# Empennage

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Tail section of an aircraft containing stabilisers

The empennage of an [Atlas Air](/source/Atlas_Air) [Boeing 747-200](/source/Boeing_747-200)

The **empennage** ([/ˌɑːmpɪˈnɑːʒ/](https://en.wikipedia.org/wiki/Help:IPA/English) or [/ˈɛmpɪnɪdʒ/](https://en.wikipedia.org/wiki/Help:IPA/English)), also known as the **tail** or **tail assembly**, is a structure at the rear of an aircraft that provides stability during flight, in a way similar to the feathers on an [arrow](/source/Arrow).[1]: 194[2]: 10[3] The term derives from the [French language](/source/French_language) verb *empenner* which means "[to feather](/source/Fletching) an arrow".[4] Most aircraft feature an empennage incorporating vertical and horizontal stabilising surfaces which stabilise the [flight dynamics](/source/Flight_dynamics) of [yaw](/source/Yaw_(rotation)) and [pitch](/source/Pitch_(flight)),[1]: 194[2]: 10 as well as housing [control surfaces](/source/Flight_control_surface).

Many early aircraft that lacked a stabilising empennage were virtually unflyable, despite having other effective control surfaces. Even so-called "[tailless aircraft](/source/Tailless_aircraft)" usually have a tail fin (usually a [vertical stabiliser](/source/Vertical_stabiliser)). Heavier-than-air aircraft without any kind of empennage (such as the [Northrop B-2](/source/Northrop_B-2)) are rare, and generally use specially shaped [airfoils](/source/Airfoil) whose trailing edge provide pitch stability, and [rearward-swept wings](/source/Swept_wing), often with [dihedral](/source/Dihedral_(aeronautics)) to provide the necessary [yaw](/source/Aircraft_principal_axes) stability. In some aircraft with swept wings, the airfoil section or angle of incidence may change radically towards the tip.

## Structure

The major components of an aeroplane's empennage

Structurally, the empennage consists of the entire tail assembly, including the [tailfin](/source/Vertical_stabiliser), the [tailplane](/source/Tailplane) and the part of the [fuselage](/source/Fuselage) to which these are attached.[1]: 194[2]: 10 On an airliner this would be all the flying and control surfaces behind the [rear pressure bulkhead](/source/Rear_pressure_bulkhead).

[Yaw, pitch, and roll](/source/Aircraft_principal_axes) in an aircraft

The front (usually fixed) section of the [tailplane](/source/Tailplane) is called the *horizontal stabiliser* and is used to provide pitch stability. The rear section of the tailplane is called the [elevator](/source/Elevator_(aircraft)), and is a movable [aerofoil](/source/Aerofoil) that controls changes in pitch, the up-and-down motion of the aircraft's nose. In some aircraft the horizontal stabiliser and elevator are one unit, and to control pitch the entire unit moves as one. This is known as a *[stabilator](/source/Stabilator)* or *full-flying stabiliser*.[1]: 194[2]: 10

The [vertical tail structure](/source/Fin) has a fixed front section called the *[vertical stabiliser](/source/Vertical_stabiliser)*, used to control yaw, which is movement of the fuselage right to left motion of the nose of the aircraft. The rear section of the vertical fin is the *[rudder](/source/Rudders#Aircraft_rudders)*, a movable aerofoil that is used to turn the aircraft's nose right or left. When used in combination with the [ailerons](/source/Aileron), the result is a banking turn, a *coordinated turn*, the essential feature of aircraft movement.[1]: 194[2]: 10

Some aircraft are fitted with a tail assembly that is hinged to pivot in two axes forward of the fin and stabiliser, in an arrangement referred to as a *movable tail*. The entire empennage is rotated vertically to actuate the horizontal stabiliser, and sideways to actuate the fin.[2]: 14

The aircraft's [cockpit voice recorder](/source/Cockpit_voice_recorder), [flight data recorder](/source/Flight_data_recorder) and [emergency locator transmitter](/source/Emergency_locator_transmitter) (ELT) are often located in the empennage, because the aft of the aircraft provides better protection for these in most aircraft crashes.

