FAA Aircraft Dispatcher (ADX)Regulations (Part 121)Medium
A pressurized Part 121 airplane cruises for 45 minutes at a cabin pressure altitude of 13,000 feet MSL. Under 14 CFR 121.333, what is the minimum supplemental oxygen requirement?
- AOxygen for the flight crew only, for that portion of flight exceeding 30 minutes
- BOxygen for the entire flight crew for the whole time at that altitude, and for at least 10% of the occupants of the passenger compartment
- COxygen for every occupant of the airplane, crew and passengers alike
- DNo supplemental oxygen is required below 14,000 feet cabin pressure altitude
Show answer & explanationAnswer & explanation
Correct answer: B. Oxygen for the entire flight crew for the whole time at that altitude, and for at least 10% of the occupants of the passenger compartment
Under 121.333(c)(2), for pressurized airplanes at cabin pressure altitudes above 12,000 through 15,000 feet MSL, oxygen must be provided for and used by the entire flight crew for the entire time at that altitude, and at least 10 percent of the occupants of the passenger compartment must be provided oxygen for that time.
Why the other options are wrong
- A. That 30-minute crew-only threshold applies to the 10,000-12,000 foot band, not 12,000-15,000.
- C. All-occupant oxygen is required above 15,000 feet, not at 13,000 feet.
- D. Oxygen requirements begin above 10,000 feet cabin pressure altitude for extended duration flight.
Passenger/Crew Oxygen Tiers (121.333)
Establishes supplemental oxygen requirements for pressurized airplanes based on cabin pressure altitude bands.
- 10,000-12,000 ft: crew oxygen if over 30 min
- 12,000-15,000 ft: crew oxygen + 10% passengers, entire time
- Above 15,000 ft: oxygen for all occupants
Memory trick: "Ten-Twelve-Thirty, Twelve-Fifteen-Ten-Percent, Fifteen-Plus-Everyone."