Everything you need to know about how hot air balloons work

On a quiet, lazy October morning, the sun rose over the Sandias, gradually stealing away the shadows covering Albuquerque. A dozen or so hot air balloons, some 1,600 feet above ground level, scattered a sky that soon would fill with hundreds of more balloons for the 52nd Albuquerque International Balloon Fiesta.

The silence was occasionally interrupted by the loud whoosh of burners keeping the hot air balloons afloat, which set off dogs barking on the ground in response to the high-pitched propane burner noises. The dozen or so passengers on one particular balloon chattered quietly, wondering out loud how the aircraft invented three centuries ago actually work.

Pilot Troy Bradley, calmly setting off the burners to keep his balloon and its passengers in the sky, patiently answered many of the same questions: How does the balloon fly? How do the burners work? Will we land where we started?

Bradley, chief pilot for Albuquerque-based Rainbow Ryders Hot Air Balloon Co., has known the answer to these questions since he was a kid. Generations in his family learned to fly at a young age, and he has been flying for over 40 years now.

He flew his own balloon and oversaw the dozen other balloons flying on Thursday in Albuquerque. These were some of the final flights before thousands flocked to Albuquerque to attend the Balloon Fiesta, which began over the weekend and continues through Sunday.

The Journal took a spot in the wicker basket held by the huge balloon, along with 13 passengers and Bradley, to get a look at the mechanics of hot air ballooning up close.

How it flies

Hot air balloons are classified as lighter-than-air aircraft, Bradley said in an interview with the Journal the day before the flight.

He said balloonists operate on the Archimedes principle of buoyancy, which is that a body that’s immersed in a fluid is buoyed by the force equal to its weight of that displaced fluid. The force is the fluid balloonists displace, Bradley said.

In simpler terms, the balloonists are heating up the air to float. Bradley said hot air is less dense than cold air and is therefore lighter.

“And hot and cold is all relative,” he said. “So, you know, if it’s 50 degrees out, and we were heating the balloon to say, 175 degrees — so it is a hot air balloon. But if it was, you know, 80 degrees out, we’d have to heat it to a greater number, so say it’d be 250 degrees that we’d be heating it up to.”

He compared it to how a boat stays afloat on water.

“It’s exactly the same,” he said. “We’re floating on a cushion of air, basically.”

Rainbow Ryders’ balloons carry 80 gallons of fuel, which Bradley had on board dispersed among multiple tanks. Bradley said that’s enough to fly for 90 minutes to two hours, more than the typical flight time of about an hour.

Bradley said pilots really develop “a feel” over time for how much heat to apply during flights, something he said is the hardest part to teach new balloonists.

Controlling the balloon

Controlling the balloon in the air is partially up to Mother Nature. Bradley said balloonists’ control is strictly vertical — moving the balloon up and down. Horizontally, the balloon goes where the wind takes it.

“The balloons are very, very controllable, and so there’s no reason to think that we’re not able to do something instantly,” he said. “We are steering; it’s just with Mother Nature as kind of our steering wheel.”

The amount of heat balloonists apply during a flight with their burners dictates how high they’ll go.

Burners continue going intermittently throughout flights to keep stable heights.

“Just like if you have a cup of coffee sitting on your table, it’s going to continually cool down,” Bradley said.

Pilots can also control flaps in the balloon fabric, opening vents to rotate the balloon clockwise or counterclockwise.

“It doesn’t steer us any way, but it does rotate us so there’s not a bad seat in the house,” Bradley told his passengers on Thursday.

He said there are different winds at different altitudes, and Albuquerque is well known for its “box winds.”

He explained that all valleys can get box winds. Santa Fe, which sits 1,000 feet higher than Albuquerque, could have a cooler air mass flow south into Albuquerque’s valley while upper winds move opposite to the north.

That causes balloons to fly in a box-like pattern.

Bradley said getting to a landing site and landing the balloon is where piloting really comes in and most of the action happens.

He constantly checked below his balloon on Thursday to make sure no other hot air balloons were in his landing path. He said it’s OK if the actual fabric of the balloons touch — that’s called a kiss — but it’s dangerous when baskets bump.

“You want to have it in a controlled descent and not make it too rough on the passengers. You don’t want to have a lot of speed going horizontally and come down really hard vertically, (which can) also can be real, real dangerous for passengers,” he said. “So we’re very careful about how we make those approaches.”

All hot air balloon pilots are licensed by the Federal Aviation Administration.

The conditions

Bradley said the weather conditions allow balloonists to fly in Albuquerque 90% of the time.

When should pilots avoid flying?

Bradley said balloonists like to see surface winds at less than 10 mph so landings are smooth. The speed of the wind at higher altitudes actually doesn’t matter as much because the balloon is moving with the wind, so passengers don’t feel it, he explained.

He said other unstable weather conditions like thunderstorms also make flying unsafe.

The most stable time of day is the morning, he said, which is why the balloonists ascend so early.

The size of balloons also affects operations. Larger balloons require more attention because pilots are heating up a larger volume of air, Bradley said, and the balloons respond slower.

The commercial hot air balloon he flew on Thursday had a volume of 315,000 cubic feet and could hold up to 16 people. He said the smaller, one-man balloons — called cloud hoppers — have much smaller volumes at 35,000 cubic feet.

Heat can also affect the flow of things.

When it’s hotter out, as is the case so far for this year’s Balloon Fiesta compared to most other years, Bradley said balloons are less responsive and can carry less weight for the duration of an average flight. But, he said, operations really aren’t impacted that much.

After Thursday’s flight, the passengers who came in from all over the country for the event toasted with champagne, as is tradition for new flyers.

“May the winds welcome you with softness. May the sun bless you with its warm hands. May you fly so high and so well that God joins you in laughter and sets you gently back into the loving arms of Mother Earth,” Bradley recited, a tradition known after flights as the “balloonist prayer.”