The Diabolical Winds

Case in point: a recent trip from Torrance, Calif., to Deer Valley, Ariz., a suburb of Phoenix. The distance was only a little over 300 nm, and Dr. Van Steed and I launched his Bonanza early so we could return home in the early afternoon. The briefer suggested there were Santa Ana winds blowing in from the east, but neither he nor I expected that they'd be as strong as 50 knots.

We stayed relatively low for the outbound leg, grumbling about the turbulence, but the Bonanza's normal, 170-knot cruise was sometimes reduced to a miserable 110-knot groundspeed. The indignity of it all: two hours and 37 minutes for 317 nm. Oh well, I reasoned, at least we'd see some spectacular speeds on the way home.

Wrong! When we departed Deer Valley at 1:30 that afternoon and headed west, I was dismayed to see that we were only benefiting from about a 10-knot to 15-knot tail wind component. The wind had shifted farther north and died down as the day went on, an unusual condition. That 15-knot push still put our groundspeed well over 180 knots, but it wasn't nearly enough to offset the morning's head winds.

No one ever promised the wind would be fair. I, of all people, should know that tail winds almost never offset head winds, even in those rare instances when the wind remains consistent in both heading and velocity. Do the math, and you'll see you can't make up the time lost to a head wind with the same tail wind. In fact, any consistent wind on a round-trip flight will always hurt you, although not necessarily by much.

That's because any tail wind will never save as much time as an equivalent head wind will lose. The reason is almost silly simple. A head wind acts longer on the airplane than a tail wind does. Pretty obviously, the faster an airplane cruises, the less effect a given wind will have. That's one reason the airlines can maintain schedules most of the time with little concern for wind. An increase in wind speed from 30 to 50 knots won't have much effect on a 450-knot jet.

Winds mean more to those of us who operate in the speed regime below 250 knots. To keep the numbers simple, assume a 100-knot airplane over a 100-nm course with a 20-knot head wind and tail wind as an example. In the tail wind direction, the airplane will cover the 100 nm in 50 minutes. Flying the opposite direction, the same airplane will require 75 minutes for the trip. That's two hours and five minutes total for a trip that theoretically would require an even two hours in no-wind conditions.

In a similar sense, you don't benefit from an angling head or tail wind. Even a direct crosswind will resolve to a slight head wind. You may barely notice it in light winds, but you'll lose some speed with wind from any direction on a round-trip flight.

Of course, another reason why head winds seem more common than tail winds is purely psychological---we remember head winds longer. It's analogous to what I like to call Murphy's Law of Freeway Lane Choice---whichever lane you're in will always be the slowest. (The first corollary to this law is should you change lanes, the new one will become the slowest.) Just as with head winds, we notice slow or stopped traffic more and pay little attention to travel at normal speeds.

There are a few things you can do to minimize the effect of wind. One is to flight plan for the highest altitude possible on the tail wind leg to take maximum advantage of as much tail wind as you can get, even jumping to oxygen heights if you have the capability. When flying beneath a broken cloud layer, you might try borrowing a page from sailplane pilots who always try to stay beneath the clouds and avoid the "blue holes" between clouds whenever possible. This will keep you in updrafts most of the time and help optimize your speed. Conversely, terrain and turbulence permitting, consider flying the head wind leg at as low an altitude as is safe and comfortable to reduce head wind exposure.

Another trick that can partially offset the effects of a head wind is to use a higher power setting, consistent with the manufacturer's recommendations, of course. Power is a notoriously inefficient method for increasing speed, but if burn, range and fuel availability aren't problems, flying faster can ease the pain of a head wind.

Weather and nasty crosswinds above the airplane's demonstrated limit are legitimate reasons not to go, but pilots don't normally allow the wind to limit their airplane's utility. To that end, another possibility when you have a choice is to fly head wind legs in the morning when winds tend to be slightly lighter. That leaves the higher tail wind leg for the afternoon when winds are stronger, thereby maximizing your advantage. That technique dovetails nicely with good turbulence planning as well, as the chop typically builds as the day wears on, and the greater height should help insulate you from the chop.

Fly through passes in mountainous terrain where venturi-fed winds can be fickle and unpredictable, and all bets are off. Additionally, head winds in one direction may not always translate to tail winds in the opposite heading because of a number of factors: the vagaries of terrain, the inconsistencies of orographic heating, the phase of the moon and your astrological sign.

Just as with life, airline fares and the IRS don't expect head winds or tail winds to be fair, to make sense or to have any sympathy. Learn to live with them and accept the fact that no matter how good you think you are, how many hours or ratings you have or who you took your last biennial flight review with, you'll never realize as much tail wind as you do head wind.

Bill Cox is entering his third decade as a senior contributor to Plane & Pilot® and provides consulting for media, entertainment and aviation concerns worldwide.
E-mail him at flybillcox@aol.com.