If investigators of this case have the idea that ‘accidents are caused’ and their purpose is to investigate the cause so this may be ‘removed’, the question, maybe unspoken, in their minds will be what is the accident? Is it only an accident because damage and injury occurred? It is hard for the critical brain to have anything other than a void of ideas at this point. Nor, I would suggest, is it helpful to think in terms of Swiss Cheese. Are all the holes failures of defences? If so what are the defences and are they truly linear in relationship (one following the other)? What is the accident that these defences are intended to protect us from?
On the other hand, if these investigators understand scientific process modelling there is no mind-void. There is a structure instead. The lessons of all sciences over centuries of effort point to the need to understand the process that gave rise to the phenomenon (damage in this case) of interest. So if understanding this case is approached in a scientific manner, rather than as a sort of cottage industry habit, we have two essential aspects to consider:
A. Describe the process leading to damage
B. Using an Energy Damage Model, determine the structure of that process. Damage necessarily requires the application of energy to an asset.
This is not only an academic consideration. The objective structure enables all aspects of this case to be categorised and hence the lessons learned applied to all other diverse cases in the same category. Doing so also develops our ability to envisage cases that have yet to arise.
In this case there are three distinct energy damage processes, two involving kinetic energy and one chemical bonding energy.
Process 1
In energy terms, the Total Flight Energy = Kinetic Energy+Gravitational Potential Energy. In a controlled descent towards landing the system can receive energy input from engine thrust – more thrust the less rate of or angle of descent and vice versa. In a controlled descent the approach speed is constant as is the rate of descent. A twin engine aircraft is able to take off, fly and land on one engine. On no engines it becomes a glider, in which Kinetic Energy is maintained at the expense of a loss of Gravitational Potential Energy.
It is evident things went wrong after the climb-out that was initiated by the pilots at close to or the point of the first touch down.
Possible candidates for the Process 1 Event are (a) the decision to take off following the bird strike just before or at touch down; (b) at the top of the climb-out, the crew erroneously shut down the one engine that was operating normally (climbing away from the runway requires thrust from at least one engine); (c) one or both engines failed after the climb-out. (b) or (c) necessitate an emergency return to the runway.
It appears, from what is known or deduced at present from publicly available information (in the absence of factual data) the approach may have occurred with no or reduced engine power, meaning that the angle and rate of descent were no longer under the full control of the flight crew. The flight crew may not have had time to deploy the undercarriage and flaps. The possibility of both systems being disabled by a bird strike or pilot action is not considered here.
The Process 1 Outcome was a landing in which the undercarriage was not extended, resulting in damage occurring to the underbelly and the engine nacelles as the aircraft skidded along the runway (the Outcome). This landing also occurred without wing flaps being extended, likely requiring a higher approach speed than normal, hence more kinetic energy than normal.
Process 2 follows this, with the Outcome of Process 1 becoming the Mechanism of Process 2.
In Process 2 normal directional control has been lost (there are no differential brakes and the rudder probably does not have sufficient authority at these speeds) over the skidding aircraft and quite where and how it ends up when all the kinetic energy has been dissipated in skidding friction is determined by the runway conditions – remaining length, rate of deceleration, obstructions and so on. Some aircraft in this situation come to rest on the runway, others off the runway. I have recently seen images of such end points where the aircraft slides over an embankment, or comes to rest in water or in an adjacent car park, or across an active road. In this case the end of Process 2 is impact with a concrete wall protecting a localiser antenna, resulting in impact damage.
Process 3 is simple. Impact damage releases fuel, which is ignited by hot engine exhaust or by body parts heated by sliding friction.
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Lest we find ourselves wondering how could the flight crew have got it so wrong?
There are times in the life of a pilot when an instant significant decision has to be made in life -threatening circumstances. Say within no more than a second or so, all factors have to be considered with probably incomplete information and a decision made and acted on. Think of US Airways Flight 1549 ( https://www.britannica.com/topic/US-Airways-Flight-1549-incident) that ditched in the Hudson River (USA) after both engines failed.