as long as the information is available and consulted when appropriate. 

Using the chart in Figure 3-13 , determine the maximum gross lift that may be expected on a 60 °F day, with decisions not to exceed 190 °F envelope temperature and 1,500 feet pressure altitude. In this example, the established parameters equate what many pilots consider when doing performance planning. They decide they do not want to exceed a given altitude or envelope temperature.) To determine the maximum gross lift available, the nomograph should be entered at point A, at the ambient temperature of 60 °F. Move right, to the line indicating an envelope temperature of 190 °F (point B). Then, move down vertically to a point equidistant between the lines denoting altitude of 1,000 and 2,000 feet (point C). Then, move horizontally to the left to the gross lift axis of the chart and read the result (point D). In the illustrated example, this computation results in a maximum gross lift of 1,120 pounds. 

Using the chart again in Figure 3-13 , determine the maximum altitude to which the balloon may climb, given the same maximum gross lift figure of 1,150 pounds. In this example, it is simply a matter of extending the lines appropriately. The A-B line would be extended to the diagonal line indicating a maximum temperature of 250 °F (which is the maximum continuous operating temperature for most balloons). Then, a perpendicular line would be drawn from that intersection point. After that line is drawn, extend the C-D line to the right, and the intersection of those two lines will indicate the maximum altitude. In this example, this computation results in a maximum altitude of 10,000 feet. 

## Special Conditions 

Most balloon flying is done in non-hostile terrain and benign weather. There are, some instances in which the terrain may be more difficult, both for the pilot and the chase crew, and the weather may become a significant factor. With proper preflight planning, the problems inherent in mountain flying and cold weather flying can be resolved. While somewhat riskier than normal flying, this type of flying can be safely conducted. 

## Cold Weather Flying 

Some pilots prefer flying in cold weather, which offers the advantages of more stable air and less fuel consumption to maintain flight. This means long, gentle flights for the pilot. There are two main disadvantages to cold weather flying: the need to maintain adequate pressure in the balloon’s fuel system and the difficulty of keeping the pilot, crew, and passengers warm. 

As propane gets colder, it has less vapor pressure. (See chart of propane and butane partial pressures, Appendix C). To ensure adequate pressure in cold weather, follow the manufacturer’s recommended method, which will be described in the flight manual. Many manufacturers recommend the use of nitrogen, an inert gas that may be added to the fuel tanks by means of a regulator. This is perhaps the easiest way to pressurize tanks, as it may be done on site, and with little or no prior planning. It does require the use of a nitrogen tank and a two-stage regulator. These items must be available to the pilot before the flight. If the flight is cancelled after pressurization, and the anticipated rise in temperature is expected to be more than 30°, the pressure will need to be bled off by using the fixed liquid level gauge. 

Balloon systems using a vapor feed pilot system may not be able to use nitrogen as it can result in an unreliable pilot light. Those systems commonly use heat tapes or heated tank covers in order to warm the propane. Heat tapes, similar to those used to prevent water pipes from freezing, are reliable. They do require frequent inspection, as normal wear and tear may cause an electrical short, with potential danger of damage to the fuel tanks. Among the aftermarket types of heat tapes, the ones with an internal thermostat will cycle once a particular temperature is reached, reducing the possibility of overheating the tanks. 

Use tank heaters and heat tapes with extra caution. Tanks must not be heated in an area within 50 feet of an open flame, near an appliance with a pilot light, or in a closed area without natural ventilation. 

Pilots, as well as crew, should be dressed appropriately for the environment. Layered clothing that entraps warm air is standard cold weather gear. Note that cold weather environments commonly promote static electricity. It is important that clothing of natural fibers be used, rather than synthetics. A hat is important, as significant body heat escapes from the head. Warm gloves and footwear are a must. Remember that certain types of hypoxia, or lack of oxygen to the brain (discussed in Chapter 9, Aeromedical Factors), may be aggravated by exposure to continued cold. Pilots and crew should be aware of the symptoms of hypothermia and frostbite, guard against them, and have a plan in place to deal with potential medical emergencies. 

From an equipment standpoint, the balloon requires no special preparation, other than insuring proper pressure in the fuel system. Pilots should be aware that seals and O-rings may shrink somewhat or become brittle in cold weather. This may cause a propane leak, and special caution should be taken 

