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49-475: The fundamentals of aircraft controls are explained in flight dynamics . This article centers on the operating mechanisms of the flight controls. The basic system in use on aircraft first appeared in a readily recognizable form as early as April 1908, on Louis Blériot 's Blériot VIII pioneer-era monoplane design. Generally, the primary cockpit flight controls are arranged as follows: The control yokes also vary greatly among aircraft. There are yokes where roll

98-420: A back-up electrical power supply that can be activated to enable the stick shaker in case of hydraulic failure. In most current systems the power is provided to the control actuators by high-pressure hydraulic systems. In fly-by-wire systems the valves, which control these systems, are activated by electrical signals. In power-by-wire systems, electrical actuators are used in favour of hydraulic pistons. The power

147-461: A control causes the mechanical circuit to open the matching servo valve in the hydraulic circuit. The hydraulic circuit powers the actuators which then move the control surfaces. As the actuator moves, the servo valve is closed by a mechanical feedback linkage - one that stops movement of the control surface at the desired position. This arrangement was found in the older-designed jet transports and in some high-performance aircraft. Examples include

196-478: A distance forward or aft of the cg, causing the aircraft to pitch up or down. A fixed-wing aircraft increases or decreases the lift generated by the wings when it pitches nose up or down by increasing or decreasing the angle of attack (AOA). The roll angle is also known as bank angle on a fixed-wing aircraft, which usually "banks" to change the horizontal direction of flight. An aircraft is streamlined from nose to tail to reduce drag making it advantageous to keep

245-472: A nominal straight and level flight path. To keep the analysis (relatively) simple, the control surfaces are assumed fixed throughout the motion, this is stick-fixed stability. Stick-free analysis requires the further complication of taking the motion of the control surfaces into account. Furthermore, the flight is assumed to take place in still air, and the aircraft is treated as a rigid body . Three forces act on an aircraft in flight: weight , thrust , and

294-501: A switch or a mechanical lever or in some cases are fully automatic by computer control, which alter the shape of the wing for improved control at the slower speeds used for take-off and landing. Other secondary flight control systems may include slats , spoilers , air brakes and variable-sweep wings . Mechanical or manually operated flight control systems are the most basic method of controlling an aircraft. They were used in early aircraft and are currently used in small aircraft where

343-402: A variety of forms, including: The various Euler angles relating the three reference frames are important to flight dynamics. Many Euler angle conventions exist, but all of the rotation sequences presented below use the z-y'-x" convention. This convention corresponds to a type of Tait-Bryan angles , which are commonly referred to as Euler angles. This convention is described in detail below for

392-703: A wing surface can change shape in flight to deflect air flow much like an ornithopter . Adaptive compliant wings are a military and commercial effort. The X-53 Active Aeroelastic Wing was a US Air Force, NASA , and Boeing effort. Notable efforts have also been made by FlexSys, who have conducted flight tests using flexible aerofoils retrofitted to a Gulf stream III aircraft. In active flow control systems, forces in vehicles occur via circulation control, in which larger and 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

441-450: Is a convenient frame to express the aerodynamic forces and moments acting on an aircraft. In particular, the net aerodynamic force can be divided into components along the wind frame axes, with the drag force in the − x w direction and the lift force in the − z w direction. In addition to defining the reference frames, the relative orientation of the reference frames can be determined. The relative orientation can be expressed in

490-436: Is a device for adjusting the tension or length of ropes , cables , tie rods , and other tensioning systems. It normally consists of two threaded eye bolts , one screwed into each end of a small metal frame, one with a conventional right-hand thread and the other with a left-hand thread. The tension can be adjusted by rotating the frame, which causes both eye bolts to be screwed in or out simultaneously, without twisting

539-478: Is carried to the actuators by electrical cables. These are lighter than hydraulic pipes, easier to install and maintain, and more reliable. Elements of the F-35 flight control system are power-by-wire. The actuators in such an electro-hydrostatic actuation (EHA) system are self-contained hydraulic devices, small closed-circuit hydraulic systems. The overall aim is towards more- or all-electric aircraft and an early example of

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588-537: Is controlled by rotating the yoke clockwise/counterclockwise (like steering a car) and pitch is controlled by moving the control column towards or away from the pilot, but in others the pitch is controlled by sliding the yoke into and out of the instrument panel (like most Cessnas, such as the 152 and 172), and in some the roll is controlled by sliding the whole yoke to the left and right (like the Cessna 162). Centre sticks also vary between aircraft. Some are directly connected to

