A tailplane known as a horizontal stabiliser, is a small lifting surface located on the tail 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 and flying wing aircraft have no separate tailplane, while in V-tail aircraft the vertical stabilizer and the tail-plane and elevator are combined to form two diagonal surfaces in a V layout; the function of the tailplane is to provide control. In particular, the tailplane helps adjust for changes in position of the center of pressure or center of gravity caused by changes in speed and attitude, fuel consumption, or dropping cargo or payload; the tailplane comprises the tail-mounted fixed horizontal movable elevator. Besides its planform, it is characterised by: Number of tailplanes - from 0 to 3 Location of tailplane - mounted high, mid or low on the fuselage, fin or tail booms. Fixed movable elevator surfaces, or a single combined stabilator or flying tail.
Some locations have been given special names: Cruciform: mid-mounted on the fin T-tail: high-mounted on the fin A wing with a conventional aerofoil profile makes a negative contribution to longitudinal stability. This means that any disturbance which raises the nose produces a nose-up pitching moment which tends to raise the nose further. With the same disturbance, the presence of a tailplane produces a restoring nose-down pitching moment, which may counteract the natural instability of the wing and make the aircraft longitudinally stable; the longitudinal stability of an aircraft may change when it is flown "hands-off". In addition to giving a restoring force a tailplane gives damping; this is caused by the relative wind seen by the tail as the aircraft rotates around the center of gravity. For example, when the aircraft is oscillating, but is momentarily aligned with the overall vehicle's motion, the tailplane still sees a relative wind, opposing the oscillation. Depending on the aircraft design and flight regime, its tailplane may create positive lift or negative lift.
It is sometimes assumed that on a stable aircraft this will always be a net down force, but this is untrue. On some pioneer designs, such as the Bleriot XI, the center of gravity was between the neutral point and the tailplane, which provided positive lift; however this arrangement can be unstable and these designs had severe handling issues. The requirements for stability were not understood until shortly before World War I - the era within which the British Bristol Scout light biplane was designed for civilian use, with an airfoiled lifting tail throughout its production run into the early World War I years and British military service from 1914-1916 — when it was realised that moving the center of gravity further forwards allowed the use of a non-lifting tailplane in which the lift is nominally neither positive nor negative but zero, which leads to more stable behaviour. Examples of aircraft from World War I and onwards into the interwar years that had positive lift tailplanes include, the Sopwith Camel, Charles Lindbergh's Spirit of St. Louis, the Gee Bee Model R Racer - all aircraft with a reputation for being difficult to fly, the easier-to-fly Fleet Finch two-seat Canadian trainer biplane, itself possessing a flat-bottom airfoiled tailplane unit not unlike the earlier Bristol Scout.
But with care a lifting tailplane can be made stable. An example is provided by the Bachem Ba 349 Natter VTOL rocket-powered interceptor, which had a lifting tail and was both stable and controllable in flight. In many modern conventional aircraft, the center of gravity is placed ahead of the neutral point; the wing lift exerts a pitch-down moment around the centre of gravity, which must be balanced by a pitch-up moment from the tailplane. A disadvantage is. Using a computer to control the elevator allows aerodynamically unstable aircraft to be flown in the same manner. Aircraft such as the F-16 are flown with artificial stability; the advantage of this is a significant reduction in drag caused by the tailplane, improved maneuverability. At transonic speeds, an aircraft can experience a shift rearwards in the center of pressure due to the buildup and movement of shockwaves; this causes. Significant trim force may be needed to maintain equilibrium, this is most provided using the whole tailplane in the form of an all-flying tailplane or stabilator.
A tailplane has some means allowing the pilot to control the amount of lift produced by the tailplane. This in turn causes a nose-up or nose-down pitching moment on the aircraft, used to control the aircraft in pitch. Elevator A conventional tailplane has a hinged aft surface called an elevator, Stabilator or all-moving tail In transonic flight shock waves generated by the front of the tailplane render any elevator unusable. An all-moving tail was developed by the British for the Miles M.52, but first saw actual transonic flight on the Bell X-1. This saved the program from a time-consuming rebuild of the aircraft. Transonic and supersonic aircraft now have all-moving tailplanes to counterac
An aircraft stabilizer is an aerodynamic surface including one or more movable control surfaces, that provides longitudinal and/or directional 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 movable surface such as a stabilator. Depending on the context, "stabilizer" may sometimes describe only the front part of the overall surface. In the conventional aircraft configuration, separate vertical and horizontal stabilizers form an empennage positioned at the tail of the aircraft. Other arrangements of the empennage, such as the V-tail configuration, feature stabilizers which contribute to a combination of longitudinal and directional stabilization and control. Longitudinal stability and control may be obtained with other wing configurations, including canard, tandem wing and tailless aircraft; some types of aircraft are stabilized with electronic flight control. A horizontal stabilizer is used to maintain the aircraft in longitudinal balance, or trim: it exerts a vertical force at a distance so the summation of pitch moments about the center of gravity is zero.
