DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2016-9418; Product Identifier 2016-NE-23-AD; Amendment
39-19167; AD 2018-02-14]
RIN 2120-AA64

Airworthiness Directives; Honeywell International Inc. Turboprop
and Turboshaft 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
Honeywell International Inc. (Honeywell) TPE331 turboprop and TSE331
turboshaft engines. This AD was prompted by reports that combustion
chamber case assemblies have cracked and ruptured. This AD requires
inspection of the affected combustion chamber case assembly,
replacement of those assemblies found cracked, and removal of affected
assemblies on certain TPE331 and TSE331 engines. We are issuing this AD
to address the unsafe condition on these products.

DATES: This AD is effective February 28, 2018.
The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in this AD as of February 28,
2018.

ADDRESSES: For service information identified in this final rule,
contact Honeywell International Inc., 111 S 34th Street, Phoenix, AZ
85034-2802; phone: 800-601-3099; internet: https://myaerospace.honeywell.
com/wps/portal. You may view this service
information at the FAA, Engine and Propeller Standards Branch, 1200
District Avenue, Burlington, MA. For information on the availability of
this material at the FAA, call 781-238-7759. It is also available on
the internet at http://www.regulations.gov by searching for and
locating Docket No. FAA-2016-9418.

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-2016-
9418; or in person at Docket Operations 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 Docket Operations (phone: 800-647-
5527) is Document Operations, 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: Joseph Costa, Aerospace Engineer, Los
Angeles ACO Branch, FAA, 3960 Paramount Blvd., Lakewood, CA 90712-4137;
phone: 562-627-5246; fax: 562-627-5210; email: joseph.costa@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 certain Honeywell TPE331
turboprop and TSE331 turboshaft engines. The NPRM published in the
Federal Register on April 19, 2017 (82 FR 18402). The NPRM was prompted
by reports of three accidents involving combustion chamber case
assembly ruptures. Investigations have shown numerous cracked and
ruptured combustion chamber case assemblies resulting from high
stresses in the as-designed weld joints and contributing factors due to
repair weld quality, poor maintenance and inspection practices, and
cycles-in-service. The NPRM proposed to require inspection, replacement
of the affected combustion chamber case assemblies, and removal of
affected assemblies on certain TPE331 turboprop and TSE331 turboshaft
engines. We are issuing this AD to address the unsafe condition on
these products.

Comments

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

Request To Revise Internet Address

Honeywell requested that its internet address be revised.
We agree. We revised the internet address as requested by
Honeywell.

Request To Revise Service Information

Honeywell requested that we revise the service bulletins in this AD
to reference the latest revisions.
We agree. We revised the references in this AD to Honeywell Service
Bulletins (SBs) TPE331-72-2218; TPE331-72-2235; and TPE331-72-2244 from
Revision 1 to Revision 2. However, we did not update the references to
the SB that is incorporated by reference since this SB is already at
the latest revision.

Request To Revise Discussion of Proposed AD Requirements

Honeywell requested that we reference the TSE331 turboshaft engine
in the ``Proposed AD Requirements'' section of this final rule.
We partially agree. We agree that we inadvertently omitted mention
of the TSE331 turboshaft engines from the ``Proposed AD Requirements''
section in the NPRM. We disagree with making a change to this final
rule because the ``Proposed AD Requirements'' section does not exist in
this final rule AD. We did not change this AD.

Request To Revise Discussion of Removal and Replacement Times

Honeywell requested changes to the Differences Between This
Proposed AD and the Service Information section contained within the
NPRM, recommending revision of the removal and replacement statement.
Honeywell's referenced service bulletins in the NPRM recommend a
revised compliance calendar deadline for certain redesigned combustion
chamber case assemblies. Honeywell indicated the compliance deadline is
March 31, 2021, for all redesigned combustion chamber case assemblies.
We partially agree. We agree it would be appropriate to reference
this calendar deadline in this discussion within the
NPRM. We do not agree to revise this final rule because this discussion
does not exist in this final rule. Further explanation in this final
rule is not necessary. We did not change this final rule.

Request To Revise Number of Affected Engines

Honeywell indicated its records show 11,280 engines have been
shipped with suspect combustion chamber case assemblies. Honeywell,
therefore, requested we revise the number of engines accordingly within
the Costs of Compliance section in this final rule.
We disagree. We estimate costs based on the number of affected
engines in the U.S. Registry. We estimate 50% of the engines Honeywell
shipped are in the U.S. Registry. We did not change this final rule.

Request To Revise Applicability To Include TPE331-12B Engine

Honeywell requested we revise the applicability of this AD to
include the TPE331-12B engine. Honeywell commented this engine was used
in military operations but now is operated commercially and has
experienced similar cracks in its combustion chamber case assembly.
We partially agree. The combustion chamber case assemblies
installed on these engines are subject to the same cracking as those
installed on the other affected TPE331 engines. However, in the
interest of safety, we will proceed to publish this final rule without
adding the TPE331-12B engine model. We will consider further rulemaking
action to incorporate the TPE331-12B engines.

