Airworthiness Directive · Amendment 39-14831 · Boeing Model 747-100, 747-100B, 747-200B, 747-200C, 747-200F, 747SR, and 747SP Series Airplanes
Boeing Model 747-100, 747-100B, 747-200B, 747-200C, 747-200F, 747SR, and 747SP Series Airplanes
This AD applies to Boeing Model 747-100, 747-100B, 747-200B, 747-200C, 747-200F, 747SR, and 747SP series airplanes, certificated in any category; line numbers 001 through 430 inclusive.
The FAA is superseding an existing airworthiness directive (AD), which applies to certain Boeing Model 747 series airplanes. That AD currently requires repetitive inspections to detect cracks at certain stringer fastener locations; and repair, if necessary. For certain airplanes, that AD requires a modification in certain areas where reports indicate that cracking was prevalent. This modification terminates the repetitive inspections only for those areas, and is also an option for other airplanes affected by the existing AD. This new AD requires an additional inspection of areas that may have Alodine-coated rivets installed, and repair if necessary. This AD results from a report of cracking discovered in a skin lap joint that was previously inspected using the eddy current method. We are issuing this AD to prevent rapid decompression of the airplane due to disbonding and subsequent cracking of the skin panels.
You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.
Prior to the accumulation of 12,000 flight cycles or within the next 1,000 flight cycles after January 22, 1991 (the effective date of AD 90-26-10), whichever occurs later, unless previously accomplished within the last 1,000 flight cycles, conduct an external detailed and external high frequency eddy current (HFEC) inspection for cracks of the fuselage skin from body station (BS) 220 to BS 520, left- and right-hand sides of the airplane between stringers (S)-6 and S-14, excluding the skin lap joints, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2321, dated October 31, 1989; or Revision 7, dated October 27, 2005. After the effective date of this AD, only Revision 7 may be used. Doing the inspections in this paragraph in accordance with Revision 7 of the service bulletin eliminates the need for doing the actions in paragraph (k) of this AD. Repeat the inspections thereafter at intervals not to exceed 2,000 flight cycles until the terminating modification in paragraph (g) of this AD is done, except as provided by paragraph (h) of this AD.
Note 1: For the purposes of this AD, a detailed inspection is: “An intensive examination of a specific item, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at an intensity deemed appropriate. Inspection aids such as mirror, magnifying lenses, etc., may be necessary. Surface cleaning and elaborate procedures may be required.”
For airplanes line numbers 001 through 200 inclusive, prior to the accumulation of 20,000 total flight cycles, or within 48 months after the January 22, 1991, whichever occurs later: Perform the terminating modification of the skin panel from BS 340 to BS 520, S-6 to S-14, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2321, dated October 31, 1989; or Revision 7, dated October 27, 2005. After the effective date of this AD, only Revision 7 may be used. The modification consists of replacing the skin panel with a new skin panel which was manufactured utilizing the improved hot phosphoric acid anodize bonding process.
(h) Replacement of the skin panel required by paragraph (g) of this AD constitutes terminating action for the inspections from BS 340 to BS 520 required by paragraphs (f) and (k) of this AD. The inspections from BS 220 to BS 340 required by paragraph (f) of this AD are to be continued.
(i) Before the effective date of this AD: Flight cycles conducted at 2.0 pounds per square inch (psi) or less cabin differential pressure need not be counted for the purpose of this airworthiness directive.
(j) Before the effective date of this AD: For Model 747SR airplanes only, the threshold and repetitive inspection intervals specified herein may be multiplied by the 1.2 adjustment factor based on continued mixed operation at lower cabin pressure differentials.
For airplanes identified in Figure 9 of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2321, Revision 7, dated October 27, 2005, as requiring additional inspection: Within 150 flight cycles after the effective date of this AD, do the inspection in paragraph (k)(1) or (k)(2) of this AD in accordance with the Accomplishment Instructions of the service bulletin.
(1) Do an external detailed inspection for cracking of Area 1, and repeat the inspection thereafter at intervals not to exceed 150 flight cycles until one of the actions in paragraph (k)(1)(i), (k)(1)(ii), or (k)(1)(iii) is accomplished. Repeat the inspection of Area 1 thereafter in accordance with the requirements of paragraph (f) of this AD.
(i) The inspection in accordance with paragraph (k)(1) of this AD has been done seven times. If this option is used: Within 150 flight cycles after the seventh inspection, do the inspection required by paragraph (k)(2) of this AD.
(ii) The inspection in accordance with paragraph (k)(2) has been accomplished.
(iii) The inspections in accordance with paragraph (f) of this AD has been accomplished once in accordance with Revision 7 of the service bulletin.
(2) Do an external HFEC inspection for cracking of Area 1 in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2321, Revision 7, dated October 27, 2005. Repeat the inspection of Area 1 thereafter in accordance with the requirements of paragraph (f) of this AD.
If any crack is found during any inspection required by this AD: Before further flight, repair in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2321, dated October 31, 1989; or Revision 7, dated October 27, 2005. After the effective date of this AD, only Revision 7 of the service bulletin may be used. Where Revision 7 of the service bulletin specifies to contact Boeing for repair instructions: Before further flight, repair using a method approved in accordance with the procedures specified in paragraph (n) of this AD.
For the purposes of calculating the compliance threshold and repetitive interval for actions required by paragraphs (f), (g), and (k) of this AD, on or after the effective date of this AD: All flight cycles, including the number of flight cycles in which cabin differential pressure is at 2.0 psi or less, must be counted when determining the number of flight cycles that have occurred on the airplane, and a 1.2 adjustment factor may not be used. However, for airplanes on which the repetitive interval for the actions required by paragraphs (f) and (k) of this AD have been calculated in accordance with paragraph (i) or (j) of this AD by excluding the number of flight cycles in which cabin differential pressure is at 2.0 pounds psi or less, or by using a 1.2 adjustment factor: Continue to adjust the repetitive interval in accordance with paragraph (i) or (j) of this AD until the next inspections required by paragraph (f) or (k) of this AD are accomplished. Thereafter, no adjustment to compliance times based on paragraph (i) or (j) of this AD is allowed.
