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Empennage

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The empennage is the structural assembly located at the rear of an aircraft.

Aircraft tail
Aircraft tail

It is also commonly called the tail or tail assembly. This structure is vital because it provides stability during flight. Its function is very similar to the feathers on an arrow. The name comes from a French verb meaning "to feather an arrow." Without an empennage, many early aircraft were virtually unflyable.

Empennage components
Empennage components

While most planes have one, some rare designs like the Northrop B-2 are heavier-than-air aircraft without any empennage at all.

The empennage manages the flight dynamics of an aircraft through specific movements. These movements are known as yaw and pitch.

flight dynamics with text
flight dynamics with text

The horizontal tailplane manages pitch, which is the up-and-down motion of the nose. The front part is the fixed horizontal stabiliser. The rear part is the elevator, a movable aerofoil. On some planes, the entire unit moves as one piece called a stabilator. The vertical fin manages yaw, which is the side-to-side motion of the nose. The fixed part is the vertical stabiliser. The movable part is the rudder. When pilots use the rudder with the ailerons, they create a coordinated banking turn.

Engineers use different trim devices to help pilots fly more easily. These devices reduce the need for constant pressure on the controls. One type is a trim tab, which is a small part on the rear of the elevator or rudder. Another type is an adjustable stabiliser that can be jacked to a new angle. Some aircraft use a bungee trim system with a spring. Others use an anti-servo tab to increase the feel of the control force. A servo tab can actually move the main control surface itself. In multi-engine planes, trim tabs on the rudder help the pilot keep the plane straight if one engine is not working.

There are many ways to configure a tailplane. A conventional tail is the simplest design. It has the vertical and horizontal stabilisers mounted to the rear of the fuselage. This type is used in about 60% of current aircraft designs. It is also used in about 80% of all aircraft ever made.

tail fuselage mounted
tail fuselage mounted

You can see this on a small Cessna 172 or a massive Airbus A380. A cruciform tail places the horizontal stabilisers midway up the vertical fin.

tail cruciform
tail cruciform

This looks like a cross from the front. This design keeps the stabilisers out of the engine wake. A T-tail mounts the horizontal stabiliser on top of the fin.

tail T
tail T

T-tails are efficient at low speeds but can be harder to recover from a spin.

Some aircraft use more complex fin and tailplane arrangements. A twin tail, or H-tail, uses two small vertical stabilisers on either side of the horizontal part.

tail twin tailplane mounted
tail twin tailplane mounted

Examples include the Avro Lancaster. A twin boom design uses two separate booms with a vertical stabiliser on each.

tail twin boom
tail twin boom

Some planes use V-tails, where the surfaces are set at diagonal angles.

tail V
tail V

These surfaces are called ruddervators because they handle both yaw and pitch. A V-tail can be lighter and produce less drag. There are also Y-tails, which add a lower fin, and X-tails, which use four diagonal surfaces.

An unusual design is the outboard tail. This system splits the tail into two halves. Each half is mounted on a short boom behind the wing tips.

This design can reduce drag and improve efficiency. It was first developed during World War II by Richard Vogt and George Haag. It reappeared much later on the SpaceShipOne in 2003. Finally, some aircraft are described as "tailless." These usually have all their horizontal control surfaces on the main wing. Most still use a vertical fin and rudder to stay stable.

The empennage is also a critical location for safety equipment. Many aircraft store the cockpit voice recorder and the flight data recorder in the tail. They also place the emergency locator transmitter (ELT) there. This is because the rear of the aircraft often provides better protection during a crash. By placing these tools in the empennage, engineers make it more likely that important data can be recovered after an accident.

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🖼️ Images & Media (17)
File:Aircraft tail.JPG
Aircraft tail.JPG
File:Empennage components.png
Empennage components.png
File:flight dynamics with text.svg
flight dynamics with text.svg
File:tail fuselage mounted.svg
tail fuselage mounted.svg
File:tail cruciform.svg
tail cruciform.svg
File:tail T.svg
tail T.svg
File:tail plane flying.svg
tail plane flying.svg
File:tail twin tailplane mounted.svg
tail twin tailplane mounted.svg
File:tail twin boom.svg
tail twin boom.svg
File:tail twin wing mounted.svg
tail twin wing mounted.svg
File:tail fin triple.svg
tail fin triple.svg
File:tail fin ventral.svg
tail fin ventral.svg

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