Incident Overview
A review of air traffic control tower tape transcripts confirmed that both pilots of the involved aircraft were given and acknowledged taxi clearances. However, neither pilot received traffic advisories regarding each other's taxi routes. The WLAC-1 was cleared to taxi westbound on Taxiway Charlie. The Aero Commander was also cleared to taxi on Taxiway Charlie and was entering the taxiway from the ramp area.
Collision Sequence
As the Aero Commander moved onto Taxiway Charlie, both aircraft converged and collided. Neither pilot reported seeing the other until immediately before the collision. The portion of Taxiway Charlie where the collision occurred had been redesignated as a ramp area in 1986.
Regulatory Context
According to the FAA Air Traffic Control Handbook 7110.65, non-movement areas, including ramps, are not under the control of the tower. The handbook further states that the responsibility for collision avoidance in non-movement areas rests with the pilot.
Investigation Findings
The investigation determined that both aircraft were operating with proper taxi clearances, but the absence of traffic advisories and the ambiguous status of the taxiway section contributed to the incident. The redesignation of that portion of Taxiway Charlie as a ramp area meant it was not subject to tower control, placing the onus on pilots to maintain situational awareness and avoid collisions.