Are You a “Control Freak?”  Should You Be?

Copyright fotoglider/Paraglider Magazine 2004

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little_skill ; Pitch ; Adverse_Yaw ; Roll ; DECIDING

  Paragliding, on the surface, appears to be a sport that requires little skill.  As some of you already know, and as the rest of you should know, what’s going on around your wing, and the forces that are keeping you airborne and alive are, in fact, quite complicated.

  As in any other form of aviation, training should be continual throughout your flying career.  Every pilot should take the time to spend at least an hour a month making short, controlled flights on a training hill.  The inherent risks and any deficiencies in skill level, particularly during the ‘taxiing’ to take off and landing phase of the flight, are best overcome by extensive kiting and hops at say a 10ft high grass bank. 

  ‘Flying’ a paraglider while your weight is supported in part by the ground requires a higher level of skill, but carries a lower level of risk than encountered while in the air.  This is true particularly in regards to dealing with any wing deflation and recovery techniques.

  This phenomenon is similar in some ways to a bicycle, which is also several degrees harder to control at slower speeds than at a higher speeds when the gyroscopic effect helps to maintain balance and simplifies control.  The effect gravity has on the paraglider and its pilot when airborne is to assist in maintaining the correct pitch and roll.

  While flying, our aircraft are pitch and roll stable simply due to the pendulum effect the weight of the pilot has hanging beneath the wing.  But on the ground, a paraglider requires input to cause or correct roll or pitch changes.  Understanding some of these inputs, and the effect they can have on your wing will help you to have a better grasp on the dynamics of your craft, making you a better pilot while in the air, AND help you to avoid those embarrassing faux pas on launch.

Much of what follows works best in what I refer to as the XBRL position that is cross break reverse launch.  

 Pitch 

At first glance the paraglider looks as if it is pointing up but if you stop and think, the air flow splits near the bottom of the leading edge and rejoins at the trailing edge. As the side view shown in the photo produces an 'up' illusion, so it is easy to see how instructors make the mistake when teaching 'pitch'.

 As a brief aside, note that as opposed to what is commonly thought, paragliders fly with a NEGATIVE pitch to the under surface while maintaining a positive angle of attack (AoA measures angle of airflow relative to the wing.)  Increasing the pitch just makes it more positive, but the actual value remains negative in sustained, un-powered gliding flight.  Check in your handbook and you will see the ‘A’ lines are the shortest!

 Lift is generated at right angles to the cord line and due to the negative pitch of a glider it has a forward ‘thrust’ component allowing us to continue flying through the air.

Pitch refers to the angle of the wing cord in relation to the horizon.

  Most pilots would use both brakes at the same time in order to increase the pitch of the wing, but remember a by-product of this action is an increase in drag as well.  As an alternative way of influencing pitch when ground handling or taxiing, is for the pilot to move relative to the wing overhead as the primary control, and assist only slightly with the brakes.  This method can create much more positive control and a more desirable result as well.

  Stepping into wind can provide a quick, short-term increase in pitch, but with less drag than use of brakes, AND adds energy to the wing rather than removing it.  The opposite is to ease downwind slightly letting the wing move more overhead, which by reducing drag (lower pitch) also allows easier progress into the wind and to the ridge, ready for takeoff.  This technique requires practice, and if taken too far or too quickly, it can easily results in a frontal collapse.  But even these collapses while ground handling can be sometimes better remedied by pilot movement, rather than brake input.  Many pilots experiencing a frontal when trying to “taxi” or get the wing settled overhead will habitually pull lots of brake.  This is a habit you should work hard to break.  Instead, a smooth but quick step into wind loads the risers and results in the collapse popping out still ready to fly!

   Stepping to control pitch can produce the smoothest, most efficient control method in most circumstances, especially if combined with RESTRAINED use of the brakes.

Yaw and Adverse Yaw

  Yawing refers to the change in angle of the wing either to the right or to the left of the CURRENT heading.  Yaw in a paraglider is a secondary effect induced when the wing is rolled (just like a bike when leaning over turns a corner.)  Adverse Yaw is a primary effect, caused by the greater amount of drag than the extra lift produced when pulling a single brake, or when using differential braking—the easing off on one brake while increasing the other.

   Adverse Yaw, as its name implies, is often not the most efficient way of turning a wing but it can be the quickest and ‘flattest’.  As we are used to using our hands as a primary method of control in life, this is often the method pilots utilize first in their flying careers, and is generally taught prior to weight shift.

   Alternative yaw controls include the use of a single tip line.  Manipulating a single tip line to yaw the glider can induce much less drag than using the brakes. This is because a small amount of drag at the tip creates more leverage due to the greater distance from the wing centre.  Another method involves the asymmetric use of the risers.  Pressure applied to a single ‘C’ riser to “slow down” one side of the wing works well in higher winds or even with care, pressure on a ‘A’ riser to “speed up” the other side of the wing will work.  These also avoid the worst of drag problems associated with the use of the brakes and again avoids the loss of energy that can occur with the traditional methods.

