How to use this calculator
- Enter altitude to lose. Use altitude above the target crossing or pattern altitude.
- Enter ground speed. Use expected wind-corrected ground speed.
- Enter descent rate. Use the planned vertical speed.
- Check target path. Compare actual angle with the target path angle.
How it works
Descent time is altitude / descent rate, and distance is ground speed x time. Required descent rate for the target path is ground speed x tan(path angle).
Continue with true airspeed, wind components and range and endurance.
Worked example
Verified against the live calculator
Losing 3,000 ft at 700 ft/min and 120 kt groundspeed takes about 4.3 minutes and starts roughly 8.6 NM back.
Frequently asked questions
How is top-of-descent distance calculated?
The calculator divides altitude to lose by descent rate to get time, then multiplies by ground speed to get distance.
Why use ground speed?
Descent distance is distance over the ground, so wind-corrected ground speed matters.
What does required descent rate mean?
It is the vertical speed needed to fly the target path angle at the entered ground speed.
Does this replace a procedure descent profile?
No. Published restrictions, clearances and stabilized-approach criteria control.
Method & assumptions
- Assumes constant ground speed and vertical speed over the checked segment.
- Does not replace ATC clearances, charted restrictions, terrain clearance, aircraft procedures or stabilized-approach gates.