Saturday, March 22, 2014

The need to invent Secondary Data Recorders for Aircraft

The tragic incident of the Malaysian Airlines MH370 has triggered a worldwide question. Why don't we have better data and cockpit voice recorders? Rep. David Price, D-N.C., is reported to have said that the 9/11 Commission recommended after the terrorist hijackings in 2001 that planes carry ejectable "black boxes" to make them easier to find. Visit

It is not very easy to design an electable data recorder. I wish to stimulate a number of student inventors/designers to think about this challenge with this blog post, by discussing a number of issues involved.

The first question is about the conditions that should trigger ejection of the recorder. In a military aircraft, this could be when the pilot bails out using an ejection seat. Not in a civilian aircraft. Actual impact, particularly over water, might be too late a moment for the data recorder to eject; it might sucked deep into the water with the falling structures and get trapped under water.  A moment of high deceleration might indicate breaking up of the aircraft in mid-air. An impact will also cause a high level of deceleration.

Innovation requires trying out a variety of designs, without incurring a prohibitive cost. Integration of the device with the aircraft's systems will make these trials process very expensive. So, it might be worth trying out an externally mounted device not integrated with the avionics of the aircraft.  If this prevents cockpit voice recording, one can perhaps do without it to start with. Alternatively, one could try and have the cockpit voice signal sent to the recorder securely over an encrypted WiFi like transmission.

A possible option is that of a device that clings to the external surface of a plane and can fall off after ejecting, to float if it falls into a water body, and sends wireless signals irrespective of where it lands.

How would a device cling to the exterior of a plane when it has air flowing over it at a high speed? One option would be to use the power of the air rushing past the shell of the device to make the device cling tighter to the aircraft. A pitot tube mechanism could create a low pressure area inside the shell, making it cling tightly to the aircraft's surface. Plastic bolts or a magnetic device could provide for the primary attachment to the aircraft, with the partial vacuum created by the moving air providing an additional mechanism to bind the device to the aircraft. Ejecting the device would involve opening a valve that depletes the vacuum. It might also require a mechanical device that cuts or breaks the plastic bolt when necessary.

An external device can easily measure altitude as indicated by air pressure, as well as airspeed. Electronic accelerometers could add data about acceleration in three dimensions, and GPS coordinates as a function of time.

To save battery life, the ejected device may send wireless signals relatively infrequently. It could be designed to respond to polling signals sent by search aircraft or ships, like a transponder. The device might also have built-in solar cells to keep sending signals over weeks or months.

Given all the above-mentioned possibilities, it seems the time is ripe to launch several design projects. A design competition, with an attractive price, may be a good idea.

Having an aircraft sending data more or less continuously is not a bad solution. However, constant search for alternative solutions is necessary till all aircraft are fitted with affordable data recording devices.

Lastly, automobiles can also benefit from data recorders, even if they are not ejectable. Perhaps insurance companies should drive their use by offering lower insurance costs to cars fitted with working and regularly monitored data recorders. Automobile data recorders would have a moderating effect on drivers and make them less risk-prone.

Srinivasan Ramani


Srinivasan Ramani said...

The absence of technology to quickly locate the flight data recorder and the cockpit voice recorder of the MH370 is surprising. A submersible drone to search for underwater signals takes weeks to get there. When it does get there, it will be the only one of its kind deployed and will have only a few days to detect the signal before the batteries of the blackboxes run out.

Why can't one airdrop several modified Tsunami Buoys to do a quick job?
Visit: Deep Ocean Tsunami Detection Buoys

If the current version of Tsunami Buoys are very expensive, we should design less expensive disposable underwater listening devices that can be air-dropped, for use in future.

Srinivasan Ramani

ajay singh said...

Worth reading sir

Srinivasan Ramani said...

A few governments have now made it mandatory for airlines to subscribe to a satellite channel data link service to regularly report aircraft positions.

A description of one such system can be seen at
Aircraft Communications Addressing and Reporting System

There are companies offering the use of shortwave data links as well. Visit:
HFDL (High Frequency Data Link)
Shortwave signals do not offer 100% reliable connections all the time. However, since shortwave signals can be monitored at multiple locations around the world and can be automatically processed, overall system reliability can be quite high. Besides automated aircraft position reporting is repeated every 30 seconds.

Srinivasan Ramani

Srinivasan Ramani said...

This importance of this issue has been highlighted recently by the loss of an Indian Air Force AN 32 over the Bay of Bengal.

No Clue Of Air Force's AN-32 Plane As Search Goes Into Third Day

A Dornier operated by the Indian Coast Guard had been lost over the Bay of Bengal in 2015.