# Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters (Type Certificate Previously Held by Schweizer Aircraft Corporation)
> **Rule** · Final rule. · Published 2017-07-21 · Effective 2017-08-25 · 82 FR 33778
## Document
- **Document number:** 2017-15032
- **Category:** airworthiness
- **Manufacturer:** Sikorsky
- **Type:** Rule
- **Action:** Final rule.
- **Citation:** 82 FR 33778
- **Publication date:** 2017-07-21
- **Effective date:** 2017-08-25
- **FAA docket:** Docket No. FAA-2016-6968
## Abstract

We are superseding airworthiness directive (AD) 93-17-13 for Schweizer Aircraft Corporation and Hughes Helicopters, Inc. (now Sikorsky Aircraft Corporation) (Sikorsky) Model TH55A, 269A, 269A-1, 269B, and 269C helicopters. AD 93-17-13 required installing tachometer markings and inspecting the lower coupling driveshaft (driveshaft). This new AD requires repetitive inspections of the driveshaft and expands the applicability to include Model 269C-1 helicopters. This AD is prompted by reports of accidents because of driveshaft failures. The actions of this AD are intended to prevent the unsafe condition on these products.

## Source
- [Federal Register document](https://www.federalregister.gov/documents/2017/07/21/2017-15032/airworthiness-directives-sikorsky-aircraft-corporation-helicopters-type-certificate-previously-held)
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