AD 97-18-04

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 757 series airplanes, that currently requires repetitive inspections to detect fatigue cracking in the midspar fuse pins; replacement with new or refinished fuse pins, if necessary; and repetitive inspections of newly installed fuse pins. This AD requires earlier initial inspections and replacements; more frequent repetitive inspections of certain fuse pins; and replacement with new fuse pins, if necessary. This amendment is prompted by reports of fatigue cracking of the midspar fuse pins and by fatigue test data indicating that current inspection thresholds and intervals for repetitive inspections are inadequate to detect fatigue cracking in a timely manner. The actions specified in this AD are intended to detect and correct such fatigue cracking, which could lead to separation of the strut and engine from the wing of the airplane.

Final rule; request for comments.

97-18-04 BOEING: Amendment 39-10114. Docket 97-NM-125-AD. Supersedes AD 96-05-08, Amendment 39-9534. \n\n\tApplicability: Model 757 series airplanes equipped with Rolls Royce engines, 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 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 (f) 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\tNOTE 2: Inspections accomplished prior to the effective date of this amendment, in accordance with the procedures described in Boeing Service Bulletin 757-54A0020, Revision 5, dated March 17, 1994; Revision 4, dated May 27, 1993; Revision 3, dated March 26, 1992; or Revision 2, dated October 11, 1989; are considered acceptable for compliance with the applicable inspections specified in this amendment. \n\n\tTo detect and correct fatigue cracking of the midspar fuse pins, which could lead to separation of the strut and engine from the wing of the airplane, accomplish the following: \n\n\t(a)\tFor airplanes equipped with straight fuse pins, part number (P/N) 311N5067-1: Prior to the accumulation of 2,500 total flight cycles on the straight fuse pin, or within 60 days after the effective date of this AD, whichever occurs later, perform an eddy current inspection to detect fatigue cracking in the fuse pin, in accordance with Boeing Alert Service Bulletin 757-54A0020, Revision 6, dated July 18, 1997. \n\n\t\t(1)\tIf no cracking is detected, repeat the inspection thereafter at intervals not to exceed 750 flight cycles on the straight fuse pin. \n\n\t\t(2)\tIf any cracking is detected, prior to further flight, accomplish the requirements of either paragraph (a)(2)(i) or (a)(2)(ii) of this AD. \n\n\t\t\t(i)\tReplace the cracked straight fuse pin with a new straight fuse pin, P/N 311N5067-1, and prior to the accumulation of 2,500 total flight cycles on the newly installed straight fuse pin, perform an eddy current inspection to detect fatigue cracking in the fuse pin, in accordance with the alert service bulletin. Repeat the inspection thereafter at intervals not to exceed 750 flight cycles on the newly installed straight fuse pin. Or \n\n\t\t\t(ii)\tReplace the cracked straight fuse pin with a new 15-5PH fuse pin, P/N 311N5217-1, and prior to the accumulation of 14,000 total flight cycles on the newly installed 15-5PH fuse pin, perform an eddy current inspection to detect fatigue cracking in the fuse pin, in accordance with the procedures described in the alert service bulletin. Repeat the inspection thereafter at intervals not to exceed 3,500 flight cycles on the newly installed 15-5PH fuse pin. \n\n\t(b)\tFor airplanes equipped with refinished straight fuse pins, P/N 311N5067-1: Prior to the accumulation of 750 total flight cycles on the refinished straight fuse pin, or within 60 days after the effective date of this AD, whichever occurs later, perform an eddy current inspection to detect fatigue cracking in the fuse pin, in accordance with Boeing Alert Service Bulletin 757-54A0020, Revision 6, dated July 18, 1997. \n\n\t\t(1)\tIf no cracking is detected, repeat the inspection thereafter at intervals not to exceed 750 flight cycles on the refinished straight fuse pin. \n\n\t\t(2)\tIf any cracking is detected, prior to further flight, accomplish the requirements of either paragraph (b)(2)(i) or (b)(2)(ii) of this AD. \n\n\t\t\t(i)\tReplace the cracked fuse pin with a new straight fuse pin, P/N 311N5067-1, and prior to the accumulation of 2,500 total flight cycles on the newly installed straight fuse pin, perform an eddy current inspection to detect fatigue cracking in the new straight fuse pin, in accordance with the procedures described in the alert service bulletin. Repeat this inspection thereafter at intervals not to exceed 750 flight cycles on the newly installed straight fuse pin. Or \n\n\t\t\t(ii)\tReplace the cracked fuse pin with a new 15-5PH fuse pin, P/N 311N5217-1, and prior to the accumulation of 14,000 total flight cycles on the newly installed 15-5PH fuse pin, perform an eddy current inspection to detect fatigue cracking in the fuse pin, in