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In discussions of level flight, the terms “flying light” and “flying heavy” are sometimes used and bear explanation. A balloon is said to be “flying light” when the sine wave being described in the air is predominately on the high side of the desired altitude [Figure 7-3, Line B]. Many new or inexperienced pilots tend to fly light, and use the vent line in order to return to the desired altitude; this may create a situation where the pilot gets into a constant overcontrolling exercise and is best avoided. “Flying heavy” can be described as a scenario where the sine wave is predominately on the low side of the desired altitude [Figure 7-3, Line C]; if the balloon is left alone, it tends to fall. Flying heavy can be hazardous when contour flying. A balloon pilot must use all visual cues available and exercise a “finesse” type of control when contour flying (described later in this chapter).
Through experimentation, standards can be established that may be used as a basis for all flights. With practice and using the second hand of a wristwatch, a new pilot can fly almost level. The exercise of learning the pattern of burns (each day and hour is different) is an interesting training exercise, but not a practical real-life technique. The ability to hold a hot air balloon at a given altitude for any length of time is a skill that
7-4
A
BC
Figure 7-3. Example of normal flight (Line A), flying light (Line B), and flying heavy (Line C).
comes only with serious practice. Unfortunately, most pilots do not spend enough time practicing level flight. During the practical test, given a choice of altitudes, it is easier to fly level at a lower altitude, due to the ease of acquiring visual references. However, the pilot must exercise care not to violate minimum safe altitude requirements (explained later in this chapter), and must be constantly alert for obstacles such as power lines in the flightpath. Ascents and Descents
The temperature of the air inside the envelope controls balloon altitude. A balloon that is neither ascending nor descending is in equilibrium. To cause the balloon to ascend, increase the temperature of the air inside the envelope. If the temperature is increased just a little, the balloon seeks an altitude only a little higher and/or climb at a very slow rate. If the temperature is increased significantly, the balloon seeks a much higher altitude and/or climbs faster. If the balloon is allowed to cool or hot air is vented, the balloon descends.
Even without the input action by the pilot, it must be remembered that the air inside the envelope is dynamic. The air mass is constantly moving within the confines of the envelope, attempting to seek a level of equalization. While it varies with each envelope, input action by the balloon pilot can take from 6 to 15 seconds to be realized as a reaction by the balloon. Planning the maneuver, anticipating the reaction time, inputting the proper burn, and observing the reaction must result in smooth and natural movement by the pilot.
Ascents
Using evenly spaced, identical standard burns to fly level, a pilot needs to make only two consecutive burns to have added excess heat to make the balloon climb. For example, if the pilot can maintain level flight with a standard burn every 35 seconds, and then makes two burns in succession instead of one, the balloon has an extra burn and climbs. How fast the balloon climbs depends on how much extra heat has been added. Under nominal conditions, if the standard burn has been made to hold the balloon at level flight and a second burn is within a few seconds (not waiting the 35 seconds), the average balloon starts a slow climb. Three consecutive burns results in a faster climb.
Once the desired climb rate is established, return to the level flight routine to hold the balloon at that rate. The higher the altitude, or the faster the rate of climb, the shorter the interval between burns. In an average size balloon (usually a 77, 000
7-5
A
BC
Figure 7-4. Ascent schematic.
or 90,000 cubic foot envelope) at 5,000 feet, the pilot may be required to make a standard burn every 15 to 20 seconds to keep the balloon climbing at 500 feet per minute (fpm). At sea level, the same rate may require burning only every 30 to 40 seconds. Burn rates cannot be predicted in advance, but practice provides a basis to begin with and experimentation finds the correct burn rate for a particular day’s ambient temperature, altitude, envelope size, and balloon weight.
Another skill to develop in ascents is knowing when to stop burning so the balloon will slow and level at the chosen altitude. The transition from a climbing mode to level flight involves estimating the momentum and coasting up to the desired or assigned altitude. One methodology is illustrated in Figure 7-4. During this flight, the pilot has decided to leave his current altitude (A) and climb to another (C). While climbing, the pilot adjusts burn times to be at a 100 fpm rate of climb by the time he or she is at a point 100 feet below the desired altitude (B). Under most circumstances, the balloon “coasts” the additional 100 feet and rounds out, or resumes level flight, at the desired altitude. It may be necessary to use the vent for a short time to stop the ascent with caution not to vent excessively, thereby causing the balloon to go into a descent. The balloon pilot must remember that each manufacturer has a specific interval that the vent can be opened while in flight. Should that interval be exceeded, it can have a disastrous result. With practice and application, the pilot can learn this skill without the use of the vent, not only conserving fuel, but also flying a much more controlled flight.
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Balloon Flying Handbook(86)
