Elevator (aeronautics)

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Elevators' effect on pitch Aileron pitch.gif
Elevators' effect on pitch
Elevator and pitch trim tab of a light aircraft Light aircraft elevator and trim tab.JPG
Elevator and pitch trim tab of a light aircraft

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 (early airplanes) or integrated into a rear "all-moving tailplane", also called a slab elevator or stabilator.


Elevator control effectiveness

The elevator is a usable up and down system that controls the plane, horizontal stabilizer usually creates a downward force which balances the nose down moment created by the wing lift force, which typically applies at a point (the wing center of lift) situated aft of the airplane's center of gravity. The effects of drag and changing the engine thrust may also result in pitch moments that need to be compensated with the horizontal stabilizer.

Both the horizontal stabilizer and the elevator contribute to pitch stability, but only the elevators provide pitch control. [1] They do so by decreasing or increasing the downward force created by the stabilizer:

On many low-speed aircraft, a trim tab is present at the rear of the elevator, which the pilot can adjust to eliminate forces on the control column at the desired attitude and airspeed. [2] Supersonic aircraft usually have all-moving tailplanes (stabilators), because shock waves generated on the horizontal stabilizer greatly reduce the effectiveness of hinged elevators during supersonic flight. Delta winged aircraft combine ailerons and elevators and their respective control inputs into one control surface called an elevon.

Elevators' location

Elevators are usually part of the tail, at the rear of an aircraft. In some aircraft, pitch-control surfaces are in the front, ahead of the wing. In a two-surface aircraft this type of configuration is called a canard (the French word for duck) or a tandem wing. The Wright Brothers' early aircraft were of the canard type; Mignet Pou-du-Ciel and Rutan Quickie are of tandem type. Some early three surface aircraft had front elevators (Curtiss/AEA June Bug); modern three surface aircraft may have both front (canard) and rear elevators (Grumman X-29).


Several technology research and development efforts exist to integrate the functions of aircraft flight control systems such as ailerons, elevators, elevons, flaps and flaperons into wings to perform the aerodynamic purpose with the advantages of less: mass, cost, drag, inertia (for faster, stronger control response), complexity (mechanically simpler, fewer moving parts or surfaces, less maintenance), and radar cross section for stealth. These may be used in many unmanned aerial vehicles (UAVs) and 6th generation fighter aircraft. Two promising approaches are flexible wings, and fluidics.

In flexible wings, much or all of a wing surface can change shape in flight to deflect air flow. The X-53 Active Aeroelastic Wing is a NASA effort. The Adaptive Compliant Wing is a military and commercial effort. [3] [4] [5]

In fluidics, forces in vehicles occur via circulation control, in which larger more complex mechanical parts are replaced by smaller simpler fluidic systems (slots which emit air flows) where larger forces in fluids are diverted by smaller jets or flows of fluid intermittently, to change the direction of vehicles. [6] [7] [8] In this use, fluidics promises lower mass, costs (up to 50% less), and very low inertia and response times, and simplicity.

See also

Related Research Articles

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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">Aileron</span> Aircraft control surface used to induce roll

An aileron 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 roll, which normally results in a change in flight path due to the tilting of the lift vector. Movement around this axis is called 'rolling' or 'banking'.

<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

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

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 and elevator. 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.

<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".

<span class="mw-page-title-main">Wing warping</span> Early system for lateral control of a fixed-wing aircraft

Wing warping was an early system for lateral (roll) control of a fixed-wing aircraft. The technique, used and patented by the Wright brothers, consisted of a system of pulleys and cables to twist the trailing edges of the wings in opposite directions. In many respects, this approach is similar to that used to trim the performance of a paper airplane by curling the paper at the back of its wings.

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

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<span class="mw-page-title-main">Flaperon</span> Type of aircraft control surface that combines the functions of both flaps and ailerons

A flaperon on an aircraft's wing is a type of control surface that combines the functions of both flaps and ailerons. Some smaller kitplanes have flaperons for reasons of simplicity of manufacture, while some large commercial aircraft such as the Boeing 747, 767, 777, and 787 may have a flaperon between the flaps and aileron. The 787 has a configuration known as a SpoileFlaperon that combines the action of spoilers, flaps and ailerons into one control surface.

<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.

In aeronautics, spoilerons are spoilers that can be used asymmetrically as flight control surfaces to provide roll control.

<span class="mw-page-title-main">Trailing edge</span> Rear edge of an aerodynamic surface

The trailing edge of an aerodynamic surface such as a wing is its rear edge, where the airflow separated by the leading edge meets. Essential flight control surfaces are attached here to control the direction of the departing air flow, and exert a controlling force on the aircraft. Such control surfaces include ailerons on the wings for roll control, elevators on the tailplane controlling pitch, and the rudder on the fin controlling yaw. Elevators and ailerons may be combined as elevons on tailless aircraft.

<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">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.


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