Why Do Airplanes Need Black Boxes?
When there is an aircraft incident, search workers and investigators first look for the black boxes. A black box is an umbrella term used to distinguish two integral pieces of equipment within aircraft, those of which include the cockpit voice recorder (CVR) and the flight data recorder (FDR). Together, these devices provide inflight data that can reveal why an aircraft incident occurred.
Usually located in the aircraft’s tail, where they are more likely to survive a crash, black boxes provide critical data about an aircraft’s operation. Black boxes, or flight recorders as they are also known, surfaced after WWII. Since their development, black boxes have become commonplace in commercial aircraft across the globe.
Pioneered in the 1950s by Dr. David Warren after his father died in a plane crash when Warren was only six, he would come to develop a way to record flight data and cockpit conversations to help investigators following a crash. His invention was known as the “ARL Flight Memory Unit,” and it would become mandatory on all commercial aircraft by the 1960s.
With technological advancements in the aviation realm, black boxes have seen much improvement. Today, flight recorders come in two varieties, each collecting several pieces of integral data. The FDR tracks every instruction made by pilots and commands sent through electronic systems to other relevant components. Meanwhile, the CVR documents general noises such as voices in the cockpit and audible warnings. The FAA requires that CVRs record at least 2 hours of audio.
Both of these devices provide vital pieces of information that allow investigators to piece together the timeline of any given accident. Beyond being located at the tail where they can survive a crash, they are also fitted with locator beacons. These beacons can broadcast their location for up to 30 days, even if they are submerged 20,000 feet below water.
While the term used to describe these flight recording instruments suggests that they may be black, in reality, they are actually painted orange for ease of identification. More than that, they have reflective surfaces on their exterior to increase their visibility. On opposite sides of the box, you will see the words “Flight Recorder Do Not Open.”
As aircraft accidents are typically catastrophic, the only devices that usually survive are the crash-survivable memory units (CSMUs) of the FDRs and CVRs. Other than that, the rest of the recorders’ casing and inner components usually get damaged. The CSMU is a large cylinder that is bolted onto the flat section of the recorder, and it is engineered to handle extreme heat, violent crashes, and loads of pressure.
Older versions of CSMUs were contained in solid-state black boxes that were insulated using three different materials. These layers protected the stack of memory boards that store the digitized data. The innermost layer consisted of an aluminum housing, the second layer was a high-temperature insulation material such as dry-silica, and the last layer was a stainless-steel shell made of titanium. Today, engineers use similar parameters to construct black boxes, ensuring that the end-product can withstand extreme abuse.
To guarantee the survivability of black boxes, manufacturers thoroughly vet CSMUs. In order to test the unit, engineers load sample data onto the memory boards within the CSMU, and they subject it to various scenarios. In fact, there are several tests that make up the crash-survival sequence, those of which include crash impact, pin drop, static crush, fire test, deep-sea & salt-water submersion, and fluid immersion.
During the fire test, the memory interface cable that connects the memory boards to the circuit boards is typically burned away. As such, researchers must wait for the unit to cool down to pull the memory module out. Once this is accomplished, they can restack the memory boards, install a new cable, and attach the unit to a readout system to confirm that all of the preloaded data is accounted for.
Though black boxes have proved effective on countless occasions, there are many potential improvements for black box technology in the future. One of the biggest upgrades engineers are looking to incorporate is video recording cockpit activity. However, it is the pilots that continuously refuse to allow video, emphasizing that such features violate their privacy and highlight that the current system provides ample data.
That being said, black boxes are clearly not going anywhere. Instead, the aviation industry will continue to improve on such systems, allowing airlines to gather pertinent information about aircraft. Beyond black boxes, there are many other parts that are paramount to aircraft functionality, some of which eventually necessitate replacement.
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