How Do Hot Air Balloons Steer? The Trick Pilots Use With No Steering Wheel

Look inside the basket of a hot air balloon and you will notice what is missing. There is no steering wheel, no rudder, no engine pushing it forwards and no wings to bank. A pilot has a burner to go up and a vent to go down, and that is about it. Yet balloon pilots regularly land in a chosen field, follow a route over a valley, and even win competitions by dropping a marker close to a target.

So can you steer a hot air balloon? Directly, no. Indirectly, yes, and the method is one of the cleverest ideas in flying. The pilot does not change the balloon's direction at all. They change which wind is carrying it.

A hot air balloon flies for the same reason a bubble rises in a pan of water. Hot air is lighter than the same amount of cooler air around it, so a big bag of hot air floats upwards and lifts the basket with it. The idea is old: on 21 November 1783, Jean-François Pilâtre de Rozier and the Marquis d'Arlandes crossed Paris in a Montgolfier balloon, the first free flight with people on board. It lasted 20 to 25 minutes and covered roughly 9 km.

Modern balloons run on propane. Firing the burner heats the air in the envelope, which is the name for the fabric balloon, and the balloon climbs. Stop burning and the air slowly cools, so the balloon starts to sink. To come down faster, the pilot pulls a line that opens a vent at the top of the envelope and lets hot air escape.

Staying level takes constant small corrections. The FAA's Balloon Flying Handbook says an average balloon needs a burn of about four seconds every 25 to 40 seconds just to hold its height, and the rhythm changes with the load and the air temperature.

From the ground, it is easy to think of the wind as one thing. In reality, the air above you is often stacked in layers, and each can move at its own speed and in its own direction. Friction with the ground slows the lowest air, and higher up the wind usually gets stronger and turns. In the Northern Hemisphere it tends to shift to the right as you climb. Hills, valleys and the sun warming the land add their own twists.

Here is a simple way to picture it. Imagine a tall building where every floor has a moving walkway, and each walkway runs in a different direction. You cannot step off and walk. All you can do is ride the lift. If you want to go east, you take the lift to the floor whose walkway runs east, and you stay on until you need to change.

That is balloon steering. The burner and the vent are the lift, and the wind layers are the walkways. Sometimes a change of just a few hundred feet is enough to put the balloon on a completely different course.

The hard part is that wind cannot be seen. Before launch, pilots check the forecast for winds at different heights, then test it for themselves. A common method is to release a small balloon, known as a pibal, short for pilot balloon, and watch which way it goes as it climbs.

Once they are flying, pilots look for clues everywhere. Other balloons are the best one, because each is a giant wind marker showing what is happening at its height. Smoke from a chimney, flags, and moving trees all help near the ground.

Even so, the layers do not always offer the direction a pilot wants. If no wind is blowing towards the planned landing field, no amount of skill will get the balloon there. That is why most balloon flights have a chase crew following by road, ready to meet the balloon wherever it comes down.

The best example of all this is in New Mexico. On many autumn mornings in Albuquerque, the valley develops a pattern called the Albuquerque Box. Cool air drains down from the surrounding mountains overnight, and the low wind can end up blowing one way while the wind a few hundred feet above it blows the opposite way.

For pilots, that is close to a gift. They can launch, drift along in the low layer, climb into the upper layer to travel back, then sink again, sometimes finishing near where they started. It is a big part of why the city's International Balloon Fiesta has become so famous.

It is not guaranteed, though. Once the sun warms the ground, the pattern breaks up, and one study cited by forecasters found it appears only about 30 percent of the time in early October. Pilots still have to read each morning as it comes.

If reading the wind is the first skill, patience is the second. A balloon responds slowly. The burner sits well below the top of a very large envelope, and that air takes time to heat. By some pilots' accounts, it can be 15 to 30 seconds before the balloon responds to a burn. The EAA makes the same point about clearing obstacles: firing the burner does not give you height straight away.

The delay works in both directions. A balloon that is climbing will keep climbing for a while after the burner goes quiet, and one that is sinking will keep sinking after the burn starts. A pilot aiming for a certain layer has to begin slowing the climb well before reaching it, or the balloon will sail straight through.

We built Loftwind, a free balloon racing game that runs in the browser, around this one idea. There is no steering at all. You hold to fire the burner and rise, and let go so that the air cools and you sink. Every band of sky has its own wind, some blowing forwards and some backwards, so you move by climbing or sinking into the one you need.

The delay is there too. Your balloon keeps rising for a little while after you let go, and keeps sinking for a little while after you start burning again. Starting early is the main skill in the game, just as it is in a real basket.

You race three to five rival balloons through numbered ring gates, over 30 courses in five chapters. Miss a ring and nothing is lost but time: you find a band blowing backwards, drift back and try again. Your best run on each course also flies beside you as a ghost, so you can see where you gained or lost time.