Which instrument indicates the difference between inside and outside pressure in an aircraft?

The cabin differential pressure gauge is the instrument specifically designed to indicate the difference between the pressure inside the aircraft cabin and the pressure of the outside atmosphere. This gauge provides critical information regarding the cabin's pressurization state, which is essential for ensuring passenger comfort and safety at high altitudes.

When an aircraft climbs, the outside air pressure decreases while the cabin is pressurized to maintain a comfortable environment for passengers and crew. The differential pressure is a key parameter that flight engineers monitor closely to ensure that it stays within safe limits. If the differential pressure exceeds specified thresholds, it could indicate potential problems with the cabin pressurization system, leading to possible safety issues.

In contrast, while the cabin altimeter indicates the altitude of the aircraft based on internal pressure, it does not measure the specific pressure differential between inside and outside. The rate of climb indicator provides information regarding the vertical speed of the aircraft but does not concern itself with pressure differences. The pressurization controller is responsible for maintaining the appropriate cabin pressure but does not measure the differential itself. Therefore, the cabin differential pressure gauge is the right instrument for indicating the pressure difference vital for safe flight operations.