Flying in Wind

Part III: Crossing Winds

by Dennis Pagen

: We conclude our mini-series on flying in wind with crosswind flying. We started with downwind flying, followed by upwind flight, and will now complete the picture with trying to cut across the wind. We left the crosswind track to last because it is a bit more complicated than flying with the wind directly on our tail or our nose. Because of this complication, we will divide the discussion into a part for beginners, one for intermediates, and one for sky heroes. Readers can decide which part(s) best suits their needs. We’ll add that the considerations and practices apply to both paragliding and hang gliding.

Crosswind Flying For Newbies

In almost all cases, our early flying involves heading straight into the wind on a training hill and then perhaps flying higher with a landing field directly in front of us. In fact, you may only experience crosswind flying once you have a good number of high flights, especially if your early high flights are limited to morning or evening light-winders. But eventually, you will need to fly across the wind, both on landing setup and possibly when heading to a field that is not directly upwind of takeoff.

So here’s how you do it: imagine you wish to fly from point A to B in Figure 1. If you had enough height, you could certainly go all over the map before arriving at point B. Still, we’ll assume we must make our little transit as short as possible, or more usual to our situation, with as little altitude loss as possible. We can also call this flying as efficiently as possible or getting to our destination as high as possible. All these descriptions mean the same thing.

mined by how fast we are flying compared to how strong the wind flow is. The stronger the wind, the more we have to aim into it. If a paraglider flies at a slower airspeed than a hang glider, the pilot of the paraglider must turn into the wind more in order to create the direct ground path shown.

The combination of our forward airspeed and the wind produces a ground path that appears to be moving sideways to our heading. Flying in this manner is often called “crabbing” because we mimic the motion of a crab scuttling sideways. In addition, the angle we make with our ground path is called the “crab angle.” The stronger the crosswind, the higher our crab angle must be to describe a perfectly straight path from A to B.

In both figures, we have drawn a boat crossing a flowing river to help you visualize the motion in a flowing stream of air or water. In the case of the boat, the same paths result—curving and inefficient if the nose is constantly pointed at the target and direct with an applied crab angle a bit upstream. As mentioned, a glider can run out of altitude when following an inefficient path. A boat doesn’t have altitude to lose, but it can run out of fuel, which is a similar disaster.

Here is how to fly the most efficient path: the minute you expect or detect a crosswind in your flight, angle a bit into the wind and look at your target. If you aren’t moving directly at it, make a little turn control to head more or less into the wind so your path is direct to the goal. We recommend drawing an imaginary line along the ground from where you are to your goal. Locate a few points along this path on the ground, like a tree, building, or field corner, to guide you, then try to pass above each point as you progress. This technique is especially useful on higher flights where the ground barely seems to move under you. Note that the crosswind factor can change along the course of your flight, especially if the goal is far away; perhaps you are passing different hills diverting the flow, or you descend into lighter winds. Expect to make adjustments along the way. Eventually, you will develop the skill and judgment to automatically set and adjust your crab angle by simply looking at your target and flying along. That’s part of moving up in skill level.

Intermediate Crosswind Matters

As we gain abilities in the air, we may fly higher and with more wind. Crosswind flying becomes common as we set up landings, attempt early cross-countries, or simply fly around in different directions looking for thermals or lift sources. But the most common crosswind flying occurs when we are ridge soaring. In many places, especially with lower hills or fewer thermals (the green East Coast, for example), a pilot’s first soaring often takes place in ridge lift with substantial wind.

Hopefully, at this point the pilot is familiar with the principles of crosswind flying, if not practiced. Still, most pilots on their first ridge soaring attempts need guidance to help keep them safely away from the hill and in the most effective lift area. Figure 3, on the following page, shows a top view of a pilot’s soaring flight path from takeoff. We can see that a pilot must turn soon after launch to remain in the lift band. Typically, a very new pilot turns too late and misses the lift or is in light lift that doesn’t sustain them, so they sink and have to move away from the hill, which results in an extended sled ride. This path is also labeled in the figure.

However, turning too soon can result in getting too close to the hill, presenting the danger of a crash. It may take a pilot several attempts at ridge soaring to get the initial turn correct. Ideally, this first turn sets the pilot up in the meat of the lifting area while setting the perfect crab angle for the current wind strength (as shown in the figure). An experienced pilot will do the launch, turn, and make adjustments automatically. This perfection should be the goal of all advancing pilots.

