[Avionics Today March 19, 2014] Malaysia Airlines Prime Minister Najib Razak clarified a statement released over the weekend regarding the disablement of the missing flight MH370 jet's Aircraft Communications Addressing and Reporting System (ACARS).
Flight MH370, a Boeing 777-200 traveling from Kuala Lumpur International Airport to Beijing Capital International Airport has been missing for 11 days now, with a search effort involving 25 different countries.
On Saturday, March 15, Razak issued a statement indicating that officials investigating the disappearance confirmed with a "high degree of certainty" that the ACARS system was disabled before the aircraft reached the east coast of peninsular Malaysia.
Tuesday, Razak clarified that statement. "We cannot determine exactly when ACARS had been disabled, only that it occurred within a specific time range: from 01:07 — approximately when the aircraft reached the east coast of peninsular Malaysia, and the last ACARS transmission occurred — to 01:37, which was the next scheduled reporting time. That is indeed the case," Razak said.
Investigators believe that someone in the cockpit switched off both the ACARS system and a separate radar transponder system and then somehow veered the aircraft off of its original flight path.
The transponder system that was reportedly switched off is used by Air Traffic Controllers (ATC) to track the aircraft with radar coverage. Transponders can be disabled with a switch on the cockpit panel.
ACARS is a component of the Flight Management System (FMS) that transmits data about the aircraft's performance throughout all phases of flight back to maintenance personnel on the ground. Disabling that system is a little more complicated and would require the removal of the circuit breakers that correspond with the ACARS.
According to officials involved in the investigation, the aircraft most likely continued flying for at least another 5 hours after those two systems were turned off. That is based on a satellite that continued tracking the aircraft's altitude and speed once per hour for another 5 hours after the two avionics systems were reportedly disabled.
What occurred after the last known radar contact with MH370 will remain unknown until officials can access the missing aircraft's flight data recorder.
"It is also important to recognize that the precise time ACARS was disabled has no bearing on the search and rescue operation. We know that the last known position of the plane as confirmed by the international investigations team was in either the northern or southern corridors, which is where our search and rescue efforts are focused," said Razak.