## Trim

In some aircraft, [trim](/source/Trim_(aircraft)) devices are provided to eliminate the need for the pilot to maintain constant pressure on the elevator or rudder controls.[2]: 14[5]

The trim device may be:

- A [trim tab](/source/Trim_tab) on the rear of the elevators or rudder which act to change the aerodynamic load on the surface. Usually controlled by a cockpit wheel or crank.[2]: 14[6]

- An [adjustable stabiliser](/source/Adjustable_stabilizer) into which the stabiliser may be hinged at its spar and adjustably jacked a few degrees in incidence either up or down. Usually controlled by a cockpit crank.[2]: 14[1]: 524

- A [bungee](/source/Bungee_cord) trim system which uses a spring to provide an adjustable preload in the controls. Usually controlled by a cockpit lever.[2]: 14[5]

- An [anti-servo tab](/source/Anti-servo_tab) used to trim some elevators and stabilators as well as increased control force feel. Usually controlled by a cockpit wheel or crank.[2]: 14

- A [servo tab](/source/Servo_tab) used to move the main control surface, as well as act as a trim tab. Usually controlled by a cockpit wheel or crank.[2]: 14

Multi-engined aircraft often have [trim tabs](/source/Trim_tab) on the rudder to reduce the pilot effort required to keep the aircraft straight in situations of asymmetrical thrust, such as single engine operations.[6]

## 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](/source/Wing_configuration#Wing_planform).

### Tailplanes

Main article: [tailplane](/source/Tailplane)

The tailplane comprises the tail-mounted fixed horizontal stabiliser and movable elevator. Besides its [planform](/source/Wing_configuration#Wing_planform), it is characterised by:

- Configuration: [tailless](/source/Tailless_aircraft) or [canard](/source/Canard_aircraft)

- 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](/source/Stabilator) or "[all]-flying tail"[7]

Some locations have been given special names:

**Conventional tail**
- The [vertical stabiliser](/source/Vertical_stabiliser) and [horizontal stabilisers](/source/Horizontal_stabiliser) are mounted to the rear of the fuselage. This is the simplest configuration that performs all three aspects of the function of a tail: trim, stability, and control.[8] Around 60% of current aircraft designs[8] — and about 80% ever[9] — incorporate this type of tail. Examples are found on aircraft of every size and role, from general aviation types like the ubiquitous [Cessna 172](/source/Cessna_172) to the largest airliners ever flown, such as the [Airbus A380](/source/Airbus_A380). Examples of this type of tail were in use as early as the [Blériot VII](/source/Bl%C3%A9riot_VII) of 1907.

**[Cruciform tail](/source/Cruciform_tail)**
- The horizontal stabilisers are placed midway up the vertical stabiliser, giving the appearance of a [cross](/source/Cross) when viewed from the front. Cruciform tails are often used to keep the horizontal stabilisers out of the engine wake, while avoiding many of the disadvantages of a [T-tail](/source/T-tail). Examples include the [Hawker Sea Hawk](/source/Hawker_Sea_Hawk) and [Douglas A-4 Skyhawk](/source/Douglas_A-4_Skyhawk).

**[T-tail](/source/T-tail)**
- The horizontal stabiliser is mounted on top of the fin, creating a "T" shape when viewed from the front. T-tails keep the stabilisers out of the engine wake, and give better pitch control. T-tails have a good [glide ratio](/source/Glide_ratio), and are more efficient on low-speed aircraft. However, the T-tail has several disadvantages. It is more likely to enter a [deep stall](/source/Stall_(flight)#Deep_stall), and is more difficult to recover from a spin. For this reason a small secondary stabiliser or **tail-let** may be fitted lower down where it will be in free air when the aircraft is stalled.[10] A T-tail must be stronger, and therefore heavier than a conventional tail. T-tails also tend to have a larger [radar cross section](/source/Radar_cross_section). Examples include the [Gloster Javelin](/source/Gloster_Javelin) and [McDonnell Douglas DC-9](/source/McDonnell_Douglas_DC-9).

Fuselage mounted Cruciform T-tail Flying tailplane

### Fins

Main article: [Vertical stabilizer](/source/Vertical_stabilizer)

The fin comprises the fixed vertical stabiliser and rudder. Besides its [profile](/source/Wing_configuration#Wing_planform), it is characterised by:

- Number of fins: usually one or two

- Location of fins: on the fuselage (over or under), tailplane, tail booms or wings

Twin fins may be mounted at various points:

- **[Twin tail](/source/Twin_tail)** A twin tail, also called an **H-tail**, consists of two small vertical stabilisers on either side of the horizontal stabiliser. Examples include the [Antonov An-225 Mriya](/source/Antonov_An-225_Mriya), [B-25 Mitchell](/source/B-25_Mitchell), [Avro Lancaster](/source/Avro_Lancaster), and [ERCO Ercoupe](/source/ERCO_Ercoupe).

