In aviation the widely recognised definition of an accident is given in
ICAO Annex 13. This document also provides guidance for investigation and reporting.
With respect to the conclusions of an investigation, the Annex recommends – “List the findings and causes established ... The list of causes should include both the immediate and the deeper systemic causes.” This neither requires nor prohibits stating a ‘Primary Cause’; however, there may be more value if all of the contributing factors were considered as a broad view and not as follow-ons to a primary cause.
The purpose of the investigation is to “prevent accidents and incidents” (Annex 13 Chapter 3), thus it is necessary to consider those contributions which address this purpose.
A problem with ‘primary cause’ is that it focuses attention to one specific aspect which might only apply to the particular accident being investigated, and thus may add little value in preventing similar but not identical accidents.
As examples; in this and similar accidents/incidents the failure to retard the thrust levers is a contributing cause, but there are many aspects of design, the MEL, human error, the situation, drills and procedures which will aid accident prevention even when the thrust levers are operated correctly.
As at Midway the lack of overrun area increased the severity of the accident, yet the underlying ‘cause’ appears to be the lack of a sufficient safety margin during landing, whether this be in calculating the required landing distance - problems with runway condition, wet, grooved, human error - or the lack of real estate at the end/side of the runway. EMAS is just one solution, but there are many others which will also be effective at CON or MID, or on any other runway where marginal operations are conducted.
Thus an investigation should consider and report equally on all of these options to add to our safety defences in a wide range of situations that we may encounter.