China jet’s dive took it near speed of sound before crash

Bloomberg

The China Eastern Airlines Corp jet that crashed was travelling at close to the speed of sound in the moments before it slammed
into a hillside, according to a Bloomberg News review of flight-track data.
Such an impact may complicate the task for investigators because it can obliterate evidence and damage a plane’s data and voice recorders that are designed to withstand most crashes. One of the two black boxes was located on Wednesday, officials in China said.
The Boeing Co 737-800 was knifing through the air at more than 640 miles (966 kilometers) per hour, and at times may have exceeded 700 mph, according to data from Flightradar24, a website that tracks planes.
“The preliminary data indicate it was near the speed of sound,” said John Hansman, a Massachusetts Institute of Technology
astronautics and aeronautics professor who reviewed Bloomberg’s calculation of the jet’s speed. “It was coming down steep.” Sound travels at 761 mph at sea level but slows with altitude as air temperature goes down and is about 663 mph at 35,000 feet (10,668 meters).
Flight 5735 was flying to Guangzhou from Kunming with 132 people on board at an altitude of about 29,000 feet when it began a sudden descent, according to data transmitted by the plane and captured by Flightradar24. The jetliner was cruising at about 595 mph before the dive. The speed data is consistent with videos appearing to show the jet diving at a steep angle in the moments before impact and indicates that it likely hit the ground with huge force.
“It was an exceedingly high-energy crash,” said Bob Mann, president of RW Mann & Co consultancy, who did not participate in the speed analysis. “It looks like it literally evaporated into a crater.” Chinese officials said that the black box they had located was badly damaged, but didn’t say which one it was — the cockpit voice recorder or the one that captures flight data.
Modern black-box recorders, which store data on computer chips, have a good record of survival in high-velocity crashes, said James Cash, who formerly served as the US National Transportation Safety Board’s chief technical adviser for recorders.
The two recorders on the China Eastern 737-800 were supplied by the aerospace division of Honeywell International and installed on the plane when it was new, according to company spokesman Adam Kress.