Counterweights Used with ANVIS.

Abstract : A survey was conducted at Fort Rucker, Alabama, on the use of counterweights with the aviator night vision imaging system (ANVIS). The purposes of the survey were to determine frequency and purpose of counterweight use, materials used, and actual weight of the counterweights. Thirty-seven night vision goggle (NVG) instructor pilots (IPs) and nineteen NVG student pilots contributed to this survey. NVG participants flew four different aircraft types located at three different airfields. The results showed that 76 percent of the NVG IPs used counterweights. Average weight for the counterweights was 13 oz with a minimum of 8.9 and a maximum of 22 oz. For the graduating NVG student pilots, 100 percent used counterweights. The average counterweight used by the students was 11.7 oz with a minimum of 3.4 and a maximum of 20.1 oz. The two primary reasons listed for using counterweights were to reduce the helmet from rotating forward and to relieve neck strain. The most common type of counterweight consisted of a standard issued cloth bag with two to three rolls of pennies. In the heaviest possible configuration, the head supported weight with ANVIS could be as much as 7.3 pounds lbs, which includes an X-Large SPH-4 helmet, 25-mm eyepiece ANVIS with dual battery pack and AA batteries, 20 oz of counterweight, a lip light, and an ANVIS head-up display (HUD). Of the 37 NVG IPs surveyed, the average estimated head supported weight with ANVIS was 5.7 lbs, with a minimum of 4.7 and a maximum of 6.8 lbs. With the addition of a protective mask the total weight would increase by approximately 2 pounds.