# Proposed AD 99-SW-73-AD: Eurocopter Deutschland GMBH Model MBB-BK 117 A-1, A-3, A-4, B-1, B-2, and C-1 Helicopters

- Type: Proposed airworthiness directive (not in force)
- Status: Became AD 2000-08-16
- Action: Notice of proposed rulemaking (NPRM).
- Published: February 4, 2000, 65 FR 5453
- Comments due: April 4, 2000
- Became: [AD 2000-08-16](https://openairdocs.org/ad/2000-08-16)
- Docket: 99-SW-73-AD
- FR document: 00-2402
- Official PDF: https://openairdocs.org/files/sha256/22/63/22632e1711d923212db6cb231db17a6cdc41fdcf62b7574ee2a803871de65fa2 (from https://www.govinfo.gov/content/pkg/FR-2000-02-04/pdf/00-2402.pdf)
- Federal Register: https://www.federalregister.gov/documents/2000/02/04/00-2402/airworthiness-directives-eurocopter-deutschland-gmbh-model-mbb-bk-117-a-1-a-3-a-4-b-1-b-2-and-c-1
- Page: https://openairdocs.org/proposed/99-SW-73-AD

## Summary

This document proposes the adoption of a new airworthiness directive (AD) applicable to Eurocopter Deutschland GMBH (ECD) Model MBB-BK 117 A-1, A-3, A-4, B-1, B-2, and C-1 helicopters. This proposal would require modifying the engine and transmission cowling doors (cowling doors). This proposal is prompted by an emergency landing of an ECD Model MBB-BK 117 helicopter after the No. 1 engine cowling opened, separated from the helicopter, and struck the main and tail rotor blades resulting in a tail rotor imbalance and subsequent departure of the tail rotor gear box from the helicopter. The actions specified by the proposed AD are intended to prevent the cowling doors opening during flight, separating from the helicopter and impacting the main or tail rotor blades, and subsequent loss of control of the helicopter.

## Notices in this docket

- Feb 4, 2000: Notice of proposed rulemaking (NPRM). (first notice), FR document 00-2402, comments due Apr 4, 2000 (https://www.federalregister.gov/documents/2000/02/04/00-2402/airworthiness-directives-eurocopter-deutschland-gmbh-model-mbb-bk-117-a-1-a-3-a-4-b-1-b-2-and-c-1)

---
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.