Pilot performance with blood alcohol concentrations below 0.04%.

The effects of a low (less than 0.04%) BAC on pilot performance were investigated in a series of four experiments in which pilots flew a light aircraft simulator under alcohol and placebo conditions. The mean BACs of subjects when starting and finishing the test sessions were 0.037% and 0.028%, respectively. Two of the experiments involved demanding flight tasks under instrument meteorological conditions: complicated departure, holding, and approach procedures in one case; and VOR-use intersection problems in the other. The other two experiments involved ILS approaches under turbulence, cross wind, and simulated wind shear conditions that imposed heavy control-task loads on the pilots. Significant alcohol effects were found, but only under the heaviest workload conditions. During posttest interviews 75% of the pilots reported physical and/or mental effects due to alcohol.