The Bell AH1-J and the Agusta A-129 had a similar device in that it measured the direction of the airflow around the helicopter as well as the airspeed. It would align itself with the relative wind in relation to the center of the fuselage. In a hover it would align itself with the downflow measuring air velocity. Like the Apache system it was used to correct for wind for the gun and the missiles.. .. .Unlike the Apache system and that used on the HH-65, which were mounted on top of the rotor system this unit was mounted on the right side of the fuselage immediately next to the pilot position.