The cabin altimeter assembly includes which meters?

• A. Cabin altitude meter and cabin pressure differential meter
• B. Outside air temperature gauge and cabin pressure gauge
• C. Airspeed indicator and vertical speed indicator
• D. Oxygen concentration gauge and humidity indicator

Answer: (A)

The essential idea is monitoring the cabin’s pressurization. In a pressurized aircraft you need to know two things: what the cabin’s altitude is and how much the cabin pressure differs from the outside air. The cabin altitude meter shows the altitude inside the cabin, so you can verify the pressurization level is within safe limits. The cabin pressure differential meter (the differential pressure gauge) measures the difference between inside and outside pressure, ensuring you stay within structural and passenger comfort limits and detect leaks or system faults.

The other instruments listed aren’t part of the cabin altimeter assembly: outside air temperature gauges measure external temperature, which isn’t about cabin pressurization; airspeed and vertical speed indicators are flight instruments for flight path and speed; oxygen concentration and humidity gauges relate to air quality, not the pressurization status.