place in an uninhabited area and the obstacle should be a  simulated obstacle. The experience of being caught in a thermal can certainly  occur at any altitude, but is more common during the landing  phase of balloon flight. This is primarily due to the balloon’s  proximity to the ground and being exposed to the conditions  that cause thermals.  [Figure 8-8] A drop-in landing or steep approach to landing is another good  maneuver to practice. Being able to perform this maneuver  can get the balloon into that perfect field that is just beyond  the trees or just the other side of the orchard. A pilot that is  able to drop quickly, but softly, into the fallow field between  crops is more neighborly than making a low approach over  the orchard. Being able to avoid frightening cattle or other  animals during an approach is a valuable skill. There are indicators of thermal conditions that may be  visible to the pilot, such as “dust devils” or small tornados  visible from the ground. An uncommanded ascent, usually  at a significant climb rate, may be experienced, or perhaps  significant changes in direction. In the extreme, a balloon  caught in a tight (compact) thermal may even create small  horizontal circles in the sky. Having the skill to predict the balloon’s track during the  landing approach, touching down on the intended landing  target, and stopping the balloon basket in the preferred place  can be very satisfying. It requires a sharp eye trained to spot  the indicators of wind direction on the ground. Dropping bits  of tissue, observing other balloons, smoke, steam, dust, and  tree movement are all ways to predict the balloon track on its  way to the landing site. During the approach, one of the pilot’s  most important observations is watching for power lines.  There are two rules to thermal flight. First, the pilot must  continue to fly the balloon. Many pilots are distracted by the  thermal flight experience and may forget that the balloon is  cooling at a faster than normal rate. The pilot should ensure  that the temperature of the balloon’s envelope is kept at or  above that required to maintain normal flight, and under  no circumstance should the pilot allow the balloon to cool.  The temperature noted at equilibrum should be a minimum  temperature to maintain. Additionally, the pilot should not  In ballooning, approaches can be practiced more often than  landings. A good approach usually earns a good landing. $_{Figure 8-8.}$  Anatomy of a thermal. A thermal is created by the uneven heating of the surface of the Earth by solar radiation (insolation).  As the sun heats the ground, the ground in turn warms the air above it. Warmer air is less dense, and therefore rises; as it rises, it cools  due to expansion. This heating/cooling pattern sets up a cycle, whereby a downward flow is created outside the thermal column one the  air has cooled to a temperature equal to that of the surrounding air. This can create a hazardous situation for a balloon pilot; the best  action is to maintain buoyancy, and wait for the column to dissipate. 8-8 Thermal Flight