Tuesday, May 25, 2010
The Myth (Almost) Of Tailwinds
Logic suggests you should have tailwinds roughly 50% of the time. Logic is wrong.
I’m based in Southern California, so I typically start off from Santa Barbara with direct headwinds, then watch the wind gradually shift around clockwise to the tail about 1,200 nm out. If I can expedite that shift a few hundred miles sooner, then it might be smart to depart farther north along the California coast or route slightly north of a great circle to Hilo or Honolulu.
In fact, no matter how long the leg, you can help alleviate the effect of headwinds or take advantage of tailwinds from the moment you leave the ground. If I’m in a turbine and climbing into headwinds, I’ll sometimes use a cruise climb to allow me better forward speed. If the winds are going my way, I’ll use a slower, near-Vy climb to gain maximum altitude as quickly as possible.
At the opposite end of the flight, I’ll maintain height as long as possible in strong tailwinds, then descend at a high rate. I’ll reduce altitude more leisurely in headwinds. The advantage may be small, but with turbines or even a big piston single, a few minutes saved can be a significant advantage.
Make no mistake about it, tailwinds do exist, though they’re rarely available when and where you want them, and they’re almost never as strong as forecast. An old-time ferry pilot (probably named Murphy) once imparted a rule I find helpful and more accurate than the weatherman’s best guess. Cut any forecast tailwinds in half and add at least half to any predicted headwinds. It usually works for me.
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