accordance with the procedures described in the alert service bulletin. Repeat the inspection thereafter at intervals not to exceed 3,500 flight cycles on the newly installed 15-5PH fuse pin. \n\n\t(c)\tFor airplanes equipped with bulkhead fuse pins, P/N 311N5211-1: Within 3,000 flight cycles on the bulkhead fuse pins after April 10, 1996 (the effective date of AD 96-05-08, amendment 39-9534), replace the bulkhead fuse pin with a new 15-5PH fuse pin, P/N 311N5217-1, in accordance with Boeing Service Bulletin 757-54A0020, Revision 5, dated March 17, 1994, or Boeing Alert Service Bulletin 757-54A0020, Revision 6, dated July 18, 1997, and accomplish the requirements of paragraph (d) of this AD. \n\n\t(d)\tFor airplanes equipped with 15-5PH fuse pins: Prior to the accumulation of 14,000 total flight cycles on the 15-5PH fuse pins, perform an eddy current inspection to detect fatigue cracking in those fuse pins, in accordance with the procedures described in Boeing Alert Service Bulletin 757-54A0020, Revision 6, dated July 18, 1997. \n\n\t\t(1)\tIf no cracking is detected, repeat the inspection thereafter at intervals not to exceed 3,500 flight cycles on the 15-5PH fuse pin. \n\n\t\t(2)\tIf any cracking is detected, prior to further flight, replace thecracked 15-5PH fuse pin with a new 15-5PH fuse pin, P/N 311N5217-1, and prior to the accumulation of 14,000 total flight cycles on the newly installed 15-5PH fuse pin, perform an eddy current inspection to detect fatigue cracking in the newly installed 15-5PH fuse pin; in accordance with the procedures described in the alert service bulletin. Repeat the inspection thereafter at intervals not to exceed 3,500 flight cycles on the newly installed 15-5PH fuse pin. \n\n\t(e)\tFuse pins must be of the same type on the same strut. For example, a steel fuse pin having P/N 311N5067-1 may not be installed on the same strut that has a 15-5PH fuse pin having P/N 311N5217-1 installed on that strut. However, fuse pins on one strut may differ from those on another strut, provided the fuse pins are not of mixed types on the same strut. \n\n\t(f)\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 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. \n\n\tNOTE 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. \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)\tThe inspections and replacements shall be done in accordance with Boeing Service Bulletin 757-54A0020, Revision 5, dated March 17, 1994, or Boeing Alert Service Bulletin 757- 54A0020, Revision 6, dated July 18, 1997. \n\n\t\t(1)\tThe incorporation by reference of Boeing Alert Service Bulletin 757-54A0020, Revision 6, dated July 18, 1997, was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. \n\n\t\t(2)\tThe incorporation by reference of Boeing Service Bulletin 757-54A0020, Revision 5, dated March 17, 1994, 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 April 10, 1996 (61 FR 9601, March 11, 1996). \n\n\t\t(3)\tCopies 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(i)\tThis amendment becomes effective on September 17, 1997.

On March 1, 1996, the FAA issued AD 96-05-08, amendment 39-9534 (61 FR 9601, March 11, 1996), applicable to certain Boeing Model 757 series airplanes. That AD requires repetitive inspections to detect cracking in the midspar fuse pins, regardless of whether they are straight, bulkhead, or 15-5PH fuse pins, and replacement of discrepant pins with new straight fuse pins, refinished straight fuse pins, or new corrosion-resistant steel (15-5PH) fuse pins, depending on the type of cracked pin. The actions required by that AD are intended to prevent cracking of the midspar fuse pins, which may lead to separation of the strut and engine from the wing of the airplane. \n\nActions Since Issuance of Previous Rule \n\n\tSince the issuance of AD 96-05-08, the FAA has received several reports indicating the detection of fatigue cracking on two straight fuse pins and one broken straight fuse pin on Model 757 series airplanes equipped with Rolls Royce engines. In theseinstances, damage to the fuse pins was detected before reaching the threshold specified in AD 96-05-08 for conducting an initial inspection of the fuse pins. In addition, since the issuance of that AD, the FAA was informed by Boeing that refinished straight fuse pins have a shorter fatigue life than new straight fuse pins. \n\n\tBased on data from fatigue testing by the manufacturer and the reports of early cracking, the FAA finds that the current inspection thresholds and intervals for repetitive inspections are inadequate to detect cracking in a timely manner. Consequently, it is necessary to lower the threshold for the initial inspection and conduct repetitive inspections of these fuse pins more frequently than currently required by AD 96-05-08. In addition, the FAA has determined that the action specified in paragraph (b)(2)(i) of AD 96-05-08, which requires the replacement of cracked refinished straight fuse pins with crack-free refinished