The vertical force exerted by the stabilizer varies with flight conditions, in particular according to the aircraft lift coefficient and wing flaps deflection which both affect the position of the center of pressure, with the position of the aircraft center of gravity. Transonic flight makes special demands on horizontal stabilizers. Another role of a horizontal stabilizer is to provide longitudinal static stability. Stability can be defined only; this maintains a constant aircraft attitude, with unchanging pitch angle relative to the airstream, without active input from the pilot. Ensuring static stability of an aircraft with a conventional wing requires that the aircraft center of gravity be ahead of the center of pressure, so a stabilizer positioned at the rear of the aircraft will produce lift in the downwards direction; the elevator serves to control the pitch axis. The upwash and downwash associated with the generation of lift is the source of aerodynamic interaction between the wing and stabilizer, which translates into a change in the effective angle of attack for each surface.
The influence of the wing on a tail is much more significant than the opposite effect and can be modeled using the Prandtl lifting-line theory. In the conventional configuration the horizontal stabilizer is a small horizontal tail or tailplane located to the rear of the aircraft; this is the most common configuration. On many aircraft, the tailplane assembly consists of a fixed surface fitted with a hinged aft elevator surface. Trim tabs may be used to relieve pilot input forces. Most airliners and transport aircraft feature a large, slow-moving trimmable tail plane, combined with independently-moving elevators; the elevators are controlled by the pilot or autopilot and serve to change the aircraft’s attitude, while the whole assembly is used to trim and stabilize the aircraft in the pitch axis. Many supersonic aircraft feature an all-moving tail assembly named stabilator, where the entire surface is adjustable. Variants on the conventional configuration include the T-tail, Cruciform tail, Twin tail and Twin-boom mounted tail.
Three-surface aircraft such as the Piaggio P.180 Avanti or the Scaled Composites Triumph and Catbird, the tailplane is a stabilizer as in conventional aircraft. Some earlier three-surface aircraft, such as the Curtiss AEA June Bug or the Voisin 1907 biplane, were of conventional layout with an additional front pitch control surface, called "elevator" or sometimes "stabilisateur". Lacking elevators, the tailplanes of these aircraft were not what is now called conventional stabilizers. For example, the Voisin was a tandem-lifting layout with a foreplane, neither stabilizing nor lifting. In the canard configuration, a small wing, or foreplane, is located in front of the main wing; some authors call it a stabilizer or give to the foreplane alone a stabilizing role, although as far as pitch stability is concerned, a foreplane is described as a destabilizing surface, the main wing providing the stabilizing moment in pitch. In unstable aircraft, the canard surfaces may be used as an active part of the artificial stability system, are sometimes named horizontal stabilizers.
Tailless aircraft lack a separate horizontal stabilizer. In a tailless aircraft, the horizontal stabilizing surface is part of the main wing. Longitudinal stability in tailless aircraft is achieved by designing the aircraft so that its aerodynamic center is behind the center of gravity; this is done by modifying the wing design, for example by varying the angle of incidence in the span-wise direction (wing washout or twist
In a fixed-wing aircraft, the spar is the main structural member of the wing, running spanwise at right angles to the fuselage. The spar carries the weight of the wings while on the ground. Other structural and forming members such as ribs may be attached to the spar or spars, with stressed skin construction sharing the loads where it is used. There may be more than one spar in a none at all. However, where a single spar carries the majority of the forces on it, it is known as the main spar. Spars are used in other aircraft aerofoil surfaces such as the tailplane and fin and serve a similar function, although the loads transmitted may be different from those of a wing spar; the wing spar provides the majority of the weight support and dynamic load integrity of cantilever monoplanes coupled with the strength of the wing'D' box itself. Together, these two structural components collectively provide the wing rigidity needed to enable the aircraft to fly safely. Biplanes employing flying wires have much of the flight loads transmitted through the wires and interplane struts enabling smaller section and thus lighter spars to be used at the cost of increasing drag.
