{"id":16639,"date":"2014-07-23T23:00:00","date_gmt":"2014-07-23T23:00:00","guid":{"rendered":"http:\/\/skydivemag.com\/new\/?p=16639"},"modified":"2022-08-29T12:06:23","modified_gmt":"2022-08-29T12:06:23","slug":"2014-07-24-wing-loading-and-turns","status":"publish","type":"post","link":"https:\/\/www.skydivemag.com\/new\/2014-07-24-wing-loading-and-turns\/","title":{"rendered":"Wing Loading and Turns"},"content":{"rendered":"\n

How does wing loading affect altitude loss in a turn?<\/h2>\n\n\n\n

How can we manage this to keep ourselves safe?<\/h2>\n\n\n\n
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Image: Jesse O’Neil by Maia-Jena Allo<\/figcaption><\/figure>\n\n\n\n
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Note:<\/strong> This is part 2 of John LeBlanc\u2019s article – Part 1 looks at general affects of higher wing loadings here<\/a><\/em>.<\/p>\n\n\n\n

Since we occasionally make mistakes, we must be very careful to choose a parachute size and model that allows for some reasonable margin of error<\/p><\/blockquote><\/figure>\n\n\n\n

Wing loading and turns<\/h3>\n\n\n\n

High wing loading changes the flight characteristics of turns. The aerodynamic relationship between bank angle, turn radius and rate make the turns different at high wing loadings. Misunderstanding of this often leads to the dangerous low turn accidents all too common today, even with conservative people who never want to do hook turns.\u00a0<\/p>\n\n\n\n

Obviously as the canopy gets smaller, the turns get quicker, right? Well, yes and no. To explain, think of two motorcycles going around the same curve but at different\u00a0speeds. The faster bike must be leaned over much more to make the turn, while the slower rider leans much less.<\/p>\n\n\n\n

For turns that have a constant radius, more bank angle is required as the speed increases<\/em><\/strong><\/p>\n\n\n\n

If the slower rider now chose to lean exactly the same amount as the faster one, he would go off the inside of the road and make a much tighter turn. The slower bike would turn a complete circle much quicker than the faster one.<\/p>\n\n\n\n

For turns that have a constant bank angle, the slower the speed, the tighter and quicker the turn.<\/strong><\/em><\/p>\n\n\n\n

These two observations are also true for airplanes and parachutes.<\/p>\n\n\n\n

For a given bank angle, the slower parachute will make a 360\u00b0 turn more quickly, and in a smaller area. So in some ways, the canopy at the lower wing loading has better turn performance, especially if you start looking at how much space a certain turn occupies! <\/p>\n\n\n\n

In this description, we are referring to a turn where the flight path is still somewhat flat, and turning at a full glide rather than a vertical spiral straight toward the ground. At full glide, an attempt to turn faster results in a spiral dive with a rapid increase in descent rate. When flying a smaller canopy, this spiralling dive rotates much faster. As the wing loading goes up, the spiraling rate gets quicker. Since more speed requires greater bank angle for a given turn rate, the altitude loss builds up much faster at high wing loadings.<\/p>\n\n\n\n

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Altitude loss builds up faster at high wing loadings
Image by Nik Daniel<\/figcaption><\/figure>\n\n\n\n
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Altitude loss<\/h3>\n\n\n\n

A large student canopy might double its rather low rate of descent in a hard spiral. A modern canopy flown at high a wing loading, however, may quadruple its already high rate of descent in the same turn! At extreme wing loadings, the increase in rate of descent can be astronomical, with a 180-degree turn consuming as much as 500 feet of altitude!<\/p>\n\n\n\n

Earlier planning<\/h3>\n\n\n\n

Underestimating the amount of altitude lost in a turn can easily get you into trouble when flying at higher wing loadings than you\u2019re used to. Planning your landing pattern becomes much more challenging. Many conservative jumpers are often caught off guard by this when trying a smaller canopy. The typical experienced yet conservative jumper flying his own canopy becomes accustomed to judging how much time and altitude he needs to fly a conventional downwind, base and final approach, where the final turn is moderate.<\/p>\n\n\n\n

When this conservative jumper tries a smaller canopy, the turns cover more ground than he expects. Since the turns run wide, he turns a little sharper. As he does this, the flight path becomes very steep, resembling a diving spiral, eating up altitude very quickly. After a turn like this onto downwind, then another onto base, the unfortunate jumper may have insufficient altitude to complete his last turn to final. But often the extra speed taxes his perceptual skills, throws his judgment slightly behind, and he finds himself doing an unwanted low hook turn. Yes, his first hook turn, on the fastest canopy he\u2019s ever jumped\u2014and an unfamiliar one too!<\/p>\n\n\n\n

Underestimating the amount of altitude lost in a turn can easily get you into trouble when flying at higher wing loadings<\/p><\/blockquote><\/figure>\n\n\n\n

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Higher wing loadings can lose altitude rapidly in turns
Image by Zach Lewis<\/figcaption><\/figure>\n\n\n\n
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The solution<\/h3>\n\n\n\n

