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Atlas / STC / SA3-404

FAA · Supplemental Type Certificate

STC SA3-404

Installation of Sperry SP20 autopilot.

Current Reissued Aircraft Large Multi-Engine Rev 03/07/2014 View PDF on drs.faa.gov ↗

What is an STC?

A Supplemental Type Certificate authorizes a major modification or alteration to an FAA-certificated aircraft. STCs are how operators legally install new avionics, change fuel systems, add floats, swap engines, etc. — every change beyond a minor modification needs one.

Applicable aircraft (1)

Certification basis — 14 CFR

Specific sections

  • Sec. 111
  • Sec. 113
  • Sec. 115
  • Sec. 117
  • Sec. 119
  • Sec. 120
  • § 21.47

The STC PDF on drs.faa.gov is the authoritative document — it lists installation instructions, ICA requirements, and any limitations. Open PDF ↗