Lower Skin Panels

Effective Date - 03/04/1999 Recurring - Yes

Supersedes - N/A Superseded by - N/A

Amendment 39-11047. Docket 99-NM-16-AD.

Applicability: All Model 727, 727-100, 727-200, 727C, 727-100C, and 727-200F 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 (g) 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 detect and correct fatigue cracking in the lower skin panel at the lower row of fasteners of the fuselage lap joints, which could result in sudden fracture and failure of the lap joints, and rapid decompression of the airplane; accomplish the following:

(a) Except as provided by paragraph (e) of this AD: At the later of the times specified in paragraphs (a)(1) and (a)(2) of this AD, perform an external detailed visual inspection to detect cracking in the lower skin panels at the lower row of fasteners of the fuselage lap joints at the following associated body stations (BS). Thereafter, repeat the inspection at intervals not to exceed 50 flight cycles until the requirements of either paragraph (c) or (d) of this AD are accomplished.

Table 1.

Model Stringer Body station

727 series airplanes and 727-100

S-4L, S-4R 259 through 700, and 1009 through 1183.

S-10L 259 through 310.

S-10R 259 through 360.

S-19L 259 through 660.

S-19R 259 through 500.

S-24L, S-24R 259 through 360.

S-26L 360 through 680.

S-26R 360 through 500, and 601 through 680.

727-200 series airplanes

S-4L, S-4R                  259 through 681; 686 through 720E; and 1009 through 1183.

S-10L                       259 through 310.

S-10R                       259 through 360.

S-19L, S19R                 259 through 360.

S-24L, S-24R                259 through 360.

S-26L                       360 through 644.

S-26R                       360 through 481, and 486 through 514.

727C series airplanes, 727-100C series airplanes.

S-4L 259 through 441, and 1080 through 1183.

S-4R                        259 through 619, and 1080 through 1183.

S-10L                       259 through 310.

S-10R                       259 through 360.

S-19L                       259 through 441.

S-19R                       259 through 500.

S-24L, S-24R                259 through 360.

S-26L                       360 through 680.

S-26R                       360 through 500, and 601 through 680.

727-200F series airplanes

S-4L                        259 through 441, and 1009 through 1183.

S-4R                        259 through 481, and 1009 through 1183.

S-10L                       259 through 310.

S-10R                       259 through 360.

                                      S-19L                       259 through 360.

                                      S-19R                       259 through 520.

                                      S-26L                       486 through 644.

                                      S-26R                       486 through 514.

(1) Inspect prior to the accumulation of 40,000 total flight cycles.

(2) Inspect within 50 flight cycles or 15 days after the effective date of this AD, whichever occurs first.

(b) After the effective date of this AD, no person may accomplish a repair or alteration that would interfere with the accomplishment of the inspection required by paragraph (a) of this AD (e.g., covering an affected lap joint), unless an alternative method of compliance for that inspection has been approved in accordance with the provisions of paragraph (g) of this AD.

(c) At the latest of the times specified in paragraphs (c)(1), (c)(2), and (c)(3) of this AD, perform a low frequency eddy current (LFEC) inspection to detect cracking in the lower skin panels at the lower row of fasteners of the fuselage lap joints, at the associated body stations specified in Table 1. of paragraph (a) of this AD; in accordance with Items F-43 and F-43A of Boeing Document No. D6-48040-1, Volumes 1 and 2, "Supplemental Structural Inspection Document" (SSID), Revision H, dated June 1994 (hereinafter referred to as the "Boeing Document"). Thereafter, repeat the LFEC inspection at intervals not to exceed 600 flight cycles. Accomplishment of the LFEC inspection constitutes terminating action for the repetitive inspections required by paragraph (a) of this AD.

(1) Inspect prior to the accumulation of 40,000 total flight cycles.

(2) Inspect within 300 flight cycles or 60 days after the effective date of this AD, whichever occurs first.

(3) Inspect within 600 flight cycles after accomplishing the same inspection in accordance with AD 98-11-03, amendment 39-10530.

Note 2: The provisions of paragraph 1. of Item F-43A of the Boeing Document, which give credit for performing the modification or repair specified in Figure 4 of Boeing Service Bulletin 727-53-72, Revision 5, dated June 1, 1989, do not apply to this AD. All lap joints specified in this AD are to be inspected whether or not they have been modified or repaired previously in accordance with that service bulletin.

Note 3: Accomplishment of the initial LFEC inspection prior to the effective date of this AD in accordance with the initial LFEC inspection specified in the Boeing Document, is considered acceptable for compliance with the initial inspection specified in paragraph (c) of this AD.

(d) Accomplishment of internal detailed visual and high frequency eddy current (HFEC) inspections to detect cracking in the lower skin panels at the lower row of fasteners of the fuselage lap joints, at the associated body stations specified in Table 1. of paragraph (a) of this AD; in accordance with the Boeing Document, constitutes terminating action for the repetitive inspection requirements of paragraphs (a) and (c) of this AD, provided that the internal detailed visual and HFEC inspections are repeated thereafter at intervals not to exceed 7,000 flight cycles.

Note 4: Accomplishment of the internal HFEC inspection prior to the effective date of this AD in accordance with the HFEC inspection specified in the Boeing Document is considered acceptable for compliance with the initial HFEC inspection specified in paragraph (d) of this AD, provided that the repetitive inspections in paragraph (d) of this AD are accomplished as specified.

(e) Airplanes on which the inspection required by paragraph (c) or (d) of this AD is performed within the compliance time specified in paragraph (a) of this AD are not required to accomplish the inspection required by paragraph (a).

(f) If any crack is detected during any inspection required by this AD, prior to further flight, perform internal detailed visual and HFEC inspections to detect additional cracking in the entire lap joint of the lower skin panel where the crack was found, in accordance with the Boeing Document, and repair any crack detected in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate; or in accordance with 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.

(g) 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 5: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.

(h) 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.

(i) The inspections shall be done in accordance with Boeing Document No. D6-48040-1, Volumes 1 and 2, "Supplemental Structural Inspection Document" (SSID), Revision H, dated June 1994, which contains the following list of effective pages:

Revision level

Page No. shown on page shown on page

List of Active Pages: Pages 1 thru 17.2.......................H

(Note: The issue date of Revision H is indicated only on the title page; no other page of the document is dated.) This incorporation by reference was approved previously by the Director of the Federal Register, in accordance with 5 U.S.C. 552(a) and 1 CFR part 51, as of June 23, 1998 (63 FR 27455, May 19, 1998). 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.

(j) This amendment becomes effective on March 4, 1999.

FOR FURTHER INFORMATION CONTACT: Walt Sippel, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2774; fax (425) 227-1181.