# Proposed AD 98-SW-77-AD: Eurocopter Deutschland GMBH Model MBB- BK 117 Helicopters

- Type: Proposed airworthiness directive (not in force)
- Status: Became AD 2000-06-07
- Action: Notice of proposed rulemaking (NPRM).
- Published: December 10, 1999, 64 FR 69208
- Comments due: February 8, 2000
- Became: [AD 2000-06-07](https://openairdocs.org/ad/2000-06-07)
- Docket: 98-SW-77-AD
- FR document: 99-32085
- Official PDF: https://openairdocs.org/files/sha256/96/29/96298fa9cebca79f7ce1567ff788ba2258f212cd56e82ae7cf6415d498dd8ccc (from https://www.govinfo.gov/content/pkg/FR-1999-12-10/pdf/99-32085.pdf)
- Federal Register: https://www.federalregister.gov/documents/1999/12/10/99-32085/airworthiness-directives-eurocopter-deutschland-gmbh-model-mbb--bk-117-helicopters
- Page: https://openairdocs.org/proposed/98-SW-77-AD

## Summary

This document proposes the adoption of a new airworthiness directive (AD) that is applicable to Eurocopter Deutschland Model MBB- BK 117 helicopters. This proposal would change the retirement life for the tail rotor (output) drive bevel gear (bevel gear). This proposal is prompted by a fatigue analysis of the bevel gear conducted by the manufacturer due to installation of different tail rotor blades. The actions specified by the proposed AD are intended to prevent fatigue failure of the bevel gear, loss of tail rotor drive, and subsequent loss of control of the helicopter.

## Notices in this docket

- Dec 10, 1999: Notice of proposed rulemaking (NPRM). (first notice), FR document 99-32085, comments due Feb 8, 2000 (https://www.federalregister.gov/documents/1999/12/10/99-32085/airworthiness-directives-eurocopter-deutschland-gmbh-model-mbb--bk-117-helicopters)

---
OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.