# STC SA3-721

- Type: Supplemental type certificate
- Status: Current, Issued
- Holder: Vapor Heating Corp, United States
- Description: Cabin temperature control system with Janitrol S-25 heater.
- Status date: January 1, 1960
- Product: Aircraft, Small Multi-Engine
- Certification basis: Part 21
- Data sheets: [TCDS 2A4](https://openairdocs.org/tcds/2A4), [TCDS 6A1](https://openairdocs.org/tcds/6A1)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/74BB42C3C943EB30862570CB00585F9D.0001
- DRS record last changed: December 6, 2025
- Page: https://openairdocs.org/stc/SA3-721

## ADs that name it (0)

None.

## Approved models (4)

- Twin Commander Aircraft Corporation 500 ([TCDS 6A1](https://openairdocs.org/tcds/6A1))
- Twin Commander Aircraft Corporation 520 ([TCDS 6A1](https://openairdocs.org/tcds/6A1))
- Twin Commander Aircraft Corporation 560 ([TCDS 6A1](https://openairdocs.org/tcds/6A1))
- Twin Commander Aircraft Corporation 680 ([TCDS 2A4](https://openairdocs.org/tcds/2A4))

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