number 115 (Friday, June 14, 2013)]
[Rules and Regulations]
[Pages 35747-35749]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2013-14040]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2012-1329; Directorate Identifier 2012-NE-46-AD; 
Amendment 39-17479; AD 2013-12-02]
RIN 2120-AA64


Airworthiness Directives; Engine Alliance Turbofan Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: We are adopting a new airworthiness directive (AD) for certain 
Engine Alliance GP7270 and GP7277 turbofan engines. This AD was 
prompted by damage to the high-pressure compressor (HPC) stage 7-9 
spool caused by failure of the baffle plate feature on affected HPC 
stage 6 disks. This AD requires initial and repetitive borescope 
inspections of the baffle plate feature and removal from service of the 
HPC stage 6 disk if the plate is missing material. This AD also 
requires mandatory removal from service of these HPC stage 6 disks at 
the next HPC module exposure. We are issuing this AD to prevent failure 
of the HPC stage 7-9 spool, uncontained engine failure, and damage to 
the airplane.

DATES: This AD is effective July 19, 2013.

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: Martin Adler, Aerospace Engineer,

[[Page 35748]]

Engine & Propeller Directorate, FAA, 12 New England Executive Park, 
Burlington, MA 01803; phone: 781-238-7157; fax: 781-238-7199; email: 
[email protected].

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 February 7, 2013 (78 FR 
9003). That NPRM proposed to require initial and repetitive borescope 
inspections of the HPC stage 6 disk baffle plate feature and removal 
from service of any HPC stage 6 disk, part number (P/N) 382-100-505-0, 
before further flight if the feature is missing any material. That NPRM 
also proposed to require mandatory removal from service of these HPC 
stage 6 disks at the next HPC module exposure, but no later than 
accumulating 6,800 cycles-since-new on the disk.

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.

Request To Allow Continue-In-Service Limits for the Baffle Plate 
Feature

    Engine Alliance and Korean Airlines requested that we allow 
continue-in-service limits for the baffle plate feature. Engine 
Alliance stated that they have performed extensive analysis showing 
that the risk in doing so, is minimal. Both commenters point out the 
potential inconveniences to the flying public, and the potential 
economical and logistical impacts on air carriers.
    We agree. We changed paragraph (f)(4) of the AD to state to remove 
the HPC stage 6 disk within 50 additional cycles-in-service, if the 
baffle plate feature is found cracked or missing material.

Request To Remove References to Damage Causing Cracks to the HPC 7-9 
Spool

    Engine Alliance requested that we remove the reference to damage 
causing cracks to the HPC 7-9 spool, in the Discussion paragraph of the 
NPRM (78 FR 9003, February 7, 2013). Engine Alliance stated that there 
has been no cracking of the spools related to the baffle plate feature 
problem, to-date, but there is potential for cracking, and they 
suggested that we state there is potential for cracking.
    We partially agree. We agree that there has been no cracking yet. 
We do not agree with stating there is potential for cracking, because 
we wouldn't be issuing an AD if cracking couldn't happen. We did not 
change the AD.

Request To Include Engine Alliance Service Bulletins (SBs)

    Engine Alliance and Korean Airlines requested that we include 
Engine Alliance SBs No.s EAGP7-72-237 and EAGP7-72-240 as terminating 
action for this AD. The SBs introduce the new design of the HPC stage 6 
disk either by repair or a new part, which eliminates the unsafe 
condition.
    We partially agree. We agree that a repaired HPC stage 6 disk 
should be allowed to be installed as a terminating action for the AD, 
as well as installing the new P/N HPC stage 6 disk. We changed 
paragraph (g) in the AD from ``At next HPC module exposure, but not to 
exceed 6,800 CSN on the HPC stage 6 disk, remove the HPC stage 6 disk, 
P/N 382-100-505-0, from service'' to allow use of the repaired part. 
Paragraph (g) of this AD now reads: ``At next HPC module exposure, but 
not to exceed 6,800 CSN on the HPC stage 6 disk, remove the HPC stage 6 
disk, P/N 382-100-505-0, from the engine.'' We do not agree with 
stipulating the SBs as terminating actions because we do not want to 
prevent future configurations from being terminating action. However, 
we listed those SBs under Related Information in the AD.

