THE HAZARD OF SPATIAL DISORIENTATION DURING HELICOPTER FLIGHT USING NIGHT-VISION DEVICES

Introduction: Night Vision Devices (NVDs) provide an enormous advantag e to the operational effectiveness of military helicopter flying by pe rmitting flight throughout the night. However, compared with daytime f light, many of the depth perception and orientational cues are severel y degraded. These degraded cues predispose aviators to spatial disorie ntation (SD), which is a serious drawback of these devices. Methods: A s part of an overall analysis of Army helicopter accidents to assess t he impact of SD on military flying, we scrutinized the class A-C misha p reports involving night-aided flight from 1987 to 1995. The accident s were classified according to the role of SD by three independent ass essors, with the SD group further analyzed to determine associated fac tors and possible countermeasures. Results:Almost 43% of all SD-relate d accidents in this series occurred during flight using NVDs, whereas only 13% of non-SD accidents involved NVDs. An examination of the SD a ccident rates per 100,000 flying hours revealed a significant differen ce between the rate for day flying and the rate for flight using NVDs (mean rate for daytime flight = 1.66, mean rate for NVD flight = 9.00, p < 0.001). The most important factors associated with these accident s were related to equipment limitations, distraction from the task, an d training or procedural inadequacies. Conclusions: SD remains an impo rtant source of attrition of Army aircraft. The more than fivefold inc rease in risk associated with NVD flight is of serious concern. The as sociated factors and suggested countermeasures should be urgently addr essed.