AD 95-25-01 ACTIVE

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 757 series airplanes, that currently requires various modifications and terminating actions for the passenger door, and repair, if necessary. This amendment requires additional inspections, and replacement of certain parts, if necessary. This amendment also provides for optional terminating action for certain inspections. This amendment is prompted by reports of excessive gaps between lockout cams and crank stops, which resulted in broken power assist triggers. The actions specified by this AD are intended to prevent broken power assist triggers, which could result in an inoperative door opening system during an emergency evacuation.

Final rule

95-25-01 BOEING: Amendment 39-9445. Docket 95-NM-07-AD. Supersedes AD 91-07-09, Amendment 39-6951. \n\n\tApplicability: Model 757 series airplanes, as listed in any of the following service bulletins: Boeing Service Bulletin 757-52-0042, dated March 30, 1989; Boeing Service Bulletin 757-52-0042, Revision 1, dated April 26, 1990; and Boeing Alert Service Bulletin 757-52A0023, Revision 3, dated November 18, 1993; 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 (f) of this AD 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 proper operation of the door opening system during an emergency evacuation, accomplish the following: \n\n\t(a)\tFor airplanes identified as Group 1 in Boeing Service Bulletin 757-52-0042, dated March 30, 1989, and Revision 1, dated April 26, 1990: Within 350 flight hours after January 6, 1990 (the effective date of AD 89-25-09, amendment 39-6407), accomplish paragraphs (a)(1), (a)(2), and (a)(3) of this AD, in accordance with either service bulletin. Any interference or improper clearance detected during any inspection required by this paragraph must be repaired, prior to further flight, in accordance with either service bulletin. \n\n\t\t(1)\tModify the forward right-hand passenger door. \n\n\t\t(2)\tInspect all passenger doors for evidence of interference between the trigger support housing and the upper hinge arm. \n\n\t\t(3)\tInspect all passenger doors for proper clearance between the power assist trigger and the door and fuselage skin. \n\n\t(b)\tFor all airplanes identified in Boeing Service Bulletin 757-52-0042, dated March 30, 1989, and Revision 1, dated April 26, 1990: Within 350 flight hours after January 6, 1990 (the effective date of AD 89-25-09, amendment 39-6407), and thereafter at intervals not to exceed 6 months, accomplish paragraphs (b)(1), (b)(2), (b)(3), and (b)(4) of this AD, in accordance with either service bulletin. Any damage, improper adjustment, or improper operation detected during any of the inspection required by this paragraph must be repaired, prior to further flight, in accordance with either service bulletin. \n\n\t\t(1)\tInspect the forward doors for proper adjustment of the lockout mechanism of the door emergency power assist system. \n\n\t\t(2)\tInspect all passenger door emergency power assist triggers for wear marks, damage, or fracture.\n\n\t\t(3)\tInspect trigger spring cylinders for proper operation. \n\n\t\t(4)\tInspect roller arms for damage. \n\n\t(c)\tFor all airplanes identified in Boeing Service Bulletin 757-52-0042, Revision 1, dated April 26, 1990: Within 18 months after April 29, 1991 (the effective date of AD 91-07-09, amendment 39-6951), accomplish paragraphs (c)(1), (c)(2), (c)(3), and (c)(4) of this AD, in accordance with Section III, Part III, of the service bulletin. Any damage, defect, improper adjustment, or improper operation detected during any inspection required by this paragraph must be repaired, prior to further flight, in accordance with the service bulletin. Accomplishment of the actions required by this paragraph constitutes terminating action for the periodic inspections required by paragraph (b) of this AD. \n\n\t\t(1)\tOn forward doors, install the lockout link and inspect the lockout mechanism for proper adjustment. \n\n\t\t(2)\tOn all passenger doors, install the new trigger guard, and inspect the emergency power assist triggers for wear marks, damage, or fracture. \n\n\t\t(3)\tOn all passenger doors, modify the trigger spring cylinder end cap and inspect the spring cylinder for proper operation. \n\n\t\t(4)\tOn all passenger doors, inspect roller arms for damage. \n\n\t(d)\tFor all airplanes identified in Boeing Alert Service Bulletin 757-52A0023, Revision 3, dated November 18, 1993: Within 6 months after the effective date of this AD, perform an inspection to detect wear marks, damage, or cracking on the upper surface of the emergency power assist triggers at all passenger doors, in accordance with the alert service bulletin. Repeat the inspection thereafter at intervals not to exceed 6 months. \n\n\t\t(1)\tIf any wear mark is