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Data Points to Rapid Loss of Control Aboard EgyptAir Jet

A piece of luggage adrift in the Mediterranean Sea. Floating nearby, a passenger seat from a plane. Scraps of metal, scattered personal belongings and, finally, the grim discovery of human remains.

As the investigation continued Friday into what caused an EgyptAir flight from Paris to Cairo to suddenly and violently plunge from the sky, the discovery of the debris allowed search crews to home in on the location of the crash — an area about 180 miles north of Alexandria, Egypt — even as its cause remained a mystery and the subject of intense speculation.

EgyptAir Jet Crush

Data that was transmitted from the aircraft to operators on the ground, published Friday by a respected aviation journal, revealed a rapid loss of control, with alarms and computer-system failures in the seconds before the plane was lost from radar.

The transmissions are evidence of a catastrophic failure, but do not answer the crucial question: What caused it? Why would a plane with a good safety record and experienced pilots fall from the sky on a clear spring night?

No bulk wreckage has been found, and the parts of the aircraft most likely to provide clues for investigators — including the voice and data recorders — are also the ones most likely to quickly sink to the seafloor.

An Egyptian official has said that investigators consider terrorism to be one possible cause of the disaster, but no terrorist group has claimed responsibility. Officials cautioned that there was no direct evidence to suggest a bomb aboard the plane, or any other deliberate act of sabotage.

The plane, a twin-engine Airbus A320 jet, went down Thursday while flying through a cloudless night sky en route to Cairo from Paris.

The Hellenic Civil Aviation Authority provided what a spokesman called a definitive timeline on the disaster. The agency reported that the flight was proceeding normally at 1:48 a.m. Cairo time on Thursday, when Greek traffic controllers last spoke with the pilot, who seemed in good spirits.

At 2:27 a.m., when the plane was passing from Greek to Egyptian-supervised airspace, the controllers in Athens tried and failed repeatedly to reach the pilots by radio. Even attempts on an emergency frequency failed.

At the same time, technical data was being transmitted from the plane automatically through its Aircraft Communications Addressing and Reporting System, or Acars, which modern jetliners use to provide status updates to maintenance and operational centers on the ground.

Representatives of Airbus and the Federal Aviation Administration said they could not confirm the authenticity of the technical signals. Dina El-Fouly, a spokeswoman for EgyptAir, declined to comment on the apparently leaked data.

“We cannot say anything, because we have already launched a committee to investigate the crash,” she said. “It hasn’t told us anything until now.”

The data, first reported on, is written tersely in abbreviations and codes. Robert W. Mann, a former commercial airline pilot and an industry analyst, said the jargon in the messages told a compelling, although incomplete, story.

At 2:26 a.m., a message indicated that the right cockpit window had been opened. This could have been done to vent smoke, Mr. Mann said, or something else could have caused the breach.

Over the next two minutes, 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 that 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.

Finally at 2:29, there were two more alerts having to do with the plane’s flight control computer systems.

“The last two are troubling,” Mr. Mann said. “You are starting to really see things rapidly degrade.”

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, but pilots prefer to rely on autopilot systems in those conditions because if they were to ever lose control of the plane, it could be hard to regain, Mr. Mann said. That is why pilots sometimes call those conditions the “coffin corner.”

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. It is over the course of two minutes, which might have seemed like an eternity on that plane, but is relatively fast.

This is also the moment that the plane left Greek airspace, and at 2:29:40 a.m., Greek controllers lost the aircraft’s trace, just inside Egyptian airspace, about halfway between Crete and Egypt.

Around this time, the plane 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 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.

One former crash investigator said that radar evidence pointing to a series of sharp maneuvers in the moments before radar contact was lost suggested that the plane was almost certainly not under the control of the pilots.

Whatever upset the Airbus was so sudden and violent that it could not be compensated for by the plane’s automated safety systems.

“In my mind, this basically opens two axes of possibility: either a sudden technical problem or some kind of illicit or terrorist act,” said the expert, Alain Bouillard, a former chief investigator for the French Bureau of Investigations and Analyses.

Given the limited amount of evidence available so far, experts said it was difficult to say with any certainty what kind of technical failure could have brought the plane down.

One possibility, Mr. Bouillard said, might be a malfunction in the plane’s cabin pressurization systems that could have caused the fuselage to rupture. At high altitude, such a rupture could be potentially catastrophic if the crew was unable to initiate a controlled descent to a lower altitude and make an emergency landing.

If the inquiry fails to uncover strong evidence of a technical problem, experts said the possibility of a more sinister chain of events would most likely take prominence. But given the circumstances of this accident, particularly in the absence of a claim of responsibility by a terrorist group or intelligence pointing to a perpetrator, it could take months to prove with any certainty that it was a terrorist act.

An initial review of the passengers aboard against American terrorist watch lists have found no matches, according to Representative Adam B. Schiff of California, the senior Democrat on the House Intelligence Committee, who has received several briefings on the investigation.

The Islamic State, considered the most likely group behind the attack, is normally quick to announce its role, as it did last fall after the crash of a Russian flight over Egypt’s Sinai Desert.

“Its important to note that attribution in the theater of terrorism is crucial,” said Michael S. Smith II, a managing partner of Kronos Advisory, a firm specializing in terrorism research.

What may be most valuable to investigators — and perhaps far more difficult to recover — is material that would have quickly sunk to the seafloor.

If that debris is scattered over a wide area, and the pieces are relatively small, it would suggest that the plane broke up in the air — supporting the theory of an onboard explosion. However, if the debris field is concentrated in a relatively small area, that would indicate that the aircraft hit the surface of the water largely intact.

The plane’s two flight data recorders, or “black boxes,” if they can be recovered, would also provide important clues.

The shock wave of an onboard explosion, for example, may have been captured by the microphones of the cockpit voice recorder, experts said; such a blast would also instantly disable the flight data recorder. In the event of a technical failure, Mr. Bouillard said, the data recorder — which tracks information including the plane’s position, speed, altitude and direction — would normally continue to function until the moment of impact.

Officials could also not rule out that one of the pilots intentionally brought down the plane.

The flight track of the Airbus on Thursday indicated that it crashed halfway between Crete and Egypt, which could mean it landed on what scientists refer to as the Mediterranean Ridge.

The ridge has been pushed upward by the African plate of the earth’s crust sliding under the Aegean Sea, deforming and crumbling the seafloor, said William B.F. Ryan, a scientist at the Lamont-Doherty Earth Observatory at Columbia University who has studied the Mediterranean seafloor.

The water there is about 1.5 miles deep, and picking out wreckage at the bottom from among the bumps, which are perhaps 50 to 100 feet in size, could be complex, he said.

If the plane crashed farther to the south, the wreckage would lie on a smoother plain at a depth between 1.7 and 2 miles, Dr. Ryan said. In that case, the search would go faster — and the much-desired answer to what caused the crash could come quicker.

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