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

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Final rule.

SUMMARY:

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 737-100 and -200 series airplanes, that currently requires inspections to detect cracking of the support fittings of the Krueger flap actuator; and, if necessary, replacement of existing fittings with new steel fittings and modification of the aft attachment of the actuator. That AD also provides for an optional terminating modification that constitutes terminating action for the repetitive inspections. This amendment requires accomplishment of the previously optional terminating action. This amendment is prompted by reports of cracking due to fatigue and stress corrosion of the support fittings of the Krueger flap actuator. The actions specified by this AD are intended to prevent such cracking, which could result in fracturing of the actuator attach lugs, separation of the actuator from the support fitting, severing of the hydraulic lines, and resultant loss of hydraulic fluids. These conditions, if not corrected, could result in possible failure of one or more hydraulic systems, and consequent reduced controllability of the airplane.

DATES:

Effective September 12, 2000.

The incorporation by reference of Boeing Service Bulletin 737-57-1129, Revision 2, dated May 28, 1998, is approved by the Director of the Federal Register as of September 12, 2000.

The incorporation by reference of Boeing Service Bulletin 737-57-1129, Revision 1, dated October 30, 1981; as revised by Notice of Status Change 737-57-1129 NSC 1, dated July 23, 1982; Notice of Status Change 737-57-1129 NSC 2, dated April 14, 1983; and Notice of Status Change 737-57-1129 NSC 3, dated May 18, 1995; as listed in the regulations; was approved previously by the Director of the Federal Register as of September 17, 1996 (61 FR 41957, August 13, 1996).

ADDRESSES:

The service information referenced in this AD may be obtained from Boeing Commercial 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.

FOR FURTHER INFORMATION CONTACT:

Nancy Marsh, 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:

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 96-17-04, amendment 39-9712 (61 FR 41957, August 13, 1996), which is applicable to certain Boeing Model 737-100 and -200 series airplanes, was published in the Federal Register on March 15, 2000 (65 FR 13919). The action proposed to continue to require inspections to detect cracking of the support fittings of the Krueger flap actuator on each wing; and to mandate replacement of any existing aluminum fitting with a new steel fitting and modification of the actuator aft attachment.

Comments

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.

Support for the Proposed Rule

One commenter states that it has no objection to the proposed rule.

Request for Credit for Work Accomplished Previously

One commenter requests that the proposed AD be revised to provide credit for accomplishment of the terminating modification per Boeing Service Bulletin 737-57-1129, Revision 1, dated October 30, 1981; as revised by Notices of Status Change 737-57-1129 NSC 1, dated July 23, 1982; 737-57-1129 NSC 2, dated April 14, 1983; or 737-57-1129 NSC 3, dated May 18, 1995. The commenter states that it has previously accomplished the terminating modification in accordance with Revision 1 of the service bulletin.

The FAA concurs with the intent of the commenter's request. However, the FAA points out that “Note 2” of this AD already provides such credit for accomplishment of the terminating modification prior to the effective date of this AD in accordance with Boeing Service Bulletin 737-57-1129, Revision 1, as revised by Notices of Status Change 737-57-1129 NSC 1, 737-57-1129 NSC 2, and 737-57-1129 NSC 3. Therefore, no change to the final rule is necessary.

Request To Extend Use of Aluminum Support Fittings

One commenter questions the FAA's rationale for prohibiting installation of new or serviceable aluminum support fittings as of the effective date of this AD, as provided by paragraph (c) of the proposed rule. The commenter states that gradually phasing out the use of aluminum fittings over the five-year compliance time allowed by paragraph (b) of the proposed AD would provide “an equivalent level of safety.”

The commenter states no justification for its request, and the FAA does not concur with the commenter's request. The FAA's decision to prohibit installation of aluminum support fittings, as required by this AD, is based on the unsatisfactory service history of these parts. Because of the criticality of the unsafe condition addressed in this AD, the FAA finds that it would be inappropriate to continue to allow replacement of existing aluminum fittings with new or serviceable aluminum support fittings after the effective date of this AD. In addition, the FAA notes that paragraph (c) of AD 96-17-04 prohibits installation of aluminum support fittings of four part numbers as of September 17, 1996 (the effective date of that AD). This AD adds four more part numbers of aluminum support fittings to the list of those that cannot be installed after the effective date of this AD. No change to the final rule is necessary.

Conclusion

After 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 as proposed.

Cost Impact

There are approximately 727 Model 737-100 and -200 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 270 airplanes of U.S. registry will be affected by this AD.

The inspections that are currently required by AD 96-17-04 and retained in this AD take approximately 12 work hours per airplane (6 work hours per wing) to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the currently required inspections on U.S. operators is estimated to be $194,400, or $720 per airplane, per inspection.

