SA09228AC-D
Installation of S-TEC System 30 ALT Altitude Hold System Model ST-686. Held by S-Tec Corporation, which holds 1,083 approved modifications in all. Last revised June 4, 1997. System: other and general.
What it applies to
- Kind of product
- Aircraft
- Design holder
- Cessna Aircraft Company; Cessna Aircraft Company; Cessna Aircraft Company; Cessna Aircraft Company; Cessna Aircraft Company; Cessna Aircraft Company; Cessna Aircraft Company; Cessna Aircraft Company; Cessna Aircraft Company; Cessna Aircraft Company; Cessna Aircraft Company; Cessna Aircraft Company
- Models
- 172, 172A, 172B, 172C, 172D, 172E, 172F (USAF T-41A), 172G, 172H (USAF T-41A), 172I, 172K, 172L
- Type certificates
- 3A12, 3A12, 3A12, 3A12, 3A12, 3A12, 3A12, 3A12, 3A12, 3A12, 3A12, 3A12
- On this site
- Cessna 172 Skyhawk 20,676 registered
- The FAA's record
- On the FAA's site
What an approved modification is
A supplemental type certificate is the FAA's approval of a change to a certified design: a new engine or propeller, avionics, an autopilot, floats, a parachute, a larger fuel tank, an ice-protection kit. The company holding it may sell the kit and the paperwork to owners of the listed models; the modification then becomes part of that aircraft's record. The FAA's list says what was approved and for which models, not how many aircraft carry it.
Source: FAA supplemental type certificates (Dynamic Regulatory System). Register counts from the FAA register of October 20, 2026.