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Blackbox technology – How do they work and what about the cloud?

I am not a pilot, I am not an expert on aircraft systems however I do have a technical background.   As a regular air traveller and after the recent Malaysian airways crash I asked myself :

1. How can authorities lose track of a Boeing 777 plane in an age when an iPhone can be located in seconds (Thanks Susan for inspiring me to think of this….)

2. Over the last several years, airlines have been installing satellite-based Wi-Fi systems for passenger entertainment that could also be used to facilitate data-streaming,  It’s bizarre that we technology so passengers can pay to watch live TV, access emails and call BUT these are still not utilised for safety purposes.

EC_IFE2_Wide.jpgImage from :

Setting the scene

According to reports : “On January 31, 2000, Alaska Airlines Flight 261 departed Puerto Vallarta, Mexico, heading for Seattle, with a short stop scheduled in San Francisco. Approximately one hour and 45 minutes into the flight, a problem was reported that the plane’s “stabiliser 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 on board were killed.”

With any plane crash, there are many unanswered questions as to what brought it down. The investigators turn to the airplane’s flight data recorder (FDR) and cockpit voice recorder (CVR), also known as “black boxes,” to find answers. According to records, 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.

In my experience as a passenger, many airlines are now regularly allowing the in seat charging of and use of mobile phones and have plane based WiFi (for example Ethiad).   I have recently flown on several long haul and short haul flights and connectivity is much improved.   The internal communications systems such as ACARS regularly  use data transmission so the technology is there and usable although would probably need to be upgraded.   The airlines may however object as although data storage is practically too cheap to measure, data bandwidth – especially on satellites, which would be required for coverage over oceans and the poles is expensive (about 60p per kilobyte).

Streaming the data?

Firstly cost.  These devices cost $10,000 and $15,000 …is  a cloud based solution viable at this cost?

Secondly, How much data does the black box (FDR/CVR) actually record?  88 operational parameters apparently.

The global Iridium network, which covers the entire globe with 66 orbiting satellites, could probably accommodate the bandwidth needed to transmit at the very least the 88 operational required parameters from the 8,000 or so commercial flights at any given moment. Krishna Kavi, a professor of computer science at the University of North Texas, estimates that the worldwide demand would be about 64 megabits per second (Mbps) and of this only a portion of which would have to be sent by satellite. Using different assumptions, Seymour Levine, an inventor who has devised his own telemetry, estimates the maximum bandwidth requirement for aeroplanes as being around 25 Mbps and the total storage requirement for a day’s worth of data at 100 gigabytes — a quarter of the speed of a fast broadband connection and less disk space than an iPod Classic.

This really is a poor use of technology….and one that I feel will need to be addressed after the current accidents ImageThe technology over time

Originally developed by David Warren from Australia (see the video  the black boxes recorded data on Magnetic Tape.  Currently they use use solid state technology.  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.

ImageSensors and the technology

The devices are powered by 28 V DC and use solid state technology.   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 less chance of something breaking during a crash.  Planes are equipped with sensors that gather data. There are sensors that detect things such as:

  • Time
  • Pressure altitude
  • Airspeed
  • Vertical acceleration
  • Magnetic heading
  • Control-column position
  • Rudder-pedal position
  • Control-wheel position
  • Horizontal stabilizer
  • Fuel flow

Magnetic-tape recorders can track about 100 parameters, while solid-state recorders can track more than 700 in larger aircraft.

Data from both the CVR and FDR are stored on stacked memory boards inside the crash-survivable memory unit (CSMU). In recorders made by L-3 Communications, the CSMU is a cylindrical compartment on the recorder (as shown above). 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.

Voice Recording in the cockpit

There are several microphones built into the cockpit to track the conversations of the flight crew. These microphones are also designed to track any ambient noise in the cockpit, such as switches being thrown or any knocks or thuds. There may be up to four microphones in the plane’s cockpit, each connected to the cockpit voice recorder (CVR).

