E6-6054. Airworthiness Directives; Mitsubishi Heavy Industries MU-2B Series Airplanes

AGENCY:

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

ACTION:

Supplemental notice of proposed rulemaking (NPRM); Reopening of the comment period.

SUMMARY:

The FAA proposes to revise an earlier proposed airworthiness directive (AD) that applies to all Mitsubishi Heavy Industries MU-2B series airplanes. The earlier NPRM would have required you to do the following: Remove and visually inspect the wing attach barrel nuts, bolts, and retainers for cracks, corrosion, and fractures; replace any cracked, corroded, or fractured parts; inspect reusable wing attach barrel nuts and bolts for deformation and irregularities in the threads; replace any deformed or irregular parts; and install new or reusable parts and torque to the correct value. The earlier NPRM resulted from a recent safety evaluation that used a data-driven approach to evaluate the design, operation, and maintenance of the MU-2B series airplanes in order to determine their safety and define what steps, if any, are necessary for their safe operation. This proposed AD would retain the actions from the earlier NPRM, add airplanes to the applicability, revise the serial numbers of the affected airplanes, and update the manufacturer's contact information. This proposed AD results from the manufacturer revising the service information to include two additional airplane models. Since these actions impose an additional burden over that proposed in the NPRM, we are reopening the comment period to allow the public the chance to comment on these additional actions.

DATES:

We must receive comments on this proposed AD by May 25, 2006.

ADDRESSES:

Use one of the following addresses to comment on this proposed AD:

• DOT Docket Web site: Go to http://dms.dot.gov and follow the instructions for sending your comments electronically.
• Government-wide rulemaking Web site: Go to http://www.regulations.gov and follow the instructions for sending your comments electronically.
• Mail: Docket Management Facility; U.S. Department of Transportation, 400 Seventh Street, SW., Nassif Building, Room PL-401, Washington, DC 20590-0001.
• Fax: [phone].
• Hand Delivery: Room PL-401 on the plaza level of the Nassif Building, 400 Seventh Street, SW., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

For service information identified in this proposed AD, contact Mitsubishi Heavy Industries America, Inc., 4951 Airport Parkway, Suite 800, Addison, Texas 95001; telephone: [phone]; fax: [phone], or Turbine Aircraft Services, Inc., 4550 Jimmy Doolittle Drive, Addison, Texas 75001; telephone: [phone]; facsimile: [phone].

FOR FURTHER INFORMATION CONTACT:

Andrew McAnaul, Aerospace Engineer, ASW-150 (c/o MIDO-43), 10100 Reunion Place, Suite 650, San Antonio, Texas 78216; telephone: [phone]; facsimile: [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to send any written relevant data, views, or arguments regarding this proposed airworthiness directive (AD). Send your comments to an address listed under the ADDRESSES section. Include the docket number, “FAA-2006-23578; Directorate Identifier 2006-CE-01-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the proposed AD. We will consider all comments received by the closing date and may amend the proposed AD in light of those comments.

We will post all comments we receive, without change, to http://dms.dot.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact we receive concerning this proposed AD.

Discussion

Recent accidents and the service history of the Mitsubishi Heavy Industries (MHI) MU-2B series airplanes prompted the Federal Aviation Administration (FAA) to conduct an MU-2B Safety Evaluation. This evaluation used a data-driven approach to evaluate the design, operation, and maintenance of MU-2B series airplanes in order to determine their safety and define what steps, if any, are necessary for their safe operation.

The safety evaluation provided an in-depth review and analysis of MU-2B incidents, accidents, safety data, pilot training requirements, engine reliability, and commercial operations. In conducting this evaluation, the team employed new analysis tools that provided a much more detailed root cause analysis of the MU-2B problems than was previously possible.

Part of that evaluation was to identify unsafe conditions that exist or could develop on the affected type design airplanes. One of these conditions is the discovery of the right wing upper forward and lower forward barrel nuts found cracked during routine maintenance on one of the affected airplanes. The manufacturer conducted additional investigations of the wing attach barrel nuts on other affected airplanes. The result of this investigation revealed no other cracked barrel nuts. However, it was discovered that several airplanes had over-torqued barrel nuts, which could result in cracking.

