DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2014-0521; Directorate Identifier 2014-NE-11-AD;
Amendment 39-18104; AD 2015-04-02]
RIN 2120-AA64

Airworthiness Directives; CFM International S.A. Turbofan Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

-----------------------------------------------------------------------

SUMMARY: We are adopting a new airworthiness directive (AD) for all CFM
International S.A. (CFM) CFM56-7B series turbofan engines. This AD was
prompted by a dual engine thrust instability event that resulted in the
overspeed and in-flight shutdown (IFSD) of one engine. This AD requires
modification of the engine by removing
full authority digital engine control (FADEC) software, version 7.B.V4
or earlier, installed in the electronic engine controls (EECs) on
CFM56-7B engines. We are issuing this AD to prevent a thrust
instability event, which could lead to overspeed and IFSD of one or
more engines, loss of thrust control, damage to the engine, and damage
to the airplane.

DATES: This AD is effective March 31, 2015.

ADDRESSES: For service information identified in this AD, contact CFM
International Inc., Aviation Operations Center, 1 Neumann Way, M/D Room
285, Cincinnati, OH 45125; phone: 877-432-3272; fax: 877-432-3329;
email: geae.aoc@ge.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. It is also available on the Internet at
http://www.regulations.gov by searching for and locating Docket No.
FAA-2014-0521.

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-2014-
0521; 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: Kyle Gustafson, Aerospace Engineer,
Engine Certification Office, FAA, Engine & Propeller Directorate, 12
New England Executive Park, Burlington, MA 01803; phone: 781-238-7183;
fax: 781-238-7199; email: kyle.gustafson@faa.gov.

SUPPLEMENTARY INFORMATION:

Discussion

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR
part 39 by adding an AD that would apply to all CFM CFM56-7B series
turbofan engines. The NPRM published in the Federal Register on October
2, 2014 (79 FR 59467). The NPRM was prompted by reports of dual-engine
thrust instability events on CFM56-7B turbofan engines that resulted in
overspeed and IFSD of one engine. These resulted from water-borne
contamination of the fuel being supplied to the engine which had an
adverse effect on the response of the fuel metering valve (FMV) in the
hydro-mechanical unit (HMU). CFM has modified its FADEC software to
compensate for compromised fuel within the HMU and improved the
response of the FMV, thereby mitigating these thrust instability
events. The NPRM proposed to require modification of the engine by
removing FADEC software, version 7.B.V4 or earlier, installed in the
EECs on CFM56-7B engines. We are issuing this AD to prevent a thrust
instability event, which could lead to overspeed and IFSD of one or
more engines, loss of thrust control, damage to the engine, and damage
to the airplane.

Comments

We gave the public the opportunity to participate in developing
this AD. The following presents the comments received on the NPRM (79
FR 59467, October 2, 2014) and the FAA's response to each comment.

Request To Change Emphasis From Software Removal to Software
Installation

Delta Air Lines (DAL) and American Air Lines (AAL) requested that
we change wording in the AD to emphasize installation of an eligible
software standard rather than removal of the ineligible software
standard. They suggested that we add this sentence to compliance
paragraph (e): ``Within 6 months of the effective date of this AD,
modify the engine by installing FADEC software version 7.B.W, released
by CFM Service Bulletins 73-0203 and 73-0204, or later approved
software versions.'' DAL and AAL state that the Boeing 737NG Aircraft
Maintenance Manual does not contain a removal step but rather guides
how to overwrite previous software with eligible software.
We disagree. The purpose of this AD is to require removal of
software standard 7.B.V4, or earlier, to correct the unsafe condition.
Overwriting a previously installed software standard with a software
standard eligible for installation is an acceptable method for removing
an affected software standard. We did not change this AD.

