Black box is a generic term used to describe the computerized flight data recorders carried by modern commercial aircraft. The Flight Data Recorder (FDR) is a miniaturized computer system which tracks a variety of data regarding the flight of the plane, such as airspeed, position, and altitude. This device is typically used in conjunction with a second black box known as the Cockpit Voice Recorder (CVR), which documents radio transmissions and sounds in the cockpit, such as the pilots' voices and engine noises. In the event of a mishap, the information stored in these black boxes can be used to help determine the cause of the accident.
Black boxes have been used since the earliest days of aviation. The Wright brothers carried the first flight recorder aloft on one of their initial flights. This crude device registered limited flight data such as duration, speed, and number of engine revolutions. Another early aviation pioneer, Charles Lindbergh, used a somewhat more sophisticated version consisting of a barograph, which marked ink on paper wrapped around a rotating drum. The entire device was contained in a small wooden box the size of an index card holder. Unfortunately, these early prototypes were not sturdily constructed and could not survive a crash.
In the 1940s, as commercial aviation grew by leaps and bounds, a series of crashes spurred the Civil Aeronautics Board to take the importance of flight data more seriously. They worked with a number of companies to develop a more reliable way of collecting data. Rising to the challenge, General Electric developed a system called the "selsyns," which consisted of a series of tiny electrodes attached directly to the plane's instruments. These sensors wired information to a recorder in the back of the plane. (Recorders are typically stored in the plane's tail section because it is the most crash-survivable area of the plane.) GE engineers overcame a number of technical challenges in the design of the selsyns. For example, they cleverly recognized that the high altitude conditions of low pressure and temperature would cause the ink typically used in recording devices to freeze or clog the pens. Their solution was a recording system that relied on a stylus to cut an image into black paper coated with white lacquer. However, despite their efforts, the unit was never used in an actual flight. Around the same time, another engineering company, Frederick Flader, developed an early magnetic tape recorder; however, this device was also never used.
Black box technology did not advance further until 1951, when professor James J. Ryan joined the mechanical division of General Mills. Ryan was an expert in instrumentation, vibration analysis, and machine design. Attacking the problem of FDRs, Ryan came up with his own VGA Flight Recorder. The "V" stands for Velocity (airspeed); "G" for G forces (vertical acceleration); and "A" is for altitude. The Ryan Recorder was a 10 lb (4.5-kg) device about the size of a bread box with two separate compartments. One section contained the measuring devices (the altimeter, the accelerometer, and the airspeed indicator) and the other contained the recording device, which connected to the three instruments.
Ryan's basic compartmentalized design is still used in flight recorders today, although it has undergone numerous improvements. The stylus and lacquer film recording device was replaced by one-quarter-inch (6.4mm) magnetic tape, which was in tum replaced by digital memory chips. The number of variables that recorders can track has also dramatically increased, from three or four parameters to about 300. FDRs can now track such in-flight characteristics as speed, altitude, flap position, auto-pilot mode, even the status of onboard smoke alarms. In the early 1960s, the airline industry added voice recording capability with the Cockpit Voice Recorder (CVR). But perhaps the most significant advance in flight recorder manufacture has been the improvements made in its construction, allowing the units to better withstand the destructive force of a crash. Early models had to withstand only about 100 Gs (100 times the force of gravity), which is loosely equivalent to the force of being dropped from about 10 ft (3 m) off the ground onto a concrete surface. To better simulate actual crash conditions, in 1965 the requirements were increased to 1,000 Gs for five milliseconds and later to 3,400 Gs for 6.5 milliseconds.
Today, large commercial aircraft and some smaller commercial, corporate, and private aircraft are required by the FAA to be equipped with a Cockpit Voice Recorder and a Flight Data Recorder. In the event of a crash, the black boxes can be recovered and sent, still sealed, to the National Transportation Safety Board (NSTB) for analysis.
The Flight Data Recorder and the Voice Data Recorder (or Cockpit Voice Recorder) are built from similar components. Both include a power supply, a memory unit, electronic controller board, input devices, and a signal beacon.
Both FDRs and CVRs run off of a dual voltage power supply (115 VAC or 28 DC) which gives the units the flexibility to be used in a variety of aircraft. The batteries are designed for 30-day continuous operation and have a six-year shelf life.
Crash Survivable Memory Unit (CSMU)
The CSMU is designed to retain 25 hours of digital flight information. The stored information is of very high quality because the unit's state of the art electronics allow it to hold data in an uncompressed form.
