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] 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.  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. 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  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  Diminished Capacity 6-16 Figure 6-17.  False heavy dynamics. Wind Lift L o w pr ess ure ar e a