637-496: Is known as wings level or zero bank angle. The most common aeronautical convention defines roll as acting about the longitudinal axis, positive with the starboard (right) wing down. Yaw is about the vertical body axis, positive with the nose to starboard. Pitch is about an axis perpendicular to the longitudinal plane of symmetry, positive nose up. Three right-handed , Cartesian coordinate systems see frequent use in flight dynamics. The first coordinate system has an origin fixed in

686-453: Is symmetric from right-to-left, the frames can be defined as: Asymmetric aircraft have analogous body-fixed frames, but different conventions must be used to choose the precise directions of the x and z axes. The Earth frame is a convenient frame to express aircraft translational and rotational kinematics. The Earth frame is also useful in that, under certain assumptions, it can be approximated as inertial. Additionally, one force acting on

735-627: The Antonov An-225 and the Lockheed SR-71 . With purely mechanical flight control systems, the aerodynamic forces on the control surfaces are transmitted through the mechanisms and are felt directly by the pilot, allowing tactile feedback of airspeed. With hydromechanical flight control systems, the load on the surfaces cannot be felt and there is a risk of overstressing the aircraft through excessive control surface movement. To overcome this problem, artificial feel systems can be used. For example, for

784-429: The aerodynamic force . The expression to calculate the aerodynamic force is: where: projected on wind axes we obtain: where: In absence of thermal effects, there are three remarkable dimensionless numbers: where: According to λ there are three possible rarefaction grades and their corresponding motions are called: The motion of a body through a flow is considered, in flight dynamics, as continuum current. In

833-439: The angle of attack of the body and Mach and Reynolds numbers . Aerodynamic efficiency, defined as the relation between lift and drag coefficients, will depend on those parameters as well. It is also possible to get the dependency of the drag coefficient respect to the lift coefficient . This relation is known as the drag coefficient equation: The aerodynamic efficiency has a maximum value, E max , respect to C L where

882-490: The angles of rotation in three dimensions about the vehicle's center of gravity (cg), known as pitch , roll and yaw . These are collectively known as aircraft attitude , often principally relative to the atmospheric frame in normal flight, but also relative to terrain during takeoff or landing, or when operating at low elevation. The concept of attitude is not specific to fixed-wing aircraft, but also extends to rotary aircraft such as helicopters, and dirigibles , where

931-405: The sideslip angle near zero, though an aircraft may be deliberately "sideslipped" to increase drag and descent rate during landing, to keep aircraft heading same as runway heading during cross-wind landings and during flight with asymmetric power. Roll, pitch and yaw refer to rotations about the respective axes starting from a defined steady flight equilibrium state. The equilibrium roll angle

980-452: The 1944 work Stick and Rudder . In some aircraft, the control surfaces are not manipulated with a linkage. In ultralight aircraft and motorized hang gliders, for example, there is no mechanism at all. Instead, the pilot just grabs the lifting surface by hand (using a rigid frame that hangs from its underside) and moves it. In addition to the primary flight controls for roll, pitch, and yaw, there are often secondary controls available to give

1029-558: The LTV A-7 Corsair II warplanes, a 'bob-weight' was used in the pitch axis of the control stick, giving force feedback that was proportional to the airplane's normal acceleration. A stick shaker is a device that is attached to the control column in some hydraulic aircraft. It shakes the control column when the aircraft is approaching stall conditions. Some aircraft such as the McDonnell Douglas DC-10 are equipped with

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1078-511: The aerodynamic forces are not excessive. Very early aircraft, such as the Wright Flyer I , Blériot XI and Fokker Eindecker used a system of wing warping where no conventionally hinged control surfaces were used on the wing, and sometimes not even for pitch control as on the Wright Flyer I and original versions of the 1909 Etrich Taube , which only had a hinged/pivoting rudder in addition to

1127-401: The aircraft will be configured differently, e.g. at low speed flaps may be deployed and the undercarriage may be down. Except for asymmetric designs (or symmetric designs at significant sideslip), the longitudinal equations of motion (involving pitch and lift forces) may be treated independently of the lateral motion (involving roll and yaw). The following considers perturbations about

1176-497: The aircraft, weight, is fixed in the + z E direction. The body frame is often of interest because the origin and the axes remain fixed relative to the aircraft. This means that the relative orientation of the Earth and body frames describes the aircraft attitude. Also, the direction of the force of thrust is generally fixed in the body frame, though some aircraft can vary this direction, for example by thrust vectoring . The wind frame

