Visual field requirements for precision nap-of-the-earth helicopter flight

Abstract

Helicopter flight simulation visuals must display terrain for high altitude flights as well as flights within a few feet of the terrain. Currently high altitude visuals are well understood and supported, but extremely low altitude visuals are not. Terrain relief and texturing that appears convincing at high altitudes is drastically oversimplified at NOE altitudes, eliminating critical visual cues. Without adequate visual cues, simulated NOE flight is pointless, or worse, may induce negative training transfer. Too much visual complexity will overburden a real-time 3D graphics pipeline adversely affecting frame rate and usability. This thesis attempts to identify the minimal visual requirement for NOE helicopter simulation, thus enabling future simulator and trainer designers to make informed decisions regarding design criteria tradeoffs. Based on a task analysis of hovering over an unprepared landing site, critical cues were implemented in a fixed base helicopter flight simulator and tested on ten military helicopter pilots. Results indicate that a critical density of visually complex three-dimensional vegetation in combination with high-resolution terrain textures enabled experienced military helicopter pilots to accurately determine helicopter motion and make control corrections. Hover performance was degraded using lower vegetation densities and significantly degraded using just high-resolution textures.