The replacement and modification required by this AD will take approximately 88 work hours per airplane (44 work hours per wing) to accomplish, at an average labor rate of $60 per work hour. Required parts will cost approximately $12,226 per airplane. Based on these figures, the cost impact of the replacement and modification required by this AD on U.S. operators is estimated to be $4,726,620, or $17,506 per airplane.

The 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.

Regulatory Impact

The regulations adopted herein will not have a substantial direct effect 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, it is determined that this final rule does not have federalism implications under Executive Order 13132.

For 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.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Incorporation by reference
• Safety

Adoption of the Amendment

Accordingly, 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:

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.

2. Section 39.13 is amended by removing amendment 39-9712 ( 61 FR 41957, August 13, 1996), and by adding a new airworthiness directive (AD), amendment 39-11851, to read as follows:

2000-15-18 Boeing: Amendment 39-11851. Docket 99-NM-320-AD. Supersedes AD 96-17-04, Amendment 39-9712.

Applicability: Model 737-100 and -200 series airplanes, line numbers 001 through 813 inclusive, 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) 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.

Compliance: Required as indicated, unless accomplished previously.

To prevent possible failure of one or more hydraulic systems and consequent reduced controllability of the airplane, accomplish the following:

Restatement of Requirements of AD 96-17-04

Repetitive Inspections

(a) Within one year after September 17, 1996 (the effective date of AD 96-17-04, amendment 39-9712), perform an eddy current inspection to detect cracking of the support fitting of the Krueger flap actuator on each wing, in accordance with Boeing Service Bulletin 737-57-1129, Revision 1, dated October 30, 1981; as revised by Notices of Status Change 737-57-1129 NSC 1, dated July 23, 1982; 737-57-1129 NSC 2, dated April 14, 1983; and 737-57-1129 NSC 3, dated May 18, 1995; or Revision 2, dated May 28, 1998.

(1) If no cracking is detected, repeat the inspection required by paragraph (a) of this AD thereafter at intervals not to exceed 3,000 hours time-in-service.

(2) If any cracking is detected, prior to further flight, accomplish the replacement and modification specified in paragraph (b) of this AD.

New Requirements of This AD:

Terminating Action

(b) Within 5 years after the effective date of this AD: Replace any existing aluminum support fitting of the Krueger flap actuator on each wing with a steel fitting, and modify the actuator aft attachment, in accordance with Boeing Service Bulletin 737-57-1129, Revision 2, dated May 28, 1998. Accomplishment of this replacement and modification constitutes terminating action for the repetitive inspections required by paragraph (a) of this AD.

Note 2:

Replacement of the existing aluminum support fitting of the Krueger flap actuator on each wing with a steel fitting, and modification of the actuator aft attachment, prior to the effective date of this AD, in accordance with Boeing Service Bulletin 737-57-1129, Revision 1, dated October 30, 1981; as revised by Notices of Status Change 737-57-1129 NSC 1, dated July 23, 1982; 737-57-1129 NSC 2, dated April 14, 1983; and 737-57-1129 NSC 3, dated May 18, 1995; is considered acceptable for compliance with the modification required by paragraph (b) of this AD.

Spares

(c) As of the effective date of this AD, no person shall install on any airplane any aluminum support fitting identified in the “Existing Part Number” column of Paragraph 2.D. of Boeing Service Bulletin 737-57-1129, Revision 2, dated May 28, 1998.

Alternative Methods of Compliance

(d) 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.

Note 3:

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

Special Flight Permits

(e) Special flight permits may be issued in accordance with §§ 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.

Incorporation by Reference

(f) The actions shall be done in accordance with Boeing Service Bulletin 737-57-1129, Revision 1, dated October 30, 1981; as revised by Notice of Status Change 737-57-1129 NSC 1, dated July 23, 1982; Notice of Status Change 737-57-1129 NSC 2, dated April 14, 1983; and Notice of Status Change 737-57-1129 NSC 3, dated May 18, 1995; or Boeing Service Bulletin 737-57-1129, Revision 2, dated May 28, 1998; as applicable.

(1) The incorporation by reference of Boeing Service Bulletin 737-57-1129, Revision 2, dated May 28, 1998, is approved by the Director of the Federal Register, in accordance with 5 U.S.C. 552(a) and 1 CFR part 51.

(2) The incorporation by reference of Boeing Service Bulletin 737-57-1129, Revision 1, dated October 30, 1981; as revised by Notice of Status Change 737-57-1129 NSC 1, dated July 23, 1982; Notice of Status Change 737-57-1129 NSC 2, dated April 14, 1983; and Notice of Status Change 737-57-1129 NSC 3, dated May 18, 1995; was approved previously by the Director of the Federal Register as of September 17, 1996 (61 FR 41957, August 13, 1996).

(3) 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 the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Effective Date

(g) This amendment becomes effective on September 12, 2000.