This is an extract from a 1990 paper (publicly available) regarding scientific analysis methods as employed by the AAIB. It helps demonstrate why the answers will be ready when they are ready, and not because the Editor of a tabloid has a deadline...
Deficiencies in reports matter, because the real aim of investigations is to reduce accident
rates by making effective safety recommendations. If we don't solve the accident properly, our recommendations are likely to be ineffective. But even if we are satisfied that our investigation is sound, it will still be a failure if the recommendations are not adopted. Recommendations involve change: they are disruptive, make work, and cost money. Those with the power to implement them will therefore seek ways to avoid doing so. If the report is open to challenge on any ground - not all the data was gathered, the logic is defective, alternative propositions were not canvassed - then it will be unpersuasive, and inaction is likely to prevail…
…We start with the on-site investigation. We make an initial survey and photograph the scene. The wreckage trail is plotted, and ground scars documented. Then we examine the wreckage in greater detail – are the extremities present? Can control system continuity be established? Were other systems apparently normal? If possible, we document the cockpit control positions, and the positions of control surfaces at impact, and so on. In the case of an accident to a large airliner, the protocols to be followed are detailed in the Manual of Accident Investigation (ICAO, 1970). Witness interviewing, document retrieval and detailed examination of the wreckage follow. In all of this phase, the work can be characterised as data gathering and documentation. There are protocols for each part: how to plot the wreckage trail, witness interviewing techniques and so on. While this phase is in progress, the news media will be demanding to know what caused the
accident, and whom to blame. Of course, we tell them that the analysis cannot be started until all the data have been gathered. Of course this is untrue, but it serves to get them off our backs. In the first place, it is untrue because that is not the way the human mind works. The mind seeks to join bits of information together to make sense of them. At quite an early stage, some parts of the puzzle will become clear. It will be possible to characterise the impact as steep or shallow angle, and high or low energy. If the aircraft started to break up before impact, this will soon be known. The answers to these and other questions will give rise to possible sequences of events, and so guide the search for supporting or rebutting information. At the same time, we must be aware of the danger of the 'glimpse of the blindingly obvious'. The thing that 'obviously' caused the accident may, in reality, have had nothing to do with it. Basic data should still continue to be gathered, and alternative explanations sought. Another reason that analysis starts before all the data is available is that an unguided search of the mass of documentation associated with an aircraft and its crew is likely to be fruitless. We need to be guided by some positive line of inquiry. If a mechanical problem seems likely, the airframe logbooks may have useful information. If the pilot may have been fatigued, crew
flight and duty time records are likely to be relevant. In other words, the search for data is guided by some theoretical propositions, which the data may support or rebut. (There is a distinction between hypotheses and propositions. Hypotheses will be tested statistically, by examining a sufficient number of samples to support or reject the hypothesis with given confidence. A proposition, on the other hand, is a possibility arising from some theory, which we may or may not find that our data fits).