FAA Aircraft Dispatcher (ADX)Regulations (Part 121)Hard
A Part 121 turbine-powered airplane is cruising at FL350. Under 14 CFR 121.578, what is the maximum allowable cabin ozone concentration at any time while operating above FL320?
- A0.10 ppm by volume, sea level equivalent, as a 3-hour time-weighted average
- B0.50 ppm by volume, sea level equivalent, at any time
- C0.25 ppm by volume, sea level equivalent, at any time
- DThere is no ozone concentration limit above FL320
Show answer & explanationAnswer & explanation
Correct answer: C. 0.25 ppm by volume, sea level equivalent, at any time
14 CFR 121.578 limits cabin ozone concentration to no more than 0.25 ppm by volume (sea level equivalent) at any time when the airplane is operated above FL320. A separate limit of 0.1 ppm applies as a 3-hour time-weighted average above FL270.
Why the other options are wrong
- A. This is the 3-hour time-weighted average limit above FL270, not the instantaneous limit above FL320.
- B. 0.50 ppm exceeds the regulatory maximum.
- D. 121.578 does establish specific ozone concentration limits.
Cabin Ozone Concentration (121.578)
Regulation limiting cabin ozone exposure: 0.25 ppm maximum at any time above FL320, and 0.1 ppm time-weighted average over any 3-hour period above FL270.
- 0.25 ppm instantaneous limit above FL320
- 0.1 ppm 3-hour average limit above FL270
- Sea-level equivalent, by volume measurements
Memory trick: 'Twenty-five hundredths at the top, ten hundredths over time.'