Ridge Strong lee-side sink Wind 15 knots Wind 15 knots Normal radius of turn—no wind Increased radius of turn with wind Safer, angled approach, then set crab angle the glider and the ridge. In that case, either turn back in the  other direction (away from the ridge) if traffic permits or  fly upwind away from the ridge and rejoin the slope lift as  traffic allows. If using a radio, try to contact the glider by the  completion number and then coordinate the passing. When  soaring outside of the United States, be aware that this rule  may differ. The glider with its right side to the ridge has the right of way.  [Figure 10-22D]  Title 14 of the Code of Federal Regulations  (14 CFR) requires both aircraft approaching head-on to give  way to the right. A glider with the ridge to the right may  not have room to move in that direction. The glider with its  left side to the ridge should give way. Additionally, when  overtaking a slower glider along the ridge, always pass  on the ridge side. If the overtaking glider encounters sink,  turbulence, etc., it must maneuver away from the ridge. This  is acceptable. When piloting the glider with its right side  to the ridge, ensure the approaching glider sees you and is  yielding in plenty of time. In general, gliders approaching  head-on are difficult to see; therefore, extra vigilance is  needed to avoid collisions while slope soaring. The use of a  radio during ridge soaring is recommended. Pilots must be  familiar with 14 CFR part 91, section 91.113, Right-of-way  rules: Except water operations, and section 91.111, Operating  near other aircraft. If the wind is at an angle to the ridge, bowls or spurs (i.e.,  recessed or protruding rock formations) extending from the  main ridge can create better lift on the upwind side and sink  on the downwind side. If at or near the height of the ridge,  it may be necessary to detour around the spur to avoid the  sink, then drift back into the bowl to take advantage of the  better lift. After passing such a spur, do not make abrupt  turns toward the ridge. Always consider what the general  flow of traffic is doing. If soaring hundreds of feet above a  spur, it may be possible to fly over it and increase speed in  any sink. This requires caution since a thermal in the upwind  bowl, or even an imperceptible increase in the wind, can  cause greater than anticipated sink on the downwind side.  Always have an escape route or, if in any doubt, detour  around.  [Figure 10-23] It is not uncommon for thermals to exist with slope lift.  Indeed, slope soaring can often be used as a “save” when  thermals have temporarily shut down. Working thermals  from slope lift requires special techniques. When a thermal is  encountered along the ridge, a series of S-turns can be made  into the wind. Drift back to the thermal after each turn if  needed and, of course, never continue the turn to the point that  Bowls and Spurs Slope Lift Figure 10-20.  Flying with a wind increases the turn radius over the ground, so approach the ridge at a shallow angle. Figure 10-21.  When flying close to a ridge, use extra speed for more  control and to pass quickly through sink. 10-13