Results indicate that alertness decrement occurrences may be very frequent, even during daytime flights, without previous sleep loss.
Results also show that alertness decrement rates are higher during north-south flights than during transatlantic flights, especially for the cruise phase. This difference may be due to the very high monotony of cruise phases during north-south flights for which radio contacts are rare. However, for Asiatic rotations, the high number of ATC communications contributes towards limiting reductions in the alertness level.
These alertness decrements may occur simultaneously for both pilots. This can be attributed to potentially highly synchronized activities between the two pilots. Observing activities and behaviors shows that certain actions, such as reading technical documents or passively supervising systems, favor these reductions in alertness. Inversely, motoric tasks associated with a cognitive activity, such as interacting with the FMS (Flight Management System), reactivate the pilots' alertness level. Also, the mutual knowledge that pilots have of themselves, the aircraft and the route may have a negative influence on alertness.
These results reflect the effect of monotony towards reducing the alertness level.
6.3.4. REDUCING THE EFFECT OF MONOTONY
Some laboratory and field research is available to document developed solutions for alleviating the effects of monotony on an operator's alertness. The following methods were deemed efficient:
. introducing short breaks during the task (10 minutes every 30 minutes),
. introducing a different task,
. task execution rate set by the operator.
Another method consists of altering the task execution process without modifying its nature. This solution was shown to be well founded by experimental laboratory research (Cabon, 1992). The task used in this experiment was a critical signal supervision and detection task requiring the use of "automatic" processes. Its duration lasted 4 hours.
In order to break the monotony of the task, subjects were forced to use "controlled" processes during short periods. These processes required greater attention than the "automatic" processes. This situation (experimental condition) was compared with a condition in which the subjects only used the automatic processes (reference condition). As a result of this daytime experiment, the following results were observed between start and end:
. similar performance (number of omitted signals) under experimental conditions,
. significant decrease in performance under reference conditions.
When the experiment was held at night, significant reductions were observed irrespective of the conditions. 中國航空網 www.k6050.com 航空翻譯 www.aviation.cn 本文鏈接地址：Getting to grips with Fatigue & Alertness Management(53)