Integrated Controller and Circuitry Board (ICB)
This board contains the electronic circuitry that acts as switchboard for the incoming data.
This port serves as the connection for the input devices from which black boxes obtain all their information about the plane. The FDR interface receives and processes signals from a variety of instruments on board the plane, such as the airspeed indicator, on-board warning alarms, altimeter, etc. The interface employed for the CVR receives and processes signals from a cockpit-area microphone, which is usually mounted somewhere on the overhead instrument panel between the two pilots. The microphone is intended to pick up sounds that may aid investigators in determining the cause of a crash, such as engine noise, stall warnings, landing gear extension and retraction, and other clicks and pops. These sounds can help determine the time at which certain crash-related events occurred. The microphone also relays communications with Air Traffic Control, automated radio weather briefings, and conversation between the pilots and ground or cabin crew.
Underwater Locater Beacon (ULB)
Each recorder may be equipped with an Underwater Locator Beacon (ULB) to assist in identifying its location in the event of an overwater accident. The device, informally known as a "pinger," is activated when the recorder is immersed in water. It transmits an acoustical signal on 37.5 KHz that can be detected with a special receiver. The beacon can transmit from depths to 14,000 ft (4,200 m).
The key to manufacturing a successful black box is to make it as indestructible as possible. This is done by sheathing the components inside a multi-layer protective shell. The different makers of recorders each have their own proprietary design, but in general the manufacturing process can be described as follows:
- The key components (the power supply, the interface/controller board, and the memory circuits) are built as separate units and then assembled to form the completed black box. This modular approach allows the components to be easily replaced without disassembly of the entire device. Each of these components has its own special assembly requirements, but primary attention is given to the protecting the memory unit, since it contains the data that will be of interest to investigators.
- A multi-layered configuration is used to ensure the memory unit's integrated circuits are adequately protected. The outermost layer is the housing, which consists of steel armor plate.
- Below that is a layer of insulation, followed by a thick slab of paraffin, which forms a thermal block. As the paraffin melts, it absorbs heat and therefore keeps the temperature of the memory core lower.
- Beneath the paraffin lies the board containing the memory chips.
- Underneath the memory board is another paraffin thermal block, followed by another layer of insulation. The entire assembly is mounted on a steel plate that serves as an access cover.
- The assembled Crash Survivable Memory Unit is then bolted onto the front of a heavy metal plate mounting shelf with four large retaining bolts. The power supply is attached just behind the CSMU.
- The Interface and Control Circuit Board (ICB) is attached by screws to the underside of the mounting shelf. A metal access cover protects the board and provides easy access.
- The Underwater Locator Beacon (ULB) is affixed to the two arms extending from the front of the memory unit. The ULB protrudes from the casing and has a cylindrical shape that allows it to be used as a handle for the entire device. If the recorder is to be sold without a ULB, a hollow metal handle tube is installed in its place.
- The outer casing is painted bright orange or red to make it more visible in a crash.
After manufacture, the units are exposed to a series of grueling and somewhat bizarre torture test conditions. Black boxes are shot from cannons, stabbed by thin steel rods, attached to 500 lb (227 kg) weights and dropped from 10 ft (3 m) above the ground, crushed in a vice at 5,000 lb (2,270 kg) of pressure, cooked with a blow torch for an hour at 2,012°F (1,100°C), and submerged under the equivalent of 20,000 ft (6,000 m) of seawater for one month. After such testing, the onboard microprocessor allows a variety of diagnostics to be run to ensure the unit is operating correctly. The high speed interface allows the entire memory unit to be checked in under five minutes. This evaluation can be done at the factory to check that the unit is working perfectly, then again after installation to ensure it is still functioning properly. By regulation, flight recorders for newly manufactured aircraft must accurately monitor at least 28 critical factors, such as time, altitude, airspeed, heading, and aircraft attitude. The average time between failures for these devices should be greater than 15,000 hours, and they are designed to be maintenance free. If the unit passes all of the tests described above, it meets the requirements established by the FAA (Federal Aviation Authority).