Request To Revise Compliance Time

Honeywell, Council 331 (a TPE331 operators and maintenance group),
and an individual operator requested a change to repetitive compliance
time for the visual inspection of the combustion chamber case assembly
and suggested a specified calendar date. The commenters noted
compliance at 50 and 400 hours would not align with the fuel nozzle
inspection interval and requested clarification.
We partially agree. We interpret Honeywell's comment on the 50-hour
initial compliance interval as a request to clarify the intent of the
50-hour interval rather than as a request to change this AD. We used
the 50-hour compliance interval and not a calendar date because a grace
period is necessary to give operators time to comply with this AD.
We agree the repetitive combustion chamber case assembly
inspections should be aligned with the fuel nozzle inspections not to
exceed 450 hours. We revised this AD to indicate repetitive visual
inspection of the combustion chamber case assembly be performed before
accumulating 450 hours since last fuel nozzle inspection.

Request To Note Ruptures of Additional Combustion Chamber Case
Assemblies

Honeywell requested this final rule note that combustion chamber
case assembly ruptures occurred on parts other than those part numbers
(P/Ns) mentioned in paragraph (g) of this AD. Honeywell indicated
ruptures have occurred on other P/N combustor chamber case assemblies.
We agree. Combustion chamber case assembly ruptures have occurred
with other configurations other than those P/Ns mentioned in paragraph
(g) of this AD. We agree the public should be aware of combustion
chamber case assembly cracks that may propagate to failure or rupture
if not properly inspected and maintained. We reviewed other combustion
chamber case assembly configurations and determined the risk of rupture
for P/N 3101668-x (``x'' denotes all dash numbers) is lower than those
configurations identified in paragraph (g)(2) of this AD. We have
adequately addressed more frequent inspections and removal from service
of high risk and cracked combustion chamber case assemblies. We did not
change this AD.

Request To Remove All Combustion Chamber Case Assemblies From Service

Honeywell requested that we revise the Compliance section of this
AD to require removal from service, at the next removal from the
engine, all combustion chamber case assemblies other than the P/Ns
listed in paragraph (g)(2) of this AD. In addition, Honeywell has
performed a Continued Airworthiness Assessment, in accordance with
Advisory Circular 39-8 and determined replacement of the combustion
chamber case assemblies with redesigned assemblies is the only
corrective action that would return the product to the level of safety
intended by the original basis of certification.
We disagree. This AD requires corrective actions that reduce the
probability of combustion chamber case rupture. We identified in
paragraph (g)(2) of this AD certain combustion chamber case assemblies
with high stresses in the specified weld joint that showed higher
incidents of cracking and rupture, a short crack propagation life, and
poor crack detectability compared to other combustion chamber case
assemblies. These combustion chamber case assemblies require
replacement within the AD's specified compliance time. We did not
change this AD.

Request To Clarify Identity of Supplemental Type Certificate (STC)
Holder

Honeywell requested we clarify that Honeywell is not the holder of
the STC referenced in this AD.
We agree. Indication of ownership of the subject STC may assist
owners to identify the engine modification. We changed this AD by
identifying National Flight Services Inc. as the holder of the STC
SE383CH.

Request To Clarify Engines That Have Been Modified With Increased P3
Pressures

Honeywell requested we clarify paragraph (g) of this AD to describe
how operators would determine that their engines have been modified
with increased P3 pressures not under STC SE383CH.
We agree that operators may be unable to determine that their
engines have been modified with increased P3 case pressures. Therefore,
we will limit the applicability of paragraph (g) of this AD to the
referenced STC. We revised paragraph (g) of this AD by removing the
phrase ``modified with increased P3 pressures, including, but not
limited to . . .'' from this paragraph.''

Request To Limit Weld Repairs

Honeywell requested we revise the compliance section of this AD to
disallow any weld repairs on any combustion chamber case assemblies
that are affected by this AD.
We partially agree. We agree a weld repair is a sensitive process
that may affect the fatigue life of the combustion chamber case
assembly. We agree not to allow use of any weld repair procedures dated
before the effective date of this AD. We will assess repair procedures
of certain combustion chamber case assemblies with lower stresses on a
case-by-case basis. We did not change this AD.

Request To Prohibit Installation of Weld-Repaired Combustion Chamber
Case Assemblies

Honeywell requested the compliance section be revised to prohibit
installation of any applicable combustion chamber case assembly which
has been weld repaired.
We do not agree. In paragraphs (g)(2), (h) and (i) of this AD, we
identified the combustion chamber case configurations with the highest
risk of rupture. Prohibiting installation of all welded combustion
chamber case assemblies is unnecessary because they
do not all create the same unsafe condition. We did not change this AD.

