During the entire investigation period activity data of each pilot were continuously recorded by means of an actimeter worn at their non-dominant wrist. A small hand held PC at pilot’s disposal allowed fast and efficient work in filling in questionnaires, handling the flight log and the daily sleep log. Completing a flight log, all relevant flight data of every duty day was documented (e.g. beginning and end of flight duty time; flight sectors; destinations, etc.).
Additionally during a duty cycle, pilots hourly ranked subjective fatigue and workload by standardized questionnaires (e.g. Karolinska Sleepiness Scale, Fatigue Scale of Samn and Perelli, NASA task load index).
Sleep – wake - cycles were documented by objectively recorded sleep-wake- data of the actimeter, as well as subjectively by daily filling in questionnaires of the sleep log before and after bedtime. The sleep log grasped specific aspects of sleep e.g. bedtime, time of awakening, number of awakenings, sleep period time, etc. The sleep log was also to be filled in before and after naps.
Besides of the sleep log, pilots also answered standardized questionnaires with respect to the subjective evaluation of fatigue, strain and recovery (e.g. subjective sleep quality; the degree of feeling refreshed). The participants’ objective performance was measured with the help of a computer-assisted single reaction task twice a day, after getting up in the morning and before going to bed in the evening. In addition, paper pencil questionnaires had to be answered at different time intervals scheduled before. These answers revealed information on relevant, psychosocial boundary circumstances, which had not been considered during the daily routines (e.g. job satisfaction, eating habits; relationship between crew members).