![F-16 3 Yokota Tokyo](https://upload.wikimedia.org/wikipedia/commons/e/ec/F-16_3_Yokota_Tokyo.jpg)
A stabilator is a fully movable aircraft horizontal
stabilizer. It serves the usual functions of longitudinal stability, control and stick force requirements otherwise performed by the separate parts of a conventional
horizontal stabilizer
A tailplane, also known as a horizontal stabiliser, is a small lifting surface located on the tail (empennage) behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixed-wing aircraft such as helicopters and gyroplan ...
and
elevator
An elevator or lift is a wire rope, cable-assisted, hydraulic cylinder-assisted, or roller-track assisted machine that vertically transports people or freight between floors, levels, or deck (building), decks of a building, watercraft, ...
. Apart from reduced drag, particularly at high Mach numbers,
it is a useful device for changing the aircraft balance within wide limits, and for reducing stick forces.
Stabilator is a
portmanteau
A portmanteau word, or portmanteau (, ) is a blend of words[tailplane
A tailplane, also known as a horizontal stabiliser, is a small lifting surface located on the tail (empennage) behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixed-wing aircraft such as helicopters and gyroplane ...](_blank)
, all-movable tail(plane), all-moving stabilizer, all-flying tail(plane), all-flying horizontal tail, full-flying stabilizer, and slab tailplane.
General aviation
![piper](https://upload.wikimedia.org/wikipedia/commons/8/87/Piper.cherokee.pa-28-140.g-bcgj.arp.jpg)
Because it involves a moving balanced surface, a stabilator can allow the pilot to generate a given pitching moment with a lower control force. Due to the high forces involved in tail balancing loads, stabilators are designed to pivot about their
aerodynamic center
In aerodynamics, the torques or moments acting on an airfoil moving through a fluid can be accounted for by the net lift and net drag applied at some point on the airfoil, and a separate net pitching moment about that point whose magnit ...
(near the tail's mean quarter-chord). This is the point at which the pitching moment is constant regardless of the angle of attack, and thus any movement of the stabilator can be made without added pilot effort. However, to be certified by the appropriate regulatory agency, an airplane must show an increasing resistance to an increasing pilot input (movement). To provide this resistance, stabilators on small aircraft contain an
anti-servo tab
__NOTOC__
A servo tab is a small hinged device installed on an aircraft control surface to assist the movement of the control surfaces. Introduced by the German firm Flettner, servo tabs were formerly known as Flettner tabs. Servo tabs are not ...
(usually acting also as a
trim tab
Trim tabs are small surfaces connected to the trailing edge of a larger control surface on a boat or aircraft, used to control the trim of the controls, i.e. to counteract hydro- or aerodynamic forces and stabilise the boat or aircraft in a pa ...
) that deflects in the same direction as the stabilator,
thus providing an aerodynamic force resisting the pilot's input. General aviation aircraft with stabilators include the
Piper Cherokee
The Piper PA-28 Cherokee is a family of two-seat or four-seat light aircraft built by Piper Aircraft and designed for flight training, air taxi and personal use.Plane and Pilot: ''1978 Aircraft Directory'', pages 62–64. Werner & Werner Corp, ...
and the
Cessna 177. The
Glaser-Dirks DG-100
The Glaser-Dirks DG-100 is the first sailplane manufactured by DG Flugzeugbau GmbH, Glaser-Dirks. It is a Glider competition classes, standard class glider designed by Wilhelm Dirks in 1974 and developed from the Akaflieg Darmstadt D-38.
Develop ...
glider initially used a stabilator without an anti-servo tab to increase resistance: as a result, the pitch movement of the glider is very sensitive. Later models used a conventional stabilizer and elevator.
Military
![Transonic flow patterns](https://upload.wikimedia.org/wikipedia/commons/6/6d/Transonic_flow_patterns.svg)
All-flying tailplanes were used on many pioneer aircraft and the popular
Morane-Saulnier G
The Morane-Saulnier G was a two-seat sport and racing monoplane produced in France before the First World War.Taylor 1989, 648"The Illustrated Encyclopedia of Aircraft", 2539 It was a development of the racing monoplanes designed by Léon Morane a ...
