FAA Aviation Mechanic Airframe (AMA)Fuel, Cabin and Ice Control SystemsMedium
A technician functionally tests the cabin pressurization controller on a transport-category aircraft. During a climb, the cabin altitude changes from sea level to 4,000 feet in 10 minutes. What is the cabin rate of climb, and how does this compare to the typical maximum allowable rate for passenger comfort?
- A4,000 fpm, which greatly exceeds the typical comfort limit
- B400 fpm, which is within the typical 500 fpm maximum comfort limit
- C40 fpm, which is far below the minimum required rate
- D800 fpm, which exceeds the typical comfort limit by 300 fpm
Show answer & explanationAnswer & explanation
Correct answer: B. 400 fpm, which is within the typical 500 fpm maximum comfort limit
Rate = altitude change ÷ time = 4,000 ft ÷ 10 min = 400 fpm. This is within the commonly used cabin rate-of-climb limit of about 500 fpm designed for passenger ear comfort, controlled by the cabin pressure controller's outflow valve modulation.
Why the other options are wrong
- A. Misplaces the decimal; 4,000 fpm would be an extreme, unrealistic rate.
- C. Incorrect division; 4,000/10 is 400, not 40.
- D. Incorrect calculation; does not match the given numbers.
Cabin Rate of Climb Control
The pressurization controller modulates the outflow valve to limit how fast cabin altitude changes, typically to about 500 fpm for passenger comfort.
- Rate = cabin altitude change ÷ time
- Typical maximum comfort rate is around 500 fpm
- Controlled by outflow valve modulation via the cabin pressure controller
Memory trick: Ears like it slow—500 fpm or less keeps passengers happy.