Some of the forces acting on a wing spar are: Upward bending loads resulting from the wing lift force that supports the fuselage in flight. These forces are offset by carrying fuel in the wings or employing wing-tip-mounted fuel tanks. Downward bending loads while stationary on the ground due to the weight of the structure, fuel carried in the wings, wing-mounted engines if used. Drag loads dependent on airspeed and inertia. Rolling inertia loads. Chordwise twisting loads due to aerodynamic effects at high airspeeds associated with washout, the use of ailerons resulting in control reversal. Further twisting loads are induced by changes of thrust settings to underwing-mounted engines; the "D" box construction is beneficial to reduce wing twisting. Many of these loads are reversed abruptly in flight with an aircraft such as the Extra 300 when performing extreme aerobatic manoeuvers. Early aircraft used spars carved from solid spruce or ash. Several different wooden spar types have been used and experimented with such as spars that are box-section in form.
Wooden spars are still being used in light aircraft such as its relatives. A disadvantage of the wooden spar is the deteriorating effect that atmospheric conditions, both dry and wet, biological threats such as wood-boring insect infestation and fungal attack can have on the component. Wood wing spars of multipiece construction consist of upper and lower members, called spar caps, vertical sheet wood members, known as shear webs or more webs, that span the distance between the spar caps. In modern times, "homebuilt replica aircraft" such as the replica Spitfires use laminated wooden spars; these spars are laminated from spruce or douglas fir. A number of enthusiasts build "replica" Spitfires that will fly using a variety of engines relative to the size of the aircraft. A typical metal spar in a general aviation aircraft consists of a sheet aluminium spar web, with "L" or "T" -shaped spar caps being welded or riveted to the top and bottom of the sheet to prevent buckling under applied loads. Larger aircraft using this method of spar construction may have the spar caps sealed to provide integral fuel tanks.
Fatigue of metal wing spars has been an identified causal factor in aviation accidents in older aircraft as was the case with Chalk's Ocean Airways Flight 101. The German Junkers J. I armoured fuselage ground-attack sesquiplane of 1917 used a Hugo Junkers-designed multi-tube network of several tubular wing spars, placed just under the corrugated duralumin wing covering and with each tubular spar connected to the adjacent one with a space frame of triangulated duralumin strips — in the manner of a Warren truss layout — riveted onto the spars, resulting in a substantial increase in structural strength at a time when most other aircraft designs were built completely with wood-structure wings; the Junkers all-metal corrugated-covered wing / multiple tubular wing spar design format was emulated after World War I by American aviation designer William Stout for his 1920s-era Ford Trimotor airliner series, by Russian aerospace designer Andrei Tupolev for such aircraft as his Tupolev ANT-2 of 1922, upwards in size to the then-gigantic Maksim Gorki of 1934.
A design aspect of the Supermarine Spitfire wing that contributed to its success was an innovative spar boom design, made up of five square concentric tubes that fitted into each other. Two of these booms were linked together by an alloy web, creating a lightweight and strong main spar. A version of this spar construction method is used in the BD-5, designed and constructed by Jim Bede in the early 1970s; the spar used in the BD-5 and subsequent BD projects was aluminium tube of 2 inches in diameter, joined at the wing root with a much larger internal diameter aluminium tube to provide the wing structural integrity. In aircraft such as the Vickers Wellington, a geodesic wing spar structure was employed, which had the advantages of being lightweight and able to withstand heavy battle damage with only partial loss of strength. Many modern aircraft use carbon fibre and Kevlar in their construction, ranging in size from large airliners to small h
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 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. Servo tabs move in the opposite direction of the control surface; the tab has a leverage advantage, being located well aft of the surface hinge line, thus can use the relative airflow to deflect the control surface in the opposite direction. This has the effect of reducing the control force required by the pilot to move the controls. In the case of some large aircraft the servo tab is the only control, connected to the pilot's stick or wheel, as in the Bristol Britannia and its Canadian derivatives; the pilot moves the wheel which moves the servo tab and the servo tab, using its mechanical advantage, moves the elevator or aileron, otherwise free-floating. With a servo-tab variant named "geared spring tab", a pilot is able "to maneuver a vehicle weighing as much as 300,000 pounds flying at an airspeed of 300 miles per hour or more".
