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General Dynamics F-16 Fighting Falcon jet fighter parked at an airshow, with stabilators deflected downwards F-16 3 Yokota Tokyo.jpg
General Dynamics F-16 Fighting Falcon jet fighter parked at an airshow, with stabilators deflected downwards

A stabilator is a fully movable aircraft horizontal stabilizer. It serves the usual functions of longitudinal stability, control and stick force requirements [1] otherwise performed by the separate parts of a conventional horizontal stabilizer (which is fixed) and elevator (which is adjustable). Apart from reduced drag, particularly at high Mach numbers, [2] it is a useful device for changing the aircraft balance within wide limits, and for reducing stick forces. [3]


Stabilator is a portmanteau of stabilizer and elevator. It is also known as an all-moving tailplane, all-movable tail(plane), all-moving stabilizer, all-flying tail(plane), all-flying horizontal tail, full-flying stabilizer, and slab tailplane. [2]

General aviation

Piper Cherokee with stabilator (and anti-servo tab) deflected upwards
Piper Cherokee with stabilator (and anti-servo tab) deflected upwards

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 (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).[ citation needed ] To provide this resistance, stabilators on small aircraft contain an anti-servo tab (usually acting also as a trim tab) that deflects in the same direction as the stabilator, [4] thus providing an aerodynamic force resisting the pilot's input. General aviation aircraft with stabilators include the Piper Cherokee [2] and the Cessna 177. The Glaser-Dirks DG-100 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.


In transonic flight shock waves form on the upper surface of the wing at a different point from the lower surface. As speed increases, the shock wave moves backwards over the wing. On conventional tails this high pressure causes the elevator to be deflected downwards. Transonic flow patterns.svg
In transonic flight shock waves form on the upper surface of the wing at a different point from the lower surface. As speed increases, the shock wave moves backwards over the wing. On conventional tails this high pressure causes the elevator to be deflected downwards.

All-flying tailplanes were used on many pioneer aircraft and the popular Morane-Saulnier G, H and L monoplanes from France as well as the early Fokker Eindecker monoplane and Halberstadt D.II biplane fighters from Germany all flew with them, although at the cost of stability: 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. [2] All[ citation needed ] non-delta-winged supersonic aircraft use stabilators because with conventional control surfaces, shock waves can form past the elevator hinge, causing severe mach tuck.

The British wartime Miles M.52 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. [5] The contemporary American supersonic project, the Bell X-1, adapted its variable incidence tailplane into an all-moving tailplane (based on the Miles M.52 project data) and was operated successfully in 1947. [6]

Entering service in 1951, the Boeing B-47 Stratojet 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 but rejected due to the unreliability of hydraulics at the time. [2]

The North American F-86 Sabre, 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 control function of ailerons, as they do on many modern fighter aircraft they are known as tailerons or rolling tails. A canard surface, looking like a stabilator but not stabilizing like a tailplane, [7] can also be mounted in front of the main wing in a canard configuration (Curtiss-Wright XP-55 Ascender).

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, springs were attached to the control stick to provide increasing resistance to pilot input.[ citation needed ] 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.


Adjustable stabilizer on an Embraer E170, with markings showing the degree of nose-up and nose-down trim available Trimmable horizontal stabiliser.JPG
Adjustable stabilizer on an Embraer E170, with markings showing the degree of nose-up and nose-down trim available

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 during flight as the speed changes, or as fuel is burned and the center of gravity 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 adjustable stabilizer trim system is powered by an electrically operated jackscrew. [8]

One example of an airliner with a genuine stabilator used for flight control is the Lockheed L-1011.

Related Research Articles

<span class="mw-page-title-main">Tailplane</span> Small lifting surface of a fixed-wing aircraft

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 gyroplanes. Not all fixed-wing aircraft have tailplanes. Canards, tailless and flying wing aircraft have no separate tailplane, while in V-tail aircraft the vertical stabiliser, rudder, and the tail-plane and elevator are combined to form two diagonal surfaces in a V layout.

