Definition
A vertical speed indicator that uses an internal accelerometer-driven pump (typically a pair of small piston pumps) to sense vertical acceleration and immediately reflect changes in the rate of climb or descent, eliminating the lag found in a standard vertical speed indicator.
Plain English
A climb-and-descent gauge that responds right away when you start going up or down, instead of taking several seconds to catch up like a normal one.
Context Anchor
Seen on aircraft instrument panels and in instrument-flying discussions where quick recognition of climbing or descending matters.
Derivation
‘Instantaneous’ comes from Latin instans, meaning ‘at this moment.’ The name reflects what makes this instrument different from a standard vertical speed indicator: it shows the change at the moment it happens, not a few seconds later.
Why Pilots Care
Provides immediate feedback on vertical speed for precise altitude control and smooth flight path management.
Intuition Check
Do not read “instantaneous” as perfectly instant or predictive. It means the instrument is designed to reduce lag and show the current climb or descent rate sooner than a standard indicator.
Example Sentence 1
Leveling off at the assigned altitude was easier in this aircraft because the instantaneous rate of climb indicator caught the trend early.
Example Sentence 2
On final approach the instantaneous rate of climb indicator helped fine-tune the descent rate to stay on the glide path.