[Federal Register Volume 61, Number 193 (Thursday, October 3, 1996)] [Proposed Rules] [Pages 51624-51625] From the Federal Register Online via the Government Publishing Office [www.gpo.gov] [FR Doc No: 96-25307] ----------------------------------------------------------------------- DEPARTMENT OF TRANSPORTATION 14 CFR Part 39 [Docket No. 96-NM-67-AD] RIN 2120-AA64 Airworthiness Directives; Boeing Model 737-300, -400, and -500 Series Airplanes AGENCY: Federal Aviation Administration, DOT. ACTION: Notice of proposed rulemaking (NPRM). ----------------------------------------------------------------------- SUMMARY: This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 737-300, - 400, and -500 series airplanes. This proposal would require replacing certain aileron/rudder trim control modules with a new module that contains an improved rudder trim switch to reduce internal friction. This proposal is prompted by reports of sticking conditions in the rudder trim switch. The actions specified by the proposed AD are intended to prevent such sticking, which could result in uncommanded movement of the rudder and consequent deviation of the airplane from its set course. DATES: Comments must be received by November 12, 1996. ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-103, Attention: Rules Docket No. 96-NM-67-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal holidays. The service information referenced in the proposed rule may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington. FOR FURTHER INFORMATION CONTACT: Hania Younis, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington; telephone (206) 227-2764; fax (206) 227-1181. SUPPLEMENTARY INFORMATION: Comments Invited Interested persons are invited to participate in the making of the proposed 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 above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this notice may be changed in light of the comments received. Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with the substance of this proposal will be filed in the Rules Docket. Commenters 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 Number 96-NM-67-AD.'' The postcard will be date stamped and returned to the commenter. Availability of NPRMs Any person may obtain a copy of this NPRM by submitting a request to the FAA, Transport Airplane Directorate, ANM-103, Attention: Rules Docket No. 96-NM-67-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Discussion The FAA has received reports of sticking conditions in the rudder trim switch on electric aileron/rudder trim control module P8-43 on certain Model 737 series airplanes. One such report involved an airplane that was climbing, under manual control, through an altitude of 6,700 feet. The airplane began to yaw slightly to the left and the flight crew felt some force on the rudder pedals; although the rudder trim switch knob was centered, the rudder trim indicator showed that the rudder was set at an angle of 16 degrees left of where it was supposed to be. If the trim switch sticks, it may be prevented from returning to the center position. If this happens, the rudder trim actuator may continue to move the rudder at a slow rate, up to the trim limit. This rate of movement is very slow, however, at approximately 1/2 deg. per second, which should provide ample time for the flight crew to detect and correct the movement before it creates a situation of concern. In most cases, these types of incidents can be stopped if the pilot merely puts the switch into the center position [[Page 51625]] manually. In all incidents of this type, the rudder movement can by stopped by use of the rudder pedals within the normal limits for yaw control. Sticking conditions in the rudder trim switch if not corrected, however, could result in uncommanded movement of the rudder, and consequent deviation of the airplane from its set course. Explanation of Relevant Service Information The FAA has reviewed and approved Boeing Alert Service Bulletin 737-27A1198, dated June 6, 1996, which describes procedures for replacing aileron/rudder trim control module P8-43 with a new module that contains an improved switch. This improved module minimizes internal friction that has caused the sticking conditions. Explanation of Requirements of Proposed Rule Since an unsafe condition has been identified that is likely to exist or develop on other products of this same type design, the proposed AD would require replacing the aileron/rudder trim control module P8-43 with a new improved module. The actions would be required to be accomplished in accordance with the alert service bulletin described previously. Cost Impact There are approximately 1,159 Boeing Model 737-300, -400, and -500 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 537 airplanes of U.S. registry would be affected by this proposed AD. Replacement of the module would take approximately 3 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts would cost approximately $1,063 per airplane. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $667,491, or $1,243 per airplane. The cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the proposed requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. Regulatory Impact The regulations proposed herein would 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 proposal would not have sufficient federalism implications to warrant the preparation of a Federalism Assessment. For the reasons discussed above, I certify that this 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) if promulgated, 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. A copy of the draft regulatory evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption ADDRESSES. List of Subjects in 14 CFR Part 39 Air transportation, Aircraft, Aviation safety, Safety. The Proposed Amendment Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend part 39 of the Federal Aviation Regulations (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. Section 39.13 is amended by adding the following new airworthiness directive: Boeing: Docket 96-NM-67-AD. Applicability: Model 737-300, -400, and -500 series airplanes; as listed in Boeing Alert Service Bulletin 737-27A1198, dated June 6, 1996; certified in any category. Note 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been otherwise 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 request approval for an alternative method of compliance in accordance with paragraph (b) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it. Compliance: Required as indicated, unless accomplished previously. To prevent sticking conditions in the rudder trim switch, which could result in uncommanded movement of the rudder and consequent deviation of the airplane from its set course, accomplish the following: (a) Within 2 years after the effective date of this AD, replace the aileron/rudder trim control module P8-43 having part number (P/ N) 69-73703-5 or 69-73703-6 with a new aileron/rudder trim control module having P/N 69-73703-8, in accordance with Boeing Alert Service Bulletin 737-27A1198, dated June 6, 1996. (b) An 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 Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. 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. Note 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. (c) Special 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. Issued in Renton, Washington, on September 26, 1996. Darrell M. Pederson, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 96-25307 Filed 10-2-96; 8:45 am] BILLING CODE 4910-13-U