Notes for new hang glider pilots--ridge soaring safety
August 21 2005 edition
steve at aeroexperiments.org
New hang glider pilots often fail to appreciate some of the hidden dangers of ridge soaring, especially in high winds. Here are a few warnings and strategies.
When the wind is strong, it is critical that you keep an eye on your potential reserve of forward groundspeed. Always be aware that the wind could very quickly gain another 5 mph or more of velocity, and if you haven't been vigilant, you could end up in a situation where you can't avoid being blown "over the back" of the ridge. If you need to have the bar pulled substantially in from trim just to "kite" in place, or if you can't create a very substantial forward groundspeed by pulling the bar in about halfway toward the "stuffed" position, you need to immediately do your utmost to penetrate forward away from the terrain and down to lower altitudes where the wind will likely be lighter.
By the same token, keep an eye on your ability to lose altitude at will. If you need to pull the bar in quite a lot just to get a significant descent rate going, you are in danger of being lifted to a higher altitude where the wind will be stronger and you may not be able to penetrate forward. Your ability to fly forward out of the lift is integrally linked to your ability to descend at will, and vice versa. Move forward out of the lift band if you find yourself in very strong lift in a high-wind situation.
Practice flying fast with the bar "stuffed"-- many gliders are prone to yaw-roll oscillations in this configuration, but this can be overcome with practice. If you can't keep the glider flying in a straight line at high speed, this will compromise your ability to penetrate forward to escape high wind or strong lift. If you have any trouble with this--as most new pilots do--you need to be extremely cautious about flying in high winds.
One key to safety in strong winds is to stay well out in front of the ridgeline, especially as you climb to higher altitudes. The closer you are to the flat ground in front, the quicker you'll be able to exit the region of lifting air should the wind show signs of a dangerous increase in velocity.
In some ridge soaring conditions, clouds can form very quickly. Be very aware that if any cloud is present in slope lift, more clouds may swiftly form, at various altitudes. Never be complacent about the possibility of being "whited out"--if you lose visibility in a cloud, you will lose all control of your glider.
If clouds are forming above you, be especially aware of your "reserve" of potential forward groundspeed and your ability to descend at will as outlined above--you may need to suddenly penetrate forward and down to stay out of the cloud if the wind velocity increases or the cloud base begins to drop. If the world starts to grow faint and misty below, you've come way too close to the cloud--"stuff" the bar immediately and keep an eye on the brightest, most visible reference point on the ground below and do your best to penetrate forward (upwind) and down. Getting your knees over the bar can help to increase your forward velocity and sink rate--I fly with my harness unzipped when there are clouds close above me in strong ridge lift, as well as any other time that the wind is strong and I feel that forward penetration may become critical.
If clouds are forming below you the situation calls for even more caution. Clouds that form below you and ahead of you will be blown up to your level in the ridge lift and can grow very quickly in size as they rise. For this reason even a small wisp of cloud below you and in front of you calls for great caution. Always assume that clouds below and in front of you will rapidly increase in size, and always have an escape route in mind at all times. By keeping an eye on the relative motion between the edge of the cloud and the ground beyond--just like you keep an eye on the relative motion between a treetop and the ground beyond to see if you will clear the treetop on your landing approach--you can get a good idea of the cloud-edge's relative motion in relation to you. If the top of a cloud in front and below you is rising or remaining fixed in relation to the background references, it will not pass safely below you, and it is critical that you take action immediately to steer toward a clear escape route, even if the cloud is still far way. Always have an escape route in mind at all times when clouds are forming below you and in front of you. You should take action to descend to a lower level, or to move forward to an area of weaker lift, or to move to a different part of the ridge, before you have to seriously start dodging the cloud-puffs. In certain conditions it can be enjoyable to try to remain above the cloud-tops and watch the glory (rainbow halo) around your glider's shadow, but you absolutely must have an escape route to clear air in mind at all times.
Another dangerous situation is when clouds are forming below you and aren't threatening to engulf you, but suddenly begin to cover a large area. It can be very beautiful to fly above a sheet of cloud, but if that cloud increases quickly in size and covers up most of the ridge, it will be hard for you to keep track of your position and avoid drifting back over the ridge. If you end up behind the ridge, out of the lift, you are in danger of sinking down into the cloud. If the cloud becomes extensive enough to hide your view of the all ground out in front of the ridge the situation is even more dangerous. You could end up with no idea of where the ridge is and no idea of which direction is "upwind", especially on an overcast day where the sky above offers no visual references. Because the clouds (or at least the fine texture of the clouds, in the case of stationary wave-like clouds) move with the wind, you won't have an visual cues from the cloudtops to alert you if you end up flying crosswind or even if you end up flying directly downwind: the relative motion cues from the cloud sheet will be very different from the relative motion cues that you would normally get from the ground. Pilots who aren't aware of this can be swiftly disoriented by even a partial cloud sheet below them. Always take action before you lose the ability to keep the ridge in sight, and always take action long before you get trapped above a sheet of cloud that extends forward far enough to hide all the ground in the upwind direction or to block all your upwind escape routes.
If you strictly observe the legal cloud clearance requirements--as you should--you won't have any problems with clouds.
Remember that there's always another day to fly, and think twice before launching in strong winds.