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Asymmetric Angle of Attack
2/2001

We need to manage our angle of attack asymmetrically.
There are times I need to use almost full asymmetric control travel to maintain some pressure.

The canopy can yaw, surge, load and off load, accordion, pressurize and depressurize etc. Ultimately the angle of attack needs to stay within a range that depends on variables. If the angle of attack gets too high the wing will stall, if it's too low it will tuck. If you're going fast it can front tuck and snap back into a full stall. If it's too high asymmetrically it will stall one side and spin toward the stalled side. If it's too low asymmetrically it will tuck one side (tip fold), and possibly surge forward and spiral due to increased loading on the percentage of wing remaining tensionally structured and flying.

We manage angle of attack by controlling pitch angle and camber configuration. Applying brake will increase the angle of attack because we change the camber, resulting in a different chord line. It will also slow the canopy, which will induce an oscillation causing transient pitch up.

Angle of attack is more likely to exceed a low limit when we fly fast.  If we sense unsettled air we can defensively slow down for margin against tucking, plus we can feel the air through the brakes. Angle of attack is not brake position alone, we can have a high angle of attack with little or no brake when the pitch angle is high.  Angle of attack is the angle the chord line of the wing makes with the relative airflow over the wing, not the angle it makes with the horizon. As we move through vertically active air the angle of attack can change because the air is meeting the wing at a different angles.

When the air is vertically active the angle of attack can vary from side to side. We feel the angle of attack in the brake lines and apply more brake if we feel the pressure decrease. Sometimes we need to use full travel. We might be trying to turn hard left into a small strong core, but have to apply full right brake to keep that side pressurized. There is balance involved because pressure, speed, energy, pitch, rotation, brake position and travel are all interdependent, dynamic, and transient. You want to be aggressive and use enough, but not over control too much because oscillations are inefficient and leave you venerable near the apex.

You build an intuitive feel for the rhythm of the air. Developing peripheral awareness of your angle of attack and managing it to fit various scenarios is one of the most important skills.

Sometimes we get out of sync, and sometimes we encounter large magnitude sharp gradients such that no matter how quick, aggressive, and balanced we act, we exceed one or more of the parameters (angle of attack, pressure, airspeed) needed for our canopy to remain tensionally structured and flying.

Sundowner

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