# Airworthiness Directives; McDonnell Douglas Helicopter Systems Model 369D, E, F, FF, 500N, AH-6, and MH-6 Helicopters
> **Rule** · Final rule; request for comments. · Published 1997-07-18 · Effective 1997-08-04 · 62 FR 38447
## Document
- **Document number:** 97-18932
- **Category:** airworthiness
- **Type:** Rule
- **Action:** Final rule; request for comments.
- **Citation:** 62 FR 38447
- **Publication date:** 1997-07-18
- **Effective date:** 1997-08-04
- **FAA docket:** Docket No. 97-SW-02-AD
## Abstract

This amendment adopts a new airworthiness directive (AD) that is applicable to McDonnell Douglas Helicopter Systems (MDHS) Model 369D, E, F, FF, 500N, AH-6, and MH-6 helicopters. This action requires replacement of certain transmission output drive gears (gears). This amendment is prompted by several reports of spalled or fractured gear teeth, most of which occurred during high-power or external-lift operations. The actions specified in this AD are intended to prevent failure of the gear, which could result in loss of main rotor control and subsequent loss of control of the helicopter.

## Source
- [Federal Register document](https://www.federalregister.gov/documents/1997/07/18/97-18932/airworthiness-directives-mcdonnell-douglas-helicopter-systems-model-369d-e-f-ff-500n-ah-6-and-mh-6)
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