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Atwin tail is a type ofvertical stabilizer arrangement found on theempennage of someaircraft. Two vertical stabilizers—often smaller on their own than a single conventional tail would be—are mounted at the outside of the aircraft'shorizontal stabilizer. This arrangement is also known as anH-tail,[1] as it resembles a capital "H" when viewed from the rear. The twin tail was used on a wide variety of World War II multi-engine designs that saw mass production, especially on the AmericanB-24 Liberator andB-25 Mitchell bombers, the BritishAvro Lancaster andHandley Page Halifax heavy bombers, and the Soviet Union'sPetlyakov Pe-2 attack bomber.
It can be easily confused for the similarly namedtwin-boom (or "double tail") arrangement, which has two separate tail-booms from the same fuselage rather than a single tail with twin stabilizers (a singular "twin tail" vs. two identical tails).
One variation on the twin tail is thetriple tail, but the twin-boom arrangement can also be considered a variation of the twin tail.
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Separating the control surfaces allows for additionalrudder area or vertical surface without requiring a massive single tail. On multi-enginepropeller designs twin fin and rudders operating in the propellerslipstream give greater rudder authority and improved control at lowairspeeds, and whentaxiing. A twin tail can also simplifyhangar requirements, give dorsal gunners enhanced firing area, and in some cases reduce the aircraft's weight.[2][failed verification] It also affords a degree ofredundancy: if one tail is damaged, the other may remain functional.
Twin tails with canted fins lean outboard of the turbulence created by the that huge, wide fuselage, improving stability and control especially at high angles of attack.[citation needed]
Most often, the twin vertical surfaces are attached to the ends of the horizontal stabilizer, but a few aircraft, like theArmstrong Whitworth Whitley,Mitsubishi G3M andDornier Do 19 bombers, had their twin vertical surfaces mounted to the upper surface of the fixed stabilizer instead, at some distanceinwards from the horizontal stabilizer's tips.
Manycanard aircraft designs incorporate twin tails on the tips of the mainwing. Very occasionally, three or more tails are used, as on theBreguet Deux-Ponts,Lockheed Constellation andBoeing 314 Clipper. A very unusual design can be seen on theC-2 Greyhound andE-2 Hawkeye, which has two additional vertical tails fixed to the horizontal stabilizer between the normal vertical twin-tail surfaces. This arrangement was chosen for the stringent size limitations of carrier-based aircraft.
A special case of twin tail is the twin-boom tail or double tail, where the aft airframe consists of two separate fuselages, "tail booms", which each have a rudder but are usually connected by a single horizontal stabilizer. Examples of this construction are the twin-enginedLockheed P-38 Lightning;Northrop P-61 Black Widow;Focke-Wulf Fw 189; the single jet-enginedde Havilland Vampire; cargo-carryingFairchild C-119 Flying Boxcar and the little knownTransavia PL-12 Airtruk.
Significant aircraft with twin tails include theConsolidated B-24 Liberator,Handley Page Halifax,Avro Lancaster, and P-38 Lightning. The arrangement is not limited toWorld War II-era aircraft, however. Manyfighter aircraft, like theGrumman F-14 Tomcat,McDonnell Douglas F-15 Eagle,Sukhoi Su-27,MiG-29, andFairchild Republic A-10 Thunderbolt II, make use of twin tail configurations, as do civilian and cargo designs like theAntonov An-14,Antonov An-22,Antonov An-28,Antonov An-38,Antonov An-225,Beechcraft 18,Beriev Be-12,ERCO Ercoupe,Short 330,Rutan Long-EZ andSpaceShipOne.
TheV-22 Osprey uses a twin tail arrangement.
A twin tail section with large rudders increases stability and manuverability and allows a greater concentration of firepower to the rear.