FAR 21.187 — Multiple Airworthiness Certificates
FAR 21.187 explains how restricted category aircraft can hold multiple airworthiness certifications, conversion rules, and required FAA inspections.
FAR 21.187 allows an aircraft to hold an airworthiness certificate in the restricted category along with one or more other categories — except primary category. This is useful for operators who use the same airframe for different missions, such as agricultural spraying one day and a different operation the next.
To qualify, the applicant must show:
- Compliance with the requirements of each category when the aircraft is configured for that category.
- The aircraft can be converted between categories by adding or removing equipment using simple mechanical means.
- Compliance with Part 34 (fuel venting and exhaust emissions).
- For airplanes, compliance with Part 38 (fuel efficiency).
Operationally, every time the aircraft is converted from restricted category to another category for carrying passengers for compensation or hire, it must be inspected for airworthiness by the FAA or a certificated mechanic with an appropriate airframe rating, unless the FAA decides the inspection is unnecessary for safety. This protects paying passengers from being flown in an aircraft still configured for restricted-category work.