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This phenomenon occurs when descending into a faster moving air mass or wind shear. The lower half of the balloon enters the shear and the surface of the balloon allows the air flow to generate lift. This lift is tangent to the surface of the balloon. Because it is below the equator, where the tangent line points in a downward direction, the lift has a downward component. This downward component of lift pulls the balloon down. [Figure 6-17] 

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This effect is more severe on a fully loaded balloon than a lightly loaded one, by reasons of skin tension. A lightly loaded balloon has more slack in the fabric on the lower portion of the balloon. On a heavily loaded balloon, the fabric below the equator has greater tension providing a surface where a low pressure can develop. 

A scenario having much less impact is fast moving air across the mouth of the balloon. This creates a dynamic low pressure, similar to a venturi, which may cause the air to be pulled out of the envelope. As the air moves over the mouth of the balloon, it creates the dynamic low pressure, which pulls the static air inside the envelope out. Of all the possibilities discussed here, this point has the least impact on the lifting capability of the balloon, but is important when standing on the ground following the initial inflation to equilibrium. 

## Diminished Capacity 

Another way in which a wind shear can increase the rate of descent is by diminishing the capacity of the envelope. For example, when descending, below is a low level wind shear with the air near the surface moving much faster or slower than the air mass in which the balloon is traveling. As the balloon enters the lower air mass, the side of the balloon is pushed in, decreasing the capacity of the envelope and pushing the air out the mouth. The larger the difference 

between the speed of the two air masses, the greater the effect. The lift created by buoyancy is decreased and the balloon starts to descend. If this happens at a low altitude, and the pilot has not responded in a timely manner, this may result in a hard landing. 

If a balloon descends abruptly from a 30 mph wind into a 15 mph wind, it experiences an effective abrupt increase in wind across its surface from no wind to a 15 mph wind. This removes the boundary layer on its surface and greatly increases heat lost by conduction, while causing distortion in the form of a “dish.” This condition is very dangerous to the low level flight of a fully loaded balloon. It should be noted that as the envelope lowers into the slower wind and begins to distort and slow-up, the effective wind speed over the top begins to increase. Air moving over the top of an envelope produces false lift. Combined with diminished capacity, this again presents a hazardous condition which may result in an extremely hard landing. 

“Dishing” usually does not affect the flight path of a lightly loaded balloon as much as a more heavily loaded balloon because no internal lifting heat is dumped; it is only redistributed inside the distorted envelope. To understand what a “dish” can do to lift, the balloon pilot needs to understand how the “heat line” fluctuates under different loading conditions. A balloon “floats” in the air because the hot air inside it weighs less than the volume of air it displaces. Usually the bottom of the heated air is down close to its mouth. Notice that a normal two-second single burn on a heavily loaded balloon adds only a small percentage of heat compared to its total required hot air volume. The same burn in a lightly loaded balloon adds a much larger percentage of lifting heat compared to its total required hot air volume. This is a simple way to visualize responsiveness. 

If a heavily loaded envelope experiences a major “dish,” important lifting heat can be squeezed out. This condition is extremely serious if on a final approach to landing because there is not enough time and altitude to add enough heat. Remember, not only must the heat loss be replaced to make the balloon neutrally buoyant, but more must be added to stop any downward momentum. 

Heat loss can change the slope of the approach and, pilot unaware, make it steeper. The stronger the shear, the greater the change in slope. Knowledge of this and the importance of adding heat quickly could prevent an excessively hard landing or an accident. 

Some signs of shear to watch for are any movement of crown lines, handling lines, throat ropes, skirt, or even basket movement. It is important to realize that as the balloon lowers 