detected, priorto further flight, repair in accordance with the alert service bulletin. \n\n\t\t(2)\tIf any damage or cracking is detected, prior to further flight, replace the power assist triggers in accordance with the alert service bulletin. \n\n\t(e)\tFor all airplanes identified in Boeing Alert Service Bulletin 757-52A0023, Revision 3, dated November 18, 1993: Within 6 months after the effective date of this AD, measure the clearance between the lockout cam and the crank stop, in accordance with the alert service bulletin. \n\n\t\t(1)\tIf the clearance between the lockout cam and the crank stop is within the limits specified in the alert service bulletin, no further action is required by this paragraph. \n\n\t\t(2)\tIf the clearance between the lockout cam and the crank stop is beyond the limits specified in the alert service bulletin, prior to further flight, accomplish the actions specified by either paragraph (e)(2)(i) or (e)(2)(ii) of this AD. \n\n\t\t\t(i)\tAdjust the lockout cam until the correct clearance is obtained, in accordance with the alert service bulletin. Or \n\n\t\t\t(ii)\tIf the correct clearance cannot be obtained by adjusting the lockout cam, replace the lockout cam in accordance with the alert service bulletin. \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 2: 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 therequirements of this AD can be accomplished. \n\n\t(h)\tThe actions shall be done in accordance with Boeing Service Bulletin 757-52-0042, Revision 1, dated April 26, 1990; and Boeing Alert Service Bulletin 757-52A0023, Revision 3, dated November 18, 1993. 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 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 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 January 16, 1996.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 91-07-09, amendment 39-6951 (56 FR 12111, March 22, 1991), which is applicable to certain Boeing Model 757 series airplanes, was published in the Federal Register on April 3, 1995 (60 FR 16815). The action proposed to continue to require various inspections and modifications of certain mechanisms of the passenger doors, and replacement of certain parts, if necessary. Additionally, that action proposed to require repetitive inspections to detect worn, damaged, or cracked power assist triggers, repair of worn triggers, and replacement, if necessary; repetitive measurements of the clearance between the lockout cam and the crank stop; and replacement of the lockout cams, if necessary. \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\tTwo commenters request that the FAA include a provision for optional terminating action for the requirement to inspect the emergency power assist triggers, as specified in paragraph (d) of the proposal. One commenter states that repetitive actions should only be necessary if there is significant evidence that doors inspected/rectified in accordance with the alert service bulletin deteriorate with time. This commenter points out that paragraph I.D. of the alert service bulletin (that is referenced in the proposal as the appropriate source of service information) indicates that once the door is rigged correctly, the inspections can be discontinued. A second commenter states that Boeing has indicated that modification of the subject lockout mechanism would terminate the proposed repetitive inspections. \n\n\tThe FAA does not concur. Although the Boeing alert service bulletin would allow termination of the repetitive inspections of the power assist trigger if the lockout cam is within specifiedmeasurements, the FAA finds that the requirement to repetitively inspect the emergency power assist triggers, as required by paragraph (d) of the final rule cannot be terminated. Failure of the lockout cam is not the only possible failure mode that could result in failure of the emergency power assist trigger, e.g., the power assist trigger function could fail in the event of a door mis-sequencing while being opened. \n\n\tTwo commenters request that the FAA include a provision for optional terminating action for the requirement to repetitively measure the clearance between the lockout cam and the crank stop, as specified in paragraph (e), of the proposal. One of the commenters, Boeing, clarifies that the intent of the alert service bulletin is to specify that no further action is necessary if the clearance between the lockout cam and crank stop is within specified limits and the emergency power assist trigger is not damaged or cracked. Boeing indicates that a phrase stating that "if the clearance is within limits, no more work is necessary" was omitted inadvertently from paragraph I.D. of the alert service bulletin. Boeing adds that no further incidents of failure of the emergency power assist triggers