Howstuffworks _How Black Boxes Work

describes how black boxes in aircrafts work
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  Howstuffworks How Black Boxes Work   Computer Stuff  Auto Stuff  Electronics Stuff  Science Stuff  Home Stuff  Stuffo Health Stuff  Money Stuff   Travel Stuff  People Stuff   Main > Travel > Travel Safety  Click here to go back to the normal view! How Black Boxes Work by Kevin Bonsor  Special thanks to L-3 Communications, Aviation Recorders Division, for its help with this article. On January 31, 2000, Alaska Airlines Flight 261  departed Puerto Vallarta, Mexico, heading for Seattle, WA, with a short stop scheduled in San Francisco, CA. Approximately one hour and 45 minutes into the flight, a problem was reported with the plane's stabilizer trim . After a 10-minute battle to keep the plane airborne, it plunged into the Pacific Ocean off the coast of California. All 88 people onboard were killed. (1 of 16)2/4/2003 1:55:32 AM Search HowStuffWorks and the Web  Howstuffworks How Black Boxes Work Photo courtesy U.S. Department of Defense The cockpit voice recorder from the downed Alaska Airlines Flight 261, held by the robotic arm of the remotely piloted vehicle that retrieved it With any airplane crash, there are many unanswered questions as to what brought the plane down. Investigators turn to the airplane's flight data recorder   (FDR) and cockpit voice recorder   (CVR), also known as black boxes, for answers. In Flight 261, the FDR contained 48 parameters of flight data, and the CVR recorded a little more than 30 minutes of conversation and other audible cockpit noises. Following any airplane accident in the United States, safety investigators from the National Transportation Safety Board (NTSB) immediately begin searching for the aircraft's black boxes . These recording devices, which cost between $10,000 an $15,000 each, reveal details of the events immediately preceding the accident. In this article, we will look at the two types of black boxes, how they survive crashes, and how they are retrieved and analyzed. Recording and Storage The Wright Brothers  pioneered the use of a device to record propeller rotations, according to documents provided by L-3 Communications. However, the widespread use of aviation recorders didn't begin until the post-World War II era. Since then, the recording medium of black boxes has (2 of 16)2/4/2003 1:55:32 AM  Howstuffworks How Black Boxes Work evolved in order to record much more information about an aircraft's operation.  Although many of the black boxes in use today use magnetic tape , which was first introduced in the 1960s, airlines are moving to solid-state memory boards , which came along in the 1990s. Magnetic tape works like any tape recorder . The Mylar tape is pulled across an electromagnetic head, which leaves a bit of data on the tape. Photo courtesy National Transportation Safety Board (NTSB) The magnetic tape inside the flight data recorder from EgyptAir Flight 990, which crashed on October 31, 1999 Black-box manufacturers are no longer making magnetic tape recorders as airlines begin a full transition to solid-state technology. Let's take a look at solid-state technology. Solid-state Technology Solid-state recorders are considered much more reliable than their magnetic-tape counterparts, according to Ron Crotty , a spokesperson for Honeywell, a black-box manufacturer. Solid state  uses stacked arrays of memory chips, so they don't have moving parts. With no moving parts, there are fewer maintenance issues and a decreased chance of something breaking during a crash. Data from both the CVR and FDR is stored on stacked memory boards  inside the crash-survivable (3 of 16)2/4/2003 1:55:32 AM  Howstuffworks How Black Boxes Work memory unit  (CSMU). In recorders made by L-3 Communications, the CSMU is a cylindrical compartment on the recorder. The stacked memory boards are about 1.75 inches (4.45 cm) in diameter and 1 inch (2.54 cm) tall. The memory boards have enough digital storage space to accommodate two hours of audio data for CVRs and 25 hours of flight data for FDRs.  Airplanes are equipped with sensors that gather data. There are sensors that detect acceleration, airspeed, altitude, flap settings, outside temperature, cabin temperature and pressure, engine performance and more. Magnetic-tape recorders can track about 100 parameters, while solid-state recorders can track more than 700 in larger aircraft.  All of the data collected by the airplane's sensors is sent to the flight-data acquisition unit  (FDAU) at the front of the aircraft. This device often is found in the electronic equipment bay  under the cockpit. The flight-data acquisition unit is the middle manager of the entire data-recording process. It takes the information from the sensors and sends it on to the black boxes. Source: L-3 Communication Aviation Recorders Basic components and operation of an aviation recording system (4 of 16)2/4/2003 1:55:32 AM
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