00-5890. Airworthiness Directives; Boeing Model 737 Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Final rule.

SUMMARY:

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 737 series airplanes, that requires a one-time inspection of the main landing gear (MLG) axle flange to detect cracking, and follow-on corrective actions. For certain airplanes, this amendment also requires replacement of the original brake mounting gasket with a more durable aluminum-nickel-bronze gasket, and installation of new shear studs, if necessary. For certain airplanes, this amendment requires modification of the mounting flange holes of the brake torque tube. This amendment is prompted by reports of cracking in the axle flange and by reports of deterioration of the brake mounting gasket. The actions specified by this AD are intended to prevent fracture of the MLG axle and separation of the wheel from the MLG, and consequent reduced controllability of the airplane.

DATES:

Effective April 19, 2000.

The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of April 19, 2000.

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:

Rick Kawaguchi, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Boeing Model 737 series airplanes was published in the Federal Register on October 29, 1998 (63 FR 57953). That action proposed to require a one-time inspection of the main landing gear (MLG) axle flange to detect cracking, and follow-on corrective actions. For certain airplanes, that action proposed to require replacement of the original brake mounting gasket with a more durable aluminum-nickel-bronze gasket, and installation of new shear studs, if necessary. For certain airplanes, that action proposed to require modification of the mounting flange holes of the brake torque tube.

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 Proposal

One commenter supports the proposed rule.

Requests to Extend Compliance Time

Several commenters request that the FAA extend the compliance time (i.e., within 200 days or 1,500 flight cycles after the effective date of this AD, whichever occurs later) for accomplishing the requirements of the proposed AD.

One commenter states that the proposed AD should be carried out within 250 days or 2,500 aircraft cycles, whichever occurs later. The commenter supports this request by stating that its standard practice is to clean and visually inspect all landing gear axle flanges each time the brake assemblies and wheel assemblies are removed from the axle. The commenter further states that it has never experienced loss of a MLG wheel with BFGoodrich brake assemblies, and that BFGoodrich is not aware of the loss of a wheel on aircraft equipped with BFGoodrich brake assemblies.

Another commenter, the airplane manufacturer, states that the inspection of axle flanges that have been repaired with nickel sulfamate or bushings would require removal of the repair. The commenter notes that this will have a significant impact on the cost and time required to perform the proposed inspection. Therefore, consideration should be given to increasing the compliance time or modifying the inspection requirements.

One commenter states that the inspection schedule specified in paragraphs (b) and (c) of the proposed AD should be increased to at least 1 year or 4,000 cycles, whichever is later. The commenter states that the currently proposed inspection schedule for most of the operators will fall during a line maintenance check. The commenter points out that the inspection and repair specified in Boeing All Operators Telex (AOT) M-7272-96-1442, dated March 29, 1996 [which is referenced in the proposed AD the appropriate source for accomplishing the proposed inspection in paragraphs (b)(1) and (c)(1) and the proposed repair in paragraphs (b)(2) and (c)(2)], involves repairs that should be accomplished at a heavy check or overhaul facility.

One commenter states that the inspection should be accomplished during a heavy maintenance visit where equipment and trained personnel are more readily available.

The FAA concurs with the commenters' requests. The FAA concurs that the magnetic particle inspection, high frequency eddy current (HFEC) inspection, modification, and repair, if necessary, required by this AD should be accomplished at an overhaul facility. The FAA has determined that an extension of the compliance time to within 1 year or 4,500 flight cycles after the effective date of this AD, whichever occurs later, will not compromise safety provided that an interim detailed visual inspection to detect fretting and corrosion of the axle flange bolt holes is accomplished within 200 days or 1,500 flight cycles after the effective date of this AD, whichever occurs later. The FAA has added a new paragraph (d) to the final rule to include such an option. The FAA also has added a note to the final rule to clarify the definition of the detailed visual inspection.

One commenter states that, if the FAA mandates modifications to the ten or eleven bolt configuration, it requests that the compliance time for paragraph (c) of the proposed AD be extended to 5 years. (This comment is discussed in more detail below under the heading “Requests to Exclude Actions on the Basis of Configuration”).

The FAA does not concur with the commenter's request. Although the two stud/ten bolt configuration provides better clamp-up between the brake assembly and the MLG axle flange, the FAA has determined that improved clamp-up by itself does not justify a 5-year compliance time.

