RULES and REGULATIONS DEPARTMENT OF TRANSPORTATION 14 CFR Part 39 [Docket No. 90 -NM- 109 -AD; Amdt 39 - 6768] Airworthiness Directives; Boeing Model 747 Series Airplanes Friday, October 12, 1990 AGENCY: Federal Aviation Administration (FAA), DOT. ACTION : Final rule. SUMMARY: This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, which currently requires inspection of the fuselage skin lap splice between body station (BS) 400 and BS 52 0 at stringers (S) 6L or S - 6R and repair, if necessary. This action deletes the option of reinspecting known small cracks in lieu of repairing them before further flight. This amendment is prom pted by further FAA consideration of the crack repair deferral option in the existing AD. This condition, if not corrected, could lead to sudden loss of c abin pressurization and the inability of the airplane fuselage to withstand fail- safe loads. EFFECTIVE DATE: November 16, 1990. ADDRESSES: The applicable service information may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. This information may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, Washington. F OR FURTHER INFORMATION CONTACT:Mr. Steven C. Fox, Seattle Aircraft Certification Office, Airframe Branch, ANM - 120S; telephone (206) 227 -2777. Mailing address: FAA, Northwest Mountain Region, 1601 Lind Avenue SW., Renton, Washington 98055 -4056. SUPPLEMENTARY INFORMATION: A proposal to amend Part 39 of the Federal Aviation Regulations by superseding AD 89 - 05 -03, Amendment 39 - 6146 (54 FR 7397, February 21, 1989), applicable to Boeing Model 747 series airplanes, to require inspection of the fuselage skin lap splice between BS 400 and BS 520 at stringer S - 6L and S - 6R and repair, if necessary, was published in the Federal Register on June 29, 1990 (55 FR 26701). Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the single comment received. The Air Transport Association (ATA) of America, commenting on behalf of its members, expressed no objection to the rule. Paragraph G. of the final rule has been revised to specify the current procedure for submitting requests for approval of alternate means of compliance. 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 change described above. The FAA has determined that this change will neither increase the economic burden on any operator nor increase the scope of the rule.There are approximately 628 Model 747 series airplanes of the affected design in the worldwide fleet. It is estimated that 202 airplanes of U.S. registry will be affected by this AD, that it will take approximately 8 manhours per air plane to accomplish the required actions, and that the average labor cost will be $40 per manhour. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $64,640. 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 p ower 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 o f a Federalism Assessment. For the reasons discussed above, I certify that this action (1) Is not a “major rule” under Executive Order 12291 ; (2) is not a “significant rule” under DOT Relgulatory 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 is contained in the regulatory docket. A copy of it may be obtained from the Rules Docket. List of Subjects in 14 CFR Part 39 Air transportation, Aircraft, Aviation safety, Safety. Adoption of the Amendment Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends 14 CFR part 39 of the Federal Aviation Regulations as follows: PART 39

— [AMENDED]1. The authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. 1354(a), 1421 and 1423; 49 U.S.C. 106(g) (Revised Pub. L. 97 -449, January 12, 1983); and 14 CFR 11.89 . § 39.13 [Amended] 2. Section 39.13 is amended by superseding AD 89 -05 -03, Amendment 39 - 6146 ( 54 FR 7397 , February 21, 1989), AD 89 - 05 - 03, with the following new aiworthiness directive: Boeing: Applies to Model 747 series airplanes, line num ber 001 through 628, certificated in any category. Com pliance required as indicated, unless previously accomplished. To prevent a failure of the fuselage skin lap splice between body station (BS) 400 and BS 520 at stringer S - 6Land S - 6R, accomplish the following: A. Conduct close visual and high frequency eddy current (HFEC) inspection of the fuselage skin lap splice between BS 400 and BS 520, at stringers S - 6L and S - 6R for cracking, in accordance with B oeing Alert Service Bulletin 747 - 53A2303, dated June 2, 1988, or Revision 1, dated March 29, 1990, at the following thresholds: 1. Within the next 100 landings after March 31, 1989 (the effective date of Amendment 39 - 6146, AD 89 - 05 -03), for airplanes that have accumulated 16,000 or more landings as of March 31, 1989, unless previously accomplished within the last 4,900 landings. 2. Within the next 1,000 landings after March 31, 1989, or prior to the accumulation of 16,000 landings, whichever occurs first, for airplanes that have accumulated between 12,000 and 16,000 landings, as of March 31, 1989, unless previously accomplished within the last 4,000 landings.3. Prior to the accumulation of 13,000 landings for airplanes that have accumulated 12,000 or fewer landings as of March 31, 1989, unless previously accomplished within the last 5,000 landings. Adequate lighting must be used for this inspection. The eddy current inspections may be conducted without removal of the paint, provided the paint does not interfere with the inspections. Paint must be removed, using an approved chemical stripper, in any situation where the inspector determines that the paint is interfering with the proper functioning of the inspection instrument. B. On airplanes which have been modified to the stretched-upper-deck configuration, as identified in Boeing Alert Service Bulletin 747 - 53A2303, dated June 2, 1988, or Revision 1, dated March 29, 1990, the accumulated landing threshold for com

pliance with paragraph A. of this AD is measured from the time of the stretched-upper-deck mo di fication. C. If no cracking is detected, repeat the close visual and HFEC inspections required by paragraph A. of this AD, at intervals not to exceed 5,000 landings. D. If cracks are detected, accomplish the repair or preventive mo dification of the affected lap splice in accordance with Boeing Alert Service Bulletin 747 - 53A2303, dated June 2, 1988, or Revision 1, dated March 29, 1990, prior to further pressurized flight. If cracks are repaired in local areas without accomplishing preventive modification of the entire affected lap area, continue inspections of the unmodified and unrepaired areas of the affected lap splice in accordance w

tth paragraph C. of this AD. E. For airplanes incorporating the preventative modification, as described in Boeing Alert Service Bulletin 747 - 53A2303, dated June 2, 1988, or Revision 1, dated March 29, 1990, accomplish the inspections required by paragraph A. of this AD, prior to accumulation of 10,000 landings after the mo dification and thereafter at intervals not to exceed 5,000 landings. If cracks are found, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, prior to further pressurized flight. F. For purposes of com

plying with this AD, the num ber of landings may be determined to equal the number of pre s surization cycles where the cabin pressure differential was greater than 1.5 psi. G. An alternate means of c om pliance or adjustment of the com pliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Northwest Mountain Region. Note: The request should be submitted directly to the Manager, Seattle ACO, and a copy s ent to the cognizant FAA Principal Inspector (PI). The PI will then forward comments or concurrence to the Seattle ACO. H. Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base in order to comply with the requirements of this AD. All persons affected by

this directive who have not already received the appropriate service documents from the manufacturer may obtain copies upon request to Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, Washington. This amendment becomes effective November 16, 1990. Issued in Renton, Washington, on October 1, 1990. Darell M. Pederson, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 90 -24081 Filed 10 - 11 - 90; 8:45 am] 55 FR 41510