DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2014-0108; Directorate Identifier 2013-CE-052-AD;
Amendment 39-18063; AD 2015-01-02]
RIN 2120-AA64

Airworthiness Directives; Mitsubishi Heavy Industries, Ltd.
Airplanes

AGENCY: Federal Aviation Administration (FAA), Department of
Transportation (DOT).

ACTION: Final rule.

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

SUMMARY: We are adopting a new airworthiness directive (AD) for certain
Mitsubishi Heavy Industries, Ltd. Models MU-2B-30, MU-2B-35, MU-2B-36,
MU-2B-36A, and MU-2B-60 airplanes. This AD results from mandatory
continuing airworthiness information (MCAI) issued by an aviation
authority of another country to identify and correct an unsafe
condition on an aviation product. The MCAI describes the unsafe
condition as stress corrosion cracking in the flanges of the airframe
at stations 4610 and 5605. We are issuing this AD to require actions to
address the unsafe condition on these products.

DATES: This AD is effective February 26, 2015.
The Director of the Federal Register approved the incorporation by
reference of certain publications listed in the AD as of February 26,
2015.

ADDRESSES: You may examine the AD docket on the Internet at http://
www.regulations.gov by searching for and locating Docket No. FAA-2014-
0108; or in person at 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 service information identified in this AD, contact Mitsubishi
Heavy Industries America, Inc., c/o Turbine Aircraft Services, Inc.,
4550 Jimmy Doolittle Drive, Addison, Texas 75001; telephone: (972) 248-
3108, ext. 209; fax: (972) 248-3321; Internet: http://mu-2aircraft.com.
You may view this referenced service information at the FAA, Small
Airplane Directorate, 901 Locust, Kansas City, Missouri 64106. For
information on the availability of this material at the FAA, call (816)
329-4148.

FOR FURTHER INFORMATION CONTACT: Kenneth A. Cook, Aerospace Engineer,
FAA, Fort Worth Airplane Certification Office (ACO), 2601 Meacham
Blvd., Fort Worth, Texas 76137; telephone: (817) 222-5475; fax: (817)
222-5960; email: Kenneth.A.Cook@faa.gov.

SUPPLEMENTARY INFORMATION:

Discussion

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR
part 39 to add an AD that would apply to certain Mitsubishi Heavy
Industries, Ltd. (MHI) Models MU-2B-30, MU-2B-35, MU-2B-36, MU-2B-36A,
and MU-2B-60 airplanes. The NPRM was published in the Federal Register
on February 26, 2014 (79 FR 10710). The NPRM proposed to correct an
unsafe condition for the specified products and was based on mandatory
continuing airworthiness information (MCAI) originated by an aviation
authority of another country.
The Japan Civil Aviation Bureau (JCAB), which is the aviation
authority for Japan, has issued AD No. TCD-8231-2013, dated August 6,
2013 (referred to after this as ``the MCAI''), to correct an unsafe
condition for certain MHI Models MU-2B-30, MU-2B-35, and MU-2B-36
airplanes. You may examine the MCAI on the Internet at http://www.regulations.gov/#!documentDetail;D=FAA-2014-0108-0002.
The JCAB has informed us that as part of the MHI continuing aging
aircraft program, Models MU-2B-30, MU-2B-35, and MU-2B-36 airplanes
were subjected to detailed teardown inspections. During the
inspections, structural cracks in the flanges of some long body
airplane frames were found at frame station (STA) 4610 and STA 5605. It
has been determined that the structural cracks resulted from stress
corrosion.
Japan is the State of Design for (MHI Models MU-2B-30, MU-2B-35,
and MU-2B-36, which the MCAI applies to, and the United States is the
State of Design for MHI Models MU-2B-36A and MU-2B-60 airplanes. Since
the Models MU-2B-36A and MU-2B-60 airplanes are of similar type design,
the same structural cracks could exist.