Requests to Exclude Actions on the Basis of Configuration

One commenter requests that operators utilizing ten or eleven bolt configurations regardless of gasket material not be subject to the requirements of the proposed AD. One commenter states that, according to Boeing AOT M-7272-96-1442, dated March 29, 1996, previous failures are primarily due to poor maintenance of finish, improper plating repairs, and installation of incorrect wheel bearings, rather than design deficiencies. The commenter suggests that no evidence exists which shows that a ten or eleven bolt brake mounting configuration with phenolic gaskets is unsafe or susceptible to cracking, and subsequent axle failure.

The FAA does not concur with the commenter's request. Although the two stud/ten bolt configuration provides better clamp-up between the brake assembly and the MLG axle flange, the FAA has determined that an improved clamp-up by itself will not prevent fretting. Furthermore, Boeing AOT M-7272-96-1442 lists deterioration of the phenolic gasket as another of the basic causes of reported axle fractures. Brake heat and vibration can lead to deterioration of the phenolic gasket. The FAA finds that an increase in clamp-up with the two stud/ten bolt configuration will help decrease the magnitude of vibration, but will not alleviate the gasket deterioration brake heat caused by the gasket. The FAA has determined that the aluminum-nickel-bronze (Al-Ni-Br) gasket used in conjunction with brake mounting hardware, which includes two studs and ten bolts, will ensure proper clamp-up and resistance to brake heat and vibration.

Another commenter requests that operators with a one stud/eleven bolt brake mounting configuration be required to add one stud and one nickel bronze gasket to comply with the intent of the proposed rule. No justification was provided.

The FAA does not concur with the commenter's request. The FAA has determined that the existing shear studs used with the phenolic gasket will not properly mate with the aluminum-nickel-bronze gasket. Therefore, two new studs will be required. Furthermore, prior to installing the gasket, magnetic particle or HFEC inspections are required to evaluate the existing integrity of the axle flange and bolt holes.

Requests for Credit for Previous Incorporation of Certain Service Information

One commenter requests that the FAA give credit for airplanes on which MLG assemblies with an Al-Ni-Br gasket have been installed in accordance with Boeing Service Bulletin 737-32-1253, and that have been inspected/reworked/overhauled in accordance with Boeing AOT M-7272-96-1442 and/or original equipment manufacturer/FAA-approved operator designed rework procedures.

The FAA concurs with the commenter's request provided that the inspection has been accomplished concurrent with or after installation of the Al-Ni-Br gasket. The FAA has determined that accomplishment of the magnetic particle or HFEC inspections in accordance with Boeing AOT M-7272-96-1442, dated March 29, 1996, concurrent with or after installation of an aluminum-nickel-bronze gasket and shear studs, is considered acceptable for compliance with the requirements of paragraphs (a)(1) and (c)(1) of this final rule. Therefore, the FAA has added a new note after paragraph (a) of this AD to provide credit for accomplishing the required inspection concurrently with or after accomplishment of the subject installation.

Two commenters request that the inspection required by paragraph (a)(1) of the proposed AD be deleted. One of these commenters requests that the inspection required by paragraph (b)(1) also be deleted. One commenter states that the inspection should not be required because a new aluminum-nickel-bronze gasket has been installed in accordance with Boeing Service Bulletin 737-32-1253, dated November 7, 1991, and the torque tube mounting holes on the mounting flange have been modified in accordance with AlliedSignal Service Bulletin 2601042-32-003, dated March 15, 1997. If operators installed this new gasket along with the modification on the axle flange and brake flange, the commenter contends that they have already accomplished the initial inspection in accordance with Boeing Service Bulletin 737-32-1253. One commenter states that there have been no reported axle failures on airplanes that have incorporated Boeing Service Bulletin 737-32-1253. The commenter further states that the inspection of these airplanes will impose an unreasonable financial burden on the operators.

Another commenter states that paragraph (c) of the proposed AD contains no requirement for repetitive inspections after incorporation of Boeing Service Bulletin 737-32-1253. Therefore, the commenter requests that no further action be required, if the magnetic particle inspection and modification specified in that service bulletin were already accomplished during the previous landing gear overhaul or at a maintenance opportunity.

Another commenter requests that, if an MLG has been inspected, overhauled, and modified in accordance with Boeing Service Bulletins 737-32-1253, dated November 7, 1991, and 737-32-1235, dated April 12, 1990, affected airplanes should not be subject to the requirements of the proposed AD. The commenter also states that In Service Report (ISR) #95-03-3210-20, dated February 16, 1995, states that incorporation of these service bulletins is the recommended action according to Boeing.

