China Eastern Crash: Plane Dived at Nearly the Speed of Sound

TAccording to Bloomberg News, the flight track data of China Eastern Airlines Corp. aircraft that crashed on Monday showed it traveling close to sound speed in its moments before hitting a hillside.

Such an impact may complicate the task for investigators because it can obliterate evidence and, in rare cases, damage a plane’s data and voice recorders that are designed to withstand most crashes.

According to Flightradar24 data, the Boeing Co. 737-8800 flew at speeds of more than 640 miles (or 966 km) an hour and may have even exceeded 700 mph at times, according to their website.

“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 the sound speed slows as you get higher in altitude. At 35,000ft (10.668m), it is around 663 MPH.

Flight 5735, a flight from Kunming to Guangzhou with 132 passengers was at 29,000 feet altitude when it started descending. Flightradar24 captured the data transmission by the aircraft. Prior to the dive, the jetliner was traveling at approximately 595 mph.

Videos that appear to have shown the jet dive at an extreme angle moments before impact indicate that the speed data supports the assumption of the large force it hit the ground.

“It was an exceedingly high-energy crash,” said Bob Mann, president of R.W. Mann & Co. consultancy, who did not participate in the speed analysis. “It looks like it literally evaporated into a crater. Do the flight data recorder or cockpit voice recorder or quick access recorder — do any survive? I just don’t know the answer.”

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 U.S. National Transportation Safety Board’s chief technical adviser for recorders.

“The hard part is going to be finding it,” Cash said.

The circuit boards storing the data often break loose from the recorder’s protective exterior. But data can usually be extracted even if they’re damaged, he said.

“It’s probably embedded in the ground somewhere,” he said. “But I would suspect it would be O.K.”

There is no beacon activation

Zhu Tao is an official of the Civil Aviation Administration of China. Searchers won’t be aided by a beacon or “ping” from the devices because they are only activated underwater.

The two recorders on the China Eastern 737-800 — a cockpit voice recorder and another that captures flight data — were supplied by the aerospace division of Honeywell International Inc. and installed on the plane when it was new, according to company spokesman Adam Kress.

While crash investigators have mastered the art of examining wreckage to find clues for decades, there are some instances when impacts could erase any evidence. The crash of an Ethiopian Airlines 737 Max in 2019 was traced back to a sensor on the plane’s nose, but the sensor was never found after the jet hit the ground at a high speed, according to a preliminary report from that nation.

Accident investigators should be able to find more precise speed data from the jet’s flight recorder. If it isn’t available for some reason, aerodynamic experts can perform extensive analysis to more closely estimate speed.

Flightradar24’s data includes the jet’s speed, but it’s measured horizontally across the ground. Bloomberg’s computations give a rough idea of how fast it was flying through the air by taking into account its horizontal speed over the ground as well as how fast it was descending.

The speed estimates were based on how fast the jet traveled between two points and didn’t take into account wind direction or other atmospheric conditions. Although the speeds estimated by Bloomberg were conservative, actual speeds might be greater.

While unverified videos showed the plane diving at a steep angle near the ground, it wasn’t clear how fast it was traveling at impact. Flightradar24 captured the last data transmission at 3,200 feet.

Just 40 seconds after the last transmission, it stopped descending. It briefly climbed again before returning to its original dive. According to preliminary reviews, the jet slowed down a bit during these latter stages.

However, it was still moving much faster than normal. Typically, jets don’t go above 288 mph at altitudes below 10,000 feet. Flightradar24 data shows that the China Eastern plane was travelling at an average speed of 470 miles at such altitudes.

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