Request To Define When Undamaged Part Replacement Is Required

    Engine Alliance requested that we define when undamaged part 
replacement is required, from module level to rotor assembly exposure. 
They stated that disk removal involves a full teardown of the 
compressor module, which can only be performed at specialized repair 
facilities. There is maintenance that can be performed at other 
facilities not qualified for a full teardown, which could involve 
removal and installation of a complete compressor module.
    We agree. We changed paragraph (i) in the AD from: ``For the 
purpose of this AD, HPC module exposure is defined as separation of the 
flanges between the compressor case and the combustion diffuser case'' 
to: ``For the purpose of this AD, HPC module exposure is defined as 
disassembly of the compressor to where the HPC rotor assembly is 
removed and accessible.''

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 changes described previously. We have determined that 
these minor changes:
    <bullet> [Agr]re consistent with the intent that was proposed in 
the NPRM (78 FR 9003, February 7, 2013) for correcting the unsafe 
condition; and
    <bullet> Do not add any additional burden upon the public than was 
already proposed in the NPRM (78 FR 9003, February 7, 2013).
    We also determined that these changes will not increase the 
economic burden on any operator or increase the scope of the AD.

Costs of Compliance

    We estimate that this AD will affect no engines installed on 
airplanes of U.S. registry, and the cost to U.S. operators to be $0.

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 to the extent 
that it justifies making a regulatory distinction, and

[[Page 35749]]

    (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

0
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]

0
2. The FAA amends Sec.  39.13 by adding the following new airworthiness 
directive (AD):

2013-12-02 Engine Alliance: Amendment 39-17479; Docket No. FAA-2012-
1329; Directorate Identifier 2012-NE-46-AD.

(a) Effective Date

    This AD is effective July 19, 2013.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to Engine Alliance GP7270 and GP7277 turbofan 
engines with a high-pressure compressor (HPC) stage 6 disk, part 
number (P/N) 382-100-505-0, installed.

(d) Unsafe Condition

    This AD was prompted by damage to the HPC stage 7-9 spool caused 
by failure of the baffle plate feature on affected HPC stage 6 
disks. We are issuing this AD to prevent failure of the HPC stage 7-
9 spool, uncontained engine failure, and damage to the airplane.

(e) Compliance

    Comply with this AD within the compliance times specified, 
unless already done.

(f) Borescope Inspections

    (1) For HPC stage 6 disks with fewer than 1,000 cycles- since- 
new (CSN) on the effective date of this AD, initially borescope 
inspect the baffle plate feature on the disk (360 degrees) before 
accumulating 1,500 CSN.
    (2) For HPC stage 6 disks with 1,000 CSN or more on the 
effective date of this AD, initially borescope inspect the baffle 
plate feature on the disk (360 degrees) within the next 500 cycles-
in-service (CIS).
    (3) Thereafter, repetitively borescope inspect the baffle plate 
feature on the disk (360 degrees) within every 500 CIS.
    (4) Remove the HPC stage 6 disk within 50 additional CIS, if the 
baffle plate feature is found cracked or missing material.

(g) Mandatory Removal From Service of Affected HPC Stage 6 Disks

    At next HPC module exposure, but not to exceed 6,800 CSN on the 
HPC stage 6 disk, remove the HPC stage 6 disk, P/N 382-100-505-0, 
from the engine.

(h) Installation Prohibition

    After the effective date of this AD, do not install any HPC 
stage 6 disk, P/N 382-100-505-0, into any HPC module.

(i) Definition

    For the purpose of this AD, HPC module exposure is defined as 
disassembly of the compressor to where the HPC rotor assembly is 
removed and accessible.

(j) Alternative Methods of Compliance (AMOCs)

    The Manager, Engine Certification Office, may approve AMOCs for 
this AD. Use the procedures found in 14 CFR 39.19 to make your 
request.

(k) Related Information

    (1) For more information about this AD, contact Martin Adler, 
Aerospace Engineer, Engine & Propeller Directorate, FAA, 12 New 
England Executive Park, Burlington, MA 01803; phone: 781-238-7157; 
fax: 781-238-7199; email: [email protected].
    (2) Engine Alliance Service Bulletin Nos. EAGP7-72-236, EAGP7-
72-237, and EAGP7-72-240, pertain to the subject of this AD.
    (3) For service information identified in this AD, contact 
Engine Alliance, 411 Silver Lane, East Hartford, CT 06118, phone: 
800-565-0140; Web site: https://www.engineallianceportal.com. You 
may view this 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.

(l) Material Incorporated by Reference

    None.

    Issued in Burlington, Massachusetts, on June 7, 2013.
Robert J. Ganley,
Acting Assistant Manager, Engine & Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 2013-14040 Filed 6-13-13; 8:45 am]
BILLING CODE 4910-13-P

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