PARIS • France's aviation safety agency said yesterday that the EgyptAir A-320 that crashed on Thursday into the eastern Mediterranean with 66 people on board had transmitted automatic messages indicating smoke in the cabin.
The messages were transmitted through the Aircraft Communications Addressing and Reporting System (Acars), a digital system that transmits short messages between aircraft and ground stations.
The disclosure by a spokesman for France's Bureau of Investigations and Analysis came after a respected aviation journal, Avherald, on Friday published details about the last minutes on the plane based on the Acars transmissions.
The data is written tersely in abbreviations and codes.
They revealed a rapid loss of control, with alarms and computer-system failures just before the plane was lost from radar.
1.48am (Cairo time)
The Hellenic Civil Aviation Authority says the flight was proceeding normally when Greek traffic controllers last spoke with the pilot of Flight MS804, who seemed in good spirits.
An Acars message indicated that the plane's right cockpit window had been opened. This could have been done to vent smoke, according to Mr Robert Mann, a former airline executive and an industry analyst, or something else could have caused the breach.
Between 2.26am and 2.28am
There were two smoke indications, one in a bathroom and another in the avionics bay, the part of the plane where much of its electronic equipment is housed.
Mr Mann cautioned that these messages did not necessarily mean there was a fire.
The messages could also have been prompted by rapid decompression of the aircraft, which can produce condensation that the plane's sensors could mistake for smoke.
There were two more alerts having to do with the plane's flight control computer systems.
First, there was a problem with the autoflight control computer. The jet would have been flying near its maximum speed and elevation at that time.
That is the most efficient way for jetliners to fly, and it is safe, Mr Mann said, but pilots prefer to rely on autopilot systems in those conditions because if they were ever to lose control of the plane, it could be hard to regain. That is why pilots sometimes call those conditions the "coffin corner", he said.
The last message had to do with the spoiler elevator controller, which essentially controls the flaps responsible for pitch and roll control. The computer controlling these failed as well.
"It looks to me like you have a progressive flight control system failure," Mr Mann said.
The plane left Greek airspace, and Greek controllers lost the aircraft's trace just inside Egyptian airspace, about halfway between Crete and Egypt. Around this time, the Airbus A-320 made a 90-degree turn to the left and then a full circle to the right, dropping precipitously to 15,000 feet from 37,000 feet and then plunging again to 9,000 feet before it disappeared from radar.
The crew never gave any indication of a technical problem or other difficulties on board, even during the final, fatal minutes when the plane itself was transmitting data indicating a catastrophic failure.
Experts noted that the short sequence of Acars messages provided no clue on what may have caused the smoke or fire aboard, no insight into pilot efforts to control the aircraft, nor does it show whether the plane fell in one piece or disintegrated in mid-air.
Those answers will only be forthcoming when investigators find the remains of the aircraft and its two flight recorders containing cockpit voice recordings and data readings.
NEW YORK TIMES, AGENCE FRANCE PRESSE, REUTERS