straight fuse pins, is no longer acceptable. The FAA concludes that, because of the safety implications and consequences associated with the fatigue cracking of fuse pins, the replacement of refinished straight fuse pins must be made with either new straight fuse pins or new 15-5PH fuse pins. However, the FAA has determined that the existing refinished straight fuse pins, which are already installed on Boeing Model 757 series airplanes and do not have cracks, may continue in use in accordance with the requirements of this AD. \n\n\tThe FAA is considering a separate rulemaking action to address the same unsafe condition on certain Model 757 airplanes equipped with Pratt & Whitney engines. \n\nExplanation of Relevant Service Information \n\n\tSince the issuance of AD 96-05-08, the FAA has reviewed and approved Boeing Alert Service Bulletin 757-54A0020, Revision 6, dated July 18, 1997, which continues specifications similar to those in Boeing Service Bulletin 757-54A0020, Revision 5, dated March 17, 1994 (which was referenced in AD 96-05-08 as the appropriate source of service information). The relevant changes in Revision 6 are procedures for earlier initial inspections and replacements; more frequent repetitive inspections of certain fuse pins; and replacement with new fuse pins, if necessary. In addition, Revision 6 specifies the replacement of cracked refinished straight fuse pins with new straight fuse pins or 15-5PH fuse pins. \n\nExplanation of Requirements of Rule \n\n\tSince an unsafe condition has been identified that is likely to exist or develop on other airplanes of this same type design, this AD supersedes AD 96-05-08 to continue to require repetitive inspections to detect cracking in the midspar fuse pins; replacement with new or refinished fuse pins, if necessary; and repetitive inspections of newly installed fuse pins. This AD requires earlier initial inspections and replacements; more frequent repetitive inspections of certain fuse pins; and replacement with new fuse pins, if necessary.This AD also requires the replacement of cracked refinished straight fuse pins with new straight fuse pins or 15-5PH fuse pins. These actions are required to be accomplished in accordance with Revision 6 of the alert service bulletin described previously. \n\nDifferences Between the AD and the Relevant Service Bulletin \n\n\tOperators should note that, although Boeing Alert Service Bulletin 757-54A0020, Revision 6, dated July 18, 1997, specifies that a cracked bulkhead fuse pin may be replaced with either a new straight fuse pin or a new 15-5PH fuse pin, this AD requires a bulkhead fuse pin to be replaced only with a new 15-5PH fuse pin. The FAA has determined that because 15-5PH fuse pins are made from corrosion-resistant steel, 15-5PH fuse pins are less likely to be subject to fatigue cracking and stress corrosion cracking and, as a result, have a longer service life than straight fuse pins or bulkhead fuse pins. The FAA also considers that this action is necessary to support the continued airworthiness of Boeing Model 757 series airplanes equipped with Rolls Royce engines. \n\n\tOperators also should note that Revision 6 of the previously described alert service bulletin specifies the replacement of bulkhead fuse pins within 6,000 total flight cycles on the bulkhead fuse pins. However, this AD requires the replacement of bulkhead fuse pins within 3,000 flight cycles on the bulkhead fuse pins after April 10, 1996, the effective date of AD 96-05-08. The FAA has determined that continuing the requirement for such replacement, which was required in AD 96-05-08, is sufficient to detect and correct the initiation and propagation of fatigue cracking in the midspar fuse pins. \n\n\tIn addition, operators should note that the applicability of this AD differs from the effectivity listing in Revision 6 of the previously referenced alert service bulletin. The FAA has determined that to adequately address the problem of fatigue cracking in the midspar fuse pins, this AD should include Model 757 series airplanes (all serial numbers) equipped with Rolls Royce engines, as previously specified in AD 96-05-08. \n\nInterim Action \n\n\tThis is considered to be interim action until final action is identified, at which time the FAA may consider further rulemaking. \n\nDetermination of Rule's Effective Date \n\n\tSince a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in fewer than 30 days. \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 theRules 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 97-NM-125-AD." The postcard will be date stamped and returned to the commenter. \n\nRegulatory Impact \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. The authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. 106(g), 40113, 44701. § 39.13 - (Amended) \n\t2. Section 39.13 is amended by removing amendment 39-9534 (61 FR 9601, March 11, 1996), and by adding a new airworthiness directive (AD), amendment 39-10114, to read as follows: