On the Design of Flight-Deck Procedures - Intelligent Systems ...

3. THE FOURTH P: PRACTICES3.1. AN EXTENSION OF THE THREE P'sAs we began this study we focused on the macro-ergonomics aspects of flight operations: thephilosophy, policies, and procedures. As we progressed, it appeared to us that something was missing.We discovered that the macro-ergonomics approach had led us astray from the focal point of any humanmachinesystem -- the human operator. We neglected the ultimate consumer of the procedure -- the flightcrew, whose decisions and actions determine the “system outcome.”To correct this, we have added an additional component -- practices. The term “practice” encompassesevery activity conducted on the flight deck: correct execution of a procedure, deviation from a procedure,omission of a procedure, the use of a technique, or any other action. While a procedure may bemandatory, it is the pilot who will either conform to it or deviate from it. The procedure is specified bymanagement -- the practice is conducted by the crew. Ideally procedures and practices should be thesame. The high prevalence of the “pilot deviation from SOP” classification mentioned earlier indicatesthat no one can assume that pilots will always follow any given procedure dictated by management 4 .The goal of flight management is to promote “good” practices by specifying coherent procedures. Butwe must also recognize that this is not always the case: procedures may be poorly designed. The crewcan either conform to a procedure or deviate from it. The deviation may be trivial (e.g., superimposingsome non-standard language on a procedural callout), or it may be significant (e.g., not setting the autobrakesaccording to the takeoff procedures). The alternatives of conformity versus deviation can bevisualized as a switch (Figure 3). This may be somewhat of an over-simplification, but it expresses thechoice that the crew member must make: to conform to the company's SOP, or to deviate. For example,we once observed a captain who, in response to the first officer's question regarding the conduct of amandatory taxi procedure, replied “I just don't do that procedure.” That captain, unequivocally, placedthe switch in the deviate position.CrewConformDeviatePracticesFigure 3. The deviate versus conform “switch”4 Assuming, of course, that the procedure is clear to the crew. We recognize, however, that this is not always the case andsome SOPs can be ambiguous and lead to deviations by a well meaning pilot.8