FAR 21.91 — Type Certificate Changes
FAR 21.91 sets the applicability of Subpart D, covering procedural requirements for approving changes to type certificates. Quick study guide for pilots.
FAR 21.91 is a short "applicability" section that simply tells you what Subpart D of Part 21 covers. It states that this subpart prescribes the procedural requirements for the approval of changes to type certificates.
In plain terms:
- A type certificate (TC) is the FAA's approval of an aircraft, engine, or propeller design.
- When a manufacturer (or anyone else) wants to change that approved design, they can't just do it — the FAA has a defined approval process.
- Subpart D, beginning at 21.91, lays out how those design changes get reviewed and approved.
Why it matters operationally: as a pilot, you fly aircraft built and modified under these rules. Major design changes either result in an amended type certificate or a supplemental type certificate (STC). Knowing that 21.91 is the gateway to Subpart D helps you understand where airworthiness changes — like new engines, avionics, or structural mods — are governed in the regulations.
Five FAA-written-style questions. Instant explanations, every answer cites its source — no account needed.
You are flying VFR in Class E airspace at 8,500 feet MSL during the day. What are your minimum visibility and cloud clearance requirements?