Request To Require Use of Software EEC Software Standard 7.B.W or Later

DAL and AAL requested that we revise paragraph (h)(2) of FAA AD
2012-05-02 (77 FR 20511, April 5, 2012) (``AD 2012-05-02'') to state
that EEC software standard 7.B.W or later is required. AD 2012-05-02
requires inspection and modification to the Boeing 737NG thrust
reversers, and also requires, in paragraph (h)(2), installation of
software standard 7.B.R3 on affected engines. Since AD 2012-05-02 was
issued, new versions of software have been released, requiring
alternative methods of compliance (AMOCs) to allow installation of
versions later than software standard 7.B.R3. The requested change to
AD 2012-05-02 would bring AD 2012-05-02 and this AD into agreement on
the required airplane configuration.
We disagree. The current version of the software standard, 7.B.W,
also addresses the thrust reverser unsafe condition and is approved as
an AMOC for AD 2012-05-02. We did not change this AD.

Request To Change Description of the Unsafe Condition

The Boeing Company (Boeing) and CFM requested that we change the
wording of the unsafe condition to ``We are proposing this AD to
mitigate characteristics of a thrust instability event; without
mitigation, thrust instability events could potentially lead to engine
overspeed and IFSD of one or more engines, loss of thrust control, and
damage to the airplane.'' The commenters state that the EEC cannot
prevent the occurrence of the events, but it can effectively mitigate
the characteristics of the events.
We disagree. While the work to prevent the root cause of fuel
contamination continues, the purpose of the FADEC software and this AD
is to prevent the events described in the unsafe condition. We did not
change this AD.

Request To Change Wording in the Description Paragraph

CFM and Boeing requested that we change the wording of two
sentences in the Description paragraph to ``These resulted from water-
borne contamination of the fuel being supplied to the engine which had
an adverse effect on the response of the FMV in the HMU. CFM has
modified its FADEC software to compensate for compromised fuel within
the HMU and improve the response of the fuel control valve, thereby
mitigating these thrust instability events.''
We agree. We changed the wording of the two sentences in the
Description paragraph to be more correct and accurate.

Request To Clarify a Sentence in the Relevant Service Information
Paragraph

Boeing requested, for clarity, that in the Relevant Service
Information paragraph of the preamble we add the words ``post 7.B.V4''
to describe the FADEC software. Boeing requested that the changed
sentence read: ``The SBs describe the procedures for the introduction
of new FADEC software, post 7.B.V4, for the EECs.''
We disagree. The information in this AD provides the necessary
information for compliance. No additional clarification is required.
Furthermore, the Relevant Service Information paragraph, which appeared
in the preamble of the NPRM (79 FR 59467, October 2, 2014), does not
appear in this AD. We did not change this AD.

Request That We Correct Our References to the FADEC Software Standard

CFM requested that we change all references to the software
standard throughout this AD from ``7BV4'' to ``7.B.V4'' because that is
the correct way to reference the software standard.
We agree. We changed all references to the software standard
throughout this AD to the correct nomenclature.

Request To Add a Table Specifying the Software Versions To Remove

Boeing requested that for clarity we include in this AD a table
that would show the software versions, by part number, that should be
removed as a result of this AD.
We disagree. The information in this AD provides the necessary
information for compliance. No additional clarification is required. We
did not change this AD.

Additional Changes

In our review of the NPRM, we found that we failed to include the
prohibition against operating any aircraft configured with one engine
with FADEC software version 7.B.V4 or earlier, installed, and the other
engine with an eligible FADEC software version installed. This
prohibition is in SB CFM Service Bulletin (SB) No. CFM56-7B S/B 73-
0203, dated June 9, 2014 and CFM No. SB CFM56-7B S/B 73-0204, dated
June 9, 2014. We added the prohibition to this AD.

Agreement With the Proposed AD

One anonymous commenter expressed agreement with 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. We have determined that
these minor changes:
[Agr]re consistent with the intent that was proposed in
the NPRM (79 FR 59467, October 2, 2014) for correcting the unsafe
condition; and
Do not add any additional burden upon the public than was
already proposed in the NPRM (79 FR 59467, October 2, 2014).
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 would affect about 2,921 engines installed
on airplanes of U.S. registry. We also estimate that it would take
about 1 hour per engine to comply with this AD. The average labor rate
is $85 per hour. Parts cost is zero. Based on these figures, we
estimate the cost of this AD on U.S. operators to be $248,285.

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
(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):