AD 95-06-53

This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) T95-06-53 that was sent previously to all known U.S. owners and operators of Boeing Model 737 series airplanes by individual telegrams. This AD requires identification of the part and serial numbers of the main rudder power control unit (PCU), and replacement of certain PCU's with serviceable parts, if necessary. This amendment is prompted by reports indicating that certain modified rudder PCU's malfunctioned and failed functional retesting. The actions specified by this AD are intended to prevent the rudder actuator piston and the rudder from operating with reduced force capability or moving in a direction opposite the intended direction due to malfunctioning of the rudder PCU; these conditions could result in reduced controllability of the airplane.

Final rule; request for comments

95-06-53 BOEING: Amendment 39-9199. Docket 95-NM-37-AD. \n\n\tApplicability: All Model 737 series airplanes, certificated in any category. \n\n\tNOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must use the authority provided in paragraph (d) to request approval from the FAA. This approval may address either no action, if the current configuration eliminates the unsafe condition; or different actions necessary to address the unsafe condition described in this AD. Such a request should include an assessment of the effect of the changed configuration on the unsafe condition addressed by this AD. In no case does the presence of any modification, alteration, or repair remove any airplane from the applicability of this AD. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo prevent the rudder actuator piston and the rudder from operating with reduced force capability or moving in a direction opposite the intended direction, and resultant reduced controllability of the airplane, accomplish the following: \n\n\t(a)\tWithin 5 flights after the effective date of this AD, identify the part number and serial number of the main rudder power control unit (PCU). \n\n\t(b)\tIf the PCU is identified with a part number and serial number specified in the list below, prior to further flight, remove the PCU from the airplane, and replace it with a serviceable part. \n\n\nPart Number\nSerial Number(s) \n65C37052-3\n17SS, 49, 90A, 101, \n138, 149A, 191A, \n308A, 374, EGG0282 \n65C37052-5\n1211A \n65C37052-7\n399A, 710A, 926A, \n935A, 1175A, 1237A, \n1493A, 1504A, 1546, \n1561A, 67700 \n65C37052-8\n1090A, 1223, 1920, \n2023A \n65C37052-9\n0184, 247, 394A, 641A, \n1739A, 1746A, 1796A, \n1849A, 1997A, 2181A \n\n\t(c)\tAs of the effective date of this AD, no person shall install on any airplane a rudder PCU having a part number and serial number that is specified in the list contained in paragraph (b) of this AD unless paragraphs (c)(1), (c)(2), (c)(3), and (c)(4) of this AD are accomplished. \n\n\t\t(1)\tPerform a functional test of the PCU in accordance with Part II of the Accomplishment Instructions of Boeing Service Bulletin 737-27-1185, dated April 15, 1993. And \n\n\t\t(2)\tCheck the torque value on the spring retainer, Part Number 68021-5, to determine that it measures a minimum of 25 inch-pounds. If the torque value is less than 25 inch- pounds, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. And \n\n\t\t(3)\tRepeat the functional test required by paragraph (c)(1) of this AD. The PCU must pass this functional test in order to be returned to service. And \n\n\t\t(4)\tThe measurement required by paragraph (c)(2) of this AD must be reported to the FAA, Transport Airplane Directorate, Seattle ACO, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; fax (206) 227-1181. Information collection requirements contained in this regulation have been approved by the Office of Management and Budget (OMB) under the provisions of the Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.) and have been assigned OMB Control Number 2120-0056. \n\n\t(d)\tAn alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Seattle ACO. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO. \n\n\tNOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.(e)\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(f)\tThe functional test shall be done in accordance with Boeing Service Bulletin 737-27- 1185, dated April 15, 1993. The incorporation by reference of this document was approved previously by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51 as of March 3, 1994 (59 FR 4570, February 1, 1994). Copies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. \n\n\t(g)\tThis amendment becomes effective on May 1, 1995, to all persons except those personsto whom it was made immediately effective by telegraphic AD T95-06-53, issued on March 14, 1995, which contained the requirements of this amendment.

