Airworthiness Directive · Amendment 39-13852 · Boeing Model 707 and 720 Series Airplanes
Boeing Model 707 and 720 Series Airplanes
All Model 707 and 720 series airplanes, certificated in any category.
This amendment supersedes an existing airworthiness directive (AD), applicable to all Boeing Model 707 and 720 series airplanes, that currently requires inspections of the upper and lower chords of the wing front and rear spars, repair if necessary, and application of corrosion inhibitor to the inspected areas. This amendment removes the requirements of the existing AD, requires new detailed inspections and new high frequency eddy current (HFEC) inspections for corrosion and cracking, and requires certain related follow-on and investigative actions, if necessary. This amendment also expands the area of inspection to include the dry bay areas. The actions specified by this AD are intended to find and fix corrosion and stress corrosion cracking of the upper and lower chords on the wing front and rear spars, which could result in reduced structural integrity of the wing. This action is intended to address the identified unsafe condition.
To find and fix corrosion and stress corrosion cracking of the upper and lower spar chords on the front and rear spars of the wing, which could result in reduced structural integrity of the wing, accomplish the following:
Note 1: As of the effective date of this AD, the requirements of AD 2001-08-02, amendment 39-12179, are no longer effective or required.
(a) The term “service bulletin,” as used in this AD, means the Accomplishment Instructions of Boeing 707 Alert Service Bulletin A3240, Revision 4, dated September 6, 2001.
(b) Within 30 days after the effective date of this AD, do a detailed inspection of the entire length of the external surfaces of the front and rear wing spar chords and the internal surfaces of the front spar chords in the dry bays of the wings for corrosion, any signs of corrosion (e.g., blistering or signs of fuel leaks), or cracking; per the service bulletin. If no corrosion or cracking is found, before further flight: Except as specified in paragraph (e) of this AD, accomplish any applicable follow-on actions or investigative actions, per the service bulletin.
(c) Within 6 months after the effective date of this AD, perform a detailed inspection and a high frequency eddy current (HFEC) inspection of the entire length of the external surfaces of the front and rear wing spar chords and the internal surfaces of the front spar chords in the dry bays of the wings for any corrosion, signs of corrosion (e.g., blistering or signs of fuel leaks), or cracking; per the service bulletin. If no corrosion or cracking is found, before further flight, accomplish any applicable follow-on or investigative actions specified in the service bulletin and the actions specified in paragraph (e) of this AD. Thereafter, repeat the detailed and HFEC inspections at intervals not to exceed 12 months.
(d) If any corrosion or signs of corrosion (e.g., blistering or signs of fuel leaks) are found during any inspection required by this AD: Before further flight, repair per paragraph (d)(1) or (d)(2) of this AD, as applicable.
(1) If the corrosion is within the areas and limits specified in the service bulletin: Except as required by paragraph (e) of this AD, repair and accomplish all applicable follow-on and investigative actions, per the service bulletin.
(2) If the corrosion is outside the areas or limits specified in the service bulletin, 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 (DER) 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.
(e) Where the service bulletin specifies to apply BMS 3-23 (a corrosion inhibitor) or a Boeing approved equivalent, this AD requires that BMS 3-23 must be used or that any application of an equivalent corrosion inhibitor be approved by the Manager, Seattle ACO, or per data meeting the type certification basis of the airplane approved by a Boeing Company DER 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.
(f) If any cracking is found during any inspection required by this AD, including cracks that have been previously stop-drilled but not permanently repaired: Before further flight, repair per a method approved by the Manager, Seattle ACO; or per data meeting the type certification basis of the airplane approved by a Boeing Company DER 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. Operators should note that “stop drilling” of cracks as a means to defer repair is not permitted by this AD.
(g) In accordance with 14 CFR 39.19, the Manager, Seattle ACO, is authorized to approve alternative methods of compliance for this AD.
(h) Unless otherwise specified in this AD, the actions shall be done in accordance with Boeing 707 Alert Service Bulletin A3240, Revision 4, dated September 6, 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 Airplanes, PO Box 3707, Seattle, Washington 98124-2207. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or for information on the availability of this material at the National Archives and Records Administration (NARA), call (202) 741-6030, or go to http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.
