Understand Toggle Turns 3

There are 8 inputs that you can use when controlling your parachute: you have two brake toggles, two rear risers, two front risers, and two legs with which to do harness turns.

Today’s focus: toggle turnsparachute lines

Let’s go back to the figure that we used when looking at parachute aerodynamics and see where our brake lines attach to the parachute.  If we follow the control lines up from the toggles, we see that each control line splits into 4 lines.  These 4 lines then are attached to the tail (or trailing edge) of the parachute on either end.  I have crudely highlighted in red the control lines from a jump that I made a while ago (on a Navigator 200, if anyone is interested).

parachute brake linesRemember the term “drag”?

There were several things that we could do to decrease our drag (i.e. thinner lines, changing our body position to reduce our surface area, collapsible sliders, etc), but there are also ways that we can increase drag.

When we pull down on a steering toggle we are pulling down on the tail of the parachute, causing increased drag on that side of the parachute.  The increased drag slows down that side of the parachute and the other side continues to fly at full speed.  Essentially, we are flying our parachute around the increased drag side.

If you found that confusing then try this little experiment:

Stand up and walk forward.  No problem – we do this all the time!

Now, stand up and walk forward, but your right foot can only go half a step every time your left foot takes a full step.  What ends up happening?  If you did this correctly, then you would find yourself turning in a circle.

The only difference between what you just did and what happens when you turn your parachute is that we are always on the way down (losing altitude) when we are underneath our parachute.  Hence, we cannot make turns under our parachute without losing some altitude.

Back to toggle turns:

The parachute will continue to turn as long as we hold a toggle down, and the speed of the turn is directly proportional to how far down we pull the toggle.  In other words, pulling your toggle down to your hips will result in a much faster turn than pulling your toggle down to your shoulder.

But, that is not all that happens:

Let’s take a moment to think about what happens to the pilot during these maneuvers.

You are effectively a pendulum (a weight suspended from a pivot so that it can swing freely).  And we venture to guess that this is not the first time that you have been a pendulum.  If you think back to your childhood days, there was probably a playground involved at some point (hopefully many times) and you got on a swing.  As you were happily swinging along, you were a pendulum, and probably didn’t even realize it.

And for those of you that were super lucky children, you may have experienced the wondrous fair swing.  You eagerly awaited your turn and then rushed for your seat.  The ride started slowly at first when it first lifted off the ground, but then it began to pick up speed and turned faster and faster.

fair swing

And what happened to you as the ride turned faster?

You swung out further from the center and screamed with glee (or terror, depending upon your enjoyment level).  Due to Newton’s Third Law of Motion (for every action there is an opposite and equal reaction) and the relationship between centripetal and centrifugal force, the faster the ride turned the further out the swing occupant was from the center of the ride.

The other thing that happened on that fair swing is that you began to feel heavier in your seat due to the increased G’s that your body felt.    Now some people love that feeling, but if you’re not careful it is possible to make yourself light-headed; the blood that is pushed down into your legs has a hard time returning through the veins back to the heart.  Around 5 G’s is when most people lose consciousness, according to the Go Flight Medicine website.pendulum arc

The same things happen when making turns under a parachute.  The faster the turn, the further the jumper swings out from his parachute.  The further out you swing, the longer it will take you to get back under your parachute once you stop your input by returning to full flight.  And this explains why turns low to the ground hurt tremendously.

Is it possible to keep your parachute above you while turning?

Yes!  Slower turns will not have such a pendulum effects and there are also marvelous turns called flat turns that can be very useful during the times when you would like to make a turn and conserve as much altitude as possible.  But, we’ll discuss flat turns at another time.

Go ahead on your next jump and notice the difference between making small toggle turns and dramatic toggle turns (lots of clear airspace needed here).  While you’re at it, look up at your parachute and notice where your brake lines attach to the parachute.  Keep your eyes on the tail of the parachute, and see how far down you need to pull your toggle before you begin deflecting the tail.  Have fun and ensure you are in clear airspace above 2500’ before performing any of these maneuvers!

Next in this parachute flight series: front riser turns.

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