The FAA does not concur with the commenters' requests. The FAA has determined that, for airplanes on which the installation of the brake mounting hardware in accordance with Boeing Service Bulletin 737-32-1253, dated November 7, 1991, and Boeing Service Bulletin 737-32-1235, dated April 12, 1990, has been accomplished, the magnetic particle or HFEC inspection required by this AD must be accomplished because these service bulletins do not contain inspection procedures. These service bulletins only describe procedures for installing the improved brake mounting hardware and an additional shear stud. The FAA points out that there is a possibility that some of the aluminum-nickel-bronze gaskets could have been installed on axle flanges that already had cracks or fretting damage. A magnetic particle or HFEC inspection of this area will ensure detection of cracks in the axle flange and brake attach bolt holes.

One commenter further requests that airplanes on which the shear stud replacement in accordance with Boeing Service Bulletin 737-32-1253 has been incorporated not be required to install new studs, as required in paragraph (a)(4) of the proposed AD. The commenter believes this to be unnecessary since Service Bulletin 737-32-1253 already requires replacement of the shear studs.

The FAA concurs with the commenter's request. The FAA finds that accomplishment of the gasket replacement in accordance with the subject service bulletin includes replacing the shear studs. The FAA notes that paragraph (a) of the AD applies to certain airplanes “on which the original gaskets have been replaced with aluminum-nickel-bronze gaskets in accordance with Boeing Service Bulletin 737-32-1253, dated November 7, 1991.” The FAA finds it unnecessary for those airplanes to accomplish the replacement of the shear studs a second time. Therefore, the FAA has deleted paragraph (a)(4) of the proposed AD from the final rule.

Requests to Allow Flight with Cracks

Two commenters request that repair of cracks, prior to further flight, as required by paragraphs (a)(1), (b)(1), and (c)(1) of the proposed AD, apply only to those axle flange cracks found progressing inward from the brake attach holes towards the MLG axle. The commenters suggest that operations should be allowed to continue on airplanes with axle flanges that have cracks on up to four bolt holes, as long as they progress towards the outer edge of the flange. One of the commenters states that this type of cracking is sufficiently covered under the current Boeing Overhaul Manual 32-11-11. One commenter further states that if repair is deemed necessary, then the FAA should develop and include an approved repair scheme in the final rule.

The FAA partially concurs with the commenter's request. The FAA does not concur that operations should be allowed to continue on airplanes with axle flanges that have any crack. While outwardly progressing cracks should not affect axle integrity, if such cracks are completely ignored, they could change direction and begin progressing inwards towards the MLG axle. Therefore, the FAA has determined that any subject axle flange that is found to be cracked must be repaired prior to further flight in accordance with a method approved by the FAA.

However, the FAA does concur that accomplishment of the repair in accordance with Boeing Overhaul Manual 32-11-11 is considered acceptable for compliance with the repair requirements of paragraphs (a)(1), (b)(1), and (c)(1) of the AD. Therefore, the FAA has revised the final rule to include as new note to clarify this point. In addition, operators may request approval of an alternative method of compliance if data are provided to substantiate that such a method would provide an acceptable level of safety.

Request to Change Terminology

Two commenters request that the term “brake assemblies” in paragraphs (b)(4) and (c)(3) of the proposed AD be changed. One commenter suggests “brake mounting hardware,” and the other commenter suggests “axle flange assemblies” as alternative terms.

One commenter further suggests that the term “torque tube” be changed to “brake torque tube” in paragraphs (a)(3) and (b)(3) of the proposed AD; delete “on the mounting flange” from paragraph (a)(3) of the proposed AD; and change “brake modification” to “brake mounting hardware modification” in the Cost Impact section of the proposed AD.

The FAA concurs with the commenters' requests. The FAA has revised paragraphs (b)(4) and (c)(3) of the final rule to read “brake mounting hardware.” The FAA also has revised the term “torque tube” to “brake torque tube” in the Summary, Supplementary Information, and Cost Impact sections of the AD; and deleted the phrase “of the mounting flange” from paragraph (b)(3) of this AD to be consistent with the changes noted previously.

Other Changes Made to the Proposed AD

The FAA inadvertently omitted information from paragraphs (b)(1) and (c)(1) of the proposed rule for HFEC inspections of axle flanges that have not been repaired previously and coated with a nickel sulfamate finish. As stated in paragraph (a)(1) of the proposed rule, an HFEC inspection may only be accomplished if the axle flange has not been repaired previously and coated with a nickel sulfamate finish. However, the FAA inadvertently omitted this clarification in paragraphs (b)(1) and (c)(1) of the proposed AD, which applies to airplanes equipped with certain AlliedSignal brake assemblies on which the original gaskets have not been replaced and on all other affected airplanes, respectively. The clarification regarding HFEC inspections applies to all repaired axle flanges, independent of gasket replacement and independent of whether the airplanes are equipped with certain AlligedSignal brake assemblies. Therefore, the FAA has revised paragraphs (b)(1) and (c)(1) of the final rule to include the clarification that an HFEC inspection is not appropriate for repaired axle flanges.

