Constellations of European and U.S. satellites captured emergency distress signals from the doomed EgyptAir Flight 804 minutes after it fell off radar on May 19, according to the National Oceanic and Atmospheric Administration.
A device known as an emergency locator transmitter, or ELT, began radioing an automatic distress message at 2:36 a.m. local time, Lieutenant Jason Wilson, an operations support officer at NOAA, said in an e-mail.
Five satellites relayed signals from the beacon to a ground station in Cyprus, said Wilson, whose agency monitors such distress signals, and a document prepared by the French government that was obtained by Bloomberg. The satellites provided a location of a probable crash site in the Mediterranean Sea that is accurate to within about 5 kilometers (3.1 miles).
The information, which confirms an earlier report on Egypt’s state-owned Ahram Gate website, will assist the search for wreckage beneath the sea, including the Airbus A320’s two crash-proof recorders, or black boxes. The plane went down on a Paris-to-Cairo flight with 66 people aboard.
A U.S. ground station in Maryland also was alerted that satellites had “received two bursts from the beacon, but was unable to make a location,” Wilson said in an e-mail.
Encoded information in the distress signal linked it to the specific EgyptAir aircraft involved in the accident, Wilson said. Airlines and other users of ELTs register them with NOAA and other agencies that monitor the signals.
“They received the beacon ID and were able to correlate that with the beacon that was on MS 804,” he said, referring to the shorthand code for the flight.
Airliners flying international routes are required to carry ELTs. The devices are designed to send a signal to satellite networks if a plane crashes, alerting authorities to the accident and providing a location.
EgyptAir’s emergency signal came about six minutes after the plane stopped transmitting its location to radar at 2:29:33 a.m., according to the flight tracking website FlightRadar24.
Investigators so far haven’t been able to say what brought down the flight so suddenly.
Separately, the plane transmitted a series of seven emergency messages indicating smoke had been detected in two locations and noting unspecified problems with cockpit windows and flight computers.
The emergency beacon is separate from the so-called pingers on the plane’s black box recorders. The pingers are designed to operate underwater so that investigators can locate the wreckage.
The French Navy has sent one of its most advanced survey vessels to lead the search for the submerged wreckage in the eastern Mediterranean.
The ELT only functions immediately after a crash and can’t transmit underwater, and thus can’t now lead searchers directly to the wreckage.
ELTs are typically designed to start transmitting after impact in a crash, Adam Williams, manager of airport policy for the Aircraft Owners and Pilots Association trade group, said in an interview.
In some cases, they can also be manually activated during an emergency, Williams said. A commercial pilot and flight instructor, Williams said he wasn’t familiar with how the device on the EgyptAir plane would have worked.
If the EgyptAir ELT did activate when the plane hit the water, it would provide the most accurate information to date on where the wreckage is located. The ELT information follows a similar pattern to radar flight-tracking that the Greek government did in the early morning hours after the plane went down.
After the plane stopped transmitting its position, radars reflecting radio beams off of the fuselage and other metal components continued to track it until 2:37 a.m., according to the Greek government. The so-called primary radar returns indicated the plane turned 90 degrees left and then made a right-hand orbit, according to a preliminary analysis.
The Greek and Egyptian governments have said they didn’t receive a distress call from pilots, which they would have radioed over a different frequency than the one used by the ELT beacon.
The detection of the ELT signal is an endorsement of a new generation of satellites used to detect the beacons, Wilson said.
Until recently, relatively few satellites circling the Earth in lower orbits were used. It can sometimes take an hour or more for the satellites to make enough passes over a crash site to estimate its location, he said.
The U.S., Europe and Russia are now installing radio receivers that can detect the emergency beacons on global-positioning satellites. Because they are at higher altitudes, allowing them to see more of the Earth’s surface at a time, and there are more of them, they will theoretically be better at monitoring for the beacons.
Five such global-positioning satellites captured the signal, according to Wilson.