[Federal Register Volume 84, Number 40 (Thursday, February 28, 2019)]
[Proposed Rules]
[Page 6708]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2019-03397]



[[Page 6708]]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2016-9139; Directorate Identifier 2016-CE-023-AD]
RIN 2120-AA64


Airworthiness Directives; Mitsubishi Heavy Industries, Ltd. 
Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Proposed rule; withdrawal.

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SUMMARY: The FAA is withdrawing a notice of proposed rulemaking (NPRM) 
that proposed to adopt a new airworthiness directive (AD) that would 
have applied to certain Mitsubishi Heavy Industries, Ltd. Models MU-2B-
10, MU-2B-15, MU-2B-20, MU-2B-25, MU-2B-26, MU-2B-26A, MU-2B-30, MU-2B-
35, MU-2B-36, MU-2B-36A, MU-2B-40, and MU-2B-60 airplanes. The NPRM 
resulted from mandatory continuing airworthiness information (MCAI) 
originated by an aviation authority of another country to identify and 
correct an unsafe condition on an aviation product and would have 
required repetitively inspecting the wing spacer plates for cracks 
until they were replaced with an improved design wing spacer plates. 
Since issuance of the NPRM, we determined that damage is contained to 
the wing spacer plate with no evidence that primary structure is 
affected. Accordingly, the NPRM is withdrawn.

DATES: As of February 28, 2019, the proposed rule, which published in 
the Federal Register on September 16, 2016 (81 FR 63725), is withdrawn.

FOR FURTHER INFORMATION CONTACT: Bang Nguyen, Aerospace Engineer, FAA, 
Fort Worth ACO Branch, 10101 Hillwood Pkwy., Fort Worth, Texas 76177; 
telephone: (817) 222-4973; fax: (817) 222-5785; email: 
[email protected].

SUPPLEMENTARY INFORMATION:

Discussion

    We issued an NPRM that proposed to amend 14 CFR part 39 to add an 
AD that would apply to the specified products. The NPRM was published 
in the Federal Register on September 16, 2016 (81 FR 63725). The NPRM 
was prompted by the Japan Civil Aviation Bureau (JCAB), which is the 
aviation authority for Japan, AD No. TCD-8783-2016, dated June 28, 2016 
(referred to after this as ``the MCAI''), to correct an unsafe 
condition for certain Mitsubishi Heavy Industries (MHI) Models MU-2B-
20, MU-2B-25, MU-2B-26, MU-2B-30, MU-2B-35, and MU-2B-36 airplanes.
    As part of the MHI MU-2B aging aircraft program, one-piece and 
three-piece main wings were subjected to detailed teardown inspections, 
and cracks were found in the wing spacer plates attached to the forward 
lower spar area at wing station 580. It was determined that the cracks 
resulted from fatigue caused by flight loads.
    Japan is the State of Design for the MHI airplane models that the 
MCAI AD applies to: Models MU-2B-20, MU-2B-25, and MU-2B-26 with serial 
numbers (S/Ns) 102 and 121 through 347, except 313 and 321; and Models 
MU-2B-30, MU-2B-35, and MU-2B-36 with S/Ns 502 through 696, except 652 
and 661. The United States is the State of Design for MHI Models MU-2B-
10, MU-2B-15, MU-2B-25, MU-2B-26, MU-2B-26A, and MU-2B-40 with S/Ns 
313SA, 321SA, and 348SA through 459SA; and Models MU-2B-36A and MU-2B-
60 with S/Ns 661SA and 697SA through 1569SA airplanes. Japan is the 
State of Design for Models MU-2B-10 and MU-2B-15 airplanes, but has 
recently removed these models from the MHI Japanese type certificate. 
These models remain on the FAA type certificate; however, none of these 
airplanes are currently on the U.S. registry.
    The NPRM proposed to require repetitively inspecting the wing 
spacer plates for cracks until they were replaced with an improved 
design wing spacer plates. The proposed actions were intended to detect 
and correct cracks in the wing spacer plates, which could result in 
reduced structural integrity of the wings and loss of control.

Actions Since the NPRM Was Issued

    Since issuance of the NPRM, we have received data from operators 
who completed the inspections specified in MHI MU-2 Service Bulletin 
No. 245, dated April 21, 2016, and MU-2 Service Bulletin No. 107/57-
005, dated May 3, 2016. During the inspections, no cracking in a 
primary wing structure has been detected. We have determined that 
damage is contained to the wing spacer plates without affecting the 
primary structure. Our analysis of fleet data also demonstrates that 
the wing spar and the wing spar cap maintains conformity with the 
structural requirements of the type certificate after complete fracture 
of the wing spacer plate. Neither the JCAB nor the manufacturer has 
provided the FAA with sufficient data that an unsafe condition exists. 
Therefore, we have determined that AD action is not appropriate, and 
the NPRM should be withdrawn.
    After we received numerous comments on the NPRM stating there is no 
unsafe condition, we requested additional information from JCAB to 
demonstrate that the cracks found in the spacers reduce the structural 
integrity of primary structure. JCAB replied that it took AD action 
because it is uncertain how the fatigue strength will be affected over 
the life of the airplane. In addition to the lack of conclusive data 
that there is an unsafe condition, we considered that removing the wing 
in order to perform the proposed corrective action may be more 
detrimental to the aircraft than the cracks themselves.
    Withdrawal of this NPRM constitutes only such action and does not 
preclude the agency from issuing future rulemaking on this issue, nor 
does it commit the agency to any course of action in the future.

Regulatory Findings

    Since this action only withdraws an NPRM, it is neither a proposed 
nor a final rule and therefore, not covered under Executive Order 
12866, the Regulatory Flexibility Act, or DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979).

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

The Withdrawal

0
Accordingly, the notice of proposed rulemaking, Docket No. FAA-2016-
9139, which published in the Federal Register on September 16, 2016 (81 
FR 63725), is withdrawn.

    Issued in Kansas City, Missouri, on February 19, 2019.
Melvin J. Johnson,
Aircraft Certification Service, Deputy Director, Policy and Innovation 
Division, AIR-601.
[FR Doc. 2019-03397 Filed 2-27-19; 8:45 am]
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