AD 94-11-04

This amendment adopts a new airworthiness directive (AD) that applies to certain Mitsubishi Heavy Industries MU-2B series airplanes. This action requires adjusting the engine underspeed governor minimum stop (ground idle) and the airframe condition control linkage, modifying the tachometer indicator markings, fabricating and installing a placard that specifies a minimum idle speed, and incorporating Airplane Flight Manual (AFM) revisions. An accident of one of the affected airplanes where the propeller hub assembly failed and the propeller separated from the airplane prompted this action. Accident investigation analysis indicates a reduction in fatigue strength of the propeller hub because of high vibration frequencies during ground idle speed. The actions specified by this AD are intended to prevent propeller hub arm assembly failure because of high vibration frequencies during ground idle speed and possible separation of the propeller from the airplane, which could result in loss of control of the airplane.

Final rule; request for comments.

94-11-04 MITSUBISHI HEAVY INDUSTRIES, LTD.: Amendment 39-8920; Docket No. 94-CE-09-AD. \n\tApplicability: The following model and serial number airplanes, certificated in any category: \n\n\nModel\nSerial Numbers \nMU-2B-26A\nAll serial numbers\nMU-2B-36A\nAll serial numbers\nMU-2B-40\nAll serial numbers\nMU-2B-60\nAll serial numbers\nMU-2B-36\nAll serial numbers modified by Supplemental Type Certificate SA2413SW \n\t\t\t\t\n\tCompliance: Required within the next 25 hours time-in-service after the effective date of this AD, unless already accomplished. \n\n\tTo prevent propeller hub arm assembly failure because of high vibration frequencies during ground idle speed and possible separation of the propeller from the airplane, which could result in loss of control of the airplane, accomplish the following: \n\n\t(a)\tAdjust the underspeed governor minimum stop (ground idle) to a range of 76.5 percent to 78.5 percent in accordance with the Allied Signal Garrett Maintenance Manual (Report No.72-00-95 for TPE331-10-501M or Report No. 72-00-27 for TPE331-501M or -511M), chapter 72-00-00, General-Adjustment /Test; and chapter 76-10-01, Control Linkage Assembly, Maintenance Practices. \n\n\tNOTE 1: One clockwise turn of the adjusting screw will increase the ground idle engine speed approximately 5 percent. \n\n\t(b)\tModify the airframe condition control linkage by adjusting Rod 1 and Levers 2 and 7 as specified in Figure 1 of this AD in accordance with Chapter 6, Section 9.2, of the applicable Mitsubishi MU-2 maintenance manual. \n\n\t(c)\tModify the tachometer indicator marking by accomplishing the following: \n\n\t\t(1)\tApply red lacquer (Federal Standard 595a, number 11105 or equivalent) to the tachometer indicator glass so that the red operating arc extends to 76.5 percent. \n\n\tNOTE 2: The red operating arc range will now be from 50 percent to 76.5 percent. \n\n\t\t(2)\tUsing white lacquer (MIL-L-7178, color number 511 or equivalent), apply a 1/16-inch wide by 1/4-inch long slip stripe over the tachometer glass and indicator case at the 11:30 o'clock position as specified in Figure 2 of this AD. \n\n\t(d)\tFabricate a placard with the following words utilizing letters at least .10-inch in height: "Minimum engine idle speed - 76.5 percent". Install this placard on the instrument panel in close proximity to the tachometer within the pilot's full view. \n\n\t(e)\tModifying the tachometer dial through an FAA-approved instrument repair shop to extend the red operating arc to 76.5 percent is equivalent to those actions required by paragraph (c)(1), (c)(2), and (d) of this AD, and may be accomplished in lieu of those actions. \n\n\t(f)\tIncorporate the following revision into the applicable Airplane Flight Manual: \n\n\nEffective Model\nPages\nDate and Revision Level\nMU-2B-26A\n1, 2, REVISION\t\nLOG 2, 1-5, 5-10,\n5-13, and 5-23\t\nFAA APPROVED 1-12-77 \nREISSUED 03-25-86 \nREVISION 4\nMU-2B-36A\n1, 2, REVISION \t\nLOG 2, 1-5, 2-10,\t\n5-10, 5-13, and 5-23\nFAA APPROVED 01-12-77 \nREISSUED 02-28-86 \nREVISION 6 \nMU-2B-40\n1, 2, REVISION \t\nLOG 2, 1-5, 2-10,\t\n5-10, 5-13, 5-14, \t\nand 5-24 \nFAA APPROVED 3-2-78 \nREISSUED 03-25-86 \nREVISION 4 \nMU-2B-60\n1, 2, REVISION \t\nLOG 2, 1-5, 2-9, \t\n5-10, 5-13, 5-14, \t\nand 5-24 \nFAA APPROVED 3-2-78 \nREISSUED 09-24-85 \nREVISION 5 \nMU-2B-36\nModified by \nSTC SA2413SW\n1 through 31\nFAA APPROVED 2-1-78 \nREISSUED 12-18-92 \nREVISION 1 \n\n\t(g)\tSpecial flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished. \n\n\t(h)\tAn alternative method of compliance other than that referenced in paragraph (e) of this AD or adjustment of the compliance time that provides an equivalent level of safety may be approved by the Manager, Wichita Aircraft Certification Office (ACO), 1801 Airport Road, Room 100, Mid-Continent Airport, Wichita, Kansas 67209.The request shall be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, Wichita ACO. \n\n\tNOTE 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Wichita ACO. \n\n\t(i)\tThe incorporation required by this AD shall be done in accordance with the following airplane flight manual revisions (as applicable): \n\n\nEffective Model\nPages\nDate and Revision Level \nMU-2B-26A\n1, 2, REVISION\nLOG 2, 1-5, 5-10,\t\n5-13, and 5-23\nFAA APPROVED 1-12-77 \nREISSUED 03-25-86 \nREVISION 4\nMU-2B-36A\n1, 2, REVISION \t\nLOG 2, 1-5, 2-10,\t\n5-10, 5-13, and 5-23\nFAA APPROVED 01-12-77 \nREISSUED 02-28-86 \nREVISION 6 \nMU-2B-40\n1, 2, REVISION \nLOG 2, 1-5, 2-10,\n5-10, 5-13, 5-14,\nand 5-24 \nFAA APPROVED 3-2-78 \nREISSUED 03-25-86 \nREVISION 4 \nMU-2B-60\n1, 2, REVISION \t\nLOG 2, 1-5, 2-9, \n5-10, 5-13, 5-14, \t\nand 5-24 \nFAA APPROVED 3-2-78 \nREISSUED 09-24-85REVISION 5 \nMU-2B-36\nModified by \nSTC SA2413SW\n1 through 31\nFAA APPROVED 2-1-78 \nREISSUED 12-18-92 \nREVISION 1\n\t\t\t\nThis incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Mitsubishi Heavy Industries, Ltd., 5-1 Marunouchi 2 Chome, Chiyoda-ku, Tokyo Japan. Copies may be inspected at the FAA, Central Region, Office of the Assistant Chief Counsel, Room 1558, 601 E. 12th Street, Kansas City, Missouri, or at the Office of the Federal Register, 800 North Capitol Street, NW., 7th Floor, suite 700, Washington, DC. \n\n\t(j)\tThis amendment becomes effective on June 10, 1994. \n\n\n\nFIGURE 2

