Does Airplane Need a Tail?

Everyone has a tail: fish, birds, airplanes. Obviously, the tail unit, or “tail,” is needed for airplanes for the same reason as for birds—to control flight. But there are tailless aircraft, and they fly too. So, maybe airplanes don’t need a tail?

Why Does an Airplane Need a Tail?

This can be explained very simply:

Just like birds, airplanes need a tail for flight stabilization and control. That’s the simple explanation, but diving deeper into the topic makes it a bit more complex and much more interesting.

What does the airplane tail do?

An arrow needs fletching for stabilization in flight. Without it, an arrow shot from a bow would deviate from its trajectory, making it hard to hit a target.

An airplane faces the same situation, which is why the tail unit is called Empennage.

The term itself comes from French — “empennage” derives from the word “empenner,” which translates to “fletching an arrow,” and “penne” means feather. By the way, in English, it’s also called empennage or tail unit.

The functions performed by the tail unit are:

• Balancing
• Control
• Ensuring stability

Typically, the “tail” consists of two parts: vertical and horizontal stabilizers. But sometimes there’s no horizontal unit (tailless design) or no tail unit at all — a “flying wing.”

In such cases, the functions of the tail are performed by other mechanisms located on the wing.

Tailless design

Balancing means equalizing forces (or more precisely, moments of force) that could cause the airplane to pitch during flight.

The thing is, an airplane is affected by lift, which pulls it upward, and the airplane’s weight, which pulls it downward. Since the points where these forces are applied don’t align, this creates what’s known in aviation as:

• “Pitching moment” — the airplane’s nose dips downward

To compensate for these moments, a horizontal tail unit is needed.

An airplane can also sway side to side, which is called “yawing.” To counteract this, a vertical tail unit, or simply a fin, is needed. Just like on a ship, their function is the same—ensuring longitudinal stability.

As for control, it’s straightforward: part of the tail unit is movable and used to control flight—turning left or right, raising or lowering the nose.

In modern supersonic combat aircraft, the horizontal tail unit, and sometimes the vertical one, is made fully movable.

What does ensuring stability mean…

In simple terms, when an airplane deviates left or right, up or down, forces arise on the tail unit that return the airplane to straight flight.

Why Does an Airplane Need a Large Tail?

When airplanes began flying at supersonic speeds, the tail unit’s area suddenly started to increase, which seems illogical. After all, the higher the speed, the greater the aerodynamic forces, so the stabilizer could be smaller. But no, it’s the opposite.

Despite the Concorde being very long, its tail is also large. Due to supersonic speed

At supersonic speeds, the center of aerodynamic forces shifts, the moment increases, and thus the horizontal tail unit needs to be larger.

As for the vertical tail unit, it’s enlarged due to the formation of shock waves, which “consume” part of the area where aerodynamic forces can be generated. This requires increasing the area here too.

Why Does an Airplane Need Two Tails?

It’s interesting to explore why an airplane might need two tails. More accurately, two fins.

The twin-fin design appeared long ago but became popular when airplanes started flying at supersonic speeds.

The thing is, at supersonic speeds, stability issues are significantly greater, so engineers had to increase the vertical tail unit’s area.

But as speeds increased, the fins became simply enormous. This meant greater strength was needed, which increased weight.

Carrying extra weight is something an airplane doesn’t need. The obvious solution is to make two fins with the same area as one large one. The weight of two will be noticeably less than one, thanks to the square-cube law.

There are other reasons why two are better than one under certain circumstances.

Two fins are less “shadowed” by the fuselage at high angles of attack. In other words, the vertical tail unit retains its effectiveness.

This is easy to see in the example of the F-18 fighter. It’s a carrier-based aircraft, meaning takeoff and landing space is limited, and angles of attack are high. Two fins mean greater stability during takeoff and landing.

Here, it’s clear that if the F-18 had one fin, it would fall into the fuselage’s “shadow”

If an airplane has two engines, making “two tails” is simpler from a design perspective, as otherwise, a structural beam would need to be placed between the engines to mount the tail, adding extra weight.

Additionally, slightly tilting the fins from the vertical positively impacts radar detectability. This can’t be done with a single stabilizer.

Airplanes Don’t Need a Tail

Now for something surprising. From an aerodynamic perspective, the tail unit is not only unnecessary for an airplane but even harmful.

1. The vertical tail unit creates drag but doesn’t generate lift.
2. The horizontal stabilizer even creates negative lift. It pulls the tail downward to compensate for the pitching moment. This is called “balancing losses.” The issue can be resolved by using a canard configuration and moving the horizontal tail unit forward.
3. All this structure is extra weight, which is generally detrimental to an airplane.

When engineers decide to eliminate everything unnecessary, they create an airplane in the flying wing configuration.

B2 Spirit

This raises an interesting question: how does this airplane fly without a tail? How are balancing, stability, and control ensured? Simply put, the wing performs all these functions. The B2 constantly “adjusts” during flight to fly straight.

The flying wing idea is not new at all; aircraft designers have long tried to eliminate the “unnecessary” tail and keep only the most essential and useful part—the wing. The first attempts began in the 1930s.

But true success came only in 1982 when the B2 bomber made its first flight. It was so challenging because flying without a tail required a complex automatic control system—in other words, a computer—otherwise, the airplane would be unstable and poorly controllable.

Now it’s clear why such a seemingly unnecessary design element is still used in aviation. You can fly without a tail. But it’s complex and expensive.

Despite all the advantages of the flying wing configuration, only 21 such aircraft were built for the world’s richest military (its successor, the B-21 Raider, is planned to be produced in a batch of 100). But all other aircraft, both civilian and military, fly with the help of a tail.

Why Do Modern Airplanes Always Have a Tail?

Modern passenger airliners are designed in the classic configuration: with a tail unit located behind the wing.

Although all designers know about the advantages of the flying wing or canard configuration, why does no one, except the military, adopt such a promising design?

Simply because anything new is a big risk. Technological risk (we’ll build it, and it won’t work as intended) and economic risk (we’ll build something that no one will buy).

Looking at the characteristics of conventional airplanes and the flying wing, it becomes clear that:

1. The flying wing is more efficient in terms of aerodynamics. The Boeing 737 carries 20 tons over a range of 3,700 kilometers, while the B-2 can deliver its 18 tons over 11,000 kilometers.
2. Large conventional airplanes with comparable range have higher maximum takeoff weight but also higher fuel consumption.
3. The cost of the B-2, excluding R&D, is $2 billion, and with R&D, up to $4 billion. Conventional airplanes are significantly cheaper.

In the end, it turns out that using the well-established tail configuration is far more efficient because it’s thoroughly developed and proven. No aircraft manufacturer seems ready to risk such enormous costs yet.

In 2007, Boeing conducted research on a scaled-down flying wing prototype, the X-48B. It was claimed that switching from the conventional configuration would reduce fuel consumption by 30%.

Boeing X-48B — tailless airliner project

Airbus hasn’t created any prototypes, limiting itself to images and a promise to create an airplane by 2035 capable of carrying 200 passengers over 3,700 kilometers using hydrogen as fuel.

It seems we won’t soon see tailless airplanes in airports, only in pictures. The classic configuration will stay with us for a long time.