On January 3, 1994, the FAA issued AD 94-01-07, amendment 39-8789 (59 FR 4570, February 1, 1994), which is applicable to certain Boeing Model 737 series airplanes. That AD requires repetitive tests of existing main rudder power control units (PCU), and eventual replacement of the main rudder PCU with a modified PCU. The modified PCU also was required to be functionally tested following modification and prior to installation. Recently, the FAA received two reports of in-service malfunctioning of certain rudder PCU's that had been modified by Aero Controls, Inc. Subsequently, these PCU's were removed from the airplanes and failed functional retesting. \n\n\tIn both of the reported cases, the secondary slide in the servo valve of these PCU's went past the intended maximum travel position. An examination of the PCU's tested revealed that the spring retainer backed off from the spring guide. If the secondary slide goes past the intended maximum travel position, the rudder actuator piston and the rudder could operate with reduced force capability or move in a direction opposite the intended direction. These conditions, if not corrected, could result in reduced controllability of the airplane. \n\n\tResults of a preliminary investigation indicate that Aero Controls, Inc., may not have been using the proper tool to torque the spring retaining nut. The FAA has identified 36 PCU's that may have been modified and/or tested incorrectly by that repair station. This AD affects only those PCU's modified and/or tested by Aero Controls, Inc. The FAA is currently in the process of verifying that other repair stations and operators have properly modified and tested PCU's. \n\n\tThe FAA has confirmed that the PCU installed on the USAir Model 737 series airplane that was involved in an accident near Pittsburgh in September 1994 had not been modified. The PCU from that airplane has been subjected to thorough functional testing, and no evidence of failures or deficiencies has been found. The investigation of that accident is continuing. No determination has been made that the PCU was the cause of that accident. This AD is being issued to correct the conditions described above and is not related to the results of the Pittsburgh accident investigation. \n\n\tSince the unsafe condition described is likely to exist or develop on other airplanes of the same type design, the FAA issued Telegraphic AD T95-06-53. The AD requires identification of the part number and serial number of the main rudder PCU, and replacement of certain PCU's with serviceable parts, if necessary. \n\n\tAs a result of recent communications with the Air Transport Association (ATA) of America, the FAA has learned that, in general, some operators may misunderstand the legal effect of AD's on airplanes that are identified in the applicability provision of the AD, but that have been altered or repaired in the area addressed by the AD. The FAA points out that all airplanes identified in the applicability provision of an AD are legally subject to the AD. If an airplane has been altered or repaired in the affected area in such a way as to affect compliance with the AD, the owner or operator is required to obtain FAA approval for an alternative method of compliance with the AD, in accordance with the paragraph of each AD that provides for such approvals. A note has been included in this rule to clarify this long-standing requirement. \n\n\tSince it was found that immediate corrective action was required, notice and opportunity for prior public comment thereon were impracticable and contrary to the public interest, and good cause existed to make the AD effective immediately by individual telegrams issued on March 14, 1995, to all known U.S. owners and operators of Boeing Model 737 series airplanes. These conditions still exist, and the AD is hereby published in the Federal Register as an amendment to section 39.13 of the Federal Aviation Regulations(14 CFR 39.13) to make it effective to all persons.\n\nComments Invited \n\n\tAlthough this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public 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 shall identify the Rules Docket number and be submitted in triplicate to the address specified under the caption "ADDRESSES." 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 rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 95-NM-37-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 that it 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. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES." \n\nList of Subjects in 14 CFR Part 39 \n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \nAdoption of the Amendment \n\n\tAccordingly, 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\n PART 39 - AIRWORTHINESS DIRECTIVES \n\n\t1.\tThe authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89. § 39.13 - (Amended) \n\n\t2.\tSection 39.13 is amended by adding the following new airworthiness directive: