Embraer EMB 120ER N121CZ accident near Greeley, Colorado

Probable cause

The bus driver's failure to maintain clearance from the standing airplane during dark night conditions. Contributing to the accident was the airport's lack of an escort for the bus.

NTSB analysis

The airplane, which was operating as a nonscheduled domestic passenger flight, was standing on a ramp during dark night conditions waiting for the flight's passengers to arrive by bus; the flight crew was onboard the airplane. The only airport employee on duty opened the gate, told the bus driver to drop the passengers next to the airplane, and then returned to previous duties. The bus driver reported that there was no lighting on the ramp when he drove the bus onto it. He added that he made a right turn around the back of the airplane and "didn't see the wing." At that point, he was unable to stop the bus before it hit the wing. Although the bus driver reported that there was no light on the back of the wing, a video of the ramp area showed that the vertical portion of the T-tail was illuminated and that the airplane position lights were illuminated.

The bus driver possessed current commercial passenger-carrying vehicle operational and medical certifications. The driver did not have vision problems. The driver stated that he was not using his cell phone at the time of the crash. A review of the driver's 72-hour activity history did not reveal any irregularities. The driver's postaccident toxicological testing results were negative for the tests performed. Given these facts, it is likely that the unescorted driver failed to maintain clearance from the airplane during the planeside delivery of passengers in dark night conditions. The lack of an airport employee to escort the bus to the side of the airplane likely contributed to the accident. After the accident, the operator stated that it would make a policy that drivers be guided to airplanes by a ground guide. If a ground guide was not available, the drivers would not be permitted to drop passengers planeside.

Text from the NTSB. Open the NTSB docket for CEN17LA350 for the full record.