# Airworthiness Directives; The Boeing Company Airplanes
> **Rule** · Final rule. · Published 2013-09-04 · Effective 2013-10-09 · 78 FR 54387
## Document
- **Document number:** 2013-21397
- **Category:** airworthiness
- **Manufacturer:** The Boeing Company
- **Type:** Rule
- **Action:** Final rule.
- **Citation:** 78 FR 54387
- **Publication date:** 2013-09-04
- **Effective date:** 2013-10-09
- **FAA docket:** Docket No. FAA-2013-0364
## Abstract

We are superseding airworthiness directive (AD) 90-23-14 for certain The Boeing Company Model 747 series airplanes. AD 90-23-14 required inspections of the fuselage skin lap splice between body station (BS) 340 and BS 400 at stringers (S)-6L and S-6R, and repair if necessary. This new AD adds new repetitive inspections for cracking in the S-6 skin lap splice, which terminates the inspections required by AD 90-23-14; eventual modification of the lap splice, which terminates the repetitive inspections; post-modification inspections; and corrective actions if necessary. This AD also adds airplanes to the applicability. This AD was prompted by a report of cracks up to 18.5 inches that were found at S-6L and S-6R on several airplanes, and subsequent analysis results that indicated that the protruding head fastener modification and related post-modification inspections required by AD 90-23-14 are not adequate to prevent cracking at the upper row of fasteners in the S-6 lap joint before the cracks reach a critical length. We are issuing this AD to detect and correct cracking at the upper row of fasteners in the S-6 lap joint, which could result in a sudden loss of cabin pressurization and the inability of the fuselage to withstand failsafe loads.

## Source
- [Federal Register document](https://www.federalregister.gov/documents/2013/09/04/2013-21397/airworthiness-directives-the-boeing-company-airplanes)
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