An anti-servo tab, or anti-balance tab, works in the opposite way to a servo tab. It deploys in the same direction as the control surface, making the movement of the control surface more difficult and requires more force applied to the controls by the pilot; this may seem counter-productive, but it is used on aircraft where the controls are too light or the aircraft requires additional stability in that axis of movement. The anti-servo tab serves to make the controls heavier in feel to the pilot and to increase stability. An anti-servo tab functions as a trim device to relieve control pressure and maintain the stabilator in the desired position. Trim tab The Quest for Reduced Control Forces — Monographs in Aerospace History: William Hewitt Phillips. A thorough dissertation on the reduction of control forces in high speed and large aircraft in the 1940s, with excellent links to NACA reports of the time, holding present day validity
Elevators are flight control surfaces at the rear of an aircraft, which control the aircraft's pitch, therefore the angle of attack and the lift of the wing. The elevators are hinged to the tailplane or horizontal stabilizer, they may be the only pitch control surface present, sometimes located at the front of the aircraft or integrated into a rear "all-moving tailplane" called a slab elevator or stabilator. The horizontal stabilizer creates a downward force which balances the nose down moment created by the wing lift force, which applies at a point situated aft of the airplane's center of gravity; the effects of drag and changing the engine thrust may 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, they do so by decreasing or increasing the downward force created by the stabilizer: an increased downward force, produced by up elevator, forces the tail down and the nose up.
At constant speed, the wing's increased angle of attack causes a greater lift to be produced by the wing, accelerating the aircraft upwards. The drag and power demand increase. At constant speed, the decrease in angle of attack reduces the lift, accelerating the aircraft downwards. 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. Supersonic aircraft have all-moving tailplanes, because shock waves generated on the horizontal stabilizer 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 are 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 tandem wing; the Wright Brothers' early aircraft were of the canard type.
Some early three surface aircraft had front elevators. Several technology research and development efforts exist to integrate the functions of aircraft flight control systems such as ailerons, elevons and flaperons into wings to perform the aerodynamic purpose with the advantages of less: mass, drag, inertia and radar cross section for stealth; these may be used in 6th generation fighter aircraft. Two promising approaches are flexible wings, 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 commercial effort. In fluidics, forces in vehicles occur via circulation control, in which larger more complex mechanical parts are replaced by smaller simpler fluidic systems where larger forces in fluids are diverted by smaller jets or flows of fluid intermittently, to change the direction of vehicles. In this use, fluidics promises lower mass and low inertia and response times, simplicity.
Rudder Aileron Aircraft Pitch Motion
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. The tailplane is kept well out of the disturbed airflow behind the wing and fuselage, giving smoother and faster airflow over the elevators; this configuration may give more predictable design better pitch control. Responsive pitch control is crucial for aircraft flying at low speed, to allow effective rotation on landing; this configuration allows high performance aerodynamics and an excellent glide ratio as the empennage is less affected by wing and fuselage slipstream. A T-tail has a better effective aspect ratio, less interaction drag than a cruciform tail, a more efficient vertical tail, the horizontal tail plate increasing the aspect ratio of the fin by virtue of the'end plate' effect, reducing turbulence and hence the induced drag of the fin.
The rudder will be more effective due to decreased induced drag. Therefore, the T-tail configuration is popular on gliders, where high performance is essential. A T tailed aircraft is easier to recover from a spin than aircraft with other types of empennage, as the elevator is located above the rudder, thus creating no dead air zone above the elevator where the rudder would be ineffective in spin conditions; the aircraft may be prone to suffering a dangerous deep stall condition, where a stalled wing at high angles of attack may blank the airflow over the tailplane and elevators, thereby leading to loss of pitch control. The American McDonnell F-101 Voodoo jet fighter suffered from this throughout its service life; the vertical stabilizer must be made stronger and stiffer to support the forces generated by the tailplane. The T-tail configuration can cause maintenance concerns; the control runs to the elevators are more complex, elevator surfaces are much more difficult to casually inspect from the ground.
The loss of Alaska Airlines Flight 261 was directly attributed to lax maintenance of the T-tail. In order to mitigate some of these drawbacks, a compromise is possible; the tailplane can be mounted part way up the fin rather than right at the top, known as a cruciform tail. The Sud Aviation Caravelle is an example of an aircraft with this configuration; the T-tail is common on aircraft with engines mounted in nacelles on a high-winged aircraft or on aircraft with the engines mounted on the rear of the fuselage, as it keeps the tail clear of the jet exhaust. These layouts are found in military transport aircraft - such as the Ilyushin Il-76, Airbus A400M and the Boeing C-17 Globemaster III - and regional airliners and business jets such as the Pilatus PC-12, Beechcraft Super King Air, Embraer ERJ, British Aerospace 146, Learjet and Gulfstream families, it is seen in combat aircraft, although the Gloster Javelin, McDonnell F-101 Voodoo, Lockheed F-104 Starfighter interceptors all sported T-tails.
