# Airworthiness Directives; Enstrom Helicopter Corporation Model F-28, F-28A, F-28C, F-28F, 280, 280C, 280F and 280FX Helicopters
> **Rule** · Final rule; request for comments. · Published 2001-10-29 · Effective 2001-11-13 · 66 FR 54418
## Document
- **Document number:** 01-26965
- **Category:** airworthiness
- **Type:** Rule
- **Action:** Final rule; request for comments.
- **Citation:** 66 FR 54418
- **Publication date:** 2001-10-29
- **Effective date:** 2001-11-13
- **FAA docket:** Docket No. 2001-SW-28-AD
## Abstract

This amendment supersedes an existing airworthiness directive (AD) for Enstrom Helicopter Corporation (EHC) Model F-28, F-28A, and 280 helicopters. That AD currently requires inspecting the main rotor shaft (shaft) for a crack or other evidence of damage until appropriately modifying or replacing the shaft with an airworthy shaft at specified time intervals. This amendment adds EHC Model F-28C, F- 28F, 280C, 280F, and 280FX helicopters and establishes life limits after which all unmodified shafts must be retired. This amendment requires determining the radius of the shaft fillet, certain visual and dye-penetrant inspections before further flight, and replacing certain main rotor transmissions. This amendment is prompted by the failure of a shaft on an EHC Model F-28A helicopter due to a fatigue crack. The actions specified by this AD are intended to prevent shaft failure and subsequent loss of control of the helicopter.

## Source
- [Federal Register document](https://www.federalregister.gov/documents/2001/10/29/01-26965/airworthiness-directives-enstrom-helicopter-corporation-model-f-28-f-28a-f-28c-f-28f-280-280c-280f)
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