# Airworthiness Directives; Agusta S.p.A. (Type Certificate Currently Held by AgustaWestland S.p.A) (Agusta) Helicopters
> **Rule** · Final rule. · Published 2013-10-31 · Effective 2013-12-05 · 78 FR 65161
## Document
- **Document number:** 2013-24038
- **Category:** airworthiness
- **Manufacturer:** Agusta S.p.A. (Type Certificate Currently Held by AgustaWestland S.p.A) (Agusta)
- **Type:** Rule
- **Action:** Final rule.
- **Citation:** 78 FR 65161
- **Publication date:** 2013-10-31
- **Effective date:** 2013-12-05
- **FAA docket:** Docket No. FAA-2013-0518
## Abstract

We are adopting a new airworthiness directive (AD) for Agusta Model A109A, A109AII, and A109C helicopters with a certain third stage turbine wheel installed. This AD requires installing a placard on the instrument panel and revising the limitations section of the rotorcraft flight manual (RFM). This AD was prompted by several incidents of third stage engine turbine wheel failures, which were caused by excessive vibrations at certain engine speeds during steady-state operations. These actions are intended to alert pilots to avoid certain engine speeds during steady-state operations, prevent failure of the third stage engine turbine, engine power loss, and subsequent loss of control of the helicopter.

## Source
- [Federal Register document](https://www.federalregister.gov/documents/2013/10/31/2013-24038/airworthiness-directives-agusta-spa-type-certificate-currently-held-by-agustawestland-spa-agusta)
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