# Proposed AD 97-SW-59-AD: Sikorsky Aircraft-Manufactured Model CH-54B Helicopters

- Type: Proposed airworthiness directive (not in force)
- Status: Became AD 99-15-14
- Action: Notice of proposed rulemaking (NPRM).
- Published: April 16, 1999, 64 FR 18835
- Comments due: June 15, 1999
- Became: [AD 99-15-14](https://openairdocs.org/ad/99-15-14)
- Docket: 97-SW-59-AD
- FR document: 99-9513
- Official PDF: https://openairdocs.org/files/sha256/6f/dd/6fddeabc437dfd8135d3bd9a065ff7ffe53d631a2110a16962d5dc6195548d5e (from https://www.govinfo.gov/content/pkg/FR-1999-04-16/pdf/99-9513.pdf)
- Federal Register: https://www.federalregister.gov/documents/1999/04/16/99-9513/airworthiness-directives-sikorsky-aircraft-manufactured-model-ch-54b-helicopters
- Page: https://openairdocs.org/proposed/97-SW-59-AD

## Summary

This document proposes the adoption of a new airworthiness directive (AD) that is applicable to Sikorsky Aircraft-manufactured Model CH-54B helicopters. This proposal would require initial and recurring inspections and rework or replacement, if necessary, of the second stage lower planetary plate (plate). This proposal is prompted by two reports of cracked plates that have been found during overhaul and inspections. The actions specified by the proposed AD are intended to prevent failure of the main gearbox plate due to fatigue cracking, which could lead to failure of the main gearbox and subsequent loss of control of the helicopter.

## Notices in this docket

- Apr 16, 1999: Notice of proposed rulemaking (NPRM). (first notice), FR document 99-9513, comments due Jun 15, 1999 (https://www.federalregister.gov/documents/1999/04/16/99-9513/airworthiness-directives-sikorsky-aircraft-manufactured-model-ch-54b-helicopters)

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