have been reported. Therefore, Boeing recommends that the FAA revise paragraphs (e)(1) and (e)(2) of the final rule accordingly. \n\n\tThe FAA concurs with the commenters' requests. The FAA has determined that measurement of the clearance between the lockout cam and the crank stop need not be accomplished on a repetitive basis. The FAA has revised paragraph (e) of the final rule to remove the requirement to measure repetitively. \n\n\tTwo commenters request that the actions specified in Boeing Telex M-7272-94-6665, "New Redesigned Girt Bar Mechanism and Emergency Power Assist (EPA) System," be considered terminating action for the proposed repetitive inspections. The commenters do not justify this request. The FAA does not concur with the commenters' request.The FAA has confirmed with Boeing that the telex referenced by the commenters is an explanation of proposed design changes that may possibly be made in the future. However, these changes could constitute a major redesign to the escape system and may not be offered as a solution for in-service airplanes. The FAA has determined that, since an unsafe condition exists, the inspections must be conducted to ensure continued safety. Furthermore, the FAA does not consider it appropriate to delay this rulemaking action until such time that these design changes are approved and available. \n\n\tThree commenters request that, if repetitive inspections will be required, the FAA extend the repetitive inspection intervals to coincide with regularly scheduled "C" checks (i.e., from the proposed 6 months to 8 months). The FAA does not concur with the commenters' request to extend the compliance time. In developing an appropriate compliance time for this action, the FAA considered the safety implications and the practical aspect of performing the required inspections within an interval of time that parallels normal scheduled maintenance for the majority of affected operators. In consideration of these items, as well as the reports of broken power assist triggers, the FAA has determined that 6 months represents the maximum interval of time allowable wherein the inspections can reasonably be accomplished and an acceptable level of safety can be maintained. However, paragraph (f) of the final rule does provide affected operators the opportunity to apply for an adjustment of the compliance time if data are presented to justify such an adjustment. \n\n\tThe FAA has revised the economic impact information, below, to include cost estimates for accomplishment of the actions required currently by AD 91-07-09. \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 578 Model 757 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 323 airplanes (6 passenger doors per airplane) of U.S. registry will be affected by this AD. \n\n\tThe actions that are currently required by AD 91-07-09 take approximately 51 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact on U.S. operators of the actions currently required by AD 91-07-09 is estimated to be $988,380, or $3,060 per airplane. \n\n\tThe new actions that are required by this new AD will take approximately 12 work hours (2 work hours per passenger door) per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact on U.S. operators of the newrequirements of this AD is estimated to be $232,560, or $720 per airplane ($120 per door), per inspection cycle. \n\n\tShould an operator be required to accomplish the replacement of power assist triggers, it will take approximately 18 work hours per airplane (3 work hours per passenger door) to accomplish the replacement, at an average labor rate of $60 per work hour. Required parts will cost approximately $1,800 per airplane ($300 per passenger door). Based on these figures, the cost impact of the replacement action is estimated to be $2,880 per airplane ($480 per passenger door). \n\n\tThe cost impact figures discussed above are 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 relationship between the national government and the States, oron 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\n List of Subjects in 14 CFR Part 39 \n\n\tAir 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\n PART 39 - AIRWORTHINESS DIRECTIVES \n\n\t1. The 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. Section 39.13 is amended by removing amendment 39-6951 (56 FR 12111, March 22, 1991), and by adding a new airworthiness directive (AD), amendment 39-9445, to read as follows:

The service information referenced in this AD may be obtained from Boeing\nCommercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the Federal Aviation Administration (FAA), Transport Airplane Directorate, Rules Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Roy Boffo, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (206) 227-2780; fax (206) 227-1181.