So we have been checking the weather forecast and everything appears to be in our favour for a flight in the balloon. But what are we actually looking for in the forecast to be able to fly?
Hot air balloons fly to Visual Metrological Conditions (VMC). That is below 3000ft and outside of controlled airspace we should be able to see a minimum of 1500 metres, be clear of cloud and visual with the ground. You won't believe how many hours we lose every year waiting for the fog to clear!
The area that I fly from in Wales is part of the RAF low flying training system so it's highly important that a Tornado at 500ft and 400 knots has the visibility to see me. I don't think either of us would be happy with the balloon wrapped around his tail.
The surface wind needs to be below a maximum of 15 knots, ideally in the 4-8 knots range. Inflating the balloon with higher wind speeds generally turns in to a fight between the envelope - which is blown from side to side, wanting to fly off on its own - and the ground crew trying to hold on to it.
The direction of the wind also plays a big part in determining your take off site and to the flight planning of the direction you're going to travel. Here in Wales I'm close to a military range and the MOD wouldn't want me flying over it and especially not landing on it. So it's a case of finding a site where the track will take me away from it or not flying at all.
Obviously we're not going to be flying in the rain so the risk of rain is taken in to account also.
Temperature plays a part too. During the summer months we will generally fly in the first hour of light from dawn to the last hour of light to sunset. This is because the sun will heat up the air causing thermal activity creating unstable air that will artificially keep the balloon airborne. The air inside the envelope will not naturally cool so control of the flight can sometimes be taken out of the pilots hands. During the colder winter months this is not so much of a problem and on those cold crispy days we are able to fly at any time of our choosing if the conditions are right.
With the weather checked and NOTAM's checked to ensure there are no airspace restrictions were ready to set up.
On arrival at the launch site a check of the surface wind direction is taken, this will determine which direction the basket and envelope are laid out. The envelope is always laid out downwind of the basket this is to prevent the envelope being blown on to the burners during inflation.
Next step is to get the basket off the trailer and upright to carry out a burner and fuel check. The volume of the envelope will depend on how many burners you have. A one man hopper balloon will have a single burner increasing up to three or four burners for the large commercial passenger balloons.
The balloon I fly has an envelope capacity of 90,000 cu.ft, known as a "90", and I use a two burner set up. Each burner can be used in two ways with a main power jet that looks like a bunsen burner flame and then a whisper burn that looks like a flame from a match. The whisper burn is not quite as powerful but as its name suggests is much quieter so is used for example when over flying livestock so as not to scare them. The two burners can be used independently or a cross flow valve opened so that both are used at the same time for twice the power and heat. Hot air balloons are powered by LPG gas, the same fuel that is used for automotive gas conversions.
With the burner checks completed satisfactorily the basket goes over on to its side and the envelope can be attached. The envelope is attached by wire (gore) to karabiners on the burner frame. The amount of wires attaching it depends on the size of the envelope and the manufacturer. My 90 is an eight gore envelope, but the big passenger carriers like a 600 would have a 32 gore envelope; that's a lot of wires to get in the right order! With everything connected we pull the bag containing the envelope away from the basket gradually easing out the envelope in a long line.
The ground crew will then pull the envelope out to the sides as much as possible to aid with the cold inflation. The control lines for the envelope are attached to the basket. All balloons have a rip line which pulls the parachute at the top of the envelope down for deflation, some have turning vents that allow the balloon to turn on its axis and these lines need to be connected too. A quick release line is attached to the burner frame and to a ground vehicle. This stops an uncommanded take off and also assists with stability if it's breezy.
With the ground line attached, a ground crew member will stand either side of the mouth of the envelope and the fan is started to blow cold air in to the envelope. At the top of the envelope is a big hole where the parachute needs to be fitted. The parachute can best be described as a "bath plug" that seals the hot air in to the envelope. A vent line can partially pull the parachute down and then allow it to reseal in flight to release hot air to control the balloon.
On landing the rip line is pulled and this will pull the parachute completely away, releasing all the hot air so the envelope deflates. On cold inflation the parachute is held in place by velcro strips. Once the balloon is upright and hot the vent line is pulled to release the velcro and the parachute is kept in place by hot air pressure. With the parachute in place a crew member will take the crown line to control the balloon as it inflates.
