Visual Approach Slope Indicator (VASI) System for Long-Bodied Aircraft

A comparative evaluation was conducted at the National Aviation Facilities Experimental Center (NAFEC), Atlantic City, New Jersey, on two methods of modifying the standard VASIS for use for long-bodied aircraft operations. Modification was required due to the greater pilot eye-to-wheel height of the larger aircraft which placed these aircraft in a potential undershoot situation when the on-course signals of standard VASIS were flown. Thirty-four subject pilots flying a variety of aircraft, including the B-747 and C-5A aircraft, participated in the program. The aircraft were tracked with phototheodolite equipment, and the pilots completed questionnaires at the conclusion of each flight. The Three-Bar System, a modification consisting of an additional component of the standard VASIS, was a significantly better aid than the White-Wing System, a modification incorporating the use of white lights only (pilots flew combinations of bright-dim lights) adjacent to the upwind bar of the standard VASIS.