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 Extend Comment Period

Mike Ciholas and seven others stated that they need more time for
discussions at seminars and to obtain more information from MHI and
Turbine Aircraft Services.
The commenters requested the comment period be extended to allow
for more time to gather and analyze data.
We do not agree with the commenters. We have considered the request
and have determined sufficient evidence and data exist, specifically
information recently from MHI on the inspections of 18 of the 119
airplanes in the U.S. fleet that indicate that 8 of them were cracked.
Out of these eight, four have been removed from service. Based on the
data presented in the NPRM and this more detailed information provided
by MHI, the location of cracks, and the cause of cracking (stress
corrosion), we have concluded that the inspections are necessary to
address the unsafe condition.
We have not changed the final rule AD action based on this comment.

Request To Withdraw Proposed AD

Mike Ciholas and eight others stated that the unsafe condition
addressed in the proposed AD be handled as part of routine inspections.
The commenters stated that there has never been any incident, accident,
injury, or fatality attributed to this issue despite the millions of
flight hours the MU-2B airplane has accumulated, including those hours
that some airplanes have flown with a crack present. There has never
been any damage to any airplane from this issue. None of the subject
parts have failed to perform in service, cracked or otherwise.
Mark James of Intercontinental Jet Service Corp. and two others
stated that there have been no failures in the airframes.
The commenters requested that the proposed AD be withdrawn.
We do not agree with the commenters. While there have been no
failures to date, the stress corrosion cracking exhibited is in primary
load structure. Upon crack initiation, the frames will have diminished
load carrying capabilities, which will propagate over time, potentially
leading to failure. Although previous inspection requirements specify
visual inspection of all frames, no instruction was provided for
accessing the difficult to reach areas where the subject cracks have
been found. In addition, we are issuing this AD to address the unsafe
condition and prevent such failures of this airplane.
We have not changed the final rule AD action based on this comment.

Request To Delay Issuing the Final Rule AD Action

David Klain and six others stated that they wanted the FAA to hold
the proposed AD in abeyance and request additional data from the
manufacturer, service centers, and the owner/operator community. At the
very least, all inspections completed to date should be considered and
an evaluation made as to what specifically is causing these cracks,
other than the simple fact these are MU-2 long body airplanes.
Additional data can be collected from ongoing inspections conducted in
accordance with the maintenance manual as well. Once that data is
collected, an informed decision based on facts instead of speculation
can be made.
The commenters requested that we delay issuing the final rule AD
action.
We do not agree with the commenters. We have considered the request
to delay issuing the final rule AD action and have determined that
sufficient evidence and data exist, specifically information recently
from MHI on the inspections of 18 of the 119 airplanes in the U.S.
fleet that indicate that 8 of them were cracked. Out of these eight,
four have been removed from service. Based on the data presented in the
NPRM and this more detailed information provided by MHI, the location
of cracks, and the cause of cracking (stress corrosion), we have
concluded that the inspections are necessary to address the unsafe
condition. Further delay of the final rule AD action would allow a
known unsafe condition to exist without AD action to address it.
We have not changed the final rule AD action based on this comment.

Request To Verify Cost of Compliance

David Klain and three others stated that the Mitsubishi Service
Centers have indicated that the time and cost estimates detailed in the
proposed AD are not accurate and do not reflect the actual higher costs
and time necessary to complete the inspection based on the inspections
completed to date.
The commenters requested a change to the Cost of Compliance
section.
We do not agree with the commenters. The cost provided by the
original equipment manufacturer (OEM) is a rough order of magnitude
estimate based on available information and standardized cost
evaluation methods.
We have not changed the final rule AD action based on this comment.

