FAA Flight Instructor Airplane (FIA)Regulations (14 CFR 61/91)Medium
An unpressurized airplane is flown at a cabin pressure altitude of 13,500 feet MSL for a total duration of 45 minutes. According to 14 CFR 91.211, what supplemental oxygen requirement applies to the required minimum flight crew?
- ANo oxygen is required because the altitude is below 14,000 feet MSL
- BOxygen must be provided to all occupants but is optional for the crew
- COxygen is required only if the flight exceeds 3 hours at that altitude
- DThe flight crew must use supplemental oxygen for that part of the flight at that altitude exceeding 30 minutes
Show answer & explanationAnswer & explanation
Correct answer: D. The flight crew must use supplemental oxygen for that part of the flight at that altitude exceeding 30 minutes
14 CFR 91.211(a)(1) requires that at cabin pressure altitudes above 12,500 feet MSL up to and including 14,000 feet MSL, the required minimum flight crew use supplemental oxygen for that part of the flight at those altitudes that is of more than 30 minutes duration. Since the flight is at 13,500 feet for 45 minutes, oxygen is required after the first 30 minutes.
Why the other options are wrong
- A. Incorrect — the 12,500–14,000 ft band still triggers a 30-minute rule.
- B. Crew oxygen use is mandatory, not optional, once the 30-minute threshold is exceeded.
- C. 3 hours is not a threshold found in 91.211.
Supplemental Oxygen (91.211)
FAR 91.211 sets crew and passenger oxygen requirements based on cabin pressure altitude and duration of exposure.
- 12,500-14,000 ft: crew oxygen after 30 min
- Above 14,000 ft: crew oxygen at all times
- Above 15,000 ft: oxygen must be available to each occupant
Memory trick: '12-30, 14-always, 15-everyone' for oxygen tiers.