Level flight is achieved when lift equals gravity. For all practical purposes, gravity is constant as far as the balloonist is concerned. The heated air trapped in the balloon envelope overcoming gravity creates buoyancy.

Equilibrium is achieved when lift exactly matches gravity and the balloon neither ascends nor descends, but remains at one altitude. Theoretically, equilibrium aloft is level flight, because the wind may raise or lower the balloon and the ambient air temperature is constantly changing.

Since it is the difference between ambient and envelope temperature that gives the balloon lift, the difference is really what a balloon pilot is interested in knowing, but few balloons have a temperature differential gauge.

In addition to fuel gauges, regulations require all hot air balloons to have an envelope temperature indicator, a rate-of-climb or vertical speed indicator (VSI), and an altimeter. The envelope temperature gauge helps prevent overheating and damage to the fabric. All balloon manufacturers have established maximum envelope temperatures that should not be exceeded. The VSI is a trend indicator showing the balloon's tendency to ascend or descend. A mechanical VSI will lag behind while an electronic VSI is more sensitive. An altimeter is similar. A mechanical altimeter lags behind and a digital altimeter is very sensitive.

Since the air around the balloon is constantly moving and changing temperature, instruments lag. The human eye is the best gauge for determining if a balloon at low altitude is ascending, flying level, or descending.

Theoretically, if a pilot were to hold a hot air balloon at a constant temperature, the balloon would float at a constant altitude. However, there is no practical way to hold the envelope air temperature constant. When the first modern hot air balloons were flown, pilots used a metering valve to adjust precisely a constant flame, hoping to hold the balloon in level flight. Anyone who has tried to fly that way has found the technique is noisy, fuel inefficient, damaging to the burners, and nearly impossible. Most modern hot air balloons are flown with a blast valve using unregulated tank pressure.

For every altitude there is an equilibrium temperature. If a pilot is flying at 500 feet mean sea level (MSL) and wants to climb to 1,000 feet MSL, the balloon temperature must be increased. This is not only to attain equilibrium at the new (higher) altitude, but some excess temperature must also be created to overcome inertia and get the balloon moving. Newton's law states, "A body at rest tends to stay at rest, and a body in motion tends to stay in motion."

A pilot flies level with a series of standard burns. Ideally, if the burns were of identical length and perfectly spaced, the balloon would hold a nearly constant altitude. The word nearly is used because the ambient air temperature is always changing. Each time a pilot burns, the balloon will tend to climb, but the air in the envelope is always trying to cool and the balloon will tend to descend. If the subsequent burns are perfectly timed, the balloon will fly in a series of very shallow sine waves.

An interesting experiment is to use the second hand of a wristwatch to establish a usable level flight pattern. Establish a standard burn and count how many burns are necessary to hold the balloon relatively level for 5 minutes. Assume you make five burns in 5 minutes and the balloon stays pretty much at 1,500 feet AGL. That means if you make a standard burn every 60 seconds, the balloon will fly level. Now you have a basis for controlling the balloon.

Of course, any variable will change the balloon flight. A heavier basket load, higher ambient temperature, or cloudy day, will all require more fuel (by shortening the interval between burns) to maintain level flight.

By experimenting, you can establish standards that can be used as a basis for all flights. On a hotter day, or with a heavier load, you could make the interval 55 seconds. A standard baseline to work from will then have been established.

With practice and using the second hand of a wristwatch, a new pilot can fly almost level. The exercise of trying to learn the pattern of burns (each day and hour is different) is an interesting training exercise, but not a practical real-life technique. The ability to hold a hot air balloon at a given altitude for any length of time is a skill that comes only with serious practice.

Level flight is probably the most important of all flight maneuvers. Nearly all other flight maneuvers are based on level flight. Level flight is very important to the student pilot aspiring to pass the practical test. Maintaining level flight is one of the few balloon maneuvers for which pass/fail tolerances have been established.

Unfortunately, most pilots do not spend enough time practicing level flight. If, during the practical test, you have a choice of altitudes, pick a lower, rather than higher altitude, to perform level flight. There are more visual references to assist in maintaining level flight when you are closer to the ground. Of course, you do not want to fly below minimum safe altitudes, and you should always be alert for powerlines along your flightpath.

Level flight is the basis of most other flight maneuvers. Evenly spaced, standard burns can produce smooth, relaxing level flight. The ability to fly straight and level comes with experience and practice.

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