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: • Configuration:
tailless or
canard • 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 "[all]-flying tail" Some locations have been given special names: ; Conventional tail : The
vertical stabiliser and
horizontal stabilisers 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. Around 60% of current aircraft designs — incorporate this type of tail. Examples are found on aircraft of every size and role, from general aviation types like the ubiquitous
Cessna 172 to the largest airliners ever flown, such as the
Airbus A380. Examples of this type of tail were in use as early as the
Blériot VII of 1907. ;
Cruciform tail : The horizontal stabilisers are placed midway up the vertical stabiliser, giving the appearance of a
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. Examples include the
Hawker Sea Hawk and
Douglas A-4 Skyhawk. ;
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, and are more efficient on low-speed aircraft. However, the T-tail has several disadvantages. It is more likely to enter a
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. A T-tail must be stronger, and therefore heavier than a conventional tail. T-tails also tend to have a larger
radar cross section. Examples include the
Gloster Javelin and
McDonnell Douglas DC-9.
Fins The fin comprises the fixed vertical stabiliser and rudder. Besides its
profile, 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 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,
B-25 Mitchell,
Avro Lancaster, and
ERCO Ercoupe. •
Twin boom 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,
P-38 Lightning,
de Havilland Sea Vixen,
Sadler Vampire, and
Edgley Optica. •
Wing mounted midwing as on the
F7U Cutlass or on the wing tips as on the
Handley Page Manx and
Rutan Long-EZ Unusual fin configurations include: •
No fin – as on the
McDonnell Douglas X-36. This configuration is sometimes incorrectly referred to as "tailless". •
Multiple fins – examples include the
Lockheed Constellation (three),
Bellanca 14-13 (three), and the
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 and
Dornier Do 335).
V, Y and X tails An alternative to the fin-and-tailplane approach is provided by the
V-tail and
X-tail 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, act differentially to provide yaw control (in place of the rudder) and act together to provide pitch control (in place of the elevator). The configuration was first developed during World War II by
Richard Vogt and George Haag at
Blohm & Voss. The
Skoda-Kauba SL6 tested the proposed control system in 1944 and, following several design proposals, an order was received for the
Blohm & Voss P 215 just weeks before the war ended. The outboard tail reappeared on the
Scaled Composites SpaceShipOne in 2003 and
SpaceShipTwo in 2010.
Tailless aircraft 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 either tailplane or
canard foreplane (nor does it have a second wing in
tandem arrangement). A "tailless" type usually still has a vertical stabilising fin (
vertical stabiliser) and control surface (
rudder). However,
NASA adopted the "tailless" description for the novel
X-36 research aircraft which has a canard foreplane but no vertical fin. == See also ==