- **[Twin boom](/source/Twin-boom_aircraft)** A twin boom has two fuselages or booms, with a vertical stabiliser on each, and a horizontal stabiliser between them. Examples include the [Northrop P-61 Black Widow](/source/Northrop_P-61_Black_Widow), [P-38 Lightning](/source/P-38_Lightning), [de Havilland Sea Vixen](/source/De_Havilland_Sea_Vixen), [Sadler Vampire](/source/Sadler_Vampire), and [Edgley Optica](/source/Edgley_Optica).

- **Wing mounted** midwing as on the [F7U Cutlass](/source/F7U_Cutlass) or on the wing tips as on the [Handley Page Manx](/source/Handley_Page_Manx) and [Rutan Long-EZ](/source/Rutan_Long-EZ)

Tailplane mounted Twin tail boom Wing mounted

Unusual fin configurations include:

- **No fin** – as on the [McDonnell Douglas X-36](/source/McDonnell_Douglas_X-36). This configuration is sometimes incorrectly referred to as "tailless".

- **Multiple fins** – examples include the [Lockheed Constellation](/source/Lockheed_Constellation) (three), [Bellanca 14-13](/source/Bellanca_14-13) (three), and the [Northrop Grumman E-2 Hawkeye](/source/Northrop_Grumman_E-2_Hawkeye) (four).

- **Ventral fin** – underneath the fuselage. Often used in addition to a conventional fin as on the ([North American X-15](/source/North_American_X-15) and [Dornier Do 335](/source/Dornier_Do_335)).

Triple fins Ventral fin

### V, Y and X tails

An alternative to the fin-and-tailplane approach is provided by the [V-tail](/source/V-tail) and [X-tail](https://en.wikipedia.org/w/index.php?title=X-tail&action=edit&redlink=1) designs. Here, the tail surfaces are set at diagonal angles, with each surface contributing to both pitch and yaw. The control surfaces, sometimes called [ruddervators](/source/Ruddervator), act differentially to provide yaw control (in place of the rudder) and act together to provide pitch control (in place of the elevator).[1]

- **V tail:** A V-tail can be lighter, produce less drag, and have a smaller radar signature than a conventional tail in some situations. Examples include the [Fouga Magister](/source/Fouga_Magister) trainer, [Northrop Grumman RQ-4 Global Hawk](/source/Northrop_Grumman_RQ-4_Global_Hawk), [Boeing X-37](/source/Boeing_X-37) spaceplane, [Beechcraft Model 35 Bonanza](/source/Beechcraft_Bonanza), and [Davis DA-2](/source/Davis_DA-2).

- **Inverted V tail:** Used by the unmanned [Predator](/source/General_Atomics_MQ-1_Predator), the ultralight [Lazair](/source/Lazair), and the homebuilt [Mini-IMP](/source/Aerocar_Mini-IMP).

- **Y tail**: A V-tail with an added lower vertical fin (generally used to protect an aft propeller), as [LearAvia Lear Fan](/source/LearAvia_Lear_Fan), [Waiex](/source/Sonex_Aircraft_Sonex), and [Monnett Moni](/source/Monnett_Moni).

- **X tail:** The [Lockheed XFV](/source/Lockheed_XFV) had an "X" tail, which was reinforced and fitted with a wheel on each surface so that the craft could sit on its tail and take off and land vertically.

V-tail Inverted V-tail X-tail

### Outboard tail

SpaceShipOne at the US National Air and Space Museum

An outboard tail is split in two, with each half mounted on a short boom just behind and outboard of each wing tip. It comprises outboard horizontal stabilisers (OHS) and may or may not include additional boom-mounted [vertical stabilisers](/source/Vertical_stabilizer) (fins). In this position, the tail surfaces interact constructively with the wingtip vortices and, with careful design, can significantly reduce drag to improve efficiency, without adding unduly to the structural loads on the wing.[11]

The configuration was first developed during World War II by [Richard Vogt](/source/Richard_Vogt_(aircraft_designer)) and George Haag at [Blohm & Voss](/source/Blohm_%26_Voss_(aircraft)). The [Skoda-Kauba SL6](https://en.wikipedia.org/w/index.php?title=Skoda-Kauba_SL6&action=edit&redlink=1) tested the proposed control system in 1944 and, following several design proposals, an order was received for the [Blohm & Voss P 215](/source/Blohm_%26_Voss_P_215) just weeks before the war ended.[12][13] The outboard tail reappeared on the [Scaled Composites SpaceShipOne](/source/Scaled_Composites_SpaceShipOne) in 2003 and [SpaceShipTwo](/source/SpaceShipTwo) in 2010.[14]

### Tailless aircraft

Main article: [Tailless aircraft](/source/Tailless_aircraft)

The [DH108 *Swallow*](/source/De_Havilland_DH_108) had a tailless design.

