Communications:MH370 Communications

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Some Background Comments

An understanding communications systems is essential for the narrative of Malaysia Airlines Flight MH370.

The aircraft, a Boeing 777-200-ER, had several communications systems all of which were functioning during the pre-flight phase and the flight segment from Kuala Lumpur to the vicinity or a waypoint IGARI located over the south China Sea near the boundary between airspace controlled by Malaysia and Vietnam.

This includes voice and data communications via VHF radios operated by both the Pilot-in-Command and the First Officer plus another radio transceiver interface accessible to either of them; satellite communications used for data but capable of telephone calls; secondary radar which uses a transponder to send position information to air traffic controllers; and a system known as ADS-B which also transmits identity and position information.

After the diversionary turn made near waypoint IGARI there was no communication from the aircraft until it was located well away from Malaysia, above the Andaman Sea. Even the automated systems, the secondary radar transponder and the ADS-B system were inactive.

It is normal, in event of any on-board problem, for the flight crew to communicate with air traffic controllers. Depending on the severity of the issue a call could be prefixed with the words Pan Pan or Mayday. From MH370, however, there was silence.

It is also normal, in event of a hijack or similar in-flight event, for the transponder code to be changed to indicate the nature of the threat. But the transponder on MH370 was also inactive.

There are also established procedures for an event such as communications failure, as might occur as a consequence of an electrical system failure. This can include flying in a pattern which is supposed to alert air traffic controllers. But as MH370 went silent nothing like this was observed.

As at least one journalist commented, everything was normal, until it wasn't. Initially, conjecture included theories such as a fire, a catastrophic electrical failure, or an unconscious flight crew, ideas that preceded the knowledge that the aircraft continued to be airborne for many hours and made a series of turns which would have been deliberate by a fully conscious pilot. So the alternative perspective is that the systems were deliberately disabled, inactivated or consciously unused. The actions would be consistent with a rogue pilot theory, but to be successful the other pilot would have to be complicit, disabled or prevented from intervening.

A rarely expressed scenario is that these systems were inactivated by use of force or coercion by a 'third party' and the pilots were prevented from using radio and other means of communications. The event at 0225:27 MYT is an interesting anomaly. Why did the satellite data unit (SDU) on MH370 initiate a log-on sequence with the Inmarsat satellite?