DAVID GREENE, HOST:
Let's work second-by-second through the end of a Metrojet flight over Egypt. Investigators do not know what caused this crash that killed everyone on board. They do know that this Russian airliner went down over a wide area of the Sinai Peninsula. And reconstructing the final seconds shows what is known and what is not. NPR's David Schaper reports.
DAVID SCHAPER, BYLINE: Everything appeared normal as the Metrojet charter flight full of vacationers departed from the Red Sea resort city of Sharm el-Sheikh bound for St. Petersburg.
IAN PETCHENIK: It was traveling at about 400 knots over the ground, 450 knots in the air, and was climbing through an altitude of just over 30,000 feet.
SCHAPER: That's Ian Petchenik of the global flight tracking service Flight Radar 24. The company's apps track flights worldwide in real time, and are used by anyone from grandparents anxiously awaiting a visit to business travelers wanting to know if their flights are on time. Petchenik is showing on a computer screen the data points of the Metrojet flight, such as speed and altitude, all down to a thousandth of a second at Coordinated Universal Time. The first 20-plus minutes were uneventful until the first anomaly at 4:13 and 13 seconds.
PETCHENIK: At 4:13:14 we detect a vertical speed change and the beginnings of a heading change.
SCHAPER: The plane is suddenly starting to descend and change direction.
PETCHENIK: At 4:13:17, so four seconds after our initial event start, we detect a rather dramatic increase in the descent of the aircraft.
SCHAPER: That increase of the rate of descent continues for another five seconds, when...
PETCHENIK: There is another dramatic shift in the heading as well as a dramatic increase in the rate of descent, from 5,952 feet per minute to 11,840 feet per minute.
SCHAPER: Petchenik says just 20 seconds after the event begins, no more data is transmitted. It indicates something has gone horribly wrong.
TODD CURTIS: I think the evidence so far is overwhelming that this was a high-altitude breakup, primarily because of the wreckage pattern on the ground.
SCHAPER: Todd Curtis is a former safety engineer at Boeing and now heads up the firm airsafe.com. He says any number of things could have caused a high-altitude breakup, including an onboard fire, some sort of structural failure or even a bomb. The key now, says Curtis, is finding as much of the wreckage as possible.
CURTIS: And to document the position of that wreckage and do other forensic-type activity so that they can take that information and perhaps piece together, among other things, what was the sequence of events? Which part of the aircraft seemed to have come off first?
ANTHONY BRICKHOUSE: Accident investigation is like putting a puzzle back together.
SCHAPER: Anthony Brickhouse is an air safety investigator and a professor of aerospace at Embry-Riddle Aeronautical University.
BRICKHOUSE: But typically with a puzzle, you have all the pieces in the box. With an aircraft accident investigation, a lot of times those pieces to the puzzle have been damaged, or they're actually missing. And that really complicates your job.
SCHAPER: Brickhouse says investigators will need to read the wreckage and look for certain telltale signs. For example...
BRICKHOUSE: Typically, if there's a bomb on board the aircraft that explodes, the damage would be from the inside out. So you would have an opening-up effect if the bomb were actually on board the aircraft. Also, the victims on board the aircraft would have certain signatures on their bodies.
SCHAPER: Other causes would yield different kinds of clues. It's a painstaking process, says Brickhouse. And above all, investigators need to demonstrate patience. David Schaper, NPR News. Transcript provided by NPR, Copyright NPR.