Roll

Roll refers to the angle of the wing in relation to the vertical when facing the direction of flight.

   Note that as opposed to what most pilots believe, ‘roll’ of a pilot, say in turbulent air, is not quite the same thing as the wing rolling.  In bumpy air, a drop (or increase) in the lift under one side of the wing causes the pilot to tip, which up to the point of a collapse occurring, actually can help maintaining a fully inflated flying wing by keeping the internal pressure more even.

  Unlike ‘roll’ of the pilot in turbulence, in a roll turn the pilot weight shifting causes the aircraft to rotate around the pilot, (just think of the pilot being the spindle that the hand of a clock is on with the wing being at the end of the hand and ranging from 10 o’clock to two o’clock.

   One of the most common ground handling flubs almost always involves failure to control the roll of the wing.  When a pilot is facing forward, your ability to induce roll in the wing is greatly reduced, but in the XBRL position, you can induce a tremendous amount of roll by twisting your hips and moving to one side or the other.  It’s a simple movement, but is frequently the opposite of what you might do instinctually.  If you want the left tip higher, turn right and step right.  If you want the right tip higher, turn left and move left, in both cases instead of trying to move sideways or worse backwards the pilot actually moves the way they face which is clearly a big plus of remaining in the XBRL position till ready for launch.

   Some additional roll control can also help when “taxiing” the paraglider.  Let’s say you’ve brought the wing overhead and now you need to move yourself and the wing to a point where the best lift is, or to the most advantageous launch location.  What you’ll frequently see is the pilot trying to essentially “drag” the wing in the direction he wants to go.  Next time, give this a try:  If you step in the opposite direction of the way you want to go, you’ll induce a roll in the desired direction of movement.  Then it’s just a matter of following the paraglider to where you wish to go and as you approach that point, move quicker than the glider and the roll is removed.  (The dynamic here is something the astute cyclist will feel very familiar with.)

   Here’s a fun practice to really refine your roll control skills: try “tip touching”, the ground handling equivalent of a wingover.  Start in the XBRL position, and as swing / run in a curved path in front of your wing to keep the wing under load, you can use ‘adverse yaw’ to further assist moving a wing from, or returning it to, overhead.  Do this by going to zero brake with one hand and pulling some brake on the side of the wing you are moving away from, smoothly and quickly followed by  easing it off at the same rate, this will help roll the wing.  With some practice, this should make ‘tip touching’ easy and is an excellent way to improve your reading of feedback from your wing the key being keeping in touch with the energy (pressure) in the risers & brakes.

   And finally, having control during the launch of your aircraft is something that is absolutely critical, and yet, you’ll see many pilots more following the lead of their glider, rather than getting the glider to do what they want.  The classic “bunny hop” is a perfect example of this.

  The majority of pilots will launch as one action, bringing the wing up from a wall, and moving down hill into the wind.  Instead, for the initial “pull-up” phase of your launch, try a “double bounce”.  Start by bringing up the wing only a foot or so while in XBRL position and then letting the wing settle down while it is still pressured with air, controlling it’s decent by the load on the risers with zero (or very little) break pulled, mainly using brakes only to control the height of the tips.  Then smoothly surge the paraglider up using a mix appropriate for the windspeed of ‘A’s and harness loading, both of which are eased off as the pilot moves downwind under the wing.

  Pilots can then remain where they are until DECIDING to take off, rather than the wing just lifting them off the ground.  Practicing a double bounce method can help you to identify problems before the wing ever gets overhead where it is more difficult to see, as well as has the advantage of having a fully pressurized wing before you start your launch.

   While readying for launch, positioning the brakes in the so called minimum sink setting makes the glider less efficient (degrades the glide angle; more drag than any increase in lift) and will normally permit remaining on the ground.  When you are ready to go, ease off the brakes towards zero brake and follow the wing forward (do not push), increasing the speed into wind allowing you take off when you choose and by curving your ‘taxy’ the ‘wrong’ way (the opposite direction to your first beat) will give a gentle roll into the first beat without flying out through the lift band of turn tightly.  The benefit is that as you are leaving the ground, the wing is already flying efficiently, exactly what you want at the most critical part of your flight!

   And when your flight is complete, and you’re dropping the wing back to the ground, why not practice your control?  As the wing passes the point of no return on its way down (about ½ to 2/3 up) move the brakes smoothly to zero, saving the wing from added stress of smacking it into the ground, and leaving a neat wall ready for the next flight. Prior to this landing as stall training in general aviation is actually about detection and AVOIDING an incipient stall, why not at a couple of feet up slow almost to stall point and practice recovering WITHOUT surging and diving.  

   During flight, extra controls such as a speed bar, trimmers, etc. can be used and are not covered here.  But by understanding and applying the knowledge that is available out there often requires the pilot to do the OPPOSITE of what at first seem natural and correct.  Overcoming those incorrect impulses is exactly what aviation training and practice is for.  Getting that training, and taking the time to practice and UNDERSTAND your wing may save your life.  I can think of few things that more warrant you doing a bit of studying, and of course, questioning everything!