Empennage ( or ) is an
aviationAviation is the activity involving man-made air-borne flying devices , including the people, organizations, and regulatory bodies involved with them.- History :...
term used to describe the
tailThe tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals and birds...
portion of an
aircraftAn aircraft is a vehicle which is able to fly by being supported by the air, or in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil An aircraft is a vehicle which is able to fly by being supported...
. The
empennage is also known as the
tail or
tail assembly; all three terms may be interchangeably used. The empennage gives stability to the aircraft and controls the
flight dynamicsFlight dynamics is the science of air and space vehicle orientation and control in three dimensions. The three critical flight dynamics parameters are the angles of rotation in three dimensions about the vehicle's center of mass, known as pitch, roll and yaw .Aerospace engineers develop control...
of pitch and yaw. In simple terms the empennage may be compared to the
fletchingFletching is the ancient art of aerodynamically stabilizing arrows from materials such as feathers. The word is related to the French word flèche, meaning "arrow," via Old French; the ultimate root is Frankish *fliukka....
of an arrow, colloquially, "tail feathers".
Structurally, the empennage consists of the entire tail assembly, including the
finThe vertical stabilizers, or fins, of aircraft, missiles or bombs are typically found on the aft end of the fuselage or body, and are intended to reduce aerodynamic side slip....
,
tailplaneA tailplane, also known as horizontal stabilizer, is a small lifting surface located behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixed wing aircraft such as helicopters and gyroplanes...
and the part of the
fuselageThe fuselage is an aircraft's main body section that holds crew and passengers or cargo. In single-engine aircraft it will usually contain an engine, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage which in turn is used as a floating hull...
to which these are attached.
Empennage ( or ) is an
aviationAviation is the activity involving man-made air-borne flying devices , including the people, organizations, and regulatory bodies involved with them.- History :...
term used to describe the
tailThe tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals and birds...
portion of an
aircraftAn aircraft is a vehicle which is able to fly by being supported by the air, or in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil An aircraft is a vehicle which is able to fly by being supported...
. The
empennage is also known as the
tail or
tail assembly; all three terms may be interchangeably used. The empennage gives stability to the aircraft and controls the
flight dynamicsFlight dynamics is the science of air and space vehicle orientation and control in three dimensions. The three critical flight dynamics parameters are the angles of rotation in three dimensions about the vehicle's center of mass, known as pitch, roll and yaw .Aerospace engineers develop control...
of pitch and yaw. In simple terms the empennage may be compared to the
fletchingFletching is the ancient art of aerodynamically stabilizing arrows from materials such as feathers. The word is related to the French word flèche, meaning "arrow," via Old French; the ultimate root is Frankish *fliukka....
of an arrow, colloquially, "tail feathers".
Structure
Structurally, the empennage consists of the entire tail assembly, including the
finThe vertical stabilizers, or fins, of aircraft, missiles or bombs are typically found on the aft end of the fuselage or body, and are intended to reduce aerodynamic side slip....
,
tailplaneA tailplane, also known as horizontal stabilizer, is a small lifting surface located behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixed wing aircraft such as helicopters and gyroplanes...
and the part of the
fuselageThe fuselage is an aircraft's main body section that holds crew and passengers or cargo. In single-engine aircraft it will usually contain an engine, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage which in turn is used as a floating hull...
to which these are attached. On an airliner this would be all the flying and control surfaces behind the
rear pressure bulkheadThe rear pressure bulkhead is a component of all large commercial aircraft. It is an airtight bulkhead located between the cabin and the tailfin. Its purpose is to seal the rear of the plane and thus maintain cabin pressure, and as such it is a vital part of the aircraft.Japan Airlines Flight 123...
.
The front, usually fixed section of the tailplane is called the
horizontal stabilizerThe stabilizers provide stability while the aircraft is flying straight, and the airfoil of the horizontal stabilizer balances the forces acting on the aircraft....
and is used to balance and share lifting loads of the mainplane dependent on centre of gravity considerations by limiting oscillations in pitch. The rear section is called the
elevatorElevators are control surfaces, usually at the rear of an aircraft, which control the aircraft's orientation by changing the pitch of the aircraft, and so also the angle of attack of the wing. In simplified terms, they make the aircraft nose-up or nose-down...
and is usually hinged to the horizontal stabilizer. The elevator is a movable
airfoilAn airfoil or aerofoil is the shape of a wing or blade or sail as seen in cross-section....
that controls changes in pitch, the up-and-down motion of the aircraft's nose.
The vertical tail structure (or
finA fin is a surface used to produce lift and thrust or to steer while traveling in water, air, or other fluid media. The first use of the word was for the limbs of fish, but has been extended to include other animal limbs and man-made devices....
) has a fixed front section called the
vertical stabilizerThe vertical stabilizers, or fins, of aircraft, missiles or bombs are typically found on the aft end of the fuselage or body, and are intended to reduce aerodynamic side slip....
, used to restrict side-to-side motion of the aircraft (yawing). The rear section of the vertical fin is the
rudderA rudder is a device used to steer a ship, boat, submarine, hovercraft, aircraft,or other conveyance that moves through a fluid . On an aircraft the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane...
, a movable airfoil that is used to turn the aircraft in combination with the ailerons.
In every empennage, some arrangement is made for the provision of trim to allow minor adjustment of airflow over the control surface and to unload the pilot from the need to maintain constant pressure on the elevator or rudder controls. The trim may take the form of trim tabs on the rear of the elevators or rudder which act to force those surfaces in the desired direction.
The aircraft's 'black box' (
cockpit voice recorderA Cockpit Voice Recorder , sometimes referred to as a "black box", is a flight recorder used to record the audio environment in the flightdeck of an aircraft for the purpose of investigation of accidents and incidents. This is typically achieved by recording the signals of the microphones and...
and
flight data recorderA flight data recorder is a kind of flight recorder. It is a device used to record specific aircraft performance parameters...
) are often located in the empennage, because the aft of the aircraft better survives the destructive forces (in most crash scenarios).
Trim
For trim, a stabilizer may be hinged at its trailing edge, forward of the elevator and adjustably jacked a few degrees in incidence either up or down. Early aircraft had a spring in the control circuit which provided an adjustable preload in the desired direction.
Multi-engined aircraft always have trim tabs on the rudder when asymmetric forces would impose unusual loads on the pilot's rudder controls and sophisticated light aircraft may incorporate rudder trim also, though more usually, a ground adjustable trim tab is used to elimintate undesired yaw in cruising flight.
Tail configurations
Aircraft empennage designs may be classified broadly according to the fin and tailplane configurations.
The overall shapes of individual tail surfaces (tailplane planforms, fin profiles) are similar to Wing planforms.
Tailplanes
The tailplane comprises the tail-mounted fixed horizontal stabiliser and movable elevator. Besides its planform, it is characterised by:
- No of tailplanes - from 0 (Tailless
A tailless aircraft traditionally has all its horizontal control surfaces on its main wing surface. It has no horizontal stabilizer - either tailplane or canard foreplane . A 'tailless' type usually still has a vertical stabilising fin and control surface...
or canard) to 3 (Roe triplaneThe Roe I Triplane was an early aircraft, the first all-British aircraft to fly . It featured not only a triplane wing, but a triplane tail as well...
)
- Location of tailplane - mounted high, mid or low on the fuselage, fin or tail booms.
- Fixed stabiliser and movable elevator surfaces, or a single combined stabilator or flying tail. (General Dynamics F-111
The General Dynamics F-111 "Aardvark" is a medium-range interdictor and tactical strike aircraft that also fills the roles of strategic bomber, reconnaissance, and electronic warfare in its various versions. Developed in the 1960s and first entering service in 1967, the United States Air Force ...
)
Some locations have been given special names:
- Cruciform: mid-mounted on the fin (Hawker Sea Hawk
The Hawker Sea Hawk was a British single-seat jet fighter of the Fleet Air Arm , the air branch of the Royal Navy , built by Hawker Aircraft and its sister company, Armstrong Whitworth Aircraft. Although its origins stemmed from earlier Hawker piston-engined fighters, the Sea Hawk became the...
