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The quick fill design dates from the mid 20th century. A natural shape envelope is surrounded by vertical support tapes that run from the apex of the balloon down to the gondola. [Figure 11-3] Several horizontal tapes extend circumferentially around and are attached to the vertical tapes to stabilize the structure.
Inflation is accomplished by laying out the envelope on the ground along its full length with the apex at one end and the appendix (base) at the other. The gondola is attached to the load lines and is bagged down. As the lifting gas is flowed in through the appendix, several crew members hold the apex of the balloon down. When enough gas has entered the envelope to generate approximately 100 to 150 pounds of net lift, the apex is released, the envelope rises, and the inflation is completed.Lifting Gases
Modern gas balloons normally use helium or hydrogen as the lifting gas. Anhydrous ammonia and methane are two other less common options. Helium is a monotomic, inert gas and must be refined to reach a purity of greater than 99 percent from raw well gas at a purity of a few percent. Hydrogen typically exists in the molecular form H2. It is flammable when combined in a mixture of 25 percent H2 to 75 percent air. This means that this mixture supports an existing flame.
11-4
Figure 11-4. Maneuvering valve on quick fill gas ballon.
Figure 11-5. Typical gondola layout.
Helium is expensive but is more commonly used in the United States while hydrogen is more common in Europe. Helium provides slightly less lift than hydrogen but is the more stable gas. (See subsection titled Flying in Inversions on page 11-7 for a discussion of stability.) Balloon systems must not be prone to generating static electricity if they are to be used with hydrogen.
There are at least six factors to consider when choosing a lifting gas. These are:
1. Compatibility with the balloon system being used
2. Cost
3. Lifting capacity
4. Availability
5. Locale of flight
6. Inherent gas stability
Normally, the gas selection process starts with the type of balloon. Hydrogen can be used if the balloon system is hydrogen compatible, hydrogen is available, and local ordinances allow its use. If one of these conditions is not satisfied, as is often the case in the United States, then helium is the likely choice. If a very short training or pleasure flight of several hours is planned, the more economical alternative of ammonia or methane (natural gas) may be considered.
When inflating or landing with hydrogen or methane, care must be taken to ensure that no flame or material with the potential to generate sparks is present in the launch locale. Lighted cigarettes, cigars, nylon clothing, cell phones, and other electronic devices are examples of forbidden items. Only essential personnel should be allowed in the launch and landing areas. For long, competitive flights, the increased stability of helium is a factor in its favor.
Components of the Gas Balloon
Gas balloon systems can be broken into four parts:
1. Envelope to contain the lifting gas
2. Gondola for carrying pilots and equipment
3. Support system to connect the envelope to the gondola
4. Other equipmentEnvelope
The maneuvering valve [Figure 11-4] is at the apex of the envelope. It allows for the controlled release of a small amount of gas to initiate a descent. It is usually spring actuated and controlled via a line that runs from the valve down through the envelope into the gondola. On some balloons, a gas tight parachute top may be used instead of a valve. The envelope is also equipped with either a rip panel or deflation port for rapid, total deflation during high wind landings. More information on proper use of the valve and deflation ports is provided in the section The Practice of Gas Ballooning, page 11-8.Gondola
The gas balloon’s gondola [Figure 11-5] is typically somewhat larger than ones used for sport hot air ballooning, with four by five feet being a typical size. A foldable cot or sleeping pad normally runs along the long side of the gondola and a “kick-out” panel in the side wall at one end of the cot may be used to provide additional legroom for sleeping.
A trail rope is slung on the outside gondola along with much of the remaining support equipment. The trail rope is typically about 150 feet of natural fiber rope, one inch in diameter and weighs about 40 pounds. Its use is described in the landing paragraph. Support Cabling
The connection between envelope and gondola may be made of rope, flat tape, or steel cable. The total strength of the
11-5
Figure 11-6. Instruments and radios are sometimes carried in a pod such as this.
cabling should have a breaking strength of at least five times the maximum gross load that is suspended on the cables. This must include sand ballast, as well as the weight of the gondola, the occupants, and all supplies and equipment.For hydrogen systems, the cabling must be electrically conductive. For ammonia systems, the cables should be long enough to separate the occupants of the gondola from gas fumes coming out of the appendix.
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Balloon Flying Handbook(133)
