What happened
An aircraft had recently landed and was taxiing eastbound across the tarmac. Simultaneously, a tractor was traveling westbound while performing sweeping duties. The tractor was equipped with an amber strobe light on its roll bar and flashing hazard lights on its fender.
The driver of the tractor observed the aircraft exit a taxiway and move toward the tractor's path. According to the driver, the aircraft performed an 'S' turn that directed it straight toward him. In an attempt to avoid a collision, the driver maneuvered the tractor, but the vehicle struck the aircraft.
The pilot reported that after exiting the taxiway onto the tarmac, he performed a left turn to check his right side and then a right turn to check his left. Believing the tarmac was clear of traffic, the pilot straightened the aircraft and continued traveling east at a slow speed. The pilot stated he did not see the tractor or the sweeper and only became aware of the incident when he heard and felt the impact. A passenger in the aircraft also reported that visibility to the sides of the aircraft was limited and that they did not see the tractor.
The investigation
A police officer inspected the lights on the tractor and found the amber strobe light and flashing hazard lights were all in working order.