Airworthiness Directives; Boeing Model 747 Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Final rule.

SUMMARY:

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that requires repetitive high frequency eddy current inspections to find cracking of the bulkhead frame support at body station 2598 under the hinge support fittings of the horizontal stabilizer, and repair if cracking is found. These actions are necessary to find and fix fatigue cracking in the frame support, which could result in inability of the structure to carry horizontal stabilizer flight loads and reduced controllability of the horizontal stabilizer. This action is intended to address the identified unsafe condition.

DATES:

Effective August 16, 2001.

The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of August 16, 2001.

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, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-1153; fax (425) 227-1181.

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 all Boeing Model 747 series airplanes was published in the Federal Register on February 21, 2001 (66 FR 10974). That action proposed to require repetitive high frequency eddy current inspections to find cracking of the bulkhead frame support at body station 2598 under the hinge support fittings of the horizontal stabilizer, and repair if cracking is found.

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.

Revised Service Information

Two commenters ask that the FAA approve Boeing Service Bulletin 747-53A2449, Revision 1, dated May 24, 2001, as another source of service information for doing the actions specified in the proposed rule. The proposed rule cited Boeing Alert Service Bulletin 747-53A2449, dated June 8, 2000, as the proper source of service information for doing the specified actions.

One commenter, the manufacturer, states that the revised service bulletin changes the airplane effectivity by limiting the affected airplanes to line numbers (L/N) 1 through 1307, inclusive. Airplanes delivered after L/N 1307 have been redesigned to reduce the possibility of early cracking of the bulkhead in the subject area. The revised bulletin also corrects the bolt torque values specified in the original issue of the service bulletin. The commenter adds that using the torque values in the original issue could lead to over-torque of the bolts during installation.

Another commenter suggests that, when a revised service bulletin is released, it should specify the correct torque values for the shear bolts, or reference the Structural Repair Manual, Chapter 51-30-04 or 51-40-04. The commenter adds that the manufacturer informed the commenter by telex that, if the shear bolts are torqued per the service bulletin specified in the proposed rule, they will be over-torqued. The commenter does not intend to do the inspections until a revised service bulletin is issued, in order to minimize the risk of over-torquing the shear bolts and to avoid the need to rework and replace the bolts.

The FAA concurs with the commenters and has reviewed and approved Boeing Service Bulletin 747-53A2449, Revision 1, dated May 24, 2001; which is referenced in the final rule as the proper source of service information for doing the actions specified. Accordingly, the applicability section has been changed to specify Model 747 series airplanes, as listed in Revision 1 of the service bulletin; the number of airplanes, as well as the number of work hours, which were increased in Revision 1 of the service bulletin, have been changed in the cost impact section; and a new Note 2 has been added to specify that actions done before the effective date of this AD, per the original issue of the service bulletin, are acceptable for compliance with paragraph (a) of the final rule.

Although the torque values have been corrected in the revised service bulletin, operators who used the incorrect torque values during re-installation of the bolts can wait until the next repeat inspection to use the correct torque values. We have determined that over-torqued bolts will not compromise safety, as long as the bolts are properly torqued during the next repeat inspection.

Extend Compliance Time

One commenter asks that the compliance time for the proposed rule be extended from before the accumulation of 10,000 total flight cycles, or within 1,000 flight cycles after the effective date of this AD, whichever occurs later; to before the accumulation of 10,000 total flight cycles, or within 1,200 flight cycles after the effective date of this AD, whichever occurs later. The commenter states that its recommendation will allow the accomplishment of the initial inspection during its regularly scheduled heavy maintenance checks, while still maintaining an equivalent level of safety.

The FAA does not concur with the commenter's request because the cracking of the bulkhead frame support is caused by fatigue, which is contingent on the number of accumulated flight cycles. In developing an appropriate compliance time for this action, we considered not only the degree of urgency associated with addressing the subject unsafe condition, but the manufacturer's recommendation as to an appropriate compliance time, and the practical aspect of accomplishing the required inspection within an interval of time that parallels normal scheduled maintenance for the majority of affected operators. We have determined that before the accumulation of 10,000 total flight cycles, or within 1,000 flight cycles after the effective date of this AD, whichever occurs later, represents an appropriate compliance time allowable for the initial inspection to be accomplished during scheduled maintenance intervals. However, under the provisions of paragraph (c) of the final rule, we may approve requests for adjustments to the compliance time if data are submitted to substantiate that such an adjustment would provide an acceptable level of safety.

Terminating Action

One commenter asks that a terminating action, such as oversizing the subject fastener holes, be provided by the manufacturer. The commenter states that this would alleviate potential structural damage caused by the repeated fastener and sealant removal, and installation at a critical joint. The FAA agrees with the intent of the comment, but until the manufacturer provides adequate service information giving procedures for a terminating action, such action cannot be added. If terminating action becomes available in the future, we may consider additional rulemaking. No change to the final rule is necessary in this regard.

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 1,147 airplanes of the affected design in the worldwide fleet. The FAA estimates that 261 airplanes of U.S. registry will be affected by this AD, that it will take approximately 18 work hours (9 work hours per side) per airplane to accomplish the required inspections, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $281,880, or $1,080 per airplane, per inspection cycle.

The cost impact figure discussed above is 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. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions.

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 adding the following new airworthiness directive:

2001-14-07 Boeing: Amendment 39-12318. Docket 2000-NM-251-AD.

Applicability: Model 747 series airplanes, as listed in Boeing Service Bulletin 747-53A2449, Revision 1, dated May 24, 2001, 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 (c) 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 find and fix fatigue cracking in the bulkhead frame support at body station (BS) 2598 under the hinge support fittings of the horizontal stabilizer, which could result in inability of the structure to carry horizontal stabilizer flight loads and reduced controllability of the horizontal stabilizer, accomplish the following:

Repetitive High Frequency Eddy Current (HFEC) Inspections

(a) Before the accumulation of 10,000 total flight cycles, or within 1,000 flight cycles after the effective date of this AD, whichever occurs later: Do an open-hole HFEC inspection to find cracking of the bulkhead frame support under the hinge support fittings of the horizontal stabilizer on the left and right sides at BS 2598, per Figure 2 of the Accomplishment Instructions of Boeing Service Bulletin 747-53A2449, Revision 1, dated May 24, 2001. Repeat the inspection after that at intervals not to exceed 3,000 flight cycles.

Note 2:

Inspections accomplished before the effective date of this AD per Boeing Alert Service Bulletin 747-53A2449, dated June 8, 2000, are considered acceptable for compliance with the applicable inspection specified in paragraph (a) of this AD.

Repair

(b) If any cracking is found during any inspection required by paragraph (a) of this AD, before further flight, repair per a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; or per data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative who has been authorized by the Manager, Seattle ACO, to make such findings. For a repair method to be approved by the Manager, Seattle ACO, as required by this paragraph, the approval letter must specifically reference this AD.

Alternative Methods of Compliance

(c) 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 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

(d) 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.

Incorporation by Reference

(e) Except as provided by paragraph (b) of this AD, the actions shall be done per Boeing Service Bulletin 747-53A2449, Revision 1, dated May 24, 2001. 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.

Effective Date

(f) This amendment becomes effective on August 16, 2001.