Terrain and obstacle avoidance displays for low-level helicopter operations in degraded visual environments

Collision with obstacles (typically wires and towers) and with terrain during low level helicopter flight under low visibility conditions has been a documented problem for the US military. Degraded visual environments (DVE) due to night operations and/or poor weather prevent adequate visibility of terrain and obstacles ahead of the aircraft and contribute to many of the accidents. This paper documents the results of twelve pilots in a simulation evaluating four types of visual conformal symbology sets in a low-visibility condition contour terrain flight: a scene-linked condition, a conformal line condition, a guidance line condition, and the combination of the two in a conformal + guidance condition. The results of combined quantitative and qualitative analyses strongly support the superiority of the contour lines over the scene-linked to ensure the safest flying behavior and the greatest situation awareness. However, the interindividual variability was very high, suggesting that a modular and selectable presentation of the different displays should be made available, as a function of the phase of the flight, the nature of the mission and the pilot's preferences.