Pelikan tail Twin tail V-tail "T-tails and top technology". Flight International. 13 Oct 1979
Air brake (aeronautics)
In aeronautics, air brakes or speed brakes are a type of flight control surfaces used on an aircraft to increase drag or increase the angle of approach during landing. Air brakes differ from spoilers in that air brakes are designed to increase drag while making little change to lift, whereas spoilers reduce the lift-to-drag ratio and require a higher angle of attack to maintain lift, resulting in a higher stall speed; the earliest known air brake was developed in 1931 and deployed on the wing support struts. Not long after, air brakes located on the bottom of the wing's trailing edge were developed and became the standard type of aircraft air brake for decades. In 1936, Hans Jacobs, who headed Nazi Germany's Deutsche Forschungsanstalt für Segelflug glider research organization before World War II, developed blade-style self-operating dive brakes, on the upper and lower surface of each wing, for gliders. Most early gliders were equipped with spoilers on the wings in order to adjust their angle of descent during approach to landing.
More modern gliders use air brakes which may spoil lift as well as increase drag, dependent on where they are positioned. Characteristics of both spoilers and air brakes are desirable and are combined - most modern airliner jets feature combined spoiler and air brake controls. On landing, the deployment of these spoilers causes a dramatic loss of lift and hence the weight of the aircraft is transferred from the wings to the undercarriage, allowing the wheels to be mechanically braked with much less chance of skidding. In addition, the form drag created by the spoilers directly assists the braking effect. Reverse thrust is used to help slow the aircraft after landing. All jet powered aircraft have an air brake or, in the case of most airliners, lift spoilers that act as air brakes. Propeller driven aircraft benefit from the natural braking effect of the propeller when the engine is throttled back, but jet powered aircraft have no such innate braking effect and must use air brakes to control descent speed.
Many early jets used parachutes as air brakes after landing. The Blackburn Buccaneer naval strike aircraft designed in the 1950s had a tail cone, split and could be hydraulically opened to the sides to act as a variable air brake, it helped to reduce the length of the aircraft in the confined space on an aircraft carrier. The F-15 Eagle, Sukhoi Su-27 and other fighters have an air brake just behind the cockpit. An air brake is a panel conforming the shape of an aircraft that can be opened with hydraulic pressure in order to create drag, similar to spoilers which are on the edges of the aircraft wings and open in an upward position forcing the plane towards the ground. Air brakes are used when the aircraft needs to reduce its airspeed, while spoilers are only able to be opened when the airplane is approaching the runway and about to touch down. Lift dumpers, a type of air brake, are mounted on the top of a fuselage; when the panel is opened, it acts as a small spoiler pushing the aircraft down.
Flaps increase drag and decrease airspeed, but are for reducing the stall speed, allowing the aircraft to land at a slower speed. Following the invention of powered flight, the rapid development of fixed-wing aircraft in the early 20th Century, man endeavoured for several decades to make airplanes faster than before. A universal goal for all manufacturers for some time, was to reach the speed of sound 740 miles per hour. Apart from the challenge of developing an engine capable of producing such a speed, preventing the aircraft from breaking apart under the stress, one major concern was how to keep the aircraft in stable flight and return it to a normal flying speed using a stronger braking system. In the 1930s, air brake systems were still using simple flaps that were manually controlled by a lever in the cockpit, with mechanical devices running through the wings. However, in order for the air brakes to be effective at 740 mph, they needed to be mounted on the fuselage for improved wing control, operated through some form of dampener or hydraulic system, allowing the pilot to physically pull a lever in order to create an excessive amount of air resistance.
The concept of fuselage-mounted air brakes, or speed brakes, spread throughout the 1930s becoming more commonplace in the 1940s. In the 1930s, pilots would land with the nose of the plane tilted upwards at a 45-degree angle for short landings in order to effect rapid deceleration. With this method, "the drag or resistance is increased by 300 percent, the distance required to land is cut down to one third of the usual stopping distance". However, there was an urgent need to develop an alternate way of drastically reducing speed on landing that would not cause the pilot to lose sight of what was ahead of him; this led to the development of a new air braking system with additional flaps, mounted on the wing, that opened in two directions simultaneously. This wing-mounted design allowed the effective surface area of the flaps to be increased by 100 percent for landing, producing more drag than the conceptual fuselage design and resulting in a sharper reduction in air speed; this meant that the pilot was able to see the landing strip in front of the aircraft as there was no longer the need to tilt the nose upwards at a steep angle at close to stalling speeds.
The rate of deceleration and foot pounds of force applied to each brake is dependent upon where the brake is located. Upper and lower surface flaps positioned along the wings provide the steadiest braking curve, but the flaps are subjected to greater stresses at theoretically hi