The most challenging and dangerous aspect of ridge soaring is turning low and slow near the mountain. This puts the glider near the edge of stall while close to the ground in gusty conditions. This is the perfect recipe for entering a spin. Learning to maneuver near the ridge is probably the most important aspect of ridge training.
The remedy is to avoid these situations. A good minimum margin for beginners is to fly no lower than 150ft AGL and no slower than Best Glide Speed near a ridge. And given, there are several critical rules that must be observed while turning low near a ridge. I have made several clips in Condor to demonstrate both proper technique and the consequences of improper execution.
How to S-Turn Near the Ridge
When starting a turn, drop the nose, gain airspeed, and steepen up your bank.
The big themes when turning low are maintaining extra airspeed, good co-ordination, and spatial awareness of the mountain. We want to stay in the ridge band while maintaining adequate margin over stall. Remember, stalls are due to exceeding the critical angle of attack. You can exceed the critical AoA by steepening your bank and/or by slowing down. As a result, if you want to maintain a greater margin over stall you must let your speed increase as you increase your bank.
Remember to bank out of the turn early. The wind will want to drift you toward the ridge. You must start banking out well before then so that you have time to level out.
Avoid pulling up hard and banking at the same time.
This is the corollary to the previous point… many beginners tend to pull their nose up hard when entering a thermal and crank over into the turn. Halfway into the entry turn, their airspeed gets dangerously low and they mush or stall out. This is sub-optimal in a thermal at 3000ft, but it is absolutely unacceptable low near the trees; not only is the airspeed low, but the wing is loaded into the turn (high G). This is the perfect recipe for a spin entry.
How to (Properly) Thermal off the Ridge
When you approach a thermal, turn away from the ridge while maintaining good airspeed and co-ordination. Complete several S-turns to get at least 200ft, preferably 400ft above ridge top. At this point you could consider transitioning into a full turn and climbing away from the ridge.
Don’t Attempt a Full Turn Low!
Don’t turn low near the mountain! As you come around the turn, the mountain will come up at you really quickly and you will be exposed to a deadly trap. You will have high ground speed with low airspeed and experience “ground-rush” as the mountains comes up at you fast. The deadly trap is the desire to pull back to avoid hitting the ridge. This will stall the glider.
Don’t turn low. But if you find yourself in this situation, the ONLY way to escape is to steepen up your bank while dropping the nose. This will let you tuck away from the ridge and escape.
Don’t Turn Toward the Mountain!
Never, ever turn downwind toward the ridge. This is very dangerous and will near certainly drop you out of the turn on the far side. Even if you manage to complete the turn, you will have drifted far over the ridge and will have a long way to get back.
Spin on Thermal Entry
This reinforces all the previous points; maintain good airspeed, co-ordination, and spatial awareness when turning low near a ridge. Do not pull back and bank at the same time and mush out on the top part of the turn. One devastating trap is when you do this while entering a thermal. If you mush while at the top part of the turn after turning too early, there is a good chance you will encounter the “killer gust”.
What happens is as you go away from the core on the downwind side of the turn, you will be entering a zone of lift that gets weaker and weaker, until you’re finally in the sink. As you traverse that shear, it sucks the energy out of the glider.
The devastating consequence is that this occurs right as you are at the top part of the turn, very slow and the wing is loaded up. That killer gust will near certainly spin you out of the turn.
There is a much deeper discussion as to how and why shear works the way it does near mountains, which I will address in more detail some other time. The key point to remember is DO NOT turn early and hard into the thermal while bleeding off your airspeed; be ready for that sharp gust on the far side of the turn.
Here are a couple simple guidelines:
- Maintain a minimum AT LEAST 150ft AGL and best glide speed while soaring the ridge.
- ALWAYS turn AWAY from the ridge. (Ie: If the ridge is on your left, turn to the right.)
- Complete S-turns or “dogbones” when 200ft AGL or lower near a ridge. 400ft is better.
- Spin avoidance
- When making turns, drop the nose a bit and gain airspeed.
- Don’t bank and pull at the same time.
- If you need to escape, bank steeper while speeding up. Don’t just pull back on the stick if the trees are coming up at you!