# STC ST931SO

- Type: Supplemental type certificate
- Status: Current, Issued
- Holder: MCA Leasing Corporation, United States
- Description: Addition of smoke detector system for conversion to cargo carrier.
- Status date: May 20, 1977
- Product: Aircraft, Large Multi-Engine
- Certification basis: Part 21
- Data sheets: [TCDS 4A28](https://openairdocs.org/tcds/4A28)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/1158498D245609F685256CC3000374D2.0001
- DRS record last changed: December 6, 2025
- Page: https://openairdocs.org/stc/ST931SO

## ADs that name it (0)

None.

## Approved models (2)

- The Boeing Company 720 ([TCDS 4A28](https://openairdocs.org/tcds/4A28))
- The Boeing Company 720B ([TCDS 4A28](https://openairdocs.org/tcds/4A28))

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