The Brandon Method

December, 2, 2020 by ,

By definition, the top of descent (or TD) is the point at which an aircraft initiates a descent to a lower level for arrival at its destination airport. Every pilot should know when s/he should start to descend and how to adjust the rate accordingly. Your ability to quickly calculate your top of descent is useful both in real-world aviation and in Infinite Flight.

Here is my preferred method of how to quickly calculate your top of descent (TD):

  • Your current ALT (a)
  • Subtract destination airport’s elevation (b)
  • Multiply that sum by 3.
  • The given product is (c)
  • Divide (c) by 1000.
  • And voila, your (d)!

TD = a – b (3)
TD = c /1000
TD ~ (d)

Example:  30000 – 100 = 29900   =>  29900 x 3 = 89700   =>  89700/1000 = 89.7
Thus, your TD ~ 90NM (Your destination ICAO is ± 9NM, just enough time for your final checks)

Brandon is a writer for the IFATC Education Group. He is also a Commander in the U.S. Navy Reserve and holds a PPL.