A **tailless aircraft** (often **tail-less**) traditionally has all its horizontal control surfaces on its main wing surface. It has no [horizontal stabiliser](/source/Horizontal_stabiliser) –either tailplane or [canard](/source/Canard_(aeronautics)) foreplane (nor does it have a second wing in [tandem](/source/Tandem_wing) arrangement). A "tailless" type usually still has a vertical stabilising fin ([vertical stabiliser](/source/Vertical_stabiliser)) and control surface ([rudder](/source/Rudder)). However, [NASA](/source/NASA) adopted the "tailless" description for the novel [X-36 research aircraft](/source/McDonnell_Douglas_X-36) which has a canard foreplane but no vertical fin.[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*]

## See also

- [S-duct](/source/S-duct)

- [Tail-sitter](/source/Tail-sitter)

- [Trijet](/source/Trijet)

## References

1. ^ [***a***](#cite_ref-Crane_1997_1-0) [***b***](#cite_ref-Crane_1997_1-1) [***c***](#cite_ref-Crane_1997_1-2) [***d***](#cite_ref-Crane_1997_1-3) [***e***](#cite_ref-Crane_1997_1-4) [***f***](#cite_ref-Crane_1997_1-5) [***g***](#cite_ref-Crane_1997_1-6) Crane, Dale (1997). *Dictionary of Aeronautical Terms* (3rd ed.). Aviation Supplies & Academics. p. 194. [ISBN](/source/ISBN_(identifier)) [1-56027-287-2](https://en.wikipedia.org/wiki/Special:BookSources/1-56027-287-2).

1. ^ [***a***](#cite_ref-GroundUp_2-0) [***b***](#cite_ref-GroundUp_2-1) [***c***](#cite_ref-GroundUp_2-2) [***d***](#cite_ref-GroundUp_2-3) [***e***](#cite_ref-GroundUp_2-4) [***f***](#cite_ref-GroundUp_2-5) [***g***](#cite_ref-GroundUp_2-6) [***h***](#cite_ref-GroundUp_2-7) [***i***](#cite_ref-GroundUp_2-8) [***j***](#cite_ref-GroundUp_2-9) [***k***](#cite_ref-GroundUp_2-10) [***l***](#cite_ref-GroundUp_2-11) Peppler, I.L., ed. (1996). *From the Ground Up* (27th ed.). Aviation Publishers Co. [ISBN](/source/ISBN_(identifier)) [0-9690054-9-0](https://en.wikipedia.org/wiki/Special:BookSources/0-9690054-9-0).

1. **[^](#cite_ref-3)** ["ATA Airline Handbook"](https://web.archive.org/web/20111110141033/http://www.airlines.org/ATAResources/Handbook/Pages/AirlineHandbookChapter5HowAircraftFly.aspx). [Air Transport Association](/source/Air_Transport_Association). November 10, 2011. Chapter 5: How Aircraft Fly. Archived from [the original](http://www.airlines.org/ATAResources/Handbook/Pages/AirlineHandbookChapter5HowAircraftFly.aspx) on November 10, 2011.

1. **[^](#cite_ref-4)** ["Empennage"](https://web.archive.org/web/20120722152506/http://oxforddictionaries.com/definition/english/empennage). *Oxford Dictionaries Online*. Oxford Dictionaries. Archived from [the original](http://oxforddictionaries.com/definition/english/empennage) on July 22, 2012.

1. ^ [***a***](#cite_ref-Reichmann_1980_p26_5-0) [***b***](#cite_ref-Reichmann_1980_p26_5-1) Reichmann, Helmet (1980). *Flying Sailplanes*. Thompson Publications. p. 26.

1. ^ [***a***](#cite_ref-T52-14E_6-0) [***b***](#cite_ref-T52-14E_6-1) [Transport Canada: Aviation](/source/Transport_Canada) (1994). *Flight Training Manual* (4th ed.). Gage Educational Publishing Company. p. 12. [ISBN](/source/ISBN_(identifier)) [0-7715-5115-0](https://en.wikipedia.org/wiki/Special:BookSources/0-7715-5115-0).

1. **[^](#cite_ref-7)** Anderson, John D. *Introduction to Flight* (5th ed.). p. 517.

