Lighter than air
I spend part of each summer helping on my relatives’ farm in Battle Creek, Michigan (for another story from Battle Creek, see my blog post). A few years ago, I was lying on a big round hay bale in the early June sun after doing morning chores. It was a brilliantly bright day, promising to be a scorcher even though summer was young.
As I lay looking up through squinted eyes at cotton candy clouds, I heard a dull roar to the south. I stood up on my bale to see over the trees surrounding the hay field and spotted a hot air balloon from the annual races floating overhead. I took off after it as it passed by to the west. The tri-colored balloon dipped below the tree line past our fields and landed in a neighbors’ back forty.
It has become commonplace for balloons to touch down in random open fields and large front yards and gardens while racing or sightseeing during Battle Creek’s annual, weeklong Field of Flight Air Show & Balloon Festival. After landing, pilots will collapse their balloons and radio their ground crew to come pick them up.
On average, a hot air balloon burns fifteen gallons of propane per hour (burn rate can be adjusted). The hot exhaust, upwards of 200 degrees Fahrenheit, fills the envelope and produces lift. For a quick review, the density of air decreases as its temperature increases, causing the air to rise above ambient air of lower temperature. To give you an idea of the average envelope size, 2015 Balloon Festival Champion Joe Zvada arrived at the 2016 festival with a 70,000 cubic foot balloon.
While burning preheated propane gas is more fuel efficient, many balloon burners have a second valve that bypasses the heating coils. This allows pilots to burn liquid propane, which creates much less noise and is useful for flying over livestock.
The parachute valve controls the rate of hot air exiting the envelope and is controlled by use of the valve cord. Allowing hot air to escape will decrease the balloon’s altitude. The balloon has no mechanical method for steering and relies on the direction of the winds. Currents often have different headings at different altitudes, so pilots can climb or descend to change course.
Just like with flying airplanes, you have to get a pilot’s license to be a hot air balloon pilot. Some requirements include ten or more hours of flight training, one solo flight and one controlled ascent to 2,000 feet above takeoff altitude. Balloons fly VFR, i.e. no flying through clouds. In addition, flying at night is not recommended and often not insured. A good balloon pilot should have an intensive understanding of wind patterns and weather forecasts and be able to make accurate course predictions.