# STC SA4-1404

- Type: Supplemental type certificate
- Status: Current, Issued
- Holder: Marlin and Myron Harms, United States
- Description: Vacuum system 121 and 121A. (Eligible only on engines with dampened crankshafts).
- Status date: January 1, 1960
- Product: Aircraft, Single-Engine
- Certification basis: Part 21
- Data sheets: [TCDS 3A12](https://openairdocs.org/tcds/3A12), [TCDS A-799](https://openairdocs.org/tcds/A-799)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/354572B0D8C27840862570CF00754159.0001
- DRS record last changed: December 6, 2025
- Page: https://openairdocs.org/stc/SA4-1404

## ADs that name it (0)

None.

## Approved models (2)

- The Cessna Aircraft Company 170 ([TCDS A-799](https://openairdocs.org/tcds/A-799))
- The Cessna Aircraft Company 172 Series ([TCDS 3A12](https://openairdocs.org/tcds/3A12))

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