The future is already unfolding for manufacturers of black boxes. Smith Industries, a major supplier of flight recorders, has recently announced it is developing a single device which will replace separate FDR and CVR units. Their device is known as an Integrated Data Acquisition Recorder (IDAR), and it incorporates flight and voice data in a single box configuration, together with a data transfer system for maintenance data retrieval. The introduction of the IDAR allows a 25% reduction in critical system weight. Interestingly, this new direction in product development comes at the same time as new legislation that makes the recording of data linked to air traffic control messages mandatory. This new law would require black boxes to contain even more information. It is likely that the manufacturers of flight recording equipment will rise to the challenge and develop black boxes that can store more and more information in ever-shrinking packages.
Where to Learn More
AlliedSignal Aerospace Catalog. AlliedSignal, Inc.
Baldwin, Tom. "Black boxes Built to Survive Doom." Journal of Commerce and Commercial, July 29, 1996, p. lB.
Goyer, Robert. "The Secrets of Black Boxes." Flying, December 1996, p. 88.
Sendzimir, Vanda. "Black Box." American Heritage of Invention & Technology, Fall 1996.
"Black Box." How Products Are Made. . Encyclopedia.com. (October 19, 2018). http://www.encyclopedia.com/manufacturing/news-wires-white-papers-and-books/black-box
"Black Box." How Products Are Made. . Retrieved October 19, 2018 from Encyclopedia.com: http://www.encyclopedia.com/manufacturing/news-wires-white-papers-and-books/black-box
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A general term for radionics devices used to diagnose disease. These devices supposedly tap the unknown forces involved in radiesthesia and dowsing, where instruments such as water-witching rods or small pendulums test for sensitivity to water, metals, or health conditions. The original "Black Box" was devised by Dr. Albert Abrams, an unconventional San Francisco physician in the early twentieth century. It consisted of a box, variously called the ERA or the Oscilloclast, with several variable rheostats and a thin sheet of rubber mounted over a metal plate. A blood sample from the patient would be put into the machine, which was connected with a metal plate placed on the forehead of a healthy person. By tapping on the abdomen of this person, the doctor determined the disease of the patient according to the "areas of dullness" identified by dial readings on the apparatus. This strange procedure brought together various techniques: Auscultation is part of normal medical practice, but the suggestion of a psychic relationship between a patient and his blood sample, plus the indications obtained from stroking the rubber sheet with the fingers, involved the paranormal sensitivities used in water witching with rod or pendulum.
Long after the death of Abrams in 1924, his theories and techniques were developed by Dr. Ruth Drown in the United States and George De la Warr in Britain. De la Warr devised a black box that produced photographs relating to the individual whose sample was placed in the machine. These photographs were more like thought processes than normal images. De la Warr claimed that they registered a radiation pattern related to the shape and chemical structure of the radiating body, and, given a suitable sample, the camera plate would register not only regional tissue but its pathology.
However, the black box did not operate uniformly, and thus it appears that the individual operators were greatly affecting the results. The inability to standardize results would deny its operation any scientific standing. One woman sued the De la Warr laboratories because she was unable to obtain satisfactory results. The case was dismissed on the grounds that there had been no intent to defraud, although the judge severely criticized the apparatus as bogus. Use of the black box is against the law in the United States. However, in a more sympathetic investigation of the apparatus, Lucian Landau suggested that success depended upon the special sensitivity of the operator. In this respect, the apparatus would be related to the phenomenon of thought photography as attempted by Ted Serios. For a negative view of Abrams, see the volume by Gardner.
Abrams, Albert. New Concepts in Diagnosis and Treatment. Physico-Clinical, 1924.
Barr, Sir James. Abrams' Methods of Diagnosis and Treatment. London, 1925.
De la Warr, George, with Langston Day. New Worlds Beyond the Atom. London: Vincent Stewart Publishers, 1956.
Firebrace, R. C., and Lucien Landau. "The Delawarr Camera." Light: A Journal of Psychic Science 77, no. 3430 (March 1937).
Gardner, Martin. Fads and Fallacies in the Name of Science. New York: Dover Publications, 1957.
Radionic Therapy (leaflet). Oxford, England: Delawarr Laboratories, 1953.
"Black Box." Encyclopedia of Occultism and Parapsychology. . Encyclopedia.com. (October 19, 2018). http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/black-box
"Black Box." Encyclopedia of Occultism and Parapsychology. . Retrieved October 19, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/black-box
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black box • n. a flight recorder in an aircraft. ∎ any complex piece of equipment, typically a unit in an electronic system, with contents that are mysterious to the user.
