The colder temperatures of winter weather brings certain concerns that the safety conscious pilot should review both at the start of the season and before each flight.
Leaky O-rings
Many pilots are still using burners that require O-rings. The newer burner designs have eliminated these rubber gaskets that caused the space shuttle Challenger to explode. Take a lesson from NASA and accept that an O-ring leak is a disaster waiting to happen.
O-ring leaks are caused by the different rates of contraction of the metal housing and the rubber O-rings in the blast valve. Generally these will disappear as the valve is actuated and thereby warmed. If O-ring leaks were a problem last year, you will likely see them again this year. It is wise to have the blast valve serviced by your repair station at the start of the season and the O-rings checked and replaced if needed.
Fuel lines
Cold weather will cause fuel lines to become brittle. This can
lead to cracks and leaks. Checking your system with the "sniff
and smell" method may not be satisfactory in winter as your
senses are less responsive in cold weather. Such things as winter
colds and nasal congestion also interfere with your sense of
smell. Cold temperatures slow the rate of vaporization from a
propane leak so always do a thorough pre-flight check using soap
bubbles.
A super-cold morning will cause contraction leaks at the hose fittings and tank connections. Be sure to check and tighten these before each flight, even though you may have flown yesterday and everything was OK.
Using methanol
Winter is a good time to think about adding methanol to your
tanks to protect against water contamination. Many authorities
feel that the potential for internal tank condensation is greater
in the winter due to the great range of heating and cooling from
heat tapes and vaporization cool down during flight.
Fuel pressure
Where you may normally fly with 100-160 psi in summer, the
freezing and below temperatures in winter cause the pressure in
your tanks to drop below 50 psi. This may not be enough to get
the balloon airborne. Your options for creating the needed
pressure are to heat the tanks or pressurize with nitrogen.
If you use heat tapes, remember that once disconnected from the heat source your tanks will loose some pressure. However, the protective jackets should maintain sufficient heat and pressure for a safe flight. If your drive to the launch site is a long one, think about covering the exposed tank tops with blankets to help retain heat and pressure.
Heat tapes and propane tanks
Give your tapes a good eyeball inspection. Particularly if the
tapes haven't been used since last winter, check for loose wires,
bad plugs and insulation wear. Bare wires and electrical current
do not mix and when you add 15 or 20 gallons of propane you'll
have a recipe for disaster.
Always heat and store your tanks outside and away from other flammable materials. A special ventilated storage space is best. Don't overfill the tanks after a cold morning flight since colder temperatures allow you to pack more compressed propane into a tank. When storing propane tanks, be aware that as a cold morning heats up during the day, tank pressure goes up. An overfilled tank and increasing pressure can cause the safety valves to open, venting propane into your storage area. One loose spark or other source of ignition and you've got a fire.
Cold burner coils
Count on colder temperatures to have an effect on the performance
of your balloon and the burner. Because the cold causes low
vaporization, when you first open the blast valve and run propane
through the cold pre-heat coils the fuel will not vaporize. This
means you will be burning liquid propane. You can recognize when
this happens because liquid propane will burn as a yellow fire
ball rather than the thin blue flame that you are accustomed to
seeing. Once the coils warm, the fuel will vaporize better and
the burner works more efficiently.
The danger is that the yellow fireball can result in a "flame thrower effect," completely filling the mouth of the balloon for the unsuspecting pilot ready to start a hot inflation. Any crew members holding open the skirt and/or throat of the envelope itself could be burned!
To minimize this danger, first test your burner and warm the coils prior to laying the basket over and connecting the cables. Then, make your first inflation burns short and perform test burns to again warm the coils for best performance.
Reaction and response times
The pressure of the fuel system and payload being lifted will
affect the performance of the balloon in cold weather. Low fuel
pressure means your system is less responsive. Payload affects
the amount of heat needed for lift.
Wind speed and pilot skill level are also factors. Slow response time due to low psi requires greater maneuvering space when approaching an obstacle or attempting to land in a field. As for your skill level, how far ahead of the balloon flight profile can you anticipate? Your experience level with the flight conditions will have a direct bearing on how well you can fly safely with low pressure. Combining these elements together and flying safely takes greater concentration on the part of the pilot. Be aware how they affect your flight profile.
Hard landings
When landing, remember that the ground is probably frozen and it
will be like landing on concrete. You may want to consider
padding the basket floor to help absorb impact. Keep in mind that
any stubble left standing in a field may also be frozen and can
damage the envelope or possibly injure a passenger. Whenever
possible, try to land as close as possible to the recovery access
and if separated from your crew, land near a house, shed or
natural outcropping where you and your passengers can seek
shelter from the elements if need be.
Propane Pressure Chart
Temp (F) Pressure
-20 13.5
-10 20.0
0 28.0
10 37.0
20 47.0
30 58.0
40 72.0
50 86.0
60 102.0
70 120.0
80 140.0
90 165.0
100 190.0
110 220.0
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