As published, the NPRM contains a typographical error in paragraph (a)(1). It references Boeing All Operators Telex (AOT) “M-7272-76-1442,” dated “Mach 29, 1996,” as the appropriate source of service information for accomplishment of the magnetic particle or HFEC inspection. However, as indicated throughout the rest of the proposed AD, the correct reference is “Boeing All Operators Telex (AOT) “M-7272-96-1442, dated March 29, 1996.”

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 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.

Cost Impact

There are approximately 2,015 airplanes of the affected design in the worldwide fleet. The FAA estimates that 893 airplanes of U.S. registry will be affected by this AD.

The FAA estimates that it will take approximately 4 work hours per airplane to accomplish the required inspection, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the inspection required by this AD on U.S. operators is estimated to be $214,320, or $240 per airplane.

It will take approximately 32 work hours per airplane at an average labor rate of $60 per work hour should an operator be required to accomplish the required brake mounting hardware modification. Required parts will cost approximately $2,052 per airplane. Based on these figures, the cost impact of the brake mounting hardware modification required by this AD on U.S. operators is estimated to be $3,972 per airplane.

Additionally, the FAA estimates that it will take approximately 5 work hours per airplane to accomplish the required brake torque tube modification, and that the average labor rate is $60 per work hour. The FAA estimates that this action will be required to be accomplished on approximately 400 U.S.-registered airplanes. Based on these figures, the cost impact of this modification required by this AD on U.S. operators is estimated to be $120,000, or $300 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 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.

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 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.

§ 39.13

[Amended]

2. Section 39.13 is amended by adding the following new airworthiness directive:

2000-05-13-Boeing: Amendment 39-11623. Docket 98-NM-57-AD.

Applicability: Model 737-100, -200, -300, -400, and -500 series airplanes; line positions 1 through 2135 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 (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.

Compliance: Required as indicated, unless accomplished previously.

To prevent fracture of the main landing gear (MLG) axle and the separation of the wheel from the MLG, and consequent reduced controllability of the airplane, accomplish the following:

Inspection, Modification, and Corrective Action

(a) For Model 737-100 and -200 series airplanes equipped with AlliedSignal (ALS/Bendix) brake assembly installations having Boeing part numbers (P/N) 10-61063-14, -18, or -21, on which the original gaskets have been replaced with aluminum-nickel-bronze gaskets in accordance with Boeing Service Bulletin 737-32-1253, dated November 7, 1991: Except as provided by paragraph (d) of this AD, within 200 days or 1,500 flight cycles after the effective date of this AD, whichever occurs later, accomplish the requirements of paragraphs (a)(1), (a)(2), and (a)(3) of this AD.

(1) Perform either a one-time magnetic particle inspection or a one-time high frequency eddy current inspection of the MLG axle flange to detect cracking, except that a high frequency eddy current inspection may only be accomplished if the axle flange has not been repaired previously and coated with a nickel sulfamate finish. The magnetic particle inspection or high frequency eddy current inspection is to be accomplished in accordance with procedures specified in paragraph B. of the “Recommended Operator Action” section of Boeing All Operators Telex (AOT) M-7272-96-1442, dated March 29, 1996. If any cracking is detected, prior to further flight, repair the MLG flange, in accordance with Boeing Overhaul Manual 32-11-11, or other method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate.

(2) If any corrosion or fretting is found during accomplishment of the inspection required by paragraph (a)(1) of this AD: Prior to further flight, accomplish the repair procedures specified in the “Recommended Operator Action” section of Boeing AOT M-7272-96-1442, dated March 29, 1996.

(3) Accomplish the modification of the brake torque tube mounting holes, in accordance with AlliedSignal Service Bulletin 2601042-32-003, dated March 15, 1997.

Inspection, Modification, and Corrective Action

(b) For Model 737-100 and -200 series airplanes equipped with AlliedSignal (ALS/Bendix) brake assembly installations having Boeing P/N 10-61063-14, -18, or -21, on which the original gaskets have not been replaced with new aluminum-nickel-bronze gaskets in accordance with Boeing Service Bulletin 737-32-1253, dated November 7, 1991: Except as provided by paragraph (d) of this AD, within 200 days or 1,500 flight cycles after the effective date of this AD, whichever occurs later, accomplish the requirements of paragraphs (b)(1), (b)(2), (b)(3), and (b)(4) of this AD.

