What are Flight Recorders/Black boxes ?



One of the most frequently used tech-word we hear from the media after a  flight crash is “Black box”. Well, many of the people don’t even know that Black boxes aren’t“black”.  Do you really know about them enough ? If not, here’s everything you need to know about Black boxes/Flight recorders .

What are Flight recorders ?

Flight recorders are devices placed in every aircraft for the purpose of facilitating the investigation of aviation accidents/crashes.

The Flight Data Recorder(FDR) :-

Flight Data Recorder(FDR) is a type of electronic recording device which records dozens of parameters collected several times a second during flight. The  sensors located in an aircraft records various parameters.(Know what is the best thing about FDRs later at the end of this article 🙂 )

The Cockpit Voice Recorder(CVR) :-

Unlike flight data recorder, the cockpit voice recorder records the sounds that occur in the cockpit. The main purpose of this was to monitor what the crew members say during the flight.
Both – the FDR & CVR are placed or mounted in the tail section or the rear fuselage section of the aircraft to maximize the chances of survival during a crash.



History of flight recorders :-

The flight recorder was invented & developed by an Australian scientist – David Warren whose own father was killed in a plane crash in 1934. Warren was working in the Aeronautical Research Laboratory in Melbourne & he was one of the lead investigators of crash of the worlds first jet powered commercial aircraft – the Comet. This realised him that the task of finding the reason behind the crash would have been more easier if there was some kind of recording device. A device which could record things of what exactly happened on the plane just before the crash.

David Warren with the later version of flight recorders.

David Warren with the later version of flight recorders. source:- wired.com

This led to the development of flight recorders & first demonstration of the unit was given in 1957. Also Australia became the first country to make flight recorders mandatory for all aircrafts in 1960.
One of many explanations behind the popularization of the term “black box” comes from the early film-based design of flight data recorders, which required the inside of the recorder to be perfectly dark to prevent light leaks from corrupting the record, as in a photographer’s dark room.

More about FDRs :-

FDRs also called as ADRs(Accident Data Recorders) as discussed above, are used to record numerous parameters & instructions given to any electronic system on any aircraft. A minimum of 88 parameters are required under US federal regulations (only 29 until 2002). These parameters include altitude, airspeed, time, direction to which the plane is heading, engine temperatures & much more. Some of the FDRs are even capable of recording more than 1000 on-flight charecteristics(that too several times a second; now that is so COOL). These may include actuator positions, flap positions, wing angles, position of tail/rudder, various guages in the cockpit & also the auto-pilot mode is monitored.

FDRs are coated with high heat resistant & bright orange colored paints to have better visibility in the heap of wreckage after crash.
They are typically wrapped in strong corrosion resistant stainless steel or titanium so that nothing goes wrong with it even after getting submerged in deep sea water. Source

Specifications :-

Time for which parameters can be recorded         –          25 hour continuous
Number of parameters that can be recorded         –        18 – 1000+
Impact tolerance                                                            –        3400gs / 6.5 milliseconds (33km/s^2)
Temperature it can withstand                                    –         1100 °C
Water pressure resistance                                           –        submerged 20,000 ft
Underwater Locator Beacon                                       –        37.5 KHz; 30-day 90 day operation capability upon activation (reason for the strikethrough is discussed later in the article)

What is Underwater Locator Beacon(ULB) ?

An ULB having operational capability of 90 days.

An ULB having operational capability of 90 days. source:- ainonline.com

Underwater Locator Beacon(ULB) is a device accompanied with FDRs & CVRs which helps in locating itself(recorders) in case of an overwater accident. Also called as “pinger”, the device emits high frequency ultrasonic pings. These pings are recieved by a special reciever & thus the beacon could be found.
The beacons could transmit from depths down to 14,000 feet. It operates at frequency of 37.5 KHz & could transmit signals for 30 days 90 days after activation.



More about CVRs :-

The CVRs not only record the sounds that occur within the cockpit but also the audio environment in the flight deck of the airplane. Besides the radio conversation of crew members, other sounds included are sound of the engines, landing gear extension & retraction, an explosion, system failures, stall warnings or any other warnings given by the auto-pilot.
The original requirement of a CVR was to record 30 minutes before the end but it proved to be insufficient in some cases(earlier CVRs which used analog magnetic tapes). Thus the recording capacity of CVR was increased to 2 hours.

Specifications :-

Time for which sound could be recorded       –    30 min continuous, 2 hours for solid state digital units
Number of channels                                            –    4
Impact tolerance                                                   –    3400gs / 6.5 milliseconds (33km/s^2)
Fire resistance                                                       –    1100 C / 30 min
Water pressure resistance                                  –    submerged 20,000 ft
Underwater locator beacon                               –    37.5 KHz; 30-day 90-day operation capability upon activation

After disappearnce Malaysia Airlines Flight MH370 –

The disappearance of the flight MH370 showed up the limitations of flight recorders. The new requirements of a flight recorder was introduced.

  • Earlier, a physical possession of the FDR was necessary for retrieving the data parameters. Since the disappearance of flight 370, considering the advanced communication technology; the data is live streamed from aircraft to ground.
  • The battery life/operational capability of the Underwater locater beacon(ULB) has been increased from 30 days to 90 days !

The best thing about flight recorders

The best thing about flight recorder is that once the data is retrieved from the FDR, it can be used to generate a computer animated/simulated video of the flight until the aircraft crashes. This gives a clear visualization of the last moments of the flight before the mishap.
Playing the sound recordings from the recovered CVR simultaneously with the animated video tells us exactly about what happened on the flight. 
The computer simulated video helps the investigators to find the probable cause of the crash. Flight recorders really are proving to be a boon to the investigators.

By the way, what do you think about missing flight 370? An alien invasion 😛 ?
Let us know your thoughts in the comment section below. Always up for a healthy discussion 🙂

 

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