I would like to verify if these formulas are correct with regards to calculating the descent.
Let's say, for instance, I'm flying a 777-300ER from London to Paris (2 hours flight).
1) Intitial Descent
T/D = Current Altitude * 3 - Airport Elevation = ANS / 1,000 = FINAL ANS
2) Descent Rate
TAS / 2 = ANS * 10 = ft. per min
3) Initial Descent (Alternate method)
*Constantly check V/S every 10,000ft
- Altitude
Current Altitude(3 digits only) / 3 = NM (ex. 27,0(00)/3 = 90 NM)
- Speed
*1 NM per 10 kts speed reduction
Current Speed - Average Speed(200 kts) / 10 (ex. 320 - 120 = 200 / 10 = 12 NM)
- Wind
*For every 10kts of wind, add 1NM (ex. 20kts(tailwind) / 10kts = 2NM)
Alt 90NM
Speed 12NM
Wind 2NM
= T/D 104NM
4) Descent Rate (Alternate method)
GS * 5 = feet/min (V/S)
Sources:
