The US Marine Corps is reverting to conventional night-vision goggles on the upgraded Bell AH-1Z Viper and UH-1Y Venom after encountering problems with low-level night flying using the Thales Top Owl helmet’s visor-projected display.
The helmet is being modified to allow use of ANVIS 9 direct-view night-vision goggles for night-time flying and a monocular display for daytime use. This will allow the UH-1Y utility helicopter to meet its accelerated fleet introduction date of 2008, the USMC says.
Top Owl projects images from two night-vision sensors, mounted on the helmet, directly on to the visor, overlaying the binocular display on the pilot’s view of the outside world. During nap-of-the-earth flying, the USMC encountered an effect known as hyperstereopsis, a result of the sensors being set further apart than the pilot’s eyes and the projected image not quite matching the pilot’s view.
“At close range, the image appears distorted,” says the USMC. “The issue is with the way we use the helmet, and is at low level at night only, for nap-of-the-earth flying and confined-area landing.” The USMC says it plans to return to the visor-projected display at a later date.
GRAHAM WARWICK / WASHINGTON DC
Source: Flight International