Plane & Pilot
Tuesday, September 24, 2013

Beware The Fickle Winds

Winds almost never play fair

Question is, how long do you wait for the tailwinds to materialize? There's no simple answer, as wind patterns aren't consistent.

On what was to become my last Mooney trip, the wind finally did start to turn, but much later than I had expected. I was grateful that the MSE can still generate good speed at reduced power. The winds weren't quite up to the forecaster's promise, and I eventually diverted to Hilo, 60 miles closer than Honolulu. I still landed with an hour's reserve.

Contrary to what some cynics allege, tailwinds do happen, even in the most unlikely scenarios, but they're more typical up high than down low. Winds of any significance aren't much of a factor in the bottom 5,000 feet of sky. Simple friction of the Earth's atmosphere with the ground tends to nullify the effect of winds less than five knots, regardless of whether they're plus or minus.

And when we do have headwinds, we tend to remember them longer than we recall tailwinds. Then, too, headwinds act on the airplane longer than do equivalent tailwinds, an automatic disadvantage that means equivalent head and tail winds don't cancel each other. Also, tailwinds only apply through about the aft 170 degrees, whereas headwinds operate in the forward 190 degrees.

I'm aware that some pilots have had such a bad experience with winds that they assume they'll never see tailwinds. It's almost analogous to Murphy's First Law of Lane Choice—the lane you're in will always be the slowest, and the first corollary: If you change lanes, your new lane will automatically become the slowest.

I once flew a Cessna 414 Chancellor the other way, from Honolulu to Van Nuys. It was summer, perhaps the worst time to be eastbound, but to my surprise, I had tailwinds all the way, and managed to average well over 250 knots at 19,000 feet.

Just as with life, airline fares and the IRS, don't expect head- or tailwinds to be fair, make sense or have any sympathy. Learn to live with them, and accept the fact that you may never realize tailwinds as strong as headwinds.


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