"black box." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. (October 19, 2018). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/black-box
"black box." The Oxford Pocket Dictionary of Current English. . Retrieved October 19, 2018 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/black-box
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Some say the term black box was coined because the box is burned to a blackish color when it is retrieved at the crash site.
"Black box" is a term used to describe the computerized recording equipment carried by modern commercial aircraft. The black box set typically consists of the flight data recorder (FDR) and the cockpit voice recorder (CVR). Each recorder is about the size of a shoe box, has reflective strips, and is bright orange in color. No one is exactly sure why the recorders are called black boxes. Some say the term was coined because the boxes are usually burned to a blackish color when retrieved at a crash site. Others believe the term is used because most electronic equipment in an airplane is housed in black boxes.
The FDR tracks a variety of data about the flight of the airplane, such as airspeed, altitude, and heading (the direction in which the aircraft is traveling). The CVR records radio transmissions and sounds in the cockpit, such as the flight crew's conversations, engine noises and warnings, and landing gear extension and retraction. Although the boxes are constructed to withstand fire, water, and tremendous impact, they are stored in the airplane tail section, the part that is most crash-survivable. In the event of an accident, information stored in these black boxes can help determine its cause.
Searching for the right black box
Wilbur (1867–1912) and Orville (1871–1948) Wright carried the first black box during one of their initial flights in the early 1900s in their hometown of Dayton, Ohio. The crude device recorded the length of flight, speed, and propeller rotation. Charles Lindbergh (1902–1974), the first person to make a nonstop solo flight across the Atlantic Ocean in 1927, also used a black box during his many flights. His black box consisted of a bar graph that marked changes in barometric pressure using ink on paper wrapped around a rotating drum.
In the early 1940s, with the increasing popularity of commercial flight, the Civil Aeronautics Board (CAB; now the Federal Aviation Administration, or FAA) concluded that there should be a reliable way to record flight data. After a series of airplane crashes occurred in the late 1940s, the CAB required that the aircraft industry look into ways of preserving its record of flight in the event of a crash. Early attempts at inventing a black box consisted of a stylus (a pointed instrument) that cut images into black paper coated with white lacquer and a device that used magnetic tape. A magnetic tape is a plastic tape coated with iron oxide for use in recording. However, these devices were never used.
The proper black box
It was not until 1948 that black box technology was developed. Professor James J. Ryan (1914–1973) of the University of Minnesota invented what he called the VGA Flight Recorder. The device was about the size of a breadbox and weighed 10 pounds (4.5 kilograms). It had two separate compartments. One compartment contained the measuring devices (the altimeter, the accelerometer, and the airspeed indicator), and the other held the recording device, which connected to the three instruments. The black box recorded flight information on aluminum tape. The device was encased in two steel containers, with about an inch of insulation in between. In 1951, the General Mills engineering department decided to fund Ryan's invention. Ryan's basic design is still used in black boxes today, although it has undergone numerous improvements.
In 1958, the CAB required commercial aircraft registered in the United States to have an approved flight data recorder on board. One single strip of aluminum foil recorded between 200 to 400 hours of data. A stylus literally scratched markings on the moving foil. In 1965, the CVR was added, and the recorders were painted orange or bright yellow so they could be easily located after a crash. In FDRs, the stylus-type recording was replaced with a .25-inch (6.4 millimeters) Mylar® magnetic tape.
JAMES "CRASH" RYAN
Professor James J. Ryan (1914–1973), the inventor of the black box, designed other useful devices. He earned the nickname "Crash" because of the crash tests he conducted to determine the forces that act on human-sized dummies during simulated car accidents. While teaching mechanical engineering at the University of Minnesota (1931–1963), Ryan experimented with safety devices for cars, including the automatic seat belt, which he patented in 1963. Believing that seat belts could cut automobile-related injuries and deaths in half, he took his research to Congress and to the car manufacturers. Met with disinterest, he persisted. Finally, in 1966, the federal government included the seat belt among the safety features required of cars being manufactured from then on.
Improved black boxes
In the 1970s, the FDRs began having problems handling the increasing volume of data being transmitted by the sensors. As a result, the flight data acquisition unit (FDAU) was introduced to act as middleman between the sensors and the FDR. The FDAU processed the data received from the sensors and then passed the data on to the FDR. The FDR magnetic tape recorded about twenty-five hours of data. However, the FDR tapes were found to be vulnerable to intense fire and impact shock. By early 1990, the magnetic tape was replaced by digital memory chips.
