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Don’t Bounce Off The Trees
IT MIGHT SEEM AN ODD SORT OF TRAINING FOR MEN WHO WERE SOON TO FACE THE NAZIS, BUT …
August 1975 | Volume 26, Issue 5
The Providence that looks out for small children and inebriates must certainly have a protective concern for free-balloon pilots. And indeed I suppose that is appropriate, since the pilot or passenger in a free balloon is almost as helpless against the assaults of the elements as the smallest tot or the most supine wine-bibber.
I spent World War II as a lighterthan-air pilot—a chauffeur of those large, nonrigid aircraft usually called blimps, which we affectionately referred to as “large silver birds” and which the less sympathetic derided as “sausages.” The training of a lighterthan-air pilot is somewhat similar to the flight training of a heavier-thanair pilot. It takes about the same length of time, and since many functions and even flight characteristics of these two types of flying machines are similar, a large part of the training syllabus is almost identical: aerology, for example, or navigation, or power plants. Lighterthan-air training, however, had one unique element in its program—the mastery of the free balloon.
The science of free ballooning, or aerostatics, has a very practical value in operating the power-driven blimps. Although a blimp is usually “heavy” in that the total weight of its body, fuselage, crew, fuel, and armament is greater than the lift from the gas that fills it, and although it usually becomes and remains airborne through the thrust of its engines and the airfoil characteristics of its “envelope” and fins, yet this heaviness is only relative; it is slight compared to that of conventional heavier-than-air craft. In this lies the peculiar military advantage of the blimp. It can cruise at a much slower speed for use with convoys, it can hover over a given spot for careful observation or for searching out submerged submarines, and in the event of a power failure it can be quickly ballasted to a state of equilibrium and thus float with the wind until the trouble is remedied. When a blimp is in this condition, it becomes, for all practical purposes, a free balloon. For this reason the mechanics of free ballooning were a required part of the flight training I took at Lakehurst, New Jersey, the original lighter-thanair base in the country.
During the summer of 1941, when I was a cadet at Lakehurst, l made several free-balloon flights. These were always gala occasions for us. The only thing that can compare with free ballooning as a sport, I am told by friends who know them both, is skiing. The flights were usually scheduled in the afternoon after a morning of classes and on days when the weather was agreeable, without the threat of thunderstorms. The principal reason for scheduling them in the afternoon was to catch the usual afternoon offshore breeze, since of course we had to go inland, not out to sea.
The first flight I had was an ideal one. We gathered about three o’clock down at the balloon hangar near the main gate. When the balloon was filled —with hydrogen, not helium—it was “walked” out of the hangar, heavily loaded with bags of sand. The pilot, three other cadets, and myself climbed aboard the wicket basket suspended from the balloon, into an area about four feet square, which held not only the five of us but also about twenty bags of sand. The crew of bluejackets on hand then removed the bags of sand that hung on the outside of the basket until we were just a shard “light.” The pilot then tossed over a bag of sand, the sailors released the basket, and up we shot. When we had reached about five hundred feet, the pilot valved a small amount of gas (by means of a butterfly valve at the top of the balloon from which a cord extended to the basket) to check our ascent. This is a trial-and-error business. If you valve too much, you will start down again and thus have to jettison a little sand to recover the lost altitude; it takes practice to judge the correct amount of gas to valve or sand to throw overboard. And maintaining a given altitude is a continuing problem. The slightest change in barometric pressure or air temperature changes the volume—and consequently the lift—of the gas, and corrections are frequently necessary.
The day was a beautiful one, with a light twelve-knot breeze carrying us over the countryside. I don’t think the pine flats and the cranberry bogs of Jersey have ever looked so good to me. There is no thrill I know comparable to flying so leisurely at so low an altitude. The pilot introduced us to one of the sports of the game—probably a forbidden one—“bouncing” off the trees. It sounds very simple, but it is difficult to do properly, at least for the novice, and it isn’t as safe as reading “All Hands” back in your bunk. Pick out a tall tree a few hundred yards ahead, and judging carefully the altitude, distance, and force of the wind, valve just enough gas to descend to the very top of the tree. The basket rests momentarily in the cushion of foliage; then the ropes become slack as the weight is released from the balloon proper, and it immediately springs aloft. The surge of the balloon upward has enough power to carry it to another tree, perhaps two hundred yards distant, and another bounce. In the wooded area of coastal New Jersey this can be kept up for miles. Of course if you miss a tree, you have to drop a little sand and start over again.