Solid-state electronics
Solid-state electronics means semiconductor electronics. The term is used for devices in which semiconductor electronics which have no moving parts replace devices with moving parts, such as the solid-state relay in which transistor switches are used in place of a moving-arm electromechanical relay, or the solid-state drive a type of semiconductor memory used in computers to replace hard disk drives, which store data on a rotating disk; the term "solid state" became popular in the beginning of the semiconductor era in the 1960s to distinguish this new technology based on the transistor, in which the electronic action of devices occurred in a solid state, from previous electronic equipment that used vacuum tubes, in which the electronic action occurred in a gaseous state. A semiconductor device works by controlling an electric current consisting of electrons or holes moving within a solid crystalline piece of semiconducting material such as silicon, while the thermionic vacuum tubes it replaced worked by controlling current conducted by a gas of particles, electrons or ions, moving in a vacuum within a sealed tube.
Although the first solid state electronic device was the cat's whisker detector, a crude semiconductor diode invented around 1904, solid state electronics started with the invention of the transistor in 1947. Before that, all electronic equipment used vacuum tubes, because vacuum tubes were the only electronic components that could amplify, an essential capability in all electronics; the replacement of bulky, energy-wasting vacuum tubes by transistors in the 1960s and 1970s created a revolution not just in technology but in people's habits, making possible the first portable consumer electronics such as the transistor radio, cassette tape player, walkie-talkie and quartz watch, as well as the first practical computers and mobile phones. Today all electronics are solid-state except in some applications such as radio transmitters, in which vacuum tubes are still used, some power industrial control circuits which use electromechanical devices such as relays. Additional examples of solid state electronic devices are the microprocessor chip, LED lamp, solar cell, charge coupled device image sensor used in cameras, semiconductor laser.
Condensed matter physics Laser diode Materials science Semiconductor device Solar cell Solid-state physics
Primary flight display
A primary flight display or PFD is a modern aircraft instrument dedicated to flight information. Much like multi-function displays, primary flight displays are built around a Liquid-crystal display or CRT display device. Representations of older six pack or "steam gauge" instruments are combined on one compact display, simplifying pilot workflow and streamlining cockpit layouts. Most airliners built since the 1980s — as well as many business jets and an increasing number of newer general aviation aircraft — have glass cockpits equipped with primary flight and multi-function displays. Cirrus Aircraft was the first general aviation manufacturer to add a PFD to their existing MFD, which they made standard on their SR-series aircraft in 2003. Mechanical gauges have not been eliminated from the cockpit with the onset of the PFD. While the PFD does not directly use the pitot-static system to physically display flight data, it still uses the system to make altitude, vertical speed, other measurements using air pressure and barometric readings.
An air data computer displays it to the pilot in a readable format. A number of manufacturers produce PFDs, varying in appearance and functionality, but the information is displayed to the pilot in a similar fashion. FAA regulation describes that a PFD includes at a minimum, an airspeed indicator, turn coordinator, attitude indicator, heading indicator and vertical speed indicator; the details of the display layout on a primary flight display can vary enormously, depending on the aircraft, the aircraft's manufacturer, the specific model of PFD, certain settings chosen by the pilot, various internal options that are selected by the aircraft's owner. However, the great majority of PFDs follow a similar layout convention; the center of the PFD contains an attitude indicator, which gives the pilot information about the aircraft's pitch and roll characteristics, the orientation of the aircraft with respect to the horizon. Unlike a traditional attitude indicator, the mechanical gyroscope is not contained within the panel itself, but is rather a separate device whose information is displayed on the PFD.
The attitude indicator is designed to look much like traditional mechanical AIs. Other information that may or may not appear on or about the attitude indicator can include the stall angle, a runway diagram, ILS localizer and glide-path “needles”, so on. Unlike mechanical instruments, this information can be dynamically updated; the PFD may show an indicator of the aircraft's future path, as calculated by onboard computers, making it easier for pilots to anticipate aircraft movements and reactions. To the left and right of the attitude indicator are the airspeed and altitude indicators, respectively; the airspeed indicator displays the speed of the aircraft in knots, while the altitude indicator displays the aircraft's altitude above mean sea level. These measurements are conducted through the aircraft's pitot system, which tracks air pressure measurements; as in the PFD's attitude indicator, these systems are displayed data from the underlying mechanical systems, do not contain any mechanical parts.