Just as the recording time has increased, the number of parameters the black box tracks has also grown—from about three or four to more than three hundred parameters. The parameters refer to the different pieces of information relating to the aircraft, such as the airspeed, altitude, vertical acceleration, heading, the time of each radio transmission to the air traffic control, cockpit conversations, and radio communications. As of 2002, the FAA required commercial aircraft to record twenty-eight parameters.
Perhaps the most significant advance in black box manufacture has been the improvement in its construction, allowing it to withstand the tremendous force of a crash. Early recorders withstood about 100 g's (100 times the force of gravity), which is similar to being dropped from a height of about 10 feet (3 meters) onto a concrete surface. This figure was increased to 1,000 g's and then to 3,400 g's.
The flight data recorder and the cockpit voice recorder have the same components (parts). Both have a power supply, a memory unit, electronic controller board, and a signal beacon.
INVESTIGATING AIRPLANE ACCIDENTS
The National Transportation Safety Board (NTSB) is responsible for investigating aviation accidents. The investigators determine the cause or probable cause of the accident and report the facts and circumstances relating to it. They are on call 24 hours a day, 365 days a year. The Federal Aviation Administration helps the NTSB investigate aviation accidents.
The black box gets its power supply from two generators, which in turn are powered by the plane's engines. One generator provides a power source of 28-volt DC (direct current), while the second generator has a power source of 115-volt AC (alternating current). The dual voltage allows the black boxes to be used in a variety of aircraft. The black box also has a battery that can run for thirty continuous days. The battery has a six-year shelf life.
Crash-survivable memory unit (CSMU)
The CSMU is designed to store twenty-five hours of digital (using computer memory chips) flight information. The stored information is of high quality because the memory chips can hold a huge amount of information in its original form.
Integrated controller and circuitry board (ICB)
The ICB contains the electronic circuitry that acts as a switchboard for the incoming data.
The interface, as its name implies, serves as the connection for the input devices from which the black boxes obtain information about the aircraft. The FDR interface receives and processes signals from aircraft instruments, such as the airspeed indicator, on-board warning alarms, and the altimeter (the instrument that measures altitude).
The CVR interface receives and processes signals from microphones found in the cockpit, including in the headsets of the two pilots and possibly of another crew member, as well as on the overhead instrument panel between the two pilots. The microphones pick up the conversations between the cockpit crew and between the cockpit and ground crews. Communications with air-traffic controllers and radio weather briefings are also collected and stored by the CVR. In addition, the microphones track engine noise, stall warnings, landing gear extension and retraction, and other sounds in the immediate surroundings.
Underwater locator beacon (ULB)
The cylindrical ULB, which also functions as the handle for picking up the black box, helps investigators identify its location in the event of an over-water accident. A submerger sensor in the ULB activates it when water touches that sensor. The ULB is called a "pinger" because, once it is activated, it makes a pinging sound once every second. It can transmit sound from as deep as 14,000 feet (4,267 meters) that can be detected by sonar. The ULB can make the pinging sound for thirty days.
The Manufacturing Process
The key components (the power supply, the interface and control circuit board, and the memory chip circuits) are constructed as separate units and then assembled to create the black box unit. This way, if one component needs replacing, the whole black box does not have to be taken apart.
Insulation for memory circuit board
1 Special attention is given to protecting the memory chip circuits since they will store the data that would be helpful to investigators in the event of an aircraft accident. Several layers of materials house the memory boards. The outermost housing is typically made of stainless steel, although some manufacturers may use titanium.
2 Underneath the stainless steel shell is a layer of insulation, followed by a thick slab of paraffin, which forms a thermal block. If fire occurs during an aircraft accident, the paraffin melts and absorbs the heat, thereby helping maintain a lower temperature for the memory board found underneath the paraffin.
3 Next comes another layer of paraffin thermal block and, finally, another layer of insulation. The whole insulation assembly is mounted on a steel plate, which can be removed to access the memory board.
Attaching the CSMU, the interface, and the ICB to the mounting shelf
4 Using four large bolts, the finished crash-survivable memory unit (CSMU) is fastened onto the front of a heavy metal-plate mounting shelf. The power supply is attached behind the CSMU.
5 The interface and the control circuit board are attached by screws to the underside of the mounting shelf. A metal protector cover, which also provides easy access, is placed over the board.
