FAR 91.191 — Category II/III Manual
FAR 91.191 requires a current, approved Category II/III manual on board, compliance with its procedures, and proper inspection of listed equipment.
FAR 91.191 sets the manual and equipment rules for flying a U.S.-registered civil aircraft in Category II or Category III approach operations (low-visibility ILS approaches below standard CAT I minimums).
To conduct a CAT II or CAT III operation, you must have:
- A current and approved Category II or III manual on board the aircraft for that specific aircraft;
- Operations conducted strictly in accordance with the procedures, instructions, and limitations in that manual; and
- All instruments and equipment listed in the manual as required for the operation inspected and maintained under the manual's maintenance program.
The operator must also keep a current copy of each approved manual at its principal base of operations and make it available to the FAA on request.
This matters operationally because CAT II/III operations rely on tightly controlled aircraft systems and crew procedures — the manual is what makes the operation legal and safe. Note: this section does not apply to Part 121, Part 135, or Subpart K (fractional) operators, who follow their own approved programs.