“Is there a way to compute the strength of up- and downdrafts based on the amount of increase or decrease in airspeed? If I’m cruising along at an indicated 135 knots with a constant power setting, maintaining altitude and see my airspeed decrease to 110 knots as I pitch up to overcome downdrafts while maintaining altitude and power, it seems there should be some way to calculate the strength of those downdrafts based on the loss of airspeed. Coming out of the downdraft and into an updraft would have the reverse effect, with maybe 155 knots or so the resulting airspeed as the airplane pitches down to maintain altitude. I thought this might be a simple right-triangle problem, but the more I think about it, the more it seems like it’s probably more complicated than that.”
Technicalities: How to Calculate the ‘Strength’ of an Updraft
Key Takeaways:
- It is possible to calculate the strength of up- and downdrafts based on observed changes in airspeed while maintaining altitude and constant engine power.
- This calculation works by treating the vertical air movement as an equivalent gain (updraft) or loss (downdraft) of horsepower for the airplane, directly impacting its speed.
- By quantifying this effective horsepower change from the airspeed difference (using a rough cubic relationship between speed and power), pilots can estimate the vertical velocity of the air mass.
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