Paragliders and Spiral Dives

Robert W. Cunningham wrote

I have only just learned to do a spiral dive and on my second attempt inadvertently rather overdid things. It was not until I felt my face begin to distort that I realised I had better ease off.

Meanwhile my husband (not a paraglider pilot) had noticed the tips of my wing begin to fold in.

My questions are:

why did this happen?? Was I doing anything wrong (apart from being over ambitious!)? Should I have been aware of what was happening (yes, undoubtedly - but aware of what?)

performance regions >you might otherwise reach only in an uncontrolled situation.

Yes, thats one reason why I wanted to try them out - and then again, it did feel good!!

Remember, in a SPIRAL DIVE, there is a significant crosswind going across the wing. The wing is trying to fly in the direction the leading edge points, but the rotation is forcing one tip into the turn, with the rest of the wing following. Also, the tips of the wing never bear as much weight per unit area as the central portions of the wing. So I would not be at all surprised if the tip that is 'leading' the turn starts to come in. This may happen independent of the level of G forces you are experiencing.

What to do about it depends on the wing. In most cases, it is not a problem for one or two feet of the leading tip to come in, just so long as you know it will come out easily (or on its own) when exiting the maneuver. My Minoa, on the other hand, occasionally likes to gobble up a large chunk of the tip and threaten to create a cravatte. I first try a little brake to puff it out (seldom works), then I abort the maneuver.

There should be no circumstance in which BOTH tips come in! The only way I can even guess this would happen is if the wing started to lose pressurization due to turbulence at the leading edge caused by too rapid rotation. In this case, having both tips come in might be the only warning before a full frontal collapse. And I have no desire to figure out the recovery strategy for THAT situation!

One maneuver I have done was to exit a SPIRAL TURN with a B-line stall. It took all my upper body strength to initiate the stall while in the spiral, but the effect was quite startling. Instantly, my rotation ceased and I continued at high speed in a sideways arc toward the ground. It took only a moment for the canopy to stabilize above me (I don't call it a wing when it is not flying), after which I released the stall normally. Observers on the ground claimed it looked like I was one of those toy soldiers on a parachute being thrown out of a car.

And when I said it took all my strength to initiate the B-line stall, I meant it. I wound up tearing muscle in my biceps and lats, and had several days of discomfort. Of course, when I first considered the maneuver, I had no idea it would take that much force. The reason I pushed it that hard was simple: Once a maneuver is started, it should NOT be stopped until it is completed! Exiting badly from a partial B-line stall can (in the worst case) lead to a frontal collapse, severe surge, or a constant (parachutal) stall. I have no idea what the worst case is when doing it from a spiral. I was in a 3G spiral doing pull-ups on my B risers. I figure I was trying to lift well over 300 pounds! Not bad for a skinny guy, eh? Needless to say, I haven't repeated that stunt since.

facinating discussion. My Saber 170 does great sprial dives.... almost all the way to the deck, without end cell closure.... Ah, but that's a different machine. .... Only better way to get down is a two or three man down plane.

Blue skies,

<snip>

I have the same problem in a spiral dive if I am not carefull. In a spiral dive the forward speed of your canopy will seriously exceed the normal flying speed. This causes a lot of air resistance on the front of the canopy, especially the outside which will have a much higher speed then the insdide tip. This will cause the outside tip of your glider to be pressed closed. This can lead to a partial frontal collapse. The best remedy for this seems to be very light breaking on the opposite side. During a spiral dive, always keep an eye on your leading edge, and apply just enough counter breaking to keep the tip in shape. Don't apply this before you enter, or your speed can drop so much you'll go negative.

Greetings, Eelco

I just hat a look on my wing handbook. DHV tested it to 8 m/s. Crucial parameter is, if the wing exits the dive on its own when releasing the brakes. It did, says the report.

I did a 12m/s spiral dive, and was not happy (although many people claim it to be fun). It still came out on its own. My flying teacher told me that this type of wind (UP Vision Classic, sort of low intermediate) has some tenency to stay in the dive when reaching 15 m/s descent. The way to exit is to apply slowly the outward brake.

So does my Extreme 109 (loaded at 2.1).......and every other ram air I've owned in the last 27 years from rings 'n rope strato stars, safety flyers, clouds, merlins, Sabers, comets, mantas....everything can be spun until the top edge is below the horizon without 'blackout' or end cell closures. or other nonsence....just because you've built a wing with a higher aspect ratio shouldn't mean they fall apart if you have too much fun; you guys need a better wing and I mean NOW, before you start counting bodies.....oh yah, and a reserve is a stupid waste of money. That from a guy who jumps a cypress!

Hey, Bob,....I'll do a down plane with the PPGs if we can get it on film!

Urrrrghhhhh. Could you please check your settings and set it to post text only? Thanks.

Matter of taste It is pretty violent, and a good adrenaline rush. Some people tend to get dizzy. Only do these kind of manouvres when you feel confident with them.

For the faster gliders it is often better to steer out of a spiral dive actively. This to prevent collapses and other nasty things. As I have learned it: First you sit up straight, or even use weight steering opposite to the rotation. Then slowly release the breaks a bit. You can keep the counter breaking (done to prevent deflation of the outer-side-of-the-turn-wingtip) the way it was. When you're glider tilts back to normal flying position, release both breaks to build up speed. During release, always keep the lines under tension. This means that when you release your breaks, but loose tension entirely when you still haven't let them up entirely (for example at the level you normally have for 20% breaking), you keep them there. That way you can always feel what your wing is doing.

Greetings, and happy spiralling,

Eelco Giele wrote

I was told not to use any counter breaking for a spiral - so should I, or shouldn't I?? (I am only a beginner at this and my glider is a standard one - Ozone Electron)

That's what I want!

It depends on your glider. If it spirals without, go ahead and don't counter break. I have to with my glider and with my weight. The best thing for spiralling is of course to practice it a few times under supervision of a flight instructor. They know the glider, they can see what is happening and they can give the information you need.

Greetings, Eelco