Descent from FL370 to
FL80 is through 29,000ft and at 1,800ft/min this will take 16.1
minutes.
In 16.1 minutes the
aircraft will cover 62.3nm at its ground speed in the descent of
232kts.
At 0422 distance to run
to top of descent is 184 – 62.3 = 122.7nm and at cruise ground speed of 320kts
this will take 23 minutes.
Commence descent at 0422
+ 23min = 0445.