Airworthiness directives: Boeing,

[Federal Register: October 2, 1998 (Volume 63, Number 191)]

[Proposed Rules]

[Page 52992-52994]

From the Federal Register Online via GPO Access [wais.access.gpo.gov]

[DOCID:fr02oc98-24]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-189-AD]

RIN 2120-AA64

Airworthiness Directives; Boeing Model 737-100, -200, and -200C Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

SUMMARY: This document proposes the supersedure of an existing airworthiness directive (AD), applicable to all Boeing Model 737-100, - 200, and -200C series airplanes, that currently requires periodic inspections to detect missing nuts and/or damaged secondary support hardware adjacent to the aft engine mount, and replacement, if necessary. That AD also provides for optional terminating action for certain inspections and a torque check. This action would mandate accomplishment of the previously optional terminating action. This proposal is prompted by the FAA's determination that the repetitive inspections required by the existing AD may not be providing the degree of safety assurance necessary for the transport airplane fleet. The actions specified by the proposed AD are intended to prevent failure of the secondary support to sustain engine loads in the event of failure of the aft engine mount cone bolt, which could result in the separation of the engine from the wing.

DATES: Comments must be received by November 16, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 98-NM-189-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: Greg Schneider, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2028; fax (425) 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

[[Page 52993]]

proposal will be filedin 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 98-NM-189-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-114, Attention: Rules Docket No. 98-NM-189-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

On April 4, 1994, the FAA issued AD 91-09-14 R1, amendment 39-8876 (59 FR 18294, April 18, 1994), applicable to all Boeing Model 737-100, -200, and -200C series airplanes, to require periodic inspections to detect missing nuts and/or damaged secondary support hardware adjacent to the aft engine mount, and replacement, if necessary. That AD also provides for optional installation of a new, modified support, which would constitute terminating action for certain inspections and a torque check. That action was prompted by the development of a modification that will prevent wearing of the secondary support. The requirements of that AD are intended to prevent failure of the secondary support to sustain engine loads in the event of failure of the aft engine mount cone bolt, which could result in the separation of the engine from the wing.

Actions Since Issuance of Previous Rule

Since the issuance of AD 91-09-14 R1, Boeing has informed the FAA that, based on testing conducted by Boeing, significant cracks of the aft engine mount cone bolts may not be detected using the current ultrasonic inspection procedures. There have been two occurrences of failure of aft engine mount cone bolts after the bolts had been subjected to ultrasonic inspections. In light of this information, the FAA has determined that the repetitive inspections required by the existing AD may not be providing the degree of safety assurance necessary for the fleet of Boeing Model 737-100, -200, and -200C series airplanes.

Explanation of Relevant Service Information

The FAA previously reviewed and approved Boeing Service Bulletin 737-71-1289, dated August 19, 1993. That service bulletin describes procedures for replacement of the existing secondary support with a new, improved secondary support. Since the issuance of AD 91-09-14 R1, the FAA has reviewed and approved Boeing Notices of Status Change (NSC) 737-71-1289 NSC 1, dated September 2, 1993; 737-71-1289 NSC 2, dated January 26, 1995; and 737-71-1289 NSC 03, dated October 3, 1996. These NSC's contain certain minor editorial changes to the service bulletin.

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 supersede AD 91-09-14 R1, to continue to require periodic inspections to detect missing nuts and/or damaged secondary support hardware, and replacement, if necessary. The proposed AD would require accomplishment of the previously optional terminating action, which, when accomplished, would constitute terminating action for certain inspections and for a torque check required by this AD.

Cost Impact

There are approximately 1,045 airplanes of the affected design in the worldwide fleet. The FAA estimates that 382 airplanes of U.S. registry would be affected by this proposed AD.

The inspections that are currently required by AD 91-09-14 R1 take approximately 3 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the currently required actions on U.S. operators is estimated to be $68,760, or $180 per airplane, per inspection cycle.

The replacement that is proposed in this AD would take approximately 60 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts would cost approximately $7,000 per airplane. Based on these figures, the cost impact of the replacement proposed by this AD on U.S. operators is estimated to be $4,049,200, or $10,600 per airplane.

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the current or 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 removing amendment 39-8876 (59 FR 18294, April 18, 1994), and by adding a new airworthiness directive (AD), to read as follows:

   Boeing: Docket 98-NM-189-AD. Supersedes AD 91-09-14 R1, amendment 39-8876.