1225-545: The approach was the Avro Vulcan . Serious consideration was given to using the approach on the Airbus A380. A fly-by-wire (FBW) system replaces manual flight control of an aircraft with an electronic interface. The movements of flight controls are converted to electronic signals transmitted by wires (hence the term fly-by-wire ), and flight control computers determine how to move the actuators at each control surface to provide

1274-422: The body frame from the Earth frame, there is this analogy between angles: Between the three reference frames there are hence these analogies: In analyzing the stability of an aircraft, it is usual to consider perturbations about a nominal steady flight state. So the analysis would be applied, for example, assuming: The speed, height and trim angle of attack are different for each flight condition, in addition,

1323-502: The control surfaces and linkages from damage from wind. Some aircraft have gust locks fitted as part of the control system. Increases in the control surface area, and the higher airspeeds required by faster aircraft resulted in higher aerodynamic loads on the flight control systems. As a result, the forces required to move them also become significantly larger. Consequently, complicated mechanical gearing arrangements were developed to extract maximum mechanical advantage in order to reduce

1372-437: The control surfaces reducing the amount of mechanical forces needed. This arrangement was used in early piston-engined transport aircraft and in early jet transports. The Boeing 737 incorporates a system, whereby in the unlikely event of total hydraulic system failure, it automatically and seamlessly reverts to being controlled via servo-tab. The complexity and weight of mechanical flight control systems increase considerably with

1421-435: The control surfaces using cables, others (fly-by-wire airplanes) have a computer in between which then controls the electrical actuators. Even when an aircraft uses variant flight control surfaces such as a V-tail ruddervator , flaperons , or elevons , because these various combined-purpose control surfaces control rotation about the same three axes in space, the aircraft's flight control system will still be designed so that

1470-583: The controls of the RAF 's Avro Vulcan jet bomber and the RCAF 's Avro Canada CF-105 Arrow supersonic interceptor (both 1950s-era designs), the required force feedback was achieved by a spring device. The fulcrum of this device was moved in proportion to the square of the air speed (for the elevators) to give increased resistance at higher speeds. For the controls of the American Vought F-8 Crusader and

1519-598: The direction of vehicles. In this use, active flow control promises simplicity and lower mass, costs (up to half less), and inertia and response times. This was demonstrated in the Demon UAV , which flew for the first time in the UK in September 2010. Flight dynamics (fixed-wing aircraft) Flight dynamics is the science of air vehicle orientation and control in three dimensions. The three critical flight dynamics parameters are

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1568-413: The entertainment industry, including theatre , film , and live concert performances. In entertainment rigging , turnbuckles are more commonly used to make small adjustments in line lengths. This is generally to make a flown (hoisted) unit sit parallel to the stage. Another way a turnbuckle could prove helpful is with making very minor height or angle adjustments. Turnbuckles are used in piping systems as

1617-412: The equation, obtaining two terms C D0 and C Di . C D0 is known as the parasitic drag coefficient and it is the base drag coefficient at zero lift. C Di is known as the induced drag coefficient and it is produced by the body lift. A good attempt for the induced drag coefficient is to assume a parabolic dependency of the lift Aerodynamic efficiency is now calculated as: If the configuration of

1666-410: The expected response. Commands from the computers are also input without the pilot's knowledge to stabilize the aircraft and perform other tasks. Electronics for aircraft flight control systems are part of the field known as avionics . Fly-by-optics, also known as fly-by-light , is a further development using fiber-optic cables . Several technology research and development efforts exist to integrate

1715-472: The eye bolts or attached cables. Turnbuckles are most commonly used in applications which require a great deal of tension ; they can range in mass from about 10 grams ( 3 ⁄ 8  oz) for thin cable used in a garden fence , to tonnes for structural elements in buildings and suspension bridges . Turnbuckles have been used in aircraft construction, especially during the early years of aviation. Historically, biplanes might use turnbuckles to adjust

1764-403: The flight dynamics involved in establishing and controlling attitude are entirely different. Control systems adjust the orientation of a vehicle about its cg. A control system includes control surfaces which, when deflected, generate a moment (or couple from ailerons) about the cg which rotates the aircraft in pitch, roll, and yaw. For example, a pitching moment comes from a force applied at

