# Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters
> **Rule** · Final rule. · Published 2014-04-28 · Effective 2014-06-02 · 79 FR 23260
## Document
- **Document number:** 2014-08849
- **Category:** airworthiness
- **Manufacturer:** Sikorsky
- **Type:** Rule
- **Action:** Final rule.
- **Citation:** 79 FR 23260
- **Publication date:** 2014-04-28
- **Effective date:** 2014-06-02
- **FAA docket:** Docket No. FAA-2013-0637
## Abstract

We are superseding Airworthiness Directive (AD) 2005-22-01 for Sikorsky Aircraft Corporation (Sikorsky) Model S-76A, B, and C helicopters. AD 5002-22-01 required inspecting the main rotor lower bifilar arm assembly (bifilar arm assembly) for a crack, and if there is a crack, replacing the bifilar arm assembly. AD 2005-22-01 also required a one-time test for the correct torque on the lug nuts, and if necessary, conducting torque stabilization tests. This new AD retains the requirements of AD 2005-22-01 and also requires replacing the main rotor hub (MRH) pilot with a different part-numbered MRH pilot, which is terminating action for the requirements of the AD. This AD was prompted by the development of a terminating procedure for the inspections required by AD 2005-22-01. We are issuing this AD to prevent failure of a bifilar lug, damage to the main rotor system, and subsequent loss of control of the helicopter.

## Source
- [Federal Register document](https://www.federalregister.gov/documents/2014/04/28/2014-08849/airworthiness-directives-sikorsky-aircraft-corporation-helicopters)
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