Request To Withdraw Proposed AD

David Klain and three others stated that the proposed AD is based
on non-representative airframes. The proposed AD was derived from a
service bulletin that originated from inspections of a limited, non-
representative sample of airframes that have been removed from service
and represent the worst possible scenario with regards to airframe
stress (freighters).
The commenters stated that since Special Airworthiness Information
Bulletin (SAIB) No. CE-03-26, dated February 28, 2003 (which can be
found at http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgSAIB.nsf/
(LookupSAIBs)/CE-03-26?OpenDocument), three additional airplanes with a
total airframe time and operational use (non-freighter) that is more
representative of the fleet have been inspected at several service
centers and not a single plane exhibited the cracks in question. The
commenters stated, based on these findings, there is a situation where
a very small sample size may give some indication there is a
correlation between total time and/or airplane utilization (freighters
with heavy takeoff/landing weights and many cycles) and the cracks in
question, but further empirical data is likely necessary to draw any
firm conclusions.
The commenters also stated that the costly inspection goes against
the FAA's mandate to encourage and promote aviation by potentially
mandating a costly inspection that would result in the decommissioning
of perfectly safe and flyable airplanes for no reason other than the
high cost of an inspection mandated by the FAA without any engineering
data to support such inspections.
We infer that the commenters believe that the final rule AD action
is unnecessary and want the proposed AD withdrawn.
We do not agree with the commenters. More detailed information from
MHI on the inspections of 18 of the 119 airplanes in the U.S. fleet
indicate that 8 of them were cracked of which 5 were used as
freighters. Out of these eight, four have been removed from service.
Based on the data presented in the NPRM and this more detailed
information provided by MHI, the location of cracks, and the cause of
cracking (stress corrosion), we have concluded that the inspections are
necessary to address the unsafe condition.
The OEM has also provided the time and cost information presented
in this final rule AD action.
We have not changed the final rule AD action based on this comment.

Request To Include a Less Expensive Repair Option

Richard Wheldon and one other commenter stated that there is a less
expensive repair available to the owners/operators of the affected
airplanes.
The commenters stated that the repairs specified in the Mitsubishi
Heavy Industries, Ltd. (MHI Ltd.) MU-2 Service Bulletins No. 231, dated
July 2, 1997, and No. 073/53-002B, dated April 27, 1999, involve
doublers and are much less intrusive and less labor intensive. The
repairs in MHI Ltd. MU-2 Service Bulletins No. 242, dated July 10,
2013, and No. 104/53-003, dated July 22, 2013, involve large splices
and/or frame segment replacements, which are very costly. It is not
explained why the less expensive methods were not proposed. In
discussions with experienced sheet metal mechanics and structures
engineers, they expressed that other repair schemes are possible that
adequately address any safety concerns and are much less costly.
Many of the cracks found at the lower sections of the bottom frame
segments might be repairable using doublers rather than replacing the
entire lower frame segments, which is the only solution allowed in the
proposed AD. Obviously, the replacement of an entire lower frame
segment is a huge, potentially unnecessary undertaking involving
considerable assembly and disassembly. Any conventional solution short
of frame segment replacement should be investigated.
The commenters also stated that an operator is not allowed to
repair the side frame segments per MHI Ltd. MU-2 Service Bulletins No.
231, dated July 2, 1997, and No. 073/53-002B, dated April 27, 1999, and
still be in compliance with the proposed AD. The only solution to a
side frame crack allowed per MHI Ltd. MU-2 Service Bulletins No. 242,
dated July 10, 2013, and No. 104/53-003, dated July 22, 2013, is the
much more expensive replacing of the side frame segment.
The commenters requested compliance based on MHI Ltd. MU-2 Service
Bulletins No. 231, dated July 2, 1997, and No. 073/53-002B, dated April
27, 1999, at a minimum, be permitted in the final rule AD action.
We do not agree with the commenters. MHI Ltd. MU-2 Service
Bulletins No. 231, dated July 2, 1997, and No. 073/53-002B, dated April
27, 1999, require inspecting for cracks that are specifically located
around rivet holes. The service bulletins specified in this AD require
inspecting for cracks in a different area, specifically throughout the
frame flanges.
If lower cost repair methods exist that meet the intent of the
proposed AD, you may propose an alternative method of compliance or a
change in the compliance time that provides an acceptable level of
safety using the procedures found in 14 CFR 39.19.

We have not changed the final rule AD action based on this comment.

Request To Consider Other Causes of the Cracks

David Klain and one other commenter stated that the proposed AD
does not accurately consider what the causal factors are that may have
caused the cracks in question (airframe age, cycles, total time,
utilization as freighters, etc.) due to lack of adequate representative
data.
The commenters requested the FAA to further investigate the cause
of the cracks.
We do not agree with the commenters. We have evaluated the data
provided and have determined that the cause of cracking is stress
corrosion. We have determined that is sufficient evidence and data of
an unsafe condition and we should proceed with issuing the final rule
AD action.
We have not changed the final rule AD action based on this comment.

