What are the likely scenarios?

When dealing with aircraft system safety, I often found it difficult to encourage design engineers to look at aircraft level effects. It was more common to address each set of systems as if they were the only ones that counted.

Safe continued flight and landing depends on a whole host of interactions. Picking up a technical specification, for say an autopilot, reading it and understanding it is one thing. It’s harder to appreciate how it interacts with every other part of an aircraft in flight.

Considering a large commercial aircraft there are only a few general conditions that can create a total catastrophe. I’m using a specific meaning of that well used word. In this case, catastrophe is a complete aircraft level failure situation that is non-recoverable. A chain of events that leads inevitably to fatalities and a total hull loss.

There are only a few general conditions because there are design commonalities between modern civil aircraft. For example, they all need surfaces that generate lift and surfaces that enable aircraft control. They all have propulsion systems that generate thrust. If they are for civil passenger transport, they all have environmental control systems that maintain a habitable environment within a pressurised area.

In flying, they all are subject to the effects of weather. That is any hostile situation that can exist in the atmosphere, from ground up.

With what is so far known about the crash of China Eastern flight MU5735, when thinking about potential aircraft level events, it’s not possible to rule out many scenarios.

However, it’s extremely difficult to conceive of a weather event on the day of occurrence that could have led to such a disastrous outcome. No great storm activity was reported. So, this is unlikely to have been an accident like Air France flight AF447 in 2009[1]. A high-altitude stall can be recovered if no other significant negative factors come into play.

Additionally, it’s extremely difficult to imagine this accident as a depressurising event. So, this is unlikely to have been an accident like Helios Airways flight 522 in 2005[2]. Unless there was a massive explosive decompression that caused structural and control damage. Japan Air Lines Flight 123 in 1985 had such a tragic fate[3].

Engines can fail in a spectacular way but that does not normally destroy a whole aircraft. A total loss of propulsion turns a large aircraft into a large glider. The trajectory of this aircraft suggests something happened that was far more devastating than the loss of one, or both engines.

Issues related to communication and navigation can put to one side given that the accident from start to finish was so rapid. No crew communication is reported to have taken place.

Following the deductions made above the remaining possibilities that warrant consideration are to do with either or both, structural failure, and unrecoverable aircraft control failure. The accident investigators working on-site will be looking at the deformations found in the recovered wreckage. They will be looking at collecting and putting together what remains of the aircraft control system. They will be saving every electronic circuit board they can find.

By far the remotest possibility is a wilful act of destruction. It’s better to first rule out more likely aircraft scenarios before posing questions that bringing into question those on-board.

Global commercial aviation has a tremendous safety record. China’s aviation safety record is a strong one. As has been said by commentators: planes don’t just drop out of the sky like that one. The urgency of the accident investigation is all too evident. The sooner there’s a plausible theory the sooner corrective action can be put in place.

[1] https://bea.aero/docspa/2009/f-cp090601.en/pdf/f-cp090601.en.pdf

[2] https://aaiasb.gr/imagies/stories/documents/11_2006_EN.pdf

[3] https://www.mlit.go.jp/jtsb/eng-air_report/JA8119.pdf

Author: johnwvincent

Our man in Southern England

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