The fan (in the background) inflates the balloon until it is safe to fire the burners

Hot air balloons are aircraft that gain their lift by heating a large contained envelope of air above ambient temperature. The envelope containing the warmer, less dense air rises and is used to lift the payload of basket, fuel tanks and passengers.

The air in a typical balloon may be heated approximately 90 to 100 degrees C above ambient temperature. The balloon will then float at whatever altitude the mass of cold air it displaces equals the combined mass of the warmer contained air, balloon system and payload.

A balloon has no means of propulsion. Except when ascending or descending it is stationary in the air and its groundspeed is exactly equal to windspeed. Airspeed is zero and there is no aerodynamic lift. This results in the smoothest ride possible in any form of aircraft. There is absolutely no vibration and no matter what the speed is over the ground, there is no wind noise in the basket.

Level changes are achieved by more heating to climb. Descent may be initiated by dumping hot air from a valve in the top of the envelope or simply letting the air cool down. It is only whilst climbing or descending that passengers may experience a little air speed in the basket as the balloon passes through temperature inversions or wind shears.

Perfect time for launch! Right on sunrise

A hot air balloon comprises of several components.

The envelope itself is a VH registered aircraft. It may vary in volume from 21,000 cubic feet (one person) to 400,000 cubic feet (20 persons).

The envelope is attached to the basket via stainless steel or kevlar flying wires. The baskets are still woven wicker as this provides enormous strength and passenger protection, but is flexible so does not break on the occasional bumpy landing.

Stainless steel propane fuel cylinders are carried in the basket to provide fuel for the burners which are suspended between the basket and envelope. In winter, the fuel cylinders may have nitrogen added to maintain burner pressure.

Instrumentation consists of altimeter, variometer, and envelope temperature indicator. Most balloons operating in Australia are VHF radio equipped and also carry a transponder in accordance with standard airspace requirements.

As previously discussed balloons have zero airspeed therefore they cannot turn to avoid obstacles or other aircraft. They can, however manoeuver vertically provided there is sufficient time and advance knowledge of an obstacle.

Most balloons operating in Australia have maximum legal climb rates of 1000 feet a minute. Descent rates may be similar but pilots will typically climb and descend at a maximum of 600 feet a minute. Whilst these quite respectable rates can easily be maintained, there is a little time lag between initiating a climb and it actually happening.

A reasonably large balloon will contain 10 tonnes of hot air. This added to a payload of over a tonne gives a quite significant aircraft mass and despite the enormous energy output of the propane burners, it may take up to 30 seconds to get this mass moving rapidly in a different vertical direction.

The simple answer is that a pilot should not be surprised to see a balloon almost anywhere although geographic and regulatory factors result in the favouring of certain locations.

The regulations provide for commercial licences and private certificates. Amongst other things, these restrict the access of private operators to certain classes of airspace. From a safety perspective, the actual regulations are not worth detailing for three reasons. Firstly, the entire regulatory framework is under review and whilst knowing CASA, change is unlikely overnight, it will occur. Secondly, the number of concessions granted to individual pilots against the regulations makes them an unreliable guide. Finally, it is irrelevant to the pilot whose windscreen has just been overwhelmed with the view of a 30 metre tall balloon whether the balloon is being flown commercially or privately!

For safety purposes, a balloon should be expected to be flying legally in any class of airspace. The two most likely areas other airspace users will encounter balloons are as follows:

Firstly, over or around the capital cities, particularly Canberra, Brisbane, Melbourne and the Western suburbs of Sydney. Separation will be provided if the balloons are operating in controlled airspace over the cities but particular attention should be paid by pilots operating OCTA below the controlled airspace steps surrounding the terminal area.

Secondly, around smaller inland country towns within a few hundred kilometres of the capital cities. Towns with a reasonable surrounding road network will be favoured as this makes it easier for retrieve vehicles to collect the balloon and pilot from its inevitable outlanding. Coastal towns are less appealing because flying is restricted in the case of an offshore breeze, as discovered the wet way by two Gold Coast pilots in the last ten years. Coastal terrain is also generally less balloon friendly, with more hills and forests than inland areas. Balloons will regularly operate up to 5000ft but they should be expected up to 10,000ft. They will rarely fly above this level because of the inconvenience of arranging oxygen and special approvals.

In fact, balloonists delight in low level flight and may spend entire flights brushing through the tops of trees. With this low level flight ability, air traffic control regularly maintains vertical separation from even quite low level aircraft on approach to land. ATC generally have a good knowledge of a balloon’s capabilities, although I will never forget the occasion I was asked to hold position over the Lake in Canberra. I suggested throwing out an anchor but received no response.

Whilst balloonists rely on hot air for lift, they hate convective conditions. When a balloon is flying in stable air the pilot determines the height by use of the burner. However, if caught in thermals the balloon will ascend whether the pilot wants it to or not. Even worse, is the unplanned descent after being ejected from the top of a thermal! This is not a comforting experience and may not be solved simply by flying out of the thermal as remember, the balloon moves only with the air.

It should also be noted that the surface wind speed is the landing speed and balloons always make ‘wheels up’ landings. For these reasons, balloon pilots avoid the windy thermic parts of the day and should therefore be expected mostly in the mornings or evenings. Exceptions do occur to this especially on cold, stable or overcast winter days where it may be safe to fly all day.

Balloons are only allowed to fly VFR, and the relevant VMC conditions are similar to other air space uses. The most significant variation is that below 500 feet only 100 metres of visibility is required. This allows take off in fog, which is not a problem given a balloon’s low speed and total inability to pitch or roll – an artificial horizon is certainly irrelevant in a balloon. Any other aircraft that close to the ground in such limited visibility probably has more immediate problems than running into a balloon!

Balloons may also operate in night VMC. When doing so they carry a red light suspended below the basket. This however, is an insignificant beacon compared to seeing the entire 30 metre tall balloon light up like a globe when the burners are activated. Remember however it will go dark again as soon as the burners are turned off. A balloon pilot will typically operate the burners for 2 to 5 seconds at 20 to 30 second intervals.

Balloons are big and brightly coloured and always attract attention. Many of their pilots similarly enjoy the attention and will nearly always be pleased to have other aircraft circle them. If you are going to do so maintain standard separation, but don’t be fooled by the close proximity of balloons to each other as they have zero horizontal separation requirements. Balloons may initiate fast climbs and descents so the pilot will be more comfortable if you fly around rather than above or below. This is absolutely essential with helicopters as nothing is more daunting than looking straight down into the spinning blades, knowing the pilot cannot see you.

In conclusion, balloons are easy to see and therefore relatively easily avoided. Like a sailing boat, they also have right of way over all other aircraft. The only exception to this is that balloons operating close to airfields must give way to aircraft landing or taking off.

The best way to really appreciate how a balloon operates is obviously to take a ride in one. I can guarantee that almost every fixed wing pilot will be amazed at the complexity and subtlety of air currents they will discover in a balloon. I am always surprised as to how many power pilots are nervous (or perhaps simply uncertain) about the concept of flying in a balloon but I’m certain you would all enjoy your first totally G free flight.