Both of these indicators are presented as vertical “tapes”, which scroll up and down as altitude and airspeed change. Both indicators may have “bugs”, that is, indicators that show various important speeds and altitudes, such as V speeds calculated by a flight management system, do-not-exceed speeds for the current configuration, stall speeds, selected altitudes and airspeeds for the autopilot, so on; the vertical speed indicator next to the altitude indicator, indicates to the pilot how fast the aircraft is ascending or descending, or the rate at which the altitude changes. This is represented with numbers in "thousands of feet per minute." For example, a measurement of "+2" indicates an ascent of 2000 feet per minute, while a measurement of "-1.5" indicates a descent of 1500 feet per minute. There may be a simulated needle showing the general direction and magnitude of vertical movement. At the bottom of the PFD is the heading display, which shows the pilot the magnetic heading of the aircraft.
This functions much like a standard magnetic heading indicator. This part of the display shows not only the current heading, but the current track, rate of turn, current heading setting on the autopilot, other indicators. Other information displayed on the PFD includes navigational marker information, bugs, ILS glideslope indicators, course deviation indicators, altitude indicator QFE settings, much more. Although the layout of a PFD can be complex, once a pilot is accustomed to it the PFD can provide an enormous amount of information with a single glance. Starting with the A350-1000, Airbus proposes a common symbology on the PFD and HUD centered on a flightpath vector and an energy cue instead of a flight director, supplementing the usual pitch and heading indications to improve situational awareness, helping incorporating synthetic vision into the PFD; the great variability in the precise details of PFD layout makes it necessary for pilots to study the specific PFD of the specific aircraft they will be flying in advance, so tha
Turn and slip indicator
In aviation, the turn and slip indicator and the turn coordinator variant are two aircraft flight instruments in one device. One indicates the rate of turn; the slip indicator is an inclinometer that at rest displays the angle of the aircraft's transverse axis with respect to horizontal, in motion displays this angle as modified by the acceleration of the aircraft. The turn and slip indicator can be referred to as the turn and bank indicator, although the instrument does not respond directly to bank angle. Neither does the turn coordinator, but it does respond to roll rate, which enables it to respond more to the start of a turn; the turn indicator is a gyroscopic instrument. The gyro is mounted in a gimbal; the gyro's rotational axis is in-line with the transverse axis of the aircraft, while the gimbal has limited freedom around the longitudinal axis of the aircraft. As the aircraft yaws, a torque force is applied to the gyro around the vertical axis, due to aircraft yaw, which causes gyro precession around the roll axis.
The gyro spins on an axis, 90 degrees relative to the direction of the applied yaw torque force. The gyro and gimbal rotate with limited freedom against a calibrated spring; the torque force against the spring reaches an equilibrium and the angle that the gimbal and gyro become positioned is directly connected to the display needle, thereby indicating the rate of turn. In the turn coordinator, the gyro is canted 30 degrees from the horizontal so it responds to roll as well as yaw; the display contains hash marks for the pilot's reference during a turn. When the needle is lined up with a hash mark, the aircraft is performing a "standard rate turn", defined as three degrees per second, known in some countries as "rate one"; this translates to two minutes per 360 degrees of turn. Indicators are marked as to their sensitivity, with "2 min turn" for those whose hash marks correspond to a standard rate or two-minute turn, "4 min turn" for those, used in faster aircraft, that show a half standard rate or four-minute turn.
The supersonic Concorde jet aircraft and many military jets are examples of aircraft. Turn indicators; the hash marks are sometimes called "dog houses", because of their distinct shape on various makes of turn indicators. Under instrument flight rules, using these figures allows a pilot to perform timed turns in order to conform with the required air traffic patterns. For a change of heading of 90 degrees, a turn lasting 30 seconds would be required to perform a standard rate or "rate one" turn. Coordinated flight indication is obtained by using an inclinometer, recognized as the "ball in a tube". An inclinometer contains a ball sealed inside a curved glass tube, which contains a liquid to act as a damping medium; the original form of the indicator is in effect a spirit level with the tube curved in the opposite direction and a bubble replacing the ball. In some early aircraft the indicator was a pendulum with a dashpot for damping; the ball gives an indication of whether the aircraft is skidding or in coordinated flight.
The ball's movement is caused by the aircraft's centripetal acceleration. When the ball is centered in the middle of the tube, the aircraft is said to be in coordinated flight. If the ball is on the inside of a turn, the aircraft is slipping, and when the ball is on the outside of the turn, the aircraft is skidding. A simple alternative to the balance indicator used on gliders is a yaw string, which allows the pilot to view the string's movements as rudimentary indication of aircraft balance; the turn coordinator is a further development of the turn and slip indicator with the major difference being the display and the axis upon which the gimbal is mounted. The display is that of a miniature airplane; this looks similar to that of an attitude indicator. "NO PITCH INFORMATION" is written on the instrument to avoid confusion regarding the aircraft's pitch, which can be obtained from the artificial horizon instrument. In contrast to the T/S, the TC's gimbal is pitched up 30 degrees from the transverse axis.
This causes the instrument to respond to roll as well as yaw. This allows the instrument to display a change more as it will react to the change in roll before the aircraft has begun to yaw. Although this instrument reacts to changes in the aircraft's roll, it does not display the roll attitude; the turn coordinator may be used as a performance instrument. This is called "partial panel" operations, it can be unnecessarily difficult or impossible if the pilot does not understand that the instrument is showing roll rates as well as turn rates. The usefulness is impaired if the internal dashpot is worn out. In the latter case, the instrument is underdamped and in turbulence will indicate large full-scale deflections to the left and right, all of which are roll rate responses. Slipping and skidding within a turn is sometimes referred to as a sloppy turn, due to the perceptive discomfort it can cause to the pilot and passengers; when the aircraft is in a balanced turn, passengers experience gravity directly in line with their seat.
With a well balanced turn, passengers may not realize the aircraft is turning unless they are viewing objects outside the aircraft. While aircraft slipping and skidding are undesired in
Heading indicator
The heading indicator is a flight instrument used in an aircraft to inform the pilot of the aircraft's heading. It is sometimes referred to by its older names, the directional gyro or DG, direction indicator or DI; the primary means of establishing the heading in most small aircraft is the magnetic compass, however, suffers from several types of errors, including that created by the "dip" or downward slope of the Earth's magnetic field. Dip error causes the magnetic compass to read incorrectly whenever the aircraft is in a bank, or during acceleration or deceleration, making it difficult to use in any flight condition other than unaccelerated straight and level. To remedy this, the pilot will manoeuvre the airplane with reference to the heading indicator, as the gyroscopic heading indicator is unaffected by dip and acceleration errors; the pilot will periodically reset the heading indicator to the heading shown on the magnetic compass. The heading indicator works using a gyroscope, tied by an erection mechanism to the aircraft yawing plane, i. e. the plane defined by the longitudinal and the transverse axis of the aircraft.
As such, any configuration of the aircraft yawing plane that does not match the local Earth horizontal results in an indication error. The heading indicator is arranged such that the gyro axis is used to drive the display, which consists of a circular compass card calibrated in degrees; the gyroscope is spun either electrically, or using filtered air flow from a suction pump driven from the aircraft's engine. Because the Earth rotates, because of small accumulated errors caused by imperfect balancing of the gyro, the heading indicator will drift over time, must be reset using a magnetic compass periodically; the apparent drift will thus be greatest over the poles. To counter for the effect of Earth rate drift a latitude nut can be set which induces a real wander in the gyroscope. Otherwise it would be necessary to manually realign the direction indicator once each ten to fifteen minutes during routine in-flight checks. Failure to do this is a common source of navigation errors among new pilots.
