There’s been little information out of China with regard to the China Eastern 737 that crashed last week, but from what we do know, we have some possibilities to include and exclude from consideration.
What’s Known About China Eastern Flight 5735
There’s very little known about the crash of China Eastern flight 5735. It was operating a routine flight between Kunming and Guangzhou, the airline’s hub near the southeastern border with Hong Kong. The 737-800 (NG – New Generation) was carrying 123 passengers and nine crew members according to sources when it dramatically lost altitude from 29,100 feet (cruising) plunging into a mountainside below.
A purported video of the crash showed a vertical spire diving toward the mountainside resulting in an explosion and plume of smoke.
Data from flight trackers showed the aircraft appeared to recover around 7,000-9,000 feet before shortly thereafter continuing its fatal drop. The black box has been recovered and because the aircraft was manufactured in the United States, federal investigators will join the effort to understand what caused the crash along with Chinese teams.
The granular ADS-B data from @flightradar24 shows that #MU5735 may have actually regained control after an initial nosedive before going nose down once more and impacting the ground https://t.co/X0zSzSU6TR
— Jason Rabinowitz (@AirlineFlyer) March 21, 2022
At the time of publication, neither a recording of communications with air traffic control (ATC) nor a transcript was available.
Many have speculated about the cause of the crash and as someone who has followed aviation and subsequently, air crash investigations, some early possible causes seem to be guesses. I don’t have any inside information, but there are some speculations that seem less credible than others for a few reasons.
Mid-Air Break Up
One of the notions forwarded was that there was some sort of a mid-air breakup of the aircraft that caused it to fall from the sky. One reason that this theory would have legs is if there is a lack of direct communication with ATC. We don’t know that at this time. The other plausible reason is because aircraft pieces were found separate from the incinerated wreckage.
Why I feel this is unlikely is that noted recovery. If the plane was split apart in the air there wouldn’t be a recovery, just a straight drop from the sky and likely in several pieces, (more than has been demonstrated in the media) with a range of debris. That said, it’s also possible that the data showing a recovery was wrong.
Images appeared to show the winglet and part of the wing had sheered off and remained intact away from the crash site, and while the video is low quality, it’s hard to make out a vertical stabilizer (tail) in the video. That suggest that something happened to separate those parts, but a drop at of that magnitude could have had the same result.
Typically in a terrorism and hijacking situation, there is generally something as simple as a squawk 7500 code which indicates “Unlawful interference” such as either of these events or a simple 7700 which just demonstrates an emergency and is used more generally.
That’s not to say that something couldn’t have happened before the pilots had a chance to indicate this, but there was some sort of control briefly at the 7,000-9,000′ elevations so even with a struggle where control was regained temporarily, this wasn’t indicated. The problem with dismissing it based on the lack of a squawk 7500 or 7700 are two-fold. First, it’s possible that the pilots did indicate this but it didn’t function properly, the second is that in an air emergency the order of priorities shifts to “aviate, navigate, communicate.” The brief control period may demonstrate that they were still attempting to navigate.
The media was clear that there was no known “Mayday” distress call, so it seems unlikely even in a perilous dive, that this wouldn’t have come through from one of the two pilots.
The Boeing 737 is the most prolific aircraft ever produced. This particular model was a 737-NG ruling out a resurgence of the MCAS software that brought down aircraft in both Ethiopia and Indonesia that was found responsible for 737-MAX crashes. This plane was not equipped with MCAS and didn’t have any of the struggles with software that appeared to demonstrate a tug-of-war with the computers that other crashes have had.
An intentional downing of the aircraft by one or both of the pilots is possible. The protocol has changed since German Wings 9525 in which the co-pilot who had been treated for suicidal thoughts, locked out the captain and crashed the plane into a mountain. If both pilots were suicidal or the protocol to leave a flight attendant in the cockpit when one goes to the restroom wasn’t followed, then this is a possible cause.
This cause would explain a limited recovery of the aircraft (if there was a struggle) and the entire nose-down attitude of the plane at impact.
It should be noted as well that this possibility also explains another data point which is that the aircraft appears to be pushed or directed down rather than simply falling. This is again from the attitude but also from the rate of falling which appears to exceed the natural rate of descent from objects at that height reaching the ground in a freefall. Oddly, the speed fluctuations are also odd.
One question that remains was how a piece of the plane was then found away from the wreckage, but pushing a plane intentionally to the ground at that rate of speed could have sheered off pieces of the plane that couldn’t handle the stress.
Many prognosticators are focused on the recovery as I too have noted. It’s entirely possible that recovery never occurred. If the plane had encountered some sort of catastrophic failure at altitude, the reliance on flawed equipment is questionable. If ground radar detected the recovery as well, then this possibility is eliminated, but for now, it has to be at least possible that the preliminary data is bad and that leads to false assumptions.
There have been just 11 fatal incidents out of 7,000+ 737-NGs in service. Unlike wide-body aircraft which may only fly once or twice daily, these workhorse aircraft are used on shorter flights resulting in far more take-offs and landings every day. Far more wear and tear on the equipment leads to greater chances of a mechanical problem.
This particular aircraft was manufactured in 2015 and is considered relatively new as most aircraft remain in service for 20+ years. That said, mechanical issues can happen based on something that took place on the ground, over time, or encountered in-flight. Maintenance records will be scrutinized in the coming weeks, months, and maybe years to determine the direct cause.
One concept that’s not being discussed enough (from my estimation) is the altitude at which the plane appeared to temporarily regain control. In a rapid decompression event, one of the first orders of business is to get below 10,000 feet where passengers can easily breathe without the need for oxygen pumped from the plane’s systems.
If there had been a rapid decompression of some sort, the rapid descent, (negative vertical speed in excess of 20,000 feet/minute) would have been egregious, but it’s possible that if there had been something that caused the plane to lose pressure, the pilots may have been trying to get under 10,000 feet for this purpose initially, but the issue that caused the decompression remained and the aircraft became unmanageable as a result of the drop.
It’s impossible to know what caused this crash initially. Even with transcripts or recordings from the cockpit and ATC, the information could prove to be incorrect or flawed as could the data. Investigations of this nature can take years to resolve. However, key data points (a mostly intact debris field and a recovery at 7,000-9,000 feet) make this crash particularly beguiling.
What do you think? Do you have any thoughts of what could have caused this accident? What do you make of the data points?