Definition
A descent rate that is too high for the aircraft's current altitude above the ground, triggering a Mode 1 alert in a Ground Proximity Warning System (GPWS) or Terrain Awareness and Warning System (TAWS). The system evaluates vertical speed against radio altitude and issues a 'SINKRATE' caution followed by a 'PULL UP' warning if the rate continues to be unsafe relative to height above terrain.
Plain English
The aircraft is going down too fast for how close it is to the ground. The terrain warning system flags this as dangerous and tells the pilot to stop descending so quickly.
Context Anchor
You encounter this term in terrain alerting system discussions and in cockpit warnings such as “Sink rate” or “Pull up.”
Derivation
“Descent” means going downward, and “rate” means how much something changes over time. Together, “descent rate” means how fast the aircraft is going down; “excessive” means that speed downward is too much for the situation.
Why Pilots Care
Alerts the crew in time to arrest the descent and prevent controlled flight into terrain.
Grounding Statement
A fast descent may be normal when the aircraft is high, but the same downward speed can be dangerous when the ground is close.
Intuition Check
Do not read “excessive” as a fixed number that is always unsafe. Here it means the descent is too fast for the aircraft’s height above the ground and the situation at that moment.
Example Sentence 1
On final approach the GPWS announced 'SINKRATE,' alerting the crew to an excessive descent rate, and the pilot reduced the rate of descent immediately.
Example Sentence 2
The pilot reduced power and raised the nose to correct the excessive descent rate before the terrain alert sounded.