14 C.F.R. § 63.19 Operations during physical deficiency.
Title 14 - Aeronautics and Space
No person may serve as a flight engineer or flight navigator during a period of known physical deficiency, or increase in physical deficiency, that would make him unable to meet the physical requirements for his current medical certificate.
Title 14: Aeronautics and Space
PART 63—CERTIFICATION: FLIGHT CREWMEMBERS OTHER THAN PILOTS
Subpart A—General
§ 63.19 Operations during physical deficiency.