This condition, if not detected and corrected, could result in failure of the wing barrel nuts and/or associated wing attachment hardware. This failure could lead to in-flight separation of the outer wing from the center wing section and result in loss of controlled flight.

We issued a proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an AD that would apply to all MHI MU-2B series airplanes. This proposal was published in the Federal Register as a notice of proposed rulemaking (NPRM) on January 25, 2006 (71 FR 4072). The NPRM proposed to require you to do the following:

• Remove and visually inspect the wing attach barrel nuts, bolts, and retainers for cracks, corrosion, and fractures;
• Replace any cracked, corroded, or fractured wing attach barrel nuts, bolts, and retainers with new parts;
• Inspect reusable barrel nuts and bolts for deformation and irregularities in the threads;
• Replace any deformed or irregular wing attach barrel nuts or bolts with new parts; and
• Install new or reusable parts and torque to the correct value.

Comments

The FAA encouraged interested persons to participate in developing this amendment. The following presents the comments received on the proposal and FAA's response to each comment:

Comment Issue No. 1: Incorporate Revised Service Bulletin

The manufacturer revised the MU-2 Service Bulletin referenced as FAA T.C.: No. 103/57-004, dated August 2, 2004, to add two airplane models to the effectivity. The change in the model effectivity accurately reflects the airplanes for that service bulletin.

The manufacturer requests the revised service bulletin, MU-2 Service Bulletin referenced as FAA T.C.: No. 103/57-004A, dated March 10, 2006, be incorporated into the NPRM.

We agree with the commenter and will incorporate the revised service bulletin into the supplemental NPRM.

Comment Issue No. 2: Revise the Manufacturer Contact Information

The manufacturer requests that we revise the manufacturer contact information from Mitsubishi Heavy Industries in Nagoya, Japan, to Mitsubishi Heavy Industries America, Inc. in Addison Texas.

We agree with the commenter and will incorporate the change into the supplemental NPRM.

Comment Issue No. 3: Revise the Serial Numbers of the Affected Airplanes

The manufacturer requests that we revise the serial numbers of the affected airplanes based on additional information submitted for clarification.

We agree with the commenter and will incorporate the change into the supplemental NPRM.

Comment Issue No. 4

The manufacturer requests that we revise the proposed requirement in the NPRM for “replacing any bolts or barrel nuts with deformation or irregularities in the threads” to include a “or that do not meet the minimum breakaway torque check.”

We agree with the commenter and will incorporate the change into the supplemental NPRM.

Events That Caused FAA To Issue a Supplemental NPRM

The manufacturer revised the service information to include two additional airplane models.

Relevant Service Information

We have reviewed Mitsubishi Heavy Industries, Ltd. MU-2 Service Bulletin referenced as JCAB T.C.: No. 241, dated July 14, 2004, and MU-2 Service Bulletin referenced as FAA T.C.: No. 103/57-004A, dated March 10, 2006.

These service bulletins describe procedures for:

• Removing and inspecting the wing attach barrel nuts and retainer for cracks, corrosion, and fractures;
• Replacing any wing attach barrel nuts and retainer with cracks, corrosion, or fractures;
• Inspecting reusable wing attach barrel nuts and bolts for deformation or irregularities in the threads;
• Checking the minimum breakaway torque of the wing attach barrel nuts;
• Replacing any bolts or wing attach barrel nuts with deformation or irregularities in the threads or that do not meet the minimum breakaway torque check; and
• Reinstalling the wing attach barrel nuts and hardware to the correct torque value.

Foreign Airworthiness Authority Information

The MU-2B series airplane was initially certificated in 1965 and again in 1976 under two separate type certificates (TC) that consist of basically the same type design. Japan is the State of Design for TC No. A2PC, and the United States is the State of Design for TC No. A10SW. The affected models are as follows (where models are duplicated, specific serial numbers are specified in the individual TCs):

Type certificate	Affected models
A10SW	MU-2B-25, MU-2B-26, MU-2B-26A, MU-2B-35, MU-2B-36, MU-2B-36A, MU-2B-40, and MU-2B-60.
A2PC	MU-2B, MU-2B-10, MU-2B-15, MU-2B-20, MU-2B-25, MU-2B-26, MU-2B-30, MU-2B-35, and MU-2B-36.

