Authorities are still struggling – nearly one week later – with how Malaysia Airlines flight MH370 vanished about an hour after takeoff on a flight from Kuala Lumpur to Beijing, with 239 passengers and crew.
Airliners follow standard “airways” that define preferred routes between key points, and are tracked along the way by air traffic control (ATC) via position reporting by VHF radio, and by radar.
ATC radar has two ways of working: “passive” radar, in which the ground station simply sends a pulse and calculates distance by the time for the echo to bounce off the aircraft; and active, where the aircraft’s “transponder” sends its own signal each time it detects an incoming radar pulse.
The transponder signal contains a four-digit code that uniquely identifies the aircraft with its altitude and position on the ATC display. Further radar monitoring is generally performed by the military.
But modern aircraft such as this have several other communication systems. These include the Aircraft Communications Addressing and Reporting System (ACARS), a data reporting system using the Inmarsat satellite network, and the Rolls Royce engine data system, a key innovation by the British jet engine manufacturer.
During flight diagnostic, information on the aircraft’s two Trent 800 engines, such as temperatures or oil pressure, is collected and transmitted in bursts via the satellite system back to Rolls Royce’s 24 hour monitoring centre in Derby.
While not replacing the on-board cockpit instrumentation, this system is able to monitor 3,000 engines in real-time to interpret trends in engine parameters, which helps the company deliver improved maintenance to airlines and better plan availability of parts and replacements.
Rolls Royce claims that the growing sophistication of these predictive maintenance tools has resulted in increased capability for potential technical issues to be caught before they become disruptive and costly problems for the airline.
However, these multiple communication systems have so far failed to give a clear indication of the whereabouts of the plane. Officials said the plane's data reporting system shut down at 1:07am on Saturday, while the transponder transmitting location and altitude shut down at 1:21am. They now believe that the plane could have flown for several hours beyond the last transponder reading.
With two separate communications systems stopping only 14 minutes apart, "this is beginning to come together to say that…this had to have been some sort of deliberate act [and not a catastrophic failure]”, ABC News aviation analyst John Nance told CNN.
In the event of a crash, there is an Emergency Location Transmitter (ELT) that sends a distress signal automatically upon immersion in fresh or salt water. Then there is the “Black Box” recorder (actually orange) located in the tail of the aircraft, which is designed to survive a crash and immersion, and send its own emergency locator signal.
However, neither signal was received, and the failure of the beacons to activate could mean that the plane didn't crash, that the transmitter malfunctioned, or that it is underwater somewhere (it must remain on the surface for a distress signal to transmit).
There is considerable confusion on how to interpret the various signals that were received from MH370. The Wall Street Journal reported that the aircraft continued to send “pings” (saying “I'm here, I'm ready to send data") to the Inmarsat satellites for up to four hours after its last transponder position.
The WSJ said that these confirmed that the plane was moving, and the final ping was sent from over water at what was described as a normal cruising altitude. It added that it was unclear why the pings stopped. One industry official said it was possible that someone on board had disabled the system sending them.
However, Rolls Royce has denied reports that the jetliner was sending engine data for some five hours after it lost contact with the main control tower. The Malaysian government also denied this report, as did a senior aviation source, who also said that there was no technical data suggesting the airplane continued flying for four hours, and said specifically that the WSJ account was wrong.
It seem likely that the ACARS system was continuing to ping the satellites to maintain contact, but that no data (particularly from the engines) was sent.
It is extraordinary – in this age of the Internet of Things – that modern technology has so far failed to locate the Malaysian airliner, and that for up to five hours after the ATC lost contact nobody knows if it was still flying or not.
The search radius in this case is determined, in the absence of better information, purely by the maximum distance the fuel on board enables the plane to fly – hardly much of an advance in the last 50 years. And our failure to detect any problem earlier has thus vastly increased the search area and thereby reduced the probability of successfully locating the aircraft.
Despite having multiple systems that use different communication methods, there are no clear conclusions that can be drawn from their content. Despite their sophistication, these different systems were never designed to work together, and so they present a challenge to the task of constructing a “joined-up” picture of events.
Furthermore, most were also designed in a different era – making many of the on-board systems vulnerable to being intentionally disabled by a hijacker, and rendering the aircraft practically invisible to the authorities.
Whatever the conclusion to the mystery of MH370, let us hope that this incident may provide a spur to the aviation authorities and equipment manufacturers to accelerate the development of new systems that provide a more integrated, robust and secure approach to monitor commercial flights.
Sourced from Mike Fish, private pilot and navigator, and CEO of BigData4Analytics