Piloting a balloon takes skill, but the controls are actually very simple.
To lift the balloon, the pilot moves a control that opens up the propane
valve. This lever works just like the knobs on a gas grill or stove: As
you turn it, the flow of gas increases, so the flame grows in size. The
pilot can increase the vertical speed by blasting a larger flame to heat
the air more rapidly.
To blast the burner, the pilot
opens the propane valve
Additionally, many
hot air balloons have a control that opens a second propane valve. This
valve sends propane through a hose that bypasses the heating coils. This
lets the pilot burn liquid propane, instead of propane in gas form.
Burning liquid propane produces a less efficient, weaker flame, but is
much quieter than burning gas. Pilots often use this second valve over
livestock farms, to keep from scaring the animals.
Hot air balloons also have a cord to open the parachute valve at the top
of the envelope. When the pilot pulls the attached cord, some hot air can
escape from the envelope, decreasing the inner air temperature. This
causes the balloon to slow its ascent. If the pilot keeps the valve open
long enough, the balloon will sink.
The parachute valve, from the inside of the balloon.
A Kevlar cord runs from the valve at the top of the balloon, down to the
basket, through the centre of the envelope
Essentially, these
are the only controls -- heat to make the balloon rise and venting to make
it sink. This raises an interesting question: If pilots can only move hot
air balloons up and down, how do they get the balloon from place to place?
As it turns out, pilots can manoeuvre horizontally by changing their
vertical position, because wind blows in different directions at different
altitudes. To move in a particular direction, a pilot ascends and descends
to the appropriate level, and rides with the wind. Since wind speed
generally increases as you get higher in the atmosphere, pilots can also
control horizontal speed by changing altitude.
To manoeuvre the balloon
horizontally, the pilot ascends or descends in altitude, catching
different wind currents
Of course, even the
most experienced pilot doesn't have complete control over the balloon's
flight path. Usually, wind conditions give the pilot very few options.
Consequently, you can't really pilot a hot air balloon along an exact
course. And it's very rare that you would be able to pilot the balloon
back to your starting point. So, unlike flying an airplane, hot air
balloon piloting is largely improvised, moment to moment. For this reason,
some members of a hot air balloon crew have to stay on the ground,
following the balloon by car to see where it lands. Then, they can be
there to collect the passengers and equipment.
Launching and Landing
A lot of the work in hot air ballooning comes at the beginning and the end
of the flight, when the crew inflates and deflates the balloon. For the
spectator, this is a much more spectacular show than the actual balloon
flight.
Once the crew has found a suitable launching point, they attach the burner
system to the basket. Then they attach the balloon envelope and begin
laying it out on the ground.
Once the envelope
is laid out, the crew begins inflating it, using a powerful fan at the
base of the envelope.
When there is
enough air in the balloon, the crew blasts the burner flame into the
envelope mouth. This heats the air, building pressure until the balloon
inflates all the way and starts to lift off the ground.
The ground crew
members hold the basket down until the launch crew is on board. The
balloon basket is also attached to the ground crew vehicle until the last
minute, so the balloon won't be blown away before it is ready to launch.
When everything is set, the ground crew releases the balloon and the pilot
fires a steady flame from the burner. As the air heats up, the balloon
lifts right off the ground.
Amazingly, this entire process only takes 10 or 15 minutes! The landing
process, combined with deflating and re-packing the balloon envelope,
takes a while longer.
When the pilot is ready to land, he or she discusses possible landing
sites with the ground crew (via an onboard radio). They need to find a
wide open space, where there are no power lines and plenty of room to lay
out the balloon. As soon as the balloon is in the air, the pilot is
constantly looking for suitable landing sites, in case there is an
emergency.
The balloon landing
can be a little rough, but an experienced pilot will bump along the ground
to stop the balloon gradually, minimizing the impact. If the ground crew
has made it to the landing site, they will hold the basket down once it
has landed. If the balloon isn't in a good position, the crew pulls it
along the ground to a better spot.
Click on the images for a high-resolution picture
The ground crew
sets out a ground tarp, to protect the balloon from wear and tear. Then
the pilot opens the parachute valve all the way, so the air can escape out
the top of the balloon. The ground crew grabs a cord attached to the top
of the balloon, and pulls the envelope over onto the tarp.
Once the balloon envelope is down on the ground, the crew begins pushing
the air out. When the balloon is flattened, the crew packs it into a stuff
sack. This whole process is a lot like packing up a giant sleeping bag.
