HOW DO YOU FLY A HOT AIR BALLOON?
TAKEOFF AND FLY!
With the balloon upright, it's time for one last set of preflight checks before you launch. First, you check the burner once again for any propane leaks and adjust the pilot light. If you have a second burner, you light it now if you haven't already. You could do this the conservative way by lighting the pilot light with the piezo or with the sparker you carry with you, but if you have two burners its a lot more fun to open the pilot light and then pull down on both blast valves and let the first burner light the second "with one hell of a roar"! You check your control lines for free and easy movement, but instead of leading to ailerons or elevators it's a vent line leading to the side vent or the parachute top. If you have a spring-top Aerostar, you check to make sure your red ripline is free and accessible, but you DO NOT pull it unless you want to try the inflation sequence all over again. Other important items... Champagne on board? Check. Radio communications check between balloon and chase vehicle. Check. Canvas bag on board for packing up the balloon envelope (so you have something to keep you busy if your chase crew doesn't find you immediately!). Check. And certainly last but not least, are the keys to the chase vehicle in it's ignition or are they in your pocket? Check!
Like the airplane pilot, the aeronaut has to be concerned with weight and density altitude. Balance pretty much takes care of itself in a balloon, unless you have a big basket and one very big passenger standing at one end of it. But most balloonists rarely consult their owner's manuals for weight figures each time they fly. (Come to think of it, there aren't many fixed wing pilots that do either!) With all the variables including temperature, humidity, and, as the balloon ages, porosity, it's easier and more accurate just to do a good "weigh-off".
A balloon's primary load limitation is the temperature at the top. A balloon has a yellow arc and a redline, but they're related to top temperature. Flying in the yellow too often and too long can weaken the fabric and shorten it's life due to increased porosity and decreased fabric strength. Fly in the red, and you risk catastrophic failure (the top melting out, which can bring you out of the sky almost as fast as the wing coming off an airplane).
To determine if you can carry one passenger or two on a warm summer afternoon, you have your maximum number of passengers (usually two plus the pilot in a typical medium AX-7 balloon) get in the basket. With your ground crew on the tether ropes to keep you over your takeoff point, you fire the burner until the balloon starts to ascend, and you check the temperature. With a temperature of 250 degrees F as the bottom of an Aerostar's yellow arc, most pilots will want a maximum weigh-off temperature of no more than 220 degrees to allow margin for maneuvering climbs out of wind shears. Cautious, conservative, non-commercial balloon owners may even opt for an envelope-saving 50 degree margin. Being extra cautious, however, may mean having to be cold-hearted enough to tell one of you bright-eyed enthusiastic passengers that they have to get out of the basket and fly another day. Not an easy task!
After making sure you are well-clear of powerlines (at least 100 feet in the direction of any powerlines for each 1 mph of surface wind), takeoffs are usually straightforward. Since your visibility up is nil, you have your crew check to make sure that no other balloons are passing over you, and then you fire your burner and lift off leisurely. But there are special cases where you have to contend with "false lift", a phenomenon similar in it's effect on the balloon to trying to take off in an overloaded airplane in ground effect. If you are in a sheltered area and a wind is blowing above nearby treetops creating a wind shear, the curved top of the balloon can act as an airfoil and pull the balloon up to just above treetop level. Without enough heat to go higher, the balloon may clear the takeoff field and like an airplane taking off in ground effect, climb no further or even begin settling back toward the ground. Into the trees! What's the answer? In an airplane, you build up extra airspeed if runway length allows. In a balloon, you have your chase crew hold the balloon down until you have enough heat for extra buoyancy, and then you signal them to let go and you pop right up through the shear layer well clear of the trees.
FLOATING ON AIR
Once you are up in the air, you quickly learn that a balloon takes 30 seconds or more to respond to any control inputs, which of course are limited to adding heat with the burner or by letting out heat with the vent. Levelling off precisely at a given altitude requires backing off your takeoff climb rate at least 500 feet before the desired altitude, and using either short burns or more widely spaced long burns to "hit your altitude". And even then the low-time balloon pilot if likely to overshoot by 200 feet or more!
Straight-and-level flight requires developing a rhythm, a sense of timing of when and how often and how long to fire the burner. For the student pilot, it also means paying attention and not getting sidetracked by the beauty of the earth below and other balloons nearby. An instructor's kick in the shins or a poke in the ribs will quickly break your reverie, of course!
You don't sit in the left-front seat in a balloon. You stand... in the front of the basket. Of course, there is no defined front. You could hang a little sign on one end saying "front", but it won't do you any good. Front is the side of the basket that's getting there first, and the balloon may spin slowly in ascents or descents, requiring you to constantly be changing ends of the basket to stay "in front".
You are out in the open air and one with nature, your reverie broken only by your intermittent burner blasts. A leisurely hour flight of only five or six miles can be an incredibly beautiful experience as you drift along just above and sometimes in the treetops. You see rabbits and geese and foxes in the woods... foliage colors are accentuated as you see them from above at a slow enough pace to appreciate them. Over ponds you look down and see the reflection of your beautiful balloon, getting larger as you descend to try a water landing!
SHARING THE SKY
Balloonists don't like to fly alone. Maybe it's because balloonists are forced to be more sociable than most fixed-wing pilots. If they weren't, their chase crews might just drive to breakfast and leave them stranded! Maybe it's because balloons are beautiful, mystical, fascinating... and you never get to see your own! But there's a practical reason, too. The only lateral control you have over your balloon's flight path is by catching wind shifts as the wind changes at different altitudes. If more balloons are up with you, you can compare their ground tracks and altitudes with yours. Of course, you can always try different altitudes yourself, but that wastes time and fuel and turns a beautiful drifting flight into a bit of a chore. Airspeed and distance also varies with altitude. Generally, the higher you go, the faster you go. Low flying is generally leisurely, hopefully, since the wind above the ground is going to be your touchdown speed when you land. The optimum situation is to have winds of about 10 mph at 2,000 feet, decreasing to light and variable on the ground. Total calm all the way up to several thousand feet is no blessing. Being becalmed over trees or a lake and hopelessly watching your fuel gauges sink toward zero is no fun either!
One of the most satisfying atmospheric conditions one can encounter in a balloon is the "box wind". A box wind is a condition where the winds below 1000 feet AGL are going in one direction, and the winds above 2,000-3,000 feet AGL are going in exactly the opposite direction. Normally, a balloonist is going to go "downwind", landing five to ten miles away from where he or she took off. But with a box wind, it is possible with luck and skill to actually return to the field you took off from. One of the reasons Albuquerque has become the unofficial "Ballooning Capitol of the World" is that the morning winds in the Rio Grande River valley often will be going in one direction and the winds a couple thousand feet up heading in the opposite direction. It can make for quite a sight in October with many of the 850 balloons staying more or less in the vicinity of the launch field!
Capricious, subtle shifts in local winds combined with balloons changing altitudes can cause balloons to get quite close and even touch. And at rallies, dozens or even a hundred or more balloons can be sharing the same airspace. Balloons touching ("kissing") fabric-to-fabric is not at all dangerous. Ascending directly into a balloon above or descending directly onto a balloon below can be catastrophic, as the lower balloon's top vent or deflation port can be forced open leading to an uncontrollable descent. One balloon dragging it's basket upward or downward along the side of another balloon could also cause a nasty tear in the side of that balloon. Because balloons have excellent visibility downward and none upward, and because a balloon low could be forced into the ground or into powerlines, a strict rule of ballooning is that the lower of two balloons always has the right-of-way.