Note that once our crab angle is set, we can’t assume our job is done for the flight. As we climb higher, we may wish to move downwind to be a bit over the ridge for better lift, or to move out to intercept a thermal. As we climb higher, we may enter stronger wind, which requires pointing more into it (many of us have climbed into stronger winds to the height where we are pointing directly into the wind and can no longer make headway left or right along the ridge).

In other situations, we may alter our crab angle to follow a ridge that drops back or juts forward. In addition, we may cross a gap that allows the wind to flow faster through it, so we may have to angle more into the wind to combat this effect or even fly a bit upwind of the gap to avoid its effects. Accumulated flight experience, awareness, and practice will lead to all these adjustments being performed automatically with very little input from your cerebral cortex required.

Advanced Crosswinds

Of course, all the preceding applies to advanced pilots and learners. We may think that advanced pilots fly in stronger winds, requiring even more crab angle, but in practice, really advanced pilots tend to fly in lesser winds because strong winds blow apart thermals and raise the risk level. The real advanced crosswind skill comes into play when a pilot constantly alters their path to take advantage of lift lines, potential thermal sources, or horizontal jets, as well as cross to a better cloud street while avoiding blue holes and treacherous areas. For the most part, we are describing flights that take place in competitions, but personal cross-country flights also involve the course alteration and decision-making we allude to. These constant course alterations, when done well, are what distinguishes a great pilot from the rest of us.

But there is one other important crosswind skill: speed-to-fly. We don’t have space to fully explain all speed-to-fly concepts, but suffice it to say that for best efficiency or minimum altitude loss for distance traveled, there is an ideal speed to fly for every different combination of lift, sink, headwind, tailwind, or crosswind. We often leave out the crosswind factor because it is so complex.

But imagine this: you are flying along in a 90-degree crosswind and wish to go as far as possible, losing as little altitude as possible. If you speed up, you will sink faster but have to apply less crab angle to proceed along your desired ground path. At what point does your airspeed stop paying dividends, and your altitude loss becomes greater than your gains from crabbing less? If you hit sudden sink or lift, you would speed up or slow down respectively, but speeding up requires less crab angle, while slowing down requires more. So we must constantly make angle (turn or heading) adjustments along with our normal pitch or speed adjustments to fly most efficiently. Most XC pilots know that the air constantly varies in lift and sink, so the problem becomes wearisome and complex. If we add to the situation a wind varying in strength or exact direction of crossing, we have an almost insurmountable problem.

Sailplane pilots have tried to solve this three-dimensional dynamic problem by taking computers onboard and running programs. But it is almost impossible to keep everything sorted out with changing altitudes, wind velocity, lift, and sink. To be sure, some of our modern instruments can give us our glide-over-the-ground (a true measure of efficiency), but in my experience, there is too much lag in their input and output (and too much lag in a glider’s response) to be really effective. In fact, we may suffer more losses trying to chase the airspeed will-o’-the-wisp than sticking to an airspeed that only changes gradually.

With all this in mind, I’ll present my policy/ technique when flying in crosswinds with a goal and efficiency in mind (as in competition). I set my airspeed at the correct value for headwind, tailwind, lift, or sink (usually given by a well-setup instrument). Then, if a crosswind is present, I add a little more airspeed. A little means about ten percent: so if you’re flying at 20 mph (a paraglider), add 2 mph. If you are flying 30 mph (a hanger), add 3 mph. I up this a bit in a stronger crosswind.

This is seat-of-the-pants flying, but after oodles of airtime, you can get quite adept at making the right decision.

How do you know your decision is good? That comes with flying in comps when gliding with a few to fifty other pilots. You can observe relative airspeeds and who is maintaining the best glide over the ground. These are the types of judgments you learn in competition, and if you choose to compete, the speed-to-fly and crosswind factors are what you should focus on from the beginning once your thermal skills are honed.

In summary, we’ll simply say that wind complicates all flying, but it also presents us with soaring opportunities and chances to test our skills. I, for one, would be quickly bored if the air never moved, even if it produced thermals. No challenge, no reward. Wind is part of our milieu; learn to fly in it, in all its guises. Enjoy the journey and our restless atmosphere.