The introduction of constant tracking of commercial aircraft during the whole journey has been raised by Malaysian authorities in a preliminary report into missing flight MH370.
Geoffrey Dell is an Associate Professor/Discipline Leader Accident Investigation and Forensics at Central Queensland University. This post originally appeared on The Conversation.
It’s been two months now since Malaysian Airlines Boeing 777 was declared missing on March 8 and search and rescue authorities are still no closer to locating any potential crash site or finding any actual wreckage.
The five-page report released last week by the Malaysian Government details some of the efforts being taken to find the missing flight over a wide area, including extending the search to the Southern Indian Ocean.
It doesn’t mention by name but refers to the two-year search for wreckage of the Air France 447 Airbus jet that disappeared into the Atlantic between Brazil and Africa in 2009.
There have now been two occasions during the last five years when large commercial air transport aircraft have gone missing and their last position was not accurately known. The report then says the Malaysian Air Accident Investigation Bureau recommends that the International Civil Aviation Organisation (ICAO) looks at the potential safety benefits of real-time tracking of all transport aircraft.
This would involve establishing a means of tracking aircraft even when they are outside of established radar coverage.
It would not be practical or cost effective to extend surface based radar coverage to include all the world’s oceans, so tracking aircraft positions mid ocean would doubtless have to include monitoring by satellite.
Can’t GPS help?
Unfortunately global positioning satellite (GPS) technology such as that used by the common smartphone (or in car navigation systems) could not be used for this.
That technology involves only one-way transmissions from the GPS satellite constellation which are received by the phone. This allows the phone to work out its geographical location with considerable accuracy but the GPS system does not have any information on the actual location of the phone.
For any real-time location technology to work there must be two-way communication in order for the system to know where the receiver actually is.
So, probably the cheapest and simplest way to achieve this would be for each aircraft to “ping” a satellite periodically, say once a minute, with a packet of information that includes the aircraft’s altitude, latitude and longitude.
Continuous communication would be most beneficial to establish the location of any potential crash site but it would also most probably be too cost prohibitive, so once a minute or so would be a compromise without impacting too much on knowing the actual aircraft location.
Any such real-time tracking system would no doubt also mean the launching of additional satellites to ensure global coverage, so the costs of implementation would not be insignificant in any case.
Most of the modern passenger transport aircraft already have the capability to transfer data back to the ground via satellite, although the communication is not continuous.
The Aircraft Communications Addressing and Reporting System (ACARS) allows technical information from the aircraft – such as engine performance data – to be automatically sent back to the airline. In return the airline uses the system to send operational information – such as flight planning information and other advisories – to the pilots.
Flight MH370 was fitted with ACARS. Even though it may have been disabled during the flight the Malaysian report says it was still “logged on to the network”. That means the system was pinging a satellite periodically throughout the flight.
It was the Doppler effect on six of these signals which has been the basis for the Inmarsat analysis which indicated the aircraft possibly flew south west toward the Southern Indian Ocean.
Why not transmit the black box data?
If real-time tracking is to be developed and implemented then consideration should also be given to the routine transmission of key flight data recorder parameters at the same time.
Modern digital flight data recorders can record upwards of 2,000 parameters so cost and bandwith might be a barrier to transmitting all the information.
But the transmission and remote storage of key flight data such as altitude, airspeed, heading, engine power, fuel remaining, vertical, lateral and longitudinal acceleration and flight control, flap and undercarriage positions would be very useful in cases such as MH370.
There would still be a need to locate the wreckage for moral and humanitarian reasons. But theoretically the more flight data transmitted and stored remotely from the aircraft, the lesser the need to recover the flight recorders.
This would also allow a more comprehensive crash investigation to begin even before the physical site of a crash was located.
But I can foresee issues being raised by flight crew associations globally relating to confidentiality and potential misuse of the data sent from the aircraft, especially if it was to include encrypted and compressed audio files of recorded cockpit voice recorder data.
There is little doubt that as the search for MH370 continues without finding evidence of the actual site of the wreckage, and the associated search costs continue to rise, changes to air safety will be made.
Already there is a suggestion to increase the duration of the recording time of the cockpit voice recorders from two to 20 hours.
The emphasis on looking for alternate means of tracking transport aircraft, and the interest in establishing systems for routine transmission and remote storage of flight data, will also grow within governments globally.