One of the simplest ways to enjoy long flights is ridge soaring using orographic lift. Orographic lift is generated when a continual wind is compressed as it moves up over an obstacle such as a ridge, hill, or mountain. Flying in these areas of lift - called lift bands - can be very smooth. However, there are a few dangers to be aware of. Most importantly you must always turn away from the hill. Ridge soaring generally takes place close to the terrain, so if you fly downwind, you are very likely to fly into the hill before you can make a 360° turn. This is why, when flying close to the terrain, we always make figure-8 turns away from the hill.
To maintain or gain altitude you must stay in the lift band that extends outward and upward from the terrain. It is advisable to stay as far out in front of the hill as possible while remaining in the lift band. If you are close to the hill, deep in the lift band and the wind increases, you may get stuck there or blown over the back. To avoid this situation follow the rule ‘if you’re going up, go out’.
Lift Band
If, while remaining a certain distance out in front of the hill, you find yourself suddenly going up, the wind is increasing or the direction has become straighter. Move further out front until you are in a better position and less likely to be blown over the back. If the wind decreases you can retreat back to the hill where the lift will be stronger. Your speed-system is the best option for positioning yourself on the front edge of the lift band.
Be aware of the fast and slow beat while ridge flying. When flying up and down the ridge line, you may find that you are covering ground quickly in one direction, and slowly in the other. This happens when the wind is not perpendicular to the ridge. You have a partial tailwind going one direction, and a partial headwind in the other direction. If you choose to perform a top or side-hill landing while ridge flying, it would be wise to land on the slow beat, or in the direction you are moving the slowest. Keep in mind, that in relation to the ground, your glider will seem to respond faster when turning on the slow beat. Conversely, when turning on the fast beat your glider will seem to turn slower and respond sluggishly. It’s not actually turning any differently, but you are covering different distances depending on whether or not you have a headwind or a tailwind. When turning during the downwind beat, it is wise to begin your turn earlier than you would expect.
When a wind passes through a constricted area, it becomes compressed and speeds up, creating a Venturi effect. When wind passes over a terrain feature, it produces ridge lift. When it passes through gaps or between features, we get higher winds without the lift. This is a problem to consider when crossing a gap in a ridge because there is little or no lift, and higher wind speeds. Make sure you have extra altitude and terrain clearance to avoid being trapped in these areas of high winds. Don’t confuse gaps with depressions or bowls. The wind will be stronger in the bowls, but so will the lift, because the terrain is still deflecting air upwards.
If you are ridge soaring a rounded hill be aware of the ‘seam’. This is the best area of lift and will be a narrow window perpendicular to the wind flow. When flying this area of lift, you will notice that you have a fast and slow beat on both sides of the seam. When you fly out of the seam, you’ll notice an increase in your ground speed. This is your cue to turn back into the seam and onto the slow beat. If you fly too far on the fast beat, you may find yourself unable to penetrate back upwind or in rotor behind the hill.
When launching on a round hill, it is important to identify the seam and launch directly into it. It will help if you pick a horizon reference point, so you can recognize if you are getting pushed off your launch heading which is very common in this scenario.
One last thing to be aware of is wake turbulence from other pilots. When ridge soaring, you are more likely to notice the wake turbulence generated from the wing-tip vortices of other aircraft. The larger and slower the other aircraft’s airspeed, the larger the turbulence will be. It’s especially noticeable behind tandem paragliders. In most cases, the wake turbulence feels like a ditch in the air. However, it can be enough to cause a deflation of your glider, and you should take precautions if you suspect you are about to fly through it.
If other aircraft are passing upwind of the launch area, wait at least 15 seconds before launching yourself. Avoid flying directly downwind or upwind of other aircraft. This is particularly important if you are close to the terrain. When ridge soaring, it is impossible to avoid crossing behind other pilots, so make sure you are thoughtful about managing your glider. Adding an extra pound or two to your brake pressure may help. Make sure you are turned slightly away from the hill, so as to be in a safer position if you do encounter turbulence. When performing a landing either on top or at the bottom of the ridge, avoid the vortices of other pilots upwind of you. Close to the ground is the worst time to encounter turbulence.