Another sort of apparent drift exists in the form of transport wander, caused by the aircraft movement and the convergence of the meridian lines towards the poles. It equals the course change along a great circle flight path; some more expensive heading indicators are "slaved" to a magnetic sensor, called a "flux gate". The flux gate continuously senses the Earth's magnetic field, a servo mechanism corrects the heading indicator; these "slaved gyros" reduce pilot workload by eliminating the need for manual realignment every ten to fifteen minutes. The prediction of drift in degrees per hour, is as follows: Although it is possible to predict the drift, there will be minor variations from this basic model, accounted for by gimbal error, among others. A common source of error here is the improper setting of the latitude nut; the table however allows one to gauge whether an indicator is behaving as expected, as such, is compared with the realignment corrections made with reference to the magnetic compass.
Transport wander is an undesirable consequence of apparent drift. Acronyms and abbreviations in avionics Earth Inductor Compass Gyrocompass, a compass depending on gyroscopic precession effect instead of a basic gyroscopic effect Horizontal situation indicator Inertial navigation system, a far more complex system of gyroscopes that employ accelerometers
Air India Flight 855
Air India Flight 855 was a scheduled passenger flight that crashed during the evening of New Year's Day 1978 about 3 km off the coast of Bandra, Bombay. All 213 passengers and crew on board were killed; the crash is believed to have been caused by the captain having become spatially disoriented after the failure of one of the flight instruments in the cockpit. It was Air India's deadliest aircraft crash until the bombing of Flight 182 in 1985, it was the deadliest aviation accident in India until the Charkhi Dadri mid-air collision in 1996. As of 2018, Flight 855 is still the second deadliest aircraft crash in both of these categories; the aircraft involved was registration VT-EBD, named Emperor Ashoka. It was the first 747 delivered to Air India, in April 1971; the flight crew consisted of the following persons: The captain was 51-year old Mandan Lal Kukar. He had joined Air India in 1956, was experienced, having 18,000 flight hours; the first officer was 42-year-old Indu Virmani, a former Air Force commander who joined Air India in 1976.
He had 4,000 flight hours. The flight engineer was 53-year-old Alfredo Faria, who joined Air India in 1955 and had 11,000 flight hours, making him one of Air India's most senior flight engineers at the time of the accident; the aircraft departed from Bombay's Santa Cruz Airport. The destination was Dubai International Airport in Dubai. One minute after takeoff from runway 27, Captain Kukar made a scheduled right turn upon crossing the Bombay coastline over the Arabian Sea, after which the aircraft returned to a normal level position. Soon it began rolling to the left, never regained level flight; the cockpit voice recorder recovered from the wreckage revealed that captain Kukar was the first to notice a problem, when he said, "What's happened here, my instruments..." The captain was explaining that his Attitude indicator had "toppled", meaning that it was still showing the aircraft in a right bank. First officer Virmani, whose functional AI was now showing a left bank, said, "Mine has toppled, looks fine."
This indicated that his AI was toppled, but there is some belief that the Captain mistakenly took this to mean that both primary AIs were indicating a right bank. It was after sunset and the aircraft was flying over a dark Arabian Sea, leaving the aircrew unable to visually cross-check their AI instrument readings with the actual horizon outside the cockpit windows; the Boeing 747 had a third backup AI in the center instrument panel between the two pilots, the transcripts of the cockpit conversation showed flight engineer Faria telling the captain, "Don't go by that one, don't go by that one..." trying to direct his attention towards that third AI, or to another instrument called the turn and bank indicator, just five seconds before the aircraft impacted the sea. The captain's mistaken perception of the aircraft's attitude resulted in him using the aircraft flight control system to add more left bank and left rudder, causing the Boeing 747 to roll further left into a bank of 108 degrees and lose altitude.
Just 101 seconds after leaving the runway, the jet hit the Arabian Sea at an estimated 35-degree nose-down angle. There were no survivors among 23 crew members; the recovered wreckage revealed no evidence of explosion, fire, or any electrical or mechanical failure. The investigation concluded that the probable cause was "due to the irrational control inputs by the captain following complete unawareness of the attitude as his AI had malfunctioned; the crew failed to gain control based on the other flight instruments." US Federal District Judge James M. Fitzgerald, in a 139-page decision issued 1 November 1985, rejected charges of negligence against the Boeing Company, Lear Siegler Inc, the Collins Division of Rockwell International Corporation in a suit related to the crash, it was dismissed in 1986. Sensory illusions in aviation John F. Kennedy, Jr. plane crash Other aircraft that crashed shortly after takeoff, while turning above a dark ocean: Pan Am Flight 816 Flash Airlines Flight 604 Viasa Flight 897 Other aircraft that crashed due to instrument malfunction: Korean Air Cargo Flight 8509 Copa Airlines Flight 201 Birgenair Flight 301 Aeroperú Flight 603 Adam Air Flight 574 Air France Flight 447 Langewiesche, William.