(1) Perform either a one-time magnetic particle inspection or a one-time high frequency eddy current inspection of the MLG axle flange to detect cracking, except that a high frequency eddy current inspection may only be accomplished if the axle flange has not been repaired previously and coated with a nickel sulfamate finish. The magnetic particle inspection or high frequency eddy current inspection is to be accomplished in accordance with procedures specified in paragraph B. of the “Recommended Operator Action” section of Boeing AOT M-7272-96-1442, dated March 29, 1996. If any cracking is detected, prior to further flight, repair the MLG flange, in accordance with Boeing Overhaul Manual 32-11-11, or other method approved by the Manager, Seattle ACO.

(2) If any corrosion or fretting is found during accomplishment of the inspection required by paragraph (b)(1) of this AD: Prior to further flight, accomplish the repair procedures specified in the “Recommended Operator Action” section of Boeing AOT M-7272-96-1442, dated March 29, 1996.

(3) Accomplish the modification of the brake torque tube mounting holes, in accordance with AlliedSignal Service Bulletin 2601042-32-003, dated March 15, 1997.

(4) Accomplish the modification of the affected brake mounting hardware in accordance with Boeing Service Bulletin 737-32-1253, dated November 7, 1991.

Inspection, Modification, and Corrective Action

(c) For Model 737-100, -200, -300, -400, and -500 series airplanes other than those identified in paragraphs (a) and (b) of this AD: Except as provided by paragraph (d) of this AD, within 200 days or 1,500 flight cycles after the effective date of this AD, whichever occurs later, accomplish the requirements of paragraphs (c)(1), (c)(2), and (c)(3) of this AD.

(1) Perform either a one-time magnetic particle inspection or a one-time high frequency eddy current inspection of the MLG axle flange to detect cracking, except that a high frequency eddy current inspection may only be accomplished if the axle flange has not been repaired previously and coated with a nickel sulfamate finish. The magnetic particle inspection or high frequency eddy current inspection is to be accomplished in accordance with procedures specified in paragraph B. of the “Recommended Operator Action” section of Boeing AOT M-7272-96-1442, dated March 29, 1996. If any cracking is detected, prior to further flight, repair the MLG flange, in accordance with Boeing Overhaul Manual 32-11-11, or other method approved by the Manager, Seattle ACO.

(2) If any corrosion or fretting is found during accomplishment of the inspection required by paragraph (c)(1) of this AD: Prior to further flight, accomplish the repair procedures specified in the “Recommended Operator Action” section of Boeing AOT M-7272-96-1442, dated March 29, 1996.

(3) Accomplish the modification of the affected brake mounting hardware in accordance with Boeing Service Bulletin 737-32-1253, dated November 7, 1991.

Note 2:

Accomplishment of the magnetic particle or HFEC inspections of unrepaired axle flanges in accordance with Boeing Telex M-7272-96-1442, dated March 29, 1996, concurrent with or after installation of an aluminum-nickel-bronze gasket and shear studs, is considered acceptable for compliance with the requirements of paragraphs (a)(1) and (c)(1) of this AD.

Optional Visual Inspection

(d) The actions required by paragraphs (a), (b), and (c) of this AD may be accomplished at the time specified in paragraph (d)(1) of this AD, provided that the action specified in paragraph (d)(2) is accomplished.

(1) Within 1 year or 4,500 flight cycles after the effective date of this AD, whichever occurs later, accomplish the actions specified in paragraph (a), (b), or (c) of this AD, as applicable; and

(2) Within 200 days or 1,500 flight cycles after the effective date of this AD, whichever occurs later, perform a detailed visual inspection to detect fretting or corrosion of the axle flange bolt holes. If any fretting or corrosion is detected, prior to further flight, accomplish the repair procedures specified in the “Recommended Operator Action” section of Boeing AOT M-7272-96-1442, dated March 29, 1996.

Note 3:

For the purposes of this AD, a detailed inspection is defined as: “An intensive visual examination of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses, etc., may be used. Surface cleaning and elaborate access procedures may be required.”

Alternative Methods of Compliance

(e) 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 ACO. 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 4:

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

(f) 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

(g) Except as provided by paragraphs (a)(1), (b)(1), and (c)(1) of this AD, the actions shall be done in accordance with Boeing All Operators Telex (AOT) M-7272-96-1442, dated March 29, 1996; AlliedSignal Service Bulletin 2601042-32-003, dated March 15, 1997; and Boeing Service Bulletin 737-32-1253, dated November 7, 1991; as applicable. 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 the Office of the Federal Register, 800 North Capitol Street, NW, suite 700, Washington, DC.

(h) This amendment becomes effective on April 19, 2000.

Issued in Renton, Washington, on March 6, 2000.

Donald L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.