These experimental results show that modifying the nature of the task, its duration, its execution rhythm and also the response execution process can attenuate the effects of monotony.
The principle for breaking monotony by alternating "automatic" and "controlled" cognitive processes was transposed to real situations involving military air surveillance operators (Cabon, 1992).
Field research carried out with nuclear power plant control room operators confirmed possibilities for practical uses of this solution when monitoring automated processes (Cabon, 1992).
This method was transposed to real long-haul flight situations within the context of validating recommendations. In these recommendations, it is specified that pilots should alternate passive and active vigilance phases.
Active vigilance periods are characterized by:
. tasks and verbal exchanges related to flight management,
. varied motor actions associated with mental tasks involving electronic interfaces (FMC, ECAM/EICAS for example),
. no meals during this period.
During the passive vigilance periods, we suggest favoring:
. activities not related to the flight (reading of papers for instance),
. more dispersed supervision of the flight,
. meals or snacks,
. napping.
It is proposed that pilots alternate these periods at a frequency between 20 to 40 minutes according to flight context. This alternation is mainly justified during calm cruise periods with no strategic changes in flight plan. Also, pilots are asked to verbally express the end of each phase in order to inform the other crewmember.
Results demonstrate that alertness decrement rates are lower for flights with recommendations, irrespective of the flight phase. Observing crews' activities shows that this reduction can be attributed to crew activity management conducive to reduced flight monotony.
6.4. CIRCADIAN RHYTHMS
6.4.1. CONSTANCY & RHYTHMICITY
6.4.1.1. DEFINITIONS
Human functioning has two main regulatory modes: circadian (circa: about, dies: day) and homeostasic (homeo: constant, stasis: level).
Vital functions pass through a maximum and a minimum during a period of 24 hours (circadian variation). These variations are within limits beyond which the organism would be in danger (homeostatic regulation).
6.4.1.2. MANIFESTATIONS
The homeostasic process manifests itself in individual life through sensations such as hunger, thirst, fatigue, drowsiness, etc. Satisfying these needs restores the internal balance needed to maintain physical and mental integrity.
Circadian regulation is reflected by a diurnal increase and a nocturnal decrease in the individual's functional capabilities. It is at the origin of sleep disorders, disturbances in the biological rhythms and mental performance when the rest-activity cycle is modified or after rapidly crossing many time zones.
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