# Proposed AD 97-NM-185-AD: Boeing Model 747 Series Airplanes Equipped with Pratt & Whitney Model JT9D-70 Engines

- Type: Proposed airworthiness directive (not in force)
- Status: Became AD 98-21-17
- Action: Notice of proposed rulemaking (NPRM).
- Published: July 7, 1998, 63 FR 36628
- Comments due: August 21, 1998
- Became: [AD 98-21-17](https://openairdocs.org/ad/98-21-17)
- Docket: 97-NM-185-AD
- FR document: 98-17947
- Official PDF: https://openairdocs.org/files/sha256/d3/39/d339753866e749524b94224266d5c970322cc9584f43284676e2c4dad00795ee (from https://www.govinfo.gov/content/pkg/FR-1998-07-07/pdf/98-17947.pdf)
- Federal Register: https://www.federalregister.gov/documents/1998/07/07/98-17947/airworthiness-directives-boeing-model-747-series-airplanes-equipped-with-pratt-and-whitney-model
- Page: https://openairdocs.org/proposed/97-NM-185-AD

## Summary

This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that currently requires repetitive inspections to detect fatigue cracking of the spring beams on the outboard struts; replacement of cracked spring beams with new or serviceable spring beams; and follow-on actions. That action also provides an optional terminating action for the repetitive inspections. This action would remove that optional terminating action, and would require a new terminating action. This proposal is prompted by the development of an improved process for manufacturing titanium spring beams that will eliminate the embedded porosity flaws in the existing spring beams from which fatigue cracking can originate. The actions specified by this proposal are intended to prevent fatigue cracking of the spring beam, which could result in loss of an outboard strut.

## Notices in this docket

- Jul 7, 1998: Notice of proposed rulemaking (NPRM). (first notice), FR document 98-17947, comments due Aug 21, 1998 (https://www.federalregister.gov/documents/1998/07/07/98-17947/airworthiness-directives-boeing-model-747-series-airplanes-equipped-with-pratt-and-whitney-model)

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