The original Black Box was Designed by David Warren< In 1953 Warren come up with the idea of an onboard Flight Data Recorder
A flight recorder is an airplane’s Digital Flight Data Recorder (DVDR) and Cockpit Voice Recorder (CVR) installed as one unit. "Black box" is the common name used in news stories. Despite this fact, 'black boxes' are almost always orange, to make them easier to see in wreckage.
The original model was red, although these days they are usually orange to make them easier to find. A journal list at the launch described it as a “wonderful black box” to make the point that how it worked was complex and one didn’t really need to know, but that it worked was the important thing
As this data is collected for the Flight Computers, some or all of the data is transferred to the FDR for storage. The FDR records the data for 30 minutes(on most aircraft) and then begins to re-write over it.
The other device that is used for accident investigation is the Cockpit Voice Recorder. This system is a set of microphones in the cockpit that records the crew conversation and any sounds. The CVR is useful in case the pilots say something that is not transmitted over the radio. Or it can pick up sounds of the warning bells and whistles. Sometimes it can pick up sounds outside the aircraft, especially if it is something like an explosion.
The black box records data from the plane's instruments (altitude, speed, pitch etc) the cockpit radio transmissions (between pilot & co-pilot and control tower) and the external weather conditions. It is usually housed in the planes tail area (if it's gonna crash it'll go in nose first !)
How Black Boxes Work
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.
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.
Few parameters recorded by most FDRs:
- Time
- Presure Altitude
- Airspeed
- Verticle Accelaretion
- Magnetic Heading
- Control Coloum Position
- Rudder Pedak Position
- Control Wheel Position
- Horizontal Stabilizer
- Fuel Flow
Advantages of Black Box
- Black box tests are reproducible
- The environment the program is running is also tested
- The invested effort can be use multiple time
- Tester can be non-technical.easy to understand the process
- Used to verify contradictions in actual system and the specifications
- Test cases can be designed as soon as the functional specifications are complete
Disadvantages of Black Box
- The reason for failure not found, The result are often overestimate
- The test inputs needs to be from large sample space
- It is difficult to identify all possible inputs in limited testing time. So writing test cases is slow and difficult
- Chances of having unidentified paths during this testing
- It consumes lot of time and human resource
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