<span class="mw-page-title-main">T-tail</span> Aircraft empennage configuration

A T-tail is an empennage configuration in which the tailplane is mounted to the top of the fin. The arrangement looks like the capital letter T, hence the name. The T-tail differs from the standard configuration in which the tailplane is mounted to the fuselage at the base of the fin.

<span class="mw-page-title-main">Flight control surfaces</span> Surface that allows a pilot to adjust and control an aircrafts flight attitude

Aircraft flight control surfaces are aerodynamic devices allowing a pilot to adjust and control the aircraft's flight attitude.

<span class="mw-page-title-main">Elevon</span>

Elevons or tailerons are aircraft control surfaces that combine the functions of the elevator and the aileron, hence the name. They are frequently used on tailless aircraft such as flying wings. An elevon that is not part of the main wing, but instead is a separate tail surface, is a stabilator.

<span class="mw-page-title-main">Aircraft flight control system</span> How aircraft are controlled

A conventional fixed-wing aircraft flight control system (AFCS) consists of flight control surfaces, the respective cockpit controls, connecting linkages, and the necessary operating mechanisms to control an aircraft's direction in flight. Aircraft engine controls are also considered as flight controls as they change speed.

<span class="mw-page-title-main">Elevator (aeronautics)</span> Aircraft control surface used to control pitch

Elevators are flight control surfaces, usually at the rear of an aircraft, which control the aircraft's pitch, and therefore the angle of attack and the lift of the wing. The elevators are usually hinged to the tailplane or horizontal stabilizer. They may be the only pitch control surface present, and are sometimes located at the front of the aircraft or integrated into a rear "all-moving tailplane", also called a slab elevator or stabilator.

<span class="mw-page-title-main">Empennage</span> Tail section of an aircraft containing stabilizers

The empennage, 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. The term derives from the French language verb empenner which means "to feather an arrow". Most aircraft feature an empennage incorporating vertical and horizontal stabilising surfaces which stabilise the flight dynamics of yaw and pitch, as well as housing control surfaces.

Aircraft flight mechanics are relevant to fixed wing and rotary wing (helicopters) aircraft. An aeroplane, is defined in ICAO Document 9110 as, "a power-driven heavier than air aircraft, deriving its lift chiefly from aerodynamic reactions on surface which remain fixed under given conditions of flight".

The United States Air Force Stability and Control Digital DATCOM is a computer program that implements the methods contained in the USAF Stability and Control DATCOM to calculate the static stability, control and dynamic derivative characteristics of fixed-wing aircraft. Digital DATCOM requires an input file containing a geometric description of an aircraft, and outputs its corresponding dimensionless stability derivatives according to the specified flight conditions. The values obtained can be used to calculate meaningful aspects of flight dynamics.

<span class="mw-page-title-main">Trim tab</span> Boat or aircraft component

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 particular desired attitude without the need for the operator to constantly apply a control force. This is done by adjusting the angle of the tab relative to the larger surface.

<span class="mw-page-title-main">Servo tab</span> Device on aircraft control surface

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 true servomechanisms, as they do not employ negative feedback to keep the control surfaces in a desired position; they only provide a mechanical advantage to the pilot.

<span class="mw-page-title-main">Vertical stabilizer</span> Aircraft component

A vertical stabilizer or tail fin is the static part of the vertical tail of an aircraft. The term is commonly applied to the assembly of both this fixed surface and one or more movable rudders hinged to it. Their role is to provide control, stability and trim in yaw. It is part of the aircraft empennage, specifically of its stabilizers.

<span class="mw-page-title-main">Mach tuck</span> Aerodynamic effect

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 at significantly below Mach 1.

<span class="mw-page-title-main">Stabilizer (aeronautics)</span> Aircraft component

An aircraft stabilizer is an aerodynamic surface, typically including one or more movable control surfaces, that provides longitudinal (pitch) and/or directional (yaw) stability and control. A stabilizer can feature a fixed or adjustable structure on which any movable control surfaces are hinged, or it can itself be a fully movable surface such as a stabilator. Depending on the context, "stabilizer" may sometimes describe only the front part of the overall surface.

