Shortly before EgyptAir Flight 804 began its plunge toward the Mediterranean Sea, the unit that monitors the airplane’s critical systems reported a rapid series of alarms indicating smoke in a lavatory and a breakdown of the flight control system.
The Herald says that it has information from three independent sources that seven emergency alerts were reported by the Airbus’s Aircraft Communications and Reporting System, ACARS, before all communications from the airplane stopped.
The sequence begins with the detection of problems with windows in the cockpit and with smoke in a lavatory.
A minute later, Greek air traffic control said it had tried to contact the plane’s pilots but they did not respond.
The most serious and instantly consequential warning indicates that there was a failure of the avionics that immediately affected the flight controls. This included the autopilot when it would have been flying the airplane at cruise altitude and almost immediately the problem spread to computers operating two critical control surfaces, the elevators at the tail and spoilers that control the airplane’s rate of descent.
The result of these failures would almost certainly mean that the pilots had no opportunity to regain control.
At the same time that the transponder and ACARS system quit sending information, Greek civil radar lost track of the plane.
It cannot be known whether this apparent fire was the result of a bomb or an accident unless and until physical evidence in the form of airplane debris and passengers bodies are collected.
It is significant that the Airbus’s ACARS reporting system is the only live link between the airplane and the ground that gives specific indications of an emergency. The messages are sent in bursts via satellite to the airline’s maintenance base—under normal conditions to indicate a problem that could need attention once the airplane lands.
It was ACARS that provided the first and eventually essential clues to a loss of control of Air France Flight 447 over the south Atlantic in 2009. In the absence of real-time live tracking of airplanes, a scandalous state of affairs, ACARS becomes vital to investigators in a situation like the crash of the EgyptAir 320 where the remains of the airplane can be beyond reach for weeks or even years.