Request To Utilize Special Airworthiness Information Bulletin (SAIB)
No. CE-03-26, Dated February 28, 2003

Mark James of Intercontinental Jet Service Corp. stated that the
inspections introduced and recommended in SAIB No. CE-03-26, dated
February 28, 2003, which can be found at http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgSAIB.nsf/(LookupSAIBs)/CE-03-
26?OpenDocument, should be sufficient to cover inspections required
from this AD because the stresses are the same.
The commenter stated that the inspection criteria in the proposed
AD require inspection of a different location of these same frames and
the fact is that the frame materials and stresses are the same.
We infer that the commenter believes the inspections introduced and
recommended in SAIB No. CE-03-26, dated February 28, 2003, are
sufficient in addressing the unsafe condition identified in this AD
wants the proposed AD withdrawn.
We do not agree with the commenter. It is stated in the proposed AD
that stress corrosion cracking may be located throughout the area of
the frame flanges. The inspections recommended in SAIB No. CE-03-26 are
more limited and only inspect for stress corrosion cracking at screw
holes in the flange.
We have not changed the final rule AD action based on this comment.

Request To Modify the Applicability Section

An anonymous commenter stated that the statistical analysis and
evaluation performed in support of the proposed AD is flawed. The
commenter also stated that given the inconsistent data from a sample
size that is not representative of the fleet, there appears to be no
scientific or engineering basis for issuing the final rule AD action
and mandating it for the entire fleet
The commenter stated that Mark James of Intercontinental Jet
Service Corp. also stated that the conclusions made by the FAA were not
based on an adequate representation of the fleet and that thus far the
only cracks found have been on two higher time airframes and not on the
many airplanes that have less than one-third of the flight time and
cycles
The commenter requested the applicability of the final rule AD
action be changed to apply only to high time, high-cycle airplanes.
We do not agree with the commenters. More detailed information from
MHI on the inspections of 18 of the 119 airplanes in the U.S. fleet
indicate that 8 of them were cracked. Out of the 18 airplanes, 5 of
them are used as freighters and all 5 of these were among the 8 found
cracked. Four of the eight airplanes found cracked have been removed
from service. Based on the data presented in the NPRM and this more
detailed information provided by MHI, the location of cracks, and the
cause of cracking (stress corrosion), we have concluded that the
inspections are necessary to address the unsafe condition.
We have not changed the final rule AD action based on this comment.

Conclusion

We reviewed the relevant data, considered the comments received,
and determined that air safety and the public interest require adopting
the AD as proposed except for minor editorial changes. We have
determined that these minor changes:
Are consistent with the intent that was proposed in the
NPRM (79 FR 10710, February 26, 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 10710, February 26, 2014).

Relevant Service Information

Mitsubishi Heavy Industries, Ltd. has issued Service Bulletin No.
242, dated July 10, 2013, and Service Bulletin No. 104/53-003, dated
July 22, 2013. The actions described in this service information are
intended to correct the unsafe condition identified in the MCAI. The
service bulletin describes procedures to inspect and repair/replace the
side and lower frame at stations 4610 and 5605. You can find this
service information on the Internet at http://www.regulations.gov by
searching for and locating Docket No. FAA-2014-0108.

Costs of Compliance

We estimate that this AD will affect 119 products of U.S. registry.
We also estimate that it will take about 100 work-hours per product to
comply with the basic requirements of this AD. The average labor rate
is $85 per work-hour.
Based on these figures, we estimate the cost of this AD on U.S.
operators to be $1,011,500, or $8,500 per product.
In addition, we estimate that any necessary follow-on actions will
take up to 428 work-hours and require parts costing up to $14,400, for
a cost up to $50,780 per product. We have no way of determining the
number of products that may need such repair based on the results of
the inspection. The extent of damage will vary on each airplane.

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

We 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 this AD:
(1) Is not a ``significant regulatory action'' under Executive
Order 12866,
(2) Is not a ``significant rule'' under the 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.

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-
0108; 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 the NPRM, the regulatory evaluation, any comments received,
and other information. The street address for the Docket Office
(telephone (800) 647-5527) is in the ADDRESSES section. Comments will
be available in the AD docket shortly after receipt.

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 AD: