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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. 

In summary, regulations require: 

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. 

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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. 

## Contour Flying Techniques 

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. 

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. 

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. 

