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There are two types of pilot light systems: liquid and vapor. In a liquid pilot light system, liquid propane is diverted from the main supply line at the heater via a pilot shut-off valve. The fuel goes through a vapor converter and regulator, and is distributed through a pilot head. A piezo-electric system ignites the vapor at inflation for most heaters, but many balloonists choose to use a striker.
In a vapor pilot light, a second fuel hose is used to supply vapor to the heater assembly pilot light from the pilot light tank valve located on top of the fuel tank. A regulator is used to decrease the pressure of the propane vapor for proper pilot operation. A pilot light valve located on the heater controls the flow of propane vapor to the pilot light.
The main liquid tank valve controls the flow of liquid propane to the burner, while the blast valve controls fuel flow at the heater. With the liquid tank valve open, opening the burner blast permits liquid propane to enter the heat exchange coil where it is either completely or partially vaporized. After exiting the heat exchange coil through the orifices in the lower portion of the coil, the propane is ignited by the pilot light. [Figure 2-8]
To meet redundancy requirements, heaters have a secondary system which allows for operation at a reduced efficiency should a problem develop with the main blast valve. These backup, or bypass systems generally have proprietary names unique to the individual manufacturers. Pilots should consult individual flight manuals for an explanation of their use.
The heaters typically have an output of approximately 20 million British thermal units (BTU) in use. There is a power loss associated with altitude, generally considered to be four percent per thousand feet of altitude. This is particularly important when dealing with higher density altitudes. Pilots accustomed to flying at lower altitudes are frequently surprised by the decreased performance of their balloon upon their first flight at a higher altitude.Basket
Wicker is the preferred material for the passenger compartment basket of a hot air balloon because it is sturdy, flexible, and relatively lightweight. [Figure 2-9] The flexibility of wicker
2-7
F
igure 2-6. Typical fuel tank (vertical).MAIN LIQUID VALVEFUEL QUANTITY GAUGELIQUID LEVEL VALVELIQUID LEVEL PICK-UPLIQUID PICK-UP (DIP TUBE)QUANTITY FLOAT654321162354TYPICAL FUEL TANK (VERTICAL)
Figure 2-10. Typical fuel tank.
helps with balloon landings and cushions some of the impact force at landing. The basket contains the fuel tanks, instruments, pilot, and passengers.
Aluminum, stainless steel, or flexible nylon poles (in conjunction with stainless steel cables) located on the upper portion of the structure transfer the basket load to the envelope attachment points and support the burner assembly. Quick pins or aircraft bolts connect the support tubes, with nylon rods usually inserted into the sockets, and the cables attached around them. Lower frame tubes support the floor, permitting the floor load to be transferred to the lower frames. Oak skids, usually affixed to the floor, add rigidity and provide a point of abrasive resistance to the floor. Rattan sidewalls of varying thickness, design, and color surround and protect the passengers, equipment, and fuel tanks. Larger baskets, usually found on large ride balloons, may have padded basket dividers to form passenger compartments.Instruments
As required by 14 CFR part 31, balloons are equipped with an altimeter, a rate of climb indicator, fuel quantity gauges, and an envelope temperature gauge. Many newer balloons use some type of electronic instrument system, but older balloons may still be equipped with traditional, pressure driven analog instruments.
The most common arrangement of instruments is a small pod or package which includes the altimeter, rate of climb indicator (variometer or vertical speed indicator), and the envelope temperature gauge (pyrometer). A cable is plugged into the instrument package during the preflight or layout process which connects to a sensor located in the top of the balloon and operates the envelope temperature gauge. Fuel quantity gauges, located on the top portion of each fuel tank, provide a reference for the quantity of fuel remaining in the tank. As these gauges are mechanical, they are sometimes inaccurate, and in most configurations do not read from 0 to 100 percent. This needs to be taken into consideration during the flight planning process.
In recent years, many manufacturers have added a wireless system that transmits the temperature signal to a receiver in the basket via a radio or infrared signal. This eliminates the necessity of a wire being located in the balloon envelope. These instrument systems are popular, but have reliability issues because radio interference or the thermal “plume” from the burner can degrade the signal transmission. Fuel Tanks
Balloons generate heat through the use of propane. The propane is contained in aluminum or stainless steel tanks mounted inside the basket. These tanks may be either vertical or horizontal, and contain 10, 15, or 18 gallons of propane. Larger tanks are available for larger ride balloons. [Figure 2-10]
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Balloon Flying Handbook(23)
