Antenna Tower 1,000' 1,000' 2,000' 500 feet 500 fee t $^{50}$0  feet 500 feet 500 feet $_{Figure 7-9}$  Minimum safe altitude over a sparsely populated  area. $_{Figure 7-8}$  Minimum safe altitudes over a congested area. 14 CFR part 91, section 91.119(c) refers to two area types:  sparsely populated and unpopulated. Here, the pilot must stay  at least 500 feet away from persons, vehicles, vessels, and  structures. “Away from” is the key to understanding this rule.  The regulation specifies how high above the ground the pilot  must be and also states the pilot may never operate closer  than 500 feet. There exists a possibility for misunderstanding  in interpreting the difference between congested and other  than congested, as neither of these terms are defined by the  FAA regulations. As an example, operating below 1,000 feet  AGL within 2,000 feet of a congested area is in violation of  14 CFR part 91, section 91.119(b), even though the bordering  area may be used only for agricultural purposes. Therefore,  when flying over unpopulated land near a housing tract, the  balloon must fly either above 1,000 feet AGL or be 2,000  feet away from the houses. To stay 500 feet away from an isolated farmhouse, imagine  a 1,000-foot diameter clear hemisphere centered over the  building.  [Figure 7-9]  If the balloon is 400 feet away from  the structure on the horizontal plane, the balloon pilot only  need fly about 300 feet AGL to be 500 feet away from it. If  the balloon passes directly over the building, then there must  be a minimum of 500 feet above the rooftop, chimney, or  television antenna to be legal. Aside from the legal aspects, contour flying is probably the  most difficult flying to perform. The balloon pilot must see all  obstacles on or near the balloon path, remember their location,  and maintain situational and spatial awareness. Terrain or  obstacle height must be estimated and allowed for, and the  pilot must always be prepared for an unexpected situation.  A relationship must be established between the balloon  altitude and the terrain or obstacle height. All these mental  calculations must occur in a few seconds, in a continuous  cycle, as the pilot executes a complicated flight profile. In those cases, the balloon may not be operated closer than  500 feet to any person, vessel, vehicle, or structure. This is  an easy to understand regulation that requires compliance  from all pilots.  The balloon practical test standards (PTS) asks the applicant  to demonstrate contour flying by using all flight controls  properly to maintain the desired altitude based on the  appropriate clearance over terrain and obstacles, consistent  with safety. The pilot must consider the effects of wind gusts,  wind shear, thermal activity and orographic conditions, and  allow adequate clearance for livestock and other animals. In summary, regulations require:  Since most contour flying is done in unpopulated areas, the  balloon is rarely higher than 300 feet AGL and frequently  much lower; therefore, the balloon’s flight instruments are  seldom observed. Because mechanical instruments have  several seconds lag and electronic instruments are very  sensitive, pilots must rely on their observation and judgment.  7-10 1. Flying high enough to be safe if a problem occurs;  2. 1,000 feet above the highest obstacle within a 2,000- foot radius above a congested area; and  3. An altitude of 500 feet above the surface, except over  open water or sparsely populated areas.  Contour Flying Techniques