04-06-2013, 03:26 PM
Black Boxes
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INTRODUCTION
If 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.
The black-box is a flight recorder which is used to record specific aircraft performance parameters. The first design of black-box is produced in 1953 by Dr. David Warren. It is used to help identify the reasons for a plane crash.
The aircrafts black-box is in fact orange in color and there may be two of them to record two streams of data, the cockpit voice recorders (CVR) and the flight data recorders (FDR).The recorders are made to withstand brutal sudden impacts, intense fire temperatures, and the crushing pressure of deep ocean depths.
The cockpits voice recorder is used to record voice and all sounds made within the cockpit. By listening to the conversations between people on the flight deck and conversations between the flight crew and cabin crew, ground crew, airport tower, and air traffic control, investigators can determine what the cockpit crew was doing and thinking up to the time of the crash.
DESIGN OF A BLACK BOX
The design of today's FDR is governed by the internationally recognized standards and recommended practices relating to flight recorders which are contained in ICAO Annex 6 which makes reference to industry crashworthiness and fire protection specifications such as those to be found in the European Organisation for Civil Aviation Equipment[10] documents EUROCAE ED55, ED56 fiken A and ED112 (Minimum Operational Performance Specification for Crash Protected Airborne Recorder Systems). In the United States, the Federal Aviation Administration (FAA) regulates all aspects of U.S. aviation, and cites design requirements i their Technical Standard Order, based on the EUROCAE documents (as do the aviation authorities of many other countries).
COCKPIT VOICE RECORDERS:
A cockpit voice recorder (CVR), often referred to as a "black box", is a flight recorder used to record the audio environment in the flight deck of anaircraft for the purpose of investigation of accidents and incidents. This is typically achieved by recording the signals of the microphones and earphones of the pilots headsets and of an area microphone in the roof of the cockpit. The current applicable FAA TSO is C123b titled Cockpit Voice Recorder Equipment.
Where an aircraft is required to carry a CVR and utilises digital communications the CVR is required to record such communications with air traffic control unless this is recorded elsewhere. As of 2005 it is an FAA requirement that the recording duration is a minimum of thirty minutes, but the NTSB has long recommended that it should be at least two hours
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 memory unit (CSMU). 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.
SOLID STATE RECORDER:
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.
BASIC COMPONET AND OPERATION OF AN AVIATION RECORDING SYSTEM
Both black boxes are powered by one of two power generators that draw their power from the plane's engines. One generator is a 28-volt DC power source, and the other is a 115-volt, 400-hertz (Hz) AC power source. These are standard aircraft power supplies, according to Frank Doran, director of engineering for L-3 Communications Aviation Recorders.
FLIGHT DATA RECORDERS:
The recorder is installed in the most crash survivable part of the aircraft, usually the tail section. The data collected in the FDR system can help investigators determine whether an accident was caused by pilot error, by an external event (such as windshear), or by an airplane system problem. Furthermore, these data have contributed to airplane system design improvements and the ability to predict potential difficulties as airplanes age. An example of the latter is using FDR data to monitor the condition of a high-hours engine. Evaluating the data could be useful in making a decision to replace the engine before a failure occurs.
GENERAL REQUIREMENTS FOR FLIGHT DATA RECORDERS
Recorder is supposed to record data during the flight without interruption. The case of
flight recorder is required to
• be coated with bright orange or white colour
• be treated with reflex material for high visibility
• be securely connected with automatically activated signalisation for localisation underwater
Recorder is required to be installed so that
• the probability of data damage is minimized
• is powered by electricity from the most reliable electrical bus
• is equipped with voice or visual features for verification of the correct operation during
BUILT TO SURVIVE:
In many airline accidents, the only devices that survive are the crash-survivable memory units (CSMUs) of the flight data recorders and cockpit voice recorders. Typically, the rest of the recorders' chassis and inner components are mangled. The CSMU is a large cylinder that bolts onto the flat portion of the recorder. This device is engineered to withstand extreme heat, violent crashes and tons of pressure. In older magnetic-tape recorders, the CSMU is inside a rectangular box.
SOLID STATE RECORDER:
Using three layers of materials, the CSMU in a solid-state black box insulates and protects the stack of memory boards that store the digitized information. We will talk more about the memory and electronics in the next section. Here's a closer look at the materials that provide a barrier for the memory boards, starting at the innermost barrier and working our way outward:
• Aluminum housing - There is a thin layer of aluminum around the stack of memory cards.
• High-temperature insulation - This dry-silica material is 1 inch (2.54 cm) thick and provides high-temperature thermal protection. This is what keeps the memory boards safe during post-accident fires.
• Stainless-steel shell- The high-temperature insulation material is contained within a stainless-steel cast shell that is about 0.25 inches (0.64 cm) thick. Titanium can be used to create this outer armor as well.
CONCLUSION
So, black box technology has moved from airplanes to automobiles -- where is it headed next?
There are improvements on the horizon for black box technology. Reportedly, some form of cockpit video recorder will be developed. Such a recorder would be able to store video images in solid-state memory.