Any sounds in the cockpit are picked up by these microphones and sent to the CVR, where the recordings are digitized and stored. There is also another device in the cockpit, called the associated control unit, that provides pre-amplification for audio going to the CVR. Here are the positions of the four microphones:

  • Pilot’s headset
  • Co-pilot’s headset
  • Headset of a third crew member (if there is a third crew member)
  • Near the center of the cockpit, where it can pick up audio alerts and other sounds

Most magnetic-tape CVRs store the last 30 minutes of sound. They use a continuous loop of tape that completes a cycle every 30 minutes. As new material is recorded, the oldest material is replaced. CVRs that used solid-state storage can record two hours of audio. Similar to the magnetic-tape recorders, solid-state recorders also record over old material.  (In the case of the Malaysian Airline  flight MH370 then I would assume this data may have been recorded over during its 7hr flight and miss vital recordings when the issues may have appeared 5hrs earlier?)

Locator Beacon

If a plane crashes into the water, the locator beacon sends out an ultrasonic pulse that cannot be heard by human ears but is readily detectable by sonar and acoustical locating equipment. There is a submergence sensor on the side of the beacon that looks like a bull’s-eye. When water touches this sensor, it activates the beacon.

The beacon sends out pulses at 37.5 kilohertz (kHz) and can transmit sound as deep as 14,000 feet (4,267 m). Once the beacon begins “pinging,” it pings once per second for 30 days. This beacon is powered by a battery that has a shelf life of six years. In rare instances, the beacon may get snapped off during a high-impact collision.

In the United States, when investigators locate a black box it is transported to the computer labs at the National Transportation Safety Board (NTSB). Special care is taken in transporting these devices in order to avoid any (further) damage to the recording medium. In cases of water accidents, recorders are placed in a cooler of water to keep them from drying out.

Getting the data off the device

The black-box manufacturers supply the NTSB with the readout systems and software needed to do a full analysis of the recorders’ stored data.  If the FDR is not damaged, investigators can simply play it back on the recorder by connecting it to a readout system. With solid-state recorders, investigators can extract stored data in a matter of minutes. Very often, recorders retrieved from wreckage are dented or burned. In these cases, the memory boards are removed, cleaned up and a new memory interface cable is installed. Then the memory board is connected to a working recorder. This recorder has special software to facilitate the retrieval of data without the possibility of overwriting any of it.

A team of experts are usually brought in to interpret the recordings stored on a CVR. This group typically includes a representative from the airline, a representative from the airplane manufacturer, an NTSB transportation-safety specialist and an NTSB air-safety investigator.

Benefits of using a more effective system would probably result in improvements in:

  • Communications – including that with Air Traffic Control
  • Surveillance improvements in case of accidents
  • Navigational improvements

Other options

Military airplanes and helicopters used in offshore exploration have flight-data recorders that can eject with a parachute in a crash. They emit a satellite signal that immediately transmit the aircraft’s identity and location. But adding an ejection system on a commercial jet would probably require an expensive redesign.


My prediction on the future for this technology

Simple enough, live data transferred from cockpit to stakeholders (Aircraft manufacturer to analyse data in real time, mechanics at airfields for maintenance, Air Traffic Control, NTSB and the airline).  A further more radical modification could be to remotely control the aircraft (using a one time key from aircraft to airline to ensure security and restrict hacking) brining it back to land on perform an emergency landing as necessary however electrical faults  may deem this impossible.

Probable issues:

  • Hacking of data  – potential terrorism?
  • Cost of bandwidth (rather than storage)
  • Infrastructure development for cloud technology or wireless data transfer
  • Backup systems and system redundancy
  • Connectivity in remote areas due to lack of network coverage (burst transmission –
  • Ethical collection of data for pilot performance management / recording of crew voice recordings
  • Pilots Association may not agree to this streaming (they also opposed the introduction of the black box!)


In a year or so I predict this data will be live streamed and stored in the cloud with redundant systems on board as needed initially this may start with triggered transmissions of data.  This would allow for more data to be stored and used for maintenance and be available immediately (unless this systems itself were to breakdown).  The better compression and encryption algorithms developed now mean there is no real reason why this would not be could not be used.   These systems are old and have not been developed taking account of newer internet enabled technologies.


Photos from : L-3 Communication Aviation Recorders

Further sources:,



About danbowen

Educational technology learning and teaching consultant, support, training, change management, innovation and all things ICT and educational, father of two, guitarist, welsh rugby follower,

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