What does a displayed rate of cabin altitude change of -500 indicate?

A displayed rate of cabin altitude change of -500 indicates that the cabin altitude is decreasing at a rate of 500 feet per minute. This is significant because it allows the crew and passengers to understand that the cabin is descending in altitude, which typically occurs during descent phases of flight. A negative rate indicates that the cabin is dropping, aligning with the operational requirements for altitude management in the aircraft.

In the context of aviation safety and comfort, understanding these rates is crucial, as it directly impacts cabin pressure and passenger experience. While increasing altitude would show a positive rate, a stable altitude would indicate no change (represented by a rate of zero), and an emergency descent would typically be characterized by a much higher negative rate of descent and additional indications, such as alerts. Therefore, a rate change of -500 specifically denotes a controlled and safe descent of cabin altitude.