# STC SA09014AC-D

- Type: Supplemental type certificate
- Status: Current, Amended
- Holder: S-TEC Corporation, United States
- Description: Installation of S-TEC yaw damper system, Model ST-591.
- Status date: May 7, 1999
- Product: Aircraft, Small Multi-Engine
- Certification basis: Part 21
- Data sheets: [TCDS 2A4](https://openairdocs.org/tcds/2A4)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/4AFC2D6DD0B67D0485256CC1007F39A2.0001
- DRS record last changed: December 5, 2025
- Page: https://openairdocs.org/stc/SA09014AC-D

## ADs that name it (0)

None.

## Approved models (7)

- Twin Commander Aircraft Corporation 680T ([TCDS 2A4](https://openairdocs.org/tcds/2A4))
- Twin Commander Aircraft Corporation 680V ([TCDS 2A4](https://openairdocs.org/tcds/2A4))
- Twin Commander Aircraft Corporation 680W ([TCDS 2A4](https://openairdocs.org/tcds/2A4))
- Twin Commander Aircraft Corporation 681 ([TCDS 2A4](https://openairdocs.org/tcds/2A4))
- Twin Commander Aircraft Corporation 690 ([TCDS 2A4](https://openairdocs.org/tcds/2A4))
- Twin Commander Aircraft Corporation 690A ([TCDS 2A4](https://openairdocs.org/tcds/2A4))
- Twin Commander Aircraft Corporation 690B ([TCDS 2A4](https://openairdocs.org/tcds/2A4))

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