The Japan Civil Airworthiness Board (JCAB), which is the airworthiness authority for Japan, approved Mitsubishi Heavy Industries, Ltd. MU-2 Service Bulletin referenced as JCAB T.C.: No. 241, dated July 14, 2004, and MU-2 Service Bulletin referenced FAA T.C.: No. 103/57-004A, dated March 10, 2006, to ensure the continued airworthiness of these airplanes in Japan.

FAA's Determination and Requirements of the Proposed AD

After examining the circumstances and reviewing all available information related to the incidents described above, we have determined that:

• The unsafe condition referenced in this document exists or could develop on other Mitsubishi MU-2B series airplanes of the same type design that are on the U.S. registry;
• We should change the NPRM to incorporate the concerns addressed by the commenters and incorporate the revised service information; and
• We should take AD action to correct this unsafe condition.

The Supplemental NPRM

Adding airplanes to the applicability section of the NPRM goes beyond the scope of what was originally proposed in the NPRM. Therefore, we are reopening the comment period and allowing the public the chance to comment on these additional actions.

This proposed AD would require you to do the following:

• Remove and visually inspect the wing attach barrel nuts, bolts, and retainers for cracks, corrosion, and fractures;
• Replace any cracked, corroded, or fractured wing attach barrel nuts, bolts, and retainers with new parts;
• Inspect reusable wing attach barrel nuts and bolts for deformation and irregularities in the threads;
• Check the minimum breakaway torque of the wing attach barrel nuts;
• Replace any deformed or irregular wing attach barrel nuts or bolts with new parts; and
• Install new or reusable parts and torque to the correct value.

The FAA is committed to updating the aviation community of expected costs associated with the MU-2B series airplane safety evaluation conducted in 2005. As a result of that commitment, the accumulating expected costs of all ADs related to the MU-2B series airplane safety evaluation may be found in the Final Report section at the following Web site: http://www.faa.gov/​aircraft/​air_​cert/​design_​approvals/​small_​airplanes/​cos/​mu2_​foia_​reading_​library/​.

Costs of Compliance

We estimate that this proposed AD affects 399 airplanes in the U.S. registry.

We estimate the following costs to do the proposed inspection:

Labor cost	Parts cost	Total cost per airplane	Total cost on U.S. operators
12 workhours × $80 per hour = $960	N/A	$960	$960 × 399 = $383,040

We estimate the following costs to do any necessary replacements that would be required based on the results of the proposed inspection. We have no way of determining the number of airplanes that may need this replacement:

Labor cost	Parts cost	Total cost per airplane to replace all 8 wing attach barrel nuts
No additional labor cost. Any necessary replacements will be done at the time of inspection	$60 for each barrel nut. There are 8 barrel nuts on each airplane. Possible total cost of: $60 × 8 = $480	$480

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 have determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD would 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 the proposed regulation:

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); and

3. 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.

We prepared a regulatory evaluation of the estimated costs to comply with this proposed AD and placed it in the AD docket.

Examining the AD Docket

You may examine the AD docket that contains the proposed AD, the regulatory evaluation, any comments received, and other information on the Internet at http://dms.dot.gov;​; or in person at the Docket Management Facility between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Office (telephone [phone]) is located at the street address stated 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
• Safety

The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend 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.

§ 39.13

[Amended]

2. The Federal Aviation Administration (FAA) amends § 39.13 by adding the following new airworthiness directive (AD):

Mitsubishi Heavy Industries, Ltd.: Docket No. FAA-2006-23578; Directorate Identifier 2006-CE-01-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by May 25, 2006.

Affected ADs

(b) None.

Applicability

(c) This AD affects the following Mitsubishi Heavy Industries, Ltd. airplane models and serial numbers that are certificated in any category:

Model	Serial numbers
MU-2B-10	101 through 120 (Except 102, 114, 115, and 118).
MU-2B-15	114, 115, and 118.
MU-2B-20	102, and 121 through 238.
MU-2B-25	239 through 318 (Except 313), and 313SA.
MU-2B-26	319 through 347 (Except 321), and 349SA.
MU-2B-26A	321SA, 348SA, and 350SA through 394SA (Except 365SA).
MU-2B-30	502 through 547.
MU-2B-35	548 through 654 (Except 652), and 652SA.
MU-2B-36	501, and 655 through 696 (Except 661).
MU-2B-36A	661SA, and 697SA through 730SA (Except 700SA).
MU-2B-40	365SA.
MU-2B-60	700SA.

