In this blog post, we’ll use paper airplanes and the Boeing 747 to explore the role of an airplane’s tail and why it’s crucial for flight stability.
Just how far is the world record for throwing a paper airplane? According to Guinness World Records, on February 26, 2012, in the United States, Joe Ayoob set the world record by throwing a paper airplane made by John M. Collins 69.14 meters. Considering that it’s not easy for the average person to get a paper airplane to fly more than 10 meters, it’s easy to assume that the 69.14-meter record was achieved using some kind of special paper airplane. Surprisingly, however, the paper airplane that set the world record doesn’t look much different from the ordinary paper airplanes we’re all familiar with.
So, if you were to fly that very same world-record-breaking paper airplane yourself, how far would it go? You might expect it to fly about 30 meters, even if not quite as far as Joe Ayoob’s. However, in most cases, it would likely be difficult to even get it to fly 10 meters. At first, it might seem to be flying well, but at some point, it suddenly soars upward or plummets downward. Or it might veer off to one side and keep flying that way, eventually circling back to near the starting point. What exactly is the problem?
The main reason is that the paper airplane is unstable. To understand this, let’s take the Boeing 747—a common sight at airports—as an example. When an airplane flies forward, lift is generated on its wings. Lift is the force acting perpendicular to the airflow, created when the airflow is altered by the wing. Air naturally flows along the surface of an object. Since the upper and lower surfaces of an airplane’s wing have different shapes, the airflow differs between them, resulting in lift. In other words, as long as the airplane moves forward, upward lift is generated on the wings, allowing the airplane to stay airborne.
The problem is that this lift is generated only by the main wings. Furthermore, the main wings and the center of gravity are not aligned. Therefore, the lift acting on the main wings creates a rotational force that tries to raise the nose of the airplane. This phenomenon is easy to understand if you think of a seesaw. A seesaw moves up and down on both sides around a central axis. If you stand exactly on the axis—which is the center of gravity—the seesaw will not tilt to either side. However, if a person sits at one end far from the axis, that side goes down while the opposite side goes up. The same principle applies to an airplane. Since the center of gravity is located toward the rear but lift is generated further forward, the nose of the airplane pitches up and the tail pitches down. Even as the airplane tries to move forward, its nose keeps lifting, causing its flight attitude to become unstable.
To reduce this instability, the Boeing 747 is equipped with a horizontal stabilizer at the tail. With a horizontal stabilizer, lift—albeit small—is generated not only by the main wings but also by the horizontal stabilizer itself. This is similar to a situation where two people sit on opposite sides of a seesaw to maintain balance. Even if the two people have different weights, the seesaw remains balanced if the lighter person sits farther from the fulcrum and the heavier person sits closer to it. Similarly, even though the lift generated by the main wings is greater, the horizontal stabilizer is located farther from the center of gravity, so the two forces balance each other out. As a result, the aircraft can fly forward while maintaining a stable attitude without the nose lifting excessively.
If you look closely at a Boeing 747, you’ll see that the tail is equipped not only with a horizontal stabilizer but also with a vertical stabilizer. So, does the vertical stabilizer play a similar role? There are times when an airplane’s direction of travel and the direction its nose is pointing are misaligned. In this situation, passengers not only feel as if they are being pushed sideways, but it also becomes difficult for the airplane to fly safely in the desired direction. This is similar to a car skidding on a wet or snowy road. If this condition persists, the airplane is considered to be in a highly unstable state.
This is where the vertical stabilizer plays a crucial role. When the direction of travel and the direction the nose is pointing do not align, aerodynamic forces generate a corrective force on the vertical stabilizer. As a result, relative to the center of gravity, the tail moves to one side and the nose rotates in the opposite direction, eventually realigning the direction of travel with the direction the nose is pointing. This principle can be easily observed in everyday life. It’s the same principle by which a wind vane or a flag naturally turns in the direction of the wind. When the wind blows, the tail of the wind vane or the flag is pushed by the wind and naturally changes direction; the aircraft’s vertical stabilizer also plays a role in stabilizing the flight attitude based on the same principle.
Ultimately, the Boeing 747 is equipped with a vertical stabilizer to ensure stable flight. That is why the tail is sometimes simply called a “tail” in English, but it is also known as a “stabilizer.” This underscores just how crucial the tail is to maintaining an aircraft’s stability. While the main wings play a key role in getting the aircraft airborne, the tail is absolutely essential for maintaining safe flight and quickly restoring the aircraft’s original flight attitude when external disturbances occur. From this perspective, the fact that Joe Ayub was able to set a world record with an unstable paper airplane may have been the result of a fortunate alignment of various conditions, rather than solely due to the paper airplane’s performance. Although the tail surfaces are small compared to the main wings and might seem dispensable, in reality, even large aircraft find it difficult to maintain normal flight if the tail surfaces are severely damaged. While they may appear to be small components, they are actually vital devices that determine flight safety.