1. ^ [***a***](#cite_ref-sadraey289_8-0) [***b***](#cite_ref-sadraey289_8-1) Mohammad H. Sadraey, *Aircraft Design: A Systems Engineering Approach*, Wiley 2013, p.289

1. **[^](#cite_ref-9)** Snorri Gudmundsson, *General Aviation Aircraft Design: Applied Methods and Procedures*, Elsevier Science 2013, p.483

1. **[^](#cite_ref-10)** Kimberlin, Ralph D. (2003). *Flight Testing of Fixed Wing Aircraft*. AIAA. p. 380.

1. **[^](#cite_ref-11)** Muller, Kurt W. (2002). [*Analysis of a Semi-Tailless Aircraft Design*](https://web.archive.org/web/20221123054514/http://apps.dtic.mil/dtic/tr/fulltext/u2/a402729.pdf) (PDF) (Master's thesis). Naval Postgraduate School, US. Archived from [the original](http://apps.dtic.mil/dtic/tr/fulltext/u2/a402729.pdf) (PDF) on November 23, 2022.

1. **[^](#cite_ref-12)** Zdenek Titz and Jaroslav Zazvonil; "Kauba's Dwarfs", *Flying Review International*, Nov 1965, pp.169-172.

1. **[^](#cite_ref-13)** Pohlmann, Hermann. *Chronik Eines Flugzeugwerkes 1932-1945. B&V – Blohm & Voss Hamburg – HFB Hamburger Flugzeugbau* (in German). Motor Buch Verlag, 1979 [ISBN](/source/ISBN_(identifier)) [3-87943-624-X](https://en.wikipedia.org/wiki/Special:BookSources/3-87943-624-X).

1. **[^](#cite_ref-14)** Benjamin Darrenougue; "Aircraft Configurations With Outboard Horizontal Stabilizers" (Final year project report), Queens University Belfast, May 14, 2004.[\[1\]](http://hdarrenougue.free.fr/html/report.pdf)

v t e Aircraft components and systems Airframe structure Aft pressure bulkhead Cabane strut Canopy Crack arrestor Cruciform tail Dope Empennage Fabric covering Fairing Flying wires Former Fuselage Hardpoint Interplane strut Jury strut Leading edge Lift strut Longeron Nacelle Rib Spar Stabilizer Stressed skin Strut T-tail Tailplane Trailing edge Triple tail Twin tail V-tail Vertical stabilizer Wing root Wing tip Wingbox Flight controls Aileron Airbrake Artificial feel Autopilot Canard Centre stick Deceleron Dive brake Dual control Electro-hydraulic actuator Elevator Elevon Flaperon Flight control modes Fly-by-wire Gust lock HOTAS Rudder Rudder pedals Servo tab Side-stick Spoiler Spoileron Stabilator Stick pusher Stick shaker Trim tab Wing warping Yaw damper Yoke Aerodynamic and high-lift devices Active Aeroelastic Wing Adaptive compliant wing Anti-shock body Blown flap Channel wing Dog-tooth Drag-reducing aerospike Flap Gouge flap Gurney flap Krueger flap Leading-edge cuff Leading-edge droop flap LEX Slats Slot Stall strips Strake Variable-sweep wing Vortex generator Vortilon Wing fence Winglet Avionic and flight instrument systems ACAS Air data boom Air data computer Aircraft periscope Airspeed indicator Altimeter Annunciator panel Astrodome Attitude indicator Compass Course deviation indicator EFIS EICAS Flight management system Glass cockpit GPS Head-up display Heading indicator Horizontal situation indicator INS ISIS Multi-function display Pitot–static system Radar altimeter TCAS Transponder Turn and slip indicator Variometer Yaw string Propulsion controls, devices and fuel systems Autothrottle Drop tank FADEC Fuel tank Gascolator Inlet cone Intake ramp NACA cowling NACA duct Self-sealing fuel tank Splitter plate Throttle Thrust lever Thrust reversal Townend ring War emergency power Wet wing Landing and arresting gear Aircraft tire Arrestor hook Autobrake Conventional landing gear Drogue parachute Landing gear Landing gear extender Oleo strut Tricycle landing gear Tundra tire Escape systems Ejection seat Escape crew capsule Other systems Aircraft lavatory Auxiliary power unit Bleed air system Deicing boot Emergency oxygen system Environmental control system Flight recorder Hydraulic system Ice protection system In-flight entertainment system Landing lights Navigation light Passenger service unit Ram air turbine

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Adapted from the Wikipedia article [Empennage](https://en.wikipedia.org/wiki/Empennage) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Empennage?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.