Definition
The aircraft's speed across the ground during a descent, measured in knots and used to calculate how far the aircraft will travel during the descent and how long the descent will take. Descent groundspeed is true airspeed adjusted for the wind component along the flight path, and it is the value used in descent planning calculations such as top-of-descent point and rate of descent in feet per minute.
Plain English
How fast the aircraft is actually moving over the ground while going down. It's not how fast you're going through the air — it's how fast the runway is approaching beneath you, taking the wind into account.
Context Anchor
Used in instrument descent planning when deciding when to start down and how fast to descend.
Why Pilots Care
It directly determines how far the aircraft will travel while losing altitude, ensuring the pilot reaches the next altitude restriction or final approach fix at the right point.
Intuition Check
Do not assume descent groundspeed is the same as airspeed. A headwind lowers descent groundspeed, and a tailwind increases it.
Example Sentence 1
With a descent groundspeed of 300 knots and 30 miles to lose 9,000 feet, the pilot calculated a required rate of descent of 1,500 feet per minute.
Example Sentence 2
A strong tailwind increased descent groundspeed and shortened the distance needed to reach the crossing altitude.