## Rules to play Hot Air Ballooning

**Weather sources we use**

Many passengers obtain their own weather information from one of the many sites available on the internet we encourage you to take an active role in your flight but remember, we are looking at very different aviation weather information. Many of the reports available to the general public do not contain the information required for a pilot the FAA only recognizes a weather briefing provided by a Flight Service Station, or one of two Direct User Access Terminals (DUAT). We will be happy to discuss our decision with you but, the pilot in command is the final authority on a flight.

**Events**

**Eligibility**

**Hot air balloon physics operation**

If the balloon operator wishes to move the balloon sideways (in a horizontal direction) he must know, ahead of time, the wind direction, which varies with altitude. So he simply raises or lowers the hot air balloon to the altitude corresponding to the wind direction he wants, which is the direction he wants the balloon to go.

The balloon stays inflated because the heated air inside the envelope creates a pressure greater than the surrounding air. However, since the envelope has an opening at the bottom (above the location of the burner), the expanding hot air is allowed to escape, preventing a large pressure differential from developing. This means that the pressure of the heated air inside the balloon ends up being only slightly greater than the cooler surrounding air pressure.

An efficient hot air balloon is one that minimizes the weight of the balloon components, such as the envelope, and on board equipment (such as the burner and propane fuel tanks). This in turn minimizes the required temperature of the air inside the envelope needed to generate sufficient buoyant force to generate lift. Minimizing the required air temperature means that you minimize the burner energy needed, thereby reducing fuel use.

**Hot air balloon physics analysis**

The heated air inside the envelope is at roughly the same pressure as the outside air. With this in mind we can calculate the density of the heated air at a given temperature, using the Ideal gas law, as follows:

P = ?RT

Where:

P is the absolute pressure of the gas, in Pa

? is the density of the gas, in kg/m3

R is the gas constant, in Joules/kg.K

T is the absolute temperature of the gas, in Kelvins (K)

Now,

Normal atmospheric pressure is approximately 101,300 Pa

The gas constant for dry air is 287 Joules/kg.K

The air inside the envelope is typically heated to an average temperature of about 100 degrees Celsius, which is 373 K

Substituting the above three values into the Ideal gas law equation and solving for ? we get ? = 0.946 kg/m3. This is the density of the heated air inside the envelope. Compare this to normal (ambient) air density which is approximately 1.2 kg/m3.

Next, for an average size balloon with an envelope volume of 2800 m3 we wish to determine the net upward buoyant force generated by the envelope.

The net buoyant force is defined here as the difference in density between the surrounding air and the heated air, multiplied by the envelope volume. Thus,

FB,net = (1.2 0.946)x2800 = 711 kg (1565 lb)

This is the net buoyant force pushing upwards on the heated air inside the envelope. The hot air balloon components (such as envelope, gondola, burner, fuel tanks, and passengers) can at most weigh 711 kg in order for the buoyant force to be able to completely lift the hot air balloon off the ground.

**High visibility**

**Flexibility**

**Branding**

**Versatility**

**Excitement buzz**