AD 97-19-18

This amendment supersedes an existing airworthiness directive (AD), applicable to AlliedSignal Inc. (formerly AiResearch and Garrett) TSCP700-4B and -5 Series Auxiliary Power Units (APUs), that currently requires restretching the first stage low pressure compressor (LPC) tie rods, or replacing affected disks at or before 8,000 cycles since new (CSN). This amendment requires removing from service affected disks, replacing them with serviceable parts, and establishing a life limit of 8,000 CSN for affected disks. This amendment is prompted by a report of a first stage LPC disk rim separation due to low cycle fatigue on an APU that had its tie rods restretched in accordance with the current AD. The actions specified by this AD are intended to prevent first stage LPC disk rim separation due to low cycle fatigue, which could result in an uncontained APU failure and damage to the aircraft.

Final rule.

97-19-18 ALLIEDSIGNAL INC.: Amendment 39-10138. Docket 97-ANE-03. Supersedes AD 88-24-07, Amendment 39-6062. \n\n\tApplicability: AlliedSignal Inc. (formerly AiResearch and Garrett) TSCP700-4B and -5 auxiliary power units (APUs), with first stage low pressure compressor (LPC) disks, Part Number (P/N) 3606429-1, installed on but not limited to Airbus A300 series, and McDonnell Douglas DC-10 and KC-10 (military) series aircraft. \n\n\tNote 1: This airworthiness directive (AD) applies to each APU 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 APUs 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 (e) 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. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo prevent first stage LPC disk rim separation due to low cycle fatigue, which could result in an uncontained APU failure and damage to the aircraft, accomplish the following: \n\n\t(a)\tRemove from service first stage LPC disks, P/N 3606429-1, in accordance with the schedule derived from calculations in paragraph C.(3) of AlliedSignal Service Bulletin (SB) No. TSCP700-49-7266, dated June 16, 1996, and the removal procedures described in the Accomplishment Instructions of that SB, and replace with serviceable parts. \n\n\t(b)\tExcept as provided in paragraph (a), this AD establishes a life limit of 8,000 cycles since new (CSN) for first stage LPC disks, P/N 3606429-1. \n\n\t(c)\tThe definition of a disk cycle may be found in the applicable AlliedSignal Inc. APU Component Maintenance Manual. \n\n\t(d)\tExcept as provided in paragraph (e) of this AD, no alternative replacement times may be approved for first stage LPC disks, P/N 3606429-1. \n\n\t(e)\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. 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 Aircraft Certification Office. \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 Aircraft Certification Office. \n\n\t(f)\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 aircraft to a location where the requirements of this AD can be accomplished. \n\n\t(g)\tThe actions required by this AD shall be done in accordance with the following AlliedSignal Inc. SB: \n\n\nDocument No.\nPages\nDate\nTSCP700-49-7266\n1-6\nJune 16, 1996\nTotal pages: 6.\n\n\n\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 AlliedSignal Aerospace, Attn: Data Distribution, M/S 64-3/2101-201, P.O. Box 29003, Phoenix, AZ 85038-9003; telephone (602) 365-2493, fax (602) 365-5577. Copies may be inspected at the FAA, New England Region, Office of the Assistant Chief Counsel, 12 New England Executive Park, Burlington, MA; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. \n\n\t(h)\tThis amendment becomes effective on October 27, 1997.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 88-24-07, Amendment 39-6062 (53 FR 46439, November 17, 1988), which is applicable to AlliedSignal Inc. (formerly AiResearch and Garrett) TSCP700-4B and -5 series auxiliary power units (APUs), was published in the Federal Register on March 18, 1997 (62 FR 12774). That action proposed to eliminate the option of restretching the tie rods, and require removing from service affected disks in accordance with a schedule derived from calculations in AlliedSignal Inc. Service Bulletin (SB) No. TSCP700-49-7266, dated June 16, 1996, replacing affected disks with serviceable parts, and establishing a life limit of 8,000 cycles since new (CSN) for affected disks.\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 (the manufacturer) states thatthe AD should not imply that the tie rod restretch is ineffective, as the manufacturer believes that the tie rod restretch is beneficial in minimizing disk liberation. The FAA concurs that tie rod restretching is beneficial; however, the FAA has determined through analysis that the life limit of affected disks must be reduced to 8,000 CSN regardless of tie rod restretch in order to ensure safe operation.\n\n\tThree commenters concur with the rule as proposed.\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 described previously. 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\tThe FAA estimates that 100 APUs installed on aircraft of U.S. registry will be affected by this AD, no additional work hours per APU to accomplish the proposed actions if the actions are accomplished during APU overhaul, 8 work hours to accomplish the required actions if the actions are not accomplished during APU overhaul, and that the average labor rate is $60 per work hour. Based on these figures, and that the work would not be performed during overhaul, the total cost impact of the AD on U.S. operators is estimated to be $48,000.\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\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 39\n\tAir Transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.\n\nAdoption of the Amendment \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\t1. The authority citation for part 39 continues to read as follows:\n\tAuthority: 49 U.S.C. 106(g), 40113, 44701.\n\n§ 39.13 (Amended)\n\t2. Section 39.13 is amended by removing Amendment 39-6062 (53 FR 46439, November 17, 1988) and by adding a new airworthiness directive, Amendment 39-10138, to read as follows: