TANK
0 250
PSI
80 160
Pilot valve
Pressure gauge
Pilot light
Liquid valve
Blast valve
Nozzle
Heat exchangers
Figure 2-8. Fuel system schematic.
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.
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 helps with balloon landings and cushions some of the impact
force at landing. The basket contains the fuel tanks, instruments, pilot, and passengers.
Figure 2-9. Representative sport basket configuration.
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]
MAIN LIQUID VALVE
FUEL QUANTITY GAUGE
LIQUID LEVEL VALVE
LIQUID LEVEL PICK-UP
LIQUID PICK-UP (DIP TUBE)
QUANTITY FLOAT6
TYPICAL FUEL TANK (VERTICAL)
Figure 2-10. Typical fuel tank
The tanks, sometimes referred to as pressure vessels, are commonly equipped with a service valve (or main liquid valve), a
fixed maximum liquid level gauge (or “spit valve”), a float gauge, and a pressure relief valve. The service valve regulates
the flow of the liquid propane to the heater. The fixed maximum liquid level gauge provides an indication that the tank is
filled to its maximum design quantity, or 80 percent of the total capacity of the tank. The float gauge provides a reading of
the remaining capacity of the tank in a percentage. The pressure relief valve allows for the release of propane from the tank
should the tank exceed the maximum design pressure. A pressure relief valve normally releases at 375 pounds per square
inch (psi). Figure 2-11 provides additional information on propane management.
Propane Primer
Propane is a liquefied petroleum gas. Propane is preferred over butane and other hydrocarbons in balloon
design because propane has a lower boiling point (propane -44 °F, butane 32 °F), and, therefore, a
consistently higher vapor pressure for a given temperature. Under ideal circumstances, a gallon of propane
produces 91,600 BTU of heat.
In its gaseous form, propane is odorless. However, an odorant (a strong smelling chemical compound) is
added to propane to indicate the leakage of even small quantities of gas. The odorant normally added to
propane, ethyl mercaptan, loses its odor when burned. Tanks should never be stored in an enclosed area,
or near a heater and/or a device with a pilot light. Propane vapor is heavier than air, and will collect in low
areas. Concentrated propane vapor constitutes an explosive hazard.
There is a popular misconception that propane is always at -44 °F when stored. This is incorrect—the
propane, in the tank, is the same temperature as the ambient air. Propane turns cold when vaporizing, due
to heat exchange.
The combustion of propane yields carbon dioxide and water.
The balloonist should be aware of the large volume of combustible mixture that will result from the escape
of a small amount of liquid propane. As a rough approximation, a given volume of liquid propane produces
a combustible mixture 6,800 times the original liquid propane volume.
The propane cylinder raises the boiling point of propane by trapping the pressure built up by the vaporized
propane. Any given temperature will produce a specific pressure within the propane cylinder. This balance
between temperature and pressure is referred to as the point of equilibrium. As long as the propane
cylinder is neither completely full nor completely empty of the liquefied fuel, and no foreign substance such
as air is present, the pressure within the cylinder is dependent upon the prevailing temperature of the liquid,
and not upon the amount of liquid propane within the cylinder. Therefore, maintaining a proper propane
temperature is necessary to supply sufficient fuel pressure to the burner. The temperature-pressure point
of equilibrium is only applicable to containers containing vapor over the liquid. While propane vapor is
easily compressible, propane liquid is practically incompressible.
Butane-propane mixtures can be a problem. At certain times of the year in certain areas, butane will be
mixed with propane to increase its boiling point. A butane-propane mixture will produce a more yellow,
sooty flame, may tend to go out when the blast valve is pulled, and the pressure available for a given
temperature will be less.
Burners commonly used in hot air balloons are vaporizer burners. A vaporizer burner combines a vaporizer
with a burner into a single unit where burner heat is used to vaporize the liquid propane being fed into the
burner. The vaporizer normally consists of a coil in direct contact with the burner flame. If there is no fuel
flow through one of the coils during burner operation, the coil may be damaged as a result of overheating.
The heat output of a burner is one of the parameters that indicate how a given balloon will perform in flight.
A long sustained burn will produce a lower rating that the same time increment broken up into short burns.
The lower output for a sustained burn is due to the inertia of the fuel, the friction hindering fuel flow, and
pressure decay due to the withdrawal of liquid propane from the cylinder.
Periodic inspections of the airborne heating system should include a visual inspection of the hoses and
fittings, and a high pressure leak check with a test gauge adaptor.
Source: Saum, Nick. “Propane and Fuel Management.”
Joint publication of the Safety and Education Committees of the Balloon Federation of America, 1991.
Figure 2-11. Propane primer. (Propane pressures at different temperatures are listed in Appendix A.)
Support Equipment
Standard support equipment for ballooning includes an inflation fan, transport/chase vehicle, and small miscellaneous
items, such as igniters, drop lines, gloves, spare parts, and helmets.
Inflation Fans
The inflation fan is one of the most dangerous pieces of equipment in ballooning.[Figure 2-12] Keep this fact in mind when
purchasing and operating any inflation fan. Fan blades have been known to shatter or break, throw rocks at high velocity,
and inadequate cages or guards fail to protect fingers and hands. Any fan considered for purchase by a prospective pilot
should be evaluated for potential safety hazards. Also, remember that the blade spinning at high revolutions per minute
(rpm) generates a significant gyroscopic effect. Fans should not be moved while running. If the fan must be moved, it
should be shut off, repositioned, and restarted.
Figure 2-12. Balloon inflation using a typical inflation fan.
Fans come in different styles and sizes. Personal finances, style of inflation, and size of the balloon determines the best fan.
Points to consider in selecting a fan are:
• Weight—someone has to lift the fan into and out of the transport vehicle. Wheels help one person move the fan, but
they add to the weight and are not helpful on soft ground. One person can carry a small fan, but a larger fan may
require two people.
• Safety—fan blades today can be wood, aluminum, fiberglass, or composite, with wood being the most popular.
Wood or aluminum blades designed specifically for balloon fan use are best. The fan should have a cowling of
fiberglass or metal because a cage or grill alone is not sufficient to stop rocks or pieces of blade from being thrown.
• Transport—available space in a pickup truck, the back of a van, or on a trailer may determine the size of the fan.
• Cubic feet per minute (CFM)—fan blade design, duct design, and engine speed determine the amount of air moved
in a given time. Do not confuse engine size with CFM. Larger engines do not necessarily push more air. The volume
of air moved is primarily a function of blade design and performance. Moving a high volume of air is not necessarily
the ultimate goal in fan performance. Some people prefer a slower cold inflation to accommodate a thorough
preflight inspection.
• Fuel—gasoline degrades in storage. Do not store gasoline in the fan due to fire hazard and the formation of varnish,
which can clog fuel passages.
• Fan maintenance—a good fan requires little maintenance and should be easy to maintain. Check the oil periodically
and change it once a year. Check hub bolts and grill screws for tightness on a regular basis.
Transport/Chase Vehicle
Balloon ground transportation varies. [Figure 2-13] The most common vehicles are a van with the balloon carried inside,
a pickup truck with the balloon carried in the bed, or a van or pickup truck with a small trailer (flatbed or covered). Some
considerations in selecting a transport/chase vehicle are:
• Finances—if costs are an issue, a trailer hitch on the family sedan and a small flatbed trailer may work just fine.
• Convenience—for ease of handling the balloon, a small flatbed trailer low to the ground makes the least lifting
demands on the pilot and crew. One consideration is that volunteer crew members may have little or no experience
in backing a small trailer.
• Number of crew members—if the number of crew members is small, handling the balloon should be made as easy
as possible. If the number of crew members is large, the size of the chase vehicle and other factors may be more
important.
• Storage—some balloonists, who do not have room for inside storage and want security on the road, choose an
enclosed trailer. If an enclosed trailer is used for storage of the balloon, the trailer should be a light color to help
reduce the heat inside. Keeping the trailer cool keeps the tank pressure within reasonable limits (so as not to
aggravate a potential fuel leak), and reduces the vaporization of gasoline in the fan tank (the fumes can attack the
composition of the balloon’s fabric and render it unairworthy).
• Vehicle suitability—terrain, vehicle road clearance, and number of chase crew members are factors that determine
the suitability of a transport/chase vehicle.
