Empennage
In spite of effective control surfaces, many early aircraft that lacked a stabilising empennage were virtually unflyable. Even so-called "
Structure
Structurally, the empennage consists of the entire tail assembly, including the
The front (usually fixed) section of the
The
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.[5]
The aircraft's
Trim
In some aircraft
The trim device may be:
- a 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.[5][7]
- an
- a bungee trim system which uses a spring to provide an adjustable preload in the controls. Usually controlled by a cockpit lever.[5][6]
- an 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.[5]
- a 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.[5]
Multi-engined aircraft often have trim tabs on the rudder to reduce the pilot effort required to keep the aircraft straight in situations of asymmetrical thrust, such as single engine operations.[7]
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:
- Configuration – 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".[9] (General Dynamics F-111 Aardvark)
Some locations have been given special names:
- 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.
- 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. Examples include the Gloster Javelin and McDonnell Douglas DC-9.
Fuselage mounted |
Cruciform |
T-tail |
Flying tailplane |
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:
- B-25 Mitchell, Avro Lancaster, and ERCO Ercoupe.
- .
- Wing mounted midwing as on the F7U Cutlass or on the wing tips as on the Handley Page Manx and Rutan Long-EZ
Tailplane mounted |
Twin tail boom |
Wing mounted |
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).
Triple fins |
Ventral fin |
V, Y and X tails
An alternative to the fin-and-tailplane approach is provided by the
- V tail: A V-tail can be lighter than a conventional tail in some situations and produce less drag, as on the X-37 spacecraft. A V-tail may also have a smaller radar signature. Other aircraft featuring a V-tail include the Beechcraft Model 35 Bonanza, and Davis DA-2. A slight modification to the V-tail can be found on the Waiex and Monnett Monicalled a Y-tail.
- Inverted V tail:The unmanned Lazair and Mini-IMP.
- Y tail: A V-tail with an added lower vertical fin (generally used to protect an aft propeller), as LearAvia Lear Fan
- X tail: The Lockheed XFV featured 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
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 stabilizers (OHS) and may or may not include additional boom-mounted vertical stabilizers (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
Tailless aircraft
A tailless aircraft (often tail-less) traditionally has all its horizontal control surfaces on its main wing surface. It has no
The most successful tailless configuration has been the tailless delta, especially for combat aircraft.[citation needed]
See also
References
- ^ ISBN 1-56027-287-2
- ^ ISBN 0-9690054-9-0
- Air Transport Association (November 10, 2011). "ATA Airline Handbook Chapter 5: How Aircraft Fly". Archived from the originalon November 10, 2011. Retrieved March 5, 2013.
- ^ "Empennage". Oxford Dictionaries Online. Oxford Dictionaries. Archived from the original on July 22, 2012. Retrieved March 5, 2013.
- ^ ISBN 0-9690054-9-0
- ^ a b Reichmann, Helmet: Flying Sailplanes, p. 26. Thompson Publications, 1980.
- ^ ISBN 0-7715-5115-0
- ISBN 1-56027-287-2
- ^ Anderson, John D., Introduction to Flight, 5th ed, p. 517
- ^ Ralph D. Kimberlin, Flight Testing of Fixed Wing Aircraft, AIAA 2003, p.380.
- ^ Kurt W. Muller; "Analysis of a Semi-Tailless Aircraft Design" (Master's thesis), Naval Postgraduate School, US, 2002.[1] Archived November 23, 2022, at the Wayback Machine
- ^ Zdenek Titz and Jaroslav Zazvonil; "Kauba's Dwarfs", Flying Review International, Nov 1965, pp.169-172.
- ISBN 3-87943-624-X.
- ^ Benjamin Darrenougue; "Aircraft Configurations With Outboard Horizontal Stabilizers" (Final year project report), Queens University Belfast, 14 May 2004.[2]