Unsafe Condition

(d) This AD results from a recent safety evaluation that used a data-driven approach to evaluate the design, operation, and maintenance of the MU-2B series airplanes in order to determine their safety and define what steps, if any, are necessary for their safe operation. Part of that evaluation was to identify unsafe conditions that exist or could develop on the affected type design airplanes. The actions specified in this AD are intended to detect and correct cracks, corrosion, fractures, and incorrect torque values in the wing attach barrel nuts, which could result in failure of the wing attach barrel nuts and/or associated wing attachment hardware. This failure could lead to in-flight separation of the outer wing from the center wing section and result in loss of controlled flight.

Compliance

(e) To address this problem, you must do the following, unless already done:

Actions	Compliance	Procedures
(1) Remove each wing attach barrel nut, bolt, and retainer and do a detailed visual inspection for cracks, corrosion, and fractures	Within the next 200 hours time-in-service (TIS) or 12 months after the effective date of this AD, whichever occurs first, unless already done	Follow Mitsubishi Heavy Industries, Ltd. MU-2 Service Bulletins referenced as JCAB T.C.: No. 241, dated July 14, 2004, and FAA T.C.: No. 103/57-004A, dated March 10, 2006, as applicable.
(2) If any signs of cracks, corrosion, or fractures are found on any wing attach barrel nut during the inspection required in paragraph (e)(1) of this AD, replace that wing attach barrel nut, bolt, and retainer with new parts and install to the correct torque value	Before further flight after the inspection required in paragraph (e)(1) of this AD, unless already done	Follow Mitsubishi Heavy Industries, Ltd. MU-2 Service Bulletins referenced as JCAB T.C.: No. 241, dated July 14, 2004, and FAA T.C.: No. 103/57-004A, dated March 10, 2006, as applicable, and the appropriate maintenance manual.
(3) If no signs of cracks, corrosion, or fractures are found during the inspection required in paragraph (e)(1) of this AD, you may reuse the wing attach barrel nuts and bolts if they have been inspected and are free of deformation and irregularities in the threads and meet the minimum breakaway torque requirement. Reinstall inspected parts to the correct torque value. If the wing attach barrel nuts and bolts are not free of deformation and irregularities in the threads or do not meet the minimum breakaway torque requirement, install new parts to the correct torque value	Before further flight after the inspection required in paragraph (e)(1) of this AD, unless already done	Follow Mitsubishi Heavy Industries, Ltd. MU-2 Service Bulletins referenced as JCAB T.C.: No. 241, dated July 14, 2004, and FAA T.C.: No. 103/57-004A, dated March 10, 2006, as applicable, and the appropriate maintenance manual.

Alternative Methods of Compliance (AMOCs)

(f) The Manager, Fort Worth Airplane Certification Office, FAA, ATTN: Andrew McAnaul, Aerospace Engineer, ASW-150 (c/o MIDO-43), 10100 Reunion Place, Suite 650, San Antonio, Texas 78216; telephone: [phone]; facsimile: [phone], has the authority to approve alternative methods of compliance for this AD, if requested using the procedures found in 14 CFR 39.19.

Related Information

(g) Mitsubishi Heavy Industries, Ltd. MU-2 Service Bulletins JCAB T.C.: No. 241, dated July 14, 2004, and FAA T.C.: No. 103/57-004A, dated March 10, 2006, pertain to the subject of this AD. To get copies of the documents referenced in this AD, contact Mitsubishi Heavy Industries America, Inc., 4951 Airport Parkway, Suite 800, Addison, Texas 95001; telephone: [phone]; fax: [phone], or Turbine Aircraft Services, Inc., 4550 Jimmy Doolittle Drive, Addison, Texas 75001; telephone: [phone]; facsimile: [phone]. To view the AD docket, go to the Docket Management Facility; U.S. Department of Transportation, 400 Seventh Street, SW., Nassif Building, Room PL-401, Washington, DC, or on the Internet at http://dms.dot.gov. The docket number is Docket No. FAA-2006-23578; Directorate Identifier 2006-CE-01-AD.

Issued in Kansas City, Missouri, on April 18, 2006.

William J. Timberlake,

Acting Manager, Small Airplane Directorate, Aircraft Certification Service.