FREQUENTLY ASKED QUESTIONS ABOUT BALLOONING

1 HOW BIG IS A HOT AIR BALLOON?

Balloons vary in size depending on the number of people they carry the height they are expected to fly at and the air temperature they are designed to fly in. The smallest man carrying balloons called Cloud hoppers, are as small as 10,000cu ft or 300m3 but can only lift a light person for a short period at low altitude in cool conditions.

An average 3-4 person sport balloon is 77,000 cu ft or 2,100 m3 about 20-25m tall and 15-20m diameter. That is about the size of a house standing on its end. It takes about 600 m3 of 70-100oc hot air to lift an average 80kg person, plus fuel for a 1-2hr average flight.

2 HOW DO YOU STEER IT?

Basically you don't steer a balloon at all. Balloons do not move relative to the wind they drift with it. The skill in directing a balloon is using the available winds to take you were you want to go. But if the wind is not going that way that's it. Balloon are all about the journey, not getting from 'A' to 'B' at Mach 2.

Therefore it may seem strange that most balloon competition tasks are about the ability of navigating a balloon to a distant target and dropping a weighted ribbon marker as close as possible. How is this so? Until you see balloons flying at different levels and going in different directions it is hard to see how any one could make a balloon fly in the right direction. Yet on a cool calm morning, when the air is stratified in shallow bands flowing in different directions, flying at various altitudes by using the fine vertical control that a hot air balloon pilot has a balloon can be steered in the desired direction. If the right combination of winds are available. At low level, cool air flows down hillsides and valleys, around hills and even individual trees. At height, air moves in the direction of the general wind pattern. It is possible for two balloons within 50-100ft, 15-30m, in height to pass each other in opposite directions.

Due to the spin of the earth, on the average low level winds in the southern hemisphere blow to the right of those at 2000-3000ft and above, to the left in the northern hemisphere. This is the so-called "Coriolis Effect" renowned for its effects on water going down the plughole. Of cause at low level the above-mentioned effects of hills and valleys, known as topographic effects can have even greater influence. The balloon pilot 'reads' and uses all these effects the steer a course by rising and descending in and out of the various streams of air.

3 HOW DO YOU CONTROL A BALLOON?

Balloons are steered by using various air current. By rising and descending into and out of breezes moving in varying directions.

Hot air balloon pilots control the rise and fall of their balloons by varying the amount of lift. This done primarily by the length and frequency which they operate the air heater or burner. Long, frequent burns will rapidly heat the air in the balloon expanding it, decreasing its density. When the overall density of the balloon, the air it contains and the passengers is less than the same volume of surrounding air that it displaces it floats just as a ship floats. Like a submarine a balloon's buoyancy is adjustable, but unlike most subs a hot air balloon leaks its source of buoyancy, heat, both by heat radiation and conduction and actual slight air leakage. So the burner must be used regularly to maintain level flight. The rate at which heat is lost is affected by many factors. 

  • The larger the difference in temperature between the inside air and the surrounding airthe faster the heat is lost. 
  • The porosity of the balloon fabric. All balloon fabric is coated with a sealer when new. This wears off in time due to the effects of heat, and sunlight so that old balloons become progressively more porous, lose more heated air and consume more fuel and are usually replaced. 
  • The rate at which the balloon passes though the air. Although balloons have no air speed as such and normal experience no wind effects in flight as they move with the air stream. They do pass thought the air vertically and through changes in wind direction, known as wind shears these can speed the cooling of the air in the balloon, spill some of the air out of the balloon envelope and deflect the heat of the burner away from the envelope mouth.

If the burner is not operated for about 20-30 seconds in level flight the air in the balloon envelope will cool sufficiently for the balloon to begin to descend. So slowly at first that it can go unnoticed, but building up to 500-1000ft/min. (9-18kph) depending on the load on board. This is the speed of an express elevator or more to the point that of an emergency parachute, the high surface area and low overall density of an undamaged hot air balloon gives it inherent safety. Such a rate of descent might be injurious but not fatal. Which bring us to the next FAQ.

4 Do you wear parachutes and if not why not?

Most balloon flights take place between a few inches and 500ft off the ground. Parachute jumps are generally considered safe only above 2000ft and we carry our own permanently deployed parachute.

 5 What is the fuel in the tanks and how long does it last?

Hot air balloons burn propane, just like a BBQ. The gas is compressed into a liquid in the tank. There is a pocket of vapour (15%) at the top each tank to allow expansion. The pressure of this vapour pushes liquid propane up a dip tube from the bottom of the tank though a valve at the top of the tank and up the hose to the burner where the pilot releases it through the blast valve. The liquid travels through the vaporising coils of the burner and out the burner jets as vaporised gas.

A typical 10US gal / 38 l tank yields about 34 l of useful propane before the pressure drops and the burner starts sucking vapour which does not produce a useful flame. Depending on the porosity of the balloon envelope and the load being carried this will provide 45-60min flying time. Therefore most hot air balloon flights are 1.5-2hrs, or 3 tanks worth. Long flights are possible carrying more gas, flying solo to save weight and using a bigger balloon. The Australian record for an AX 7 ie a 77,000 cu ft / 2,100 cu m balloon is 8hrs 35min carrying 8 tanks, and that is by no means exceptional. Solo or two person flights of 3-4hrs in an AX 7 are easily achieved with 4 standard tanks 38L tanks.

 6.How much does a balloon cost?

An average size 3-4 passenger balloon costs A$30-35,000 stock standard. Which usually allows for a variety of colours. Most manufacturers will product any colour scheme involving arranging panel of various colours at no extra cost. Diagonal and other fancy cut panels, sign writing, artwork and other custom work cost more and top of the price range are the special shapes which must be individually designed an engineered. For all their weird and wacky appearance they a still man carrying aircraft and must be safe to fly. These can cost A$100,000 or more.

Then there are the running costs, depreciation say $35/hr for an average size private balloon, maintenance say $5/hr, insurance $40/hr, fuel $25/hr and sundries, giving a total of about $120-130/hr at 50hrs/year. Not cheap, but not frightfully expensive. Commercial balloons cost more to operate and the pilot and crew have to earn a living in a very weather dependant occupation so that the average commercial passenger is charged $200+/hr depending on the location and the size of the balloon.

7 What maintenance do you have to do?

Balloons are fairly low maintenance. Treat them well, don't leave them out in the sun, wash any mud off the basket, polish the leather, and annual replacement of the valve seals, trimming and a good soaking of the wickerwork is all that is usually required.

8 What why a wicker basket? Can't you get something lighter and more modern?

Both aluminium and fibre reinforced resin have been used for balloon gondolas but their both dint and scratch too easily. The bottom and sides of a balloon gondola are its landing gear. For a balloon every landing is a 'gear-up' belly landing. Wicker and cane are very tough and even more resilient. Every couple of years the leather or rawhide rubbing strip on the bottom edge of the basket must be replaced. A good soak and some judicious trimming of the odd broken cane a wicker basket can look good for 20yrs of careful use even with the odd hard landing.

9 How fast can you go?

As fast as the wind, which I'll admit used to sound a lot faster than it does today. None the less trying to chase a cross country balloon by road, when the balloon is flying at as little as 10 knots /18kph can involve car speeds up to 100kph. The balloon will pass over rivers and mountains with the same ease and grace that it crosses a flat field.

Normally it is too much trouble to inflate and launch a balloon in anything more that a 5kt breeze so that most pleasure flights are conducted at not much more that walking pace an aerial stroll in the country in 'seven league boots'. 

10 How high can you go?

Most balloon flights take place at low altitudes and not far above the ground, anything from a few feet to 500-1000ft / 150-300m but a normal sport balloon is capable of flying as high as 20,000ft / 6,000m. However for extended flights above 10,000ft the pilot must, breath oxygen so such flights are relatively rare.

11 What regulations did you have to follow? Do you need a licence and what training do you need?

In Australia and most other countries balloons are registered aircraft and must comply with CASA regulations for operations and airworthiness. The balloon receives a daily inspection by the pilot and an annual inspection by authorised maintenance personnel and annual replacement of the gas valve seals. Flight instruments are checked and calibrated every 2 years and gas tanks every 10.

You need a licence either private, issued by the Australian Ballooning Federation, or commercial issued by the Civil Aviation Safety Authority.

An Australian private pilot's licence (balloons) requires 15hrs flight instruction by an approved licensed instructor, solo flights, a flight test and a pass in four written examinations on meteorology (weather), flight rules and procedures, aerostatics (the science of ballooning) and airmanship, and navigation.

A commercial licence requires flight experience as a private pilot, additional training and tests. 

12 What instruments do you carry?

All balloons in Australia carry an Altimeter, to tell how high they are, a Variometer or "rate-of-climb" indicator to measure vertical movement, a compass, an aircraft radio and often a temperature gauge to monitor the temperature at the top of the balloon to prevent over heating.

13. What is it made of?

Most hot air balloons are made of "rip-stop" nylon or polyester proofed with a silicon or polyurethane coating to make them more airtight. These are the same type of fabric used in parachutes and sails.

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