<span class="mw-page-title-main">Canard (aeronautics)</span> Aircraft configuration in which a small wing is placed in front of the main wing

In aeronautics, a canard is a wing configuration in which a small forewing or foreplane is placed forward of the main wing of a fixed-wing aircraft or a weapon. The term "canard" may be used to describe the aircraft itself, the wing configuration, or the foreplane. Canard wings are also extensively used in guided missiles and smart bombs.

<span class="mw-page-title-main">Tailless aircraft</span> Aircraft whose only horizontal aerodynamic surface is its main wing

In aeronautics, a tailless aircraft is an aircraft with no other horizontal aerodynamic surface besides its main wing. It may still have a fuselage, vertical tail fin, and/or vertical rudder.

In flight dynamics, longitudinal stability is the stability of an aircraft in the longitudinal, or pitching, plane. This characteristic is important in determining whether an aircraft pilot will be able to control the aircraft in the pitching plane without requiring excessive attention or excessive strength.

<span class="mw-page-title-main">Three-surface aircraft</span> Fixed-wing aircraft with a main central wing plus fore and aft surfaces

A three-surface aircraft or sometimes three-lifting-surface aircraft has a foreplane, a central wing and a tailplane. The central wing surface always provides lift and is usually the largest, while the functions of the fore and aft planes may vary between types and may include lift, control and/or stability.

<span class="mw-page-title-main">Outboard tail</span>

An outboard tail is a type of aircraft tail or empennage which 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). OHS designs are sometimes described as a form of tailless aircraft.

<span class="mw-page-title-main">Trim drag</span> Component of aerodynamic drag on aircraft

Trim drag, denoted as Dm in the diagram, is the component of aerodynamic drag on an aircraft created by the flight control surfaces, mainly elevators and trimable horizontal stabilizers, when they are used to offset changes in pitching moment and centre of gravity during flight. For longitudinal stability in pitch and in speed, aircraft are designed in such a way that the centre of mass is forward of the neutral point. The nose-down pitching moment is compensated by the downward aerodynamic force on the elevator and the trimable horizontal stabilizer. This downwards force on the tailplane produces lift–induced drag in a similar way as the lift on the wing produces lift–induced drag. The changes (shifts) of the position of the centre of mass are often caused by fuel being burned off over the period of the flight, and require the aerodynamic trim force to be adjusted. Systems that actively pump fuel between separate fuel tanks in the aircraft can be used to offset this effect and reduce the trim drag.


  1. Roskam, Airplane Design, part III, Empennage layout, Longitudinal considerations
  2. 1 2 3 4 5 Abzug, Malcolm J.; Larrabee, E. Eugene (23 September 2002). Airplane Stability and Control: A History of the Technologies that Made Aviation Possible. Cambridge University Press. p. 78. ISBN   978-1-107-32019-2 . Retrieved 17 October 2022. All-movable tail surfaces became interesting... when high Mach number theory and transonic wind-tunnel tests disclosed poor performance of ordinary flap-type controls.
  3. Daroll Stinton, The design of the aeroplane, Control surfaces, p. 447 and 449 : "...for variation of tab size, gear ratio and stabilator pivot position, the stick-free neutral point can be varied almost at will.
  4. Phillips, William Hewitt (November 1998). "6. Problems Encountered as a Result of Wartime Developments". Journey in Aeronautical Research: A Career at NASA Langley Research Center. NASA History Office. Retrieved 17 October 2022. the tab on the all-movable tail was changed from a servo tab to a geared unbalancing tab. With this arrangement, the control forces were similar to those on a conventional airplane
  5. Brown, Eric. Wings on my Sleeve. London: Weidenfeld & Nicolson, 2006. ISBN   978-0-297-84565-2.
  6. Miller, Jay. The X-Planes: X-1 to X-45. Hinckley, UK: Midland, 2001. ISBN   1-85780-109-1.
  7. Hoerner, Fluid dynamic lift, about XP-55, p. 11-29, Stability Contributions : "Stabilization in any canard configuration can only be obtained from the wing."
  8. Federal Register. Office of the Federal Register, National Archives and Records Service, General Services Administration. July 1978. p. 32404. Retrieved 18 October 2022.