"Chapter Four: On A Bombay Night". Inside the Sky: A Meditation on Flight. USA: Pantheon Books. ISBN 0-679-42983-2. Design Induced Errors, which includes a discussion of the crash. Pre-crash photos of 747 VT-EBD at airliners.net
Gyroscope
A gyroscope is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rotation is free to assume any orientation by itself; when rotating, the orientation of this axis is unaffected by tilting or rotation of the mounting, according to the conservation of angular momentum. Gyroscopes based on other operating principles exist, such as the microchip-packaged MEMS gyroscopes found in electronic devices, solid-state ring lasers, fibre optic gyroscopes, the sensitive quantum gyroscope. Applications of gyroscopes include inertial navigation systems, such as in the Hubble Telescope, or inside the steel hull of a submerged submarine. Due to their precision, gyroscopes are used in gyrotheodolites to maintain direction in tunnel mining. Gyroscopes can be used to construct gyrocompasses, which complement or replace magnetic compasses, to assist in stability or be used as part of an inertial guidance system. MEMS gyroscopes are popular in some consumer electronics, such as smartphones.
A gyroscope is a wheel mounted in two or three gimbals, which are pivoted supports that allow the rotation of the wheel about a single axis. A set of three gimbals, one mounted on the other with orthogonal pivot axes, may be used to allow a wheel mounted on the innermost gimbal to have an orientation remaining independent of the orientation, in space, of its support. In the case of a gyroscope with two gimbals, the outer gimbal, the gyroscope frame, is mounted so as to pivot about an axis in its own plane determined by the support; this outer gimbal possesses one degree of rotational freedom and its axis possesses none. The inner gimbal is mounted in the gyroscope frame so as to pivot about an axis in its own plane, always perpendicular to the pivotal axis of the gyroscope frame; this inner gimbal has two degrees of rotational freedom. The axle of the spinning wheel defines the spin axis; the rotor is constrained to spin about an axis, always perpendicular to the axis of the inner gimbal. So the rotor possesses three degrees of its axis possesses two.
The wheel responds to a force applied to the input axis by a reaction force to the output axis. The behaviour of a gyroscope can be most appreciated by consideration of the front wheel of a bicycle. If the wheel is leaned away from the vertical so that the top of the wheel moves to the left, the forward rim of the wheel turns to the left. In other words, rotation on one axis of the turning wheel produces rotation of the third axis. A gyroscope flywheel will roll or resist about the output axis depending upon whether the output gimbals are of a free or fixed configuration. Examples of some free-output-gimbal devices would be the attitude reference gyroscopes used to sense or measure the pitch and yaw attitude angles in a spacecraft or aircraft; the centre of gravity of the rotor can be in a fixed position. The rotor spins about one axis and is capable of oscillating about the two other axes, it is free to turn in any direction about the fixed point; some gyroscopes have mechanical equivalents substituted for one or more of the elements.
For example, the spinning rotor may be suspended instead of being mounted in gimbals. A control moment gyroscope is an example of a fixed-output-gimbal device, used on spacecraft to hold or maintain a desired attitude angle or pointing direction using the gyroscopic resistance force. In some special cases, the outer gimbal may be omitted so that the rotor has only two degrees of freedom. In other cases, the centre of gravity of the rotor may be offset from the axis of oscillation, thus the centre of gravity of the rotor and the centre of suspension of the rotor may not coincide. A gyroscope is a top combined with a pair of gimbals. Tops were invented in many different civilizations, including classical Greece and China. Most of these were not utilized as instruments; the first known apparatus similar to a gyroscope was invented by John Serson in 1743. It was used as a level, to locate the horizon in misty conditions; the first instrument used more like an actual gyroscope was made by Johann Bohnenberger of Germany, who first wrote about it in 1817.
