Landing in Turbulence
by Kim Emerson, S&AT - spring@ulster.netThe easiest and best advice one might offer on flying your parachute in turbulence is, "Don't." That said, let's move on to reality. (Which at the Ranch can mean you stand a good chance of being right where you don't want to be on almost any given jump.)
Turbulence is caused mostly through seasonal or other weather changes such as cool air meeting warm air, northerly winds confronting southerly winds, winter becoming spring, nature saying, "What the hell!" Thermals can offer a toss and twist as well. Even an ostensibly calm day on the ground can have enough thermal activity to give serious challenge to the best canopy pilot among us. For example, a freshly mowed landing field on a hot summer day might give some bump and thump to the ride, and the thermal turbulence coming off the runway is different from the turbulence from the trees of the forest.
Usually we can tell when it's so turbulent and that we should stay on the ground. Canopies might buckle, or fold laterally and snap back into shape with a whack loud enough to bring the morbidly curious out of the hangar, or suddenly catch a down draft causing vertical plunges of a few feet before resuming their troubled flight. It can get to be quite a circus on the landing field as jumpers still on the ground collect in ever increasing numbers by the fence to watch as, load by load, the plane is carrying fewer and fewer jumpers. (Unless the tandem mercenaries are lining up to fill the vacating spaces, their unsuspecting passengers in tow.)
Up high, there is little or nothing to give us concern as turbulence that causes trouble is usually a result of the air activity in relation to the ground and objects on the ground. It's lower to the ground as we're setting up for the landing that we have to be hypersensitive to canopy control, toggle input and timing.
In order to handle landing your parachute safely while in turbulence it is first important to understand that it has never been etched in stone that at all times we must fly in a straight line directly into the wind. While this is nice, it is by no means absolutely necessary for a good stand up landing. Crosswind and downwind landings are very possible and are inherently no more perilous than landing straight upwind as long as it doesn't interfere with the general traffic pattern and direction thereby endangering others. As with driving a car in a relatively straight line we are seldom free of small adjusting maneuvers, so it is with landing in the changing winds. What matters most is that we keep an eye on the line we intend to fly. For example, if you are set up for your landing, have determined where you intend to land and begin to feel a push or drop, make the appropriate adjustments required to maintain that line. Slight toggle input to either direction will help keep the canopy flying straight. It is also vital to recognize that one need not land with toggles pulled symmetrically and evenly from full flight to full flare. You can - and should - be able to flare asymmetrically until you actually touch down if your flight has been shoved to one side. If you notice a push to the right, say, it makes no sense to respond by depressing the right toggle as this will put you into a turn, which is potentially fatal when low to the ground. It is a common beginner's error to follow a push to one side with a toggle input on that same side. Why? Now there's a mystery. Better to compensate by providing input to the opposite toggle, thereby correcting the wind's push so that the canopy maintains the line of flight you had intended and had set up. And don't panic. Make no sudden, jerky moves. It's a simple, smooth maneuver. Just provide enough toggle input to get you back on line.
Another common mistake is to respond to fears of impacting in turbulence by flying in slower flight, in partial flight with the toggles somewhat depressed. This will tend to alter the rigidity of the canopy (which needs to be much like a fixed wing, not a bed sheet over your head) by changing the angle of attack into the wind and slowing your canopy down making it more susceptible to the turbulence rather than less so. You need speed in order to slice through the turbulence and therefore spend less time there, making your way either to cleaner air if there is any, or to the ground and completion of the flight. Full canopy flight and a rigid wing are the best ways to get back safely. It requires trust and a bit of faith to simply let the canopy fly.
In a nutshell, the primary reactions a canopy can be expected to give to turbulence are either a drop - a sudden loss of altitude - a buckling, folding effect, or the push to one side. In all cases, full flight, toggle sensitivity and a determination to maintain line of flight on final are required. Then go pack up and enjoy the day from the ground.
It takes some experience to develop this sensitivity and it certainly wouldn't hurt to do some exercises in more desirable conditions so that you can get a feel for response to input and put it to use when you need it most. Try flying in slow flight and maneuvering your canopy while the toggles are in quarter, half and three-quarter brakes. (Then recover early enough to regain full flight before flaring.)
Kim Emerson is S&TA at the Ranch Parachute Club in Gardiner, NY. |
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