Request To Add Further Information on Combustion Chamber Assembly
Failures

Perimeter Aviation LP (Perimeter) requested we add information to
this AD regarding the number of failures of combustion chamber
assemblies with or without the one-piece bleed pad. Perimeter requested
further information on how these failures relate to the P/N 3101668-12
combustion chamber assembly.
We agree. We note that five of the six combustion chamber case
assemblies that ruptured were assemblies without the one-piece bleed
pad. P/N 3101668-x has the one-piece bleed pad with P3 boss, which
demonstrated significantly reduced cracking between the P3 and bleed
boss; therefore, this combustion chamber case assembly is not affected
by this AD. No further changes are needed. We did not change this AD.

Request To Add More Frequent Inspections

Hancock Enterprises, Inc. and Council 331 requested we require more
frequent visual inspections and/or fluorescent penetrant inspections
during the combustion chamber case assembly's removal. They recommended
allowing the assembly be re-installed and replaced with an updated part
at the next overhaul or continuous airworthiness maintenance. Council
331 cited the non-destructive testing experience of these combustion
chamber case assemblies.
We disagree. We do not believe more frequent inspections would
maintain an adequate level of safety. Allowing the most difficult-to-
inspect and highest risk combustion chamber case assemblies back into
service would allow excessive risk. Although we agree more frequent
visual inspections would improve the probability of detecting cracks,
thereby reducing the risk of a rupture, the FAA believes the
probability of crack detection for a visual inspection of an installed
combustion chamber case assembly is generally low and will not maintain
an acceptable level of safety. We did not change this AD.

Request To Add Terminating Action

Council 331 requested that compliance with one of the service
bulletins listed in ``Other Related Service Information'' provide
terminating action for the proposed AD. Terminating action in the AD
will provide added incentive to operators in removing from service
suspect parts with a documented history of failure. Council 331
commented that, as drafted, the new redesign combustion chamber case
assembly does not eliminate the AD's compliance requirements. There
have been no known failures of the new redesign combustion chamber case
assembly.
We partially agree. We agree lower stress and improved reliability
should eliminate the need for repetitive visual inspection. We also
agree to limiting the ADs applicability to only the suspect
configurations should provide adequate safety. We therefore changed the
Applicability section of this AD to refer only to engines ``with
combustion chamber case assemblies, part numbers (P/Ns) 869728-x,
893973-x, 3101668-x, and 3102613-x, where ``x'' denotes any dash
number, installed.''
We do not agree it is necessary to specify terminating action in
this AD. This AD only applies to the specified engine models with the
specific P/N combustor chamber case assemblies installed. Therefore, a
terminating action for new combustor chamber assemblies is unnecessary.
We did not change this AD.

Revision to Engine Operating Time Limit

After further review, we revised the engine operating time limit in
paragraph (g)(2) of this AD to ``not to exceed 3,700 hours time-in-
service since last hot section inspection.'' This is equivalent to
removal of the combustion chamber case assemblies at their next removal
from the engine, which was specified in the NPRM.

Revision to Installation Prohibition

After further review, we revised the Installation Prohibition,
paragraph (i) of this AD, to limit this prohibition against
installation of affected combustion chamber case assemblies in certain
engine models. This clarification makes this prohibition consistent
with paragraph (g)(2) of this AD.

Conclusion

We reviewed the relevant data, considered the comments received,
and determined that air safety and the public interest require adopting
this final rule with the changes described previously and minor
editorial changes. We have determined that these minor changes:
[Agr]re 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 final
rule.

Related Service Information Under 1 CFR Part 51

We reviewed Honeywell SB TPE331-72-2178, Revision 0, dated May 3,
2011. Honeywell SB TPE331-72-2178 describe procedures for inspection
and removal of the affected combustion chamber case assemblies
installed on all affected engines except for the TPE331-12B engine.
This service information is reasonably available because the interested
parties have access to it through their normal course of business or by
the means identified in the ADDRESSES section.

Other Related Service Information

Honeywell has also issued SBs TPE331-72-2228, Revision 0, dated
June 12, 2014; TPE331-72-2230, Revision 0, dated June 19, 2014; TPE331-
72-2218, Revision 2, dated February 18, 2017; TPE331-72-2244, Revision
2, dated March 20 2017; TPE331-72-2235, Revision 2, dated February 18,
2017; TPE331-72-2281, Revision 0, dated July 22, 2016; TPE331-72-2294,
Revision 0, dated December 22, 2016; and TSE331-72-2245, Revision 0,
dated November 11, 2016. These SBs provide guidance on replacement of
the affected combustion chamber case assemblies.

Costs of Compliance

We estimate that this AD affects 5,644 engines installed on
airplanes of U.S. registry.
We estimate the following costs to comply with this AD:

Estimated Costs

We estimate the following costs to do any necessary replacements
that would be required based on the results of the proposed inspection.
We estimate that 158 engines will need this replacement during the
first year of inspection.

On-Condition 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
associated appliances to the Manager, Engine and Propeller Standards
Branch, Policy and Innovation Division.

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):