Descent planning (top of descent)

Top of descent: point along track to start down, to arrive level at planned rate.

1. Descent time (min) = altitude to lose (ft) / rate of descent (ft/min).
2. Descent distance (nm) = groundspeed (kt) x descent time (min) / 60.

Worked example (TP 1102):

• Lose 6,000 ft at 500 ft/min = 12 min.
• At 120 kt (2 nm/min): start descent 24 NM before airport.

Trap: reporting descent TIME (min) as distance (nm); still multiply by groundspeed.

Practice