Figure 2-13. This is an example of a transport vehicle which carries a small balloon, three adults, a 20-inch inflation fan, and all
other necessary equipment.
Quick/Safety Release
Safety restraints, referred to as “quick releases” or “safety tie downs,” are used in balloon inflations. They are designed to
restrain the balloon from movement in breezy or windy conditions.
There are several different types of safety restraints available, but none are part of the aircraft certification process. This
lack of aircraft certification has led to controversy over the use of safety restraints among ballooning enthusiasts. Since
event participation often requires their use for safety reasons, the use of safety restraints is now recommended for balloon
launches. Each type of restraint has its own advantages and disadvantages which a pilot can learn via observation and
discussion with an instructor and/or other balloon pilots. When a pilot decides to utilize a safety restraint, it is important to
follow the balloon manufacturer’s recommendations on how to attach it to the balloon superstructure. Many balloons have
been seriously damaged by using an improperly attached restraint in excessive winds.
It is also important to insure that all personnel involved with the inflation, whether pilot, crew or spectator, be aware of
the dangers of a safety restraint. The quick release rates with the inflation fans as one of the most hazardous pieces of
equipment on the launch field. Early release under load, or breaking of the safety restraint may cause serious injury. All
personnel involved should be briefed and made aware of the potential hazards.
Miscellaneous Items
• Radios—most pilots use some kind of two-way radio for air to ground communication. There are many choices
available, ranging from Family Radio Service (FRS) and General Mobile Radio Service (GMRS) radios, which are
relatively low cost, to the more sophisticated FM business band systems, which can be expensive. The GMRS and
FM radios require licensing by the Federal Communications Commission (FCC). FRS radios do not. Using cell
phones for air-ground communications is a violation of FCC rules.
• Igniters—most manufacturers provide at least two sources of ignition on board. The best igniter is the simple
welding striker. Nearly all balloons have builtin piezo ignition systems.
• Fueling adapter—adapters are required to connect the balloon fuel tanks to the propane source. Pilots should carry
their own adapters to ensure the adapters are clean and not worn. Dirty and worn adapters may damage a fuel system.
• Compass—compasses are used to track pibals, check map orientations, and navigate the balloon. While almost any
good quality compass will do, the best kind to use is probably the sighting compass.
• Fire extinguisher—most balloons now come equipped with small fire extinguishers affixed to the basket. If one is
present, it will be inspected during the annual inspection. These fire extinguishers are often too small to extinguish
grass fires or serious basket fires caused by a propane leak. In the case of a propane-leak fire, turning off a valve
usually extinguishes the fire. This is a better use of pilot time than fumbling for a fire extinguisher that might not
extinguish the fire.
• First aid kit—the location and contents of first aid kits vary. Some pilots keep a small first aid kit in their balloon;
some keep one in the chase vehicle. A frequent topic at Safety Seminars, the contents of the kit often depend on the
area of the country in which the balloon is flown.
• Drop line—drop lines allow ground crew to assist the pilot in landing in a confined area, or to move the balloon to
an area better suited for deflation and retrieving. A good drop line has a quick release provision; is easy to deploy,
recover and store; and is easy for a person on the ground to handle. Webbing is a popular drop line material because
it is strong. Webbing is hard to roll up, but easy to store. Half-inch nylon braid is strong and is easily rolled into a
ball and put in a bag.
• Gloves—pilots and crew members should develop the habit of wearing gloves anytime they handle the balloon
and associated equipment. A well fitting pair of gloves can reduce the injuries that occur while handling balloon
equipment, such as rope, cables, bag handles, etc. In the case of a small fuel leak at a burner fitting, gloves can
minimize a potentially disastrous situation. Gloves should be made of light colored smooth leather to reflect/deflect
propane, and gauntlet style to cover the wrist. Avoid synthetic material which melts in heat and ventilated gloves
which let in flame or gas. A second pair of gloves, of appropriate rubberized material and looser fit, can be used to
conduct refueling operations.
• Helmets—balloon manufacturers usually mandate protective headgear be worn, especially in high wind conditions
to protect heads from impact injury. Store helmets in a bag that can be carried inside or outside the basket, depending
on number of passengers and available room.