At first he called it the "Machine". Bohnenberger's machine was based on a rotating massive sphere. In 1832, American Walter R. Johnson developed a similar device, based on a rotating disc; the French mathematician Pierre-Simon Laplace, working at the École Polytechnique in Paris, recommended the machine for use as a teaching aid, thus it came to the attention of Léon Foucault. In 1852, Foucault used it in an experiment involving the rotation of the Earth, it was Foucault who gave the device its modern name, in an experiment to see the Earth's rotation, visible in the 8 to 10 minutes before friction slowed the spinning rotor. In the 1860s, the advent of electric motors made it possible for a gyroscope to spin indefinitely; the first functional gyrocompass was patented in 1904 by German inventor Hermann Anschütz-Kaempfe. American Elmer Sperry followed with his own design that year, other nations soon realized the military importance of the invention—in an age in which naval prowess was the most significant measure of military power—and crea
Aircraft principal axes
An aircraft in flight is free to rotate in three dimensions: yaw, nose left or right about an axis running up and down. The axes are alternatively designated as vertical and longitudinal respectively; these axes rotate relative to the Earth along with the craft. These definitions were analogously applied to spacecraft when the first manned spacecraft were designed in the late 1950s; these rotations are produced by torques about the principal axes. On an aircraft, these are intentionally produced by means of moving control surfaces, which vary the distribution of the net aerodynamic force about the vehicle's center of gravity. Elevators produce pitch, a rudder on the vertical tail produces yaw, ailerons produce roll. On a spacecraft, the moments are produced by a reaction control system consisting of small rocket thrusters used to apply asymmetrical thrust on the vehicle. Normal axis, or yaw axis — an axis drawn from top to bottom, perpendicular to the other two axes. Parallel to the fuselage station.
Transverse axis, lateral axis, or pitch axis — an axis running from the pilot's left to right in piloted aircraft, parallel to the wings of a winged aircraft. Parallel to the buttock line. Longitudinal axis, or roll axis — an axis drawn through the body of the vehicle from tail to nose in the normal direction of flight, or the direction the pilot faces. Parallel to the waterline; these axes are represented by the letters X, Y and Z in order to compare them with some reference frame named x, y, z. This is made in such a way that the X is used for the longitudinal axis, but there are other possibilities to do it; the yaw axis has its origin at the center of gravity and is directed towards the bottom of the aircraft, perpendicular to the wings and to the fuselage reference line. Motion about this axis is called yaw. A positive yawing motion moves the nose of the aircraft to the right; the rudder is the primary control of yaw. The term yaw was applied in sailing, referred to the motion of an unsteady ship rotating about its vertical axis.
Its etymology is uncertain. The pitch axis has its origin at the center of gravity and is directed to the right, parallel to a line drawn from wingtip to wingtip. Motion about this axis is called pitch. A positive pitching motion lowers the tail; the elevators are the primary control of pitch. The roll axis has its origin at the center of gravity and is directed forward, parallel to the fuselage reference line. Motion about this axis is called roll. An angular displacement about this axis is called bank. A positive rolling motion lowers the right wing; the pilot rolls by decreasing it on the other. This changes the bank angle; the ailerons are the primary control of bank. The rudder has a secondary effect on bank; these axes are not the same. They are geometrical symmetry axes, regardless of the mass distribution of the aircraft. In aeronautical and aerospace engineering intrinsic rotations around these axes are called Euler angles, but this conflicts with existing usage elsewhere; the calculus behind them is similar to the Frenet–Serret formulas.
Performing a rotation in an intrinsic reference frame is equivalent to right-multiplying its characteristic matrix by the matrix of the rotation. The first aircraft to demonstrate active control about all three axes was the Wright brothers' 1902 glider. Aerodynamics Aircraft flight control system Euler angles Fixed-wing aircraft Flight control surfaces Flight dynamics Moving frame Panning Six degrees of freedom Screw theory Triad method Yaw Axis Control as a Means of Improving V/STOL Aircraft Performance. 3D fast walking simulation of biped robot by yaw axis moment compensation Flight control system for a hybrid aircraft in the yaw axis