   Applicability: All Model 737-100, -200, and -200C series airplanes; certificated in any category.

   Note 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 request approval for an alternative method of compliance in accordance with paragraph (d)(1) of this AD. The request should include an assessment of

   [[Page 52994]]

   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 failure of the secondary support to sustain engine loads in the event of failure of the aft engine mount cone bolt, which could result in the separation of the engine from the wing, accomplish the following:

   (a) Within the next 45 landings after May 20, 1991 (the effective date of AD 91-09-14, amendment 39-6972), accomplish the following:

   (1) Inspect the aft mount cone bolt indicator for proper alignment. Improper alignment indicates a broken aft cone bolt. Broken cone bolts must be replaced, prior to further flight, with bolts that have been inspected in accordance with Boeing Alert Service Bulletin 737-71A1212, dated December 22, 1987, using magnetic particle inspection techniques. Repeat the inspection of the indicator at intervals thereafter not to exceed 45 landings.

   (2) Unless previously accomplished within the last 255 landings, inspect the aft mount cone bolt improved secondary support for missing nuts, evidence of bolt wear, and disbonded honeycomb core; in accordance with Boeing Service Bulletin 737-71-1250, dated June 14, 1990. Except as provided in paragraph (b) of this AD, missing nuts, bolts worn outside the limits specified in the service bulletin, or disbonded honeycomb core must be replaced, prior to further flight, with new or repaired identical parts. Repeat the inspection at intervals not to exceed 300 landings.

   (b) Perform the following inspections if discrepant hardware is found during the inspections required by paragraph (a)(2) of this AD, and replacement hardware is not immediately available:

   (1) Prior to further flight, and thereafter at intervals not to exceed 300 landings, inspect for cracks in the aft engine mount cone bolt, in accordance with Boeing Alert Service Bulletin 737-71A1212, dated December 22, 1987, using ultrasonic inspection techniques. Replace cracked cone bolts, prior to further flight, with bolts that have been inspected in accordance with the service bulletin, using magnetic particle inspection techniques. Replacement (newly installed) cone bolts must be ultrasonically inspected for internal cracking in accordance with the provisions of this paragraph at intervals not to exceed 300 landings.

   (2) At the next ultrasonic inspection, as required by paragraph (b)(1) of this AD, unless previously accomplished within 150 to 300 landings after cone bolt installation, accomplish a torque check to verify that the cone bolt is torqued to the proper torque limit specified in the appropriate Boeing maintenance manual. This check is to be accomplished without loosening the bolt. After each cone bolt installation, accomplish the torque check procedure required by this paragraph between 150 landings and 300 landings following installation. Replacement of discrepant hardware in accordance with paragraph (a)(2) of this AD constitutes terminating action for the requirements of this paragraph.

   (i) If the cone bolt torque is below one-half the specified torque, prior to further flight, remove the cone bolt and replace it with a serviceable bolt.

   (ii) If the cone bolt torque is equal to, or above one-half the specified torque, but below the specified torque, re-torque to the specified level and re-check the torque within the next 150 to 300 landings. If, at that time, the torque is below 90 percent of the specified torque, replace the cone bolt with a serviceable bolt.

   (c) At next engine removal, or within 8,000 flight hours after the effective date of this AD, whichever occurs first, replace the secondary support of the aft engine mount with a new, improved secondary support, Kit Number 65C37057-1; in accordance with Boeing Service Bulletin 737-71-1289, dated August 19, 1993; as revised by Notices of Status Change 737-71-1289 NSC 1, dated September 2, 1993, 737-71-1289 NSC 2, dated January 26, 1995, and 737-71-1289 NSC 03, dated October 3, 1996. Accomplishment of such replacement constitutes terminating action for the repetitive inspection requirements of paragraphs (a)(2) and (b)(1) of this AD, and for the torque check requirement of paragraph (b)(2) of this AD.

   (d)(1) 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.

   (d)(2) Alternative methods of compliance, approved previously in accordance with AD 91-09-14 R1, amendment 39-8876, are approved as alternative methods of compliance with paragraph (a)(1) of this AD.

   Note 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.

   (e) 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 25, 1998. Darrell M. Pederson, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

   [FR Doc. 98-26354Filed10-1-98; 8:45 am]

   BILLING CODE 4910-13-U