# Airworthiness Directives; Boeing Model 747 Series Airplanes Equipped with Pratt & Whitney JT9D-3 and -7 Series Engines
> **Rule** · Final rule; request for comments. · Published 1998-01-16 · Effective 1998-02-02 · 63 FR 2593
## Document
- **Document number:** 98-713
- **Category:** airworthiness
- **Manufacturer:** Boeing Model 747 Series
- **Type:** Rule
- **Action:** Final rule; request for comments.
- **Citation:** 63 FR 2593
- **Publication date:** 1998-01-16
- **Effective date:** 1998-02-02
- **FAA docket:** Docket No. 97-NM-267-AD
## Abstract

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that currently requires repetitive inspections for discrepancies of the forward engine mount bulkhead of the nacelle strut, and corrective action, if necessary. That AD also provides for optional terminating action for the repetitive inspections. For certain airplanes, this amendment adds repetitive inspections for discrepancies in the forward engine mount bulkhead and in the forward lower spar web, and corrective actions, if necessary. For other airplanes, this amendment adds a one- time inspection to detect stop drilled cracks of the exterior of the forward engine mount chord, and replacement of the chord with a new chord, if necessary. This amendment also adds an additional optional terminating action for the repetitive inspections. This amendment is prompted by reports that fatigue cracking was found in an area adjacent to the inspection area specified in the existing AD. The actions specified in this AD are intended to detect and correct such fatigue cracking, which could lead to the failure of the forward engine mount bulkhead and consequent separation of the engine from the airplane.

## Source
- [Federal Register document](https://www.federalregister.gov/documents/1998/01/16/98-713/airworthiness-directives-boeing-model-747-series-airplanes-equipped-with-pratt-and-whitney-jt9d-3)
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