AD 95-11-12

This amendment adopts a new airworthiness directive (AD), applicable to certain McDonnell Douglas Model DC-9, DC-9-80, and C-9 (military) series airplanes, and Model MD-88 airplanes, that requires repetitive replacement of the emergency power switch in the overhead switch panel with a new switch. This amendment is prompted by a report of heavy smoke in the cockpit coming from the overhead switch panel on a Model DC-9-81 series airplane. The actions specified by this AD are intended to ensure replacement of the emergency power switch when it has reached its maximum life limit; an emergency power switch that is not replaced could fail and lead to a short in the electrical circuit, which could result in a fire in the overhead switch panel and smoke in the cockpit.

Final rule.

95-11-12 MCDONNELL DOUGLAS: Amendment 39-9245. Docket 94-NM-194-AD. \n\n\tApplicability: Model DC-9-10, -20, -30, -40, and -50 series airplanes; Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83), and DC-9-87 (MD-87) series airplanes; Model MD-88 airplanes; and C-9 (military) series airplanes; as listed in McDonnell Douglas DC-9 Service Bulletin 24-150, dated March 28, 1994; 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 (b) 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 ensure replacement of the emergency power switches that have reached the maximum life limit, accomplish the following: \n\n\t(a)\tPrior to the accumulation of 3 years since installation of the emergency power switch in the overhead switch panel, or within 12 months after the effective date of this AD, whichever occurs later, replace the emergency power switch with a new switch in accordance with the procedures specified in McDonnell Douglas DC-9 Service Bulletin 24-150, dated March 28, 1994, or Revision 1, dated April 7, 1995. Thereafter, replace the emergency power switch at intervals not toexceed 3 years. \n\n\t(b)\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, Los Angeles 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, Los Angeles 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 Los Angeles ACO. \n\n\t(c)\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(d)\tThe replacement shall be done in accordance with McDonnell Douglas DC-9 Service Bulletin 24-150, dated March 28, 1994; or McDonnell Douglas DC-9Service Bulletin 24-150, Revision 1, dated April 7, 1995. This 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 McDonnell Douglas Corporation, 3855 Lakewood Boulevard, Long Beach, California 90846, Attention: Technical Publications Business Administration, Department C1-L51 (2-60). Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Los Angeles Aircraft Certification Office, Transport Airplane Directorate, 3960 Paramount Boulevard, Lakewood, California; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. \n\n\t(e)\tThis amendment becomes effective on July 3, 1995.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain McDonnell Douglas Model DC-9, DC-9-80, and C-9 (military) series airplanes, and Model MD-88 airplanes was published in the Federal Register on December 20, 1994 (59 FR 65518). That action proposed to require repetitively replacing the emergency power switch in the overhead switch panel with a new switch at regular intervals. \n\n\tInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received. \n\n\tOne commenter supports the proposed rule. \n\n\tTwo commenters request that the compliance time for accomplishment of the replacement be extended from the proposed 12 months to 18 months. One of these commenters states that such an extension will allow the replacement to be accomplished during a regularly scheduled maintenance check. The FAA does not concur. In developing an appropriate compliance time for this action, the FAA considered not only the degree of urgency associated with addressing the subject unsafe condition, but the availability of required parts and the practical aspect of installing the required replacement with a maximum interval of time allowable for all affected airplanes to continue to operate without compromising safety. Since maintenance schedules vary from operator to operator, there would be no assurance that the replacement will be accomplished during that time. The manufacturer has advised that an ample number of required parts will be available for replacement of the emergency power switch on the U.S. fleet within the proposed compliance period. However, under the provisions of paragraph (b) of the final rule, the FAA may approve requests for adjustments to the compliance time if data are presented to justify such an adjustment. \n\n\tSeveral commenters request thatthe compliance time for accomplishing the proposed replacement be based on switch cycle usage, rather than calendar time. Two commenters note that a compliance time based on a calendar time would impose a severe penalty on operators that cycle the switch only once a day and would also impose a somewhat lesser penalty on operators who cycle the switch on the first flight of the day and at crew changes. One commenter states that, due to the fact that the switches do not have counters to record actual switch cycles, it is critical that operators have the flexibility to establish an equivalent calendar time or airplane cycle limit based on their individual procedures for exercising these switches. \n\n\tThe FAA does not concur with the commenters' request to base the compliance time on switch cycles. Compliance times for AD's are normally based on a parameter related to failure of a particular component. In this case, the failure of the emergency power switch is undoubtedly related to the number of switch cycles. However, because switch cycles are not recorded, referencing switch cycles in the compliance time would make it impossible to verify compliance at the required time. Therefore, the FAA has selected a compliance time that equates to the approximate number of switch cycles specified in McDonnell Douglas DC-9 Service Bulletin 24- 150, assuming that the switch is cycled once for each flight cycle. Under provisions of paragraph (b) of the final rule, however, operators may apply for the approval of an extension of the compliance time if sufficient justification is presented to the FAA. For example, such justification may consist of data demonstrating that the operator only cycles the switch once a day, or at each crew change, rather than once per flight cycle. \n\n\tSince issuance of the proposal, the FAA has reviewed and approved McDonnell Douglas DC- 9 Service Bulletin 24-150, Revision 1, dated April 7, 1995, which describes the appropriate procedures for repetitively replacing the emergency power switch in the overhead switch panel with a new switch at regular intervals. Therefore, the final rule has been revised to reference this revision of the service bulletin as an additional source of service information. \n\n\tThe FAA points out that it inadvertently used the phrase "time-in-service" after the term "3 years" in paragraph (a) of the proposal when referring to the compliance threshold for installation of the emergency power switch. Since that phrase is inappropriate, the FAA has removed it from the final rule. Likewise, the FAA has removed that phrase from the reference to the repetitive replacement interval. \n\n\tAfter careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes previously described. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD. \n\n\tThere are approximately 1,990 Model DC-9, DC-9-80, and C-9 (military) series airplanes and Model MD-88 airplanes of the affected design in the worldwide fleet. The FAA estimates that 992 airplanes of U.S. registry will be affected by this AD, that it will take approximately 2 work hours per airplane to accomplish the required actions, and that the average labor rate is $60 per work hour. Required parts will cost approximately $1,434 per airplane. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $1,541,568, or $1,554 per airplane, per replacement cycle. \n\n\tThe total cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. \n\n\tThe regulations adopted herein will not have substantial direct effects on the States, on the relationshipbetween 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\tFor the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under 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. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES." \n\nList of Subjects in 14 CFR Part 39Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \n\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\nPART 39 - AIRWORTHINESS DIRECTIVES \n\n\t1.\tThe authority citation for part 39 continues to read as follows: \n\nAuthority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89. \n\n§ 39.13 - (Amended) \n\n\t2.\tSection 39.13 is amended by adding the following new airworthiness directive: