Saturday 21 June At 9.30 in the morning in Praia Grande, in southern Brazil, a tragedy was consumed. A hot air balloon with 21 people on board has precipitated, leading to 8 victims and 13 survivors. The accident seems to have been born from a small rogue inside the basket Which contained the passengers, which brought to an emergency procedure that unfortunately had complications, until it brought to the gash of the ball and the consequent collapse of the whole hot air balloon.
How a hot air balloon works and difficulties in take -off
There hot air balloon It is an aerostatic ball, i.e. an air vehicle that uses low density gases to get up. Specifically, the hot air balloons manage to get up thanks to theUse of hot air inside the ball. This is because the hot air is less dense than the colder one located outside, and for this it moves upwards, it is the famous Archimedes principle. At the entrance of the ball, in the lower part, there is therefore the so -called burner, A cylinder that thanks to the combustion of gas, usually the propane, generates a flame that will heat the air inside the ball and in addition it releases the products of the combustion of the propane that will also go to fill the hot air balloon, which thus manages to get up.
And here we can already do aobservation on the accident: Some witnesses spoke of problems already at the start, because the hot air balloon struggled to get up in the air. Here, on this it must be said that precisely for the cold hot air mechanism that we have just talked about, the lower the external temperature, the easier it will be to make the hot air balloon off. While if it is very hot outside, the difference in temperature between the interior of the ball and the outside is less and therefore the push upwards will be less. It is for this reason that Flights usually take place at dawn or at nightwith a preferable temperature by Massimo 15 degrees. At greater temperatures it can still be flying, but take -off will be more difficult.
At the time of the accident, 9.30 in the morning, in Praia Grande The temperature was around 23 degreestherefore it is not strange that the take -off does not seem to have been immediate.
However, to finish the operation of the flight of a hot air balloon, if you want instead DESCEND, lose altitude, you have to cool the air present inside the hot air balloon. In this way the air in the ball becomes denser and the push upwards is reduced. And how do you do it? Through a relief valve placed at the top of the ball that is opened by the pilot to bring out hot air and thus rebalance the temperature.
Because the presence of a flame is not dangerous: the resistance of the ball
Given the operation of the hot air balloon, probably the most common question is: but it is not dangerous, in general, that a canvas ball be inflated through one flame? Tended not. And this was not the cause of the accident. Modern hot air balloons are composed of synthetic fabrics, such as nylon, equipped with lightness and good mechanical resistance. Consider that the temperatures inside the ball can reach about 120 ° Cwhile the melting temperature of the nylon it is definitely higher, About 220-230 ° C. In addition, the entrance of the ball is very large and the high flame, covered by the ball itself, so It is very difficult for the flame to touch the hot air balloon directly. In addition, in the lowest part, near the burner, there is finally fireflow material, to prevent the ball from taking fire.
The casing is not a unique fabric, but composed of More wedges You sew together and it is made so that even in the presence of glimpses, of an accidental tear, it does not expand. This is why nylon is called “Rip stop”.
So what did the accident caused?
The dynamics of the accident: errors in the procedure in case of fire
The first thing to say is that the weather conditions they were stable And favorable, on the same day other flights had been performed in peace.
According to the testimonies of both the Mongolfiera pilot and the 13 survivors, everything started from a small one rogue inside the Basket of the hot air balloon. What you know is that it may have been caused by the oxidical flame that is used to turn on the burner, but how this has been activated or who has been to use it improperly at the moment is not clear. Another hypothesis is that there was one propane loss from one of the cables that connect the tanks to the light ignition point. Theoretically, the area around the cylinders should be covered by fireproof materialso that the basket is protected from any flames, but we do not know what happened in this case.
Also according to the testimonies, the pilot tried to extinguish the flames with the on -board fire extinguisher, which must always be there, and in the meantime it has made the hot air balloon descend so as to get to the ground.
There procedure in case of fire on boardin fact, it provides precisely: to stop the gas supply by closing the rubunes of the cylinders, turn off the burner And once you arrive on the ground, completely open the valve so as to get all the hot air out and prevent the hot air balloon from getting up again.
Something in this procedure, however, went wrong. Once the hot air balloon arrived on the ground, the pilot gave the order to go down and he also fell, only that not all the passengers had rescued. And here there is a great mistake: The pilot must always be the last to go down. We don’t know why it went down before, but it shouldn’t happen, especially during unexpected events like this. The hot air balloonIndeed, Once on the ground she has returned to climbing. This may be due to multiple factors or errors: first of all, 13 people came down, the weight to be raised has significantly decreased. In theory, however, if the burner was off and the valve correctly open, the hot air balloon should not have returned to get up because it has no longer pushed.
So if she got up, either the pilot did not correctly open the valve or turned off the burner, that is, it did not follow the procedure, or the fire of the basket continued to fill the ball of hot air thus giving it the opportunity to get up. But again, if the valve had been opened, theoretically the lifting was not possible anyway.
A possible hypothesis is that the rope that regulates the valve had been worn out of the stake and for this reason the pilot may not have managed to open it correctly. The fact remains that the pilot made a big mistake: it went down before everyone was safe.
Once returned to altitude, the hot air balloon was so without someone who was able to guide it and with a stake still alive. At that point the Flames from the basket have also reached the other components of the ball we see and collapse. It is also likely that the combustion of the basket brought the air into the ball well above 200 degreesthus going to harm the fabric, which he did not hold up.