How do we manage this rapid altitude loss in turns at higher wing loading?<\/p>\n\n\n\n

1, Downsize progressively<\/h4>\n\n\n\n

Make only a small change to the next size down and, if you\u2019re not sure, wait!<\/p>\n\n\n\n

2, Plan further ahead<\/h4>\n\n\n\n

Plan further ahead. Enter your downwind leg much higher, and fly a larger pattern with larger radius turns. Use brakes to adjust flight path and descent rate.<\/p>\n\n\n\n

3, Learn flat turns<\/h4>\n\n\n\n

Really experiment and learn all about flying braked [flat] turns<\/a>. By using braked turns early in the pattern, you can leave lots of altitude for a safe turn to final. Doing the opposite (making full-glide turns early and a low, braked hook turn at the last second) shows poor planning skills and lack of judgment. It is also somewhat suicidal.<\/p>\n\n\n\n

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Plan further ahead<\/figcaption><\/figure>\n\n\n\n

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Swoop Landings<\/h3>\n\n\n\n

Accidents occur when swoop landings are done incorrectly. The higher risks of such landings cannot be ignored. I don\u2019t wish to encourage the uninterested to experiment with swoops, but some safety hints may help those presently involved:-<\/p>\n\n\n\n

1, Evaluate the traffic<\/h4>\n\n\n\n

There is no real reason for a swoop landing \u2014 except for pure enjoyment. This does not dominate over the obligation to fly in a manner that enhances the safety of all the jumpers in your vicinity. Don\u2019t even think of swooping if traffic is even a little heavy. It\u2019s not even close to permissible just because you didn\u2019t hit anybody. If your fancy landing startles some novice jumper or causes others to become preoccupied with your actions, then your fancy landing was dangerous and rude.<\/p>\n\n\n\n

2, Improve efficiency<\/h4>\n\n\n\n

An efficient swoop is made with a smooth but conservative approach. You\u2019ll swoop farther than the guy making the radical snapping turn with the coarse control movements. If you make turning approaches, do so much higher and smoother, with less bank angle. You\u2019ll be amazed at how much speed can build up using this technique.<\/p>\n\n\n\n

If you think a turning approach is needed to build up enough speed to get a good landing, you probably need to work on perfecting your technique. A conventional landing approach should work well, even at high wing loadings. But if you insist on experimenting with turning approaches, do so only on a canopy you are very familiar with, not some new canopy that you have only one or two hundred jumps on. It can take thousands of jumps on a single canopy to become consistent with turning approaches. The accident reports are littered with those who seemed to be consistent until that last jump.<\/p>\n\n\n\n

Don\u2019t even think of swooping if traffic is even a little heavy<\/p><\/blockquote><\/figure>\n\n\n\n

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Improve your efficiency
Photo: Luis Prinetto landing his PD Sabre3, by Scott Jontes<\/figcaption><\/figure>\n\n\n\n
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3, Build in excess altitude<\/h4>\n\n\n\n

When the decision is made to attempt a turning approach, do so with lots of excess altitude. This will give more time to correct errors in judgment, or even to change the plan entirely. For example, if you set up very high and notice previously unseen traffic halfway through your turn, you should have the speed, altitude and skill to quickly abort the diving approach and change to a rapid gain of altitude, even continuing the turn if necessary. Make a braked approach to a straight-in landing, then walk over to the other jumper and apologize for your lack of vigilance for other traffic. None of this is possible from a \u201clow hook turn.\u201d If you can\u2019t visualize the methods needed for this set of maneuvers, then don\u2019t even think about doing a turning approach\u2014especially when I\u2019m in the air with you.<\/p>\n\n\n\n

Learn how little altitude can be lost in a turn while at higher altitudes, but only use this method as an emergency salvage maneuver to abort the normal turn that seems a little too close. Never intentionally attempt a turn so close to the ground that the salvage method is the only possibility of pulling it out. Your judgment is probably off, so you might smack the ground. You don\u2019t think your judgment will be off? Then how did you get into the position of needing this low turn anyway?!<\/p>\n\n\n\n

It can take thousands of jumps on a single canopy to become consistent with turning approaches. The accident reports are littered with those who seemed to be consistent until that last jump.<\/p><\/blockquote><\/figure>\n\n\n\n

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Build in excess altitude, your turn should level out well above the ground
Image by Rolf ‘Kuri’ Kuratle<\/figcaption><\/figure>\n\n\n\n
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4, Don\u2019t become a \u2018digger\u2019!<\/h4>\n\n\n\n

If you find yourself needing to pull the toggles down hard to avoid hitting the ground [digging yourself out], of course do so. Try hard to keep the wings exactly level, all the way through touch down, until all movement stops. Don\u2019t give up! Then, assuming you have survived, get up (if you can) and kick yourself hard for exhibiting such poor planning and judgment. It\u2019s critical to understand that an intentional \u2018low turn\u2019 has no value for swoop landings. It doesn\u2019t allow enough altitude:-<\/p>\n\n\n\n