,
H and
L monoplanes from France as well as the early
Fokker Eindecker
The Fokker ''Eindecker'' fighters were a series of German World War I monoplane single-seat fighter aircraft designed by Dutch engineer Anthony Fokker.Boyne 1988 Developed in April 1915, the first ''Eindecker'' ("Monoplane") was the first purpose- ...
monoplane and
Halberstadt D.II biplane fighters from Germany all flew with them, although at the cost of
stability
Stability may refer to:
Mathematics
*Stability theory, the study of the stability of solutions to differential equations and dynamical systems
** Asymptotic stability
** Linear stability
** Lyapunov stability
** Orbital stability
** Structural sta ...
: none of these aircraft, with the possible exception of the biplane Halberstadts, could be flown hands-off.
Stabilators were developed to achieve adequate
pitch control in supersonic flight, and are almost universal on modern military
combat aircraft
A military aircraft is any fixed-wing or rotary-wing aircraft that is operated by a legal or insurrectionary armed service of any type. Military aircraft can be either combat or non-combat:
* Combat aircraft are designed to destroy enemy equipm ...
.
All non-
delta-wing
A delta wing is a wing shaped in the form of a triangle. It is named for its similarity in shape to the Greek uppercase letter delta (Δ).
Although long studied, it did not find significant applications until the Jet Age, when it proved suitab ...
ed supersonic aircraft use stabilators because with conventional control surfaces,
shock wave
In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a med ...
s can form past the elevator hinge, causing severe
mach tuck
Mach tuck is an aerodynamic effect whereby the nose of an aircraft tends to pitch downward as the airflow around the wing reaches supersonic speeds. This diving tendency is also known as tuck under. The aircraft will first experience this effect ...
.
The British wartime
Miles M.52
The Miles M.52 was a turbojet-powered supersonic research aircraft project designed in the United Kingdom in the mid-1940s. In October 1943, Miles Aircraft was issued with a contract to produce the aircraft in accordance with Air Ministry Sp ...
supersonic project was designed with stabilators. Though the design only flew as a scale rocket, its all-flying tail was tested on the
Miles Falcon
The mile, sometimes the international mile or statute mile to distinguish it from other miles, is a British imperial unit and United States customary unit of distance; both are based on the older English unit of length equal to 5,280 English ...
. The contemporary American supersonic project, the
Bell X-1
The Bell X-1 (Bell Model 44) is a rocket engine–powered aircraft, designated originally as the XS-1, and was a joint National Advisory Committee for Aeronautics– U.S. Army Air Forces–U.S. Air Force supersonic research project built by Be ...
, adapted its variable incidence tailplane into an all-moving tailplane (based on the Miles M.52 project data) and was operated successfully in 1947.
Entering service in 1951, the
Boeing B-47 Stratojet
The Boeing B-47 Stratojet (Boeing company designation Model 450) is a retired American long-range, six-engined, turbojet-powered strategic bomber designed to fly at high subsonic speed and at high altitude to avoid enemy interceptor aircraft ...
was the world's first purposely built jet bomber to include one piece stabilator design. A stabilator was considered for the
Boeing B-52 Stratofortress
The Boeing B-52 Stratofortress is an American long-range, subsonic, jet-powered strategic bomber. The B-52 was designed and built by Boeing, which has continued to provide support and upgrades. It has been operated by the United States Air ...
but rejected due to the unreliability of hydraulics at the time.
The
North American F-86 Sabre
The North American F-86 Sabre, sometimes called the Sabrejet, is a transonic jet fighter aircraft. Produced by North American Aviation, the Sabre is best known as the United States' first swept-wing fighter that could counter the swept-wing So ...
, the first U.S. Air Force aircraft which could go supersonic (although in a shallow dive) was introduced with a conventional horizontal stabilizer with elevators, which was eventually replaced with a stabilator.
