Reality tree

Figure 17.3 Pharmaceutical industry future reality tree.

A case-study approach is appropriate for exploratory studies such as this (Yin, 1994). For the subject of the study, an acdderrt was needed where detailed information was available to form a Current Reahty Tree - the situation at the time of the accident. From this, it should be possible to generate safety recommendations to form a Future Reality Tree - the situation we would like to bring about The accident used for the study was the Ansett (New Zealand) Dash 8 controlled flight into terrain, near Palmerston North in New Zealand, because litigation had made the necessary information available. 

By convention, the Current Reality Tree entities are written in the present tense, even though, as here, the accident is in the past. 

Full details of the eonstruction of the Current Reality Tree are shown in Zotov, Hunt, and Wright (2004). 

These networks link together, to form the Current Reality Tree (Figure 9.9). The dashed lines near the top of the tree represent potentiation. At this point, we no longer have necessary and sufficient conditiorrs for the next step. Irrstead, we have a hazardous situation, wherein the occttrrence of random and ordirrarily berrign conditions (for example, low clond) can tip the sitrration from potential accident to actuality. 

When Figures 9.11 and 9.12 are combined, we get the Current Reality Tree from the perspective of the CAA (Figure 9.13). 

Figure 9.13 Current reality tree the ability of the CAA to avert the Ansett accident...

Arising from these injections, we find that recurring defects are reviewed, to locate the causes safety implications of defects are considered and safety implications of proposed savings are reviewed. As with the Current Reality Tree, we can form all the sets into a Futiue Reality Tree (Figure 9.15). The square-cornered injections form the basis of the safety recommendations. The Future Reality Tree is formed by combining the sectors ... 

Details of the construction of the Future Reality Trees are available in Zotov, Wright and Hunt (2005), at www.aavpa.org. 

Figure 9.14 Future reality tree safety manager funetions... 

When constmcting the CAA Future Reality Tree, there are no constraints on the type of recommendation, and because of the shape of the Current Reality Tree (Figure 9.13) we can address a fundamental problem. At the very base of the tree there is a conflict diagram the CAA would like to deploy all necessary resources to do the job properly, but has to work within a limited budget, and cannot do both. If we can break this conflict, then since all the undesirable effects stem from it, the whole tree will collapse, and it can be re-built as we would like it to be. 

Every arrow in a Cnrrent Reality Tree represents assumptions. Here are some of the assumptions in the CAA conflict diagram (Figure 9.16). 

The various sectors generated in this way are amalgamated as before, to form the new Future Reality Tree for the CAA (Figure 9.18). 

The object, however, is not to generate Future Reality Trees, but safety recommendations, and these come from the injections which make the Future Reality trees valid. 

Arising from the injections in the Ansett Future Reality Tree, the safety recommendations are ... 

The safety recommendations arising from the CAA Future Reality Tree are ... 

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