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Calcimator

Emergency Descent Calculator

Emergency descent time, distance, and time of useful consciousness for rapid decompression scenarios.

Inputs

Results

Descent time (min)

3.8

Time of useful consciousness (sec)

210

Descent time (sec)225
Horizontal distance (NM)15.2
Groundspeed (kts)243
True airspeed (kts)243
Turn radius (NM)0
O2 remaining (min)63
Completes before TUC (1=Yes)0
How to Use This Calculator
  1. Enter your current altitude (ft) and target altitude (ft) for the emergency descent.
  2. Set the planned descent rate (fpm) and indicated airspeed (kts) during the descent.
  3. Enter headwind component (kts) and bank angle if turning during descent.
  4. Review time to descend (minutes and seconds), horizontal distance covered (NM), and groundspeed.
  5. Compare time of useful consciousness (TUC) to descent time for rapid decompression emergencies.

How the result changes with Current altitude (ft)

Current altitude (ft)Descent time (min)Time of useful consciousness (sec)
6,000099,999
21,0002.8600
39,0007.345
54,0001118

What each input means

Current altitude (ft)
Altitude when emergency descent begins.
Target altitude (ft)
Safe altitude to descend to (typically 10,000 ft or MEA).
Descent rate (fpm)
Target vertical speed for the emergency descent.
Indicated airspeed (kts)
Airspeed during the descent (below Vne/Vmo).
Headwind (kts, neg=tail)
Headwind component. Negative = tailwind.
Bank angle (degrees)
Bank angle if executing a turning descent.
O2 pressure (PSI)
Remaining supplemental oxygen cylinder pressure.
O2 flow rate (L/min)
Oxygen flow rate in liters per minute.

What each result means

Descent time (min)
Time required to reach the target altitude.
Descent time (sec)
Descent time in seconds for comparison with TUC.
Time of useful consciousness (sec)
Approximate TUC at the starting altitude without supplemental O2.
Horizontal distance (NM)
Ground distance covered during the descent.
Groundspeed (kts)
Estimated groundspeed during descent.
True airspeed (kts)
TAS corrected for altitude.
Turn radius (NM)
Turn radius if banked (0 = wings level).
O2 remaining (min)
Supplemental oxygen duration at current flow rate.
Completes before TUC (1=Yes)
1 if descent completes within time of useful consciousness.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Current altitude (ft) = 25000, Target altitude (ft) = 10000, Descent rate (fpm) = 4000, Indicated airspeed (kts) = 180 = 8 input(s) provided
  2. Calculate Descent time
    Descent time = altitudeLoss / descentRateFpm
    3.8 = 3.8
  3. Calculate Time of useful consciousness
    Time of useful consciousness = Infinity
    210 = 210
  4. Calculate Descent time
    Descent time = descentTimeMin * 60
    225 = 225
  5. Calculate Horizontal distance
    Horizontal distance = (groundspeedKts / 60) * descentTimeMin
    15.2 = 15.2

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