A recent accident of a Mitsubishi Model MU-2B-60 airplane where the propeller hub assembly failed and the propeller separated from the airplane prompted the FAA and the National Transportation Safety Board (NTSB) to investigate the vibration frequency of these airplanes during ground idle operation. Accident investigation analysis indicates a reduction in fatigue strength of the propeller hub because of high vibration frequencies during ground idle speed. These high vibration frequencies, if not corrected, eventually will result in the above-referenced propeller hub assembly failure and separation of the propeller from the airplane. \n\n\tAfter examining the circumstances and reviewing all available information related to the incidents described above, the FAA has determined that (1) certain precautions (in addition to those taken by previous AD actions and during initial certification of the airplane) should be taken to minimize these high vibration frequencies during ground idle speed; and (2) AD action should be taken to prevent the above-referenced conditions. \n\n\tSince an unsafe condition has been identified that is likely to exist or develop in other Mitsubishi MU-2B series airplanes of the same type design, this AD requires adjusting the engine underspeed governor minimum stop (ground idle) and the airframe condition control linkage, modifying the tachometer indicator markings, fabricating and installing a placard that specifies a minimum idle speed, and incorporating Airplane Flight Manual (AFM) revisions. The ground idle modification is required to be accomplished in accordance with the Allied Signal Garrett Maintenance Manual (Report No. 72-00-95 for TPE331-10-501M or Report No. 72-00-27 for TPE331-501M or -511M), chapter 72-00-00, General-Adjustment /Test; and chapter 76-10-01, Control Linkage Assembly, Maintenance Practices. The airframe control linkage modification is required to be accomplished in accordance with Chapter6, Section 9.2, of the applicable Mitsubishi MU-2 maintenance manual. The revisions to the applicable Airplane Flight Manual are as follows: \n\n\nEffective Model\nPages\nDate and Revision Level\nMU-2B-26A\n1, 2, REVISION\t\nLOG 2, 1-5, 5-10,\n5-13, and 5-23\t\nFAA APPROVED 1-12-77 \nREISSUED 03-25-86 \nREVISION 4\nMU-2B-36A\n1, 2, REVISION \t\nLOG 2, 1-5, 2-10,\t\n5-10, 5-13, and 5-23\nFAA APPROVED 01-12-77 \nREISSUED 02-28-86 \nREVISION 6 \nMU-2B-40\n1, 2, REVISION \t\nLOG 2, 1-5, 2-10,\t\n5-10, 5-13, 5-14, \t\nand 5-24 \nFAA APPROVED 3-2-78 \nREISSUED 03-25-86 \nREVISION 4 \nMU-2B-60\n1, 2, REVISION \t\nLOG 2, 1-5, 2-9, \t\n5-10, 5-13, 5-14, \t\nand 5-24 \nFAA APPROVED 3-2-78 \nREISSUED 09-24-85 \nREVISION 5 \nMU-2B-36\nModified by \nSTC SA2413SW\n1 through 31\nFAA APPROVED 2-1-78 \nREISSUED 12-18-92 \nREVISION 1 \n\n\tSince a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for public prior comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days. \n\nComments Invited \n\n\tAlthough this action is in the form of a final rule that involves requirements affecting immediate flight safety and, thus, was not preceded by notice and opportunity to comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications should identify the Rules Docket number and be submitted in triplicate to the address specified above. All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed. \n\n\tComments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket. \n\n\tCommenters wishing the FAA to acknowledge receipt of their comments submitted in response to this notice must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket No. 94-CE-09-AD." The postcard will be date stamped and returned to the commenter. \n\n\tThe regulations adopted herein will not have substantial direct effects 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. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment. \n\n\tThe FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket (otherwise, an evaluation is not required). A copy of it, if filed, may be obtained from the Rules Docket. \n\nList of Subjects in 14 CFR Part 39 \n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \n\nAdoption of the AmendmentAccordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows: \n\nPART 39 - AIRWORTHINESS DIRECTIVES \n\t1.\tThe authority citation for part 39 continues to read as follows: \nAuthority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89. \n\nSection 39.13 - (AMENDED) \n\t2.\tSection 39.13 is amended by adding a new airworthiness directive to read as follows: