Part one of “Safety Check—Fly It, Don’t Fight It” (October Parachutist) discussed establishing a landing pattern that works for your canopy at your current wing loading. Hopefully, you’ve done so and maybe even added notes in your logbook identifying the predetermined altitudes and specific locations over the ground that give you the ideal landing pattern. Maybe you even tried shifting that pattern for different wind directions. Now let’s discuss how to adjust your altitudes and locations to fly safely and accurately in high winds.
We’ll need to make some generalizations about landing patterns and round a few numbers to make the math a little easier. Each canopy pilot needs to know the flight characteristics of their canopy and adjust the models to fit their circumstance.
Skydiver’s Information Manual section 4-A.D covers pattern adjustment for different winds speeds. In light and variable winds, your pattern is fairly square. As winds pick up, the pattern becomes more rectangular; the higher the winds, the narrower the rectangle becomes. Gate altitudes remain constant, but gate location over the ground changes.
Let’s discuss a pattern adjustment from no winds to 10-mph winds, assuming your canopy has a 20-mph forward speed in full flight. To calculate the ground speed of your final leg, take the forward speed of your canopy (20 mph) and subtract the headwind (10 mph). The result is a 10-mph ground speed, which would result in you covering half the distance on this leg than you would have in no winds. The wind has a similar effect on the crosswind (base) leg of your pattern, too. With approximately half of your forward speed countering the wind (crabbing), your ground speed is reduced, nearly cutting the distance covered during that leg in half, too. Therefore, adjusting the location of your final and base gates is easy. Simply cut the distance traveled for each leg in half and move the location for those gates accordingly, keeping the altitude for all gates the same (see Box Pattern illustration).
Your downwind gate location is also going to change significantly. To calculate your downwind leg’s ground speed, add the forward speed of the canopy (20 mph) to the tailwind (10 mph), giving you a 30-mph ground speed. Your ground speed has increased by a factor of 1.5 (30/20); therefore, the distance traveled will increase by the same factor. If you traveled 600 feet across the ground on your downwind in light and variable winds, in 10 mph winds, you would travel 900 feet across the ground (600 times 1.5). Adjust the location of your gate accordingly.
Sometimes—especially in higher winds—this adjustment can move the location of your downwind gate off the landing area, perhaps deep over obstacles. This contradicts the adage, “Don’t fly over anything you don’t want to land on.” In these cases, you can head to the upwind side of the landing area by 1,000 feet and hold into the wind. Using brakes while holding into the wind, hover there until you get to the appropriate altitude to merge into the downwind leg. For example, the illustration shows how you would merge into the landing pattern halfway down the downwind leg at approximately 800 feet. Don’t forget to factor in the altitude you will lose during the turn, so that you merge into the pattern at the correct altitude. This technique can cause confusion in the landing pattern if you don’t take proper precautions, so consult with your local Safety and Training Advisor before trying this.
Another way of adjusting for higher winds that is gaining popularity is called drifting. A drifting pattern allows canopy pilots to drift with the wind on the crosswind (base) leg rather than flying into the wind as jumpers do with the standard box patterns. A drifting pattern also keeps jumpers upwind of their landing target for most of their pattern, which give a jumper more time to discern wind strength or direction changes. This pattern allows your downwind leg to always be the same parallel distance from the landing target rather than having the downwind leg move closer to the landing target as in the standard box pattern. Jumpers using a drift pattern can mix with jumpers using a traditional box pattern as long as everyone maintains vertical separation. The two patterns will converge as the jumpers turn onto their final legs. Consult with your local S&TA before trying a drifting pattern in your landing area.
Plan your pattern before you jump, but don’t expect everything to go according to the plan. The worst-case scenario is realizing too late that not only has the wind strength changed, but so has the wind direction. The best way to avoid that situation is to build a double check into your routine. As soon as you have cleared your airspace and completed your canopy-control check, turn into the wind and assess them. Then continue to monitor your ground speed and your ground track relative to the direction your canopy is facing as you work your way to your holding area.
This might seem like a lot more math than you signed up for when you started skydiving, and you might be tempted to forego any planning and fly it as it comes. However, understanding the basic principles of adjusting your location points for higher winds is vital to improving your safety and accuracy. The most important thing to remember is to increase your wind limits gradually, which makes these adjustments a lot easier and safer. Now, get out there and practice, making sure you plan ahead and reflect and log afterward!
Ron Bell | D-26863
USPA Director of Safety and Training