# Proposed AD FAA-2010-0490: Sikorsky Aircraft Corporation (Sikorsky) Model S-70A and S-70C Helicopters

- Type: Proposed airworthiness directive (not in force)
- Status: Became AD 2010-23-24
- Products: Sikorsky
- Product type: Aircraft
- Action: Notice of proposed rulemaking (NPRM).
- Published: May 13, 2010, 75 FR 26888
- Comments due: July 12, 2010
- Became: [AD 2010-23-24](https://openairdocs.org/ad/2010-23-24)
- Docket: FAA-2010-0490 (https://www.regulations.gov/docket/FAA-2010-0490, where comments are filed)
- Project: 2010-SW-037-AD
- FR document: 2010-11423
- Official PDF: https://openairdocs.org/files/sha256/d8/d7/d8d7d97c1e1aaf3be8b31581b1187ae2778783c97270c3185b6cf0d2bcb5bd90 (from https://www.govinfo.gov/content/pkg/FR-2010-05-13/pdf/2010-11423.pdf)
- Federal Register: https://www.federalregister.gov/documents/2010/05/13/2010-11423/airworthiness-directives-sikorsky-aircraft-corporation-sikorsky-model-s-70a-and-s-70c-helicopters
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/10706B1E20CE6DB786257722005C1DA4.0001
- Page: https://openairdocs.org/proposed/FAA-2010-0490

## Summary

This document proposes adopting a new airworthiness directive (AD) for the Sikorsky Model S-70A and S-70C helicopters. This proposal would require an ultrasonic test (UT) inspection of the tail gearbox output bevel gear (gear) for a crack. If you find a crack, replacing the gear with an airworthy gear before further flight would be required. This proposal is prompted by three gear cracking incidents, one of which resulted in the tail rotor separating from the helicopter. The actions specified by this proposed AD are intended to detect a crack in the gear to prevent a tail rotor separating, loss of tail rotor control, and subsequent loss of control of the helicopter.

## Notices in this docket

- May 13, 2010: Notice of proposed rulemaking (NPRM). (first notice), FR document 2010-11423, comments due Jul 12, 2010 (https://www.federalregister.gov/documents/2010/05/13/2010-11423/airworthiness-directives-sikorsky-aircraft-corporation-sikorsky-model-s-70a-and-s-70c-helicopters)

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