Aviation experts are baffled by data showing that a China Eastern Boeing 737-800 about to begin its descent to the city of Guangzhou suddenly plunged vertically to earth like a missile, killing the 123 passengers and nine crew aboard on Monday.
This horrific disaster, the worst in recent Chinese aviation history, highlights that the kind of data that once took investigators at least days to gather is now instantly available from open-source tracking sites like FlightRadar. As a result, speculation about the cause of a crash creates an instant Twitter storm as pilots and technical experts attempt to interpret what they are looking at.
In this case, there is a striking consensus that something very unusual happened that cannot directly relate to previous disasters involving this version of the 737, one of the most flown jets in the world, which preceded the 737-MAX version that was grounded for nearly two years after two catastrophic accidents.
The flight pattern revealed by radar shows that the airplane was flying at 29,100 feet over mountainous terrain, with the crew about to prepare for the descent, when the nose abruptly pitched down and it began the dive. As it neared the terrain it seemed to briefly pull up but then resumed the dive to impact with enormous force.
The only certain details are what did not happen: There was no indication of an engine fire and no sign of any major part of the airplane breaking up. Significantly, there was no time for the crew to send a Mayday distress call.
There have been several cases of various models of the 737 suffering an explosive decompression, when part of the fuselage structure, weakened by undetected cracks in the outer skin, suddenly rips open and the air in the pressurized cabin is released in a blast, but even with that damage pilots have been able to get the airplane down safely, even with parts of the cabin open to the skies.
But those events happened early in the flights, when the airplanes were reaching cruise altitude, not as in this case at the end of the cruise and at the beginning of the approach to the airport.
One aerospace engineer, commenting on the AviationHerald site, says, “It is not normal for a plane to nose dive into the ground, it rules out a lot of failures.” Another says, “To those who can’t think of any reason… there are a lot. Some repeats from things that already happened, perhaps something that has never happened before. Aviation is like that.”
There was a case where a similar dive was involved: in 1997 Silk Air Flight 185, an earlier model 737, crashed into a river in Sumatra, killing 104 people; an investigation by the US National Transportation Safety Board concluded that the pilot had deliberately triggered the dive in an act of suicide, but this verdict was disputed by Indonesian regulators, who cited problems with the rudder controls that had caused other crashes of that model.
Another possibility is that although no break-up was visible on the radar track, some part of the horizontal stabilizer, which would be activated to begin descent, may have broken off.
All of this leads to one urgent task—to find an answer in the one place where it should be found, in the airplane’s black boxes. The crash site is accessible and teams are headed there. There is, however, some concern that these flight data recorders might not survive such a devastating impact.
The Chinese regulators and investigators are highly regarded. China was the first country to ground the 737-Max and the last to allow it to return to the skies. Domestic air travel in China has grown rapidly in the last decade, but there have been very few accidents.