FAR 21.111 — STC Applicability
FAR 21.111 sets the scope of Subpart E, covering procedural requirements for issuing supplemental type certificates (STCs) under Part 21.
In Plain English
FAR 21.111 is the opening section of Subpart E of Part 21 and simply tells you what that subpart is about. It states that the subpart prescribes the procedural requirements for the issue of supplemental type certificates (STCs).
Why does this matter to you as a pilot?
- An STC is the FAA approval mechanism used when someone modifies an aircraft, engine, or propeller in a way that changes its type design but doesn't warrant a brand-new type certificate. Think of items like an autopilot retrofit, a winglet kit, an engine conversion, or an avionics upgrade.
- Subpart E (which 21.111 introduces) is the rulebook for how applicants get those modifications approved.
- As a pilot, you'll see STCs referenced in the aircraft's records and supplements in the POH/AFM. Knowing where STC authority comes from in the regulations helps you understand why those supplements are legally part of the aircraft's approved data.
In short: 21.111 is a scope statement — it doesn't impose a duty on pilots, but it anchors the rest of Subpart E that governs STC issuance.
Regulation Text
14 CFR § 21.111§ 21.111 Applicability.
This subpart prescribes procedural requirements for the issue of supplemental type certificates.
Oral Exam Questions a DPE Might Ask
Q1What does FAR 21.111 cover?
Per FAR 21.111, this section establishes the applicability of Subpart E, which prescribes the procedural requirements for the issuance of supplemental type certificates.
Q2Under which subpart of Part 21 are supplemental type certificates issued, and what section sets its applicability?
Supplemental type certificates are issued under Subpart E of Part 21, and FAR 21.111 is the applicability section that defines that subpart's scope.
Q3Does FAR 21.111 itself contain the procedures for getting an STC?
No. FAR 21.111 is only an applicability statement; it tells you that Subpart E contains the procedural requirements for issuing supplemental type certificates, with the actual procedures appearing in the sections that follow.
Studying for a checkride?
Related Sections in Part 21