Definition
On the vertical speed indicator (VSI), 'descending' or 'down' refers to the indication shown when the aircraft is losing altitude. The VSI needle moves below the zero index, and the rate of descent is read in feet per minute (fpm).
Plain English
The aircraft is going down. On the VSI, the needle points below zero and shows how fast you are losing altitude in feet per minute.
Context Anchor
Seen on the Vertical Speed Indicator when checking whether the aircraft is climbing, level, or descending.
Derivation
From Latin 'descendere' — 'de-' (down) + 'scandere' (to climb). Literally 'to climb downward.' The aviation use keeps the everyday meaning: moving from a higher altitude to a lower one.
Why Pilots Care
Knowing the rate of descent is critical during approaches, level-offs, and emergency descents. Too fast a descent rate can mean overshooting an altitude or arriving too low; too slow can mean missing a crossing restriction.
Intuition Check
Descending does not necessarily mean the nose is pointed down. In this context, it means the aircraft’s altitude is decreasing.
Example Sentence 1
After leveling at cruise, the pilot reduced power and the VSI showed descending at 500 feet per minute.
Example Sentence 2
To stop the descent, the pilot applied power and raised the nose until the VSI needle returned to zero.