When the Top Guns Go Boom

During the months from December to April, the Archipelago of islands the Beach Boys call home is host to some of the very best flying conditions anywhere. We also have learned that pilots admire sailing, just as most sailors have a fascination with airplanes. Over the years, the Marco Beach Boys and Girls have also learned that the lessons we learn from our visitors in winter can be some of the best stories ever.

This amazing trend was confirmed recently on a perfectly clear day when there was not a cloud in the sky. We were just offshore, with Marco and Capri offering a picturesque skyline, when a distant double boom of what sounded like thunder punched through the air and caught almost everyone unaware. A few of the newcomers looked up in alarm and asked: “Thunder?” After the statement that was really a question led to concerned faces searching the horizon for signs of trouble, the fighter pilot we had onboard smiled and shook his head. “That’s not thunder,” he said. “That was a sonic boom. There are always some supersonic training exercises just offshore between Tampa and Key West.”

Before anyone could respond, our retired fighter pilot began to explain in simple terms just how amazing supersonic flight could be and why south Florida is special for supersonic aviators.

“Florida has some of the best flying conditions anywhere,” our Top Gun pilot began. “Student pilots from all over the world come to Florida and learn how to fly. The pilots of the U.S. armed forces are no exception, and some of the finest jet fighters in the world push the aeronautical envelope beyond the speed of sound, and when that happens, widows shake, glassware trembles, and a few folks will run out of their homes imagining an earthquake.”

“We can begin to understand sonic booms better by considering what happens when a stone is tossed into a body of water. Little ripples spread out from where stone splashes and makes circular waves that fan outward from the point of impact. When a slow boat travels through the water, the same type of waves spread out from behind as the boat displaces water, but when the boat begins to speed up, the waves ahead of the boat cannot get out of the way fast enough. When the speed of the boat overtakes the waves ahead, a wake or large wave forms behind the boat. A wake is the large wave forming from all the smaller waves that were moving ahead of the boat but were overtaken and forced aside.”

 “When airplanes fly through the air, they produce waves of sound,” he said, continuing his lesson. “When a small propeller plane or even an airliner flies through the air, they are moving slower than the speed of sound and are like the slow boat on the water. These slower aircraft are in the “no wake zone,” and are not traveling fast enough to push the sound waves ahead and out of the way. A sonic boom occurs when the sound waves that were unfolding ahead of the plane are suddenly overtaken and forced aside. When a speedboat overtakes the ripple waves ahead and forces them behind, a wake or larger wave is created. When a jet flies faster than the speed of sound, the wake it creates is a sonic boom.”

“Hanna Reitsch was a test pilot for Germany in the Second World War and she flew an experimental rocket plane that might have been the first aircraft to break the sound barrier,” he said.

“Chuck Yeager is the most famous test pilot ever. During October in 1947 as a test pilot for the newly created United States Air Force, Yeager broke the sound barrier with a rocket powered X-1 rocket plane.”

“No earth-bound human had ever heard a sonic boom before the 1940s and many reports regarding the earlier test flights describe ground crews suddenly looking aloft with alarm.” Our jet fighter pilot paused to smile again. “Just like today when we heard the sonic boom just off the beach. After the booming thunder of the first sonic waves, the ground crews had simply considered the experimental rocket planes might have exploded.”

With everyone onboard our offshore excursion now fascinated by our visiting jet fighter pilot and his explanation of supersonic thunder, our youngest passenger perked up and asked. “What would happen if a fighter jet flew over us making the big waves?”

“There are strict regulations regarding areas of supersonic flight,” he responded. “The Air Force and Navy regularly conduct supersonic jet fighter maneuvers to ensure the success and survival of pilots and aircrews during actual combat. With a major interest in responsibility for everyone, the Air Force, the Navy, and the Federal Aviation Administration require that whenever possible, all supersonic flights are to be over open water, above 10,000 feet, and at least 15 miles from land.”

“It is important to know that there are two different sonic boom types,” he continued. “The “N” wave and the “U” wave. The “N” wave is produced by straight-line supersonic flight and has a consistent but lighter effect on the ground. The overpressure ground effect of an “N” wave is measured at one to ten pounds of pressure per-square-foot. The “U” wave is very different however and is produced when fighter aircraft climb and turn well above Mach One. This type of sonic boom is focused and can release up to 21 pounds per-square-foot of ground-effect pressure. The strongest sonic boom ever recorded was 144 pounds per-square-foot, and there is a possibility that windows can be shattered by strong sonic booms.”

As the Beach Boys and Girls live, work, and play on Marco, Goodland, and the Isles of Capri, we are in the sonic boom alley of jet fighter land. The uninhabited Ten Thousand Islands stretch out to the south, the Everglades to the southeast, and with Naples our nearest neighbor to the north, there could be no better training area for supersonic flight.

In the past, on perfectly clear weather days, many islanders have been alarmed by trembling windows, China cabinet vibrations, and even slight tremors in major structures. Consider that the vibrations we sometimes feel are only the airborne military, training and stretching their wings.

Tom Williams is a Marco Islander and the author of two books: “Lost and Found” and “Surrounded by Thunder—the Story of Darrell Loan and the Rocket Men.” Both books are available on Kindle and Nook.