When stabilators can move differentially to perform the
roll
Roll or Rolls may refer to:
Movement about the longitudinal axis
* Roll angle (or roll rotation), one of the 3 angular degrees of freedom of any stiff body (for example a vehicle), describing motion about the longitudinal axis
** Roll (aviation), ...
control function of
ailerons
An aileron (French for "little wing" or "fin") is a hinged flight control surface usually forming part of the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in Flight dynamics, roll (or ...
, as they do on many modern
fighter aircraft
Fighter aircraft are fixed-wing military aircraft designed primarily for air-to-air combat. In military conflict, the role of fighter aircraft is to establish air superiority of the battlespace. Domination of the airspace above a battlefield ...
they are known as tailerons or rolling tails. A
canard surface, looking like a stabilator but not stabilizing like a tailplane, can also be mounted in front of the main
wing
A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is expres ...
in a canard configuration (
Curtiss-Wright XP-55 Ascender
The Curtiss-Wright XP-55 Ascender (company designation CW-24) is a 1940s United States prototype fighter aircraft built by Curtiss-Wright. Along with the Vultee XP-54 and Northrop XP-56, it resulted from United States Army Air Corps proposal ...
).
Stabilators on military aircraft have the same problem of too light control forces (inducing overcontrol) as general aviation aircraft. Unlike light aircraft, supersonic aircraft are not fitted with anti-servo tabs, which would add unacceptable drag. In older jet fighter aircraft, a resisting force was generated within the control system, either by springs or a resisting hydraulic force, rather than by an external anti-servo tab. For example, in the
North American F-100 Super Sabre
The North American F-100 Super Sabre is an American supersonic jet fighter aircraft that served with the United States Air Force (USAF) from 1954 to 1971 and with the Air National Guard (ANG) until 1979. The first of the Century Series of ...
, springs were attached to the control stick to provide increasing resistance to pilot input. In modern fighters, control inputs are moderated by computers ("
fly by wire"), and there is no direct connection between the pilot's stick and the stabilator.
Airliners
![Trimmable horizontal stabiliser](https://upload.wikimedia.org/wikipedia/commons/c/c1/Trimmable_horizontal_stabiliser.JPG)
Most modern airliners do not have a stabilator. Instead they have an
adjustable horizontal stabilizer, and a separate elevator control. The movable horizontal stabilizer is adjusted to keep the pitch axis in
trim
Trim or TRIM may refer to:
Cutting
* Cutting or trimming small pieces off something to remove them
** Book trimming, a stage of the publishing process
** Pruning, trimming as a form of pruning often used on trees
Decoration
* Trim (sewing), or ...
during flight as the speed changes, or as fuel is burned and the
center of gravity
In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weight function, weighted relative position (vector), position of the distributed mass sums to zero. Thi ...
moves. These adjustments are commanded by the autopilot when it is engaged, or by the human pilot if the plane is being flown manually. Adjustable stabilizers are not the same as stabilators: a stabilator is controlled by the pilot's control yoke (or stick), whereas an adjustable stabilizer is controlled by the trim system.
In the
Boeing 737
The Boeing 737 is a narrow-body aircraft produced by Boeing at its Renton Factory in Washington.
Developed to supplement the Boeing 727 on short and thin routes, the twinjet retains the 707 fuselage width and six abreast seating with two un ...
, the adjustable stabilizer trim system is powered by an electrically operated
jackscrew
A jackscrew, or screw jack, is a type of jack that is operated by turning a leadscrew. It is commonly used to lift moderately and heavy weights, such as vehicles; to raise and lower the horizontal stabilizers of aircraft; and as adjustable suppo ...
.
One example of an airliner with a genuine stabilator used for flight control is the
Lockheed L-1011
The Lockheed L-1011 TriStar, also known as the L-1011 (pronounced "El-ten-eleven") and TriStar, is an American medium-to-long-range, wide-body trijet airliner built by the Lockheed Corporation. It was the third wide-body airliner to enter comme ...
.
References
External links
Stabilators (NASA)– Includes Java applet
{{Aircraft components
Aerodynamics
Aircraft controls
Aircraft wing design
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