The crown line is used to ensure a safe and slow rise of the envelope as it's being filled with hot air; on a breezy day this can be quite a challenge as the envelope moves around. Once the envelope is cold inflated the pilot will walk inside it to check that the control lines are free of snags and that the pulleys they pass through are clear along with checks on the envelope.
So with the envelope full of cold air, the crew in place and with their orders from the pilot, it's time to light the burners. With bursts of heat from the burners directed in to the mouth you can see the heat ripple along the envelope; hot air rises so the crown soon starts to rise. This is where the crew member on the crown line comes in. Their job is to hold the crown down until the rest of the envelope is hot - not as easy as it sounds -think giant tug of war that you will always lose! As the balloon fills with heat the crown line is brought in towards the basket allowing the balloon to stand up. Too quick and the envelope will pinch in at the mouth where it's not full of hot air, resulting in some very careful use of the burner in a much reduced opening.
With the balloon on its feet and crown line attached it's time to get weight - sorry, passengers - in the basket. At this stage it's important to have weight in the basket as the envelope wants to fly and will lift the basket off the ground. The size of the balloon dictates the amount of passengers and without the passengers there is not enough weight in the basket to fly in a fully controlled manner.
We get the envelope nice and hot with the burners, pull the vent line to release the velcro holding the parachute in place and allow it to re seal under air pressure. We are now ready to take off.
More use of the burner and the balloon is nearly buoyant, the quick release is armed, and a bit more heat and the balloon feels buoyant, just lifting from the ground. Checks to make sure it isn't false lift and we are ready to go! Burner on and a pull on the quick release and we are airborne.
Now we're airborne just how do you fly a balloon? The basics are more heat to go up and less heat to go down. To fly level flight it's a balancing act of feeling when the envelope is just starting to cool. When flying you will see the pilot using the burner regularly to keep the envelope at the same temperature. Too late on the burner or too much on the burner and you'll feel like you're on a roller coaster going up and down.
Two questions were always asked when we fly are "how do you steer it?" And "where will it land?" Which can both be answered by, we have no steering that's all down to the wind and the skill of the pilot! Whilst we know a general wind direction from the forecast the wind actually blows in varying directions at different levels.
Where we fly in Wales we also have valley winds so you can descend in to a valley and find yourself turning 90 degrees to follow the valley. In certain conditions you can experience what's known as an inversion layer. This is where you can be flying at say 2000ft heading north, descend down to 500ft and be travelling south. When I'm crewing for our commercial balloons these are the conditions I like, instead of chasing around the countryside after it, I can stay put at the launch site and wait for the balloon to come back to me. Alas it doesn't happen very often!
I'm often asked what it's like to fly in a balloon, the best description I can give is to imagine flying on a magic carpet. You're floating along on the breeze there is no sense of movement as you fly; the basket is a very steady platform. Apart from the burner noise it's a silent way of flying and it's amazing how much you can hear; animals, people talking and it's a friendly way to fly - most people on the ground will give you a wave. It also gives you a totally different perspective flying over an area you know well from the ground.
Balloons are extremely controllable and with the right conditions and surroundings low level flying can be fun. Skimming over a field at just a few feet above the ground is a great experience or flying at treetop height saying hello to the birds or how about walking on water when "landing" on a lake or river...
So we have reached our fuel limit and it's time to look for a landing site. As with flying we know to avoid landing on sensitive areas, generally notified areas with livestock or those people that don't like balloons. We're looking for a good field or area without crops or livestock and no overhead cables and hopefully good access for the ground crew to collect us. If the wind is calm then we can generally land vertically like a helicopter. If there is a breeze we land like an aircraft, depending on how much of a breeze will be a factor on the size of the landing area. A light breeze and we will land within a short distance. A higher wind speed and the basket can be dragged along for some distance so you need to ensure there is enough room to land and recover safely.
With a landing site identified we begin our descent, short sharp bursts on the burner arrest our descent speed. We're aiming to round out the descent just above the ground ready for landing.
Once we are committed to land and just above the ground the gas for the burners is cut off. This is to prevent unintentional burner use - especially if the basket tips on landing. If we're landing with a breeze then we can pull the rip line to empty the envelope knowing that the breeze will stop it collapsing on to the burners. If it's a calm landing then a crew member will take the crown line and as the rip line is pulled they will run and pull the envelope over to avoid it collapsing. Then it's left for the ground crew to assist in gathering up the envelope, the full body workout of putting it back in its storage bag and then getting everything back on the trailer for the trip home.
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