)
- T-tail
thumb|right|Grob motor gliderA T-tail is an aircraft tail stabilizer arrangement in which the horizontal surfaces are mounted to the top of the vertical stabilizer. Traditionally, the horizontal control surfaces are mounted to the fuselage at the base of the vertical stabilizer...
: high-mounted on the fin (Gloster JavelinThe Gloster Javelin was an "all-weather" interceptor aircraft that served with Britain's Royal Air Force in the late 1950s and most of the 1960s...
)
Fuselage mounted |
Cruciform |
T-tail |
Flying tailplane |
Fins
The fin comprises the fixed vertical stabiliser and rudder. Besides its profile, it is characterised by:
- No. of fins - from none (McDonnell Douglas X-36
The McDonnell Douglas X-36 Tailless Fighter Agility Research Aircraft was a subscale prototype jet designed to fly without the traditional tail surfaces common on most aircraft.-Design and development:...
) to three (Lockheed ConstellationThe Lockheed Constellation was a four engine propeller-driven airliner built by Lockheed between 1943 and 1958 at its Burbank, California, USA, facility. A total of 856 aircraft were produced in four models, all distinguished by a triple-tail design and dolphin-shaped fuselage...
).
- Location of fins - on the fuselage (over or under), tailplane, tail booms or wings
Twin fins may be mounted on:
- The tailplane (Avro Lancaster
The Avro Lancaster was a British four-engined Second World War heavy bomber made initially by Avro for the Royal Air Force . It first saw active service in 1942, and together with the Handley Page Halifax it was one of the main heavy bombers of the RAF, the RCAF and squadrons from other...
)
- Twin tail booms (de Havilland Vampire
The de Havilland DH.100 Vampire was a British jet-engined fighter of the Second World War, the second jet-powered aircraft commissioned by the Royal Air Force during the War , although it was not used in combat. The Vampire served with front line RAF squadrons until 1955 and continued in use as a...
)
- The wings (F7U Cutlass
The Vought F7U Cutlass was a United States Navy carrier-based jet fighter and fighter-bomber of the early Cold War era. It was a highly unusual, semi-tailless design, allegedly based on aerodynamic data and plans captured from the Arado company at the end of World War II, though Vought designers...
)
Tailplane mounted |
Twin tailboom |
Wing mounted |
Unusual fin configurations include:
- Triple fins (Lockheed Constellation
The Lockheed Constellation was a four engine propeller-driven airliner built by Lockheed between 1943 and 1958 at its Burbank, California, USA, facility. A total of 856 aircraft were produced in four models, all distinguished by a triple-tail design and dolphin-shaped fuselage...
)
- Ventral fin, often in addition to a conventional fin (Dornier Do 335
The Dornier Do 335 Pfeil , unofficially also Ameisenbär , was a World War II heavy fighter built by the Dornier company. The Pfeils performance was much better than that of other twin-engine designs due to its unique "push-pull" layout...
)
Other tail configurations
An alternative to the fin-and-tailplane approach is provided by the
V-tailIn aircraft, a V-tail is an unconventional arrangement of the tail control surfaces that replaces the traditional fin and horizontal surfaces with two surfaces set in a V-shaped configuration when viewed from the front or rear of the aircraft...
. Here, two angled tail surfaces act differentially to provide yaw control (in place of the rudder) and together to provide pitch control (in place of the elevator).
The
Pelikan tailThe Pelikan tail is an experimental tail design for fighter jets. Originally conceived by Ralph Pelikan, who hired into McDonnell Aircraft, later worked for McDonnell Douglas and after another merger, retired from Boeing. His design has not to date been incorporated into any publicly available jets...
is an all-flying variation on the V tail. It was proposed for the
Boeing X-32The Boeing X-32 was a multi-purpose jet fighter in the Joint Strike Fighter contest. It lost to the Lockheed Martin X-35 demonstrator which was further developed into the F-35 Lightning II.-Background:...
but abandoned.