Effect of alcohol on the threshold for detecting angular acceleration.

We investigated the effects of a low blood alcohol level (mean BAC = 0.037%) on subjects' ability to detect acceleration and deceleration of angular motion. The angular motion thresholds of six alcohol and six placebo subjects, all of whom had private pilot certificates, were tested under double-blind conditions in an enclosed simulator apparatus prior to drinking, after drinking, and at a time when the BAC's of alcohol subjects had reached zero. Mean threshold values for the three threshold determination sessions were 0.282, 0.376, and 0.343 degrees.s-2 respectively for the alcohol subjects, and 0.263, 0.262, and 0.262 degrees.s-2 for placebo subjects. A significant alcohol x test-session interaction (p < 0.005) reflected the elevated thresholds shown by all alcohol subjects after consuming alcohol (p < 0.001). Of the six alcohol subjects, four continued to have elevated thresholds after their BAC's reached zero (p < 0.001). Alcohol and placebo subjects showed similar performance on the ancillary tasks of maintaining altitude and reporting a specified number when it appeared on a digital display. Both groups also reported that they had experienced similar levels of discomfort symptoms before and after drinking. The results indicate that a pilot's ability to detect angular motion can be compromised by low BAC levels, and this effect may continue for some pilots after their BAC reaches zero.