Attaching the ULB
6 The underwater locator beacon (ULB) is attached to the two arms that extend from the memory unit. The ULB is a cylinder that also serves as the handle for the black box. If the black box is sold without the ULB, the manufacturer attaches a hollow metal tube in its place. Then, the user installs the ULB.
Painting the outer casing
7 The outer casing is painted orange or bright yellow to make it more visible in case of a crash. Reflective strips are also applied.
Black boxes have to survive a crash so that the information they contain can be recovered by investigators. For this reason, manufacturers have to comply with federal regulations by subjecting the box to grueling testing measures that mimic catastrophic crash conditions. The simulated crash conditions are usually in excess of what the black box would experience in an actual crash.
To make sure the black box will survive the initial impact of a crash, it is fired from an air cannon toward an aluminum wall, hitting the wall at 3,400 times its weight. According to experts, this figure is equivalent to or more than the force of impact the black box would experience in an actual crash.
A piercing test involves dropping, from a height of ten feet (three meters), a 500-pound (227-kilogram) weight with an attached one-quarter-inch steel pin onto the black box. The box also undergoes a crushing pressure of 5,000 pounds (2,270 kilograms).
Since most aircraft accidents involve fire, the black box is cooked at 2,012 degrees Fahrenheit (1,100 degrees Celsius) for one hour, the temperature at which aviation fuel burns. The black box is also submerged under the equivalent of 20,000 feet (6,000 miles) of seawater for thirty days. Other tests include submersion in aviation fuel, lubricants, toilet-flushing liquid, and fire-extinguisher substances. Vibration tests are also performed.
Federal regulations require that flight data recorders for new commercial aircraft record twenty-eight parameters. The black boxes are designed to be maintenance-free, and the average time between failures should be greater than 15,000 hours.
A new black box design combines the FDR and the CVR. This type of black box has been used in military fighter craft and helicopters. This new unit is lightweight and takes up less space, while at the same time storing the same amount of information. It has been proposed that, since this design is available, an aircraft can have two of these combined black boxes, one to be stored at the usual location at the airplane's tail section, and the second one, near the cockpit. In addition, authorities are also studying the possibility of video recordings in light of recent advances in video technology.
The U.S. Congress requires that, because of the sensitive nature of the verbal communications inside the cockpit, the National Transportation Safety Board (NTSB) cannot release any portion of the cockpit voice recorder communications. Federal law also regulates the release of the written transcripts of the recordings.
A solution being proposed to preserve flight data during a crash involves a black box called a deployable flight incident recorder (DFIR). The device is designed to automatically bail out from a crashing aircraft and "fly away" from the accident site. This technology, which has been used in military planes and helicopters for over three decades, is quite expensive. The manufacturer, DRS Technologies, Inc., is developing the next-generation DFIR for the military, a design that takes into consideration the safety regulations and cost for commercial aircraft.
- Height above the Earth's surface.
- The force that pulls objects down toward the Earth.
- The direction in which an aircraft is traveling.
- memory chip:
- Also called microchip, a very small piece of silicon that carries interconnected electronic components.
- shelf life:
- The length of time a battery may be stored before it starts losing its effectiveness.
- A system that uses transmitted and reflected underwater sound waves to determine the location of a submerged object.
For More Information
"A Passion for Safety: Professor James 'Crash' Ryan." ME News (Winter 2000): pp. 6–7.
"Cockpit Voice Recorders (CVR) and Flight Data Recorders (FDR)." NationalTransportation Safety Board.http://www.ntsb.gov/Aviation/CVR_FDR.htm (accessed on July 22, 2002).
"Flight-Data Recorders: Orange Is Good, Black Is Bad." EDN Access.http:www.e-insite.net/ednmag/contents/images/178107.pdf (accessed on July 22, 2002).
"The 'Wright' Stuff." Federal Aviation Administration.http://www.faa.gov/education/wright/wright.htm (accessed on July 22, 2002).
"Black Box." CDs, Super Glue, and Salsa: How Everyday Products Are Made: Series 3. . Encyclopedia.com. (October 19, 2018). http://www.encyclopedia.com/education/culture-magazines/black-box
"Black Box." CDs, Super Glue, and Salsa: How Everyday Products Are Made: Series 3. . Retrieved October 19, 2018 from Encyclopedia.com: http://www.encyclopedia.com/education/culture-magazines/black-box