Another way of considering the maintenance technician’s process of completing a maintenance task is through a model created by Donald Norman called the action cycle (Norman, 1988).  This model begins with the user’s goal and breaks down the steps the user/technician takes to accomplish their goal.  The two main parts to this process are the execution of an action toward the goal and the evaluation of the action. 

On the execution side of the cycle, the maintenance technician begins with his intentions or plan of action.  This includes the technician matching their prior knowledge (KIH - knowledge in head) with their environment (KIW - knowledge in world).  The technician can then determine what actions will be required to move toward their goal.  The technician takes this information and plans a logical sequence of these actions.  The actions are then performed as planned.

Once the action has been performed, the maintenance technician observes the subsequent change in the environment.  A judgment is made as to whether the action taken has produced the intended outcome.  This part of the cycle involves analyzing whether what they now see in their environment (KIW) matches what they think they should see (KIH).

In any one of these six steps of execution and evaluation, the maintenance technician may encounter difficulties in moving toward the goal, which are termed ‘gulfs’.  Gulfs of execution are found when the technician’s KIH (knowledge in head) does not match KIW (knowledge in world). 

As the maintenance technician performs tasks, training knowledge and experience provides a great deal of expertise (KIH).  However, the maintenance manual is a necessary tool to bridge the gulfs of execution and evaluation in completion of the tasks (the goal).   In the execution of the task, the technician uses the manual to supplement his KIH with the KIW to successfully accomplish the goal.  Providing additional information such as “Notes” and “Warnings” is also useful in guiding the action sequence.  However, when this information is incomplete, confusing, or incorrect, the technician will “workaround” the task as written in the manual using KIH to move toward their goal completion.

Similarly, when the maintenance technician has executed the action, the manual may be used to provide feedback to aid evaluation of the action.  When a check or test of the procedure is included as part of the task sequence, the technician can quickly interpret whether the action taken was correct.  By providing KIW (the results of testing the system), the technician can compare this with their KIH and either narrow their gulf of execution or allow the user to take corrective actions.

Gulfs of execution and evaluation may also be due to the differences between the way in which the writer and engineer communicate the procedure in the documentation.  Writers and engineers must rely on their writing experience and knowledge of the aircraft systems when deciding how best to describe a procedure.  Likewise, a technician will rely on maintenance experience and knowledge of aircraft systems when deciding how to take the appropriate action and evaluate that action.  Unfortunately, the experience and knowledge of the writer, engineer, and the maintenance technician are all most likely quite different. 

Narrowing the gulfs is the principle reason for testing the usability of the document throughout the development process.  Most importantly, when the technical writer supplies the most useful information to the manual’s user, the technician will feel in control of performing the procedure accurately.  This provides the technician with positive affect through successful goal achievement.  In this way, a usable manual increases the likelihood of continued use as a valuable tool.