1813-456: The forces required from the pilots. This arrangement can be found on bigger or higher performance propeller aircraft such as the Fokker 50 . Some mechanical flight control systems use servo tabs that provide aerodynamic assistance. Servo tabs are small surfaces hinged to the control surfaces. The flight control mechanisms move these tabs, aerodynamic forces in turn move, or assist the movement of

1862-608: The functions of 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, also known as "morphing aerofoils", much or all of

1911-550: The outer layer of the space that surrounds the body viscosity will be negligible. However viscosity effects will have to be considered when analysing the flow in the nearness of the boundary layer . Depending on the compressibility of the flow, different kinds of currents can be considered: If the geometry of the body is fixed and in case of symmetric flight (β=0 and Q=0), pressure and friction coefficients are functions depending on: where: Under these conditions, drag and lift coefficient are functions depending exclusively on

1960-437: The pilot finer control over flight or to ease the workload. The most commonly available control is a wheel or other device to control elevator trim , so that the pilot does not have to maintain constant backward or forward pressure to hold a specific pitch attitude (other types of trim, for rudder and ailerons , are common on larger aircraft but may also appear on smaller ones). Many aircraft have wing flaps , controlled by

2009-470: The plane is symmetrical respect to the XY plane, minimum drag coefficient equals to the parasitic drag of the plane. In case the configuration is asymmetrical respect to the XY plane, however, minimum drag differs from the parasitic drag. On these cases, a new approximate parabolic drag equation can be traced leaving the minimum drag value at zero lift value. The Coefficient of pressure varies with Mach number by

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2058-473: The reference frame of the Earth: In many flight dynamics applications, the Earth frame is assumed to be inertial with a flat x E , y E -plane, though the Earth frame can also be considered a spherical coordinate system with origin at the center of the Earth. The other two reference frames are body-fixed, with origins moving along with the aircraft, typically at the center of gravity. For an aircraft that

2107-400: The relation given below: where This relation is reasonably accurate for 0.3 < M < 0.7 and when M = 1 it becomes ∞ which is impossible physical situation and is called Prandtl–Glauert singularity . see Aerodynamic force Stability is the ability of the aircraft to counteract disturbances to its flight path. Turnbuckle A turnbuckle , stretching screw or bottlescrew

2156-416: The roll, pitch, and yaw Euler angles that describe the body frame orientation relative to the Earth frame. The other sets of Euler angles are described below by analogy. Based on the rotations and axes conventions above: When performing the rotations described above to obtain the body frame from the Earth frame, there is this analogy between angles: When performing the rotations described earlier to obtain

2205-496: The size and performance of the aircraft. Hydraulically powered control surfaces help to overcome these limitations. With hydraulic flight control systems, the aircraft's size and performance are limited by economics rather than a pilot's muscular strength. At first, only-partially boosted systems were used in which the pilot could still feel some of the aerodynamic loads on the control surfaces (feedback). A hydro-mechanical flight control system has two parts: The pilot's movement of

2254-655: The stick or yoke controls pitch and roll conventionally, as will the rudder pedals for yaw. The basic pattern for modern flight controls was pioneered by French aviation figure Robert Esnault-Pelterie , with fellow French aviator Louis Blériot popularizing Esnault-Pelterie's control format initially on Louis' Blériot VIII monoplane in April 1908, and standardizing the format on the July 1909 Channel-crossing Blériot XI . Flight control has long been taught in such fashion for many decades, as popularized in ab initio instructional books such as

2303-399: The tangent line from the coordinate origin touches the drag coefficient equation plot. The drag coefficient, C D , can be decomposed in two ways. First typical decomposition separates pressure and friction effects: There is a second typical decomposition taking into account the definition of the drag coefficient equation. This decomposition separates the effect of the lift coefficient in

2352-496: The tension on structural wires bracing their wings. Turnbuckles are also widely used on flexible cables in flight control systems. In both cases they are secured with lockwire or specifically designed wire clips to prevent them from turning and losing tension due to vibration. Turnbuckles are used for tensioning a ship's rigging and lashings . A variant of the turnbuckle called a bottle screw features an enclosed tubular body. Turnbuckles are used in nearly all rigging performed in

2401-515: The warping-operated pitch and roll controls. A manual flight control system uses a collection of mechanical parts such as pushrods, tension cables, pulleys, counterweights, and sometimes chains to transmit the forces applied to the cockpit controls directly to the control surfaces. Turnbuckles are often used to adjust control cable tension. The Cessna Skyhawk is a typical example of an aircraft that uses this type of system. Gust locks are often used on parked aircraft with mechanical systems to protect

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