Airworthiness Directive · Amendment 39-11700 · Boeing Model 747 Series Airplanes
Boeing Model 747 Series Airplanes
Model 747 series airplanes, as listed in Boeing Service Bulletin 747-57A2309, Revision 1, dated December 22, 1999, 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 (f) 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.
This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that requires repetitive inspections or checks to detect broken H-11 steel bolts at the wing rear spar side-of-body on the lower chord splice plate and kick fitting; and corrective actions, if necessary. This AD also requires eventual replacement of the existing bolts with new Inconel bolts, which constitutes terminating action for the repetitive inspections. This amendment is prompted by a report of broken bolts at the wing rear spar side-of-body on the lower chord splice plate. The actions specified by this AD are intended to prevent cracking of the bolts due to stress corrosion, which could result in reduced structural integrity of the wing-to-body joint structure.
To prevent cracking of the high strength H-11 steel bolts on the wing rear spar side-of-body on the lower chord splice plate and kick fitting due to stress corrosion, which could result in reduced structural integrity of the wing-to-body joint structure, accomplish the following:
(a) Within 12 months after the effective date of this AD, perform a detailed visual inspection, or alternatively, an ultrasonic inspection or torque check, to detect broken H-11 steel bolts common to the rear spar lower chord splice plate and the H-11 steel bolts common to the wing rear spar lower chord kick fitting, in accordance with Boeing Alert Service Bulletin 747-57A2309, dated February 25, 1999, or Boeing Service Bulletin 747-57A2309, Revision 1, dated December 22, 1999. Thereafter, repeat the applicable inspection or torque check at intervals not to exceed 18 months, until accomplishment of the actions specified in paragraph (d) of this AD.
Note 2: For the purposes of this AD, a detailed visual 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.”
(b) If there is any detection or indication that any bolt is broken during the inspection required by paragraph (a) of this AD, prior to further flight, perform the applicable corrective action [ i.e., ultrasonic inspection, torque check, high frequency eddy current (HFEC) inspection, repair, and replacement] in accordance with Boeing Alert Service Bulletin 747-57A2309, dated February 25, 1999, or Boeing Service Bulletin 747-57A2309, Revision 1, dated December 22, 1999, except as provided in paragraph (c) of this AD. Replacement of a broken bolt with a new Inconel bolt in accordance with the service bulletin constitutes terminating action for the repetitive inspection requirements of paragraph (a) of this AD for that bolt only.
(c) If any crack is detected during any corrective action required by paragraph (b) of this AD, or during the terminating action required by paragraph (d)(1) of this AD, and the service bulletin specifies to contact Boeing for appropriate action: Prior to further flight, repair 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. For a repair method to be approved by the Manager, Seattle ACO, as required by this paragraph, the Manager's approval letter must specifically reference this AD.
(d) Within 48 months after the effective date of this AD, accomplish the actions required by paragraphs (d)(1) and (d)(2) of this AD in accordance with Boeing Alert Service Bulletin 747-57A2309, dated February 25, 1999, or Boeing Service Bulletin 747-57A2309, Revision 1, dated December 22, 1999. Accomplishment of the actions specified in this paragraph constitutes terminating action for the repetitive inspection requirements of this AD.
(1) Prior to accomplishing the replacement required by paragraph (d)(2) of this AD, perform an open hole HFEC inspection to detect cracks at the bolt hole location for all high strength H-11 steel bolts common to the rear spar lower chord splice plate and all high strength H-11 steel bolts common to the wing rear spar lower chord kick fitting. If any crack is detected, prior to further flight, perform applicable corrective actions in accordance with paragraph (c) of this AD.
(2) Replace all high strength H-11 steel bolts common to the rear spar lower chord splice plate and all high strength H-11 steel bolts common to the wing rear spar lower chord kick fitting with new Inconel bolts.
(e) As of the effective date of this AD, no person shall install an H-11 steel bolt having part number (P/N) BACB30MT () * () or BACB30TR () * (), or any other H-11 steel bolt, in the locations specified in this AD, on any airplane.
