Knowing and having the correct reaction to critical situations is a core goal for instructors. I discuss and go over critical situations during ground schools. The results of students have inspired this article. Away from ground schools, I frequently do pop quizzes to check the reactions to different critical situations. Over time, I have seen that the most common place student pilots get crossed up is asymmetric collapses vs spins. Since these two are a more common possibility in thermals, separating the reactions and understanding is important.
Before going into the meat and potato of these, I would like to say that there is no substitute to doing an SIV clinic. The myriad of maneuvers that SIV coaches teach help newer pilots become comfortable in active air. The basics for critical situations do not change. Understanding the correct responses will enable pilots to react correctly if they need to deal with either of these. Collapses are the more common of these two, but spins would likely be the next in the list of critical situations that can happen while flying.
Let’s go over the basics of what each is, what the common causes are, and finally, what the correct reactions should be:
Asymmetric Collapses
Collapses happen when the pressure on the outside/front of the leading edge of the wing has greater pressure than the inside. This occurs when the angle of attack becomes too low. When this happens, the fabric is pushed downward and collapses. This can be a small “tip slap”, a medium 30 – 40% of one side, or a big 50 – 75 % one that is the most severe. If 80% – 100% occurs, the behavior is more like a full 100% frontal that is not asymmetric. Full frontals often fix themselves before a reaction is done, or just require a pull of both brakes to help pull the wing back a little, and the center and rest of the wing usually re-inflate. Full frontals are easier to deal with in many ways. Most of the time, they can take care of themselves, but if you need to, the reaction is to pull the brakes down till the leading edge begins to re-inflate.
The reaction to collapses is “Steer, then Clear”. By steer, what is meant is to keep the glider’s heading and prevent it winding into a turn toward the collapsed side. Use weight shift in the opposite direction of the collapse, combined with enough pull of the brake to help block the wing from turning toward the collapsed side. The turning occurs because of the added drag from the collapsed portion of the wing. With most collapses, the turning will gradually worsen over time, so learning to react quickly is important. For small tip collapses, it will often fix itself by the time you have started to change lean the opposite way. With larger collapses, adding some brake pull will help keep the glider from turning. Using more weight shift minimizes the amount of brake that needs to be pulled. The amount of brake to pull is usually not much when the weight shift is in place. The brake pull amount is a dynamic thing. You can look ahead and find the correct amount of brake to pull to go straight ahead.
The clear part is only needed when the collapse continues after maintaining direction. If the wing re-inflates after the direction is sustained, then the event is over and you can continue flying. Only when the wing stays collapsed do you use the clear portion of “Steer, the Clear”. Clearing the wing is done by pulling the brake on the collapsed side to shoulder or just below level. This changes the shaping of the rear part of the airfoil and helps get air pressure to help re-inflate the collapsed side. In the old days, we used to do larger pumps to help clearing, but the modern wings usually only need a steady pull to help this. Clearing is fairly rare on modern wings, unless there is a cravat. Cravats need a specific discussion, but in a nutshell clearing a minor cravat can be done by yanking or reeling in the stabillo line, or doing a larger big ear on that side.
To prevent collapses, the best practices are:
- Pitch awareness is one of the biggest keys to active flying. Learn to recognize and anticipate wing movements. Know the correct reactions related to Active Flying.
- When flying in active air (thermals and or bumpy – Note: Know the limits for your skill level!), keep some light tension on the brakes to better feel the wing and add stability. Remember that (on most entry to intermediate wings) brakes to just above or around shoulders tend to be a higher internal pressure for the wing. This angle of attack resists collapses much better than flying at trim.
- Always stay calm and loose in your arms when flying. Stiffness can slow down your reactions.
Spins
Spins are an asymmetric stall that causes the wing to rotate above the pilot, much like a helicopter blade. Stalls happen due to an angle of attack too high. This is the opposite of the cause for collapses. This is why the reaction for the two is different.
Spins are almost always caused by the pilot either flying too slow in rough air or pulling a brake on the inside too strong, or when the wing already has a high angle of attack. The end result is that the inside wing stops flying and the outside wing starts rotating around the inside wing. A big collapse can also begin a spin if the pilot does not do the steer part of “Steer, then Clear” enough. The wing does not often collapse during a spin. The pressure on the inside half of the wing will have lower pressure. The other, flying side of the wing in a spin will have enough pressure, so that the cross venting ports all have some pressure to move to the stalled side of the wing.
The reaction to a spin is definitely not “Steer, then Clear.” Instead, the primary is to release both brakes all the way up to the pulleys to help un-stall the wing. For simplicity, we will call this “hands up”. Lower rated wings (A and B) often exit the spin almost immediately. In nearly 30 years of flying, I have not had a spin happen other than when practicing them intentionally at an SIV clinic. With that said, they happen a lot, and more often to newer thermal pilots. I would say the most common time they happen is when a pilot encountered a thermal. After entering the thermal, a pilot can tell it is a good one, and can pull the inside hand down too far to turn into the thermal. There are many reasons that a pilot might pull that hand too much, but the result is the same. Because the angle of attack became high when they entered the thermal, the wing was already closer to stall. When they pull the inside hand down quickly and possibly too far, the inside wing can stall easier than if they pulled this hand during a time when the wing was at its normal angle of attack.
To prevent spins, the best practices are:
- Never yank a brake down super fast or below minimum sink level to start a turn.
- Leave the brakes up until the wing comes back overhead, before slowing down to climb better in a thermal. Instead, wait till the wing is back above you.
- Learn to turn in thermals by letting the outside hand up, and resist the temptation to pull the inside hand any further than the minimum sink level.
When the wing is back overhead and the brakes have been pulled, steer with the outside hand by combining lots of weight shift and letting the outside hand up to initiate the turn. If the outside hand is fully released and the glider still does not turn enough, resist the temptation to pull the inside hand further than just below the shoulder.
Know the difference between the reactions:
So, now it is up to you to think through these and have a clear answer if one of these happens. I believe the key is to understand and prevent both of these, and to keep awareness of angle of attack all the time when flying. Angle of attack is pitch control and awareness. I have felt and like to teach pilots to feel their wing. What I mean is that through the brakes and senses of where the risers are, you can tell if your wing is falling back (increasing angle of attack) or surging (decreasing angle of attack). Prevention is great, but if you fly in stronger thermals, you will certainly hit the edge of a thermal with your wing and have some collapses. Steer, then clear! If you ever feel the wing rotating you around below it, you likely entered a spin. Brakes Up!
